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Summary Report June 2012

West Dorset Catchment Flood Management Plan

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June 2012

Environment Agency West Dorset Catchment Flood Management Plan 1

Introduction

I am pleased to introduce our summary of the West Dorset

Catchment Flood Management Plan (CFMP). This CFMP gives an

overview of the flood risk in the West Dorset catchment and sets

out our preferred plan for sustainable flood risk management over

the next 50 to 100 years.

The West Dorset CFMP is one of 77 CFMPs for Englandand Wales. Through the CFMPs, we have assessedinland flood risk across all of England and Wales for thefirst time. The CFMP considers all types of inlandflooding, from rivers, ground water, surface water andtidal flooding, but not flooding directly from the sea(coastal flooding), which is covered by ShorelineManagement Plans (SMPs). Our coverage of surfaceand ground water is however limited due to a lack ofavailable information.

The role of CFMPs is to establish flood risk managementpolicies which will deliver sustainable flood riskmanagement for the long term. This is essential if weare to make the right investment decisions for thefuture and to help prepare ourselves effectively for theimpact of climate change. We will use CFMPs to help ustarget our limited resources where the risks aregreatest.

This CFMP identifies flood risk management policies toassist all key decision makers in the catchment. It wasproduced through a wide consultation and appraisalprocess, however it is only the first step towards anintegrated approach to Flood Risk Management. As weall work together to achieve our objectives, we mustmonitor and listen to each others progress, discusswhat has been achieved and consider where we mayneed to review parts of the CFMP.

There are several sources of flood risk within the WestDorset catchment, including fluvial, surface water, andtidal flooding. Fluvial flood risk is associated with theRivers Char, Brit, Bride and Wey. Over half of allproperties at risk and economic damages due toflooding are in Bridport. There are also a significantnumber of properties at risk in Beaminster, BurtonBradstock, and Nottington.

We cannot reduce flood risk on our own, we willtherefore work closely with all our partners to improvethe co-ordination of flood risk activities and agree themost effective way to manage flood risk in the future.We have worked with others including Dorset CountyCouncil, Natural England, South West Water and theNational Farmers Union to develop this plan.

This is a summary of the main CFMP document, if youneed to see the full document an electronic version canbe obtained by emailing [email protected] or alternatively paper copies can be viewed at any ofour offices in South West Region.

Richard CresswellSouth West Regional Director

2 Environment Agency West Dorset Catchment Flood Management Plan

The purpose of a CFMP in managing flood risk 3

Catchment overview 4

Current and future flood risk 6

Future direction for flood risk management 10

Sub-areas

1 Bridport sub-area 12

2 Weymouth Urban Areas sub-area 14

3 Beaminster sub-area 16

4 Burton Bradstock sub-area 18

5 Charmouth sub-area 20

6 West Dorset Rural Areas sub-area 21

7 Isle of Portland sub-area 22

Map of CFMP policies 23

Contents


The purpose of a CFMP in managing flood riskCFMPs help us to understand thescale and extent of flooding now andin the future, and set policies formanaging flood risk within thecatchment. CFMPs should be used toinform planning and decisionmaking by key stakeholders such as:

• the Environment Agency, who willuse the plan to guide decisionson investment in further plans,projects or actions;

• Regional Assemblies and localauthorities who can use the planto inform spatial planningactivities and emergencyplanning;

• Internal Drainage Boards (IDB),water companies and otherutilities to help plan theiractivities in the wider context ofthe catchment;

• transportation planners;

• land owners, farmers and landmanagers that manage andoperate land for agriculture,conservation and amenitypurposes;

• the public and businesses toenhance their understanding offlood risk and how it will bemanaged.

Figure 1. The relationship between CFMPs, delivery plans, projects and actions

CFMPs aim to promote moresustainable approaches tomanaging flood risk. The policiesidentified in the CFMP will bedelivered through a combination ofdifferent approaches. Together withour partners, we will implementthese approaches through a rangeof delivery plans, projects andactions.

The relationship between the CFMP,delivery plans, strategies, projectsand actions is shown in Figure 1.

Policy planning• CFMPs and Shoreline Management Plans.

• Action plans define requirement for deliveryplans, projects and actions.

Note: Some plans may not be led by us – we may identify theneed and encourage their development.

Policy delivery plans (see note)• Influence spatial planning to reduce risk and

restore floodplains.

• Prepare for and manage floods (including localFlood Warning plans).

• Managing assets.

• Water level management plans.

• Land management and habitat creation.

• Surface water management plans.

Projects and actions• Make sure our spending delivers the best

possible outcomes.

• Focus on risk based targets, for example numbersof households at risk.


The river catchments that make upthe West Dorset CFMP are (from westto east) the Char, Brit, Bride andWey, each flowing directly into thesea on the south coast.

The West Dorset CFMP covers an areaof some 370 square kilometres (140square miles). Annual rainfall ranges1,000mm (40in) over higher groundto less than 750mm (30in) on thecoast. The England and Walesaverage is 920mm (36in).

The topography of the area istypically characterised by broad,bowl shaped vales incised by steepsided river valleys. All of thesecatchments are small with a totalriver length of between 10km and20km and catchment areas of 50km2

to 115km2. The River Char and RiverBrit have a very rapid response torainfall. The River Bride and RiverWey are fed by chalk aquifers which

Catchment overview

tend to dampen the response unlessheavy rainfall occurs following aperiod of prolonged wet weather.

The geology of the West Dorset areais highly distinctive and has had aprofound influence on thelandscape, hydrology and land usewithin the catchment. In general, thegeology becomes progressivelyyounger from west to east. LowerJurassic sandstones and clays in thewest give way to Middle Jurassicclays and limestones further to theeast. Overlying the Jurassic strata tothe west and north east are outcropsof Cretaceous Greensand andremnants of the overlying Chalk.These are major aquifers providingbaseflow to the River Bride and RiverWey during the summer months.

The Char and Brit catchments are

subject to active geomorphologicalchange with bank erosion andsediment movement in times offlooding.

The CFMP area is predominantlyrural, the majority of land use beinggrazing and arable. The main urbanareas are Beaminster and Bridportand Weymouth. Smaller villages arescattered across the CFMP area.

The West Dorset catchment hasmany important environmentallocations. There is one Area ofOutstanding Natural Beauty, fiveSpecial Areas of Conservation (SAC),one Special Protection Area (SPA), 32Sites of Special Scientific Interest(SSSIs) and 136 ScheduledMonuments.

The River Bride and River Wey arefed by chalk aquifers which tendto dampen the response unlessheavy rainfall occurs following aperiod of prolonged wet weather.


Map 1. Location and extent of the West Dorset CFMP area

© Crown Copyright. Environment Agency 100026380.

Legend

West DorsetCFMP

Urban areas

Main rivers

Railway

Motorway

Beaminster

LymeRegis

0 3 6 9 12Kilometres

Bridport

Weymouth

Dorchester

Isle ofPortland

N

A caravan park at Freshwater, Burton Bradstock is flooded by the River Bride in October 2000


Current and future flood risk

Sources of flood risk within the WestDorset catchment include fluvial,surface water and tidal flooding.

Fluvial flood risk is associated withthe Rivers Char, Brit, Bride and Wey.Over half of all properties at risk andeconomic damages due to floodingare in Bridport. There are alsosignificant numbers of properties atrisk in Beaminster, Burton Bradstockand Nottington. Several designatedenvironmental sites and historicalfeatures are also at risk of flooding.However, the number of caravan,camping and holiday parks at risk isa particular issue in this area.

Although a flood warning system isin place for the River Char, Brit,Asker, Bride and Wey, in someareas, particularly upstream, there isless than two hours warning of animpending flood. There is no floodwarning for many locations next tosmaller watercourses.

Overview of the current flood risk

Today, there are approximately 700properties across the catchment atrisk of flooding from rivers and thetide, at a 1 per cent annualprobability (rivers) or 0.5 per centannual probability (tidal) event.

Also at risk are a water treatmentworks, two sewage treatment works,a fire station, two police stations, acare home, two health centres and aschool.

The area includes a number ofcaravan, camping and holiday parksthat represent highly vulnerablecommunities at risk of flooding.

Within the floodplain are also anumber of designated sites,including Radipole Lake SSSI,Lodmoor SSSI and parts of theSidmouth to West Bay SAC, WestDorset SAC and Chesil and Fleet SPA,SAC and SSSIs.

What is at risk?

‘….As the five foot deep floodwaters receded in Weymouth….Sixhundred people had been forced outof their homes and caravans. Thedevastation was caused by a rainfallof more than seven inches.’ 1955

Table 2. Critical infrastructure at risk:

1 electricity substation, 3 emergency services, 1 A road, 2 water treatment works

Number of properties at risk Locations

500 to 1,000 None

100 to 500 Beaminster, Preston, Bridport

50 to 100 Nottington and Broadwey

25 to 50 Burton Bradstock


Table 1. Locations of towns and villages with 25 or more properties at risk in a 1% annual probability river flood

Map 2. Flood risk to property in a 1% annual probability river flood, taking into account current flood defences


Legend

Properties with a 1%chance of flooding

25 - 100

101 - 250

251 - 500

501 - 1,000

West Dorset CFMPMain rivers

N

Beaminster


Bridport

Westham

Nottington

BurtonBradstock

Preston


How we currently manage the risk

Our activity is prioritised on a riskbasis. Our main activities include:

• Flood risk mapping – A major partof the programme is Flood Zoneimprovements and HazardMapping.

• Managing development – Ourdevelopment control teamsupports the planning process byensuring that new developmentshave the appropriate flood riskassessments and follow PPS25(Government Planning PolicyStatement on Flood Risk).

• Flood warning – a multi-mediawarning service called FloodlineWarnings Direct provides targetedwarnings to people via differentmedia methods, includingtelephone, email and SMS textmessaging. This is available forCharmouth, Beaminster, Bridport,Burton Bradstock, Upwey,Nottington and Broadwey,Radipole to Southill and Westhamto Harbour. We also provide a

public access telephone servicecalled Floodline that people canring to check if there is a floodwarning for their area. MajorIncident Plans have beendeveloped for Beaminster, forBridport, Burton Bradstock andWest Bay, for Weymouth, for theWey villages (of Upwey, Broadwey,Nottington and Radipole), and fortidal flooding at both Chiswell andfor the A353 Preston Beach Road.Major Incident Plans are beingdeveloped for Charmouth and forPreston and Jordan Brooks.

• Flood defence schemes – We haveschemes at Beaminster, Bridport,Burton Bradstock, Nottington andPreston.

• Maintenance – We maintainchannels and defences.

The distribution of potential floodrisk from rivers and tides isillustrated in Map 2 for a flood with a1% annual probability (0.5% fortides) of occurring or beingexceeded.

The greatest concentration ofproperties at risk of flooding is atBridport. Here some 420 propertiesare at risk from river, tidal andsurface water flooding. This is set toincrease due to rising sea levels.

Beaminster has the next highestconcentrations in property at riskwith some 110 properties at riskrespectively.

In addition to these locations, thereare risks of surface water flooding,which can be deep and fast flowing,across much of the catchment.However, further studies followingon from the CFMP are needed by usand our partners to quantify thispotential risk.

Where is the risk?

➜Policemen deliver milk by boat toflooded families in Marsh Road,Weymouth in July 1955


The impact of climate change and future flood risk

It is widely accepted that our climateis changing and increasing peak riverflows and sea levels will have asignificant effect on flood risk. Landuse and management changes in thecatchment will also affect thefrequency and magnitude offlooding. Increased urbanisation inthe CFMP catchment over the next100 years, particularly in theWeymouth area, could result in anincrease in flood risk to people andproperties over the long term. Wehave combined these factors withdifferent ways of managing flood riskto forecast flood risk in the future.

Sensitivity testing showed that therewould be no measurable change inpeak flows outside the waycatchment.

We have used the following futurescenario in the West Dorset CFMP:

• 20% increase in peak flows due toclimate change.

• Sea level rise of 950mm due toclimate change.

• 10% increase in peak flows in theWey Catchment due to urbandevelopment.

• 5% increase in peak flows due torural land use and managementpractice.

Bridport, Nottingham and Broadweyare expected to se the greatestincrease in the number of propertiesat risk in the future (see Figure 2).

0

100

200

300

400

500

600

700

Bridport Beaminster Nottington and Broadwey Burton Bradstock

Current Future

Num

ber o

f Pro

pert

ies

at F

lood

Ris

k

Figure 2. Current and future (2100) flood risk to property from a 1% annualprobability river flood, taking into account current flood defences


Approaches in each sub-area

We have divided the West Dorset catchment into sevendistinct sub-areas which have similar physicalcharacteristics, sources of flooding and level of risk. We have identified the most appropriate approach tomanaging flood risk for each of the sub-areas andallocated one of six generic flood risk managementpolicies, shown in Table 2.

To select the most appropriate policy, the plan hasconsidered how social, economic and environmentalobjectives are affected by flood risk managementactivities under each policy option.

Map 3. West Dorset sub-areas

Chard

Preston

Weymouth

Bridport

AxminsterBeaminster

Charmouth

Dorchester

Charminster

Fortuneswell

BlandfordForum

Easton and Weston

BurtonBradstock



N

LegendWest Dorset CFMP

Sub-area

Bridport (Policy 4)

Weymouth Urban Area (Policy 4)

Beaminster (Policy 4)

Burton Bradstock (Policy 3)

Charmouth (Policy 3)

West Dorset Rural Areas (Policy 1)

Isle of Portland (Policy 1)

1

2

3

4

5

6

7

8

9

Future direction for flood risk management

➜ A road at Upwey affected by flooding from the River Weyin July 1955


Policy 1

Areas of little or no flood risk where we will continue to monitor and advise

This policy will tend to be applied in those areas where there are very few properties at risk of flooding. It reflects a commitment to work with the natural flood processes as far as possible.

Policy 2

Areas of low to moderate flood risk where we can generally reduce existing flood risk management actions

This policy will tend to be applied where the overall level of risk to people and property is low to moderate.It may no longer be value for money to focus on continuing current levels of maintenance of existing defencesif we can use resources to reduce risk where there are more people at higher risk. We would therefore reviewthe flood risk management actions being taken so that they are proportionate to the level of risk.

Policy 3

Areas of low to moderate flood risk where we are generally managing existing flood risk effectively

This policy will tend to be applied where the risks are currently appropriately managed and where the risk offlooding is not expected to increase significantly in the future. However, we keep our approach under review,looking for improvements and responding to new challenges or information as they emerge. We may reviewour approach to managing flood defences and other flood risk management actions, to ensure that we aremanaging efficiently and taking the best approach to managing flood risk in the longer term.

Policy 4

Areas of low, moderate or high flood risk where we are already managing the flood risk effectively but where wemay need to take further actions to keep pace with climate change

This policy will tend to be applied where the risks are currently deemed to be appropriately-managed, butwhere the risk of flooding is expected to significantly rise in the future. In this case we would need to do morein the future to contain what would otherwise be increasing risk. Taking further action to reduce risk will requirefurther appraisal to assess whether there are socially and environmentally sustainable, technically viable andeconomically justified options.

Policy 5

Areas of moderate to high flood risk where we can generally take further action to reduce flood risk

This policy will tend to be applied to those areas where the case for further action to reduce flood risk is mostcompelling, for example where there are many people at high risk, or where changes in the environment havealready increased risk. Taking further action to reduce risk will require additional appraisal to assess whetherthere are socially and environmentally sustainable, technically viable and economically justified options.

Policy 6

Areas of low to moderate flood risk where we will take action with others to store water or manage run-off inlocations that provide overall flood risk reduction or environmental benefits

This policy will tend to be applied where there may be opportunities in some locations to reduce flood risklocally or more widely in a catchment by storing water or managing run-off. The policy has been applied toan area (where the potential to apply the policy exists), but would only be implemented in specific locationswithin the area, after more detailed appraisal and consultation.

Table 3. Policy options


Bridport

Sub-area 1

The issues in this sub-area

Bridport sub-area covers the town ofBridport and the area south to WestBay. Around 420 properties arewithin the 1% annual probabilityflood extent (ignoring the influenceof defences). In the future, thisnumber is expected to increase to590. In general the degree of floodhazard is low, with a small numberof properties at risk from amoderate or significant hazard dueto deep or fast flowing floodwater.In more extreme flooding up to 700properties are at risk.

Our key partners are:

West Dorset District Council

Dorset County Council

Wessex Water

Natural England

Dorset Wildlife Trust

National Farmers Union

Landowners/ local farmers

Infrastructure at risk of floodingincludes the A3066, a watertreatment works, a sewagetreatment works, a fire station,police station, a number ofelectricity sub-stations, a carecentre and two health centres. Thecaravan / holiday parks in the WestBay area are also at risk.

A flood warning service in Bridportcovers fluvial flooding from the RiverBrit and River Asker, but not from theRiver Simene. Current lead times are2 to 3 hours for the Brit, but there isno lead time for the Asker.

There are fluvial defences inBridport, as well as at Bradpole andPymore. These comprise of masonryand concrete walls andembankments. Channel siltationthrough Bridport can causeproblems by reducing channelcapacity, and we have identified theneed to investigate the link betweensoils and run-off to establishwhether solutions can be found toreduce current risk. Furthermore,there is risk of flooding in Bridport ifhigh fluvial flows coincide with anextreme tide, this is controlled bythe tidal sluice gates at West Bay.

The vision and preferred policy

Policy Option 4- we are alreadymanaging the flood risk effectivelybut we may need to take furtheractions to keep pace with climatechange.

Under this policy 600 propertiescould continue to be protected to a1% standard and only be affectedby the most extreme events. Risk tocritical infrastructure, and thecaravan/holiday parks would alsobe reduced. There is opportunity toimprove floodplain connectivity andinvestigate opportunities to restoreany drained and degraded wetlandhabitat.


Proposed actions to implement the preferred policy

• Improve flood forecasting, flood warning, flood awareness, flood incident management and emergencyresponse. The area is classified as a Rapid Response Catchment.

• Identify areas in Bridport where surface water run-off issues are causing problems.

• Ensure spatial planning and development does not increase flood risk (PPS25).

• Review licences and investigate possible relocation of caravan and camping sites currently at risk, forexample on the west side of the lower Brit.

• Investigate whether critical infrastructure currently at risk, can be relocated over the longer term.

• Determine the link between soils and run-off in the catchment. Currently maintenance comprises mainlyremoval of silts from watercourses which this action aims to reduce.

• Investigate opportunities to restore drained and degraded wetland. Increase floodplain connectivity (e.g.at Asker Meadows Local Nature Reserve). Modify or improve the existing flood alleviation scheme on thelower Asker.

• Investigate if there are any feasible opportunities for smaller on-line storage options for the River Brit andtributaries.

➜ The centre of Bridport flooded by the River Brit in February 1974


Weymouth urban areas

Sub-area 2


The area covers the Wey catchmentincluding Upwey, Nottington,Broadwey and Weymouth, and alsothe Preston Brook and River Jordan.Included within the floodplain arethe Lodmoor SSSI, Radipole LakeSSSI and the Portland HarbourShore SSSI.

At Nottington, Broadwey, Upwey,Radipole and Westham,approximately 100 properties are at


Weymouth and Portland BoroughCouncil

Dorset County Council

Wessex Water

Natural England

Royal Society for the Protection ofBirds (RSPB)



risk from a 1% annual probabilityflood on the River Wey. This numbercould increase to 275 in the future.A further 150 properties are at riskfrom the River Jordan and PrestonBrook. Roads in Weymouth andlisted buildings are also at risk.

Various Environment Agency, LocalAuthority and private defences arein place in Nottington, Upton andBroadwey, to the west side ofRadipole Lake, on either side ofWeymouth harbour, and along thePreston Brook and River Jordan.

Flooding problems are alsoassociated with a line of springs inUpwey.

A flood warning service is in placeon the Wey. The maximum floodwarning lead time increasesdownstream through the area up toapproximately 6 hours inWeymouth.

There is a legacy of inappropriatedevelopment in the Wey floodplain,this includes a number of caravanand camping sites at risk. Over thelonger term relocation options needinvestigation.


Policy Option 4 - we are alreadymanaging the flood risk effectivelybut we may need to take furtheractions to keep pace with climatechange.

Under this policy some of theproperties in the Wey catchmentwould continue to be undefended.Depending on the measures taken,there is significant opportunity tobenefit the environment under thispolicy option.



• Ensure spatial planning and development does not increase flood risk (PPS25).

• Review current surface water drainage in the Wey catchment. Assess possible solutions, identify andretro-fit Sustainable Drainage Systems (SuDs) where appropriate. Ensure that SuDs are incorporated aspart of the development of the new Weymouth Relief Road.

• Investigate whether any inappropriate development in the Wey floodplain can be relocated in themedium to long term. Evaluate risk to critical infrastructure and whether this can be relocated.

• Review licences and possible relocation of the caravan and camping sites that are currently in the at riskareas, particularly from the River Jordan.

• Investigate whether any mitigation measures can be taken to resolve flooding problems in Upwey from aline of springs.

• Carry out a siltation study in the Wey catchment in partnership with the RSPB, and in support of theRSPB’s ‘Siltation Study at Radipole Lake SSSI’, which will inform site management at Radipole Lake aswell as informing flood risk management.

• Use the results of the siltation study to review current drainage issues at Radipole Lake and whether theflood risk to properties in Radipole village can be reduced.

• Investigate opportunity for creation of floodplain grazing marsh for the benefit of flood risk management.

➜ Weymouth’s Westham coach park overlooking Radipole Lake is hit by flooding from the River Wey in July 1955


Beaminster

Sub-area 3


Beaminster is a small town locatedin a bowl shaped vale at theheadwaters of the River Brit and theconfluence of several smallertributaries.

The rivers draining to Beaminsterhave a very rapid (almostinstantaneous) response to heavyrainfall. Although a flood warningservice is available for the River Brit,this is based on the gauging stationat Netherbury, downstream ofBeaminster, and consequently thereis no flood warning lead time inBeaminster.

In total just over 100 properties arewithin the current 1% annualprobability flood extent and this is



Highways Authority

Wessex Water

Residents / Asset Owners

not expected to change in thefuture. The police station inBeaminster and parts of the A3066are also at risk of flooding, as wellas 32 listed buildings.

Flood defences in Beaminstercomprise a mixture of flood walls,embankments, and culverts - manyof these are private. However, anEnvironment Agency scheme wasalso built in 1985 in response to theflooding of 1979 that affected 70properties.

Many of the existing defences inBeaminster are private and there isconsiderable reliance on these.

We are currently developing SystemAsset Management Plans (SAMPs)that will enable an improvedunderstanding of flood defenceassets including reliance on private‘third party’ assets, and whether itmay be appropriate for these to bebrought under Environment Agencyresponsibility.

However, there is also a need tobetter understand storm watermanagement in Beaminster and wehave identified a study of this withour partners.


Policy Option 4 - we are alreadymanaging the flood risk effectively,but we may need to take furtheractions to keep pace with climatechange.

This policy would ensure that floodrisks to the 100 properties affecteddoes not increase. There areconsidered to be no significantenvironmental losses or gains underthe policy, although there isopportunity to implementmeasures, such as opening upculverts and influencing good landmanagement, for the benefit of theenvironment as well as flood riskmanagement.


Proposed actions to implement the preferred approach

• Continue ongoing work on development of System Asset Management Plans (SAMPs) which will enableimproved understanding of flood defences in Beaminster, reliance on private ‘third party’ assets andwhether it may be appropriate for these to be brought under Environment Agency responsibility.

• Carry out a study to determine the current Standard of Protection in Beaminster, and how flood risk canbe managed appropriately in the future. This will include investigating ways in which hydraulic andenvironmental improvements can be made to the tributary streams through Beaminster (for example byopening up of culverted sections).

• Carry out a Surface Water Management Plan with West Dorset District Council, the Dorset County CouncilHighways Authority and Wessex Water.

• Review current flood forecasting and flood warning procedures in Beaminster. Note that this is classifiedas a Rapid Response Catchment.


Burton Bradstock

Sub-area 4


Burton Bradstock is a small coastalsettlement located to the east ofBridport and near to the outflow ofthe River Bride. Approximately 25properties are within the 1% annualprobability flood extent, althoughthe degree of flood hazard is low.This number would be expected toincrease to around 30 in the future.



Burton Bradstock Parish Council

Wessex Water

Highways Authority


Dorset Area of Outstanding NaturalBeauty

Land Owners


In addition to these risks, caravan/holiday sites, a school, 9 listedbuildings and the B3157 are at riskof flooding.

Flood risk can be exacerbated bystormy conditions raising ChesilBank and blocking the outlet of theRiver Bride into the sea. This causeswater levels to back up in BurtonBradstock.

An Environment Agency flooddefence scheme is maintained onthe River Bride in Burton Bradstock,comprising raised flood walls andembankments. There are issues ofsedimentation in this scheme due tosurface water run-off from ruralareas which requires more frequentmaintenance.

There may also be options to realignthe river channel back to its originallocation.

A flood warning service is in place inBurton Bradstock, covering fluvialflooding from the River Bride. Theflood warning lead time is around 1to 4 hours.


Policy Option 3 - we are generallymanaging existing flood riskeffectively.

Under this policy the standard ofprotection of defences would onlyreduce to approximately 2% by2100.

We have identified the impact ofstormy conditions raising ChesilBank and blocking the outlet of theRiver Bride into the sea. Future sealevel rise will make this worse, andas a consequence it may benecessary to amend this policy to‘Take further action to sustain thecurrent scale of flood risk into thefuture’ if estimates of sea level riseare revised upwards in the future.



• Carry out a comprehensive review of current drainage issues in Burton Bradstock, in partnership with theLocal Planning Authority, Wessex Water, Highways Authority and Parish Council. Review to include anassessment of whether realignment of the river channel back to its original location is feasible, andwhether the regulation of flows in the main river and mill stream could benefit flood risk management.

• Work with the Local Planning Authority to review licences and possible relocation of the caravan andcamping sites that are currently in the at risk areas. This is liable to require support from the LocalDevelopment Framework.

• Investigate whether land use and land management changes in the Bride catchment can reduce the risk ofsurface water run-off from rural areas that affect Burton Bradstock. Opportunities to manage the RiverBride more sensitively, particularly for water voles and the chalk stream habitat. The investigation alsoneeds to take into account issues of sedimentation from surface waters and whether actions can be takento reduce the ongoing desilting requirements.

• Depending on the outcome of our Rapid Response Catchments project, (which may include parts of theBride catchment), take further action if this is deemed appropriate.

➜ Repairing erosion at Burton Bradstock, where the River Bride flows into the sea, in October 2006


Charmouth

Sub-area 5


Charmouth is a small coastal town inthe west of the catchment,approximately 2 miles east of LymeRegis. Four properties are within thecurrent 1% annual probability floodextent and one additional propertyis expected to be at risk in thefuture. The flood risk from deep andfast flowing floodwater is low.

However, there are several caravan /holiday parks at risk of flooding.These represent highly vulnerablecommunities.

A sewage works upstream ofCharmouth is within the flood extentand may result in potential risk ofpollution to the watercourse in thefuture.

The following statutorily designatedsites may be affected by flooding inthis area:

• Sidmouth to West Bay SAC – 1%of the site is located within the1% flood extent;

• West Dorset Coast SSSI – 3% ofthe site is located within the 1%flood extent.



Caravan /Holiday Park Site Owners

The only defences in Charmouth areprivate defences consisting ofrevetments / gabions and masonrywalls.

Though a flood warning service is inplace, warnings are based on thegauging station in Charmouth so anylead time is very short.


Policy Option 3 - we are generallymanaging existing flood riskeffectively.

With the exception of flood risk tothe holiday and caravan parks,there are only a small number ofproperties at risk, and this isunlikely to increase significantly inthe future. We do not anticipate theneed for a flood defence scheme inthe future.

We will continue with our existingflood warning service.

A priority for this area is the need toinvestigate options for therelocation of the caravan / holidayparks at risk.

Proposed actions to implement thepreferred policy

• Work with the Local PlanningAuthority to review licences andpossible relocation of thecaravan/camping/holiday sitesthat are currently in the at riskareas. This may require supportfrom the Local DevelopmentFramework to allocatereplacement sites located inlower flood risk areas.

• Continue to provide a floodwarning service in Charmouth.

• Depending on the outcome of ourRapid Response Catchmentsproject, take further action if thisis deemed appropriate.


West Dorset Rural Areas


Whilst predominantly rural the WestDorset Rural Area does include anumber of small villages. A numberof these villages are designatedConservation Areas.

Flood risk in the area is low, and ingeneral from small watercourses. Intotal there are 60 properties withinthe 1% flood extent. Theseproperties are dispersed throughsmaller villages including Chideock,Netherbury, West Milton, Loders,Uploders, Askerswell, Abbotsburyand Osmington.

There are no flood defences in thearea. Fourteen listed buildings anda number of minor roads are at riskfrom a 1% flood event.

A proportion of the Chesil and FleetSPA, SAC and SSSI are within the1% annual probability floodplain.Various other statutorily designatednature conservation sites extendinto the floodplain.




We do not foresee a significantincrease in flood risk in the future.We estimate 65 properties will be inthe 1% flood extent by 2100. Thisdoes not account for futuredevelopment. However, futuredevelopment should comply withPPS25 and, due to the AONB statusof the majority of the area, is likelyto be limited.


Policy Option 1 - we will continue tomonitor and advise.

The main choice of policy wasbetween no active intervention andactively trying to increase floodingto reduce downstream risks.However, in practice much of theupland areas of the catchmentcomprise chalk and limestoneaquifers that retain rainwaterthrough infiltration and release itmore slowly as baseflow to thewatercourses. This, in effect,already attenuates rainwater and isunlikely to be enhanced by changesto land use or land managementgiven constraints of the topographyof the catchment.

Should an increase in flood risk tocommunities become apparent inthe future (through continuedmonitoring), the policy does notdiscount the possibility ofintervention if necessary.

Proposed actions toimplement the preferredpolicy

• Continue to monitor and advise.

It should be noted that there maybe some degree of overlap ofactions from other sub-areas (forexample, Burton Bradstock) intothis area.

Land use planners should complywith Planning Policy Statement 25Development and Flood Risk withdevelopment steered away fromareas at risk of flooding. Anyredevelopment within floodplainareas should seek to reduce thevulnerability of the developmentthrough: change of use,incorporating resistance andresilience measures, and ensuringappropriate flood warning andevacuation procedures.

Sub-area 6


The Isle of Portland

Sub-area 7




The Isle of Portland is a rockylimestone outcrop into the EnglishChannel at the eastern end of ChesilBeach.

There are no significantwatercourses on the Isle ofPortland. There are no significantfluvial, surface water or sewerflooding issues on the Isle ofPortland, and none from historicalflood records. This is expected toremain the same into the future.

The following statutorily designatednature conservation sites arepartially located within the 1% floodextent:

• Chesil and the Fleet SAC, SPA,Ramsar site and SSSI – between11% (78ha) and 16% (134ha) ofthe site;

• Isle of Portland SSSI – 3% (1ha)of the site.


Policy Option 1- we will continue tomonitor and advise.

Proposed actions to implement thepreferred policy

• There are no proposed actionsrelating to fluvial, surface wateror sewer flooding.

Actions relating to tidal / coastalflood risk (for example at Chiswell)are outside the remit of this CFMPand are included in the SouthDevon and Dorset ShorelineManagement Plan.

➜ Portland limestone has been quarried extensively across the island.


Map of CFMP policies

Map of the policies in the West Dorset catchment


Legend

Main rivers

Urban areas

Preferred approach

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

West Dorset CFMP

Beaminster

LymeRegis

Fortuneswell

Chard

Bridport

Weymouth

Dorchester


Axminster

N

5

6

2

1

4

3

7

1 Bridport

2 Weymouth urban areas

3 Beaminster

4 Burton Bradstock

5 Charmouth

6 West Dorset Rural Areas

7 The Isle of Portland

The sub-areas

GESW0612BWPX-E-E

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Would you like to find out more about us,or about your environment?

Then call us on 08708 506 506* (Mon-Fri 8-6)

email [email protected]

or visit our website www.environment-agency.gov.uk

incident hotline 0800 80 70 60 (24hrs)

floodline 0845 988 1188

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Date post:	12-Jul-2020
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