River Adur Catchment Flood Management Plan Appendices · Environment Agency River Adur CFMP –...

Environment Agency River Adur CFMP Draft Plan - Appendix B (March 2007)

River Adur

Catchment Flood Management Plan

Appendices

Environment Agency River Adur CFMP (September 2008) i

Contents Contents ........................................................................................................................................................i

Appendix A: Responsibilities for Flood Risk Management and Associated Activities................................. 1

Appendix B: Environmental Report and Policy Appraisal Tables................................................................ 3

Environment Agency River Adur CFMP - Appendix A (September 2008) 1

Appendix A: Responsibilities for Flood Risk Management and Associated Activities

The Department for the Environment, Food and Rural Affairs (Defra) has overall responsibility for flood risk management in England. Their aim is to reduce flood risk by:

• Discouraging inappropriate development in areas at risk from flooding.

• Encourage the provision of adequate and cost effective flood warning systems.

• Encourage the provision of adequate technically, environmentally and economically sound and sustainable flood defence measures.

The Government’s Foresight Programme has recently produced a report called Future Flooding, which warns that the risk of flooding will increase between 2 and 20 fold over the next 75 years. The report produced by the Office of Science and Technology has a long-term vision for the future (2030 – 2100), helping to ensure effective strategies are developed now. Sir David King, the Chief Scientific Advisor to the Government (2000 to 2007) concluded: “continuing with existing policies is not an option – in virtually every scenario considered (for climate change), the risks grow to unacceptable levels. Secondly, the risk needs to be tackled across a broad front. However, this is unlikely to be sufficient in itself. Hard choices need to be taken – we must either invest in more sustainable approaches to flood and coastal management or learn to live with increasing flooding”. In response to this, Defra is leading the development of a new strategy for flood and coastal erosion for the next 20 years. This programme, called “Making Space for Water” will help define and set the agenda for the Government’s future strategic approach to flood risk. Within this strategy there will be a holistic approach to the assessment of options through a strong and continuing commitment to CFMPs and SMPs within a broader planning matrix, which will include River Basin Management Plans prepared under the Water Framework Directive and Integrated Coastal Zone Management. We take the lead role in preparing Catchment Flood Management Plans (CFMPs). We recognise that all key organisations and decision makers must work together to plan and take action to reduce flood risk. Consultation with other authorities, organisations and groups has been carried out in order that the plan can be adopted as a way forward for flood risk management in the catchment. The development of the CFMP has been supported by a Steering Group with representatives from the following organisations:

• Adur District Council

• Arun District Council

• Brighton and Hove County Council

• Defra

• Natural England

• Environment Agency

• Horsham District Council

• Mid Sussex District Council

• Southern Water

• West Sussex County Council Consultation has also taken place with a number of other organisations including the National Farmers Union, RSPB, Sussex Downs Conservation Board, High Weald AONB, National Trust, Sussex Wildlife Trust, Highways Agency and members of the public.

Environment Agency River Adur CFMP - Appendix A (September 2008) 2

The Environment Agency’s role in flood risk management Since its formation in 1996, the Environment Agency has taken a lead role in flood risk management within England and Wales. Within this CFMP area, we also perform the role of Internal Drainage Board (IDB) with responsibility for land drainage issues. We provide information on flood likelihood on the internet Flood Map. The map shows areas that would be affected by flooding from the rivers or the sea without defences. The flood extent shown on the Flood Map refers to Flood Zone 2 and Flood Zone 3 as defined in PPS25. A Flood Risk Assessment is required by Local Planning Authorities when a planning application is made within Flood Zones 2 and 3. We are a statutory consultee on development plans and other aspects of development control within the land use planning system. The department of the Communities and Local Government has issued guidance in relation to flood risk and planning (PPS25), which stipulates a “risk based sequential search” for assessing development within the catchment. This guides the approach of planning authorities to land use allocation, and has a significant impact on development at both local and regional scale. It is therefore essential that the CFMP is compatible as well as supportive of this process. It should be noted that the CFMP does not replace a strategic flood risk assessment, which is a more detailed assessment of flood risk in relation to development and planning. We are also responsible for flood warning. We provide an online Flood Warning Service for designated Flood Warning Areas in England and Wales that is automatically updated every 15 minutes. Flood warning makes an important contribution to reducing the impact of flooding and can be particularly effective where confidence in the prediction of rising river levels is high, allowing sufficient time for an effective response both by the public and emergency services. We work with Sussex Police, West Sussex Fire Brigade, Sussex Ambulance Service, West Sussex County Council, district councils, the Maritime and Coastguard Agency, and local community groups to co-ordinate responses to fluvial and coastal flooding. Our flood defence work aims to protect people and property and improve the environment. The Environment Act 1995 and the Water Resources Act 1991 give the Environment Agency certain powers to carry out works on ‘main’ river watercourses for flood defence purposes. These powers are permissive and allow us to determine how and where work is carried out according to priority and available resources.

Environment Agency River Adur CFMP – Appendix B (September 2008) 3

Appendix B: Environmental Report

and Policy Appraisal Tables

Contents Non-Technical Summary B1 Introduction and Background B1.1 The purpose of SEA B1.2 The Catchment Flood Management Plan B1.3 Structure of the report appendix B2 Consultation B3 Environmental Context B3.1 Policy, plan and programme review B3.2 Baseline review B3.3 Scope of the SEA and environmental objectives B4 Assessment and evaluation of environmental effects B4.1 Strategic options and appraisal process B4.2 Assessment and evaluation of impacts B4.3 Cumulative environmental effects B4.4 Mitigation and enhancement B4.5 Monitoring requirements References List of Figures Figure B1 Preferred Policy Options for the Adur CFMP Figure B2 The location of the Adur Catchment Flood Management Plan. Figure B3 How the CFMP fits with the wider planning framework

List of Tables Table B1 Summary of consultation undertaken during the development of the CFMP Table B2 Review of policies, plans, and programmes and relevance to the CFMP Table B3 Scope of the SEA in relation to the CFMP Table B4 Definition of policy options Table B5 Summary of cumulative issues List of Forms (Appraisal tables in Section B4.2) Form B.1 Purpose of the CFMP Form B.2 Meeting Legal Requirements Form B.3a Summary of Flood Risks Form B.3b Source-pathway-receptor table Form B.4 CFMP Policy Options Form B.5 Summary of current and future level and response to flood risk Form B.6 Appraisal of Policy Options against Policy Option Objectives Form B.7 Summary of the Losses and Gains Form B.8 Summary of the Preferred Policy Form B.9 Requirements for further policy development and appraisal Form B.10 Indicators for Monitoring, Review and Evaluation Form B.11 Signature of CFMP Project Manager


Non-Technical Summary We are developing the Adur Catchment Flood Management Plan (CFMP) in order to establish long-term (50 - 100 years) policies for sustainable flood risk management. Our policies are at the highest level in our hierarchy of spatial flood risk management plans and are about setting the right strategic direction so that in the future we take the best and most sustainable approach to managing flood risk to people, the environment and the economy. These policies will not set specific measures to reduce flood risk or establish how to manage flooding issues in a catchment. Although not a legal requirement, we are undertaking strategic environmental assessment (SEA) as part of our planning process in order to demonstrate how our plan takes account of the environment and, in particular, the likely significant environmental effects of the CFMP. The CFMP involves:

•••• working with key partners and decision makers to establish long-term policies for sustainable flood risk management;

• carrying out a strategic assessment of current and future flood risk from all sources (such as rivers, sewers, groundwater and the sea) within the catchment, understanding both the likelihood and consequence of flooding and the effect of current ways of reducing risk. We measure the scale of risk in social, environmental and economic terms;

• considering how the catchment works, and looking at other policies, plans and programmes to identify opportunities and constraints to achieving sustainable flood risk management;

• finding ways to work with nature, and manage flood risk to maintain, restore or improve natural and historic assets.

In undertaking the SEA we considered the baseline environment, and how this would evolve without the influence of our plan. People and communities At the household and community level, flooding can cause personal distress, poor health and damage to property and possessions as well as pose a threat to life. There are currently approximately 150 residential properties and approximately 400 people at risk across the catchment under a 1% annual probability flood outline. The majority of these properties are located in the Lower Adur and Ferring Rife, including Steyning, Upper Beeding, Bramber, Shoreham and Ferring, where flooding also occurs from surface water, groundwater and sewer systems. The Lower Adur is also the catchment most sensitive to future change. In total, it is predicted that the number of properties and people at risk from a 1% annual probability flood event will rise to approximately 2,400 and 5,800 respectively in 50-100 years time. The majority of these increases are attributed to significant increases in risk in Shoreham. Property and infrastructure The Annual Average Damages (AAD) to property and agricultural land currently total approximately £5 million under a 1% annual probability flood outline and £0.3 million for more frequent flooding (10% annual probability). The majority of these damages are sustained in the Lower Adur and Ferring Rife catchments due to the large number of residential and commercial properties at risk in the towns of Steyning, Upper Beeding, Bramber, Ferring and Worthing. The low damage values in the Adur West Branch sub-catchment result from the rural and sparsely populated nature of the area. The damages in this area constitute the highest agricultural costs in the catchment. There are also currently 1 sewage treatment works and approximately 2km of main road under threat in the 1% annual probability flood outline and approximately 1.4km


under the 10% annual probability flood outline. In 50-100 years, total AAD to properties and agricultural land are predicted to have increased to approximately £15 million, the length of main road affected to have increased to approximately 10km and a number of emergency services and hospitals become exposed to flood risk (1% annual probability). Properties and major transport routes in Brighton and Hove have flooded from groundwater and surface water in the past. The most recent widespread flooding in Brighton and Hove was during 2000. There are also likely to be a number of properties at risk from the Teville Stream, however current information on this watercourse is limited. The environment In terms of the environment, there are currently approximately 5km2 of proposed National Park, approximately 1.5km2 of Environmentally Sensitive Area (ESA) and approximately 1.5km2 of Area of Outstanding Natural Beauty (AONB) at risk from a 1% annual probability flood outline. There are also 0.6km2 of Adur Estuary Site of Special Scientific Interest (SSSI), 3.5km2 of Sites of Nature Conservation Importance (SNCI) including the River Adur Water Meadows, Wyckham Wood and Ferring Rife and Meadows (1% annual probability). In 50-100 years, these areas are not expected to have expanded significantly. There is a degree of tourism and recreation value associated with these sites. There are also issues of soil erosion and surface water run-off that cause a significant problem to the environment and in terms of depositing ‘muddy’ flooding to properties in Worthing and Brighton and Hove which are downstream of the South Downs. There are also water quality issues associated with this which have the potential to cause problems within designated sites. There is significant potential within this catchment to restore geomorphological processes to reduce these problems as well as flood risk in general. Our understanding of the likely future of the catchment is based upon various scenarios from our broad-scale modelling, where estimated changes to the climate, development and land management could result in changes to flood risk. We used these scenarios to understand what six generic policy options could mean for flood risk to people, the environment and the economy. The options we considered were:

1. No active intervention (including flood warning and maintenance). Continue to monitor and advise 2. Reduce existing flood risk management actions (accepting that flood risk will increase over time) 3. Continue with existing or alternative actions to manage flood risk at the current level (accepting

that flood risk will increase over time from this baseline) 4. Take further action to sustain current scale of flood risk into the future (responding to the potential

increases in flood risk from urban development, land use change, and Climate Change). 5. Take further action to reduce flood risk (now and/or in the future) 6. Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, (which

may constitute an overall flood risk reduction, for example for habitat inundation).

With our Steering Group we established a series of social, environmental and economic objectives for the catchment that drew from other policies, plans and programmes. Economic

• Ensure that river channel and flood defence maintenance expenditure is appropriate to the economic damage of flooding.

• Ensure flood damages do not significantly increase in the future (for example due to climate change).

Social

• Ensure the impact of flooding on people and properties does not significantly increase in the future (for example due to climate change).

• Ensure the disruption caused by flooding to transport and critical infrastructure does not significantly increase in the future (for example due to climate change).

• Reduce the impact of muddy flooding.


Environmental • Protect and enhance nationally and internationally important species and habitats. • Restore rivers and floodplains to a naturally functioning state where feasible.

These objectives establish the key aims of the CFMP. We also consulted with the public on our draft objectives, and it was against these that we appraised the alternative policy options, drawing from opportunities and constraints provided from other policies, plans and programme. The most important opportunities and constraints to our CFMP are as follows: Opportunities:

• Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities.

• Help meet national biodiversity action plan (BAP) targets. • Work with the High Weald AONB Joint Advisory Committee to achieve the targets

set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character.

• Move toward more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character.

• Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

• Influence the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area.

• Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham and Burgess Hill).

• Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham and Burgess Hill.

• Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream.

• Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding.

• Develop a flood warning system for groundwater flooding. • Continued practice and development of the Emergency Response Plan in Brighton

and Hove, Worthing, Shoreham, and Burgess Hill. • Reduce surface water run-off and soil erosion by supporting the existing and future

management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council).

• Support the existing flood defence measures in relation to surface water flooding, such as bunds provided by Brighton and Hove City Council.

• Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill.

• Improvements in the efficiency of channel and flood defence maintenance processes.

• Effective and efficient use of developer contributions for flood risk management. • To work with Defra/ farmers to produce soil management plans which have a benefit

to flood risk through reducing the run-off rate.

Constraints: • Government and international legislation, environmental management policies,

plans and strategies for the catchment must be complied with, such as


accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.

• Existing urban development may prevent reinstatement of natural river processes. • Individual homes and properties are currently at risk of flooding. • Transport links in the catchment are a vital part of the communication network

regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032.

• Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance.

• Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions.

• Presence of protected species with specific water level, water quality and habitat requirements, for example in the Adur Estuary SSSI.

• Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences).

• No degradation of existing fish passage and habitat. • Visual impact of flood risk management activities within the proposed National Park

or Areas of Outstanding Natural Beauty. • Steep catchments of the South Downs result in rapid run-off and quick responses to

rainfall events. • A suitable level of productivity from agricultural land needs to be retained. • Changes to flood risk management can affect the landscape, its character and value

as an amenity. • CFMP objectives and policies must complement those of the Shoreline

Management Plan (SMP) that affects the CFMP area. • Available funding for the initial set up of new flood risk management schemes. • Older flood defence structures are likely to be costly to maintain. • Limited available information on surface water and groundwater flood damages.

Having established the catchment objectives, and identified the opportunities and constraints for the CFMP, all the relevant information gained about the catchment was brought together in order to divide the CFMP area into similar areas, using the following criteria:

• Current level of flood risk; • Hydraulic characteristics and flood mechanisms; • Topography, geology and drainage characteristics; • Land use land use and drivers for change; • Links to other plans; and, • Opportunities for future flood risk management.

From this, the River Adur catchment was divided into 9 separate policy units. Each policy unit was then assessed to decide which policy would provide the most appropriate level and direction of flood risk management for both now and the future. One of six standard flood risk management policies, listed on page 4, has been applied to each policy unit. These policies have been agreed nationally and are being applied to CFMPs in a standard way across England and Wales. Our preferred policies are as follows:


Figure B1 Preferred Policy Options for the Adur CFMP

The significant impacts likely to result from implementing the CFMP policies are as follows:

• Annual Average Damages (AAD) caused by flooding are unlikely to increase significantly in the future, particularly in the urban areas of Shoreham, Burgess Hill and Hassocks, where flood defences are set to be improved in order to prevent increased flood risk due to climate change. The combination of flood attenuation in the Adur catchment and South Downs with maintained flood defences in Worthing, Brighton, Hove, Steyning and Upper Beeding will also prevent a significant increase in flood damages.

• The balance of flood risk management (FRM) to AAD will be efficient across the catchment.

• The impact of flooding on people and properties will be prevented from significant increases across the catchment.

• The level of disruption to critical infrastructure and transport routes will not increase in the future.

• Rivers and floodplains will be restored to a more natural state throughout the Adur catchment and Upper Adur. This will also result in increased wetland habitat areas.


• The CFMP is likely to have a positive impact on the biodiversity of the catchment, especially those habitats and species dependant upon the water environment. These areas will be protected and also extended and enhanced.

• Sustainable land management practices are likely to increase in uptake and efficacy resulting in reductions in water run-off rates and soil erosion. This in turn will reduce the likelihood of muddy flooding in urban areas downstream of the South Downs.

These preferred policies have been selected because alternative options would have resulted in a less sustainable and coordinated approach to flood risk management or unnecessary environmental impacts on a catchment level. These policy options have been chosen within the limits of the aforementioned constraints whilst maximising the potential to alleviate flood risk and benefit the environment. The strategy of this CFMP is to increase water retention and storage capacity in the sparsely populated upper catchment and River Adur channel and floodplain while increasing defences around high-risk urban areas, particularly Burgess Hill, Hassocks and Shoreham which will benefit from increased defences in line with future change in flood risk due to climate change and sea level rise. The towns of Steyning, Upper Beeding, Brighton, Hove and Worthing will also benefit from the combined effects of maintaining current FRM and attenuating flood risk upstream. In particular appropriate land management practices on the South Downs have potential to reduce muddy flooding in both Worthing and Brighton and Hove. This strategy will help to achieve the key objectives of the CFMP by ensuring the number of people and properties at risk from flooding will not increase significantly in the future. This will also ensure the disruption caused by flooding of critical infrastructure and transport routes does not increase. AAD incurred through flooding to properties and agricultural land will in turn be prevented from significant increases in the future and may even be reduced in parts of the catchment. Studies will be completed where understanding of current and future flood risk from rivers, groundwater, surface water and urban drainage is less developed, such for the Teville Stream and Brighton and Hove. This will enable better informed decision making. Returning the River Adur and its floodplain to a more natural state will have significant environmental benefits. Habitats and species will be protected and designated sites enhanced in accordance with UK and local BAP targets and water-dependent SSSIs will be improved towards the Public Service Agreement to bring 95% of SSSI land into ‘favourable’ condition by 2010. SNCIs will also benefit from increased frequency of flooding in managed and predictable way. With careful management, these improvements may lead to increased amenity and recreation value throughout the CFMP area. These important benefits will not be maximised unless the naturalisation of the River Adur is carried out in a managed and predicable way. A ‘do nothing’ approach may result in damage to sensitive environmental sites. Increasing water retention and storage capacity in both the Adur catchment and South Downs will serve to alleviate flows and the frequency, depth and extent of flooding further downstream in high-risk urban areas. This process will also have to be managed to protect and enhance wherever possible habitat and species diversity and landscape character. This CFMP also supports the uptake of environmentally beneficial land management practices which will form part of an integrated FRM strategy and greatly reduce run-off rates and soil erosion in the agricultural areas of catchment. These schemes will also lead to shifts in land use practices that will enhance biodiversity. By taking a proactive approach in all parts of the catchment, this CFMP will support the implementation of sustainable planning policies and feed into ongoing planning processes and document revisions. This will lead to the development of a more integrated and environmentally, socially and economically sustainable flood risk management strategy.


Our mitigation and enhancement measures are included within the appraisal of alternative policy options; and will be cascaded down through our subsequent and more detailed plans as we decide the flood risk management measures we need to implement the policies. The monitoring of the significant effects of the plan will include (in no particular order):

a) Change in AAD to properties (£); b) Change in AAD to agricultural land (£); c) Change in estimated damages resulting from surface water flooding (£) d) Change in number of people affected by 1% annual probability flood outline; e) Change in estimated number of properties affected by surface water and/or

groundwater flooding; f) Change in the estimated number of properties affected by downland ‘muddy’ surface

water flooding; g) Change in length of main roads affected by 1% annual probability flood outline (km); h) Change in number of critical infrastructure sites affected by the 1% annual probability

fluvial flood event; i) Change in the number and period of recorded A road and railway closures due to

surface water flooding; j) Change in the number if critical infrastructure sites recorded as being affected by

surface water flooding; k) Change in balance of annual river channel and flood defence maintenance (£) to

annual average damages from fluvial flooding to agriculture (£); l) Change in area of naturally active floodplain restored (km2); m) Change in length of naturally functioning river (km); n) Achievement of BAP targets and improved habitat quality and species diversity; and o) Change in landscape character assessment of the AONB, ESA and/or proposed

National Park. These indicators are monitored by various agencies best placed to do so as part of their internal targets monitoring. This information is largely collected in a standardised way on a relatively regular basis. These indicators are therefore practical and feasible measures to monitor the progress of the CFMP over the following years. In doing so, unforeseen adverse effects on the environment and/or communities within the catchment will be identified and the necessary remedial actions taken. The Environment Agency will look to work with local authorities to monitor indicators a) to k). The Environment Agency is likely to be best placed to monitor indicators l) to o) as lead partners in Local Biodiversity Partnerships, or as participants in monitoring systems such as the English Nature Site Information Service (ENSIS) and the Biodiversity Action Reporting System (BARS), both maintained by Natural England. Natural England will also be a useful resource for most of the environmental information needed to effectively monitor this CFMP.


B1 Introduction and Background

B1.1 The purpose of SEA

This appendix documents the strategic environmental assessment (SEA) process undertaken for the Adur Catchment Flood Management Plan (CFMP). Strategic environmental assessment is a systematic process for anticipating and evaluating the environmental consequences of plans and programmes prior to decisions being made. The purpose of SEA is to provide for a high level of protection of the environment and to contribute to the integration of environmental considerations into the preparation and adoption of plans and programmes with a view to promoting sustainable development. There is no legal requirement for us to undertake SEA for CFMPs because they are not required by legislation, regulation or administrative provision. However they clearly help set the framework for future planning decision, and have the potential to result in significant environmental effects. As a result Defra guidance (Defra, September 20041) and our own internal policy have identified a need to undertake a SEA approach. In developing our CFMP, we consider the environment alongside social and economic issues. This appendix demonstrates how we have gone about undertaking the SEA for our CFMP. The contents of this Environmental Report have been broadened to include the social and economic effects also considered in our plan making process.

1 http://www.defra.gov.uk/environ/fcd/policy/sea.htm


B1.2 The Catchment Flood Management Plan

Figure B2 shows the location of the Adur CFMP with the various policy units identified.

Figure B2 Location of Adur Catchment Flood Management Plan

CFMPs are planning documents that we are preparing for all surface water river catchments across England and Wales. In developing the CFMPs, we are working with other key decision-makers to help us to establish policies to manage flood risk for the next 50-100 years. We know we cannot reduce flood risk everywhere, so we need to target efforts to where they are needed most: this is the purpose of our CFMP. They will not set specific measures to reduce flood risk or establish how to manage flooding issues in a catchment. Our policies are at the highest level in our hierarchy of spatial flood risk management plans and are about setting the right strategic direction so that we take the best and most sustainable approach in the future. To do this, we need to understand the extent, nature and scale of current and future flood risk to people, the environment and the economy across the whole catchment before choosing certain policies.


We need to decide at this stage where to take further action to reduce or sustain flood risk, where we need to change the way we currently manage flood risk, or where we need to take little or no action. The main body of the CFMP report provides a more detailed introduction to the CFMP, including the contents, aims and objectives of the plan: see Section 1.1 (Background) and Section 1.2 (Aims and Scope). The CFMP involves:

• carrying out a strategic assessment of current and future flood risk from all sources (such as rivers, sewers, groundwater and the sea) within the catchment, understanding both the likelihood and consequence of flooding and the effect of current ways of reducing risk. We measure the scale of risk in social, environmental and economic terms;

• identifying opportunities and constraints within the catchment to reduce flood risk through changes in land use, land management practices and/or the flood defence infrastructure;

• finding ways to work with nature, and manage flood risk to maintain, restore or improve natural and historic assets;

• working out priorities for studies or projects to manage flood risk within the catchment, and identifying responsibilities for the Environment Agency, other operating authorities, local authorities, water companies or other key interested groups.

B1.3 Structure of the report appendix

This appendix documents the SEA process we have undertaken throughout our CFMP planning process and covers:

• B2 – Consultation: setting out information on how we have engaged interested parties, including the SEA consultation bodies, through CFMP development and the SEA process.

• B3 – Environmental Context: The relationship between the CFMP and relevant plans and programmes; a summary of the relevant environmental baseline in the catchment. It also sets out the environmental issues scoped into the SEA process and the environmental objectives used to carry out the assessment in Section B4.

• B4 – Assessment and Evaluation of Environmental Effects: Setting out the environmental effects of the different options available to the CFMP, cumulative effects of the CFMP as a whole and with other relevant plans in the catchment. It also sets out how mitigation and enhancement are considered at this strategic scale and the future monitoring requirements.

Note: hyperlinks have been provided to the main report to allow the reader to appreciate the broader context of our plan-making process.


B2 Consultation Section 1.5 Involving others in the main CFMP report provides information about the consultation undertaken to date. This information is repeated below. The aim of consultation during the CFMP process is to obtain feedback and build consensus with the Consultation Group on issues identified during the catchment understanding process, and the proposed adoption of certain policies in certain areas of the catchment. Consultation includes statutory and non-statutory consultation bodies and is integral to the process at every stage in addition to defined periods. Developing a CFMP takes a considerable amount of time, and allows for public consultation so that people can be informed of the process and what is being achieved. It enables comments and suggestions on the plan to be received. Table B1 below, shows how we gathered information and consulted and worked with important groups and organisations for this CFMP. The draft CFMP report and the previous inception and scoping reports are available on our website2. This report is at the draft main stage and will be updated after this consultation period. Now is the opportunity for you to give your feedback and input on all parts of the report before it is finalised. The Consultation Group for this CFMP has included a wide range of statutory, non-statutory, environmental and socio-economic interest groups as well as members of the general public. These groups have participated at each key stage of the CFMP to date and their opinions and suggestions have been incorporated throughout, wherever feasible and appropriate. The Steering Group is a wider group brought together to guide the technical delivery of a CFMP, to focus the data collection, and to sign off the various reports produced prior to their publication. The Steering Group is comprised of key Environment Agency staff and staff from other major stakeholders including:

• Adur District Council;

• Arun District Council;

• Brighton and Hove City Council;

• Defra;

• Environment Agency;

• Horsham District Council;

• Mid Sussex District Council;

• Natural England;

• Southern Water;

• West Sussex County Council; and,

• Worthing Borough Council. Key stakeholders in the catchment comprise statutory and non-statutory agencies and groups as well as members of the public. Those who were consulted during the CFMP process include, but are not limited to, the following:

• Campaign to Protect Rural England;

• Country Land And Business Association;

• Natural England;

2 http://environment.gov.uk/regions/southern/290158/954666/995532/1493581/?version=1&lang=_e


• English Heritage;

• Farming and Wildlife Advisory Group;

• Forestry Commission;

• Highways Agency;

• National Farmers Union;

• National Trust;

• Network Rail;

• Parish Councils (various);

• Ramblers Association;

• Royal Society for the Protection of Birds;

• South Downs Joint Committee;

• Sussex Otters and Rivers Partnership; and,

• Sussex Wildlife Trust. Table B1 Summary of consultation undertaken during the development of the CFMP

CFMP timetable

CFMP stage When Actions Achievements

Inception Stage January 2004 All Sussex CFMP Reports delivered.

Inception reports issued according to CFMP rolling programme.

October 2005 Scoping stage started.

January 2006 Scoping workshop held.

Further development of catchment understanding and review of hydraulic model output.

Scoping Stage

April 2006 to June 2006

Scoping Report public consultation period. Report available on Environment Agency website, main libraries and advertised in local newspapers.

Comments on all aspects of the Scoping Report received.

July 2006 Draft main stage started.

September 2006

Steering Group meeting held.

Review of policy unit boundaries and application of flood risk management policies.

June 2007 to September 2007

Public consultation period. Draft CFMP available on Environment Agency website, main libraries and advertised in local newspapers.

Comments on all aspects of the draft CFMP, notably:

Policy choice

Action plan.

November 2007

Steering Group meeting. Review of consultation responses and finalise CFMP.

Main Stage

September 2008

Final CFMP published.

Available on the Environment Agency’s website with hard copies in selected libraries and local authority offices.

Scoping Report consultation summary Responses were received by Mid Sussex District Council and West Sussex County Council. Below is a summary of the main environmental, social and economic issues that have been highlighted during the Scoping Stage consultation period and throughout the CFMP process which have been incorporated into the CFMP where feasible and appropriate:


• Concern over how an integrated drainage strategy will be implemented, and by who (Mid Sussex District Council);

• Expressed need for appreciation of careful management requirements where areas of the catchment have been identified for Policy 6 (West Sussex County Council);

• Queries as to how the CFMP will promote agri-environment schemes (West Sussex County Council); and,

• The consequences associated with an increased frequency of flooding in the Adur Valley in terms of increased tidal vulnerability should be assessed in greater detail (West Sussex County Council).

Draft CFMP Report consultation summary During the three-month consultation period, formal responses were received from Mid Sussex District Council, Henfield Parish Council, West Sussex County Council, Brighton and Hove City Council and Burgess Hill Town Council. The majority of the comments either requested clarification, revisions or greater detail, or offered further information about flood risk and management in their areas. These points were considered and the report amended as appropriate. West Sussex County Council appreciated the recognition that FRM is a major contributor to sustainable development and supported the implementation of policy option 6 across stretches of the Adur, whilst cautioning the need for careful management. The Council also recognises that it is important that the CFMP support landowners and farmers wishing to enter agri-environment schemes but is concerned the CFMP does not address how this will be achieved and that Natural England should be involved with this. As Natural England is a statutory consultee and member of the Steering Group for this CFMP, the organisation is involved throughout the development of the CFMP. There is a good framework in place to extend this involvement in to the implementation phase of the CFMP. Similarly, the Council highlight the work of the Sussex Water Partnership and its potential role in implementing sustainable water management. The Environment Agency will endeavour to work with appropriate stakeholders to implement the CFMP. The Council also commented on the need to identify appropriate locations and mechanisms for implementation of wetland recreation and expansion. The Council also highlighted the potentially positive effects of flooding on sites of historical interest, namely Bramber and Knepp Castles. Henfield Parish Council reiterated the view that current floodplains must be properly maintained to reduce the risk of flooding in the future. There is indeed large scope for river and floodplain restoration within this catchment and this is integral to the strategy of this CFMP in minimising flood risk. Burgess Hill Town Council welcomed the policies and action plan set out for the policy unit of Burgess Hill and Hassocks and also encouraged a system that would allow documents produced by different stakeholders to be reviewed regularly to ensure that the impact of any changes in one document is taken into account in the strategies of others. This is an approach that is very much welcomed and encouraged by the CFMP. Every effort has been made to identify the synergies, opportunities and constraints between plans, policies and programmes as reviewed in Tables B2 and B5 below.


B3 Environmental context

B3.1 Policy, plan and programme review The SEA considers the relationship between the CFMP and other relevant plans and programmes. A review was undertaken at the scoping stage and updated during the main stage assessment, in order to:

• help collate additional environmental baseline information for developing the CFMP;

• identify environmental issues relevant to the SEA (e.g. existing environmental problems / protection objectives);

• identify influences of the CFMP on existing plans and programmes and vice versa;

• understand these relationships to help evaluate the significance of environmental effects;

• help identify any further assessment required. A diagram setting out our view of the relationship between CFMPs and other key policies, plans and programmes is illustrated in Figure B2. Section 1.4 Links with other plans discusses the relationship with other plans. Those plans that we have drawn into the development of the CFMP are listed in Table B3. Figure B3 How the CFMP fits with the wider planning framework


Table B2 Review of policies, plans, and programmes and relevance to the CFMP Relevant plan, policy or programme Potential influence Relevant opportunities or constraints we need

the CFMP to consider

Land-Use Planning (Regional and Local Government)

Regional Spatial Strategy for South East (March 2006)

Water utility efficiency (now and in the future) will influence water resources, aim to stabilise and reduce footprint. Exposure to flood risk (now/future) to developments depending on housing allocations, new and improved strategic infrastructure, tree cover/open spaces.

Reducing risk to critical infrastructure, material assets, people and property. Improving water resource efficiency and quality. Extent of tree cover and green open spaces now and in the future and the impact of this on run off, storage and flow patterns.

Brighton and Hove Local Plan 2001 Managing risks to reduce the threat to people and their property Enforcing adequate protection measures for essential water resources. Influence on new developments in areas at risk from flooding. Aiding planning and development in the Coastal Zone.

Potential to aid future developments to meet sufficient environmental requirements CFMP should ensure sufficient infrastructure is in place including land drainage, coastal defence and flood-prevention structures prior to development.

Adur District Plan 1996 Protection of existing water resources and sustainable water management. Development in areas exposed to flood risk. Protection of all designated and other areas of national and local nature conservation importance.

Opportunity to strictly control development in the countryside in undeveloped areas between Worthing and Lancing/Sompting and Shoreham-by-Sea. Potential to restrict development encroaching on the South Downs. Potential to influence planning permission in flood risk areas. Protection of integrity of coastal and flood defences. Protection of SSSIs – the Adur Estuary at Shoreham-by-Sea and Cissbury Ring and Local Nature Reserves at Lancing Ring in Adur District and Mill Hill in Shoreham-by-Sea.

Horsham District Local Plan 1997 Development in areas exposed to flood risk (now/future). Protection of AONB and SSSIs.

Protection and continued conservation of Sussex Downs and High Weald AONBs. Restrictions on planning permission in areas associated with flood risk.

Worthing Local Plan 2003 Enhancing and protecting local nature sites. Future Development. Water resource management.

Accommodating proposed development at Durrington and East Worthing. Opportunity to aid the implementation of the coastal


Relevant plan, policy or programme Potential influence Relevant opportunities or constraints we need the CFMP to consider

Development in the coastal zone. Coastal and tidal flooding defences.

defence strategy.

Mid Sussex Local Plan 2004 Strong protection of AONBs from development-defining ‘built-up’ boundaries. Preservation of buildings of architectural or historic interest and their settings, archaeological sites and their settings, and preservation and enhancement of special character and appearance of conservation.

Accommodating future development around Haywards Heath and Burgess Hill. Reducing risk to assets and character of settlements such as Haywards Heath. Potential to develop better land use planning in the future taking into account water resources, use and extraction.

Flood Risk Management Planning

Beachy Head to Selsey Bill Shoreline Management Plan (First Review)

Policy framework addressing flood risk to people and the historic and natural environment located at the coastline. Management of coastal defences Protection of biodiversity.

CFMP objectives must complement those of the SMP. Maintenance and upgrade of existing shoreline and coastal defences at Shoreham Harbour Maintenance of existing river walls and embankments on the mouth of the River Adur and upgrading them as sea levels rise. CFMP must complement ‘hold the line policy’ along relevant coastline to maintain protection from coastal erosion and flooding.

Other Water Management Planning

Adur and Ouse Catchment Abstraction Management Plan (March 2005)

Sustainable management of water resources in the catchment including water allocation and abstraction licensing.

Addressing quality concerns associated with the large Goddards Green waste water treatment works discharges to the Eastern branch of the River Adur. Improving water resource efficiency and abstraction issues.

River Basin Management Plans Plans to achieve Water Framework Directive targets for 2015. River Basin characteristics, review of impact of human activity on status of water bodies and an economic analysis of water use.

Maintenance of water quality status of water bodies in the CFMP area and opportunities for improving towards Water Framework Directive targets. Impact of improving water quality on flow, erosion, sedimentation and water body capacity. Opportunities for protecting and enhancing biodiversity, UK and local BAP priority species and habitats and designated fisheries.

Directing the Flow – Priorities for future water Future water policy to respect environmental limits, Potential opportunities for identifying water pollution



policy (November 2002) productivity, abstraction, health, pollution, land use planning, climate change and recreation in order to implement the Water Frameworks Directive.

issues arising from agricultural and urban diffuse pollution. Opportunity for improved understanding of the catchment and better land use planning in the future, taking into account varying characteristics across the catchment, including water quality, water demand and land use. Potential for complementary land use management policies to reduce soil erosion and surface water run off. Potential opportunities for returning watercourses to a more natural state.

Making Space for Water - Urban flood risk and integrated drainage (March 2005)

An holistic approach taking account of all sources of flooding, reflecting other relevant Government policies in the policies of flood and coastal erosion risk management. The aim will be to choose options that manage risks to reduce the threat to people and their property and deliver the greatest environmental, social and economic benefit consistent with the principles of sustainable development.

The CFMP must comply with management policies to address flood risk and coastal erosion. Opportunities to assess and improve the effectiveness of current flood risk management responsibilities and arrangements. Potential to identify opportunities for land use planning to encourage sustainable urban drainage.

Rural Land Management Planning

Land Use Management Plans and Polices, including Common Agricultural Policy (CAP), Single Payment Scheme (SPS), Environmental Stewardship (ES), and England Rural Development Plan (ERDP)

Holistic land use management plans and schemes promoting increased environmental protection. Farmers must maintain their land in good agricultural and environmental condition. Schemes also promote organic farming, energy crops, and increased woodland cover. There is likely to be a shift towards these schemes in the future, potentially reducing flood risk through sustainable land management practices. In the South East region, more woodland planting may occur and it is unlikely horticulture will expand so pesticide use and pressure on water resources should reduce.

Although limited information is currently available on how changes in land management influences flood flows at a catchment level, it is known that they do affect run-off at the plot level and therefore may be an important influence on the risk of flooding. These agri-environment schemes may have an effect on CFMP objectives and also incorporate additional opportunities and constraints such as conservation of wildlife (biodiversity), maintenance and enhancement of landscape quality and character, protection of the historic environment and natural resources.

Regional Forestry and Woodlands Framework for the South East

Framework to protect trees, particularly ancient ones, from loss and to bring woodland habitat back into good

Tree planning targets can potentially help reduce downstream flows (and do help us meet our flood



ecological condition while increasing their amenity value, potential for carbon sequestration and preservation of archaeological heritage. Also included are provisions for wet woodland restoration and river bank stabilisation.

risk management objectives). Soft engineering solutions, such as river bank stabilisation, would be supported under this framework. However, a possible constraint would be the protection of trees and woodlands from flood risk. This landscape scale approach to management would provide considerable scope for integrating objectives.

High Wealds AONB Management Plan Maintenance and enhancement of landscape character. Restoration of natural function of river catchments. Protection of sandstone outcrops.

Landscape character must be retained in general and particularly in AONBs. Opportunity for CFMP to reduce flood risk through restoration and protection of functional floodplains. Opportunity to improve public understanding and awareness of the benefits of river restoration. Protection and enhancement of UK and local BAP priority species and habitats (wetlands, wet woodlands and riverine habitats). Consideration of CFMP policy options’ impact on sandstone outcrops.

South Downs Management Plan (October 2007) Policies to reduce stress from abstraction, mitigate rising water demand, prevent drying of chalk streams and low flows, reduce soil erosion and water pollution and mitigate increasing flood severity and frequency.

Opportunity to improve river flow and reduce flood risk where areas may be vulnerable to flooding, or increase inundation for water compatible sites through floodplain and wetland restoration and maintenance of water flow to ditches. Consider threats of pollution to surface and groundwater due to flooding events. Consider future constraints of National Park status of Sussex Downs AONB. Alleviate abstraction pressure through increased storage elsewhere in the catchment.

Other Relevant Plans

UK Biodiversity Action Plan (BAP) and Local BAP for Sussex

Priority habitats found in the catchment are coastal and floodplain grazing marsh, saltmarsh, chalk grassland, heathland and several other habitats. Priority species include water voles, European otters and great crested newts. Fish species included are lamprey, European eel and brown/sea trout (the latter two of which have been added to the UK BAP list in

Presence of protected species with specific water level, water quality and habitat requirements must be considered. Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance. It is imperative that priority habitats and species are



2007). maintained and enhanced by preventing loss and damage to existing habitat, promoting new areas of habitat and improving quality through appropriate flood risk management activities.

Local Environment Agency Plan (LEAP) LEAP’s are a holistic approach to environmental management allowing the full range of management issues to be identified and considered within a geographical area, which is both relevant and meaningful. LEAP’s are seen as the key mechanism for prioritising actions arising from biodiversity action plans.

There is significant potential within the CFMP to protect, improve and enhance habitat species diversity and therefore comply with and help towards BAP targets. The LEAP has considered the potential contribution of riverine systems and habitats within the BAP framework and this will be considered as an objective in the CFMP.

South East England Regional Assembly – Destination South East Proposed Alterations to Regional Planning Guidance, South East, Tourism and Related Sport and Recreation (May 2003)

Objective to utilise and husband the region’s numerous environmental assets to foster sustainable tourism. Protecting access to and support proposals for upgrading inland waterways and associated facilities for recreational use in accordance with relevant management strategies. Avoid loss of waterside sites to uses that do not require deep-water access. There is also a strategic focus on the coastal strip of the South East.

There are opportunities within the CFMP process to contribute to the aims of this plan. For example, the restoration of wetlands and river corridors will increase the amenity value and tourism and recreation potential within the catchment. Efforts should be made to avoid disruption to existing recreation facilities through implementation of CFMP policies.


B3.2 Baseline review

Section 2 Catchment overview provides an overview to the characteristics of the catchment, including the environmental aspects relevant to the CFMP. Environmental issues within the catchment relevant to this CFMP are summarised below. Section B4. Assessment and evaluation of environmental effects provides more detail of the environmental characteristics of the individual areas most likely to be affected by the plan, their current state of the environment and the likely evolution thereof without implementation of the plan. People and communities At the household and community level, flooding can cause personal distress, poor health and damage to property and possessions as well as pose a threat to life. There are currently approximately 150 residential properties and approximately 400 people at risk across the catchment under a 1% annual probability flood outline. The majority of these properties are located in the Lower Adur and Ferring Rife, including Steyning, Upper Beeding, Bramber, Shoreham and Ferring, where flooding also occurs from surface water, groundwater and sewer systems. The Lower Adur is also the catchment most sensitive to future change. In total, it is predicted that the number of properties and people at risk from a 1% annual probability flood event will rise to approximately 2,400 and 5,800 respectively in 50-100 years time. The majority of these increases are attributed to significant increases in risk in Shoreham. There may be additional people at risk from the Teville Stream both now and in the future. We do not currently have sufficient information to assess the number of people at risk in the Teville Stream catchment. Property and infrastructure The AAD to property and agricultural land currently total approximately £5 million under a 1% annual probability flood outline and £0.3 million for more frequent flooding (10% annual probability). The majority of these damages are sustained in the Lower Adur and Ferring Rife catchments due to the large number of residential and commercial properties at risk in the towns of Steyning, Upper Beeding, Bramber, Ferring and Worthing. The low damage values in the Adur West Branch sub-catchment result from the rural and sparsely populated nature of the area. The damages in this area constitute the highest agricultural costs in the catchment. There are also currently 1 sewage treatment works and approximately 2km of main road under threat in the 1% annual probability flood outline and approximately 1.4km under the 10% annual probability flood outline. In 50-100 years, total AAD to properties and agricultural land are predicted to have increased to approximately £15 million, the length of main road affected to have increased to approximately 10km and a number of emergency services and hospitals become exposed to flood risk (1% annual probability). Numerous properties are at risk from surface water, groundwater and urban drainage flooding, particularly in Worthing and Brighton and Hove. Transport routes including the A23 and railway lines are also at risk of flooding. The environment In terms of the environment, there are currently approximately 5km2 of proposed National Park, approximately 1.5km2 of Environmentally Sensitive Area (ESA) and approximately 1.5km2 of Area of Outstanding Natural Beauty (AONB) at risk from a 1% annual probability flood outline. There are also 0.6km2 of Adur Estuary Site of Special Scientific Interest (SSSI), 3.5km2 of Sites of Nature Conservation Importance (SNCI) including the River Adur Water Meadows, Wyckham Wood and Ferring Rife and Meadows (1% annual probability). In 50-100 years, these areas are not expected to have expanded significantly. There is a degree of tourism and recreation value associated with these sites. There are also issues of soil erosion and surface water run-off that cause a significant problem to the environment and in terms of depositing ‘muddy’ flooding to properties in Worthing and Brighton and Hove which are downstream of the South Downs. There are also water quality issues associated with this which have the potential to cause


problems within designated sites. There is significant potential within this catchment to restore geomorphological processes to reduce these problems as well as flood risk in general.

B3.3 Scope of the SEA and environmental objectives

An important early stage in the SEA process is to identify which environmental issues are relevant to this CFMP. Our Scoping exercise identified issues that are not relevant to this type and level of plan: allowing us to exclude these issues and focus our assessment on what is most important. To help us do this we consulted widely on a Scoping Report which was published in March 2006. The scope of this SEA was determined by:

• developing an understanding of the flood risk management context for the catchment, including current flood risk to people and the environment (we also considered the economy), and the potential constraints and opportunities to the management of flood risk;

• undertaking a review of the environmental context of the catchment, including identifying relevant trends;

• a review of relevant plans and policies, including an assessment of their relationship with catchment flood management planning;

• identifying relevant environmental protection objectives from these plans and policies and consideration of how the CFMP might conflict with these, or influence their achievement; and

• consultation with key stakeholders (see previous Section B2), including the SEA statutory consultation bodies Natural England and English Heritage.

The environmental and social issues scoped into the SEA were then used alongside economic issues to develop a suite of policy appraisal objectives, indicators and, where possible, targets (see Section 5.3 CFMP Objectives. Throughout this process we drew on the knowledge and vision of our CFMP Steering Group (see Section 1.5 Involving others) to help understand what matters in the catchment and shape what this plan was trying to achieve. Following our formal Scoping exercise, we considered what the future might look like, including what the effects of climate change could be, and the impact of future development pressures and changes in land management. While we can not predict the future with complete certainty, we used this perspective on the future to help us understand the scale of changes we could face in the future and so consider them explicitly within the development of the plan. Table B3 summarises the issues we scoped into the development of the plan, and the resulting broad objectives we developed against which to test our alternative options. Not all of these issues are equally relevant everywhere in our plan area, and we also drew on other relevant policies, plans and programmes to identify opportunities and constraints for individual areas (policy units) within the plan area.


Table B3 Scope of the SEA in relation to the CFMP Environmental

Topic Scope and Justification Relevant environmental

objective Relevance to the CFMP

Scoped in Scoped out

Population and Human Health

People and properties exposed to flooding and the risk of being drowned due to flooding. Risk flooding to people has been considered for all populations in the catchment with specific quantitative analysis of those in floodplains. Nationally and regionally important infrastructure and transport routes which are in the 1% AEP outline or greater.

Disease as a result of flooding. A robust assessment of the risk associated with these impacts is not established for this level of plan. The CFMP will not have a significant effect on employment at a catchment level; this will be assessed at project EIA stage. The CFMP will not have a significant effect on noise at a catchment level; this will be assessed at project EIA stage.

Ensure the impact of flooding on people and properties does not significantly increase in the future (for example due to climate change). Ensure the disruption caused by flooding to transport and critical infrastructure does not significantly increase in the future (for example due to climate change).

There are people at risk from flooding across the CFMP area, a total of approximately 400 (1% annual probability), the majority of which are located in the densely populated Lower Adur and Ferring Rife. There may be additional people at risk from the Teville Stream. We do not currently have sufficient information to assess the number of people at risk in the Teville Stream catchment. There are approximately 150 residential properties at risk from a 1% annual probability event across the catchment. There are also people at risk from surface water, groundwater, and urban drainage flooding, particularly in Brighton and Hove, where key transport routes were disrupted in 2000. There are also 1 sewage treatment works, approximately 2km of main road and a negligible length of railroad at risk from flooding (1% annual probability).

Material Assets Economic damage and Annual Average Damages (AAD) to properties and agricultural land. Recreation and amenity value of waterways and

Ensure flood damages do not significantly increase in the future (for example due to climate change). Ensure that river channel and flood defence maintenance

Across the CFMP area, AAD due to flooding of property are approximately £0.22 million (1% annual probability), the majority of which occur in the densely populated Lower Adur and Ferring Rife catchments.


Environmental Topic

Scope and Justification Relevant environmental objective

Relevance to the CFMP


countryside.

expenditure is appropriate to the economic damage of flooding.

AAD to agricultural land are approximately £0.2 million and the area of agricultural land at risk totals approximately 15km

2 (1% annual

probability). Tourism is of significant economic importance to the catchment especially in the coastal areas. There is one caravan park located in Ferring and one in Sompting which are both at risk from fluvial flooding. Not only should the amenity value of the area be protected from flood damage or intrusive flood management, there is also potential to increase it through wetland creation, river restoration and other flood alleviation measures.

Landscape Landscape designations including proposed National Park, Areas of Outstanding Natural Beauty (AONBs), proposed National Parks and Environmentally Sensitive Areas (ESAs).

Landscape character areas Restore rivers and floodplains to a naturally functioning state where feasible.

Areas of the High Weald and Sussex Downs AONBs and South Downs proposed National Park and ESA are at risk from flooding. Approximately 4.2km

2 of these sites are at risk from

a 1% annual probability flood event. This area increases only slightly in the future.

Historic Environment, including cultural, architectural and archaeological heritage

This CFMP does not have potential to significantly impact on flood risk to listed buildings.

For the purposes of the CFMP process it can be assumed that buildings located within the floodplain have potential to suffer damage during flooding. Listed Buildings are the only historic assets which we can be certain

Not applicable There are nearly 3,000 listed buildings within this catchment of which only 6 are currently at risk from a 1% annual probability flood event. This number increases by only 2 in the next 50-100 years. This CFMP therefore does not have the potential


Environmental Topic




are buildings and can therefore be assumed to have potential to be damaged by flooding. Other historic assets have therefore not been considered in this CFMP. The CFMP could have a significant effect on Conservation Areas. However, due to the large number of these sites within the CFMP area these effects will be assessed at project stage. The risk of impacting upon other known and unknown undesignated heritage sites and/or features of archaeological interest is considered to be outside the scope of this plan and any potential impacts will be considered where necessary at project stage.

to significantly impact flood risk to listed buildings so no specific objective has been included. These identified sites have therefore been considered as constraints to FRM activities, along with other historic environment assets.

Air quality No air quality issues are relevant to this level of plan

There is no potential for CFMP policies to influence issues that effect air quality, e.g. emissions or generation of particulate matter at a strategic level. Air quality issues are therefore not considered to be significant and have been scoped out of the assessment.

Not applicable

Not applicable

Climatic factors The plan explicitly considers the implications of climate change on flood risk. Our policies are therefore aiming

There is no potential for CFMP Policies to influence issues that affect the local climate.

Not applicable

Not applicable


Environmental Topic




to help society to adapt to climate change

Biodiversity, fauna and fauna

Sites of Special Scientific Interest (SSSIs) and Sites of Nature Conservation Importance (SNCIs) and Biodiversity Action Plan (BAP) Habitats and Species where these have some dependence on the water environment and flooding. Restoration of floodplain function and naturalisation of river channels.

There are no sites designated as Special Protection Areas (SPAs), Special Areas of Conservation (SACs), Ramsar within the CFMP area. Sites of local conservation importance have not been included. The CFMP will not have a significant effect on sites of local conservation importance at a catchment level; this will be assessed at project EIA stage.

Protect and enhance nationally and internationally important species and habitats. Restore rivers and floodplains to a naturally functioning state where feasible.

Although there are no SPAs, SACs or Ramsar sites in the CFMP area, there are numerous Sites of Nature Conservation Importance (SNCIs), of which approximately 3.3km

2 are at

risk from flooding (1% annual probability), including the River Adur Water Meadows, Wyckham Woods and the Ferring Rife and Meadows SNCIs. There are also SSSIs designated for their ecological or geological importance at risk from flooding. None of these SSSIs require Water Level Management Plans (WLMP) and only an area of approximately 0.06km

2 at risk from

flooding (1% annual probability). Of these, only the Adur Estuary SSSI is at significant risk of flooding. The Local BAP for Sussex includes action plans for coastal and floodplain grazing marsh, saltmarsh, chalk grassland and heath and several other habitats that are all found in the CFMP area. BAP priority species in the catchment include the otter, great crested newt, pipistrelle bat and brown/sea trout.

Soils FRM policy could have a significant effect of surface water run-off on erosion of soils from the land and on transport of sediment.

The CFMP will not have a significant effect on coastal geomorphology. The CFMP will not have a

Reduce the impact of muddy flooding. Restore rivers and floodplains to a naturally functioning state

The South Downs have steep slopes with poorly draining silty soils which contribute to surface water flooding in parts of the catchment which in turn leads to problem muddy flooding in


Environmental Topic




FRM policy could have direct or indirect effects on fluvial geomorphology and could offer opportunities to restore natural systems.

significant effect on contaminated land at a catchment level; this will be assessed at project stage. FRM policy will not have a significant effect on geology at a catchment level; this will be assessed at project stage. FRM policy will not have a direct or indirect significant effect on land use and land management.

where feasible. the urban areas downstream of the South Downs, namely Worthing and Brighton and Hove. Poor agricultural practice can significantly increase surface water run-off rates and therefore increase flood risk downstream. Flooding has been caused as a result of poor land management practices in the past at Sompting, Patcham, Bevendean, Woodingdean, Ovingdean, Westdene and Mile Oak.

Water The potential for flooding and FRM to affect the achievement of good ecological potential of water bodies.

FRM effects on water resources (surface and groundwater) are not of strategic importance in the catchment. There is no significant potential for an increase in poor quality water (and secondary impact on designated sites). There is limited potential for flooding to affect the quality of water through foul water flooding, surface water flooding and/or the flooding of water treatment works.

Protect and enhance nationally and internationally important species and habitats.

There are several water quality issues in the catchment including diffuse pollution from urban areas and roads entering watercourses, run-off from agricultural land and increased sediment from soil erosion caused by surface water run-off and also from scour within the river channels, which can damage fish spawning habitats. There is an opportunity for flood risk management to include features which both improve water quality and alleviate the risk of flooding e.g. creation of wetlands.

Environment Agency River Adur CFMP - Appendix B (September 2008) 30

B4 Assessment and Evaluation of

Environmental Effects

B4.1 Strategic options and appraisal process

We have considered six generic options in our policy plan, which are listed in Table B4. Table B4 Definition of policy options

Policy option Risk management strategic approach

1. No active intervention (including flood warning and maintenance). Continue to monitor and advise

Accept the risk – both current and future increases in risk

2. Reduce existing flood risk management actions (accepting that flood risk will increase over time)

Accept the risk – both current and future increases in risk

3. Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline)

Accept the risk – our current scale of actions is sufficient to manage the current risk, and future increases will be acceptable

4. Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and Climate Change).

Accept the risk – but in the longer term take action to ensure the risk does not increase from current level

5. Take further action to reduce flood risk (now and/or in the future)

Reduce the risk – lower the probability of exposure to flooding and/or the magnitude of the consequences of a flood, and hence the risk

6. Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, (which may constitute an overall flood risk reduction, for example for habitat inundation).

Reduce the risk by transferring the risk to other locations where the risks (typically the consequences) are positive

These options relate to the outcome of flood risk management in terms of the scale of risk and management activity compared to today. Deciding on the specific measures needed to achieve these outcomes is not the purpose of the CFMP. However, we do need to appreciate whether or not the change in risk under a particular policy is generally feasible and desirable in terms of where the water goes in the catchment. To appreciate this we need to understand how the catchment works in times of flood so that our policies make sense. The water needs to go somewhere when it floods and we need to understand that if we prevent water from flooding homes in one location what the knock-on effects would be in another location. In order to understand how the catchment works we develop models that can draw on information about the amount of rainfall and show to some extent how this drains off the land and into the river systems. We can then consider at a broad scale how the flow of water within the catchment could change over time with or without management intervention. Of particular importance in driving future changes in flood risk are:

• the potential impact of climate change on flooding due to increased rainfall and sea level rise;

• the potential impact of new development due to extra run-off from impermeable surfaces as well as new properties being developed in areas exposed to flooding; and


• the potential impact of changes in land management because this can change the permeability of the catchment and how the rate at which water drains into the river system.

To consider what future flood risk might be like, including the effect of having no management intervention, we have considered a number of future scenarios. These scenarios aim to establish what changes there could be in the three important drivers of change listed above (climate change, development and land management). To develop reasonable predictions of change we have looked at past changes and had discussions with our Steering Group to arrive at reasonable projections of what the future could be like. To consider the impact of climate change on flooding we have used the government guidance issued by Defra (2006). A more detailed explanation of the scenarios used is given in Section 4.2 Scenarios. Our appraisal of the alternative policies is undertaken by considering how the flow within the catchment could change in the future. This understanding is done at a high level using our models, complemented with expert judgement on how water flows through the catchment during times of flood. For example, we might say that if land management practices changed in the headlands of a catchment, the land would be more permeable and this would reduce the rate at which rainfall enters the river system downstream. Such a change in how water flows through the catchment could then reduce the volume of floodwater downstream (and reduce the frequency of flooding to homes in this downstream location). Our consideration of how the catchment works, and what the current and future risks are has allowed us to divide the catchment up into smaller geographical areas that we have called policy units. In each policy unit we have considered how the risks arise (using a source-pathway-receptor model) and what our specific objectives are. We have considered other policies, plans and programmes to see where there may be objectives and constraints that our plan could contribute to or that we need to take account of. For example, a BAP may identify habitat improvement such as creation of wet woodland. Our investigations could start to show that if the area adjacent to the river corridor was to flood more frequently, then this could potentially help contribute to achieving the BAP improvements. The process of SEA encourages us to make these links with other plans so that we can help deliver broader benefits and reduce conflict between our flood risk management policies and other aspirations. We have done this during the review of other plans and considered others’ objectives as opportunities or constraints to our policy development, as an integral part of our appraisal.


Policy Appraisal Tables CFMP title: River Adur CFMP

Policy author: Capita Symonds

Date on which policy appraisal was started:

December 2006

Iteration number: Draft 3

The following forms are based on our integrated policy appraisal process, modified for use on CFMPs. The forms pull together all the key data and information gathered throughout the CFMP development process. The first four and last forms are generic to the CFMP area and these are listed below. A further seven forms are specific to each policy unit and are presented in order of policy unit.

Index of Policy Appraisal forms Generic forms: Form B1 – Purpose of the CFMP. Form B2 – Meeting legal requirements. Form B3a – Summary of flood risk – including an explanation of model results from ‘drivers’. Form B3b - Source-pathway-receptor table with objectives and suggested flood risk management responses. Form B4 – CFMP policy options. Form B11 – Signature of CFMP project manager. For each policy unit: Form B5 – Summary of current and future levels of and responses to flood risk. Form B6 – Appraisal of policy options against policy unit objectives. Form B7 – Summary of losses and gains. Form B8 – Summary of preferred policy. Form B9 – Requirements for further policy development and appraisal. Form B10 – Indicators for monitoring, review and evaluation.


Form B1 Purpose of the CFMP This form contains the key catchment specific objectives, opportunities and constraints that need to be taken into account when developing the CFMP, including Biodiversity Action Plan targets, environmental targets and housing targets. These factors have been reviewed and amended through consultation undertaken in the scoping stage and during the draft CFMP stage.

Catchment objectives

Economic - Ensure flood damages do not significantly increase in the future (for example due to climate

change). - Ensure that river channel and flood defence maintenance expenditure is appropriate to the

economic damage of flooding.

Social - Ensure the impact of flooding on people and property does not significantly increase in the

future (for example due to climate change). - Ensure the disruption caused by flooding to transport and critical infrastructure does not

significantly increase in the future (for example due to climate change). - Reduce the impact of muddy flooding.

Environmental

- Restore rivers and floodplains to a naturally functioning state where feasible. - Protect and enhance nationally and internationally important species and habitats.

Catchment opportunities and constraints

Opportunities:

• Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities.

• Help meet national biodiversity action plan (BAP) targets.

• Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character.

• Move toward more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character.

• Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

• Influence the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area.

• Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove, Worthing, Shoreham and Burgess Hill).

• Reduce flood risk and improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham and Burgess Hill.

• Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream.

• Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding.

• Develop a flood warning system for groundwater flooding.

• Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill.

• Reduce surface water run-off and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council).

• Support the existing flood defence measures in relation to surface water flooding, such as


bunds provided by Brighton and Hove City Council.

• Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill.

• Improvements in the efficiency of channel and flood defence maintenance processes.

• Effective and efficient use of developer contributions for flood risk management.

• To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate. Constraints:

• Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.

• Existing urban development may prevent reinstatement of natural river processes.

• Individual homes and properties are currently at risk of flooding.

• Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032.

• Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance.

• Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions.

• Presence of protected species with specific water level, water quality and habitat requirements, for example in the Adur Estuary SSSI.

• Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences).

• No degradation of existing fish passage and habitat.

• Visual impact of flood risk management activities within the proposed National Park or Areas of outstanding Natural Beauty.

• Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events.

• A suitable level of productivity from agricultural land needs to be retained.

• Changes to flood risk management can affect the landscape, its character and value as an amenity.

• CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area.

• Available funding for the initial implementing new flood risk management schemes.

• Older flood defence structures are likely to be costly to maintain.

• Limited available information on surface and groundwater flood damages. Local Biodiversity Action Plan (from Rio to Sussex): BAP targets consisting of specific species action plans (SAPs) and habitat action plans (HAPs)

Species Action Plans (SAPs) for Sussex:

Barn Owl (Tyto alba) The Rother, Arun, Adur and Ouse river valleys of Sussex were considered to be nationally important in the Hawk and Owl Trust’s (HOT) National Conservation Plan for the Barn Owl, 1988-2008. Barn Owls are birds of low-lying open farmland and woodland edge. They feed on small mammals, predominantly the short-tailed vole, but also mice, shrews and small rats. They require extensive areas of prey-rich habitat, usually rough, ungrazed or lightly grazed tussocky grassland in the form of whole fields, field margins, parkland, orchard and newly planted plantations. There is considerable potential to increase the Barn Owl population in Sussex. Black Poplar (Populus nigra) The black poplar is considered to be native to Britain and is a tree of wet woodland and forested floodplain. Historically it is a significant tree in Britain and once played a substantial role in local economies and culture. In Sussex, thirty three individual trees have so far been identified. Although the number of black poplars in the country is low, it is likely that the Sussex population is significant on a national scale. Brown Hare (Lepus europaeus) The brown hare is a common and conspicuous farmland species in Britain, probably introduced by the Romans in ancient times. Formerly considered abundant, the brown hare appears to have undergone a substantial decline in numbers since the early 1960s. Carder Bumblebee (Bombus humilis) The carder bumblebee makes its nest on the surface of the ground at the base of long vegetation, often under accumulated plant litter. It has most often been


recorded as associated with areas of grassland supporting a large number of plant species with long corolla flower types, notably those belonging to the plant families Lamiaceae and Fabaceae. It is one of a number of bumblebee species to have undergone a drastic reduction in range and abundance, as a result of the loss of this habitat in the modern agricultural landscape, although it appears to be able to survive in less extensive areas of flower-rich habitat compared with some bumblebee species. Duke of Burgundy (Hamearis lucina) The Duke of Burgundy butterfly has a primarily central southern distribution in England, with isolated populations on the limestone of south Cumbria/north Lancashire and the north Yorkshire moors. The Duke of Burgundy was once widespread throughout much of lowland England and there are a few historical (pre 1940) records from Wales. The butterfly is found on most areas of the chalk grassland of lowland England, with centers of distribution in Wiltshire, Hampshire and West Sussex. European Otter (Lutra lutra) The Eurasian or European otter is a semi-aquatic mammal that inhabits a variety of wetland environments; ranging from rivers, lakes and streams to marshes and coastal areas. Hunting in the 1960s, the introduction of organochlorine pesticides and habitat loss from land drainage activities significantly affected populations in the UK. By the late 1970s only 6% of sites inspected in the UK showed signs of otters. Now legally protected otter populations have started to slowly rise. Recent evidence of otter activity in a number of catchments in both East and West Sussex has been found, although there is some speculation as to whether the sightings are due to natural recolonisation or reintroductions that have taken place. Fen Raft Spider (Dolomedes plantarius) The fen raft spider is a wetland spider dependent on permanent, standing or slow moving water. It is associated with nutrient-poor water of near neutral or alkaline pH. It lives on the surface of pools and ditches, and amongst emergent vegetation; typically it hunts from ‘perches’ on stems emerging from the water, taking a wide range of invertebrate prey on or below the surface. Emergent, stiff-leaved vegetation in open, sunny conditions is also required for the construction of nursery webs in which the young are reared. Areas of suitable habitat have been identified in West Sussex for the location of a population of this species. Glow worm (Lampyris noctiluca) Actually a beetle, with preferred habitats defined as “downland, pastures, meadows, roadside verges, hedgerows, railway embankments, churchyards, golf courses, gardens, moorland, heathland, quarries, canal towpaths, and waste ground”. The structure of vegetation, in other words its height, density, shade and shelter, may be more important than its composition. Also, a mixture of open grass and some form of cover such as scrub, brambles or woodland edge is preferred to pure woodland or pure grassland. Good populations present in the catchment in the South Downs and to a lesser frequency in the Low Weald. The habitat requirements for the insect are maintained at the Lewes Railway Land Local Nature Reserve. Great Crested Newt (Triturus cristatus) Sussex appears to have an internationally significant resource of this species, even though the majority of sites have yet to be identified. The distribution is by no means uniform across East and West Sussex. The greatest concentration of breeding ponds appears to be in the middle of Sussex, with Lewes and Wealden Districts having the largest number, followed by Mid-Sussex and Horsham Districts. Populations have also been identified within the conurbations along the south coast. Areas of the Downs around Brighton are known to support viable populations. Pipistrelle Bat (Pipistrellus) The pipistrelles are Britain’s smallest bats and are the most comment species in towns. Although it remains the most abundant and widespread bat species in the UK, the pipistrelle is thought to have undergone a significant decline in numbers this century. Estimates from the National Bat Colony Survey suggest a population decline of approximately 70% between 1978 and 1993. The pipistrelle can be found throughout Sussex, in varying population densities. The highest populations are found in the Wealden areas and the lowest on the Downs. Skylark (Alauda arvensis) One of the most widespread birds of the UK, with over 1 million breeding pairs, the resident population is joined in winter by a significant proportion of the northern European population - possibly up to 25 million individuals. Nonetheless, the UK breeding population of skylark on lowland farmland declined by 54% between 1969 and 1991. The skylark is still commonplace in Sussex, particularly on the Downs, although its distribution is somewhat patchy. Song Thrush (Turdus philomelos) This is a common and widespread species, which is declining throughout the UK. Following the winter of 1962/63, the population declined but recovered to a stable level within three to four years. The numbers subsequently remained stable until the mid 1970s after which they declined steadily, with an estimated reduction of 73% in farmland and 49% in woodland habitats. These birds are generally more abundant in the east than the west of the country. Song thrush densities are highest in the Weald. Stag Beetle (Lucanus cervus) This large and conspicuous beetle is rare and protected in some European countries, but is still widespread in southern England, especially the Thames valley, north Essex, south Hampshire and West Sussex. It also occurs fairly frequently in the Severn valley and


coastal areas of the southwest. Outside these areas the records are sparse and often old, indicating some contraction of the beetle’s range. This species is well distributed within West Sussex, with areas around Shoreham being traditional geographical hot spots.

Habitat Action Plans (HAPs) for Sussex:

Arable Land (including Field Margins) Arable land under this definition covers all cultivated land, including arable crops, grass leys, vegetables and non-food crops as well as the field margin. There is a range of different geology, soil types and landscape across Sussex which favour differing farming practices and support widely differing plant and animal communities. Chalk Grassland (Lowland calcareous grasslands) In the UK chalk grasslands are developed on shallow lime-rich soils most often derived from chalk and limestone rocks. Orchid-rich chalk grassland is identified as a priority in the European Habitats Directive. About a fifth of the country’s chalk grassland was lost between 1966 and 1980. It now covers only 3% of the area on the South Downs; the remaining resource is largely confined to slopes too steep to plough, such as the north-facing escarpment. Coastal Vegetated Shingle Shingle is defined as sediment with particle sizes in the range 2-200mm. It is a globally restricted coastal sediment type with few occurrences outside northwest Europe, Japan and New Zealand. The vegetation communities of shingle features depend on the amount of finer materials mixed in with the shingle and on the hydrological regime. Small areas of vegetated shingle occur at a number of sites within the CFMP area, including Shoreham, Littlehampton, Kingston, Worthing and Lancing. Estuaries (including mudflats) A natural dynamic estuary comprises extensive areas of both aquatic and terrestrial habitats, the composition and location of which will change over time as a result of geomorphological processes. In addition to dynamic processes, the aquatic elements of estuarine systems are dependent on two main factors, the land levels and the degree of salinity. Mudflats are sedimentary intertidal habitats created by deposition in low energy coastal environments. In the CFMP an area of 37 hectares has been classified as an estuary with mudflats and sandflats and the component habitats. Floodplain Grassland The habitat types covered by this plan are periodically inundated pastures or meadows with ditches, which maintain water levels, containing standing brackish or fresh water. Wet grassland have a high nature conservation value and support a wide range of plant, bird and invertebrate species, many of which are rare and/or declining. The rivers Adur, Arun, Ouse and Cuckmere all have important areas of floodplain grassland. Hedgerows (species-rich and/or ancient hedgerows) A hedgerow is defined as a boundary feature, which are less than five metres wide and comprised of predominantly shrub and/or tree species. A species-rich hedgerow is one that has, on average, five or more native, woody, shrub or tree species per 30m length. An ancient hedgerow is one that was in existence before 1850, predating the establishment if current civil parishes. In Sussex the Weald appears rich in ancient and species-rich hedgerows. Lowland Heathland Lowland heathland forms an open landscape, generally occurring on poor, acidic, sandy soils and is characterised by the presence of plants such as heather, dwarf gorses, and cross-leaved heath. Heathland is a priority for nature conservation because it is an internationally rare and threatened habitat. In Sussex, heathland occurs principally in two Natural Areas; the Wealden Greensand and the High Weald, but in former times it may have occurred more extensively in the Low Weald and elsewhere.

Marine HAP for Sussex is currently under production (January 2007).

Maritime Cliff and Slope HAP for Sussex is currently under production (January 2007).

Minerals Mineral sites in West Sussex include quarries and pits from which gravel, sand, clay, chalk and sandstone are being, or have been, extracted. Although mineral extraction is a commercial operation, mineral sites encompass a high range of different habitats, features and conditions and are potentially very important for biodiversity conservation. There are in the region of 50 mineral sites in Sussex (including both active and restored sites) that are likely to have at least some interest for biodiversity or geodiversity. Road Verges The road verge can be regarded as being made up of a wide range of habitats and their associated species. The habitat is determined by a range of factors including the underlying geology, the naturally derived soils or soils which have been important onto the verge and the management of the verge. The habitats found on the roadside verges in West Sussex are extremely varied, currently there is little recorded detailed knowledge of the physical and biological characteristics of the whole resource.

Saline Lagoons Bodies of saline water, either natural or artificial, that are partially (but not completely)


separated from the adjacent sea. Saline lagoons are important for both the plant and invertebrate communities they contain, some of which are reliant on this habitat. Saline lagoons are a nationally rare habitat type; in Sussex they cover a total of 69 hectares (only 5% of the total English coverage). Standing Fresh Water This plan covers all standing fresh waters from ponds of one square metre up to large lakes. Small ponds are very important features of the Sussex landscape. In the past these would have been created through seasonal flooding and meandering of natural river systems. Sussex Woodlands Includes a great range of types and those present within the CFMP area are; Lowland Beech and Yew Woods, Wet Woodlands Lowland Mixed Deciduous Wood and Undetermined woodlands. Sussex is one of the most wooded parts of lowland Britain, with the Weald having the greatest cover of woodland in Britain. Unimproved neutral grassland and acid grassland Unimproved neutral grassland is a feature of lowland mineral soils with a pH between 5 and 6.5 and which are neither very wet nor very dry. Neutral grasslands are found throughout Britain where suitable soils and soil moisture are present. In Sussex unimproved neutral grasslands are relatively evenly distributed through the Sussex Weald. Dry acid grasslands are fairly widespread in Britain where sols are base poor. Recorded dry acid grasslands in Sussex are few in number and randomly scattered where suitable soils are present, but may be more widely associated with heathland. Urban the definition of urban areas is broad to cover all areas of human settlement. The biodiversity in urban areas include a complex mosaic of semi-natural and artificial habitat types, many of which are covered in other individual Habitat Action Plans (HAPs). This includes urban woodland included in the Woodland HAP and urban green spaces that are not covered in other plans. There are a large number of additional environmental initiatives and objectives that relate to the CFMP area. The main ones are as follows:

• The Environmentally Sensitive Areas Scheme was introduced nationally in 1987 to offer incentives to encourage farmers to adopt agricultural practices which would safeguard and enhance parts of the country of particularly high landscape, wildlife or historic value.

• The South Downs is classified as an Environmentally Sensitive Area (ESA) and 250 voluntary agreements under the ESA scheme across the South Downs were made.

• Defra introduced a new Environmental Stewardship Scheme in March 2005 which supersedes (with enhancements) the Environmentally Sensitive Areas and Countryside Stewardship Schemes. These schemes help to achieve targets within the BAPs, for example the schemes include payments for reinstating hedgerows hence supporting the Sussex Hedgerow Habitat Action Plan. Additionally reducing flood risk is stated as a secondary goal to the schemes.

• Others Rural Development Programme schemes include Woodland Grants Scheme, Farm Woodland Premium Scheme, Hill Farm Allowance, and the Organic Farming Scheme.

• West Sussex County Councils area-based Countryside Management Unit implements heathland restoration/recreation schemes in liaison with private landowners in both the High and Low Weald. By 1998, 1,109 hectares of heathland were managed under Defra's Countryside Stewardship Scheme and 128 hectares under English Nature's Wildlife Enhancement Scheme (WES).

• Adur District Council produced a wetland feasibility study on the lower Adur in March 1997 entitled ‘The potential of restoration of wetland biodiversity’.

• A River Adur restoration project at Knepp Castle Estate is proposed to commence in 2007. The aim is to re-naturalise the river, restoring its natural meaders and thereby reintegrating the surrounding floodplains. In doing this it is hoped the process will encourage the return of insects and amphibians, important marsh plants and riverine trees like black poplar.

Future housing targets for the CFMP are as follows:

• The South East Plan – Proposed Sub-Regional Strategy for the Sussex Coast recommends developing up to 17,000 homes between Worthing and Brighton and Hove between 2001 and 2026, with accompanying infrastructure improvements linked to an emphasis on economic and business growth.

• Annual average housing targets in South East Plan Policy HC1 shown in brackets; Adur (130), Worthing (330), Horsham (620), Mid Sussex (705) and Brighton and Hove (550).


• The West Sussex Structure Plan 2001 – 2016 sets a target to ensure the provision of an annual average rate of 3,100 dwellings within Adur, Mid Sussex, Horsham Districts and Worthing Borough.

• The East Sussex and Brighton and Hove Structure Plan 1991 – 2011 sets a total housing provision of 9,400 dwellings in Brighton and Hove by 2011.


Form B2 Legal requirements This form lists the legal requirements and Government and Environment Agency targets that CFMP policy needs to comply with or support.

Environment Agency corporate measures for flood risk management:

• Sustained objections to development in Flood Zones.

• People taking appropriate action in response to flooding based on our advice.

• Increase the proportion or properties (homes and businesses) within the indicative floodplain that have been offered an appropriate flood warning service.

• Increase the number of houses which benefit from reduced flood risk.

• All flood systems to be in the condition required by the performance specifications.

• Delivery of Operation Public Safety (OPUS).

• Produce Catchment Flood Management Plans (CFMPs) for all principal catchments.

• All data stored in the National Flood and Coastal Defence Database (NFCDD) will have Data Quality Indicators.

• All new data entered in NFCDD in the year will be spatially accurate and be fully attributed.

• Environment Agency Flood Maps comply with policy guidance.

• Deliver Water Level Management Plans on 72 priority SSSIs to achieve Favourable/Unfavourable Recovering condition by 2010.

• Create at least 200 hectares of new Biodiversity Action Plan (BAP) habitats as a result of flood management activities, of which at least 100 hectares should be salt marsh and mudflat.

• Decrease the proportion of major infrastructure within the floodplain that is at risk of not being available for its intended use at times of flood.

• Optimise economic return from relevant Flood Risk Management activities.

• Improve the effectiveness and efficiency of investment in asset management.

• Improve efficiency by reducing the cost of decision making and overheads and savings from procurement best practice.

• As part of the above target, reduce the cost of developing and implementing capital flood defence schemes, as a percentage of total relevant costs (taken year on year).

Government targets:

• High Level Target 4 – Biodiversity.

• High Level Target 5 – Flood defence inspections and assessment of flood risk.

• High Level Target 12 – Development and Flood Risk.

Legal requirements:

• Conservation (Natural Habitats, &c.) Regulations 1994.

• The Water Environment (Water Framework Directive) (England and Wales) Regulations 2003.

Will the appraisal include/meet other specialist appraisal needs? Yes

Is so, state which:

The appraisal process has been prepared within the spirit of the SEA Directive. Thus, in addition to appraising policies against catchment objectives and legal requirements, policies will also be appraised against catchment opportunities and constraints.


Form B3a Summary of flood risk – including explanation of model results from ‘drivers’

This form provides an overview of flood risk within the catchment. It contains maps showing the extent of flooding during the 1% annual probability flood event, a summary table of current flood risk and a summary table of environmental issues related to flooding. This form also contains a table summarising the likely future changes in the catchment for a range of future scenarios and the flooding consequences of these changes. Estimates of the 1% annual probability flood damages for the current basecase and the future scenario for each catchment are also included.

Adur East Branch

Figure B3.1 - Adur East Branch: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2006 baseline conditions)


Current flood risk – Adur East Branch

Flooding source and places at risk

Pathway and people/ property affected

Current flood risk and scale of disruption

Burgess Hill Fluvial flooding from River Adur and tributaries running through Burgess Hill. Surface water flooding from urban and road drainage systems.

River channel under capacity can cause localised flooding. Under capacity and blocked urban drainage systems. Localised flooding to properties and roads in Burgess Hill.

Less than ten properties are thought to be at risk from flooding in Burgess Hill. Flooding is generally short lived, and relatively shallow. Both disruption and hazard are assessed as low. Flood damages only occur under extreme and unlikely flood events and rely on blockage of infrastructure; flood risk is assessed as low.

Hassocks Surface water flooding from urban road drainage systems in Hassocks.

Under capacity and blocked urban drainage systems. Surface water and overland flow. Localised flooding to properties and roads in Hassocks.

A small flood alleviation pond (Keymer Pond) is located to the West of Hassocks and attenuates the peak flows of one of the tributaries running through Hassocks. Flooding is generally short lived and relatively shallow, however because of the steep surrounding hills, inundation may be relatively fast, although the ground is not considered steep enough to result in dangerously high water velocities. Less than ten properties are thought to be at risk of this type flooding in Hassocks. Both disruption and hazard are assessed as low and therefore flood risk is assessed as low.

Wivlesfield Surface water flooding from urban and road drainage systems in Wivlesfield.

Surface water and overland flow in and around Wivlesfield. Properties, roads and land affected in Wivlesfield.

Small localised disruption to roads and properties. Duration of the flooding is short (less than five hours) with low velocities. Because of the low disruption and hazard the flood risk is assessed as low.

Current flood risk to the environment – Adur East Branch

Flooding source Pathway and habitat affected Current flood risk and scale of

impact

None identified


Figure B3.2 - Adur East Branch: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2106 baseline conditions)

The following tables provide a summary of how flooding may change in response to future changes within the catchments, and what the implications of these changes might be. A broadscale model has been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages.


Adur East Branch – Future scenario (climate change: 20% additional fluvial flow and sea level rise of 600mm)

Results from broadscale modelling 1% annual probability fluvial

flood damages (£million)

Broadscale modelling showed that the catchment was insensitive to the small amount of urban growth that is predicted in the Adur East Branch area as a whole, in terms of flooding, and so was not included in this scenario. Modelling climate change has shown a small increase in flood damages in this area, which is mainly due to increased fluvial flow. It is anticipated that urban growth in Burgess Hill will be large and as such the number of properties at risk will increase significantly in the future and as such the future damages may be larger in this community than predicted by the broadscale modelling assessment.

Basecase = £0.31

Scenario = £0.52

Conclusions

The Adur East Branch catchment appears not to be sensitive to our future change scenario. We have found very little serious flood damages as a result of fluvial flooding in this part of the CFMP catchment. However pressures for development may results in greater damages in Burgess Hill than predicted.

Future flood risk to the environment – Adur East Branch


impact

None identified


Adur West Branch

Figure B3.3 - Adur West Branch: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2006 baseline conditions)

Current flood risk – Adur West Branch




West Grinstead Surface water flooding and run-off from highway drainage.

Road drainage problems affecting the A272 and B2135, causing minor road and land flooding around West Grinstead.

The risk of flooding is very small in this catchment, with minimal to no disruption caused. Flood risk is assessed as low to none.


Current flood risk to the environment – Adur West Branch


impact

None identified

Figure B3.4 - Adur West Branch: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2106 baseline conditions)

The following tables provide a summary of how flooding may change in response to future changes within the catchments, and what the implications of these changes might be. A broadscale model has


been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages.

Adur West Branch – Future scenario (climate change: 20% additional fluvial flow and sea level rise of 600mm)


flood damages (£m)

The broadscale modelling has shown that flooding in the Adur West Branch area of the CFMP will not increase as a result of climate change.

Basecase = £0.02

Scenario = £0.02

Conclusions

The low flood damages result from the catchment being sparsely populated and predominantly rural in nature, with lower flood risks of flooding to property and consequently lower flood damages. The damage values for the current basecase and future scenario are entirely from agricultural damages.

Future flood risk to the environment – Adur West Branch


impact

None identified


Lower Adur

Figure B3.5 – Lower Adur: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2006 baseline conditions)


Current flood risk – Lower Adur (including Brighton and Hove)




Steyning, Bramber and Upper Beeding Fluvial flooding from Adur, Black Sewer and Tanyard Stream. Surface water flooding from urban and road drainage systems.

Overtopping of raised river embankments along the River Adur. Under capacity and blocked urban drainage systems. Surface water and overland flow. Properties, land and roads affected in Steyning, Bramber and Upper Beeding

The raised embankments provide some protection for the lower probability fluvial flood events, so damages are lower for the more frequent flood events. Embankments are likely to be overtopped by an exceptionally high tide or the combination of a high tide and very high river flows. 50-100 properties are at risk from the more extreme flood events in this area, which results in high flood damages to properties. The high street, connecting the towns of Upper Beeding and Bramber, is at risk of flooding during the most severe flood events. The overall hazard and disruption is assessed as low. Because of the number of properties at risk under an extreme flood event the flood risk has been assessed as low.

Shoreham and Lancing Surface water flooding from run-off generated from the steep slopes of the South Downs.

Surface water and overland flow. Properties, land and Shoreham Airport affected.

Surface water is pumped to the River Adur in times of flood, but water can take weeks to subside in extreme events. Agricultural land is worst affected, with some disruption to the airport and highways and gardens flooded. There are a very small number of properties (less than ten) affected by the surface water flooding. Surface water flooding is experienced approximately 1 in every 10 years. The flood risk has been assessed as low.

Brighton and Hove Groundwater and surface water flooding.

Intense rainfall combined with high groundwater levels causes surface water and overland flows as drainage capacity is exceeded. People, property and infrastructure in affected in Brighton and Hove.

No formal flood defences present in the area. Numerous properties are at risk from groundwater flooding. Transport routes including the A23 and railway lines are also at risk. Because of the likelihood of flooding is not certain, and the mechanisms can be rapid or slow depending on whether flooding is from surface water or groundwater the flood risk has been assessed as low to medium.


Current flood risk to the environment – Lower Adur

Flooding source Pathway and habitat affected Current flood risk and scale of impact

None identified

Figure B3.6 – Lower Adur: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2106 baseline conditions)



Lower Adur – Future scenario (climate change: 20% additional fluvial flow and sea level rise of 600mm)


flood damages (£m)

The broadscale modelling has shown an increase in flood damages in this area, which is due to the combination of sea level rise and increased flows as a result of climate change.

Basecase = £3.10

Scenario = £3.90

Conclusions

Flood damages from the River Adur are expected to increase as a result of climate change. The increase of approximately 26% (from £3.1 million up to £3.9 million) is due mainly to additional volumes of floodwater resulting in greater depths of flooding throughout the area and therefore greater flood damages to properties and agriculture. If a fluvial flood event is combined with a large coastal flooding event, these figures are expected to increase significantly. Under the future scenario, flooding of the urban areas (Steyning, Bramber and Upper Beeding) is likely to occur more frequently due to the climate change in the future. Groundwater flooding has not been included as part of our broadscale modelling and our current ability to accurately predict the impact of climate change on groundwater flooding is limited. However, we do expect an increase in high intensity storms in the future, which will make flood risk worse in Brighton and Hove.

Future flood risk to the environment – Lower Adur


impact

None identified.


Ferring Rife

Figure B3.7 – Ferring Rife: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2006 baseline conditions)

Current flood risk – Ferring Rife




Ferring Fluvial flooding from the Ferring Rife. Surface water flooding.

Under capacity river channel in the upper catchment. Overland flow. People and properties affected in Ferring.

Approximately 50 properties are at risk from the more extreme flood events in this area, which results in high flood damages to properties. The overall hazard and disruption is assessed as low. Flood risk has been assessed as low.


Current flood risk to the environment – Ferring Rife


impact

None identified.

Figure B3.8 – Ferring Rife: Broadscale model flood outline – 1% annual probability fluvial flood event (at 2106 baseline conditions)



Ferring Rife – Future scenario (climate change: 20% additional fluvial flow and sea level rise of 600mm)


flood damages (£m)

The extents of the larger flood events will not change very much and it is only the depth of flooding that will increase. The broadscale modelling has shown that damage levels within the catchment are relatively insensitive to any changes in flood flows that do occur. Tide locking due to sea level rise also lasts slightly longer, which, by reducing the ability to discharge to the sea, increases flooding on the lower parts of the Ferring Rife

Basecase = £1.65

Scenario = £1.83

Conclusions

The extent of the modelled flood risk area does not increase very much. For the 1% annual probability fluvial flood event, the flood damages increase by around 11% for the 100 year horizon. The extent of the larger flood events will not change by very much and it is only the depth of flooding that will increase.

Future flood risk to the environment – Ferring Rife


impact

None identified.


Form B3b Source-Pathway-Receptor table with objectives and suggested flood risk management responses.

Drivers Source Primary Pathway

Secondary Pathway

Receptor Aspect Indicator Catchment Objectives

Responses Examples Policy

Climate change (increased inflows)

River River channel and drainage network

Overtopping of river embankments

Population Number of people affected

Planning policy (future development)

No active intervention (including flood warning and maintenance). Continue to monitor and advise.

Climate change (sea level rise)

Surface water run-off

Sub-surface flow i.e. groundwater

Overtopping of watercourses

Population – vulnerability

Number of people affected (according to Social Vulnerability)

Flood warning and evacuation

Reduce existing flood risk management actions (accepting that flood risk will increase over time).

High tide levels in Adur estuary and along the coast

Storage for tide locking overwhelmed by catchment run-off

Overtopping of watercourses and overland flow

People

Transport

Length of transport type affected (main road, rail etc.)

Ensure the impact of flooding on people, property and the built environment does not increase due to future changes. Reduce flood risk to society where it is unacceptably high.

Flood awareness

Continue with existing or alternative actions to manage flood risk at the current level of flooding (accepting that flood risk will increase over time).

Tidal influence extending up River Adur

River channel Overtopping of river embankments

Property (residential)

Number of residential properties affected and cost of flood damage

Influencing and informing

Land use change

Take further action to sustain current scale of flood risk into the future (responding to the potential increased in flood risk from urban development, land use change and climate change).

Urban drainage systems

Structural blockages/ incapacity

Roads and fields

Property (commercial)

Number of commercial properties affected and cost of flood damage

Online storage

Take further action to reduce flood risk (now and/or in the future).

Property

Agriculture (land resource)

Area of land affected and damages to agricultural land (according to Agricultural Land Classification)

Reduce the cost of flood damages where it is unacceptably high. Support the implementation of sustainable planning policies taking due regard of flood risk.

Attenuation/ retention

Floodplain storage (wetland creation)

Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction (e.g. for habitat inundation).

Biodiversity – designated resource

Area of wetland and naturally active floodplain

Agricultural drainage

Biodiversity – species

Species diversity

Best farming practices

Biodiversity - habitats

Habitat quality

Rural land use change

Afforestation

Landscape Area of AONB and proposed National Park

River maintenance

Environment

Soil erosion

Amount of disruption caused by soil erosion

Increase water retention within the catchments where appropriate. Restore rivers and floodplains to a naturally functioning state where feasible. Enhance the biodiversity of the catchment including the support of the national and local biodiversity action plan (BAP) targets. Reduce soil erosion.

Dredging/ desilting

Increased conveyance

Removal of channel obstruction

Defences, diversion channels, flood alleviation schemes

Protection measures

River engineering

Studies

Analysis and understanding of groundwater flooding


Form B4 CFMP policy option The following generic policy options have been recommended in the CFMP guidelines for consideration. They are intended to cover the whole spectrum of potential policy choices in response to flood risk.

Option 1: No active intervention (including flood warning and maintenance); continue to monitor and advise.

Option 2: Reduce existing flood risk management actions (accepting that flood risk will increase over time).

Option 3: Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time).

Option 4: Take further action to sustain the current level of flood risk into the future (responding to the potential increased in risk from urban development, land use change and climate change).

Option 5: Take further action to reduce flood risk.

Option 6: Take action to increase the frequency of flooding to deliver benefits locally or elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation).


Policy unit 1 Upper Adur

Policy appraisal forms

Form B5 – Summary of current and future levels of and responses to flood risk.

Form B6 – Appraisal of policy options against policy unit objectives.

Form B7 – Summary of losses and gains.

Form B8 – Summary of preferred policy.

Form B9 – Requirements for further policy development and appraisal.

Form B10 – Indicators for monitoring, review and evaluation.


Form B5 Summary of current and future levels or and responses to flood risk

Policy unit 1 - Upper Adur

Current responses to flood risk within the policy unit

Defences: No major defence schemes. There are approximately 12km of raised tidal embankments on lower sections of the Adur East and Adur West Branches and some short lengths of culverted channel. In total there are approximately 25.5 km of raised defences in his policy unit. Flood warning: This unit is covered by the River Adur East Branch (north Burgess Hill to Chates Weir, Henfield) and River Adur West Branch (Coolham to Bines Green) Flood Warning Areas. There are around 20 properties connected to the flood warnings direct service. Maintenance: We maintain the sections of flood embankment to the south of the unit. We also carry out an annual maintenance programme whereby much of the river lengths in the unit are subject to annual weed clearance to allow river flow. The estimated cost of maintaining the channels and existing defences under the Environment Agency’s responsibility is approximately £80,000.

Standards of service that apply to flood defences within the policy unit

Standard of protection: The raised embankments to the lower sections of the Adur East and West Branches are considered to offer protection ranging from the 20% annual probability event (1 in 5) to the 3.3% annual probability event (1 in 30). They are considered to be at or above the target condition.

Receptors In 10% flood

outline* In 1% flood

outline* In 0.1% flood

outline*

Residential properties 2 5 N/A

Commercial properties 0 0 N/A

Population 5 12 N/A

Property damages £93,530 £0.207 million N/A

Agricultural damages £78,840 £0.126 million N/A

A roads 0.42 km 0.68 km 2.92 km

Railways 0 km 0 km 0.05 km

Agricultural land Grade 1

0 km2 0 km

2 0 km

2


0 km2 0 km

2 0.10 km

2


1.91 km2 3.06 km

2 3.61 km

2


5.57 km2 12.13 km

2 13.88 km

2


0 km2 0 km

2 0 km

2

SNCIs 0.28 km2 2.7 km

2 3.32 km

2

SSSI 0 km2 0 km

2 0 km

2

Listed Buildings 1 2 6

SM 0 0 3

AONB 0 km2 0 km

2 0.12 km

2

ESA 0 km2 0 km

2 0 km

2

Registered Historic Parks and Gardens

0km2 0km

2 0.222km

2

Proposed National Park 0.16 km2 2.96 km

2 3.15 km

2

What is currently exposed to flooding?

* 10% and 1% based on broadscale model results and 0.1% based on Flood Zone 2

Who and what are currently most vulnerable to flood damage and losses?

Economic and social receptors: Currently approximately five properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. There are a few incidents of road disruption due to surface water run-off flooding. A small number of isolated properties within the catchment may suffer from disrupted access routes. Very short sections of the A23(T), A24, A2037 and A281, a total of 0.68km, lie in the 1% annual probability flood event outline; increasing to a total length affected of approximately 3km in the more extreme flood events (Flood Zone 2).


Only moderate to low grade agricultural land (Grades 3 and 4) is at risk of localised fluvial flooding. Environmental designations: There are no internationally designated sites or SSSIs at risk of flooding within this policy unit. Total area of 2.7km

2 of the River Adur Water Meadows and Wyckham Wood

SNCI is located within the 1% annual probability flood event outline in this policy unit. The sensitivity of this site to flooding is low and may benefit from periodic flooding. Landscape: The High Weald AONB is located within this policy unit, however none of this area is located within the 1% annual probability flood event outline. The sensitivity of the site to flooding is low. Natural and Historic Environment: Significant areas of existing wet woodland are located within the 1% annual probability flood outline, however these areas would benefit from increased flooding. Two listed buildings are at risk of flooding during the 1% annual probability flood event, this increases to six within the extreme flood outline, including one parish church. There is no extent of registered historic parks and gardens located within the 1% annual probability flood outline, however, a small extent of Knepp Castle and Heaselands is located within the extreme flood outline. There are no SMs within the 1% annual probability flood event outline. This increases to three, two salterns located to the north of St. Peter’s church and Knepp Castle, within the extreme flood outline.

What are the key factors that could drive future flood risk?

Flood risk not expected to significantly increase in the future. Some increase in flood risk due to climate change (increased inflows) is predicted.

What are the possible future levels of flood risk under the main scenarios?

Very small increase (approximately £0.01 million) in AAD due to climate change. In 100 years approximately 6 properties at risk of flooding in the policy unit.

What potential responses (or groups of responses) are being considered to manage flood risk?

There is potential to reduce flood risk downstream in other policy units by providing flood storage within this policy unit and also through changes in land use by reducing run-off in the catchment. Lowering or removing flood defences could also help reduce flood risk in this and other areas. In addition there is likely to be environmental benefit to the River Adur Water Meadows and Wyckham Wood SNCI.

What gaps and uncertainties are there in knowledge, and what assumptions have been made?

There is currently some uncertainty about how effective land management and vegetation cover is in altering run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. The broadscale modelling has shown that lowering or removing flood defences can help reduce flood risk in this area. We will need more detailed studies to We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future.

The following tables provide a summary of how flooding may change in response to flood management options which may be adopted within the policy unit and what the implications of these changes might be. We have not applied any specific measures or schemes to the policy unit, but have applied what has been termed a ‘generic response’. This represents the most likely outcome of a given policy, but is not specific and does not reflect any proposed scheme or project. It simply allows a broad assessment of what the impact of that policy might be. A broadscale model has been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages. The results given below for each of the generic responses and the basecase are for the 1% annual probability flood event.


Generic response: Attenuation/retention (storage) on the Adur West Branch

Results from broadscale modelling 1% annual probability fluvial flood

damages (£m)

The broadscale modelling has indicated that applying flood storage on the Adur West Branch (of no specific size or location) has a minor positive effect on flood damages within this policy unit (approximately £0.01 million decrease in flood damages). The broadscale modelling has also shown a reduction in flood damages downstream in policy unit 3, with a 6% reduction in total flood damages from £3.71 million down to £3.48 million for the 1% annual probability fluvial flood event.

Future basecase = £0.424

Generic response = £0.415

% change = -2%

Conclusions

A large flood storage reservoir on the Adur West Branch will provide some benefit downstream by reducing flood damages. Although the benefit reduces further downstream in other policy units as the flooding becomes more dominated by the tide.

Generic response: Rural land use change – changing farming practices to reduce run-off rates


damages (£m)

The effect of reducing run-off rates through changes in land use has been applied across the whole of this policy unit within the broadscale model. The results show a small reduction in flood damages within this policy unit of approximately 3% for the 1% annual probability fluvial flood event. Reductions in flood damages are also experienced in policy unit 3 downstream, with a 6% reduction in total flood damages. The decrease in flood damages diminishes further downstream towards Shoreham and policy units 7 and 8.



% change = -3%

Conclusions

Although the impact on flood risk from changing land use in the upper catchment is not large, it is nonetheless significant, both in this policy unit, and to a slightly larger extent, on policy unit 3, Steyning and Upper Beeding. Together with other downstream measures, land use change in the upper catchment can provide a useful way of reducing flood risk.

Generic response: Reducing the height of all raised embankments along the River Adur


damages (£m)

Reducing the height of the raised embankments along the River Adur, from Shermanbury on the Adur East Branch and Bines Green on the Adur West Branch (in this policy unit) to the outfall into the sea at Shoreham, allows more frequent inundation of the floodplain on both sides of the river. This has the effect of increasing the flood extent in places, but significantly reducing the depth of water in the river channel. The broadscale modelling has shown that reducing the height of the embankments has a relatively small impact on flood damages within this policy unit. The reduction in flood damages resulting from this policy is more noticeable in policy unit 3, where the flood damages for the 1% annual probability fluvial flood event reduces by 37%.



% change = +0.2%

Conclusions

The impact of reducing the height of the embankments is complex and far reaching, with the influence experienced within several policy units. By allowing more frequent flooding of the currently protected floodplains, there is less damage caused within this policy unit by the more frequent, but less severe flood events and minimal damage caused by the more extreme events. Downstream, the effect is reversed and the flood damages are reduced for the more extreme flood events in policy unit 3 and increased for the more frequent, less severe flood event. The increased inundation of the floodplains has the effect of reducing the peak water level in the river. This allows water to drain away more effectively, lowering water levels along the River Adur.


Form B6 Appraisal of policy options against policy unit objectives

Policy unit 1 – Upper Adur

KEY = Scale of policy impact on objective: Not appraised Baseline Meets objective No impact Doesn’t meet objective Uncertain

The preferred policy option is indicated below by the policy option highlighted in pink

Baseline (current and future)

Policy 1 Policy 2 Policy 3 Policy 4 Policy 5 Policy 6


Targets and Indicators

Opportunities and constraints

Current and future baseline with current

flood risk management.

No maintenance of watercourses.

Channels become blocked with

vegetation and conveyance is

reduced.

The height of raised embankments would

reduce over time.

The flood warning service is withdrawn.

A do nothing

approach would increase the flooding in an unmanaged and

unpredictable way.

Reduction in maintenance of watercourses.

Channels become blocked with vegetation

and conveyance is reduced.

The flood warning service remains in

place.

Maintenance of the channels continues.


place.

Improved level of channel maintenance

of watercourses.

Localised protection measures introduced.

The flood warning service is improved.

Improved level of channel maintenance of watercourses with

increased conveyance on the Adur East

branch.


Improved land use management through

agri-environment schemes would

reduce surface run-off by woodland creation

to increase interception of run-off

and increase infiltration.

There is potential to

increase water retention by

introducing flood storage areas.

Economic objectives

Ensure that river channel and flood

defence maintenance expenditure is

appropriate to the agricultural economic damage in rural areas

from flooding.

Targets Maintain a suitable

balance of annual river channel and flood

defence maintenance expenditure (£) to annual average

damages from fluvial flooding to agriculture

(£).

Indicators Balance of annual river

channel and flood defence maintenance

expenditure (£) to annual average


(£).

Opportunities - Improvements in the

efficiency of channel and flood defence maintenance processes.

- To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate.

Constraints - Available funding for the

initial set up of new flood risk management schemes.

- Older flood defence structures are likely to be more costly to maintain.

- Limited available information on surface water and groundwater flood damages.

The current annual river channel and

flood defence maintenance expenditure is approximately

£80,000; the annual average damages

from fluvial flooding to agriculture are

currently around £13,700, increasing to around £18,200 in the

future. The current balance of

expenditure to damages is considered acceptable.

No river channel and flood defence maintenance expenditure is incurred as no maintenance is

undertaken. Annual average damages

from fluvial flooding to agriculture increase

to be around £23,000. The

balance of expenditure to

damages is unacceptable.

River channel and flood defence maintenance

expenditure reduces to be less than £80,000.

Annual average damages from fluvial flooding to agriculture are likely to be around £20,000. The balance

of expenditure to damages is

unacceptable.

River channel and flood defence maintenance

expenditure remains at approximately £80,000. Annual average damages

from fluvial flooding to agriculture increase over time due to the

affects of climate change to be around

£18,200. The balance of expenditure to

damages will become unacceptable over time with increased

damages.

The level of river channel and flood

defence maintenance expenditure will

increase over time to mitigate the affects of

climate change to slightly more than £80,000. Annual

average damages from fluvial flooding to

agriculture will remain around £13,700. The

balance of expenditure to damages will

become unacceptable over time with

increased expenditure.


defence maintenance expenditure will increase to be

significantly more than £80,000.

Annual average damages from fluvial flooding to agriculture are estimated to be

less than £2,000. The balance of

expenditure to damages will be

unacceptable with expenditure being unjustifiably high.


defence maintenance expenditure is likely to remain the same or be

slightly less than £80,000 as agri-

environment schemes reduce the level of

management required. Annual average

damages from fluvial flooding to agriculture are likely to be slightly

less than £13,700. The balance of expenditure to

damages will remain acceptable.

Social objectives

Ensure the impact of flooding on people

and property does not significantly increase

in the future (for example due to

climate change) in the Upper Adur.

Targets No significant increase in the number of people or properties affected by

the 1% annual probability fluvial flood event or surface water flooding in the future

Indicators

Number of people and properties affected by

the 1% annual probability fluvial flood

Opportunities - Investigate removal of

Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

Constraints - Government and

international legislation, environmental management policies, plans and strategies

Approximately 12 people and 5

properties are at risk of localised fluvial

flooding by the current 1% annual probability

flood event. This increases to around

14 and 6 in the future.

An estimated 9 properties are

currently covered by a flood warning service.

No maintenance of channels and

drainage networks would result in an

increase in the frequency, extent and

depth of localised fluvial flooding.

The number of

people and properties at risk of localise

fluvial flooding will increase to be more

It is likely that the

number of people and properties at risk of

localise fluvial flooding will increase to be

more than 14 and 6 respectively.

The current level of

Flood Warning Service remains in place.


properties are likely to be at risk of localised fluvial flooding by the

current 1% annual probability flood event


Flood Warning Service remains in

place.


properties are likely to be at risk of localised fluvial flooding by the

current 1% annual probability flood event

Coverage of Flood Warning Service is

increased, system is improved in terms of

accuracy and coverage.

Improved channel maintenance,

increased local defence works and

upgrading of the drainage network and warning service will

reduce the number of people affected by

localised fluvial flooding to less than 10 and number of

properties affected to less than 4.

The increased frequency of flooding will be managed such

that the number of properties at risk in this policy unit is not increased from the

current baseline and the

Flood Warning Service is retained at

the current level.


event

Coverage of Flood Warning Service

for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.

than 20 and 48 respectively.

Withdrawing the flood warning system may result in increased risk to human life.

Flood Warning

Service is improved in terms of accuracy

and coverage

Environmental objectives

Restore parts of the River Adur and

floodplain to a naturally functioning state where

feasible upstream of Steyning and Upper

Beeding.

Targets Increase the length of naturally functioning

river and area of naturally active

floodplain along the Rive Adur upstream of

Steyning and Upper Beeding, providing

suitable quality habitat.

Indicators Length of naturally

functioning river (km). Area of naturally active

floodplain (km2).

Opportunities - Enhance the character of the

landscape and increase amenity opportunities for recreation, tourism and leisure activities.

- Move toward more natural rivers and drainage networks, as outlined within PPS25, will mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character.

- Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

- Help meet national biodiversity action plan (BAP) targets.


international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.

- Some environmentally designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance.

- Existing urban development may prevent reinstatement of natural river processes.

- Individual homes and properties are currently at risk of flooding.

- Presence of protected species with specific water level, water quality and habitat requirements.

- Changes to flood risk management can affect the landscape, its character and value as an amenity.

- Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions.

- Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences).

- No degradation of existing fish passage and habitat.

Currently there is approximately 26km of defended watercourse

and around 4km2 of

naturally active floodplain in this policy

unit. There are opportunities now and

in the future to enhance the floodplain

connectivity along defended parts of the

River Adur, for example by restoring it

back to its original state or removing

raised embankments.

With current flood risk management in the future the length of

naturally functioning river and naturally

active floodplain may slightly increase over

time.

No maintenance and reduction in the

height of embankments would allow the channel and floodplain to function more naturally and restore the natural

river processes (i.e. erosion and deposition).

However, this would occur in an

unmanaged and unpredictable way.

The length of

naturally functioning river is likely to

increase by around 26km and the area of

naturally active floodplain to

approximately 12km2.

A reduction in maintenance would

allow the channel and floodplain to function more naturally and

restore the natural river processes (i.e. erosion

and deposition). However, this would

occur in an unmanaged and unpredictable way.

The length of naturally

functioning river is likely to increase by

around 10km and the area of naturally active

floodplain to around 7km

2.

It is not expected that the river processes or floodplain connectivity

will significantly change under this

policy option.

The length of naturally functioning river may slightly increase over time from the current extent and the area of

naturally active floodplain to slightly

more than 4km2.

There is unlikely to be any significant

alterations to the river processes and

floodplain connectivity under this policy

option.

The length of naturally functioning river is

likely to remain at the current extent and the area of naturally active

floodplain is likely to remain at around 4km

2.

Increasing conveyance on the Adur East branch is likely to reduce the

natural river processes and

floodplain connectivity.

The length of


decrease from the current extent and

the area of naturally active floodplain will be less than 4km

2.

Restoring the rivers to a naturally functioning state and increasing

floodplain connectivity could be achieved through this policy option and provide

flood storage.

The length of naturally functioning river is

likely to increase by up to 26km and the

area of naturally active floodplain to up to

12km2.

This would be achieved in a managed and controlled way.


Protect and enhance the River Adur Water

Meadows and Wyckham Wood Site of Nature

Conservation Importance.

Targets Protect and enhance the

River Adur Water Meadows and Wyckham

Wood Site of Nature Conservation Importance.

Indicators

Habitat quality and species diversity.

Opportunities - Help meet national

biodiversity action plan (BAP) targets.


Constraints - Some environmentally

designated habitats are susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance.


There is currently 2.7 km

2 of the SNCI

located within the 1% annual probability

flood event outline.

This is likely to increase to around 3

km2 in the future,

however, there will be no notable increase in

habitat and species diversity with such a

minor increase.

Doing nothing and removing

embankments would allow the rivers to

flood more frequently and increase the

flood depths, increasing the area of the SNCI within the

1% annual probability flood outline to

significantly more than 3 km

2.

There is increased

potential to significantly improve

or increase the habitat types and species diversity within the SNCI.


unmanaged and uncontrolled way.

Reducing the maintenance of the

channels would eventually allow the rivers to flood more

frequently and increase the flood depths,

increasing the area of the SNCI within the 1% annual probability flood outline to more than 3

km2.

There is increased

potential to improve or increase the habitat types and species diversity within the

SNCI. However, this would occur in an unmanaged way.

There would be a slight increase to

approximately 3 km2

in the area of the SNCI within the 1% annual probability

flood event outline due to the affects of climate change.

However, as the

increase is small there will be no notable

increase in habitat and species diversity.

The extent of the SNCI within the 1% annual probability flood event outline will remain at

approximately 2.7 km2.

There will be no

notable change in the habitat and species diversity within the

SNCI.

Increasing conveyance on the Adur East branch is likely to reduce the

extent of flooding and therefore the extent

of the SNCI within the 1% annual probability flood outline to less

than 2.7 km2.

Decrease in flooding extent (duration and

depth) will reduce the potential of

increasing habitat types and species diversity within the

SNCI.

Increasing the flood storage areas in this

policy unit would improve the potential

to increase the area of SNCI to more than 3 km

2 and improve or

increase the habitat types and species

diversity in a managed and controlled way.


Increase the landscape character value of the

High Weald AONB and proposed South Downs

National Park.

Targets Increase the landscape character value of the

High Weald AONB and South Downs proposed

National Park.

Indicators Landscape character

assessment of the AONB and proposed

National Park.



- Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character.





Currently none of the High Weald AONB is located within the 1%

annual probability flood event outline.

This remains the case in the future.

Approximately 2.9km

2

of the South Downs proposed National

Park is located within the current 1% annual probability flood event

outline. This increases over time to approximately 3.1km

2

in the future.

The landscape character of the South

Downs proposed National Park is

unlikely to notable alter.

The area of the South Downs proposed

National Park located within the 1% annual

probability flood event outline

increases to be significantly more

than 3.1km2.

The landscape character of the South Downs

proposed National Park is likely to alter

in a beneficial manner, however, it

will occur in an unmanaged and un

controlled way.


National Park located within the 1% annual probability flood event outline increases to be

more than 3.1km2.

The landscape

character of the South Downs proposed

National Park is likely to alter in a beneficial

manner, however, it will occur in an unmanaged

way.


National Park located within the 1% annual probability flood event outline increases over

time to at around 3.1km

2.

There would be no

notable impact on the landscape character of the High Weald AONB or South

Downs proposed National Park in this

policy unit.


National Park located within the 1% annual probability flood event

outline remains at around 2.9km

2.

There would be no

impact on the landscape character of the High Weald AONB

or South Downs proposed National Park

in this policy unit.




decreases to be minimal.

A decrease in

flooding extent, depth and frequency is likely to have a

negative impact on the landscape

character of the South Downs

proposed National Park

The landscape character of the South

Downs proposed National Park would

be enhanced with the implementation of

considered flood risk management

practices.

Does this policy change flood risk locally or elsewhere:

Impact uncertain - Reduction in

conveyance may benefit downstream

areas



areas

Risk downstream will increase due to

climate change

Risk downstream may increase due to

improved conveyance


improved conveyance

Reduction in conveyance and

increased storage will benefit

downstream areas



Policy unit name/number:

Policy Unit 1 - Upper Adur

Policy options Losses Gains Preferred policy option relative to current baseline

Policy option P1

Environmental

Social

Economic

NO LOSSES

Medium -

� The number of people and property at risk significantly increases and the withdrawal of flood warning services further increases flood risk

HIGH-

� The balance of FRM expenditure to AAD compared to other policy options is unacceptable with AAD to agricultural land increasing by approximately £9,300

MEDIUM+

� The length of naturally functioning river and area of naturally active floodplain along the upper River Adur will increase by approximately 26km and 8km

2 respectively

but in an unmanaged and unpredictable way

� The area of the River Adur Meadows and Wyckham Wood SNCI will significantly increase by more than 0.3km

2 but in an

unmanaged and uncontrolled way

� The landscape value of the South Downs proposed National Park is likely to be beneficially altered but in an unmanaged and uncontrolled way

NO GAINS

NO GAINS

Not preferred option – Although the benefits to the environment are potentially high, alterations to natural habitats, biodiversity, river and floodplain functions and landscape will be unmanaged and uncontrolled and therefore unpredictable. In addition to this, the AAD to agricultural land resulting from this policy will be unacceptably high.

Policy option P2


Environmental

Social

Economic

NO LOSSES

LOW-

� The number of people and property at risk significantly increases and flood warning services is only maintained at its current level

HIGH-

� The balance of FRM expenditure to AAD is unacceptable compared to other policy options with AAD to agricultural land increasing by approximately £6,300

MEDIUM+


2 respectively

but in an unmanaged way

� The area of the River Adur Meadows and Wyckham Wood SNCI will increase by more than 0.3km

2 but in an

unmanaged way � The landscape value of the South Downs proposed National Park is likely to be beneficially altered but in an unmanaged way

NO GAINS

NO GAINS

Not preferred option – Although the benefits to the environment are potentially relatively high, alterations to natural habitats, biodiversity, river and floodplain functions and landscape will be unmanaged and therefore unpredictable. In addition to this, the AAD to agricultural land resulting from this policy will be unacceptably high.

Policy option P3

Environmental

NO LOSSES

LOW+

� The length of naturally functioning river and area of naturally active floodplain along the upper River Adur will be slightly increased

� The area of the River Adur Meadows and Wyckham Wood SNCI will slightly increase but with no notable increase in biodiversity

� The area of the South Downs proposed National Park that falls

Not preferred option – The potential benefits in terms of the environment are not sufficiently optimised under this policy. In addition to this, the AAD to agricultural land will increase significantly in the future.


Social

Economic

LOW-

� The number of people and property at risk significantly increases and flood warning services is only maintained at its current level

HIGH-

� The balance of FRM expenditure to AAD will become unacceptable compared to other policy options in the future with AAD increasing by approximately £4,500

within the 1% AEP will increase slightly but with no notable increase in landscape value

NO GAINS

NO GAINS

Policy option P4

Environmental

Social

Economic

LOW-

� The length of naturally functioning river and area of naturally active floodplain along the upper River Adur will remain the same

� The area of the South Downs proposed NP that falls within the 1% AEP remain the same with no increase in landscape value

NO LOSSES

MEDIUM-

� The balance of FRM expenditure to AAD will become unacceptable in the future with necessary increases in FRM expenditure to keep AAD to agricultural land constant

LOW+

� The area of the River Adur Meadows and Wyckham Wood SNCI will remain the same with no increases in biodiversity

LOW+

� The number of people and property at risk does not significantly increase and flood warning services are improved

NO GAINS

Not preferred option – Although AAD to agricultural land will not increase in the future, opportunities to bring benefits to the environment are not sufficiently optimised under this policy and there are also potential losses in terms of landscape value and floodplain function.


Policy option P5

Environmental

Social

Economic

MEDIUM-

� The length of naturally functioning river and area of naturally active floodplain along the upper River Adur will be slightly decreased

� The area of the River Adur Meadows and Wyckham Wood SNCI will be decreased

� The area of the South Downs proposed NP that falls within the 1% AEP will be decreased which will impact negatively on the landscape value

NO LOSSES

MEDIUM-

� The balance of FRM expenditure to AAD will become unacceptable in the future with necessary increases in FRM expenditure to reduce AAD to agricultural land

NO GAINS

LOW+

� The number of people and property at risk does not significantly increase and flood warning services are improved

NO GAINS

Not preferred option – There are no gains under this policy option. FRM expenditure is unacceptably high and there will be significant negative impacts on the environment.

Policy option P6

Environmental

NO LOSSES

HIGH+


2 respectively,

in a managed and controlled way

� The area of the River Adur Meadows and Wyckham Wood SNCI will significantly increase by more than 0.3km

2 but in a

managed and controlled way

Preferred Policy Option – There are no losses under this policy option. The potential benefits to the environment in terms of natural habitat, biodiversity, river and floodplain function and landscape value are maximised and will be carried out in a managed and controlled way which will in turn optimise the balance between FRM and AAD to agricultural land. Encouraging increased uptake of agri-environment schemes


Social

Economic

NO LOSSES

NO LOSSES

� The landscape value of the South Downs proposed National Park will be enhanced in a managed and controlled way

LOW+

� The number of people and property at risk does not significantly increase and flood warning services are maintained

HIGH+ � The balance of FRM expenditure to AAD will remain acceptable with reductions in FRM expenditure and AAD to agricultural land due to agri-environment schemes and targeted FRM

will further reduce the AAD to land. Implementing policy option 6 in this part of the catchment will also bring strategic benefits to policy units downstream through increased floodwater storage.

Key

HIGH:

High negative A policy has a ‘high negative’ effect where it could contribute to a social, economic or environmental objective in a significantly negative way. A ‘high negative’ effect could be: (i) a very large increase in current flood risk; (ii) very large projected increases in flood risk under future conditions, and/or; (iii) significant additional social, economic and/or environmental losses.

MEDIUM:

Medium negative A policy has a ‘medium negative’ effect where it could contribute to a social, economic or environmental objective in a negative way. A ‘medium negative’ effect could be: (i) an increase in current flood risk; (ii) a projected increase in flood risk under future conditions, and/or; (iii) social, economic and/or environmental losses.

LOW:

Low negative A policy has a ‘low negative’ effect where it could make a limited contribution to a social, economic or environment objective, but where the overall contribution would be negative. A ‘low negative’ effect could be: (i) an overall increase in current flood risk; (ii) an overall increase in flood risk under future conditions, and/or; (iii) overall social, economic and/or environmental losses.

NEUTRAL: Neutral A policy has a ‘neutral’ effect where it makes neither a positive or negative contribution to a social, economic or environmental objective. A ‘neutral’ effect could be: (i) no change in current level of risk. In this instance the current level of risk would have to be low, so that the residual risk after a neutral policy was implemented remained acceptable; (ii) no change in flood risk under future conditions. In this instance projected


future risk would need to be low so that the residual risk after a neutral policy was implemented remained acceptable, and/or; (iii) no additional social, economic and/or environmental gains or losses. Policy options may also be ‘neutral’ where they are not relevant in a particular policy unit, or where it is not feasible for a policy option to contribute to an objective.

HIGH:

High positive A policy has a ‘high positive’ effect where it could contribute to a social, economic or environmental objective in a significantly positive way. A ‘high positive’ effect could be: (i) a very large reduction in current flood risk; (ii) avoiding/reducing very large projected increases in flood risk under future conditions, and/or; (iii) significant additional social, economic and/or environmental gains.

MEDIUM:

Medium positive A policy has a ‘medium positive’ effect where it could contribute to a social, economic or environmental objective in a positive way. A ‘medium positive’ effect could be: (i) a reduction in current flood risk; (ii) avoiding/reducing projected increases in flood risk under future conditions, and/or; (iii) additional social, economic and/or environmental gains.

LOW:

Low positive A policy has a ‘low positive’ effect where it could make a limited contribution to a social, economic or environment objective, but where the overall contribution would be positive. A ‘low positive’ effect could be: (i) an overall reduction in current flood risk; (ii) an overall avoidance/reduction in flood risk under future conditions,


Form B8 Summary of preferred policy


Physical characteristics: - Largely rural landscape in the north of the CFMP area, of moderate agricultural

quality with a few villages and isolated properties. - Weald Clay Formation geology set predominantly in the Low Weald Landscape

Character Area, with poorly draining clay soils, which may result in rapid run-off from the land.

- The north-east section (High Weald AONB) has varied topography, and this region and the southern boundary of the unit overlie sandstone geology.

- The East and West Adur confluence lies west of Henfield village amongst gently sloping land, which results in slow run-off from the land.

- The Adur West Branch headwaters emerge north of Coolham. - The northern section of the proposed South Downs National Park designation is

present in the far south of the unit. - Flood defences extend to Bines Green on the Adur West Branch and Shermanbury

on the Adur East Branch. Flood mechanism:

- Low fluvial flood risk (some localised areas of fluvial flooding). - Adur West Branch slower response to run-off rates than the Adur East Branch.

Receptor: - Mainly moderate grade Agricultural Land (Grades 3 and 4) at risk of localised fluvial

flooding. - Limited environmental and landscape designations – only High Weald AONB (which

is outside of floodplain) and the proposed South Downs National Park. - Significant areas of existing wet woodland, which would benefit or be increased in

area through increased flooding. - Small number of isolated properties within the River Adur floodplain. - Currently approximately 5 properties at risk of fluvial flooding in the policy unit from

the 1% annual probability fluvial flood event. - In 100 years approximately 6 properties at risk of flooding in the policy unit.

Current Flood Risk Summary

Number of properties at risk of flooding (1% annual probability flood event) 5

Total damages (approx.) (1% annual probability flood event) £0.333 million

Annual average damages (approx.) £38,000 Future Flood risk:

- An increase in the severity of flooding does not significantly increase the risk of flooding or significantly increase the economic damages.

- Flood risk is currently assessed as low, assessment remains low in the future. Future Flood Risk Summary (in 100 years time)



Problem/risk

Annual average damages (approx.) £49,000

Policy selected Policy 6 - Take action to increase the frequency of flooding to deliver benefits locally or elsewhere, which may constitute an overall flood risk reduction (for example for habitat inundation).

Justification

This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding locally in this unit or at least keeping water in the catchment for longer, flooding downstream can be reduced, and in many instances, increasing flooding can improve wetland biodiversity, as flooding is an essential part of floodplain ecosystems. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal cutting back overhanging branches. Policy 6 sets a framework that actively supports increased flooding, or keeping water on the land for longer. This applies to this policy unit for the following reasons:

- An increase in flooding or retaining flood water for longer in this unit, reduces flood risk to properties in Steyning, Upper Beeding and Shoreham 100 years in the future.

- An increase in flooding or retaining flood water for longer in this unit, reduces economic damages, from a 1% annual probability fluvial flood event 100 years in the future in Steyning and Upper Beeding, by approximately 6%.

- An increase in flooding or retaining flood water for longer in this unit, also reduces economic damages, from a 1% annual probability fluvial flood event 100 years in the future locally in this policy unit, by approximately 3%.

- An increase in flooding could result in an increase of approximately 1300 hectares of


wetland around the River Adur Water Meadow and Wyckham Wood SNCI. This will improve local biodiversity and help meet biodiversity action plan targets.

- There are relatively few constraints in this policy unit, such as environmental or landscape designations which would restrict options to increase flooding locally.


- Ensure that river channel and flood defence maintenance expenditure is appropriate to the agricultural economic damage in rural areas from flooding.

- Restore parts of the River Adur and floodplain to a naturally functioning state where feasible upstream of Steyning and Upper Beeding.

- Protect and enhance the River Adur Water Meadows and Wyckham Wood Site of Nature Conservation Importance.

- Increase the landscape character value of the High Weald AONB and proposed South Downs National Park.

Catchment-wide opportunities and constraints

Opportunities: - Improvements in the efficiency of channel and flood defence maintenance processes. - To work with Defra and farmers to produce soil management plans which have a benefit

to flood risk through reducing the run-off rate. - Enhance the character of the landscape and increase amenity opportunities for

recreation, tourism and leisure activities. - Move towards more natural rivers and drainage networks, as outlined within PPS25, will

mean we can achieve more efficient and sustainable water management, whilst enhancing landscape character.


- Help meet national biodiversity action plan (BAP) targets. - Work with the High Weald AONB Joint Advisory Committee to achieve the targets set in

the High Weald AONB Management Plan to maximise the opportunities for natural processes to reduce flooding through the adoption of river restoration policies, whilst enhancing landscape character.

Constraints: - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Government and international legislation, environmental management policies, plans and

strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.


- Existing urban development may prevent reinstatement of natural river processes. - Individual homes and properties are currently at risk of flooding. - Presence of protected species with specific water level, water quality and habitat

requirements. - Changes to flood risk management can affect the landscape, its character and value as

an amenity. - Historic development and some heritage designations in Steyning, Bramber and Upper

Beeding present permanent physical obstructions. - Location of electricity pylons adjacent to the Lower River Adur (currently protected by

existing defences). - No degradation of existing fish passage and habitat.

Alternative policies considered

Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, the effects would happen in an unmanaged and unpredictable way, and local flood risk may increase. Policy 2 - reduce current level of flood risk management. This could also be considered a possible policy option for this area, and it could allow increased floodplain inundation whilst controlling the changes that would happen in time. This policy would not provide the benefits of reducing flood risk downstream or the benefits of increasing biodiversity that would occur through a managed approach to increasing flooding through policy 6. Policy 3 - maintain current level of flood risk management. This option results in the least favourable result, with moderate increases in damages locally of approximately 30% but with none of the benefits that would come from a managed approach of potentially increasing areas of wetland and therefore improving local biodiversity and help meet biodiversity action plan targets.


Policy 4 - maintain the current level of flood risk into the future. This policy could apply to this policy unit, but it implies a need for increased flood risk management in the future and does not consider the opportunity for large potential reduction in flood risk elsewhere. Although there is a 30% increase in flood risk in the future the assessment of flood risk remains low, with approximately 6 properties at risk under future scenarios. Policy 5 - reduce the level of flood risk, both now and in the future. As the current and future flood risk in this unit is low, there is no justification for investing in flood defences to reduce flood risk.

Uncertainties and dependencies

There is currently some uncertainty about how effective land management and vegetation cover is in altering run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. The broadscale modelling has shown that lowering or removing flood defences can help reduce flood risk in this area. We will need more detailed studies to find out if it is practical to do this and improve the environment at the same time.


Form B9 Requirements for further policy development and appraisal


Is there a need for further policy development? No

If yes, then mark policy options for more detailed development. Some complex policies may require more detailed development, probably at Strategy Plan level.

Is there a need for further more detailed appraisal? Yes

If yes, take forward to strategy study.


Form B10 Indicators for monitoring, review and evaluation

This form sets out the indicators that need to be included in the policy implementation plan, for policy monitoring, drawing on the residual risks and likely impacts identified above. This will allow better review and evaluation of the policy when implemented.

Policy unit 1 – Upper Adur

Indicators to be included in policy unit 1 implementation plan are: Economic - Balance of annual river channel and flood defence maintenance expenditure (£) to annual average

damages from fluvial flooding to agriculture (£). - Flood damages downstream in policy unit 3 (Steyning and Upper Beeding) (£AAD). Social - Number of people affected by the 1% annual probability flood event downstream in policy unit 3

(Steyning and Upper Beeding). Environmental - Length of naturally functioning river (km). - Area of naturally functioning floodplain (km

2).

- Habitat quality and species diversity. - Landscape character assessment of the AONB and proposed National Park.


Policy unit 2 Burgess Hill










Policy unit 2 – Burgess Hill


Defences: There are no formal raised defences within this policy unit. Flood risk management activity consists of carrying out channel maintenance programme; completing annual weed cuts and desilting structures when necessary. Flood warning: This policy unit contains the upper section of the Adur East Branch Flood Warning Area. There is a lead time of 2 hours, but there is a flashy response to heavy rainfall due to upper catchment topography and urban areas. There are no properties connected to the flood warnings direct service. Maintenance: The most upstream reach is inspected every 24 months. There is a significant build up of gravel in the channel at Hag Bridge, this is removed in order to provide more accurate flood warning. The estimated current annual cost of maintaining the channels and structures under the Environment Agency’s responsibility is approximately £50,000.


Standard of protection: There is no formal standard of protection from fluvial flooding as there are no formal raised defences.




outline* Residential properties 2 12 539 Commercial properties 0 1 40 Population 5 30 1290 Property damages 0 £0.109 million N/A Agricultural damages £560 £1,900 N/A A roads 0.02 km 0.04 km 0.4 km Railways 0 km 0 km 0.26 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2

Agricultural land Grade 2 0 km2 0 km

2 0 km

2

Agricultural land Grade 3 0.01 km2 0.05 km

2 0.77 km

2


2 0.34 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0.04 km

2

SSSI 0 km2 0 km

2 0.001 km

2

Listed Buildings 0 0 2 SM 0 0 0 AONB 0 km

2 0 km

2 0.01 km

2

ESA 0 km2 0 km

2 0 km

2


0 km2 0 km

2 0 km

2

Proposed National Park 0 km2 0 km

2 0.004 km

2




Economic and social receptors: Currently approximately 13 properties and 30 people at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. Significantly more properties are at risk from surface water and localised urban flooding. A small area of industrial estate and agricultural land in Burgess Hill and Hassocks. Only moderate to low grade agricultural land (Grades 3 and 4) is at risk of localised fluvial flooding. Some local minor roads are at risk of flooding during the 1% annual probability flood event. Environmental designations: There are no internationally or nationally designated sites or SSSIs at risk of flooding for the 1% annual probability flood event within this policy unit. There is a very small area, less than 0.005km

2, of the Bedelands SNCI located

within the 1% annual probability flood event outline in this policy unit. The sensitivity of this site to flooding is low and may benefit from periodic flooding.


Landscape: The proposed South Downs National Park is located within this policy unit, however none of this area is located within the 1% annual probability flood event outline. The Sussex Downs AONB bounds the southern border of this policy unit. Natural and Historic Environment: There are no listed buildings located within the1% annual probability flood outline; this increases to two within the extreme flood event outline, including one Baptist Chapel. There are no registered historic parks and gardens or SMs located in this policy unit. Areas of wet woodland within this policy unit benefit from periodic flood events.


Climate change (increased rainfall) and pressures for further urban development.


Annual average damages will more than double due to climate change. In 100 years approximately 250 properties are at risk of flooding in the policy unit from the 1% annual probability fluvial flood event. The scale of disruption is expected to increase slightly, and there is an increased probability of local minor roads flooding as a result of surface water flooding and/or urban drainage flooding causing localised flooding in areas of Burgess Hill and Hassocks.


There is potential to limit increased run-off from new development by installation of SuDS. There is also potential to provide integrated urban drainage solutions to reduced urban flooding. The prevention of vulnerable development in flood risk areas.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

The main sources of flooding for this policy unit are surface water, urban drainage and insufficient capacity of small streams. We have not been able to model these processes. However, we have been able to model the river process and the following tables provide a summary of how flooding may change in response to flood management options for fluvial flooding, which may be adopted within the policy unit and what the implications of these changes might be. We have not applied any specific measures or schemes to the policy unit, but have applied what has been termed a ‘generic response’. This represents the most likely outcome of a given policy, but is not specific and does not reflect any proposed scheme or project. It simply allows a broad assessment of what the impact of that policy might be. A broadscale model has been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages. The results given below for each of the generic responses and the basecase are for the 1% annual probability flood event.


Generic response: Increasing conveyance on the Adur East Branch


damages (£m)

The broadscale modelling has indicated that by increasing conveyance in the whole of the Adur East Branch, the extent of local flooding can be reduced quite significantly. There is a 77% reduction in the 1% annual probability fluvial flood event damages. Annual average damages can also be reduced by 77%.



% change = -77%

Conclusions

Although in practice it is quite difficult to achieve, improving the flow through the Adur East Branch, by whatever means, has been shown to reduce flood risk from fluvial flooding in Burgess Hill and Hassocks.



damages (£m)

The effect of reducing run-off rates through changes in land use has been applied across the upper catchments of the River Adur. The results show a significant reduction in flood damages within this policy unit of 62% for the 1% annual probability fluvial flood event and a 67% reduction in the average annual damages.



% change = -62%

Conclusions

The reduction in run-off rates by changes in farming practices has shown a significant reduction in flood damages in this policy unit. However, flooding in this policy unit occurs from a number of processes so in practice the reduction in flood damages is unlikely to be as significant as the modelling has suggested, but together with other measures, land use change in the upper catchment can provide a useful way of reducing flood risk.




KEY = Scale of policy impact on objective: Not appraised Baseline Meets objective No impact Doesn’t meet objective Uncertain






Opportunities and constraints






reduced.


No maintenance undertaken on

surface water and urban drainage

networks.

A do nothing approach would

increase the flooding in an unmanaged and unpredictable

way.




reduced.


place.

Reduced level of maintenance of the surface water and

urban drainage networks.



place.

Maintenance of the surface water and urban

drainage networks continue.


of watercourses.



Improvements to the


networks.


of watercourses.


Increase the local

defence works.

Upgrade of surface water and urban

drainage networks to increase capacity and

meet design standards for the

future.

Not considered feasible in this policy

unit.

Economic objectives

Ensure flood damages do not significantly

increase in Burgess Hill and Hassocks due to future change (urban

development and climate change).

Targets No significant increase in damages in Burgess Hill and Hassocks from

fluvial, surface water and urban drainage

flooding due to future changes (urban


Indicators

Total annual average damages (to properties and agriculture) from

fluvial flooding (£AAD).

Estimated* damages resulting from surface

water flooding (£).

*Estimation based on historical damages observed in the

Brighton area from the 2000/ 2001 flood event (Binnie Black

& Veatch 2001 – Flood Defence Assessment of

Downland Flooding).

Opportunities - Provide development control

advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Burgess Hill).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Burgess Hill.

- Potential for improving the current defences, for example possible installation of demountable or temporary defences in Shoreham and Burgess Hill.



- Steep catchments of the South Downs result in rapid run-off and quick responses to rainfall events.

The current total annual average

damages from fluvial flooding and

estimated damages resulting from surface

water flooding are approximately £4,300 and less than £60,000

respectively.

This increases to around £80,000 for

total annual average damages from fluvial flooding and between

£60,000 and £120,000 for

estimated surface water damages in the

future.


drainage networks would lead to a

significant increase in flooding with total annual average


estimated damages resulting from surface water flooding being

significantly more than £150,000 and

more than £200,000 respectively.

As channels and drainage networks

decrease in capacity and condition due to

reduced maintenance the total annual

average damages from fluvial flooding and estimated damages

resulting from surface water flooding will

increase to be more than £120,000 and


The total annual average damages from

fluvial flooding and estimated damages


increase over time due to the affects of climate

change to be around £80,000 and between £60,000 and £120,000

respectively.

Improved channel maintenance, drainage networks and localised protection measures

will mitigate the affects of climate change. The

total annual average damages from fluvial

flooding and estimated damages resulting from surface water flooding

will remain at approximately £4,300

and less than £60,000.



upgrading of the drainage network would reduce total

annual average damages from fluvial

flooding and the estimated damages

resulting from surface water flooding to be

minimal.

Not applicable.




appropriate to the property economic

damage in urban areas from flooding.




damages from fluvial flooding to property (£).

Indicators

Balance of annual river channel and flood





- Effective and efficient use of developer contributions for flood risk management.





The current annual channel and flood

defence maintenance expenditure is approximately


from fluvial flooding to property are currently around £4,000, and are likely to increase to more than £80,000

in the future.

The current balance of expenditure to

damages is considered acceptable.

No channel and flood defence maintenance

expenditure is incurred as no maintenance is


from fluvial flooding to property increase

to be more than £150,000. The

balance of expenditure to


Channel and flood defence maintenance


Annual average damages from fluvial

flooding to property are likely to be more than

£120,000. The balance of expenditure

to damages is unacceptable.


expenditure remains at approximately £50,000.

Annual average damages from fluvial flooding to property

increase over time due to the affects of climate change to be more than £80,000. The balance

of expenditure to damages will become

unacceptable over time.

The level of channel and flood defence

maintenance expenditure will




property will remain around £4,000. With better maintenance

efficiency and effective use of funding the

balance of expenditure to damages will remain

acceptable.


maintenance expenditure will increase to be


Annual average damages from fluvial flooding to property are estimated to be

less than £1,000. The balance of

expenditure to damages will be

unacceptable with expenditure being unjustifiably high.

Not applicable.

Social objectives

Ensure the impact of flooding on people and

property does not significantly increase in

Burgess Hill and Hassocks in the future.


the 1% annual probability fluvial flood event or surface water flooding in Burgess Hill

and Hassocks in the future.

Indicators



event.

The estimated* number of properties affected by surface water flooding.

*Surface water/ urban

drainage flooding estimates based on historical records.




- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Burgess Hill.

- Continued practice and development of the Emergency Response Plan in Burgess Hill.






flood event. This increases to around 597 and 250 in the

future.

An estimated 30 properties are at risk of surface water and

urban drainage flooding. This is likely

to increase to between 30 and 60

properties in the future.

Approximately 9 properties are

currently covered by the Flood Warning

Service.




depth of localised fluvial and surface water and urban

drainage flooding.

The number of people and

properties at risk of localise fluvial

flooding will increase to be more than 750 and 325 respectively.

The estimated

number of properties at risk of surface water and urban

drainage flooding is likely to increase to

more than 100.


Reduction in maintenance of

channels and drainage networks would result in an increase in the

frequency, extent and depth of localised fluvial and surface water and urban

drainage flooding.

It is likely that the number of people and

properties at risk of localise fluvial flooding

will increase to be more than 625 and 262

respectively.

The estimated number of properties at risk of


flooding is likely to increase to more than

75.

The current level of Flood Warning Service

remains in place.

Maintenance of channels and drainage networks continues at

the current level.

The number of people and properties at risk of localised fluvial flooding is likely to increase to

approximately 597 and 250 respectively.


surface water and urban drainage flooding is likely to increase to between 30 and 60.




will mitigate the affects of climate change. The number of people and properties affected by

localised fluvial flooding will remain at approximately 30 and

13 respectively.



flooding will remain at around 30.







reduce the number of people affected by

localised fluvial flooding to less than

5 and number of properties affected to

less than 2.

No properties will be at risk of surface water and urban

drainage flooding.

Flood Warning Service is improved in terms of accuracy

and coverage.

Not applicable.

Ensure the disruption caused by flooding to transport and critical

infrastructure does not increase in Burgess Hill

and Hassocks in the future.

Targets No increase in flooding of A roads and railway

line or increase in extent of critical infrastructure flooded, in Burgess Hill and Hassocks, from a 1% annual probability fluvial flood event or

surface water flooding.

Indicators Length of A road and

railway line (km)




Constraints - Steep catchments of the

South Downs result in rapid run-off and quick responses to rainfall events.

Currently approximately 0.04km of A road, no extent of railway and no critical infrastructure sites are

affected by the 1% annual probability

flood event. This is not expected to

increase significantly in the future.

There are no records

of A roads, railway





drainage flooding.

More than 0.5km of A road and some

lengths of railway



frequency, extent and depth of localised fluvial and surface water and urban

drainage flooding.

More than 0.1km of A road and some lengths of railway and critical

Maintenance of channels and drainage networks continues at

the current level. There may be a slight increase in extent of A

roads (slightly more then 0.04km) and railway or

critical infrastructure sites affected by

flooding during the 1% annual probability flood

event.


will mitigate the affects of climate change.

Approximately 0.04km of A road and no extent

of railway or critical infrastructure sites are

affected by flooding during the 1% annual

probability flood event.



upgrading of the drainage network will

reduce fluvial and surface water and

urban drainage flooding.

No extent of A road,

railway or critical infrastructure sites

Not applicable.


affected by the 1% annual probability fluvial

flood event.

Number of critical infrastructure sites affected by the 1%

annual probability fluvial flood event.

Number and period of recorded A road and

railway closures due to surface water flooding*.

Number of critical infrastructure sites recorded as being affected by surface

water flooding*.

*Surface water/ urban drainage flooding estimates based on

historical records.

- Transport links in the catchment are a vital part of the communication network regionally, nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032.

and critical infrastructure site being affected by surface water or urban drainage

flooding, however, surface water and

urban drainage flooding is a known problem in this area

and it is likely to increase in the future.

and critical infrastructure sites

are likely to be at risk of flooding from

fluvial flooding during the 1% annual


Significantly more surface water and

urban drainage flooding of A roads, railway and critical infrastructure sites

will occur.

infrastructure are likely to be at risk of flooding

from fluvial flooding during the 1% annual


More surface water and urban drainage flooding of A roads, railway and critical

infrastructure sites will occur.

There is likely to be a gradual increase from the current extent of A

roads, railway and critical infrastructure at

risk of surface water and urban drainage flooding

due to the affects of climate change.

There will be no change from the current extent of


flooding to A roads, railways and critical infrastructure sites.

will be affected by fluvial or surface water and urban

drainage flooding.

Environmental objectives There are no

environmental objectives applicable to

this policy unit.

There are no environmental

objectives applicable to this policy unit.



















conveyance may benefit

downstream areas



areas

Risk downstream will increase due to climate change

Risk downstream may increase due to

improved conveyance

Risk downstream may increase due

to improved conveyance

NA





Policy Unit 2 - Burgess Hill


Policy option P1

Environmental

Social

Economic

NO LOSSES

HIGH-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by more than 750 and 312 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase by more than 70

� Withdrawing the flood warning system will increase risk to human life

� The length of A road at risk from a 1% AEP flood event will increase by more than 0.46km

� The length of railways and the number of critical infrastructure at risk from a 1% AEP flood event will increase

� Significantly more surface water and urban drainage flooding to critical infrastructure and transport routes will occur

HIGH-

� The AAD and economic damages caused by flooding will increase by more than £146,000 and £140,000 respectively

� The balance of FRM expenditure to AAD is unacceptable with AAD

NO GAINS

NO GAINS

NO GAINS

Not preferred option – There are no gains under this policy option. The numbers of people and properties adversely affected by removing FRM are unacceptably high. This option is therefore not feasible.


to property increasing by more than £146,000

Policy option P2

Environmental

Social

Economic

NO LOSSES

HIGH-




� The length of railways and the number of critical infrastructure at risk from a 1% AEP flood event will increase

� Significantly more surface water and urban drainage flooding to critical infrastructure and transport routes will occur

HIGH-

� The AAD and economic damages caused by flooding will increase by more than £121,000and £90,000 respectively

� The balance of FRM expenditure to AAD is unacceptable with AAD to property increasing by more than £121,000

NO GAINS

NO GAINS

NO GAINS

Not preferred option – There are no gains under this policy option. The numbers of people and properties adversely affected by removing FRM are unacceptably high. This option is therefore not feasible.

Policy option P3

Environmental

Social

NO LOSSES

MEDIUM-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by

NO GAINS

NO GAINS

Not preferred option – There are no gains under this policy option. The numbers of people and properties adversely affected by removing FRM will become unacceptably high in the future. This option is therefore not


Economic

approximately 567 and 237 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase by up to 30

� The length of A road at risk from a 1% AEP flood event will increase slightly

� The length of railways and the number of critical infrastructure at risk from a 1% AEP flood event will increase slightly

� More surface water and urban drainage flooding to critical infrastructure and transport routes will occur in the future

MEDIUM-

� The AAD and economic damages caused by flooding will increase by approximately £76,000 and up to £60,000 respectively

� The balance of FRM expenditure to AAD will become unacceptable with AAD to property increasing by more than £76,000 in the future

NO GAINS

feasible.

Policy option P4

Environmental

Social

NO LOSSES

NO LOSSES

NO GAINS

HIGH+

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will not increase in the future

� The number of properties at risk of surface water and urban drainage flooding will not increase in the future

� The length of A road at risk from a 1% AEP flood event will not increase in the future

� The length of railways

Preferred Policy Option – There are no losses under this policy. The numbers of people and properties affected by flooding and the disruption caused will not increase in the future. The AAD and economic damages will remain constant and the associated future FRM expenditure will be efficient.


Economic

NO LOSSES

and the number of critical infrastructure at risk from a 1% AEP flood event will not increase in the future

� Surface water and urban drainage flooding to critical infrastructure and transport routes will not occur in the future

HIGH+

� The AAD and economic damages caused by flooding will not increase in the future

� The balance of FRM expenditure to AAD will remain acceptable with slight increases in FRM expenditure to maintain AAD to property at current levels in the future

Policy option P5

Environmental

Social

NO LOSSES

NO LOSSES

NO GAINS

HIGH+

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will be reduced by more than 25 and more than 11 respectively

� The number of properties at risk of surface water and urban drainage flooding will be reduced from approximately 30 to 0

� The length of A road at risk from a 1% AEP flood event will be reduced

� The length of railways and the number of critical infrastructure at risk from a 1% AEP flood event will be reduced

� Surface water and urban drainage

Not preferred option – Although there are additional gains in terms of reducing the numbers of people and properties affected by flooding and minimising the disruption it causes, these benefits are marginal in relation to additional FRM expenditure. This option is therefore not efficient.


Economic

MEDIUM-

� The balance of FRM expenditure to AAD will become unacceptable in the future with significant increases in FRM expenditure to reduce AAD to property by more than £3,000

flooding to critical infrastructure and transport routes will not occur in the future

HIGH+

� The AAD and economic damages caused by flooding will be reduced

Policy option P6

Environmental

Social

Economic

Not applicable Not applicable Not preferred option – this Policy Option is not considered feasible in this policy unit.

Key

HIGH:


MEDIUM:


LOW:


NEUTRAL: Neutral A policy has a ‘neutral’ effect where it makes neither a positive or negative contribution to a social, economic or environmental objective. A ‘neutral’ effect could be: (i) no change in current level of risk. In this instance the current level of risk would have to be low, so that the residual risk after a neutral policy was implemented remained acceptable; (ii) no change in flood risk under future conditions. In this instance projected future risk would need to be low so that the residual risk after a neutral policy was implemented remained acceptable, and/or; (iii) no additional social, economic and/or environmental gains or losses. Policy options may also be ‘neutral’ where they are not relevant in a particular


policy unit, or where it is not feasible for a policy option to contribute to an objective.

HIGH:


MEDIUM:


LOW:





Physical characteristics: - Largely comprising the urban areas Burgess Hill and Hassocks. - Policy unit is split between the High and Low Weald Landscape Character Areas. - The extreme north and extreme south of the unit area overlie sandstone (Cuckfield

Member), and Weald Clays predominate throughout the central section. - The source of the Adur East Branch emerges amongst undulating topography east

of Burgess Hill. - Ditchling Common SSSI grassland habitat requires a wide variation in drainage

conditions. - Flood risk in Burgess Hill may increase due to pressure for urban expansion and

development. Flood mechanism:

- Relatively rapid runoff from steep slopes in the High Weald. - A combination of surface water flooding, urban drainage problems and under

capacity of local streams causing localised areas of fluvial flooding and urban flooding.

Receptor: - People, properties and infrastructure in Burgess Hill and Hassocks. - Local minor roads. - Currently approximately 13 properties at risk of fluvial flooding in the policy unit from

the 1% annual probability fluvial flood event, which is expected to increase to 250 due to climate change.




Annual averages damages (approx.) £4,000 Future Flood risk:

- Flood risk from fluvial flooding is currently assessed as low, assessment increases to medium in the future.

- Flood risk from surface water flooding and urban drainage problems is currently assessed as low to medium, assessment becomes medium in the future.

Future Flood Risk Summary (in 100 years time)


Total damages (approx.) (1% annual probability flood event) £2 million

Problem/risk

Annual averages damages (approx.) £77,000

Policy selected Policy 4 - Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and climate change).

Justification

Policy 4 sets a framework which prevents the level of flood risk increasing in the future as a result of climate change or increased urban growth. It does not, however, support extensive effort in reducing flood risk from its current level either now or in the future. Current maintenance activities include grass and weed cutting, debris removal cutting back overhanging branches. This may have to increase in the future under a policy 4 option. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low. - Climate change and urban development could increase future levels of flood risk from

localised flooding. - This policy would achieve the economic and social objectives of making sure that flood

risk does not increase in the future as a result of climate change and/or urban development.


- Ensure flood damages do not increase in Burgess Hill and Hassocks due to future change (urban development and climate change).

- Ensure that river channel and flood defence maintenance expenditure is appropriate to the property economic damage in urban areas from flooding.

- Ensure the impact of flooding on people and property does not significantly increase in Burgess Hill and Hassocks in the future.

- Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Burgess Hill and Hassocks in the future.


Opportunities: - Provide development control advice to ensure no increase in run-off from the new

development proposed in the South East Plan (e.g. Burgess Hill). - Reduce flood risk and improve water quality by promoting and encourage the use of


SuDS in the proposed urban developments in Burgess Hill. - Potential for improving the current defences, for example possible installation of

demountable or temporary defences in Shoreham and Burgess Hill. - Continued practice and development of the Emergency Response Plan in Brighton and

Hove, Worthing, Shoreham, and Burgess Hill. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. Constraints: - Government and international legislation, environmental management policies, plans and



- Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Transport links in the catchment are a vital part of the communication network regionally,

nationally and internationally, in particular the railways connecting London to the south coast and connecting the coastal towns and cities, the A23, A24, A27, A259, A283 and A2032.


Policy 1 - do nothing. The urban areas of Burgess Hill and Hassocks currently have a low risk of flooding. However, the risk of flooding from surface water and rivers may increase with climate change and urban development. Without continued maintenance the damages and losses would increase. The number of people at risk from river flooding would increase to more than 750. Do nothing is, therefore, not an appropriate policy. Policy 2 - reduce current level of flood risk management. As with policy option 1, the potential damages and losses would become unacceptable in the future under a ‘do less’ policy. The number of people at risk from river flooding would increase to more than 625. Policy 3 - maintain the current level of flood risk management. Although the current level of flood risk is considered acceptable, it has been shown that flood risk will increase in the future due to a combination of fluvial, surface water and urban drainage flooding. This policy is therefore not acceptable. Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified. Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. Due to limitations in the modelling the properties at risk in the future have been adjusted based on Flood Zones and as such the future AAD has been estimated. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.






Is there a need for further more detailed appraisal? No






Indicators to be included in policy unit 2 implementation plan are: Economic - Total annual average damages (to properties and agriculture) from fluvial flooding (£AAD). - Estimated damages resulting from surface water flooding (£) (based on historical damages). - Balance of annual river channel and flood defence maintenance expenditure (£) to annual average

damages from fluvial flooding to property (£). Social - Number of people and properties affected by the 1% annual probability fluvial flood event. - The estimated number of properties affected by surface water flooding (based on historical

records). - Length of A road and railway line (km) affected by the 1% annual probability flood event. - Number and period of recorded A road and railway closures due to surface water flooding (based

on historical records). - Number of critical infrastructure sites affected by the 1% annual probability flood event. - Number of critical infrastructure sites recorded as being affected by surface water flooding (based

on historical records).


Policy unit 3 Steyning and Upper Beeding










Policy unit 3 – Steyning and Upper Beeding


Defences: There is a total of 3.5km of culverted channel sections and flood embankments to both banks along the River Adur throughout this policy unit. Flood warning: This area is included in the Lower Adur flood warning area. There are more than 110 properties connected to the flood warnings direct service. Maintenance: We currently carry out annual inspection and maintenance of the tidal embankments and land drainage sluice gates. The estimated annual cost of maintaining the channels and existing defences under the Environment Agency’s responsibility is approximately £60,000.


Standard of protection: The River Adur embankments are considered to offer protection ranging from the 3.3% annual probability fluvial flood event (1 in 30) to the 2% annual probability fluvial flood event (1 in 50). They are considered to be at or above the target condition.




outline*

Residential properties 3 91 103 Commercial properties 0 11 N/A Population 0 210 N/A Property damages 0 £2.944 million N/A Agricultural damages £2,355 £7,140 N/A A roads 0 km 0.76 km 0.48 km Railways 0 km 0 km 0 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2


2 0 km

2


2 0.15 km

2


2 1.06 km

2


2 0 km

2


2 0.65 km

2

SSSI 0 km2 0 km

2 0 km

2


2 0.24 km

2 0.27 km

2

ESA 0 km2 0.26 km

2 0.29 km

2


0 km2 0 km

2 0 km

2


2 0.96 km

2




Economic and social receptors: There is flood risk to people, properties and infrastructure in Steyning, Upper Beeding and Bramber from fluvial flooding, surface water flooding and some urban drainage flooding. Currently 102 properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. The majority of these properties are residential. Short sections of the A283 and A2037 lie in the 1% annual probability flood event outline. Only moderate to low grade agricultural land (Grades 3 and 4) is at risk of localised fluvial flooding. Environmental designations: There are no internationally designated sites or SSSIs at risk of flooding within this policy unit. Total area of approximately 0.5km

2 of the River Adur Water Meadows and

Wyckham Wood SNCI is located within the 1% annual probability flood event outline in this policy unit. The sensitivity of this site to flooding is low and may


benefit from periodic flooding. Landscape: Approximately 0.25km of the Sussex Downs AONB and South Downs ESA and 0.84km

2 of the proposed South Downs National Park is located within the 1%

annual probability flood outline in this policy unit. Natural and Historic Environment: Three listed buildings are within the1% annual probability flood event outline, increasing slightly to four within the extreme flood outline. There are no registered historic parks and gardens within this policy unit. There are nine SMs (salterns) within the 1% annual probability flood event outline. This increases to ten SMs (salterns) within the 0.1% annual probability flood event outline.


Increase in frequency of storm events resulting more frequent fluvial and surface water flooding. Sea level rise* increases the likelihood of tidally influenced flooding in this policy unit. *To represent future sea level rise, the tidal boundary within the broadscale model was scaled to

increase the maximum still water level by 600mm for the 100 year timescale. These climate change figures used were the accepted approach for ‘typical’ catchments when the scoping stage broadscale modelling was carried out. Since the scoping stage was completed new Defra guidance (October 2006) on climate change has been released which suggest that for a 100 year time scale, sea level may rise by almost 1m. Therefore the results from the broadscale model in the tidally influenced areas are likely to have under predicted the increase in flood risk and damages in the future.


There is an increase (approximately £0.1 million) in AAD due to climate change over the next 100 years. In 100 years just over 110 properties are at risk of flooding in the policy unit from the 1% annual probability fluvial flood event.


Improve existing or construct new defences and reduction in flows entering the catchment through improved management or attenuation upstream. This policy unit is unsuitable for large scale attenuation; small scale attenuation is unlikely to successfully manage flood risk alone. An improvement in land use run-off management in upstream catchments could reduce flows entering this policy unit.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. Delivering this policy will partly depend on developing and implementing effective urban drainage in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.





damages (£m)

The broadscale modelling has indicated that a change in the way land is managed, in the upper parts of the CFMP area, has a positive impact on flood damages within this policy unit. Flood damages are shown to decrease by 6% for the 1% annual probability fluvial flood event.



% change = -6%

Conclusions

The reduction in damages for the 1% annual probability fluvial flood event is small. Although the impact on flood risk from changing land use in the upper catchment is not large, it is nonetheless significant and together with other flood risk management options, land use change in the upper catchment can provide a useful way of reducing flood risk to Steyning and Upper Beeding.



damages (£m)

Removing the embankments along the River Adur allows more frequent inundation of the floodplain on both sides of the river. The results from the broadscale modelling show a large reduction of 58% for a 1% annual probability fluvial flood event. At Steyning and Upper Beeding, water depths are reduced from between 0.5 to 0.8m.



% change = -58%

Conclusions

The impact of lowering the embankments along the River Adur within this policy unit is surprising as the larger, more extreme fluvial flood events result in a reduction of flood damages in Steyning and Upper Beeding. This is because the increased inundation of the floodplains upstream and downstream of Steyning and Upper Beeding has the effect of reducing the peak water levels in the River Adur and allows water to drain away more effectively from the floodplains, lowering the water depths through the urban areas. The impact is complex however, and reducing the height of the raised embankments does not result in reductions in flood depths everywhere. Some locations that would normally be defended to some extent by the existing defences will receive greater depths of flooding for an equivalent size of flood event. For the more frequent, less severe events the flood damages increase. This has the effect of increasing the annual average damages, which take into account a wide range of flood severity in the calculation.

Generic response: Increasing conveyance on the Adur East Branch


damages (£m)

The broadscale modelling has indicated that increasing conveyance in the whole of the Adur East Branch has minimal impact at Steyning and Upper Beeding.



% change = +0.3%

Conclusions

The benefits experienced from the increased conveyance on the Adur East Branch are evident (see policy unit 2). However, the flood mechanisms at Steyning and Upper Beeding are dominated by tidal influences and the impact of any changes in fluvial flows upstream are small in comparison.



damages (£m)

The broadscale modelling has indicated that applying flood storage on the Adur West Branch (of no specific size or location) has a small positive effect on flood damages within this policy unit (approximately £0.231 million decrease in flood damages). The results show a 6% decrease in flood damages for the 1% annual probability fluvial flood event.



% change = -6%

Conclusions

A large flood storage reservoir on the Adur West Branch will provide some benefit to Steyning and Upper Beeding by reducing flood damages. The effect on flood extent in this policy unit is minimal, however there is a reduction of approximately 0.1 to 0.15 m in flood depth, which results in the decrease in flood damages.


Generic response: Barrier across the River Adur at Shoreham Harbour


damages (£m)

This case looks at the situation where a barrier is built across the mouth of the river that keeps the tide out, but allows free discharge of the river into the sea at low tide. The modelling has shown that the reduction in flooding through this approach is not significant for the 1% annual probability fluvial flood event within this policy unit. The annual average damage value, however, does show a significant reduction in flood damages, of approximately 30%.



% change = -1%

Conclusions

Although this approach has shown not to be effective at reducing flood damages for the 1% annual probability fluvial flood event, it has however, shown a significant reduction in flood damages for the more frequent events. For the 4% annual probability fluvial flood event there is a reduction of approximately 56% on flood damages and for the 10% event the reduction is 94%. This flood management response allows free flow of water out of the river, but prevents water from the sea entering at high tide. High tides will still have an effect on flooding within the river by preventing discharge when the water level in the sea is higher than the water levels in the river. However, it is the duration of this tide locked condition that is important and not the actual sea level reached by the high tide. Cost and technical feasibility is not a prime consideration for the CFMP, however it must be recognised that this approach would need further investigation.




KEY = Scale of policy impact on objective: Not appraised Baseline Meets objective No impact Doesn’t meet object Uncertain






Opportunities and Constraints






reduced.


reduce over time.


A do nothing


unpredictable way.





place.



place.


of watercourses.




of watercourses.


Increase the local

defence works.


unit.

Economic objectives


increase in Steyning and Upper Beeding due to future change (urban


Targets No significant increase in damages in Steyning and Upper Beeding from fluvial, surface water and urban drainage flooding due to future changes

(urban development and climate change).

Indicators




water flooding (£).

*Estimation based on historical damages observed in the

Brighton area from the 2000/ 2001 flood event (Binnie Black

& Veatch 2001 – Flood Defence Assessment of Downland

Flooding).


advice to ensure no increase in run-off from new development.

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in proposed developments.

- Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

Constraints - Government and international

legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.



damages from fluvial flooding are

approximately £86,000; this

increases to around £206,000 in the future.

There are no historic

records of surface water flooding and

therefore we have not been able to estimate

the damages, however, surface water flooding is a

known problem in this area and it is likely to increase in the future.

No maintenance of channels and a reduction in the

height of the embankments would lead to a significant increase in flooding

with total annual average damages

from fluvial flooding increasing to more

than £500,000.

No maintenance will lead to a significant increase from the

current level of surface water flooding and

associated damages.

As channels decrease in conveyance and

capacity due to reduced maintenance

the total annual average damages from


than £330,000.

There will be a substantial increase from the current level

of surface water flooding and

associated damages with a reduction in

maintenance.

The total annual average damages

from fluvial flooding will increase over time due to the affects of climate change to be

approximately £206,000.

There are no records

of surface water flooding, however, a

slight increase in surface water flooding

and associated damages is likely due

to the affects of climate change.

Improved channel maintenance and

localised protection measures will mitigate the affects of climate

change. The total annual average

damages from fluvial flooding will remain at


Surface water flooding and associated

damages will remain at the current levels.

Improved channel maintenance and increased local

defence works would reduce total annual average damages

from fluvial flooding to be less than £10,000 and

damages resulting from surface water

flooding to be minimal.

Not applicable.










Indicators














from fluvial flooding to property are currently

around £85,800, increasing to around

£205,000 in the future.







to be more than £450,000.

The balance of expenditure to






£310,000.



Channel and flood defence maintenance expenditure remains

at approximately £60,000. Annual average damages

from fluvial flooding to property increase over time due to the affects of climate change to be around £205,000.


damages is considered to be

acceptable.






property will remain around £85,800.

With better

maintenance efficiency and effective use of

funding the balance of expenditure to





Annual average damages from fluvial flooding to property are estimated to be less than £10,000.


damages will be unacceptable with expenditure being unjustifiably high.

Not applicable.

Social objectives


property does not significantly increase in

Steyning and Upper Beeding in the future.


the 1% annual probability fluvial flood event or surface water

flooding in Steyning and Upper Beeding in the

future.

Indicators Number of people and properties affected by


event.

The estimated* number of properties affected by surface water flooding.

*Surface water/ urban drainage

flooding estimates based on historical records.




- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in proposed developments.




- Visual impact of flood risk management activities within the proposed National Park or Areas of Outstanding Natural Beauty.




flood event. This increases slightly to around 270 people

and 115 properties in the future.

There are no historic

records of surface water and urban

drainage flooding and therefore we have not been able to estimate

the number of properties affected by

these sources of flooding. However, surface water and



Approximately 89

properties are currently covered by the Flood Warning

Service.


height of embankments would result in a significant



drainage flooding.

The number of people and properties

at risk of localise fluvial flooding will

increase to be more than 310 and 130

respectively.

There will be a significant increase

from the current level in the number of

properties affected by surface water and




channels would result in an increase in the

frequency, extent and depth of localised

fluvial and surface and urban drainage

flooding.




respectively.

There will be a substantial increase






Maintenance of channels and

drainage networks continues at the

current level.

The number of people and properties at risk

of localised fluvial flooding is likely to slightly increase to approximately 270

and 115 respectively.

Over time the number of properties at risk of


flooding will gradually increase from the

current level due to the affects of climate

change.

The current level of Flood Warning

Service remains in place.




102 respectively.



flooding will remain at the current level.





defence works and flood warning service

will reduce the number of people

affected by localised fluvial flooding to less than 25 and number of properties affected

to less than 10.


drainage flooding.


and coverage

Not applicable.



infrastructure does not increase in Steyning and

Upper Beeding in the future.


line or increase in extent of critical infrastructure

flooded, in Steyning and Upper Beeding and

surrounding areas, from a 1% annual probability

fluvial flood event or surface water flooding.

Indicators

Length of A road and railway line (km) affected

by the 1% annual probability fluvial flood

event.






water flooding*.

*Surface water/ urban drainage flooding estimates based on

historical records.








There is no extent of railway within this

policy unit.

Currently approximately 0.76km

of A road and no critical infrastructure sites are affected by

the 1% annual probability flood event.

In the future only a minor increase in length of A road is affected by the 1% annual probability

flood event.

There are no records of A road and critical infrastructure sites being affected by surface water and

urban drainage flooding, however, surface water and




drainage networks and a reduction in the

height of embankments would result in an increase

in the frequency, extent and depth of localised fluvial and surface and urban drainage flooding.

More than 1.2km of A road is likely to be at risk of flooding from



Substantially more surface water and

urban drainage flooding of A roads. Surface water and

urban drainage flooding may affect

some critical infrastructure sites.


channels would result in an increase in the



flooding.

More than 1km of A road is likely to be at risk of flooding from



More surface water and urban drainage flooding of A roads. Surface water and

urban drainage flooding may affect




current level.

In the future only a minor increase in length of A road is affected by the 1% annual probability

flood event.

There will be a minor increase, from the

current risk, of surface water and urban

drainage flooding to A roads and critical

infrastructure sites.

The minor increase in risk of flooding does not lead to a notable

increase in disruption, therefore this policy

option does meet the objective.



Approximately 0.76km

of A road and no critical infrastructure sites are affected by

flooding during the 1% annual probability flood

event.



flooding to A roads and critical infrastructure

sites.


defence works will reduce fluvial and surface water and


No extent of A road

or critical infrastructure sites will be affected by fluvial or surface water and urban

drainage flooding.

Not applicable.


Protect and enhance the River Adur Water

Meadows and Wyckham Wood Site of Nature



River Adur Water Meadows and Wyckham

Wood Site of Nature Conservation Importance.

Indicators








There is currently 0.53km

2 of the SNCI



This is a small increase to around

0.63km2 of the SNCI


flood event outline in the future. There

maybe some potential to improve or increase the habitat types and

species diversity within the SNCI.

Doing nothing and reducing the height of embankments would

allow the rivers to flood more frequently

and increase the flood depths,

increasing the area of the SNCI within the


substantially more than 0.63km

2.

There is increased

potential to substantially improve





channels would eventually allow the rivers to flood more

frequently and increase the flood depths,

increasing the area of the SNCI within the 1% annual probability flood

outline to more than 0.63km

2.

There is increased




0.63km2 in the area of

the SNCI within the 1% annual probability flood event outline due

to the affects of climate change in the future. There maybe

some potential to improve or increase the habitat types and

species diversity within the SNCI.


approximately 0.53km2.

There will be no


SNCI.


defence works will reduce the extent of

flooding and therefore the extent

of the SNCI within the 1% annual probability flood outline to less

than 0.53km2.




SNCI.

Not applicable.


Does this policy change flood risk locally or elsewhere: Impact uncertain Impact uncertain


climate change

Risk downstream likely to increase

Risk downstream likely to increase

NA




Policy Unit 3 - Steyning and Upper Beeding


Policy option P1

Environmental

Social

Economic

NO LOSSES

HIGH-


� The number of properties at risk of surface water and urban drainage flooding will increase significantly



� The number of critical infrastructure at risk from a 1% AEP flood event will increase

� Substantially more surface water and urban drainage flooding to critical infrastructure and transport routes will occur

HIGH-

� The AAD to properties and agricultural land caused by fluvial

HIGH+

� The area of the River Adur Meadows and Wyckham Wood SNCI will significantly increase by more than 1km

2 but in an


NO GAINS

NO GAINS

Not preferred option – There are limited gains under this policy option. The numbers of people and properties adversely affected by removing FRM are unacceptably high. The AAD are also high and the environmental effects are unpredictable due to the unmanaged and uncontrolled nature of this policy option.


flooding will increase by more than £414,000

� AAD to properties and agricultural land caused by surface water flooding will significantly increase

� The balance of FRM expenditure to AAD is unacceptable with AAD to properties and agricultural land increasing by more than £364,200

Policy option P2

Environmental

Social

Economic

NO LOSSES

HIGH-




� The number of critical infrastructure at risk from a 1% AEP flood event will increase

� Substantially more surface water and urban drainage flooding to critical infrastructure and transport routes will occur

HIGH-

� The AAD to properties and agricultural land caused by fluvial flooding will increase by more than £244,000

HIGH+

� The area of the River Adur Meadows and Wyckham Wood SNCI will significantly increase by more than 1km

2 but in an

unmanaged way NO GAINS

NO GAINS

Not preferred option – There are limited gains under this policy option. The numbers of people and properties adversely affected by removing FRM are unacceptably high. The AAD are also high and the environmental effects are unpredictable due to the unmanaged and uncontrolled nature of this policy option.


� AAD to properties and agricultural land caused by surface water flooding will significantly increase


Policy option P3

Environmental

Social

Economic

NO LOSSES

LOW-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase in the future by approximately 55 and 13 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase in the future

� The length of A road and number of critical infrastructure at risk from a 1% AEP flood event will increase only slightly

� A minor increase in surface water and urban drainage flooding to critical infrastructure and transport routes will occur in the future

MEDIUM-

� The AAD to properties and agricultural land caused by fluvial flooding will increase by approximately £120,000

� AAD to properties and agricultural land caused by surface water flooding will increase slightly in the future

MEDIUM+

� The area of the River Adur Meadows and Wyckham Wood SNCI will increase by approximately 1km

2 in

the future

NO GAINS

LOW+

� The balance of FRM expenditure to AAD will remain acceptable with AAD to properties and agricultural land increasing by approximately £119,200 in the future

Preferred Policy Option – Although there are some losses in terms of the numbers of people and properties and the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change.


Policy option P4

Environmental

Social

Economic

NO LOSSES

NO LOSSES

NO LOSSES

LOW+

� The area of the River Adur Meadows and Wyckham Wood SNCI will remain the same with no increases in biodiversity

HIGH+



� The length of A road and number of critical infrastructure at risk from a 1% AEP flood event will not increase in the future

� Surface water and urban drainage flooding to critical infrastructure and transport routes will not increase in the future

HIGH+

� The AAD to properties and agricultural land caused by fluvial flooding will not increase in the future

� AAD to properties and agricultural land caused by surface water flooding will not increase in the future

� The balance of FRM expenditure to AAD will remain acceptable with slight increases in FRM expenditure to maintain AAD to properties and agricultural land at current levels in the future

Not preferred option – Although there are additional benefits in terms of the numbers of people and properties and reducing the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change. It should therefore be unnecessary to further increase FRM in this policy unit in order to ensure risk does not increase.


Policy option P5

Environmental

Social

Economic

MEDIUM-

� The area of the River Adur Meadows and Wyckham Wood SNCI will be decreased

NO LOSSES

MEDIUM-

� The balance of FRM expenditure to AAD will be unacceptable with significant increases in FRM expenditure to reduce AAD to properties and agricultural land by more than £75,800

NO GAINS

HIGH+

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will be reduced by more than 90 and more than 92 respectively

� The number of properties at risk of surface water and urban drainage flooding will be reduced to 0

� The length of A road and number of critical infrastructure at risk from a 1% AEP flood event will be reduced to 0

� Surface water and urban drainage flooding to critical infrastructure and transport routes will not occur in the future

HIGH+

� The AAD to properties and agricultural land caused by fluvial flooding will be reduced

� AAD to properties and agricultural land caused by surface water flooding will be minimal

Not preferred option – Although there are significant benefits in terms of the numbers of people and properties and minimising the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change. It should therefore be unnecessary to further increase FRM in this policy unit in order to ensure risk does not increase.

Policy option P6

Environmental

Social Economic


Key


HIGH:


MEDIUM:


LOW:


NEUTRAL: Neutral A policy has a ‘neutral’ effect where it makes neither a positive or negative contribution to a social, economic or environmental objective. A ‘neutral’ effect could be: (i) no change in current level of risk. In this instance the current level of risk would have to be low, so that the residual risk after a neutral policy was implemented remained acceptable; (ii) no change in flood risk under future conditions. In this instance projected future risk would need to be low so that the residual risk after a neutral policy was implemented remained acceptable, and/or; (iii) no additional social, economic and/or environmental gains or losses. Policy options may also be ‘neutral’ where they are not relevant in a particular policy unit, or where it is not feasible for a policy option to contribute to an objective.

HIGH:


MEDIUM:


LOW:





Physical characteristics: - Urban area of Steyning and Upper Beeding villages, which are separated laterally

by the Lower River Adur. - The unit overlies weald clay to the north and chalk to the south, and has very

subdued topography. - Lies at the northern base of the South Downs escarpment and the majority of the

unit lies within the proposed South Downs National Park designated area. Flood mechanism:

- Land behind the defences becomes seasonally waterlogged, resulting in flashy responses to rainfall.

- Combination of surface water run-off, urban drainage and under capacity of local streams causing localised fluvial flooding and urban flooding.

- Overtopping of raised river embankments along the River Adur – will generally not overtop due to fluvial flooding on its own, requires significant tidal influence.

Receptor: - People, properties and infrastructure in Steyning and Upper Beeding. - A small number of listed buildings and heritage sites (salterns) lie in the floodplain. - Currently 91 properties are at risk of fluvial flooding in the policy unit from the 1%

annual probability fluvial flood event. - The flood risk increases slightly changes over the next 100 years. - Surface water flooding is likely to increase more significantly than fluvial flooding.





Future Flood risk: - Flood risk from surface water flooding and urban drainage problems is currently

assessed as low, assessment changes to low to medium in the future. - Flood risk from fluvial flooding is currently assessed as low, assessment changes to

medium in the future. Future Flood Risk Summary (in 100 years time)



Problem/risk


Policy selected Policy 3 - Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk with increase over time from this baseline).

Justification

This policy is appropriate where the current level of flood risk management is considered acceptable. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal cutting back overhanging branches. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low and it is not expected to increase greatly in the

future. - The consequences of flooding are relatively low. - The current flood risk management activities, carried out for the localised fluvial and

surface water and urban drainage flooding problems, are considered appropriate and acceptable for the level of risk.

- The selected policy would help achieve the catchment objectives to ensure the impact of flooding does not significantly increase.

- This policy unit will also benefit from the policy 6 option adopted for policy unit 1.


- Ensure flood damages do not significantly increase in Steyning and Upper Beeding due to future change (urban development and climate change).


- Ensure the impact of flooding on people and property does not significantly increase in Steyning and Upper Beeding in the future.

- Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Steyning and Upper Beeding in the future.

- Protect and enhance the River Adur Water Meadows and Wyckham Wood Site of Nature Conservation Importance.



Opportunities: - Provide development control advice to ensure no increase in run-off from new

development. - Reduce flood risk and improve water quality by promoting and encourage the use of

SuDS in proposed developments. - Investigate removal of Environment Agency owned and maintained existing raised

defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.

- Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - Help meet national biodiversity action plan (BAP) targets. Constraints: - Government and international legislation, environmental management policies, plans and



- Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Visual impact of flood risk management activities within the proposed National Park or

Areas of Outstanding Natural Beauty. - Transport links in the catchment are a vital part of the communication network regionally,





Policy 1 - do nothing. The urban areas of Steyning, Upper Beeding and Bramber currently have a low level of risk of flooding. However the risk of flooding from surface water and rivers may increase with climate change. Without continued maintenance the average annual damages would increase to more than £500,000. Do nothing is, therefore, not an appropriate policy. Policy 2 - reduce current level of flood risk management. As with policy option 1, the potential damages and losses would become unacceptable in the future under a ‘do less’ policy. The average annual damages would increase to more than £330,000. Policy 4 – maintain the current level of flood risk into the future. This policy could also apply, however, it implies increasing flood risk management costs to more than £60,000 p.a. in the future. The need for this has not been identified or considered justifiable. Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is adequately managed and therefore this policy is not justified. Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (at the time of the assessment), frequency and size of storms and flood events in the future. The broadscale modelling has shown that by increasing the flooding in policy units upstream there is a small reduction in flood risk in this policy unit (approximately 5%). We will need more detailed studies to find out if it is practical to do this. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.












Indicators to be included in policy unit 3 implementation plan are: Economic

- Total annual average damages (to properties and agriculture) from fluvial flooding (£AAD). - Estimated damages resulting from surface water flooding (£) (based on historical damages). - Balance of annual flood risk maintenance expenditure (£) to annual average damages from fluvial

flooding to property (£). Social - Number of people and properties affected by the 1% annual probability fluvial flood event. - The estimated number of properties affected by surface water flooding (based on historical

records). - Length of A road and railway line (km) affected by the 1% annual probability fluvial flood event. - Number of critical infrastructure sites affected by the 1% annual probability fluvial flood event. - Number and period of recorded A road and railway closures due to surface water flooding (based

on historical records). - Number of critical infrastructure sites recorded as being affected by surface water flooding (based

on historical records). Environmental - Habitat quality and species diversity.


Policy unit 4 South Downs (West)










Policy unit 4 – South Downs (West)


Defences: There are no formal flood defences in this policy unit. Flood warning: This policy unit is not covered by a fluvial flood warning area. There are no properties connected to the flood warning direct service. Maintenance: The Soil Society periodically inspects the land east of Findon Valley to ensure continued preservation of soil. The estimated annual cost of maintenance undertaken by the Environment Agency within this policy unit is approximately £1,000.


Standard of protection: There is no formal raised flood defences within this policy unit.


outline*

In 1% flood

outline*

In 0.1% flood

outline*

Residential properties 0 0 0 Commercial properties 0 0 0 Population 0 0 0 Property damages 0 0 N/A Agricultural damages 0 £455 N/A A roads 0 km 0 km 0.33 km Railways 0 km 0 km 0 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2


2 0 km

2

Agricultural land Grade 3 0 km2 0.02 km

2 0.04 km

2


2 0 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0 km

2

SSSI 0 km2 0 km

2 0 km

2


2 0.02 km

2 0.04 km

2

ESA 0 km2 0.02 km

2 0.04 km

2


0 km2 0 km

2 0 km

2

Proposed National Park 0 km2 0.02 km

2 0.04 km

2




Economic and social receptors: There are no residential or commercial properties within the 1% annual probability flood event outline. A very small area of moderate grade agricultural land (Grade 3) is at risk of flooding for the 1% annual probability flood event. Environmental designations: No extent of internationally or nationally designated sites, SSSIs or SNCIs is at risk of flooding from the 10%, 1% or 0.1% annual probability flood event within this policy unit. Landscape: Less than 0.05km2 of the Sussex Downs AONB, Sussex Downs ESA and proposed South Downs National Park lies within the 1% and 0.1% annual probability flood event outlines. Natural and Historic Environment: There are no listed buildings, registered historic parks and gardens or SMs at risk of flooding for the considered annual probability flood events in this policy unit.


Land use changes contributing to increase in soil erosion, such as changes in crop type and increases in livestock stocking density.


Flood risk is currently assessed as low, and it is not expected to increase under future scenarios.



Potential to work with professional partners to derive better land management options so that run-off can be reduced and soil erosion avoided.


There is uncertainty about how effective changes in land management and vegetation cover will be in altering run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.

There is no flood risk within this policy unit, however, it does contribute to groundwater flooding and surface water run-off in neighbouring policy units. We have not been able to model these processes and it has therefore not been possible to define generic responses in this policy unit.
















reduced.


increase the flooding in an unmanaged and

unpredictable way.






of watercourses.


Introduce management

practices that allow greater water

retention within the policy unit i.e. change

in land use.






There is potential to

increase water retention by

introducing flood storage areas.

Economic objectives




from flooding.





(£).





(£).










approximately £1,000; the annual average

damages from fluvial flooding to agriculture are currently less than £100. Annual average damages from fluvial flooding to agriculture

are unlikely to significantly increase, being less than £150

in the future.






from fluvial flooding to agriculture

increase to be more than £2,000.





Annual average damages from fluvial flooding to agriculture are likely to be around

£1,000.


damages becomes unacceptable over

time.


at approximately £1,000. Annual

average damages from fluvial flooding to agriculture increase over time due to the

affects of climate change to be around

£150.








agriculture will remain less than £100.

With better






increase to be more than £1,000. Annual

average damages from fluvial flooding to agriculture are

estimated to be £0.




maintenance expenditure is likely to remain the same or be





are likely to remain less than £100.



In addition policy unit 5 is likely to benefit

from the agri-environmental

schemes, which should reduce muddy

flooding.

Social objectives




in the future (for example due to climate change).



Indicators



event


Opportunities - Reduce flood risk and

improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham and Burgess Hill.

Constraints

- Government and international legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and compliance with the Habitats Directive.




flooding by the current 1% annual probability flood event. This is not anticipated to

increase the future.

There are currently no properties covered by

a flood warning service.





The number of



There will be no flood

warning system which may result in

increased risk to human life.



localise fluvial flooding may increase to be

more than zero.

There is no flood warning service

available, which may result in increased risk

to human life.

No people and properties are likely to be at risk of localised fluvial flooding by the 1% annual probability

flood event


available.


flood event

Flood Warning Service is introduced.

No people and properties are likely

to be at risk of localised fluvial

flooding by the 1% annual probability

flood event




current baseline and There is no flood warning service

available.


Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National

Park.

Targets Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National

Park.


assessment of the AONB, ESA and

proposed National Park.







2 of the Sussex

Downs AONB and South Downs ESA

and proposed National Park located within the 1% annual probability

flood event outline. This increases by a

minor extent over time to approximately

0.032km2 in the future.

The landscape character of the

Sussex Downs AONB and South Downs ESA and proposed

National Park is unlikely to notable

alter.

The area of the Sussex Downs

AONB and South Downs ESA and

proposed National Park located within

the 1% annual probability flood

event outline increases to be more

than 0.05km2.

The landscape character of the Sussex Downs





controlled way.

The area of the Sussex Downs AONB and

South Downs ESA and proposed National Park located within the 1%

annual probability flood event outline increases to be slightly more than

0.032km2.


Sussex Downs AONB and South Downs ESA and proposed National Park is likely to alter in a beneficial manner,

however, it will occur in an unmanaged way.

The area of the Sussex Downs AONB

and South Downs ESA and proposed


time to at around 0.032km

2.

There would be no

notable impact on the landscape character of the Sussex Downs


proposed National Park in this policy unit.



annual probability flood event outline remains at around 0.02km

2.

There would be no

impact on the landscape character of

the Sussex Downs AONB and South Downs ESA and


Introducing management practices that

increase water retention and reduce

run-off within the catchment is likely to reduce frequency and depth of flooding and

therefore have a negative impact on

the landscape character of the Sussex Downs







event outline decreases to be

minimal.



National Park can be enhanced with the implementation of


practices, such as increasing the flood storage areas, in a

managed and controlled way.

Does this policy change flood risk locally or elsewhere: Impact uncertain, but no significant

impact on adjacent policy units anticipated.

Impact uncertain, but no significant impact on adjacent policy units anticipated.

No significant impact on adjacent

policy units.

No significant impact on adjacent policy

units.

Policy unit 5 is likely to benefit from

increased water retention and

reduced run-off, which should reduce

muddy flooding.

Policy unit 5 is likely to benefit from the agri-

environmental schemes, which

should reduce muddy flooding.




Policy Unit 4 - South Downs (West)


Policy option P1

Environmental

Social

Economic

NO LOSSES

MEDIUM-

� The number of people and property at risk significantly increases.

HIGH-

� The balance of FRM expenditure to AAD is unacceptable with AAD to agricultural land increasing by more than £900

MEDIUM+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP are likely to be beneficially altered but in an unmanaged and uncontrolled way

NO GAINS

NO GAINS

Not preferred option – Although the benefits to the environment are potentially high, alterations to the landscape will be unmanaged and uncontrolled and therefore unpredictable. In addition to this, the AAD to agricultural land resulting from this policy will be unacceptably high.

Policy option P2

Environmental

Social

Economic

NO LOSSES

MEDIUM-

� The number of people and property at risk significantly increases.

HIGH-

� The balance of FRM expenditure to AAD is unacceptable with AAD to agricultural land increasing by more than

MEDIUM+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP are likely to be beneficially altered but in an unmanaged way

NO GAINS

NO GAINS



£900 Policy option P3

Environmental

Social

Economic

NO LOSSES

NO LOSSES

NO LOSSES

LOW+

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP will increase slightly but with no notable increase in landscape value

NO GAINS

LOW+

� The balance of FRM expenditure to AAD will remain acceptable with AAD to agricultural land increasing slightly in the future


Policy option P4

Environmental

Social

Economic

LOW-

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP remain the same with no increase in landscape value

NO LOSSES

NO LOSSES

NO GAINS

NO GAINS

MEDIUM+

� The balance of FRM expenditure to AAD will remain acceptable with slight increases in FRM expenditure to maintain AAD to agricultural land at current levels in the future

Not preferred option – Although AAD to agricultural land will not increase in the future, opportunities to bring benefits to the environment are not sufficiently optimised under this policy.

Policy option P5

Environmental

MEDIUM-

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP will be decreased which will

NO GAINS

Not preferred option – There are no gains under this policy option. FRM expenditure is unacceptably high and there will be negative impacts on the


Social

Economic

impact negatively on the landscape value

NO LOSSES

HIGH-

� The balance of FRM expenditure to AAD is unacceptable with significant increases in FRM expenditure to reduce AAD to agricultural land

NO GAINS

NO GAINS

landscape value of the area.

Policy option P6

Environmental

Social

Economic

NO LOSSES

NO LOSSES

NO LOSSES

HIGH+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP will be enhanced in a managed and controlled way

NO GAINS

HIGH+

� The balance of FRM expenditure to AAD will remain acceptable with reductions in FRM expenditure and AAD to agricultural land due to agri-environment schemes and targeted FRM

Preferred Policy Option – There are no losses under this policy option. The potential benefits to landscape value are maximised and will be carried out in a managed and controlled way. The balance between FRM and AAD to agricultural land will be optimised. Encouraging increased uptake of agri-environment schemes will further reduce the AAD to land. Implementing policy option 6 in this part of the catchment will also bring strategic benefits to policy units downstream through increased floodwater storage.

Key

HIGH:


MEDIUM:


LOW:

Low negative A policy has a ‘low negative’ effect where it could make a limited contribution to


a social, economic or environment objective, but where the overall contribution would be negative. A ‘low negative’ effect could be: (i) an overall increase in current flood risk; (ii) an overall increase in flood risk under future conditions, and/or; (iii) overall social, economic and/or environmental losses.


HIGH:


MEDIUM:


LOW:





Physical characteristics: - Steep scarp slopes of the chalk downland hills extend the entire width of the CFMP

area. - Environmentally Sensitive Area and Area of Outstanding Natural Beauty. - Spring line on the southern slopes forms the headwaters of the Teville Stream and

Ferring Rife. - Shallow silty soils are well drained and the chalk is an important local aquifer for

water supply. - Proposed National Park with high amenity value and landscape character. - Contains a significant proportion of Scheduled Monuments and SSSIs in the CFMP

area. Flood mechanism:

- No fluvial flooding within the policy unit. - Land management affects runoff rates with certain types of management causing

muddy floods in adjacent urban areas. Receptor:

- None within the policy unit. - Adjacent urban areas (particularly in Policy Unit 5 (Worthing)) are receptors of

flooding generated due to land management in this unit. Current Flood Risk Summary


Total damages (approx.) (1% annual probability flood event) £455

Annual averages damages (approx.) Less than

£100 Future Flood risk:

- Flood risk is currently assessed as low, and it is not expected to increase under future scenarios.




Problem/risk

Annual averages damages (approx.) Less than

£150


Justification

This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding and infiltration of rainwater locally in this unit, flooding downstream can be reduced. The changes in land management can also benefit biodiversity. Current maintenance activities include grass and weed cutting. Policy 6 sets a framework that actively supports increased flooding and infiltration of rainwater and is appropriate to this policy unit for the following reasons: - Although flood risk is assessed as low within the policy unit, there is the opportunity to

reduce flood risk in adjoining units. - Large rural policy unit presents opportunities for changing land use and developing

possible flood storage mechanisms to reduce rapid run-off generated from land use activities and the steep slopes.

- Action in this unit will help reduce risk of muddy floods in places such as Findon. - There are some opportunities for reducing downstream flooding by improving or creating

new habitats, which increase water retention. - Soil erosion problems can best be tackled through more sensitive land management land

use change and changes in farming practices. - Increased storminess due to climate change may increase soil erosion and localised

flash flooding in neighbouring catchments. - This policy would help meet the environmental and landscape objectives by working with

landowners and the Government.


- Ensure that river channel and flood defence maintenance expenditure is appropriate to the agricultural economic damage in rural areas from flooding.

- Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National Park.

Catchment-wide opportunities

Opportunities: - Improvements in the efficiency of flood defence maintenance processes.


and constraints - To work with Defra and farmers to produce soil management plans which have a benefit to flood risk through reducing the run-off rate.

- Help meet national biodiversity action plan (BAP) targets. Constraints: - Available funding for the initial set up of new flood risk management schemes. - Limited available information on surface water and groundwater flood damages. - Some environmentally designated habitats are susceptible to changes in flood

frequency, floodwater chemistry, groundwater levels and drainage system maintenance. - Changes to flood risk management can affect the landscape, its character and value as

an amenity.


Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, it would limit the opportunities to reduce soil erosion and surface water run-off that affect neighbouring policy units. Policy 2 - reduce current level of flood risk management. There is already minimal flood risk management within this policy unit. It is not possible to reduce it further. Policy 3 - maintain current level of flood risk management. This policy could also apply as maintaining the current level of flood risk management is the same as ‘do nothing’ in this case. But it does imply that a certain level of flood risk management is being carried out which is not correct. Policy 4 - maintain the current level of flood risk into the future. As with policy 3, this policy could apply, but it implies a level of activity that is not happening. Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the level of flood risk within the policy unit.


There is uncertainty about how effectively changes in land management and vegetation cover will alter run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. Changes in land management will depend on the agreement of landowners. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.












Indicators to be included in policy unit 4 implementation plan are: Economic - Balance of annual river channel and flood defence maintenance expenditure (£) to annual average

damages from fluvial flooding to agriculture (£). - Flood damages downstream in policy units 5 (Worthing) and 7 (Shoreham and Adur Estuary) (£). Social - Number of people affected by the 1% annual probability flood event downstream in policy units 5

(Worthing) and 7 (Shoreham and Adur Estuary). - The estimated number of properties affected by Downland ‘muddy’ surface water flooding

downstream in policy unit 5 (Worthing). Environmental - Landscape character assessment of the AONB, ESA and proposed National Park.


Policy unit 5 Worthing










Policy unit 5 - Worthing


Defences: There is 6.5km of culverted channel on the Ferring Rife and Teville Stream in this policy unit Flood warning: This policy unit is covered by the Lower Ferring Rife at south Ferring the Upper Ferring Rife at north Ferring Flood Warning Areas. The Teville Stream is not covered by a Flood Warning Area. There are over 210 properties in this policy unit connected to the flood warnings direct service. Maintenance: The flapped outfalls to the sea on the Ferring Rife and Teville Stream are maintained. We carry out river channel maintenance, culvert clearance and maintenance of key surface water storage areas, such as Brooklands Lake. There are also coastal defences in this policy unit. The estimated cost of maintaining the channels and existing defences under the Environment Agency’s responsibility is approximately £90,000.


Standard of protection: Standard of protection offered by the storage pond, Brooklands Lake, is unknown.




outline*

Residential properties 2 52 502 Commercial properties 0 0 23 Population 5 124 1200 Property damages £66,950 £1.646 million N/A Agricultural damages £1,565 £1,565 N/A A roads 0.09 km 0.09 km 1.17 km Railways 0.002 km 0.08 km 0.7 km Agricultural land Grade 1 0.01 km

2 0.01 km

2 0.26 km

2


2 0.22 km

2


2 0.06 km

2


2 0 km

2


2 0 km

2


2 0.13 km

2

SSSI 0 km2 0 km

2 0 km

2

Listed Buildings 0 1 1 SM 0 0 0 AONB 0km

2 0.02 km

2 0.04 km

2

ESA 0 km2 0 km

2 0.04 km

2


0 km2 0 km

2 0 km

2


2 0.04 km

2




Economic and social receptors: There is a flood risk to people, properties and infrastructure from fluvial flooding, surface water flooding and groundwater flooding in the urban areas of this policy unit. Currently approximately 50 properties within the Ferring area are at risk of fluvial flooding from the Ferring Rife, from the 1% annual probability fluvial flood event. A short length of the A2032 and A259 to the north west of Worthing and the railway line in the north of Ferring are at risk of flooding for the 1% annual probability flood event. The A27 was closed for a period of time due to groundwater flooding during the 2000 flood event. A very small area of agricultural land (grades 1 and 2, excellent and very good) is at risk of flooding for the 1% annual probability flood event. Environmental designations: There are no internationally or nationally designated sites or SSSIs at risk of flooding for the 1% annual probability flood event within this policy unit.


Approximately 0.04km2 of the Ferring SNCI is located within the 1% annual

probability flood event outline in this policy unit. The sensitivity of this site to flooding is low. Landscape: The Sussex Downs AONB, South Downs ESA and proposed National Park are within this policy unit, however, only a small portion of the AONB and none of the ESA or proposed National Park are located within the 1% annual probability flood event outline; less than 0.05km

2 is within the 0.1% annual probability flood event

outline. Natural and Historic Environment: There is one listed building located within the 1% annual probability flood outline. There is no extent of registered historic parks and gardens and no SMs at risk of flooding for any of the considered annual probability flood events.


Sea level rise and increased storminess as a result of climate change*. *To represent future sea level rise, the tidal boundary within the broadscale model was scaled to



There is a small increase (approximately £0.04 million) in AAD due to climate change over the next 100 years. In 100 years approximately 60 properties are at risk of flooding from the Ferring Rife from the 1% annual probability fluvial flood event. Surface water flooding incidents are also likely to increase in frequency and severity due to climate change (increased rainfall).


There is potential to reduce flood risk through changes in land use by reducing run-off in the catchment. There is potential to limit increased run-off from new development by installation of SuDS. And also the prevention of vulnerable development in flood risk areas.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties. Flood risk from the sea is also a significant consideration in this policy unit. Therefore, fluvial flood risk management options must fit with shoreline management plan policy and actions.

The following tables provide a summary of how flooding may change in response to flood management options which may be adopted within the policy unit and what the implications of these changes might be. We have not applied any specific measures or schemes to the policy unit, but have applied what has been termed a ‘generic response’. This represents the most likely outcome of a given policy, but is not specific and does not reflect any proposed scheme or project. It simply allows a broad assessment of what the impact of that policy might be.

A broadscale model has been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages. The results given below for each of the generic responses and the basecase are for the 1% annual probability flood event.




damages (£m)

Change in land use has been applied to the upper parts of this Ferring Rife catchment within the broadscale model. The results show a small reduction in flood damages within this policy unit of approximately 12%.



% change = -12%

Conclusions

Although the impact of flood risk from changing land use in the upper catchment is not large, it is nonetheless significant. Together with other downstream measures, land use change in the upper catchment can provide a useful way of reducing flood risk in this policy unit.

Generic response: Attenuation/retention (storage) on the Ferring Rife


damages (£m)

The broadscale modelling has indicated that applying flood storage in the upper catchment of the Ferring Rife (of no specific size or location) has a negative effect on flood damages within this policy unit (approximately £0.443 million increase in flood damages). The results show a 24% increase in flood damages for the 1% annual probability fluvial flood event.



% change = +24%

Conclusions

A large flood storage reservoir on the upper parts of the Ferring Rife catchment will provide little benefit to Ferring. The Ferring Rife is affected by tide locking at the bottom end of the catchment and therefore flood damages would be reduced if additional storage for flood water was made available within Ferring itself.



Policy unit 5 – Worthing













reduced.




networks.



unpredictable way.





place.





place.

Maintenance of the surface water and

urban drainage networks continue.


of watercourses.

Some localised protection measures

introduced.


Improvements to the


networks.

Significant improvement in the

level of channel maintenance of watercourses.

Significant localised protection measures

introduced.


Upgrade of surface

water and urban drainage networks to increase capacity and


future.

There is potential to increase water

retention by introducing flood

storage areas along the Ferring Rife.

Economic objectives


increase in Worthing due to future change (urban


Targets No significant increase in damages in Worthing

from fluvial, surface water and urban

drainage flooding due to future changes (urban


Indicators




water and groundwater flooding (£).

*Estimation based on historical

damages observed in the Brighton area from the 2000/

2001 flood event (Binnie Black & Veatch 2001 – Flood Defence

Assessment of Downland Flooding).


advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Worthing).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Worthing.





damages from fluvial flooding and estimated


flooding are approximately £70,000

and around £4,000 respectively.

This increases to

around £108,000 for total annual average damages from fluvial

flooding and more than £5,000 for

estimated surface water damages in the

future.


drainage networks would lead to a

significant increase in flooding with total annual average


estimated damages resulting from surface water flooding being

significantly more than £180,000 and more than £10,000

respectively.

As channels and drainage networks

decrease in capacity and condition due to


average damages from fluvial flooding and estimated damages


increase to be more than £145,000 and more than £7,000

respectively.


from fluvial flooding and estimated


flooding will increase slightly over time due

to the affects of climate change to be around £108,000 and




total annual average damages from fluvial

flooding and estimated damages resulting from surface water flooding

will remain are approximately £70,000

and £4,000.

Significant improvements in

channel maintenance,

localised protection measures and

upgrading of the drainage network would reduce total


flooding and the estimated damages

resulting from surface water flooding to be

minimal.

The results of broadscale modelling

has indicated that applying flood storage

in the upper catchment of the

Ferring Rife (of no specific size or location) has a

negative effect on flood damages within this policy unit with a 24% increase in flood damages for the 1%


Therefore annual

average damages are likely to be more than

£70,000 and the estimated damages

resulting from surface water flooding may also remain around

£4,000.

However damages may decrease if

additional storage is provided within the

Ferring Rife.










Indicators















from fluvial flooding to property are currently


£107,900 in the future.







to be more than £180,000.







£145,000.





from fluvial flooding to property increase over time due to the affects of climate change to be around £107,900.

With better

maintenance efficiency and

effective use of funding the balance of

expenditure to damages will remain

acceptable.

The level of f channel and flood defence





property will remain around £69,800.






Annual average damages from fluvial flooding to property are estimated to be less than £8,000.




maintenance expenditure is likely to

be slightly less than £90,000, however, the broadscale modelling has indicated that by

applying flood storage in the upper

catchment of the Ferring Rife there will

be an increase in flood damages to more than

£70,000.

However, this may not be the case if storage was provided within

the Ferring Rife.


damages is uncertain.

Social objectives


property does not significantly increase in Worthing in the future.


the 1% annual probability fluvial flood event or surface water flooding in Worthing in

the future.

Indicators Number of people and properties affected by


event.

The estimated number of properties affected by

surface water and groundwater flooding.

*Surface water/ groundater flooding estimates based on

historical records.




- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Worthing.

- Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings Direct service by installing new level gauges on the Teville stream.

- Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill.

- Influence the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring Rife, to improve the sustainability of flood risk management in the this area.




- CFMP objectives and policies must complement those of the SMP that affect the CFMP area.




flood event. This increases slightly to around 140 people and 59 properties in

the future.

There are some historic records of

surface water flooding in this area but they are limited and we

have not been able to estimate the number of properties affected

by surface water flooding from these

accounts.

However, surface water flooding is a


An estimated 272

properties are currently covered by a flood warning service.






drainage flooding.

The number of people and properties

at risk of localise fluvial flooding will

increase to be significantly more than 140 and 59

respectively.

There will be a significant increase









flooding.




respectively.

There will be a substantial increase





remains in place.



current level.


of localised fluvial flooding is likely to slightly increase to approximately 140

and 59 respectively.



flooding will gradually increase from the

current level due to the affects of climate

change.






52 respectively.


surface water and urban drainage will

remain at the current level.





defence works and flood warning service

will reduce the number of people

affected by localised fluvial flooding to less than 15 and number of properties affected

to less than 5.


drainage flooding.


and coverage





negative effect within the catchment.


the Ferring Rife.

It is uncertain how this policy option would

influence the number of people and

properties affected by the 1% annual


Flood Warning Service is retained at

the current level



infrastructure does not increase in Worthing in

the future.


line or increase in extent of critical infrastructure

flooded, in Worthing and surrounding areas, from a 1% annual probability

fluvial flood event or surface water flooding.

Indicators

Length of A road and railway line (km) affected

by the 1% annual probability fluvial flood

event.






water flooding*.

*Surface water/ groundwater flooding estimates based on

historical records.






- Visual impact of flood risk management activities within the proposed National Park or Areas of outstanding Natural Beauty.

- CFMP objectives and policies must complement those of the Shoreline Management Plan (SMP) that affects the CFMP area.

Currently approximately 0.09km of A road and 0.08km

of railway, but no critical infrastructure sites are affected by

the 1% annual probability flood event. The extent of road and railway affected by the 1% annual probability fluvial flood event is expected to increase in the future to more than 1km and 0.5km

respectively. No critical infrastructure sites are at risk in the

future.

There are historic records of closure and

disruption of A road (A24 and A 27)/ rail

links and one hospital being affected by surface water and


Surface water and






depth of localised fluvial and surface

and urban drainage flooding.

Significantly more

than 1km of A road and 0.5km of railway are likely to be at risk

of flooding from fluvial flooding during


event. No critical

infrastructure sites are at risk of fluvial

flooding from the 1% annual probability

flood event.


urban drainage flooding (extent and/

or frequency) of A roads, railway and

critical infrastructure sites will occur.





flooding.

More than 1km of A road and 0.5km of

railway are likely to be at risk of flooding from fluvial flooding during


No critical infrastructure sites are at risk of fluvial flooding

from the 1% annual probability flood event.

More surface water and urban drainage

flooding (extent and/ or frequency) of A roads,

railway and critical infrastructure sites will

occur.



current level.

Approximately 1km of A road and 0.5km of

railway are affected by flooding during the 1%

annual probability flood event. No

critical infrastructure sites are at risk of

fluvial flooding from the 1% annual


There is likely to be a gradual increase in

extent and/ or frequency from the current level of A


risk of surface water and urban drainage flooding due to the affects of climate

change.



Approximately 0.09km of A road and 0.08km

of railway but no critical infrastructure sites are

affected by flooding during the 1% annual




flooding with some disruption from closure

of road and rail links and one hospital being

affected.



upgrading of the drainage network will

reduce fluvial and surface water and



railway or critical infrastructure sites will be affected by fluvial or surface water and urban

drainage flooding.





negative effect within the catchment.


the Ferring Rife.

It is uncertain how this policy option would affect the extent of

fluvial, surface water and urban drainage flooding to A roads, railways and critical infrastructure sites.

Reduce the impact of muddy flooding in northern parts of

Worthing, including Findon.

Targets Reduction in the number of properties affected by

muddy flooding in northern parts of

Worthing, including Findon.

Indicators

The estimated number of properties affected by

Downland ‘muddy’ surface water flooding.

* Estimates of properties

affected by muddy flooding based on historical records.

Opportunities - Reduce surface water run-off

and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices.

- Support the existing flood defence measures in relation to surface water flooding.



- A suitable level of productivity from agricultural land needs to be retained.


There are no definitive historic records of

‘muddy’ surface water flooding for this policy unit and therefore we have not been able to estimate the number of properties affected or the impacts from this type of flooding.

However, ‘muddy’ flooding is a known problem in this area


The impacts of ‘muddy’ flooding will significantly increase

with a significant number of additional

properties being affected by this type

of flooding.

The impacts of ‘muddy’ flooding will increase

with a decrease in maintenance of

watercourses and drainage networks.

There will be a gradual increase in

the impact of ‘muddy’ flooding due to the affects of climate

change. Flooding is likely to occur more

frequently, to a greater depth, and additional

properties may be affected.

The impact of ‘muddy’ flooding will remain at

the current level as improvements in maintenance and

localised protection measures mitigate the

affects of climate change.

With increased maintenance and

local defence works there are no incidents or associated impacts of ‘muddy’ flooding.

The provision of flood storage associated

with the Ferring Rife is not likely to have any affect on the impacts of ‘muddy’ flooding.


Protect and enhance the Ferring Rife and

Meadows Site of Nature Conservation Importance.


Ferring Rife and Meadows Site of Nature


Indicators






- Changes to flood risk


2 of the Ferring

Rife and Meadows SNCI located within

the 1% annual probability flood event

outline.

This is likely to increase to around

Doing nothing and with a reduction in the height of the

embankments the Ferring Rife would

flood more frequently and to increased

flood depths. The area of the SNCI

within the 1% annual


channels would eventually allow the Ferring Rife to flood more frequently, with an increase in flood

depths, increasing the area of the SNCI within

the 1% annual

There would be a slight increase to

approximately 0.1km2

in the area of the SNCI within the 1% annual probability

flood event outline due to the affects of climate change.



There will be no




upgrading of the drainage network is likely to reduce the

extent of flooding and therefore the extent

of the SNCI within the

Increasing the flood storage areas in this

policy unit would increase the potential to increase the area of

SNCI to more than 0.5km

2 and improve or

increase the habitat types and species

diversity in a managed


management can affect the landscape, its character and value as an amenity.


0.1km2 in the future,

with a small increase in habitat and species

diversity.

probability flood outline increases to significantly more

than 0.1km2.

There is increased

potential to significantly improve




probability flood outline to more than 0.1km

2.

There is increased



There is likely to be a small increase in

habitat and species diversity.

SNCI. 1% annual probability flood outline to less

than 0.04km2.


depth) is likely to have a negative

affect on the habitat types and species diversity within the

SNCI.

and controlled way.

Does this policy change flood risk locally or elsewhere: Unlikely to affect adjacent policy

units

Unlikely to affect adjacent policy units



Unlikely to affect adjacent policy

units





Policy Unit 5 - Worthing


Policy option P1

Environmental

Social

Economic

NO LOSSES

HIGH-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by significantly more than 16 and 7 respectively



� The lengths of A road and railway at risk from a 1% AEP flood event will increase by significantly more than 0.91km and 0.42km respectively

� Significantly more surface water and urban drainage flooding to transport routes will occur

� The impact of ‘muddy’ flooding will increase significantly

HIGH-

� The AAD to properties and agricultural land

HIGH+

� The area of the Ferring Rife and Meadows SNCI will significantly increase by significantly more than 0.96km

2 but in an


NEUTRAL=

� The number of critical infrastructure at risk from a 1% AEP flood event will remain at 0

NO GAINS

Not preferred option – There are limited gains under this policy option. The numbers of people and properties adversely affected by removing FRM are unacceptably high. The AAD and level of disruption caused by flooding are also high and the environmental effects are unpredictable due to the unmanaged and uncontrolled nature of this policy option.


caused by fluvial flooding will increase by significantly more than £110,000

� AAD to properties and agricultural land caused by surface water flooding will increase by significantly more than £6,000


Policy option P2

Environmental

Social

Economic

NO LOSSES

HIGH-


� The number of properties at risk of surface water and urban drainage flooding will increase substantially

� The lengths of A road and railway at risk from a 1% AEP flood event will increase by more than 0.91km and 0.42km respectively

� Substantially more surface water and urban drainage flooding to transport routes will occur

� The impact of ‘muddy’ flooding will increase substantially

HIGH-

HIGH+

� The area of the Ferring Rife and Meadows SNCI will significantly increase by more than 0.96km

2

but in an unmanaged way

NEUTRAL=


NO GAINS



� The AAD to properties and agricultural land caused by fluvial flooding will increase by more than £75,000

� AAD to properties and agricultural land caused by surface water flooding will increase by more than £3,000


Policy option P3

Environmental

Social

Economic

NO LOSSES

MEDIUM-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by approximately 16 and 7 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase slightly

� The lengths of A road and railway at risk from a 1% AEP flood event will increase by approximately 0.91km and 0.42km respectively

� More surface water and urban drainage flooding to transport routes will occur in the future

� The impact of ‘muddy’ flooding will increase in the future

MEDIUM-

� The AAD to properties

MEDIUM+

� The area of the Ferring Rife and Meadows SNCI will increase by approximately 0.96km

2

with a small increase in habitat and species diversity

NEUTRAL=


LOW+

� The balance of FRM expenditure to AAD

Preferred Policy Option – Although there are some losses in terms of the numbers if people and properties and the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change.


and agricultural land caused by fluvial flooding will increase by approximately £38,000

� AAD to properties and agricultural land caused by surface water flooding will increase by approximately £1,000

will remain acceptable with AAD to properties and agricultural land increasing slightly in the future

Policy option P4

Environmental

Social

NO LOSSES

NO LOSSES

LOW+

� The area of the Ferring Rife and Meadows SNCI will not increase in the future with no notable change in habitat and species diversity

HIGH+



� The lengths of A road and railway at risk from a 1% AEP flood event will not increase in the future

� Surface water and urban drainage flooding to transport routes will not increase in the future

LOW+

� The impact of ‘muddy’ flooding will remain at current levels

NEUTRAL=


Not preferred option – Although there are additional benefits in terms of the numbers of people and properties and reducing the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change. It should therefore be unnecessary to further increase FRM in this policy unit in order to ensure risk does not increase.


Economic NO LOSSES HIGH+



� The balance of FRM expenditure to AAD will remain acceptable with slight increases in FRM expenditure to maintain AAD to properties and agricultural land at current levels in the future

Policy option P5

Environmental

Social

MEDIUM-

� The area of the Ferring Rife and Meadows SNCI will be reduced with a possible decline in habitat and species diversity

NO LOSSES

NO GAINS

HIGH+

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will be reduced by more than 109 and 47 respectively


� The lengths of A road and railway at risk from a 1% AEP flood event will be reduced

� Surface water and urban drainage flooding to transport routes will be reduced

� The impact of ‘muddy’ flooding will be minimised as far as possible

Not preferred option – Although there are significant gains in terms of reducing the numbers of people and properties affected by flooding, the costs of implementing increased FRM now and in the future are considered unacceptable. There are also losses to the environment.


Economic

HIGH-

� The balance of FRM expenditure to AAD is unacceptable with significant increases in FRM expenditure to reduce AAD to properties and agricultural land

NEUTRAL=


HIGH+

� The AAD to properties and agricultural land caused by fluvial flooding will be reduced

� AAD to properties and agricultural land caused by surface water flooding will be minimal

Policy option P6

Environmental

Social

Economic

NO LOSSES

LOW-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event are likely to be increased

� The number of properties at risk of surface water and urban drainage flooding is uncertain

� The lengths of A road and railway at risk from a 1% AEP flood event are uncertain

� The extents of surface water and urban drainage flooding to transport routes are uncertain

LOW-

� The AAD to properties and agricultural land caused by fluvial flooding are likely to increase

� The balance of FRM

MEDIUM+

� The area of the Ferring Rife and Meadows SNCI will increase by more than 0.46km

2 but in a

managed and controlled way

NEUTRAL=


� Flood storage is not likely to have any effect on ‘muddy’

MEDIUM+

� AAD to properties and agricultural land caused by surface water flooding will not increase in the future and may be reduced

Not preferred option – Although there are moderate gains in terms of the environment and AAD to properties and agricultural land, there are also losses associated with the numbers of people and properties affected by flooding and the balance of expenditure. In addition to this, the effects listed here are relatively uncertain.


expenditure to AAD is uncertain with reductions in FRM expenditure and likely increases in AAD to properties and agricultural land

Key

HIGH:


MEDIUM:


LOW:



HIGH:


MEDIUM:

Medium positive A policy has a ‘medium positive’ effect where it could contribute to a social, economic or environmental objective in a positive way. A ‘medium positive’ effect could be: (i) a reduction in current flood risk;


(ii) avoiding/reducing projected increases in flood risk under future conditions, and/or; (iii) additional social, economic and/or environmental gains.

LOW:





Physical characteristics: - Largely an urban unit, including Worthing, Lancing and parts of Littlehampton. - Urban centres are separated by the Ferring Rife and Teville Stream floodplains. - Geology mainly comprises Chalk formation, which is dissected by Lambeth Group

clays through the centre of the policy unit. - Small pockets of high grade agricultural land (grades 1 and 2) lie just north of

Worthing and in Sompting, at the foot of the South Downs. - Low-lying topography across the whole coastal plain region.

Flood mechanism - Combination of groundwater, surface water run-off and fluvial flooding from the

Ferring Rife. Receptor:

- People, properties and infrastructure in the urban areas. The A27, a main transport route, is susceptible to groundwater and surface water flooding.

- Currently approximately 52 properties at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event in the Ferring Rife area.

- In 100 years approximately 60 properties at risk of flooding in the Ferring Rife area. - There are many more properties at risk from fluvial, surface water and groundwater

flooding in Sompting – the exact number is unknown. Current Flood Risk Summary




- Flood risk in the Ferring Rife area is currently assessed as low to medium, assessment remains unchanged as a result of future scenarios.

- We are uncertain of the exact impact of flooding in the Teville Stream area, but it is predicted that a combination of groundwater flooding, surface water run-off and/or fluvial flooding could result in a flood event flooding the low-lying areas of Sompting. It is also predicted that future scenarios will increase this risk, however, the extent to which this increase affects the people, property and environment in the Teville Stream area is unknown.




Problem/risk



Justification

This policy is appropriate where the current level of flood risk management is considered appropriate. Current management and maintenance activities include maintaining defences, grass and weed cutting, debris removal and inspections. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low to medium and it is not expected to significantly

increase in the future. - The current flood risk management activities, carried out for the localised fluvial and

surface water and urban drainage flooding problems, are considered appropriate and acceptable for the level of risk.



- Ensure flood damages do not significantly increase in Worthing due to future change (urban development and climate change).


- Ensure the impact of flooding on people and property does not significantly increase in Worthing in the future.

- Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Worthing in the future.

- Reduce the impact of muddy flooding in northern parts of Worthing, including Findon. - Protect and enhance the Ferring Rife and Meadows Site of Nature Conservation

Importance.




development proposed in the South East Plan (e.g. Worthing). - Reduce flood risk and improve water quality by promoting and encourage the use of

SuDS in the proposed urban developments in Worthing. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit

to flood risk through reducing the run-off rate. - Investigate the feasibility of incorporating the Teville Stream into the Floodline Warnings

Direct service by installing new level gauges on the Teville stream. - Continued practice and development of the Emergency Response Plan in Brighton and

Hove, Worthing, Shoreham, and Burgess Hill. - Influence the coastal defence strategy, along the Lower Adur, Teville Stream and Ferring

Rife, to improve the sustainability of flood risk management in this area. - Reduce surface water run-off and soil erosion by supporting the existing and future

management policies regarding environmentally sensitive farming practices. - Support the existing flood defence measures in relation to surface water flooding. - Help meet national biodiversity action plan (BAP) targets. Constraints: - Government and international legislation, environmental management policies, plans and




Areas of Outstanding Natural Beauty. - CFMP objectives and policies must complement those of the Shoreline Management

Plan (SMP) that affects the CFMP area. - Transport links in the catchment are a vital part of the communication network regionally,


- A suitable level of productivity from agricultural land needs to be retained. - Some environmentally designated habitats are susceptible to changes in flood


an amenity.


Policy 1 - do nothing. The urban areas of Worthing currently have a low level of risk of fluvial flooding and the risk of flooding from surface water and rivers may increase with climate change. Without continued maintenance the annual average damages would increase to more than £180,000. Do nothing is, therefore, not an appropriate policy. Policy 2 - reduce current level of flood risk management. As with policy option 1, the annual average damages would increase to more than £145,000 and would become unacceptable in the future under a ‘do less’ policy. Policy 4 – maintain the current level of flood risk into the future. This policy unit could also apply, however, it implies considerable increased flood risk management in the future. The need for this has not been identified or considered justifiable. Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified. Policy 6 - increase flooding to reduce flooding elsewhere. There are no opportunities within this policy unit for this policy.


We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.


Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties. The extent of fluvial flooding and the potential consequences are uncertain for the Teville Stream. Although broad conclusions may be drawn, the lack of sufficient data to model the watercourse limits the analysis that can be completed in the CFMP. The figures presented in this table for fluvial flooding relate to the Ferring Rife.











Policy unit 5 – Worthing

Indicators to be included in policy unit 5 implementation plan are: Economic - Total annual average damages (to properties and agriculture) from fluvial flooding (£AAD). - Estimated damages resulting from surface water and groundwater flooding (£) (based on historical

damages). - Balance of annual river channel and flood defence maintenance expenditure (£) to annual average

damages from fluvial flooding to property (£). Social - Number of people and properties affected by the 1% annual probability fluvial flood event. - The estimated number of properties affected by surface water and groundwater flooding (based on

historical records). - Length of A road and railway line (km) affected by the 1% annual probability fluvial flood event. - Number of critical infrastructure sites affected by the 1% annual probability fluvial flood event. - Number and period of recorded A road and railway closures due to surface water flooding (based

on historical records). - Number of critical infrastructure sites recorded as being affected by surface water flooding (based

on historical records). - The estimated number of properties affected by Downland ‘muddy’ surface water flooding (based

on historical records). Environmental - Habitat quality and species diversity.


Policy unit 6 Brighton and Hove










Policy unit 6 – Brighton and Hove


Defences: There are no formal Environment Agency fluvial flood defence schemes in this policy unit. There are sections of informal raised defences owned by Brighton and Hove City Council for surface water management. Flood warning: This policy unit is not covered by a Flood Warning Area as it does not suffer from fluvial flooding. There are no properties connected to the flood warnings direct service. Maintenance: Surface water and groundwater events as large as the 2000/ 2001 event trigger significant emergency works, with a total estimated expenditure of around £0.4 million.


Standard of protection: There are no flood defence schemes in this policy unit.




outline* Residential properties 0 0 N/A Commercial properties 0 0 N/A Population 0 0 N/A Property damages 0 0 N/A Agricultural damages 0 0 N/A A roads 0 km 0 km 0 km Railways 0 km 0 km 0 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2


2 0 km

2


2 0 km

2


2 0 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0 km

2

SSSI 0 km2 0 km

2 0 km

2

Listed Buildings 0 0 0** SM 0 0 0 AONB 0 km

2 0 km

2 0 km

2

ESA 0 km2 0 km

2 0 km

2


0 km2 0 km

2 0 km

2


2 0 km

2


* 10% and 1% based on broadscale model results and 0.1% based on Flood Zone 2 **Several listed buildings are at risk from tidal flooding based on Flood Zone 2


Economic and social receptors: Currently there are no properties or people at risk of fluvial flooding in Brighton and Hove from the 10%, 1% or 0.1% annual probability flood event. No extent of A road, railway line or graded agricultural land lies within any of the considered annual probability flood event outlines. Tourist infrastructure and amenities are not at risk of flooding from the 10%, 1% or 0.1% annual probability flood events. Environmental designations: There are no internationally or nationally designated sites, SSSIs or SNCIs at risk of flooding for the 1% annual probability flood event within this policy unit. Landscape: The Sussex Downs AONB and the South Downs ESA and proposed National Park is located within this policy unit, however none of these areas are located within the 1% annual probability flood event outline. Natural and Historic Environment: There are no listed buildings, registered historic parks and gardens or SMs at risk of fluvial flooding for the considered annual probability flood events in this policy unit.



Climate change (increased rainfall).


It is predicted that climate change will increase the flood risk in this policy unit, however, the extent to which this increase affects the people, property and environment in Brighton and Hove is unknown.


There is potential to limit increased run-off from new development by installation of SuDS and reduce or maintain current runoff from the south Downs in the future through the adoption of agri-environmental schemes. There is also potential to provide integrated urban drainage solutions to reduce urban flooding. And also the prevention of vulnerable development in flood risk areas.


Flood risk from the sea is also a significant consideration in this policy unit. Therefore, fluvial flood risk management options must complement shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change. Our current ability to accurately predict the impact of climate change, particularly the impact it will have on groundwater flooding, is limited.

The main sources of flooding for this policy unit are groundwater and surface water run-off. We have not been able to model these processes and it has therefore not been possible to define generic responses in this policy unit.















networks.



unpredictable way.





Continued support of

groundwater and surface water flooding studies and research such as the Flood 1

project.


Improvements to the


networks.


Upgrade of surface



future.


unit.

Economic objectives


increase in Brighton and Hove due to future

change (urban development and climate change).

Targets No significant increase in damages in Brighton and Hove from surface water (including urban drainage flooding) and

groundwater due to future changes (urban


Indicators








advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Brighton and Hove.





The estimated damages resulting from surface water and groundwater

flooding is currently approximately £1.4

million. This is likely to increase to slightly more than £1.4 million

in the future.

No maintenance of drainage networks and surface water

management schemes would lead

to a significant increase in flooding

with estimated damages resulting from surface water and groundwater

flooding being significantly more than £1.4 million.

As drainage networks and surface water

management schemes decrease in condition

due to reduced maintenance the


water and groundwater flooding will increase to

be more than £1.4 million.

The estimated damages resulting from surface water and groundwater

flooding will increase over time due to the

affects of climate change to be slightly

more than £1.4 million.

Improved drainage networks and localised

surface water protection measures



water and groundwater flooding will remain at

approximately £1.4 million.

Increased local defence works and

upgrading of the drainage network would reduce the


water and groundwater flooding

to be minimal.

Not applicable.

Ensure that expenditure on emergency surface water and groundwater

flooding works is appropriate to the


water and groundwater flooding.

Targets Maintain a suitable level

of emergency works expenditure when

compared to estimated damages resulting from

surface water and groundwater flooding

(£).

Indicators Balance of emergency works expenditure to estimated* damages resulting from surface


*Estimation based on historical damages

observed in the Brighton









The current estimated emergency work

expenditure is approximately £0.4

million; the estimated damages resulting from surface water and groundwater

flooding are currently around £1.4 million, increasing to slightly

more than £1.4 million in the future.

The current balance of


No maintenance of drainage networks and surface water

management schemes would lead

to a significant increase in flooding. No expenditure is

incurred as no emergency work is

undertaken. Estimated damages

resulting from surface water and

groundwater flooding increase to be

significantly more than £1.4 million. The balance of expenditure to

Emergency work is reduced with

expenditure reducing to less than £0.2 million. Estimated damages

resulting from surface water and groundwater flooding are likely to be substantially more than

£1.4 million. The balance of expenditure

to damages is unacceptable.

The level of emergency work

remains at the current level with an

estimated expenditure of approximately £0.4

million. Estimated damages resulting from surface water and groundwater

flooding are likely to increase gradually

over time due to the affects of climate

change to be slightly more than £1.4

million. The balance of expenditure to

damages will initially remain acceptable but

Improved drainage networks and localised

surface water protection measures


Due to this the level of emergency works and estimated damages

remains the same are around £0.4 million and

£1.4 million respectively.




upgrading of the drainage network would reduce both

the level of emergency work and

estimated flood damages to be minimal. The

balance of emergency work expenditure to

damages will be acceptable.

Not applicable.


area from the 2000/ 2001 flood event (Binnie Black &

Veatch 2001 – Flood Defence Assessment of

Downland Flooding).


may become unacceptable over

time.

Social objectives

Ensure the impact of surface water and

groundwater flooding on properties does not

significantly increase in Brighton and Hove in the

future.

Targets No significant increase

in the number of properties affected by

surface and groundwater flooding in Brighton and

Hove in the future.

Indicators The estimated* number of properties affected by



historical records.



advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Brighton and Hove.

- Continue local authority and Environment Agency support of the Flood 1 project in relation to groundwater flooding.

- Develop a flood warning system for groundwater flooding.

- Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, Shoreham, and Burgess Hill.





An estimated 50 properties are at risk of surface water and

groundwater flooding. This is likely to

increase to between 50 and 200 properties

in the future.

There is currently no flood warning service in Brighton and Hove.

No maintenance of drainage networks would result in an


depth of surface water and

groundwater flooding.

The estimated number of properties

at risk of surface water and

groundwater flooding is likely to increase to

more than 600.

No Flood Warning Service provided



increase in the frequency, extent and depth of surface water

and groundwater flooding.


surface water and groundwater flooding is

likely to increase to more than 350.

No Flood Warning Service provided

Maintenance of drainage networks

continues at the current level.


surface water and groundwater is likely

to increase to between 50 and 210.

No Flood Warning

Service provided but option continues to be

explored for groundwater flooding.

Improved drainage networks and localised protection measures



surface water and groundwater will

remain at around 50.

Groundwater Flood Warning Service

provided.



reduce the number of properties at risk of surface water and

groundwater flooding to zero.

No Groundwater Flood Warning

Service required.

Not applicable.


infrastructure does not increase in Brighton and

Hove in the future.

Targets No increase in the number of critical

infrastructure sites affected by surface

water and groundwater flooding in Brighton and Hove and surrounding

areas.

Indicators Number and period of recorded A road and

railway closures due to surface water and

groundwater flooding*.



and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council).

- Support the existing flood defence measures in relation to surface water flooding, such as bunds provided by Brighton and Hove City Council.

- Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Brighton and Hove).


- Develop a flood warning

There are records of disruption and closure

of road/ rail links including the A23,

Lewes Road and the main Brighton to

London railway line. In addition two schools

and a community centre are also

recorded as having been affected by

surface water flooding.

Records indicate that surface water flooding

persists for a significant period of

time (up to and more than two weeks).

No maintenance of drainage networks would result in an


depth of surface water and



groundwater flooding of A roads, railway

and critical infrastructure sites

will occur and persist for a significantly

longer time period.



increase in the frequency, extent and depth of surface water


More surface water and groundwater

flooding of A roads, railway and critical

infrastructure sites will occur and persist for a

longer time period.

Maintenance of drainage networks

continues at the current level.

There is likely to be a gradual increase from the current extent of A


risk of surface water and groundwater

flooding due to the affects of climate

change. Flooding is likely to persist for a longer time period.

Improved drainage networks and localised protection measures



surface water and groundwater flooding with disruption and closures of the A23, Lewes Road and the

main Brighton to London railway line;

schools remain likely to be a affected.


upgrading of the drainage network will reduce surface water



railway or critical infrastructure sites will be affected by surface water and


Not applicable.


water and groundwater flooding*.


historical records.

system for groundwater flooding.





Surface water and groundwater flooding is a known problem in this area and it is likely

to increase in the future.

Reduce the impact of muddy flooding in northern parts of

Brighton and Hove, Rottingdean,

Woodingdean, Ovingdean and

Bevendean.

Targets Reduction in the number of properties affected by

muddy flooding in northern parts of

Brighton and Hove, Rottingdean,

Woodingdean, Ovingdean and

Bevendean.

Indicators The estimated* number of properties affected by

Downland ‘muddy’ surface water flooding*.

* Estimates of properties

affected by muddy flooding based on historical records.


and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council).




- A suitable level of productivity from agricultural land needs to be retained.

- Visual impact of flood risk management activities within the proposed National park or Areas of Outstanding Natural Beauty.

An estimated 25 properties are

currently affected by ‘muddy’ surface water flooding. This is likely to increase to between

25 and 150 approximately

properties in the future.

The impacts of ‘muddy’ flooding will

increase with between 25 and 175

properties being affected by this type

of flooding.

The impacts of ‘muddy’ flooding will increase

with a decrease in maintenance of

watercourses and drainage networks.

The number of properties affected will increase to between 25

and 150

There will be a gradual increase in

the impact of ‘muddy’ flooding due to the affects of climate

change. Flooding is likely to occur more

frequently, to a greater depth. The estimated number of properties affected increases to between 25 and 125

The impact of ‘muddy’ flooding will remain at the current level, with

an estimated 25 properties being

affected, as improvements in maintenance and

localised protection measures mitigate the

affects of climate change.

With increased maintenance and

local defence works there are no incidents or associated impacts of ‘muddy’ flooding.

Not applicable.


There are no environmental objectives applicable to this policy

unit.


unit.


unit.
















units





units NA




Policy Unit 6 - Brighton and Hove


Policy option P1

Environmental

Social

Economic

NO LOSSES

HIGH-


� Significantly more surface water and urban drainage flooding to transport routes and critical infrastructure will occur

� The number of properties affected by ‘muddy’ flooding will increase by up to 150

HIGH-

� Estimated damages caused by surface water flooding will increase significantly

� The balance of FRM expenditure to estimated damages is unacceptable with estimated damages increasing significantly

NO GAINS

NO GAINS

NO GAINS

Not preferred option – The numbers of properties, critical infrastructure and transport routes affected by surface water flooding is unacceptably high. Estimated damages will also increase to unacceptable levels.

Policy option P2

Environmental

Social

NO LOSSES

HIGH-


� Substantially more surface water and urban

NO GAINS

NO GAINS

Not preferred option – The numbers of properties, critical infrastructure and transport routes affected by surface water flooding is unacceptably high. Estimated damages will also increase to unacceptable levels.


Economic

drainage flooding to transport routes and critical infrastructure will occur


HIGH-

� Estimated damages caused by surface water flooding will increase substantially

� The balance of FRM expenditure to estimated damages is unacceptable with estimated damages increasing substantially

NO GAINS

Policy option P3

Environmental

Social

Economic

NO LOSSES

LOW-

� The number of properties at risk of surface water and urban drainage flooding will increase by up to 160

� More surface water and urban drainage flooding to transport routes and critical infrastructure will occur


MEDIUM-

� Estimated damages caused by surface water flooding will increase

� The balance of FRM expenditure to estimated damages will become unacceptable with estimated damages increasing in the future

NO GAINS

NO GAINS

NO GAINS

Preferred Policy Option – Although there are some losses in terms of the numbers if people and properties and the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change.

Policy option P4

Environmental

Social

NO LOSSES

NO LOSSES

NO GAINS

HIGH+

Not preferred option – Although there are additional benefits in terms of the numbers of people and properties


Economic

NO LOSSES


� Surface water and urban drainage flooding to transport routes and critical infrastructure will not increase in the future

� The number of properties affected by ‘muddy’ flooding will not increase in the future

HIGH+

� Estimated damages caused by surface water flooding will not increase in the future

� The balance of FRM expenditure to estimated damages will remain acceptable with slight increases in FRM expenditure to maintain estimated damages at current levels in the future

and reducing the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change. It should therefore be unnecessary to further increase FRM in this policy unit in order to ensure risk does not increase.

Policy option P5

Environmental

Social

NO LOSSES

NO LOSSES

NO GAINS

HIGH+


� Surface water and urban drainage flooding to transport routes and critical infrastructure will be minimised as far as possible

� The number of properties affected by ‘muddy’ flooding will be reduced to 0

Not preferred option – Although there are significant additional benefits in terms of the numbers of people and properties and minimising the level of disruption and AAD caused by flooding, the overall strategy for this CFMP is to increase flood storage upstream and thereby mitigate against future increases in flood risk due to climate change. It should therefore be unnecessary to further increase FRM in this policy unit in order to ensure risk does not increase.


Economic NO LOSSES HIGH+

� Estimated damages caused by surface water flooding will be minimised

� The balance of FRM expenditure to estimated damages will be acceptable with increases in FRM expenditure to reduce estimated damages

Policy option P6

Environmental

Social

Economic


Key

HIGH:


MEDIUM:


LOW:


NEUTRAL: Neutral A policy has a ‘neutral’ effect where it makes neither a positive or negative contribution to a social, economic or environmental objective. A ‘neutral’ effect could be: (i) no change in current level of risk. In this instance the current level of risk would have to be low, so that the residual risk after a neutral policy was implemented remained acceptable; (ii) no change in flood risk under future conditions. In this instance projected future risk would need to be low so that the residual risk after a neutral policy was implemented remained acceptable, and/or; (iii) no additional social, economic and/or environmental gains or losses. Policy options may also be ‘neutral’ where they are not relevant in a particular policy unit, or where it is not feasible for a policy option to contribute to an


objective. HIGH:


MEDIUM:


LOW:





Physical characteristics: - Most densely populated policy unit, comprising Brighton and Hove, extending east

to Rottingdean. Area of regional importance to the economy. - Chalk geology predominates with small pockets of Lambeth Group clays beneath

Brighton. - There are no watercourses in this policy unit; there are however, several dry river

valleys present. Flood mechanism:

- Flashy response to surface water run-off. - Groundwater, urban drainage, and surface water flooding.

Receptor: - People, properties and infrastructure in Brighton and Hove. - Main transport routes of A23, A27 (Lewes Road) and Brighton to London train line

susceptible to groundwater and surface water flooding. Current Flood Risk Summary

Number of properties estimated to be at risk of flooding 50

Estimated damages (based on 2000/01 event) £1.4 million

Annual averages damages (approx.) -

Future Flood risk: - Flood risk from groundwater and surface water flooding is currently assessed at low

to medium; assessment remains low to medium in the future. - Anecdotal reports of rapid flooding to over 1m deep in some instances.


Number of properties at risk of flooding (1% annual probability flood event) 50 to 200

Estimated damages (based on 2000/01 event) More than £1.4

million

Problem/risk

Annual averages damages (approx.) -


Justification

This policy is appropriate where the current level of flood risk management is considered acceptable. Maintenance is minimal however assets are inspected. It is recognised that flood risk will change in the future, and management actions may change in time to gain efficiencies or improve effectiveness. This policy is appropriate for this policy unit for the following reasons: - The current level of flood risk is low to medium and it is not certain how this will increase

in the future. - The current flood risk management activities, carried out for the surface water, urban

drainage and groundwater flooding problems, are considered appropriate and acceptable for the level of risk.


- A policy 6 option for policy unit 9 will also provide benefit to Brighton and Hove in the future.


- Ensure flood damages do not significantly increase in Brighton and Hove due to future change (urban development and climate change).

- Ensure that expenditure on emergency surface water flooding works is appropriate to the estimated damages resulting from surface water flooding.

- Ensure the impact of surface water and groundwater flooding on properties does not significantly increase in Brighton and Hove in the future.

- Ensure the disruption caused by flooding to transport and critical infrastructure does not increase in Brighton and Hove in the future.

- Reduce the impact of muddy flooding in northern parts of Brighton and Hove, Rottingdean, Woodingdean, Ovingdean and Bevendean.



development proposed in the South East Plan (e.g. Brighton and Hove). - Reduce flood risk and improve water quality by promoting and encourage the use of

SuDS in the proposed urban developments in Brighton and Hove. - Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit


to flood risk through reducing the run-off rate. - Continue local authority and Environment Agency support of the Flood 1 project in

relation to groundwater flooding. - Develop a flood warning system for groundwater flooding. - Continued practice and development of the Emergency Response Plan in Brighton and


Rife, to improve the sustainability of flood risk management in the this area. - Reduce surface water run-off and soil erosion by supporting the existing and future

management policies regarding environmentally sensitive farming practices (e.g. those set out by Brighton and Hove City Council).


Constraints: - Government and international legislation, environmental management policies, plans and




- Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Transport links in the catchment are a vital part of the communication network regionally,


- A suitable level of productivity from agricultural land needs to be retained. - Visual impact of flood risk management activities within the proposed National Park or

Areas of Outstanding Natural Beauty.


Policy 1 - do nothing. This policy would not recognise the need to manage existing levels of flood risk. Policy 2 - reduce current level of flood risk management. As with policy 1, this policy would not recognise the need to manage existing levels of flood risk. Policy 4 – maintain the current level of flood risk into the future. This policy unit could also apply, however, it implies considerable increased flood risk management in the future. The need for this has not currently been identified or considered justifiable. Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is considered tolerable and therefore this policy is not justified. Policy 6 - increase flooding to reduce flood risk elsewhere. Because of the large groundwater element of the flooding, there are no opportunities within this policy unit for this approach.


Flood risk from the sea is also a significant consideration in this policy unit. Therefore, flood risk management options must fit with shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the October 2006 Defra guidance). Our current ability to accurately predict the impact of this, particularly the impact climate change will have on groundwater flooding, is limited. There is currently insufficient understanding of future flood risk from surface water and groundwater in this policy unit. The estimates made are indicative based on an assumption of increase runoff due to climate change and historic incidents of flooding. Further study into future flood risk and the cost of potential mitigation measures would facilitate more informed decision making and enable more confidence to be placed in the selected policy.












Indicators to be included in policy unit 6 implementation plan are: Economic - Estimated damages resulting from surface water and groundwater flooding (£) (based on historical

damages). - Balance of emergency works expenditure to estimated damages resulting from surface water

flooding (£) (based on historical damages). Social - The estimated number of properties affected by surface water and groundwater flooding (based on

historical records). - Number and period of recorded A road and railway closures due to surface water and groundwater

flooding (based on historical records). - Number of critical infrastructure sites recorded as being affected by surface water and groundwater

flooding (based on historical records). - The estimated number of properties affected by Downland ‘muddy’ surface water flooding (based

on historical records).


Policy unit 7 Shoreham and Adur Estuary










Policy unit 7 – Shoreham and Adur Estuary


Defences: There are 9km of raised flood defences along the River Adur on both sides of the river. The unit also includes the locked harbour that is on a spur from the east back of the River Adur. It is controlled by two harbour arms. Shingle builds against the western arm and material is by-passed eastwards to help reinforce the narrow, timber groyned beach fronting the Harbour. Other defences along the banks of the tidal Adur consist of steel sheet piled walls, reinforced concrete walls, rock groynes, shingle and earth embankments. Flood Warning: This policy unit is covered by the River Adur, downstream of Upper Beeding to Norfolk Bridge at Shoreham, fluvial Flood Warning Area and also from the coastal areas. There are more than 810 properties connected to the flood warnings direct service. Maintenance: We currently carry out annual inspection and maintenance of the tidal embankments. The estimated cost of maintaining the channels and existing defences under the Environment Agency’s responsibility is approximately £80,000.


Standard of protection: The raised embankments along the River Adur are considered to offer protection ranging from the 20% (1 in 5) to the 0.5% (1 in 200) annual probability events (fluvial and tidal). They are considered to be at or above the target condition.




outline* Residential properties 0 1 344 Commercial properties 10 10 N/A Population 0 2 822 Property damages £383,000 £383,000 N/A Agricultural damages £805 £805 N/A A roads 0.06 km 0.06 km 5.98 km Railways 0.10 km 0.10 km 2.93 km Agricultural land Grade 1 0 km

2 0 km

2 0.42 km

2


2 0.20 km

2


2 2.51 km

2


2 0 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0.09 km

2

SSSI 0.01 km2 0.01 km

2 0.5 km

2

Listed Buildings 0 0 0 SM 0 0 2 AONB 0.0004 km

2 0.0004 km

2 0.22 km

2

ESA 0 km2 0 km

2 0.04 km

2


0 km2 0 km

2 0 km

2


2 0.04 km

2




Economic and social receptors: The broadscale model results show approximately 10 properties and 2 people are at risk of tidally influenced fluvial flooding in this policy unit, for the 1% annual probability flood event. Shoreham airport and sections of the A259 are at risk of flooding from the 10% and 1% annual probability flood events; sections of the A27 are at risk of flooding from the 0.1% annual probability flood event with the around 6km of A road at risk of flooding. A short length of the railway is located within the 10% and 1% annual probability flood event outlines, this increases to almost 3km for the extreme flood event. Environmental designations: A minor extent of the Adur Estuary SSSI is located within 1% annual probability flood event outline.


No SNCIs within this policy unit are at risk of flooding during the 10% or 1% annual probability flood event. A small extent of the Widewater Lagoon SNCI is located within the extreme event flood outline. Landscape: A small extent of the Sussex Downs AONB is located within the 1% annual probability flood event outline within this policy unit. Natural and Historic Environment: There are no listed buildings, registered historic parks and gardens, SMs or natural environments (i.e. wet woodlands) at risk of flooding for the 1% annual probability flood event.


Sea level rise resulting from the effects of climate change*. Increased urbanisation will place more people and property in areas at risk. *To represent future sea level rise, the tidal boundary within the broadscale model was scaled to



There is a large increase in AAD from fluvial flooding expected due to climate change over the next 100 years from fluvial flooding alone. The number of properties at risk in the future increases to more than 1750.


Improve existing or construct new defences. This policy unit is unsuitable for large scale attenuation; small scale attenuation is unlikely to successfully manage flood risk alone as the flood risk is predominantly tidally influenced.


Flood risk from the sea is a significant consideration in this policy unit. Therefore, fluvial flood risk management options must fit with the shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change, frequency and size of storms and flood events in the future. The broadscale model has not included the drainage network through the Shoreham Airport site. This area is at risk from overtopping of the Adur and also from groundwater and surface water run-off. There is, therefore, some uncertainty in the resulting flood extent and severity – particularly in the long-term. We have taken this uncertainty into account when selecting the most appropriate policy, but we must look at this again at the next CFMP review. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.

The following tables provide a summary of how flooding may change in response to flood management options which may be adopted within the policy unit and what the implications of these changes might be. We have not applied any specific measures or schemes to the policy unit, but have applied what has been termed a ‘generic response’. This represents the most likely outcome of a given policy, but is not specific and does not reflect any proposed scheme or project. It simply allows a broad assessment of what the impact of that policy might be.

A broadscale model has been used to investigate the impact of these changes and has allowed us to quantify the effect on flood damages. The results given below for each of the generic responses and the basecase are for the 1% annual probability flood event.




damages (£m)

There is a clear reduction in flood damages in the policy units further upstream, but there is no noticeable effect in this policy unit at the downstream end of the River Adur.



% change = 0%

Conclusions

The flood mechanisms in policy unit 7 are dominated by tidal influences. The reduction in run-off rates in the upper parts of the Adur catchment has no impact on flood depths or extent within this policy unit.



damages (£m)

There is a clear reduction in flood damages in the policy units further upstream, but there is no noticeable effect in this policy unit at the downstream end of the River Adur from flood storage measure in the upper parts of the catchment.



% change = 0%

Conclusions

The flood mechanisms in policy unit 7 are dominated by tidal influences. Flood attenuation in the upper parts of the Adur catchment has no impact on flood depths or extent within this policy unit.

Generic response: Barrier across the River Adur at Shoreham


damages (£m)

This case looks at the situation where a barrier is built across the mouth of the river that keeps the tide out, but allows free discharge of the river into the sea at low tide. The modelling has shown that the reduction in flooding through this approach is significant for the 1% annual probability fluvial flood event within this policy unit, with a 100% reduction in flood damages.



% change = -100%

Conclusions

In this policy unit, this approach has shown to be effective at virtually eliminating flood damages for fluvial flooding. There is a wide and complex range of combined fluvial and tidal events that can currently result in flooding. It is therefore not possible to say with confidence what the overall effect of this option would be under different conditions.



damages (£m)

Reducing the height of the embankments along the River Adur represents the case of ‘do nothing’. The results from the modelling of this option show as expected in this policy unit, a large amount of additional flood extent and flood damage.



% change = >1,000%

Conclusions

The impact of reducing the height of the raised embankments on flooding within this policy unit is large. Flooding would occur frequently, with Shoreham being flooded by a 20% annual probability fluvial flood event.
















reduced.


reduce over time.




networks.



unpredictable way.





place.





place.




of watercourses.



Improvements to the


networks.

Construct a barrier across the River Adur within this policy unit.

Upgrade of surface



future.


unit.

Economic objectives


increase in Shoreham due to future change

(urban development and climate change).

Targets No significant increase

in damages in Shoreham from fluvial,

surface water and urban drainage flooding due to future changes (urban


Indicators










advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Shoreham).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Shoreham.

- Investigate removal of Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.



legislation, environmental management policies, plans and strategies for the catchment must be complied with, such as accommodating new housing within the catchment as detailed by the South East Plan and



approximately £77,000; this

increases to around £15 million in the

future.

There are reports of surface water flooding

to the west of the policy unit, however

these were not sufficient to enable

estimates of the damages. Surface water flooding is a



height of the embankments would lead to a significant increase in flooding


from fluvial flooding increasing to more than £20 million.

No maintenance will lead to a significant increase from the

current level of surface water flooding and

associated damages.


As channels decrease in conveyance and

capacity due to reduced maintenance

the total annual average damages from


than £17 million.

There will be a substantial increase from the current level

of surface water flooding and

associated damages with a reduction in

maintenance.


from fluvial flooding will increase over time due to the affects of climate change to be approximately £15

million.

There are limited report of surface water flooding, however, it is likely there will be an increase in surface water flooding and

associated damages due to the affects of

climate change.




damages from fluvial flooding will remain at


Surface water flooding and associated

damages will remain at the current levels due

to improvements to the drainage networks.

The construction of a barrier across the

River Adur and upgrading of surface

water and urban drainage networks would reduce total


flooding and damages from surface water flooding to be

minimal.

Not applicable.


compliance with the Habitats Directive.











Indicators















from flooding to property are currently


£15 million in the future.

The current balance of





from fluvial flooding to property increase to be more than £20

million.







£17 million.





from fluvial flooding to property increase over time due to the affects of climate change to

be around £15 million.


damages is considered to be

unacceptable.




climate change to more than £80,000. Annual average damages from

fluvial flooding to property will remain

around £77,000.

With better maintenance efficiency

and effective use of funding the balance of

expenditure to damages will remain

acceptable.




Annual average damages from fluvial flooding to property are estimated to be

£0.



Not applicable.

Social objectives


property does not significantly increase in Shoreham in the future.


the 1% annual probability fluvial flood event or surface water

flooding in Shoreham in the future.

Indicators



event.

The estimated* number of properties affected by



historical records.



advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Shoreham).

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments in Shoreham.

- Continued practice and development of the Emergency Response Plan in Brighton and Hove, Worthing, and Shoreham.


- Influence the coastal defence strategy, along the Lower Adur, to improve the sustainability of flood risk management in the this area.



- Visual impact of flood risk management activities within the proposed National Park




flood event. This increases to more

than 4200 people and more than 1750 properties in the

future.

There are limited historic reports of surface water and

urban drainage flooding and therefore we have not been able

to estimate the number of properties

affected by these sources of flooding. However, surface water and urban

drainage flooding is a known problem in this area and it is likely to increase in the future

A flood warnings

service is currently available to 1435

properties.




depth of fluvial and surface water and


The number of

people and properties at risk of fluvial

flooding will increase to be significantly


There will be a

significant increase from the current

number of properties affected by surface

water and urban drainage flooding.



channels and surface water and urban



depth of fluvial and surface and urban drainage flooding.


number of people and properties at risk of fluvial flooding will

increase to be substantially more than

4200 and 1750 respectively.

There will be a

substantial increase from the current level in

the number of properties affected by


flooding.


remains in place.



current level.


of localised fluvial flooding is likely to increase to slightly




flooding will increase from the current level due to the affects of

climate change.





fluvial flooding will remain at

approximately 2 and 10 respectively.



flooding will remain at the current level due to

improvements to the drainage networks.




The construction of a barrier across the River Adur would

reduce the number of people and properties

affected by fluvial flooding to none.

No properties will be

at risk of surface water and urban

drainage flooding due to upgrading of


networks.


and coverage

Not applicable.


or Areas of Outstanding Natural Beauty.



infrastructure does not increase in Shoreham in

the future.


line or increase in extent of critical infrastructure flooded, in Shoreham

and surrounding areas, from a 1% annual

probability fluvial flood event or surface water

flooding.

Indicators Length of A road and

railway line (km) affected by the 1% annual

probability fluvial flood event.




railway closures due to surface water and

groundwater flooding*.


water and groundwater flooding*.


historical records.


and soil erosion by supporting the existing and future management policies regarding environmentally sensitive farming practices.

- Support the existing flood defence measures in relation to surface water flooding.

- Provide development control advice to ensure no increase in run-off from the new development proposed in the South East Plan (e.g. Shoreham).






- Visual impact of flood risk management activities within the proposed National Park or Areas of outstanding Natural Beauty.


Currently approximately 0.06km of A road (A259) and 0.1km of railway are affected by the 1% annual probability

flood event. No critical

infrastructure sites are affected.

In the future there is

only a minor increase in length of A road

(A259) is affected by the 1% annual


There are no records of A road, railway and critical infrastructure

sites being affected by surface water and

urban drainage flooding, however, surface water and





height of embankments would result in an increase

in the frequency, extent and depth of fluvial and surface


More than 1km of A road and 1.5 km of

railway, four electricity sub

stations, one hospital and the Lancing police station are

likely to be at risk of flooding from fluvial flooding during the

1% annual probability flood event.

Substantially more surface water and

urban drainage flooding of A roads, railway and critical infrastructure sites.



frequency, extent and depth of fluvial and surface and urban drainage flooding.

More than 0.5km of A

road and 1km of railway is likely to be at

risk of flooding from fluvial flooding during


More surface water and urban drainage

flooding of A road and railway. Surface water

and urban drainage flooding may affect




current level.

Due to the railway being raised on

embankment in the future there is only a

minor increase in length of A road

affected by the 1% annual probability

flood event.

There will be an increase, from the

current risk, of surface water and urban

drainage flooding to A roads and critical

infrastructure sites.



Approximately 0.06km of A road and 0.1km of railway remain affected by flooding during the 1% annual probability

flood event.

With improvements to the surface water and

urban drainage networks there will be no change from the

current extent of surface water and

urban drainage flooding to A roads,

railway line and critical infrastructure sites.



water and urban drainage networks

would reduce fluvial and surface water



railway or critical infrastructure sites will be affected by fluvial or surface water and urban

drainage flooding.

Not applicable.


Protect and enhance the Adur Estuary SSSI.


Adur Estuary SSSI.

Indicators Habitat quality and species diversity.





designated habitats are


2 of the SSSI



There is a small increase to around

0.02km2 of the SSSI


flood event outline in the future. It is likely

Doing nothing and reducing the height of embankments would

allow the rivers to flood more frequently

and increase the flood depths,

increasing the area of the SSSI within the


substantially more than 0.2km

2.


channels and surface water and urban

drainage networks would eventually allow the rivers to flood more frequently and increase

the flood depths, increasing the area of

the SSSI within the 1% annual probability flood

outline to more than


0.02km2 in the area of

the SSSI within the 1% annual probability flood event outline due

to the affects of climate change in the future, however, it is

likely that there will be no notable increase in

habitat and species diversity with such a

The extent of the SSSI within the 1% annual probability flood event outline will remain at


There will be no


SSSI.




will reduce the extent of flooding and

therefore the extent of the SSSI within the 1% annual probability flood outline to less

than 0.01km2.

Not applicable.


susceptible to changes in flood frequency, floodwater chemistry, groundwater levels and drainage system maintenance.



that there will be no notable increase in habitat and species diversity with such a

minor increase.

There is increased

potential to substantially improve

or increase the habitat types and species diversity within the SSSI.



0.1km2.

There is increased


SSSI. However, this would occur in an unmanaged way.

minor increase. Decrease in flooding extent (duration and



SSSI.

Increase the landscape character value of the

Sussex Downs.

Targets Increase the landscape character value of the Sussex Downs AONB.

Indicators

Landscape character assessment of the

AONB.









2 of the

Sussex Downs AONB located within the 1%

annual probability flood event outline. This increases by a

minor extent to slightly more than 0.0004km

2

in the future.


Sussex Downs AONB is unlikely to notable

alter.


AONB located within the 1% annual


increases to be more than 0.05km

2.


AONB is likely to alter in a beneficial

manner, however, it will occur in an

unmanaged and un controlled way.

The area of the Sussex Downs AONB located within the 1% annual probability flood event outline increases to be

more than 0.02km2.


Sussex Downs AONB is likely to alter in a beneficial manner,


The area of the Sussex Downs AONB located within the 1%

annual probability flood event outline

increases over time to slightly more than

0.0004km2.

There would be no

notable impact on the landscape character of the Sussex Downs AONB in this policy

unit.

The area of the Sussex Downs AONB located within the 1% annual probability flood event

outline remains at around 0.0004km

2.

There would be no


the Sussex Downs AONB in this policy

unit.




will reduce frequency and depth of flooding and therefore have a negative impact on


AONB.


AONB located within the 1% annual


decreases to be nil.

Not applicable.


units





units NA




Policy Unit 7 - Shoreham and Adur Estuary


Policy option P1

Environmental

Social

NO LOSSES

HIGH-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by significantly more than 4198 and 740 respectively




� The critical infrastructure at risk from a 1% AEP flood event will increase by 4 electricity substations, 1 hospital and 1 police station

� Substantially more surface water and urban drainage flooding to

HIGH+

� The area of the Adur Estuary SSSI will increase by more than 0.19km

2 but in an


� The landscape value of the Sussex Downs will be likely to alter in a beneficial way but in an unmanaged and uncontrolled way

NO GAINS



Economic

transport routes will occur

HIGH-

� The AAD to properties and agricultural land caused by fluvial flooding will increase by more than £19.9 million

� AAD to properties and agricultural land caused by surface water flooding will increase significantly

� The balance of FRM expenditure to AAD is unacceptable with AAD to properties and agricultural land increasing by more than £19.9 million

NO GAINS

Policy option P2

Environmental

Social

NO LOSSES

HIGH-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by substantially more than 4198 and 740 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase substantially


� More surface water and urban drainage flooding to transport routes will

MEDIUM+

� The area of the Adur Estuary SSSI will increase by more than 0.09km

2 but in an

unmanaged way � The landscape value of the Sussex Downs will be likely to alter in a beneficial way but in an unmanaged way

NEUTRAL=


Not preferred option – There are limited gains under this policy option. The numbers of people and properties adversely affected by reducing FRM are unacceptably high. The AAD and level of disruption caused by flooding are also high and the environmental effects are unpredictable due to the unmanaged nature of this policy option.


Economic

occur

HIGH-

� The AAD to properties and agricultural land caused by fluvial flooding will increase by more than £16.9 million

� AAD to properties and agricultural land caused by surface water flooding will increase substantially

� The balance of FRM expenditure to AAD is unacceptable with AAD to properties and agricultural land increasing by more than £16.9 million

NO GAINS

Policy option P3

Environmental

Social

NO LOSSES

MEDIUM-

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will increase by approximately 4198 and 740 respectively

� The number of properties at risk of surface water and urban drainage flooding will increase in the future

� The length of A road at risk from a 1% AEP flood event will increase slightly

� Surface water and urban

MEDIUM+

� The area of the Adur Estuary SSSI will increase by approximately 0.01km

2

LOW+


MEDIUM+

� The length of railway at risk from a 1% AEP flood event will not increase in the future

NEUTRAL=


Not preferred option –The numbers of people and properties adversely affected by removing FRM are substantial. The AAD and level of disruption caused by flooding are also high.


Economic

drainage flooding to transport routes will increase slightly

MEDIUM-

� The AAD to properties and agricultural land caused by fluvial flooding will increase by approximately £14.9 million

� AAD to properties and agricultural land caused by surface water flooding will increase in the future

� The balance of FRM expenditure to AAD is unacceptable with AAD to properties and agricultural land increasing by approximately £14.9 million

NO GAINS

Policy option P4

Environmental

Social

LOW-

� The area of the Sussex Downs that falls within the 1% AEP remain the same with no increase in landscape value

NO LOSSES

LOW+

� The area of the Adur Estuary SSSI will not increase in the future with no notable change in habitat and species diversity

HIGH+



� The lengths of A road and railway at risk from a 1% AEP flood event will not increase in the future

NEUTRAL=

� The number of critical infrastructure at risk from a 1% AEP flood

Preferred Policy Option – There are few losses under this policy. The numbers of people and properties affected by flooding and the disruption caused will not increase in the future. The AAD and economic damages will remain constant and the associated future FRM expenditure will be efficient.


Economic

NO LOSSES

event will remain at 0 HIGH+



� The balance of FRM expenditure to AAD is acceptable with increases in FRM expenditure to significantly reduce AAD to properties and agricultural land

Policy option P5

Environmental

Social

Economic

MEDIUM-

� The area of the Adur Estuary SSSI will be reduced with a possible decline in habitat and species diversity

� The area of Sussex Downs that falls within the 1% AEP will be decreased which will impact negatively on the landscape value

NO LOSSES

MEDIUM-

NO GAINS

HIGH+

� The number of people and properties at risk of localised fluvial flooding in a 1% AEP flood event will be reduced


NEUTRAL=


HIGH+

� AAD to properties and

Not preferred option – Although there are additional gains in terms of reducing the numbers of people and properties affected by flooding and minimising the disruption it causes, these benefits are marginal in relation to additional FRM expenditure. This option is therefore not efficient. There are also significant negative environmental impacts associated with this policy option.


� The balance of FRM expenditure to AAD is unacceptable with significant increases in FRM expenditure to reduce AAD to properties and agricultural land

agricultural land caused by flooding will be minimised

� The balance of FRM expenditure to AAD will be acceptable with increases in FRM expenditure to reduce AAD to properties and agricultural land

Policy option P6

Environmental

Social

Economic


Key

HIGH:


MEDIUM:


LOW:



HIGH:

High positive A policy has a ‘high positive’ effect where it could contribute to a social,


economic or environmental objective in a significantly positive way. A ‘high positive’ effect could be: (i) a very large reduction in current flood risk; (ii) avoiding/reducing very large projected increases in flood risk under future conditions, and/or; (iii) significant additional social, economic and/or environmental gains.

MEDIUM:


LOW:




Policy unit 7 - Shoreham and Adur Estuary

Physical characteristics: - This unit is predominantly urban including Shoreham and Lancing. - Includes part of River Adur corridor from the coast to the A27. - The A27 trunk road and chalk downland landscape forms the northern policy unit

boundary. - Shoreham airport lies entirely within this unit. - Mainly chalk geology with flat low-lying ground.

Flood mechanism: - Heavily tidally influenced. - Overtopping of embankments – will not generally overtop due to fluvial flooding on

its own and will require significant tidal influence. - Surface water flooding through Shoreham airport generated from run-off from the

steep slopes of the South Downs – can takes weeks for the flood water to subside. Receptor:

- People, properties and infrastructure of the urban areas, including A259, A27, and Shoreham Airport.

- Most of the Adur Estuary SSSI lies within this policy unit, although only a minor extent that is not channel lies within the 1% annual probability flood outline.

- Currently approximately 11 properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event. As a result of climate change the number of properties at risk of fluvial flood alone is not expected to increase significantly. However, if a fluvial event should be combined with a significant tidal influence, it is expected that a large number of properties (around 1750) will be at risk in the future with a potential of up to £15 million damages (AAD).





- Flood risk from fluvial flooding is currently assessed as low, assessment changes to high in the future due to the increased influence from the tide resulting from sea level rise.

- Flood risk from surface water flooding is currently assessed as low to medium, assessment remains low to medium in the future.



Total damages (approx.) (1% annual probability flood event) £78 million

Problem/risk

Annual averages damages (approx.) £15 million

Policy selected Policy 4 - Take further action to sustain current scale of flood risk into the future (responding to the potential increases in flood risk from urban development, land use change, and climate change).

Justification

Although there are opportunities to reduce flooding in this unit by increasing storage on the floodplain upstream in other policy units, the level of potential flood risk in the unit is predicted to increase significantly (up to £15 million in damages AAD) in the future. Therefore we have selected policy 4 for this policy unit. Current management and maintenance activities include grass and weed cutting, cutting back overhanging branches, channel desilting and debris removal. This policy applies to this policy unit for the following reasons: - The current level of fluvial flood risk alone is low, however a combination of a high tide

and high river flows does increase the level of flood risk. - The level of flood risk in Shoreham needs to be addressed – local defences will need to

be maintained and improved over time to mitigate the affects of climate change, and this is recognised in the Rivers Arun to Adur Coastal Defence strategy study.

- The selected policy would help achieve the economic, and social objectives by maintaining the current level of flood risk within the policy unit in the future, by carrying out appropriate works to the river wall defences through the unit.

- Protection to historic landfill area from flooding. - Supports the regeneration proposals for Shoreham (Shoreham Renaissance, Shoreham

Marine North, Shoreham Airport and Shoreham Hospital).


- Ensure flood damages do not significantly increase in Shoreham due to future change (urban development and climate change).

- Ensure that river channel and flood defence maintenance expenditure is appropriate to


the property economic damage in urban areas from flooding. - Ensure the impact of flooding on people and property does not significantly increase in

Shoreham in the future. - Ensure the disruption caused by flooding to transport and critical infrastructure does not

increase in Shoreham in the future. - Protect and enhance the Adur Estuary SSSI. - Increase the landscape character value of the Sussex Downs.



development proposed in the South East Plan (e.g. Shoreham). - Reduce flood risk and improve water quality by promoting and encourage the use of

SuDS in the proposed urban developments in Shoreham. - Investigate removal of Environment Agency owned and maintained existing raised

defences to reinstate the floodplain between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.


- Improvements in the efficiency of channel and flood defence maintenance processes. - Effective and efficient use of developer contributions for flood risk management. - To work with Defra and farmers to produce soil management plans which have a benefit

to flood risk through reducing the run-off rate. - Continued practice and development of the Emergency Response Plan in Brighton and


Rife, to improve the sustainability of flood risk management in the this area. - Reduce surface water run-off and soil erosion by supporting the existing and future

management policies regarding environmentally sensitive farming practices. - Support the existing flood defence measures in relation to surface water flooding. - Help meet national biodiversity action plan (BAP) targets. Constraints: - Government and international legislation, environmental management policies, plans and





Areas of Outstanding Natural Beauty. - Transport links in the catchment are a vital part of the communication network regionally,





Policy 1 – do nothing. If defences were permitted to fall into disrepair the annual average damages could increase to more than £20 million and significantly more than 4200 people would be at risk. This policy, therefore, could not be considered as an alternative. Policy 2 – reduce current level of flood risk management. If the current flood risk management was reduced the annual average damages could increase to more than £17 million and substantially more than 4200 people would be at risk. This is considered unacceptable. Policy 3 – maintain current level of flood risk management. As with policy 1, this policy would not recognise the need to maintain flood risk from heavily influenced tidal flood events in the future, which is considered unacceptable. Policy 5 - reduce the level of flood risk, both now and in the future. The current level of risk is


managed adequately and therefore this policy is not justified. Policy 6 – increase flooding to reduce flood risk elsewhere. There are limited opportunities within this policy unit, due to the high density of development and essential infrastructure, to take this approach.


Flood risk from the sea is a significant consideration in this policy unit. Therefore, fluvial flood risk management options must fit with the shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future. Although the Defra 2006 guidance suggests greater levels of sea rise in the future, than used in the broadscale modelling, this would not change the policy selected for this policy unit. The broadscale model has not included the drainage network through the Shoreham Airport site. This area is at risk from overtopping of the Adur and also from groundwater and surface water run-off. There is, therefore, some uncertainty in the resulting flood extent and severity – particularly in the long-term. We have taken this uncertainty into account when selecting the most appropriate policy, but we must look at this again at the next CFMP review. Delivering this policy will partly depend on developing and implementing an effective urban drainage strategy in partnership with the local drainage authority, highway department, water and sewerage company and other relevant authorities or responsible parties.












Indicators to be included in policy unit 7 implementation plan are: Economic - Total annual average damages (to properties and agriculture) from fluvial flooding (£AAD). - Estimated damages resulting from surface water and groundwater flooding (£)(based on historical

damages). - Balance of annual river channel and flood defence maintenance expenditure (£) to annual average

damages from fluvial flooding to property (£). Social - Number of people and properties affected by the 1% annual probability fluvial flood event. - The estimated number of properties affected by surface water and groundwater flooding (based on

historical records). - Length of A road and railway line (km) affected by the 1% annual probability fluvial flood event. - Number of critical infrastructure sites affected by the 1% annual probability fluvial flood event. - Number and period of recorded A road and railway closures due to surface water and groundwater

flooding (based on historical records). - Number of critical infrastructure sites recorded as being affected by surface water and groundwater

flooding (based on historical records). Environmental - Habitat quality and species diversity. - Landscape character assessment of the AONB.


Policy unit 8 Adur Valley (north of A27 to south of Steyning)










Policy unit 8 – Adur Valley (north of A27 to south of Steyning)


Defences: In this unit raised embankments extend on both banks, giving a total of 10 km of defences along this reach of the River Adur. Flood Warning: This policy unit covered by the River Adur from downstream of Upper Beeding to Norfolk Bridge at Shoreham Flood Warning Area. Less than five properties are connected to the flood warnings direct service. Maintenance: We currently carry out annual inspection and maintenance of the embankments and flap gates. The estimated cost of maintaining the channels and existing defences under the Environment Agency’s responsibility is approximately £75,000.


Standard of protection: The River Adur embankments are considered to offer protection ranging from the 3.33% annual probability fluvial flood event (1 in 30) to the 0.5% annual probability event (1 in 200). They are considered to be at or above the target condition.




outline* Residential properties 0 0 N/A Commercial properties 0 0 N/A Population 0 0 N/A Property damages 0 0 N/A Agricultural damages £25 £26,835 N/A A roads 0 km 0.34 km 2.1 km Railways 0 km 0 km 0 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2


2 0 km

2

Agricultural land Grade 3 <0.001 km2 0.89 km

2 1.86 km

2

Agricultural land Grade 4 0 km2 0.39 km

2 0.82 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0.17 km

2

SSSI 0 km2 0 km

2 0.11 km

2

Listed Buildings 0 0 0 SM 0 0 0 AONB 0.001 km

2 1.28 km

2 2.68 km

2

ESA 0.001 km2 1.23 km

2 2.67 km

2


0 km2 0 km

2 0 km

2


2 2.63 km

2




Economic and social receptors: There are no people or properties at risk of flooding for the 1% annual probability flood event. A short length, less than 0.5km, of the A283 is located within the 1% and 0.1% annual probability flood event outline. Less than 1km

2 of agricultural land of grade 3 or 4 is at risk of flooding for the 1%

annual probability flood event, increasing slightly for the 0.1% annual probability flood event. Environmental designation: There are no internationally or nationally designated sites, SSSIs or SNCIs at risk of flooding for the 1% annual probability flood event within this policy unit. A small extent of the Adur Estuary SSSI and River Adur Meadows, Shoreham-by-Sea and the Mill Hill, Shoreham-by-Sea SNCIs are within the 0.1% annual probability flood event outline. Landscape: Parts of the Sussex Downs AONB and South Downs ESA and proposed National Park lies within both the 1% and 0.1% annual probability flood event outlines. Natural and Historic Environment:


There are no listed buildings, registered historic parks and gardens, SMs or wet woodlands at risk of flooding for the 1% or 0.1% annual probability flood events.


Increase in frequency of storm events resulting more frequent fluvial flooding. Sea level rise increases the likelihood of tidally influenced flooding in this policy unit*. *To represent future sea level rise, the tidal boundary within the broadscale model was scaled to



There is a very small increase (approximately £0.04 million) in AAD due to climate change over the next 100 years. In 100 years approximately 1 property is at risk of flooding.


There is potential to reduce flood risk downstream in other policy units by providing flood storage within this policy unit. Lowering or removing flood defences could help reduce flood risk in this and other policy units as well providing beneficial environmental impact.


Flood risk from the sea should also be a consideration in this policy unit due to the effect of sea level rise. Therefore, fluvial flood risk management options must consider the effects of shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future. The broadscale modelling has shown that lowering or removing flood defences can help reduce flood risk in neighbouring policy units. We will need more detailed studies to find out if it is practical to do this and improve the environment at the same time.




damages (£m)

The broadscale modelling has indicated that a change in the way land is managed, in the upper parts of the CFMP area, has a large positive impact on flood damages within this policy unit. Flood damages are shown to decrease by 58% for the 1% annual probability fluvial flood event, with flood depths decreasing by approximately 0.5 to 1m.



% change = -58%

Conclusions

The reduction in run-off rates by changes in farming practices in the upper parts of the catchment has shown a significant reduction in flood damages in this policy unit.




damages (£m)

There is a clear reduction in flood damages in the policy units further upstream, but there is only a small effect in this policy unit with a 3% decrease in flood damages.



% change = -3%

Conclusions

The flood mechanisms in this policy unit are dominated by tidal influences. Flood attenuation in the upper parts of the Adur catchment has limited impact on flood depths or extent within this policy unit.

Generic response: Barrier across the River Adur at Shoreham


damages (£m)

This case looks at the situation where a barrier is built across the mouth of the river that keeps the tide out, but allows free discharge of the river into the sea at low tide. There is a very small positive effect from this option in this policy unit with a 3% reduction in flood damages for the 1% annual probability fluvial flood event.



% change = -2%

Conclusions

There are limited impacts from flooding in this policy unit with less than 5 properties affected by the more severe fluvial flood events, which is reflected in the low flood damages. However, the environmental benefits from the increased flood extent should be investigated further.



damages (£m)

Reducing the height of the raised embankments along the River Adur allows more frequent inundation of the floodplain on both sides of the river. The results from the broadscale modelling show a large reduction of 31% for a 1% annual probability fluvial flood event. Within this policy unit water depths are reduced by approximately 1m from the future basecase.



% change = -31%

Conclusions

The impact of lowering the embankments along the River Adur within this policy unit increases the flood extent as it allows the water to spread out over a larger floodplain area, which has the effect of lowering the water depths and thus reducing the flood damages.
















reduced.


reduce over time.


A do nothing


unpredictable way.





place.



place.


of watercourses.



Construct a barrier across the River Adur within this policy unit.

There is potential to increase water

retention by introducing flood storage areas.

Economic objectives

Ensure flood damages do not significantly increase along the

Lower Adur corridor.

Targets No significant increase in damages along the

Lower Adur corridor due to future changes (climate change).

Indicators




advice to ensure no increase in run-off from the new development proposed in the South East Plan

- Reduce flood risk and improve water quality by promoting and encourage the use of SuDS in the proposed urban developments.







approximately £450. This increases to

around £1,000 in the future.

No maintenance of channels and a

reduction in height of embankments would lead to a significant increase in flooding


from fluvial flooding being significantly more than £1,000.

As channels decrease in capacity due to


average damages from fluvial flooding will



from fluvial flooding will increase over time due to the affects of climate change to be

around £1,000.




damages from fluvial flooding will remain at approximately £450.

The construction of a barrier across the River Adur would

reduce total annual average damages

from fluvial flooding to be minimal.

Increasing water retention by

introducing specific flood storage areas in this policy unit should reduce flood damages from fluvial flooding to

be minimal.

Social objectives







Indicators



event


Opportunities - Investigate removal of

Environment Agency owned and maintained existing raised defences to reinstate the floodplain between Partridge Green and Steyning and between Steyning and Shoreham to a naturally functioning state, to provide flood storage and enhance conservation value and biodiversity.
















The number of









more than zero.



to human life.


flood event


available.


flood event





flood event


available.



current baseline and there remains no requirement for a Flood Warning

Service.



Restore parts of the River Adur and

floodplain to a naturally functioning state where feasible downstream of

Steyning and Upper Beeding.

Targets Increase the length of naturally functioning

river and area of naturally active

floodplain along the River Adur downstream of Steyning and Upper

Beeding where feasible, providing suitable quality

habitat.

Indicators Length of naturally

functioning river (km).

Area of naturally functioning floodplain

(km2).

Opportunities - Enhance the character of the

landscape and increase amenity opportunities for recreation, tourism and leisure activities.



- Help meet national biodiversity action plan (BAP) targets.




- Individual homes and properties are currently at risk of flooding.

- Presence of protected species with specific water level, water quality and habitat requirements, for example in the Adur Estuary SSSI.


- Historic development and some heritage designations in Steyning, Bramber and Upper Beeding present permanent physical obstructions.

- Location of electricity pylons adjacent to the Lower River Adur (currently protected by existing defences).

- No degradation of existing fish passage and habitat.

Currently there is approximately 9.4km

of defended watercourse and no naturally functioning

river or naturally active floodplain in this policy

unit. There are opportunities now and

in the future to enhance the floodplain

connectivity along defended parts of the

River Adur, for example by restoring it

back to its original state or removing

raised embankments.



active floodplain is not expected to notably

alter.

No maintenance and removing the

embankments would allow the channel and floodplain to function more naturally and restore the natural

river processes (i.e. erosion and deposition).


unmanaged and unpredictable way.

The length of


increase by around 9 km and the area of

naturally active floodplain to

approximately 2 km2.

A reduction in maintenance would

allow the channel and floodplain to function more naturally and

restore the natural river processes (i.e. erosion

and deposition). However, this would

occur in an unmanaged and unpredictable way.


functioning river is likely to increase by around 4 km and the

area of naturally active floodplain to around 1

km2.

It is not expected that the river processes or floodplain connectivity

will significantly change under this

policy option.



active floodplain is not expected to notably

alter with the affects of climate change.

There is unlikely to be any significant

alterations to the river processes and

floodplain connectivity under this policy

option.

The length of naturally functioning river and

naturally active floodplain is likely to remain at the current

level.


River Adur will reduce the natural

river processes and floodplain

connectivity.

However, given that there is no current extent of naturally functioning river or

naturally active floodplain this policy option is unlikely to

notable impact on the current situation.

Restoring the rivers to a naturally functioning state and increasing

floodplain connectivity could be achieved through this policy

option whilst providing flood storage.


functioning river is likely to increase by up to 9.4km and the

area of naturally active floodplain to up to

2.6km2.

This would be achieved in a managed and

controlled way. These flood risk

management practices would have the potential benefit of reducing the flood risk in other parts of this

policy unit and in policy 7 (Shoreham and Adur Estuary)

downstream.


Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National

Park.

Targets Increase the landscape character value of the Sussex Downs AONB and South Downs ESA and proposed National

Park.


assessment of the AONB, ESA and







- Changes to flood risk management can affect the landscape, it’s character and value as an amenity.

There is currently approximately

1.28km2 of the Sussex



flood event outline. This increases by a

minor extent to around 2 km

2 in the future.



National Park is unlikely to notable

alter.





event outline increases to be more

than 2.6 km2.






controlled way.



annual probability flood event outline increases to be more than 2 km

2.


Sussex Downs AONB and South Downs ESA and proposed National Park is likely to alter in a beneficial manner,


The area of the Sussex Downs AONB

and South Downs ESA and proposed


time to at around 2 km

2.

There would be no

notable impact on the landscape character of the Sussex Downs





annual probability flood event outline remains at around 1.28km

2.

There would be no


the Sussex Downs AONB and South Downs ESA and



River Adur will reduce frequency and depth of flooding and

therefore have a negative impact on








event outline decreases to be

minimal.



National Park can be enhanced with the implementation of


practices, such as increasing the flood storage areas, in a


Does this policy change flood risk locally or elsewhere: Impact uncertain - increased water

retention will benefit

downstream areas

Impact uncertain - increased water

retention will benefit downstream areas

Unlikely to significantly affect

adjacent policy units





Increased water retention will benefit downstream areas




Policy Unit 8 - Adur Valley (north of A27 to south of Steyning


Policy option P1

Environmental

Social

Economic

NO LOSSES

MEDIUM-

� The number of people and property at risk significantly increases

HIGH-

� AAD to properties and agricultural land will increase by more than 550

HIGH+

� The length of naturally functioning river and area of naturally functioning floodplain will increase by approximately 9km

and 2km2 respectively,


� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP flood outline will increase by more than 0.72km

2 and are likely

to be beneficially altered but in an unmanaged and uncontrolled way

NO GAINS

NO GAINS

Not preferred option – Although the benefits to the environment are potentially high, alterations to the function of rivers and floodplains and to the landscape will be unmanaged and uncontrolled and therefore unpredictable. In addition to this, the AAD to properties and agricultural land resulting from this policy will be unacceptably high.

Policy option P2

Environmental

NO LOSSES

MEDIUM+

� The length of naturally functioning river and area of naturally functioning floodplain will increase by approximately 4km

and 1km2 respectively,


� The areas of the

Not preferred option – Although the benefits to the environment are potentially high, alterations to the landscape and river and floodplain function will be unmanaged and therefore unpredictable. In addition to this, the AAD to properties and


Social

Economic

LOW-


HIGH-

� AAD to properties and agricultural land will increase by more than 550

Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP flood outline will increase by more than 0.72km

2 and are likely

to be beneficially altered but in an unmanaged way

NO GAINS

NO GAINS

agricultural land resulting from this policy will be unacceptably high.

Policy option P3

Environmental

Social

Economic

NO LOSSES

NO LOSSES

MEDIUM-

� AAD to properties and agricultural land will increase by approximately 550

LOW+

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP will increase by approximately 0.72km

2

but with no notable increase in landscape value

NEUTRAL=

� The length of naturally functioning river and area of naturally functioning floodplain will not increase notably in the future

NO GAINS

NO GAINS

Not preferred option – The potential benefits in terms of the environment are not sufficiently optimised under this policy. In addition to this, the AAD to properties and agricultural land will increase significantly in the future.

Policy option P4

Environmental

LOW-

� The areas of the Sussex

NEUTRAL=

� The length of naturally

Not preferred option – Although AAD to properties and


Social

Economic

Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP remain the same with no increase in landscape value

NO LOSSES

NO LOSSES

functioning river and area of naturally functioning floodplain will not increase notably in the future

NO GAINS

HIGH+

� AAD to properties and agricultural land will not increase in the future

agricultural land will not increase in the future, opportunities to bring benefits to the environment are not sufficiently optimised under this policy.

Policy option P5

Environmental

Social

Economic

MEDIUM-

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP will be decreased which will impact negatively on the landscape value

NEUTRAL=

� The length of naturally functioning river and area of naturally functioning floodplain will not increase in the future

NO LOSSES

NO LOSSES

NO GAINS

NO GAINS

HIGH+

� AAD to properties and agricultural land will be minimised

Not preferred option – Although AAD will be minimised, the impact on the environment is unnecessarily negative.

Policy option P6

Environmental

NO LOSSES

HIGH+

� The length of naturally functioning river and area of naturally functioning floodplain will increase by up to 9km

and 2km

2

respectively, but in an managed and controlled way

� The landscape value of the Sussex Downs AONB and South

Preferred Policy Option – There are no losses under this policy option. The potential benefits to river and landscape function and landscape value are maximised and will be carried out in a managed and controlled way. Encouraging increased uptake of agri-environment schemes and managing FRM will


Social

Economic

NO LOSSES

NO LOSSES

Downs ESA/proposed NP will be enhanced in a managed and controlled way

NO GAINS

HIGH+

� AAD to properties and agricultural land will not be minimised

minimise the AAD to land. Implementing policy option 6 in this part of the catchment will also bring strategic benefits to policy units downstream through increased floodwater storage.

Key

HIGH:


MEDIUM:


LOW:



HIGH:



MEDIUM:


LOW:





Physical characteristics: - Unit consists of the rural landscape immediately adjacent to the river corridor and

contains a few isolated properties. - River Adur corridor, including a small part of the Adur Estuary SSSI. - Relatively flat low-lying ground in a valley between the South Downs Chalk block.

Flood mechanism: - Heavily influenced tidal flooding. - Overtopping of embankments – will not generally overtop due to fluvial flooding on

its own and will require significant tidal influence. Receptor:

- Infrastructure (roads and rail), isolated properties and agricultural land. - Sussex Downs AONB, South Downs ESA and Proposed National Park. - Includes part of the Adur Estuary SSSI and part of the Beeding Hill and Newtimber

Hill SSSI. No extent of these SSSIs are located within the 1% annual probability flood outline.

- The majority of the River Adur Meadows, Shoreham-by-Sea, the Mill Hill, Shoreham-by-Sea and the Old Erringham Farm valley and road cutting SNCIs. No extent of these SNCIs are located within the 1% annual probability flood outline.

- Currently no properties are at risk of fluvial flooding in the policy unit from the 1% annual probability fluvial flood event.



Total damages (approx.) (1% annual probability flood event) £27,000

Annual averages damages (approx.) £450

Future Flood risk: - Flood risk is currently assessed as low, and it is not expected to increase under

future scenarios. Future Flood Risk Summary (in 100 years time)

Number of properties at risk of flooding (1% annual probability flood event) Less than 5

Total damages (approx.) (1% annual probability flood event) £65,000

Problem/risk



Justification

This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding locally in this unit, flooding downstream can be reduced, and in many instances, increasing flooding can improve wetland biodiversity, as flooding is a natural part of floodplain ecosystems. Current management and maintenance activities include grass and weed cutting, cutting back overhanging branches, channel desilting and debris removal. Policy 6 sets a framework that actively supports increased flooding, or at least keeps water on the land for longer. This applies to this policy unit for the following reasons: - With a low flood risk within this policy unit, there is no need for a significant flood risk

reduction policy.

- Applying policy 6 here may help reduce flood risk downstream in policy unit 7. - An increase in flooding could result in an increase of approximately 140 hectares of

wetland around the River Adur Meadows, Shoreham-by-Sea and the Mill Hill, Shoreham-by-Sea SNCIs. This will improve local biodiversity and help meet biodiversity action plan targets.

- This policy would help meet the catchment objectives, having a positive effect on biodiversity in this area, leading to an eventual increase in extent, quality and diversity of wetland habitats, with opportunities for recreation and landscape. Emphasis would be placed on helping the public and landowners to understand the risk of flooding and climate change better; encourage close partnership with local communities and rural development authorities; and build policy objectives into planning documents.


- Ensure flood damages do not significantly increase along the Lower Adur corridor. - Restore parts of the River Adur and floodplain to a naturally functioning state where

feasible downstream of Steyning and Upper Beeding. - Increase the landscape character value of the Sussex Downs AONB and South Downs

ESA and proposed National Park. Catchment-wide opportunities



and constraints development proposed in the South East Plan. - Reduce flood risk and improve water quality by promoting and encourage the use of

SuDS in the proposed urban developments. - Investigate removal of Environment Agency owned and maintained existing raised

defences to reinstate the floodplain between Steyning and Shoreham to a naturally functioning state, to provide flood storage, enhance conservation value and biodiversity.

- Enhance the character of the landscape and increase amenity opportunities for recreation, tourism and leisure activities.


- Help meet national biodiversity action plan (BAP) targets. Constraints: - Government and international legislation, environmental management policies, plans and




- Individual homes and properties are currently at risk of flooding. - Presence of protected species with specific water level, water quality and habitat

requirements, for example in the Adur Estuary SSSI. - Changes to flood risk management can affect the landscape, its character and value as

an amenity. - Historic development and some heritage designations in Steyning, Bramber and Upper

Beeding present permanent physical obstructions. - Location of electricity pylons adjacent to the Lower River Adur (currently protected by

existing defences). - No degradation of existing fish passage and habitat.


Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, the effects would happen in an unmanaged and unpredictable way, and local flood risk may increase. Policy 2 - reduce current level of flood risk management. This could also be considered a possible policy option for this area, and it could allow increased floodplain inundation whilst controlling the changes that would happen in time. However, this policy does not reflect the scale of the likely changes and it does not ensure the level of investment and commitment to meet the catchment objectives. Policy 3 - maintain current level of flood risk management. This option results in the least favourable result, with increases in damages locally of approximately 68% but with none of the benefits that would come from a managed approach of potentially increasing areas of wetland and therefore improving local biodiversity and help meet biodiversity action plan targets. Policy 4 - maintain the current level of flood risk into the future. This policy could apply to this policy unit, but it implies a need for increased flood risk management in the future and does not consider the opportunity for potential reduction in flood risk in policy unit 7. Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the current and future level of flood risk within the policy unit, and would require an unsustainable level of investment in flood defences to meet future changes.


Flood risk from the sea should also be a consideration in this policy unit due to the effect of sea level rise. Therefore, fluvial flood risk management options must consider the effects of shoreline management plan policy and actions. We have estimated the future increase in flood risk within this policy unit on the best available prediction we have of climate change (prior to the Defra October 2006 guidance), frequency and size of storms and flood events in the future. Although the Defra 2006 guidance suggests greater levels of sea rise in the future, than used in the broadscale modelling, this would not change the policy selected for this policy unit. The broadscale modelling has shown that lowering or removing flood defences can help reduce flood risk in neighbouring policy units. We will need more detailed studies to find out if it is practical to do this and improve the environment at the same time.












Indicators to be included in policy unit 8 implementation plan are: Economic - Total annual average damages (to properties and agriculture) from fluvial flooding (£AAD). Environmental - Length of naturally functioning river (km). - Area of naturally functioning floodplain (km

2).

- Landscape character assessment of the AONB, ESA and proposed National Park.


Policy unit 9 South Downs (East)










Policy unit 9 – South Downs (East)


Defences: There are no formal flood defences in this policy unit, however, there are small flood detention bunds at Bevendean to hold back localised run-off from the Downs. Flood warning: This policy unit is not covered by a fluvial flood warning area. No properties are connected to the flood warnings direct service. Maintenance: The maintenance of these structures is unknown. The estimated annual cost of maintenance to channels undertaken by the Environment Agency within this policy unit is approximately £1,000.


Standard of protection: There are no formal flood defences within this policy unit.




outline* Residential properties 0 0 N/A Commercial properties 0 0 N/A Population 0 0 N/A Property damages 0 0 N/A Agricultural damages £0 £0 N/A A roads 0 km 0 km 0 km Railways 0 km 0 km 0 km Agricultural land Grade 1 0 km

2 0 km

2 0 km

2


2 0 km

2


2 0.01 km

2


2 0 km

2


2 0 km

2

SNCIs 0 km2 0 km

2 0 km

2

SSSI 0 km2 0 km

2 0 km

2


2 0 km

2 0.01 km

2

ESA 0 km2 0 km

2 0 km

2


0 km2 0 km

2 0 km

2


2 0.01 km

2




Economic and social receptors: There are no people, properties, extent of A road, railway or area of graded agricultural land at risk of flooding for the 1% annual probability flood event. A small extent of grade 3 agricultural land lies within the 0.1% annual probability flood event outline. Environmental designation: There are no internationally or nationally designated sites, SSSIs or SNCIs at risk of flooding for the 1% or the 0.1% annual probability flood events within this policy unit. Landscape: A small extent of the Sussex Downs AONB and South Downs proposed National Park lies within the 0.1% annual probability flood event outline. Natural and Historic Environment: There are no listed buildings, registered historic parks and gardens, SMs or wet woodlands at risk of flooding for the 1% or 0.1% annual probability flood events.


Climate change, through more intense rainfall events. Land use changes contributing to increase in soil erosion, such as changes in crop type and increases in livestock stocking density.



Flood risk is currently assessed as low, and it is not expected to increase under future scenarios.


Potential to work with professional partners to derive better land management options so that run-off can be reduced and soil erosion avoided.


There is uncertainty about how effective changes in land management and vegetation cover will alter run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.

There is no flood risk within this policy unit, however, it does contribute to groundwater flooding and surface water run-off in neighbouring policy units. We have not been able to model these processes and it has therefore not been possible to define generic responses in this policy unit.
















reduced.


reduce over time.

Deterioration of the small flood detention bunds at Bevendean.

A do nothing


unpredictable way.




Deterioration over time

of the small flood detention bunds at

Bevendean.



of watercourses.


Introduce management

practices that allow greater water

retention within the policy unit i.e. change

in land use.






Economic objectives




from flooding.





(£).





(£).


efficiency of flood defence maintenance processes.








approximately £1,000; the annual average

damages from fluvial flooding to agriculture are currently less than £100. Annual average damages from fluvial flooding to agriculture

are unlikely to significantly increase, being less than £150

in the future.






from fluvial flooding to agriculture






Annual average damages from fluvial flooding to agriculture are likely to be around

£1,000.


damages becomes unacceptable over

time.


at approximately £1,000. Annual

average damages from fluvial flooding to agriculture increase over time due to the

affects of climate change to be less than

£150.








agriculture will remain less than £100.

With better






increase to be more than £1,000. Annual

average damages from fluvial flooding to agriculture are

estimated to be £0.




maintenance expenditure is likely to remain the same or be





are likely to remain less than £100.



These flood risk

management practices would have the potential benefit of reducing the flood risk in policy 6 (Brighton

and Hove) downstream.

Social objectives







Indicators



event


Opportunities - Reduce flood risk and

improve water quality by promoting and encouraging the use of SuDS in the proposed urban developments in Brighton and Hove, Worthing, Shoreham and Burgess Hill.


- Develop a flood warning system for groundwater flooding.














The number of









more than zero.



to human life.


flood event


available.


flood event





flood event


available.



current baseline and there remains no requirement for a Flood Warning

Service.


Increase the landscape character value of the Sussex Downs AONB

and South Downs proposed National Park.

Targets Increase the landscape character value of the Sussex Downs AONB

and South Downs proposed National Park.

Indicators

Landscape character assessment of the

AONB and proposed National Park.



Constraints



There is currently 0km

2 of the Sussex



flood event outline. This is not expected to increase in the future with current flood risk

management.


Sussex Downs AONB and South Downs proposed National Park is unlikely to

alter.


AONB and South Downs proposed



increases to be slightly more than

0.01km2.


AONB and South Downs proposed National Park is

unlikely to notably alter due to such a minimal increase.


South Downs proposed National Park located within the 1% annual probability flood event outline increases to be

around 0.01km2.


Sussex Downs AONB and South Downs

proposed National Park is unlikely to notably alter due to such a minimal increase.

There is no extent of the Sussex Downs AONB and South Downs proposed


outline.



outline.



probability flood event outline.


Sussex Downs AONB and South Downs proposed National

Park can be enhanced with the

implementation of considered flood risk

management practices, such as

increasing the flood storage areas, in a



Reduced conveyance may

benefit downstream areas

Reduced conveyance may

benefit downstream areas



Increased conveyance may increase flood risk

downstream


adjacent policy units, although

improved retention may benefit

downstream areas

Increased water retention through

agri-environmental schemes will benefit downstream areas




Policy Unit 9 - South Downs (East)


Policy option P1

Environmental

Social

Economic

NO LOSSES

MEDIUM-


HIGH-

� The balance of FRM expenditure to AAD is unacceptable with AAD to agricultural land increasing by more than £900

MEDIUM+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP are likely to be beneficially altered but in an unmanaged and uncontrolled way

NO GAINS

NO GAINS


Policy option P2

Environmental

Social

Economic

NO LOSSES

LOW-


HIGH-

� The balance of FRM expenditure to AAD is unacceptable with AAD to agricultural land

MEDIUM+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP are likely to be beneficially altered but in an unmanaged way

NO GAINS

NO GAINS



increasing by more than £900

Policy option P3

Environmental

Social

Economic

NO LOSSES

NO LOSSES

NO LOSSES

LOW+


NO GAINS

LOW+

� The balance of FRM expenditure to AAD will remain acceptable with AAD to agricultural land increasing slightly in the future


Policy option P4

Environmental

Social

Economic

LOW-

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP remain the same with no increase in landscape value

NO LOSSES

NO LOSSES

NO GAINS

NO GAINS

MEDIUM+

� The balance of FRM expenditure to AAD will remain acceptable with slight increases in FRM expenditure to maintain AAD to agricultural land at current levels in the future

Not preferred option – Although AAD to agricultural land will not increase in the future, opportunities to bring benefits to the environment are not sufficiently optimised under this policy.

Policy option P5

Environmental

MEDIUM-

� The areas of the Sussex Downs AONB and South Downs ESA/proposed NP that fall within the 1% AEP will be decreased which will

NO GAINS

Not preferred option – There are no gains under this policy option. FRM expenditure is unacceptably high and there will be negative impacts on the


Social

Economic

impact negatively on the landscape value

NO LOSSES

HIGH-

� The balance of FRM expenditure to AAD is unacceptable in with significant increases in FRM expenditure to reduce AAD to agricultural land

NO GAINS

NO GAINS

landscape value of the area.

Policy option P6

Environmental

Social

Economic

NO LOSSES

NO LOSSES

NO LOSSES

HIGH+

� The landscape value of the Sussex Downs AONB and South Downs ESA/proposed NP will be enhanced in a managed and controlled way

NO GAINS

HIGH+

� The balance of FRM expenditure to AAD will remain acceptable with reductions in FRM expenditure and AAD to agricultural land due to agri-environment schemes and targeted FRM

Preferred Policy Option – There are no losses under this policy option. The potential benefits to landscape value are maximised and will be carried out in a managed and controlled way. The balance between FRM and AAD to agricultural land will be optimised. Encouraging increased uptake of agri-environment schemes will further reduce the AAD to land. Implementing policy option 6 in this part of the catchment will also bring strategic benefits to policy units downstream through increased floodwater storage.

Key

HIGH:


MEDIUM:


LOW:

Low negative A policy has a ‘low negative’ effect where it could make a limited contribution to


a social, economic or environment objective, but where the overall contribution would be negative. A ‘low negative’ effect could be: (i) an overall increase in current flood risk; (ii) an overall increase in flood risk under future conditions, and/or; (iii) overall social, economic and/or environmental losses.


HIGH:


MEDIUM:


LOW:





Physical characteristics: - Steep scarp slopes of the chalk downland hills extend the entire width of the CFMP

area. - Environmentally Sensitive Area and Area of Outstanding Natural Beauty. - Shallow silty soils are well drained and the chalk is an important local aquifer for

water supply. - Proposed National Park with high amenity value and landscape character. - Contains a large proportion of Scheduled Monuments and a significant proportion of

SSSIs in the CFMP area. Flood mechanism:

- No fluvial flooding within the policy unit. - Land management affects runoff rates with certain types of management causing

muddy floods in adjacent urban areas. Receptor:

- None within the policy unit. - Adjacent urban areas (particularly in Policy Unit 6 - Brighton and Hove) are

receptors of flooding generated due to land management in this unit. Current Flood Risk Summary



Annual averages damages (approx.) Negligable

Future Flood risk: - Flood risk is currently assessed as low, and it is not expected to increase under

future scenarios. Future Flood Risk Summary (in 100 years time)



Problem/risk

Annual averages damages (approx.) Negligable


Justification

This policy can deliver benefits for people and the environment locally or in other policy units. By increasing flooding and infiltration of rainwater locally in this unit, flooding downstream can be reduced. Current maintenance activities include grass and weed cutting. The changes in land management can also benefit biodiversity. Policy 6 sets a framework that actively supports increased flooding and infiltration of rainwater and is appropriate to this policy unit for the following reasons: - Although flood risk is assessed as low within the policy unit, there is the opportunity to

reduce flood risk in adjoining units. - Large rural policy unit which presents opportunities for changing land use and

developing possible flood storage mechanisms to reduce rapid run-off generated from land use activities and the steep slopes.

- Action in this unit will help reduce risk of muddy floods in the suburbs of Brighton. - There are some opportunities for reducing downstream flooding by improving or creating

new habitats, which increase water retention. - Soil erosion problems can best be tackled through more sensitive land management,

land use change, and changes in farming practices. - Increased storminess due to climate change may increase soil erosion and localised

flash flooding in neighbouring catchments. - This policy would help meet the environmental and landscape objectives by working with

landowners and the Government.


- Ensure that flood defence maintenance expenditure is appropriate to the agricultural economic damage in rural areas from flooding.

- Increase the landscape character value of the Sussex Downs AONB and South Downs proposed National Park.


Opportunities: - Improvements in the efficiency of flood defence maintenance processes. - To work with Defra and farmers to produce soil management plans which have a benefit

to flood risk through reducing the run-off rate. - Help meet national biodiversity action plan (BAP) targets. - Continue local authority and Environment Agency support of the Flood 1 project in

relation to groundwater flooding. - Develop a flood warning system for groundwater flooding.


Constraints: - Available funding for the initial set up of new flood risk management schemes. - Older flood defence structures are likely to be more costly to maintain. - Limited available information on surface water and groundwater flood damages. - Some environmentally designated habitats are susceptible to changes in flood


an amenity. - Visual impact of flood risk management activities within the proposed National Park or

Areas of Outstanding Natural Beauty. - Government and international legislation, environmental management policies, plans and



Policy 1 - do nothing. Although this could be considered as a possible policy option, and would have a similar long-term result as policy 6, it would limit the opportunities to reduce soil erosion and surface water run-off that affect neighbouring policy units. Policy 2 - reduce current level of flood risk management. There is already minimal flood risk management within this policy unit. It is not possible to reduce it further. Policy 3 - maintain current level of flood risk management. This policy could also apply as maintaining the current level of flood risk management is the same as ‘do nothing’ in this case. But it does imply that a certain level of flood risk management is being carried out which is not correct. Policy 4 - maintain the current level of flood risk into the future. As with policy 3, this policy could apply, but it implies a level of activity that is not happening. Policy 5 - reduce the level of flood risk, both now and in the future. This policy is not justified by the level of flood risk within the policy unit.


There is uncertainty about how effective changes in land management and vegetation cover will alter run-off at the catchment scale. It is known to work locally, but we do not yet know its effect on the catchment as a whole. Changes in land management will depend on the agreement of landowners. The understanding of the impact of climate change on groundwater is still in its infancy, and there is still a lot of uncertainly surrounding the impact on groundwater flooding events.












Indicators to be included in policy unit 9 implementation plan are: Economic - Balance of annual flood risk maintenance expenditure (£) to annual average damages from fluvial

flooding to agriculture (£). - Flood damages downstream in policy unit 6 (Brighton and Hove) (£). Social - The estimated number of properties affected by Downland ‘muddy’ surface water flooding

downstream in policy unit 6 (Brighton and Hove). Environmental - Landscape character assessment of the AONB and proposed National Park.


Form B11 Signature of

CFMP Project Manager:

Gary Lane

Date (of completion): September 2008


B4.2 Assessment and evaluation of impacts The alternative options have been assessed against objectives that are specific for each policy unit. The tables set out below detail this appraisal. These tables identify the losses and gains under each of the six generic policy options and identify the preferred option for each policy unit along with monitoring requirements. As such they set out the findings of the SEA in relation to the assessment of options. In consultation with Natural England we have demonstrated that as a result of this CFMP there will be no significant impacts on Natura 2000 sites as there are no designated sites within the CFMP area. Information on mitigation and enhancement measures related to the preferred policy option identified for each policy unit is set out in section B4.4. At this level of plan, the mitigation and enhancement measures are integral to the policy appraisal. Where we have the potential to enhance the environment we have included this potential within the appraisal objectives. Mitigation measures at this level are generally included as part of the policy options, so that a less detrimental impact will tend to be an alternative policy option. We therefore can not identify any further specific mitigation measures at the policy level. At a lower level in our planning hierarchy, when we are investigating the details of how we will implement flood risk management measures, we will be undertaking an appropriate level of environmental assessment which will, in turn, identify more relevant mitigation measures to the impacts arising.

4.3 Cumulative environmental effects

SEA requires assessment of cumulative and synergistic effects. This section sets out the significant environmental effects of the plan as a whole, which have been considered in relation to each of the environmental objectives. It goes on to consider the environmental effects of potential interactions between the CFMP and relevant plans and programmes within the catchment. These findings are summarised in Table B5 below.


Table B5 Summary of cumulative issues Cumulative effects across the whole plan area

Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts

Interaction of CFMP with relevant Plans

and Programmes

HIGH

+ N/A

LOW

+

HIGH

+

LOW

+ N/A N/A

HIGH

+

HIGH

+ HIGH +

Restore rivers and floodplains to a naturally functioning state where feasible.

Flood water storage can be effectively increased through strategic restoration of river and floodplain function. This will reduce flood risk to people, properties, critical infrastructure and other valuable environmental and historic assets downstream. The strategy of this CFMP is to restore the rivers and floodplains of the River Adur and its east and west tributaries in the upper catchment as well as introducing managed floodwater storage in these areas. By relaxing flood defences and allowing natural processes to be restored in a managed and predictable way, the frequency of flooding will increase as will water retention. This will have the benefit of reducing flood risk in the high-risk downstream areas of Worthing, Brighton, Hove, Shoreham, Steyning and Upper Beeding without the need for extensive FRM improvements. Increased FRM in Burgess Hill and Hassocks under a policy option 4 could potentially increase flows into the Upper Adur as they bypass the urban areas. By increasing storage in the Upper Adur, this potential impact will not be passed on to urban areas downstream and will instead be retained in rural areas where wetland habitats can be created. Managing this potential carefully will also ensure risks in the policy units in which flooding frequency is increased can be minimised where it has the potential to cause harm to isolated settlements or environmental receptors. There is also potential to restore river channels in some of the urban areas of the catchment, namely Steyning, Upper Beeding and Worthing, with the aim to reduce flows by increasing capacity and river bank naturalisaton. This will bring additional local improvements to the environmental and amenity value of these urban corridors. Restoring river channels and floodplains to their natural state will also bring significant environmental benefits in terms of creating valuable wetland habitats or important species. There will be great potential to contribute to UK and local BAP

Adur and Ouse Catchment Abstraction Management Scheme The CFMP will have the opportunity to influence the water quality concerns associated with the large Goddards Green waste water treatment works discharges to the east branch of the River Adur. The CFMP has the opportunity to improve water resource efficiency and abstraction issues. Regional Forestry and Woodlands Framework for the South East There is potential for positive interaction with the CFMP to encourage more environmentally sensitive land management practices. This framework includes provisions for riverbank stabilisation and tree planting targets. The High Weald AONB Management Plan There are objectives within the AONB Management Plan to reduce flood risk through restoration and protection of functional floodplains which is a direct opportunity for positive interactions with the CFMP. South Downs Management Plan This plan contains policies to alleviate


Cumulative effects across the whole plan area

Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

targets as well as enhancing existing designated sites such as the Adur Estuary SSSI and several SNCIs. Managing this potential carefully under policy option 6 will ensure any potentially negative impacts can be avoided. Increasing water retention in the upper catchment, Adur Valley and South Downs may have an impact on the landscape character of the High Weald and Sussex Downs AONBs, proposed South Downs National Park and South Downs ESA, as well as the general landscape character area. The areas of these designated landscapes that are affected by flooding are minimal and if water retention is managed in a careful and predictable manner, negative impacts will be highly unlikely. In fact, this is more likely to enhance the character and value of these landscapes. However, it is unlikely that such enhancements will have a significant impact on the tourism and amenity value of the designated areas, however, the general landscape character areas may be enhanced bringing potential for a wider range of recreation activities associated with water bodies and wetland habitats.

abstraction pressure through increased storage within the catchment, to improve river flow and reduce flood risk in vulnerable areas through floodplain and wetland restoration and maintenance of water flow to ditches. These aims are complemented very well by the policies of this CFMP although the future National Park status may bring other constraints. Destination South East Proposed Alterations to Regional Planning Guidance, Tourism and Related Sport and Recreation There is potential for positive interactions as the CFMP will seek to support the long term aims of conserving and enhancing the environment, avoiding damaging activities and promoting appropriate activities such as water sports, angling, ecology/nature and walking which can be associated with natural riverine habitats.

HIGH

+ N/A

MED

+

MED

+

MED

+ N/A

LOW

+

MED

+

MED

+ HIGH +



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

Protect and enhance nationally and internationally important species and habitats.

There are numerous SSSIs within the CFMP area, of which only the Adur Estuary SSSI is at relative risk from a 1% annual probability flood event. There are also several SNCIs at risk from flooding, with a total area of 3.3km

2 falling within the

1% annual probability outline. Increasing water retention in the upper catchment and river channels will have a positive impact on the water-dependent Adur Estuary SSSI and the River Adur Water Meadows, Wyckham Wood and the Ferring Rife and Meadows SNCIs. However, retention of water will have to be carefully planned and managed to protect any sensitive designated sites or habitats from flood damage. There is an expected net benefit to BAP priority habitats such as wet woodland and coastal and floodplain grazing marsh and associated species such as the brown/sea trout, otter and great crested newt. Changes in rural land management will have a positive impact on the biodiversity of habitats and species. By strategically implementing policy option 6, it is more likely that these aims can be achieved in a predictable and manageable way. This policy will encourage the uptake of agri-environment schemes with the aim of reducing run-off and flood risk. However, these schemes will also lead to significant environmental improvements in terms of water quality, soil management and habitat protection and enhancement.

Land Use Management Plans (various) There is potential for positive interaction as the plans will seek to implement more sensitive land management practices. This will support and encourage the protection and enhancement of biodiversity and there may be assistance for investment in resources related to soil and water management and conservation, particularly in policy units 1, 4, 8 and 9. UK BAP and Local BAP for Sussex Positive interactions are likely to arise and there may be opportunities for habitat creation and protection and expansion of designated sites. The BAP habitats and species associated with these sites will also benefit from the policies of the CMFP. There is also potential for outcomes of the CFMP to be incorporated into future revision of BAP Habitat and Species Action Plans. Local Development Frameworks (various) There is potential for positive interactions as polices contained within the Local Plans aim to sustain and improve biodiversity and the natural environment, and help ensure their protection beyond the duration of the CFMP. As many of these planning frameworks are in the development stages, there will be opportunities for the CFMP to inform this



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

process. The High Weald AONB Management Plan There are objectives within the AONB Management Plan to protect and enhance UK and local BAP priority species and habitats, particularly wetlands, wet woodlands and riverine habitats, which is a direct opportunity for positive interactions with the CFMP. River Basin Management Plan There are opportunities for this to interact positively with the CFMP to achieve common aims to protect and enhance biodiversity, BAP priority species and habitats and designated fisheries through improvements in water quality. Improvements in water quality will bring added benefits in terms of FRM. There is significant opportunity for these plans to coordinate approaches in the early stages of their development. Regional Forestry and Woodlands Framework for the South East There is potential for positive interaction with the CFMP to encourage more environmentally sensitive land management practices, and opportunities to increase tree planting may help to alleviate damaging flows, particularly in policy units 1, 4, 8 and 9.



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

MED

+ HIGH

+ LOW -

MED +

MED -

LOW - HIGH

+ MED

+ MED

+ MEDIUM +

Ensure the impact of flooding on people and properties does not significantly increase in the future (for example due to climate change).

There are approximately 400 people at risk of flooding (1% annual probability flood event) across the CFMP area with this number set to increase significantly to nearly 6,000 in the next 50-100 years. The majority of this increase is predicted in Shoreham where climate change and sea level rise are likely to cause very significant increases in flood risk. The overall combination of policies for this CFMP will ensure the number of people and properties at risk from flooding does not increase significantly in the future. The risk of flooding in the Lower Adur catchment will not increase significantly in the future due to strategic water storage in the upper catchment coupled with increased defences around Shoreham. The current levels of FRM in Worthing, Brighton, Hove, Steyning and Upper Beeding, in combination with strategic flood water attenuation, will ensure there are no significant increases in flood risk in the future. Although flood risk to individual properties could potentially increase in the rural areas of the catchment Upper Adur and South Downs, these should be protected through carefully managed water storage under policy option 6. The flood risk to people and properties in Burgess Hill will not increase in the future due to increased FRM to maintain current levels. Implementing policy option 4 in the high flood risk area of Shoreham will also mitigate the potentially severe impacts of climate change and sea level rise.

Regional Spatial Strategy for the South East There is potential for negative interaction if strategic development is located in areas at severe risk of flooding, such as Shoreham, Brighton and Hove and Worthing, particularly as the RSS will extend beyond the duration of this CFMP. However, given that development should only be permitted in line with PPS 25, this is unlikely to be significant. Local Development Frameworks (various) There is potential for negative interactions if the Local Plans allow significant development to occur in areas at risk of flooding, due to flood risk management activities throughout the catchment, particularly as Local Plans will extend beyond the duration of the CFMP. However, given that development should only be permitted in line with PPS 25, this is unlikely to be significant. As many of these planning frameworks are in the development stages, there may be opportunities for the CFMP to inform the process and avoid future increases in flood risk. There is also potential to minimise the extents, frequency and duration of flooding through implementation of SuDS in the new emerging LDFs which will in



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

turn reduce risk to life. Beachy Head to Selsey Bill Shoreline Management Plan There is potential for positive interactions between the SMP and CFMP to reduce flood risk to Shoreham Harbour and the River Adur in the future, where the policy is to hold the line. South Downs Management Plan This plan contains policies to alleviate abstraction pressure through increased storage within the catchment, to improve river flow and reduce flood risk in vulnerable areas through floodplain and wetland restoration and maintenance of water flow to ditches. These aims are complemented very well by the policies of this CFMP although the future National Park status may bring other constraints. Land Use Management Plans (various) There is potential that positive interaction between the plans as policies may result in reduced run-off and mitigation against climate change, particularly in policy units 1, 4, 8 and 9. Regional Forestry and Woodlands Framework for the South East



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

Positive interactions may potentially arise in those parts of the catchment where CFMP policies support sustainable land management, including tree planting schemes which will help to alleviate flood flows, particularly in policy units 1, 4, 8 and 9.

MED

+ HIGH

+ LOW -

MED +

MED -

LOW - HIGH

+ MED

+ MED

+ MEDIUM +

Ensure the disruption caused by flooding to transport and critical infrastructure does not significantly increase in the future (for example due to climate change).

It is expected that this combination of policies will ensure that flood risk to critical infrastructure and transport routes does not increase significantly in the future. The urban areas of Burgess Hill, Hassocks and Shoreham will be well protected against increased flood risk through the implementation of policy option 4 which will increase FRM to maintain current levels of risk into the future. The combination of water retention upstream and maintained defences in Brighton, Hove, Steyning, Upper Beeding and Worthing will also ensure no significant increases in flood risk to these urban areas. The careful management of floodwater attenuation in the Upper Adur and Adur Valley will also mitigate against disruption to the A roads and railways within these policy units.

Regional Spatial Strategy for the South East There is potential for negative interaction if strategic development is located in areas at risk of flooding, such as Shoreham, Brighton and Hove and Worthing, particularly as the RSS will extend beyond the duration of this CFMP. However, given that development should only be permitted in line with PPS 25, this is unlikely to be significant. Local Development Frameworks (various) There is potential for negative interactions if the Local Plans allow significant development to occur in areas at risk of flooding, due to flood risk management activities throughout the catchment, particularly as Local Plans will extend beyond the duration of the CFMP. However, given that development should only be permitted in line with PPS 25, this is unlikely to be significant. As many of these



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

planning frameworks are in the development stages, there may be opportunities for the CFMP to inform the process and strategically reduce disruption and damage during severe flood events. Beachy Head to Selsey Bill Shoreline Management Plan There is potential for positive interactions between the SMP and CFMP to reduce flood risk to Shoreham Harbour and the River Adur in the future, where the policy is to hold the line. South Downs Management Plan This plan contains policies to alleviate abstraction pressure through increased storage within the catchment, to improve river flow and reduce flood risk in vulnerable areas through floodplain and wetland restoration and maintenance of water flow to ditches. These aims are complemented very well by the policies of this CFMP although the future National Park status may bring other constraints. Land Use Management Plans (various) There is potential that positive interaction between the plans as policies may result in reduced run-off and mitigation against climate change, particularly in policy options 1, 4, 8



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

and 9. Regional Forestry and Woodlands Framework for the South East Positive interactions may potentially arise in those parts of the catchment where CFMP policies support sustainable land management, including tree planting schemes which may help to alleviate flood flows, particularly in policy options 1, 4, 8 and 9.

MED

+ N/A N/A

HIGH +

MED -

LOW - N/A HIGH

+ HIGH

+ MEDIUM +

Reduce the impact of muddy flooding.

Muddy flooding is a problem in parts of northern Brighton and Hove, Rottingdean, Woodingdean, Ovingdean, Bevendean, Worthing and Findon with a significant number of properties affected. This nuisance flooding is caused by surface water run-off and associated soil erosion from the South Downs. Changes in farming practices from pasture to arable have resulted in an associated increase in flooding and erosion. By implementing policy option 6 in the South Downs and Adur Valley, sustainable land management and agri-environment schemes will be encouraged and the natural function of the River Adur channel and floodplain will be restored where possible. This will lead to a reduction in muddy flooding through a combination of soil management, reduced surface water run-off and transportation and sedimentation processes.

Land Use Management Plans (various) There is potential that positive interaction between the plans as policies may result in reduced run-off and improved soil management, particularly in policy options 1, 4, 8 and 9. These schemes may also contribute towards restoration of natural processes which will reduce soil erosion. Regional Forestry and Woodlands Framework for the South East Positive interactions may potentially arise in those parts of the catchment where CFMP policies support sustainable land management, including tree planting schemes which may help to alleviate run-off and soil erosion, particularly in policy options 1, 4, 8



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

and 9. The High Weald AONB Management Plan There are objectives within the AONB Management Plan to reduce flood risk through restoration and protection of functional floodplains which is a direct opportunity for positive interactions with the CFMP. South Downs Management Plan This plan contains policies to improve river flow through floodplain and wetland restoration and maintenance of water flow to ditches. This will interact positively with objectives to reduce surface water run-off and soil erosion in the South Downs.

MED

+ HIGH

+ MED

- MED

+ MED

- MED

- HIGH

+ MED

+ MED

+ LOW +

Ensure flood damages do not significantly increase in the future (for example due to climate change).

Across the CFMP area, AAD due to the flooding of properties and agricultural land currently stands at approximately £5 million, the majority of which occurs in the densely populated Lower Adur and Ferring Rife catchments. This is expected to rise by a further £10 million in the future. The strategy of increasing water storage capacity in the upper catchment and increasing flood defences around high-risk urban areas such as Steyning, Upper Beeding and Shoreham will ensure that AAD to both properties and agricultural land will not increase significantly in the future. It is also expected that carefully managed floodwater attenuation in the upper catchment will be sufficient to ensure flood risk does not increase in the future in downstream Worthing, Brighton, Hove, Steyning and Upper Beeding

Regional Spatial Strategy for the South East There is potential for negative interaction if strategic development and infrastructure is located in areas at risk of flooding, such as Shoreham, Brighton and Hove and Worthing, particularly as the RSS will extend beyond the duration of this CFMP. However, given that development should only be permitted in line with PPS 25 this is unlikely to be significant.



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

without the need to increase FRM in these urban areas. The AAD to agricultural land can be managed through carefully controlled flood attenuation in the upper catchment which will reduce risk within these policy units and should be located in areas where additional damages will not be sustained. By encouraging the uptake of agri-environment schemes in these parts of the catchment, further reductions in AAD may be achieved, as well as other environmental benefits.

Local Development Frameworks (various) There is potential for negative interactions if the Local Plans allow significant development to occur in areas at risk of flooding, due to flood risk management activities throughout the catchment, particularly as Local Plans will extend beyond the duration of the CFMP. However, given that development should only be permitted in line with PPS 25, this is unlikely to be significant. Plans for growth in areas of Worthing, Brighton and Hove and Shoreham are likely to lead to increased damages in the future, however, the CFMP has taken these increased risks into consideration during policy appraisal and will interact to reduce or prevent an increase in these effects where possible. Beachy Head to Selsey Bill Shoreline Management Plan There is potential for positive interactions between the SMP and CFMP to reduce flood risk to Shoreham Harbour and the River Adur in the future, where the policy is to hold the line. South Downs Management Plan This plan contains policies to alleviate abstraction pressure through increased storage within the catchment, to improve river



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

flow and reduce flood risk in vulnerable areas through floodplain and wetland restoration and maintenance of water flow to ditches. These aims are complemented very well by the policies of this CFMP although the future National Park status may bring other constraints. Land Use Management Plans (various) There is potential for positive interactions where the CFMP implements policies that support and encourage sustainable land management practices, which may reduce the velocity and volume of run off, particularly in policy units 1, 4, 8 and 9. Regional Forestry and Woodlands Framework for the South East Potentially positive interactions where the CFMP encourages more sustainable land management practices and opportunities to increase tree planting may help to alleviate flood flows, particularly in policy option 1, 4 8 and 9.

HIGH

+ HIGH

+ LOW

+ HIGH

+ LOW

+ MED

- HIGH

+ HIGH

+ HIGH

+ HIGH +



Catchment objective

PU1

P6

PU2

P4

PU3

P3

PU4

P6

PU5

P3

PU6

P3

PU7

P4

PU8

P6

PU9

P6

Sum of

policy unit

impacts


and Programmes

Ensure that river channel and flood defence maintenance expenditure is appropriate to the economic damage of flooding.

Whether the cost of FRM expenditure is justifiable and appropriate has been assessed by comparing the ratios of AAD prevented (the difference between policy option 1 and the policy option chosen) and the annual cost of FRM within a policy unit, for each policy option. This tests whether the annual costs of FRM do not exceed the AAD prevented, in which case it is considered appropriate and justifiable. The cumulative effects of the policies chosen in this CFMP are highly positive in terms of this measure. Nearly every policy chosen for every policy unit is shown to have positive effects, which demonstrates that there are few losses sustained under this CFMP and that nearly every unit of FRM expenditure brings returns greater than one equivalent unit of AAD prevented. The highest returns are made under policy options 1, 2, 4, 7, 8 and 9 which cover the large rural areas of the Adur catchment, the South Downs, Shoreham and Burgess Hill. The only policy unit in which the ratio is unacceptable is Brighton and Hove, where policy option 3 limits the gains in terms of AAD prevented. However, it is the aim of this CFMP to further reduce AAD through strategic attenuation of flood water upstream.

See above


B4.4 Mitigation and Enhancement

At this level of policy making, where we are setting the direction for future actions, the mitigation and enhancement measures are integral to the policy appraisal. Where we have the potential to enhance the environment we have included this potential within the appraisal as opportunities. Mitigation measures at this level are generally included as part of the policy options, so that a less detrimental impact will tend to be implicit within an alternative policy option. At a lower level in our planning hierarchy, when we are investigating the details of how we will implement flood risk management measures, we will be undertaking an appropriate level of environmental assessment and consultation which will, in turn, identify more relevant mitigation measures to the impacts arising. We will use the assessment of impacts undertaken at this level to help focus our lower levels of decision making, ensuring that relevant mitigation and enhancement measures are explored fully. Where Table B5 identifies potential benefits / impacts between the CFMP and other plans / programmes operating within the catchment we will take this into account when developing further proposals, as set out above.

B4.5 Monitoring

SEA requires significant environmental effects related to the implementation of the plan to be monitored. Information on the monitoring requirements related to the implementation of the CFMP is included in the appraisal tables presented in Section B4.2.

The monitoring of the significant effects of the plan will be based on the following indicators (in no particular order):

a) Change in AAD to properties (£); b) Change in AAD to agricultural land (£); c) Change in estimated damages resulting from surface water flooding (£) d) Change in number of people affected by 1% annual probability flood outline; e) Change in estimated number of properties affected by surface water and/or

groundwater flooding; f) Change in the estimated number of properties affected by downland ‘muddy’ surface

water flooding; g) Change in length of main roads affected by 1% annual probability flood outline (km); h) Change in number of critical infrastructure sites affected by the 1% annual probability

fluvial flood event; i) Change in the number and period of recorded A road and railway closures due to

surface water flooding; j) Change in the number if critical infrastructure sites recorded as being affected by

surface water flooding; k) Change in balance of annual river channel and flood defence maintenance (£) to annual

average damages from fluvial flooding to agriculture (£); l) Change in area of naturally active floodplain restored (km2); m) Change in length of naturally functioning river (km); n) Achievement of BAP targets and improved habitat quality and species diversity; and o) Change in landscape character assessment of the AONB, ESA and/or proposed

National Park.

References Project Appraisal Guidance – Supplementary Guidance: Treatment of climate change impacts. Defra October 2006. (http://www.defra.gov.uk/environ/fcd/pubs/pagn/climatechangeupdate.pdf)

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