1 Brent Local Plan Level 2 Strategic Flood Risk Assessment September 2019 1.0 Introduction 1.1 The Strategic Flood Risk Assessment (SFRA) is a planning tool that enables the Local Planning Authority through the development of the Local Plan to select and develop sustainable site allocations with respect to flood risk. 1.2 Where decision-makers are unable to allocate all proposed development and infrastructure in accordance with the Sequential Test (i.e. steer development to areas of lowest risk of flooding), it is necessary to increase the scope of the Level 1 SFRA to provide information necessary for application of the Exception Test through the process of a Level 2 SFRA. 1.3 The Level 2 SFRA will provide more detail on the nature of flood risk in development allocations located in Flood Zones 2 or 3. This detailed flood risk information will enable the London Borough of Brent to apply the Sequential and Exception Tests within Flood Zones where there is development pressure in areas at medium or high flood risk. 1.4 The Level 2 SFRA should be read in conjunction with the West London SFRA. The consultants Metis were appointed to produce the West London SFRA on behalf of the London Boroughs of Ealing, Brent, Barnet, Hillingdon and Hounslow. This provided a detailed analysis of all sources of flooding across the study area and the impacts of climate change, and provides the context for the Level 2 SFRA. 1.5 The objectives of the Level 2 SFRA are to: provide information needed to apply the Sequential Test within specific development proposals sites at medium or high flood risk in line with the principles of National Planning Practice Guidance (NPPG); allow the flood risk for specific development proposal sites to be assessed, to ensure that development in such areas satisfies the requirements of the Exception Test; consider the detailed nature of the flood hazard, taking into account the presence of flood risk management measures such as flood defences; and inform planning policy for site allocations.
Transcript
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Brent Local Plan Level 2 Strategic Flood Risk Assessment
September 2019 July 2019
1.0 Introduction
1.1 The Strategic Flood Risk Assessment (SFRA) is a planning tool that enables the Local Planning Authority through the development of the Local Plan to select and develop sustainable site allocations with respect to flood risk.
1.2 Where decision-makers are unable to allocate all proposed development and infrastructure in accordance with the Sequential Test (i.e.
steer development to areas of lowest risk of flooding), it is necessary to increase the scope of the Level 1 SFRA to provide information necessary for application of the Exception Test through the process of a Level 2 SFRA.
1.3 The Level 2 SFRA will provide more detail on the nature of flood risk in development allocations located in Flood Zones 2 or 3. This detailed flood risk information will enable the London Borough of Brent to apply the Sequential and Exception Tests within Flood Zones where there is development pressure in areas at medium or high flood risk.
1.4 The Level 2 SFRA should be read in conjunction with the West London SFRA. The consultants Metis were appointed to produce the
West London SFRA on behalf of the London Boroughs of Ealing, Brent, Barnet, Hillingdon and Hounslow. This provided a detailed analysis of all sources of flooding across the study area and the impacts of climate change, and provides the context for the Level 2 SFRA.
1.5 The objectives of the Level 2 SFRA are to:
provide information needed to apply the Sequential Test within specific development proposals sites at medium or high flood risk in line with the principles of National Planning Practice Guidance (NPPG);
allow the flood risk for specific development proposal sites to be assessed, to ensure that development in such areas satisfies the requirements of the Exception Test;
consider the detailed nature of the flood hazard, taking into account the presence of flood risk management measures such as flood defences; and
1.6 The study area comprises the London Borough of Brent in West London. Detailed information on sources of flooding within the borough is available on the interactive SFRA webmap and webpage and therefore not repeated here.
2.0 Sequential Test 2.1 The aim of the Sequential Test is to steer development towards areas of lowest flood risk first, before allocating development within areas
of higher flood risk. Only where there are no reasonable available alternative sites suitable for the development in areas of lower flood risk, should areas of greater flood risk be considered for development.
2.2 All site allocations and proposed intensification corridors (previously developed land which could be developed at a higher density) have been screened against sources of flooding. The full screening is included as Appendix A. The screening assessment used the following key assumptions derived from the National Planning Policy Framework (NPPF), NPPG and the Level 1 SFRA.
Key Assumptions
Sites with 0% of areas in FZ2 and FZ3a/b do not require the Sequential Test (on the basis that other forms of flood risk are generally manageable on a site by site basis)
Less vulnerable sites within FZ2 and 3a/b require the Sequential Test
More vulnerable sites within FZ2 and 3a/b require the Sequential Test
More vulnerable sites in FZ3a require the Sequential and Exception Tests
Highly vulnerable sites in FZ2 require the Sequential and Exception Tests
Highly vulnerable sites are not suitable in FZ3 a/b
Water Compatible use in FZ2 and 3a/b require the Sequential Test
Level 2 SFRA where Sequential & Exception Tests are needed and FZ3 > 20% of site (and will be a significant constraint on development) or if the site is currently less than 20% in FZ3, but will be more than 20% under the selected climate change scenario (100yr +35%)
Flood Zone 3a for surface water is defined using the full 1 in 100 extent from the EA Risk of Flooding from Surface Water Map
Table 1. Screening Assessment Key Assumptions
2.3 The draft London Plan proposes to increase Brent’s annual housing target from 1,525 to 2,915. Given the scale of development required to meet housing need an extensive assessment of potential sites has been undertaken. The findings of the Sequential Test identified that the majority of development proposed for the borough is located in Flood Zone 1 – low probability, and therefore passes the Sequential Test. However, the borough’s housing target cannot be met from sites in Flood Zone 1 alone.
2.4 The local plan identifies 109 site allocations, excluding those sites with planning permission. 48 sites out of the 109 are affected by flood risk areas to some degree. Of these 11 sites are affected by fluvial flood risk and 66 surface water flood risk. The Sequential Test shows that for 61 of these, the area affected by flood risk is marginal and the vulnerable uses can be accommodated on parts of the site that are at lowest flood risk. However, 12 of the sites require undertaking of an Exception Test and a Level 2 SFRA to inform the test – 7 due to fluvial flood risk and the remainder due to surface water. The full appraisal is included in Appendix A. Table 2 has been reproduced from the PPG and identifies when the Exception Test is required. The vulnerability classifications for different types of development can be identified from Table 3.
Flood Zones Flood Risk Vulnerability Classification
Essential Infrastructure Highly Vulnerable More Vulnerable Less Vulnerable Water Compatible
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2 Exceptions Test
required
3a Exceptions Test
requited
X Exceptions Test
required
3b Exceptions Test
required
X X X
Table 2. When the Exception Test is Required (Extracted from PPG) Classification Uses
Essential
Infrastructure
Essential transport infrastructure (including mass evacuation routes) which has to cross the area at risk.
Essential utility infrastructure which has to be located in a flood risk area for operational reasons,
including electricity generating power stations and grid and primary substations; and water treatment
works that need to remain operational in times of flood.
Wind turbines.
Highly
Vulnerable
Police and ambulance stations; fire stations and command centres; telecommunications installations
required to be operational during flooding.
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Emergency dispersal points.
Basement dwellings.
Caravans, mobile homes and park homes intended for permanent residential use.
Installations requiring hazardous substances consent. (Where there is a demonstrable need to locate
such installations for bulk storage of materials with port or other similar facilities, or such installations
with energy infrastructure or carbon capture and storage installations, that require coastal or water-side
locations, or need to be located in other high flood risk areas, in these instances the facilities should be
classified as ‘Essential Infrastructure’).
More
Vulnerable
Hospitals
Residential institutions such as residential care homes, children’s homes, social services homes, prisons
and hostels.
Buildings used for dwelling houses, student halls of residence, drinking establishments, nightclubs and
hotels.
Non–residential uses for health services, nurseries and educational establishments.
Landfill* and sites used for waste management facilities for hazardous waste.
Sites used for holiday or short-let caravans and camping, subject to a specific warning and evacuation
plan.
Less
Vulnerable
Police, ambulance and fire stations which are not required to be operational during flooding.
Buildings used for shops; financial, professional and other services; restaurants, cafes and hot food
takeaways; offices; general industry, storage and distribution; non-residential institutions not included in
the ‘more vulnerable’ class; and assembly and leisure.
Land and buildings used for agriculture and forestry.
Waste treatment (except landfill* and hazardous waste facilities).
Minerals working and processing (except for sand and gravel working).
Water treatment works which do not need to remain operational during times of flood.
Sewage treatment works, if adequate measures to control pollution and manage sewage during flooding
events are in place.
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Water-
compatible
Development
Flood control infrastructure.
Water transmission infrastructure and pumping stations.
Sewage transmission infrastructure and pumping stations.
Sand and gravel working.
Docks, marinas and wharves.
Navigation facilities.
Ministry of defence installations.
Ship building, repairing and dismantling, dockside fish processing and refrigeration and compatible
Amenity open space, nature conservation and biodiversity, outdoor sports and recreation and essential
facilities such as changing rooms.
Essential ancillary sleeping or residential accommodation for staff required by uses in this category,
subject to a specific warning and evacuation plan.
Table 3. Vulnerability Classification (Extracted from PPG)
3.0 Exceptions Test 3.1 The purpose of the Exception Test is to ensure that new development is only permitted in medium and high flood risk areas where flood
risk is clearly outweighed by other sustainability factors and where the development will be safe during its lifetime, considering climate change. The Exception Test comprises two criteria, both of which must be satisfied before a development may be considered appropriate within an area of medium or high flood risk.
3.2 Part 1 – wider benefits to the community that outweigh flood risk
3.3 The PPG states ‘Evidence of wider sustainability benefits to the community should be provided, for instance, through the sustainability appraisal. If a potential site allocation fails to score positively against the aims and objectives of the sustainability appraisal, or is not otherwise capable of demonstrating sustainability benefits, the local planning authority should consider whether the use of planning conditions and/or planning obligations could make it do so. Where this is not possible the Exception Test has not been satisfied and the allocation should not be made.’
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3.4 Table 4 and 5 provide a policy review in relation to each site where the Exceptions Test and Level 2 SFRA is required, which considers the potential for wider benefits to the community.
Site Wider Benefits
Bridge Park & Unisys In the London Plan this site is within an Area for Regeneration, being in the top 20% most
deprived areas. The site is wholly brownfield. In its current state the site is of a poor
environmental quality, with dated buildings and the long-term vacant Unisys buildings which on
numerous occasions have been subject to anti-social behaviour such as extensive fly-tipping. It
contrasts with the attractive environment created elsewhere in Stonebridge through modern
development. Redevelopment would improve the environmental quality of the area and create
an attractive gateway to the borough and Stonebridge.
Comprehensive mixed-use development is needed to help facilitate a new leisure centre and to
bring the Unisys buildings back in use. The development will meet an identified need for a new
leisure centre and swimming pool in the south of the borough, as identified in the Council’s
Indoor Sports Facility Strategy. The Council does not own a site of sufficient size to provide
such a facility in the south of the borough which is sequentially preferable and/or which is not
designated open space.
The site benefits from good public transport access with a PTAL rating of both 3 and 4. The
NPPF and London Plan support residential development on underutilised sites in areas of good
public transport accessibility, such as this one.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Coombe Road In the London Plan this site is within an Area for Regeneration, being in the top 20% most
deprived areas. The site is used to a relatively low intensity given its position adjacent to a
main movement corridor. The McDonalds in particular is a poor piece of townscape
inconsistent with the small set back from the edge of pavement/ strong building line along the
rest of the road. Other recent developments along Neasden Lane indicates that sites can be
used more intensively to provide mixed use schemes that provide employment opportunities/
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services as well as adding to the dwelling stock. The site has good access to public transport
and local infrastructure including shops and open spaces. The Council needs to ensure
continued provision of employment space, so will seek its retention of employment uses on
site. The location of buildings and their design will have to ensure that there is no unacceptable
risk to building occupants, or property and people elsewhere as a result of any proposed
development. Setting back buildings from the watercourse provides an opportunity for their
enhancement and also potential future public access along pedestrian routes.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Watkin Road In the London Plan this site is within the Wembley Opportunity Area. It is also within the
Wembley Growth Area, which is identified to meet a significant proportion of the borough’s
housing and employment need.
The site is located in an area with good public transport accessibility levels and could improve
the public realm as a transition from the new Wembley Park development to the industrial land
located east of Wealdstone Brook. The NPPF and London Plan support residential
development on underutilised sites in areas of good public transport accessibility, such as this
one. Development at this site can bring forward an improved setting for Wealdstone Brook
including the delivery of open space and river restoration work to improve ecological diversity
and climate change adaptation.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Argenta House & Wembley Point In its current state the site is of a poor environmental quality, with dated buildings.
Redevelopment would improve the environmental quality of the area, help reduce flood risk
and create an attractive gateway to the borough and Stonebridge.
The Wealdstone Brook is not achieving good status as required by the EU Water Framework
Directive. Development on this site could facilitate naturalisation of the Wealdstone Brook,
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delivering objectives in the Thames River Basin Management Plan and Brent River Corridor
Improvement Plan, and improving water quality.
The site benefits from good public transport access being adjacent Stonebridge Park Station
and having a PTAL rating of 4. The NPPF and London Plan support residential development on
underutilised sites in areas of good public transport accessibility, such as this one.
Although the majority of the site is within flood zone 3b and therefore not suitable for
development other than water compatible uses, land within flood zone 3a could be developed
to deliver benefits to the wider community.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Brook Avenue In the London Plan this site is within the Wembley Opportunity Area. It is also within the
Wembley Growth Area, which is identified to meet a significant proportion of the boroughs
housing an employment need.
The site is located in an area with excellent public transport accessibility levels and could
improve the public realm as a gateway to the new Wembley Park development. The NPPF and
London Plan support residential development on underutilised sites in areas of good public
transport accessibility, such as this one. Given the high levels of development around this site,
it would benefit from good access to local shops and services. Redevelopment of this site can
contribute towards an improved setting for the Wealdstone Brook, including the delivery of
open space and river restoration work to improve ecological diversity and climate change
adaptation. It will also remove existing dwellings that are at risk of ground floor fluvial flooding.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
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College of North West London
Wembley
In the London Plan this site is within the Wembley Opportunity Area. It is also within the
Wembley Growth Area, which is identified to meet a significant proportion of the borough’s
housing and employment need.
The site is located in an area with excellent public transport accessibility levels. The NPPF and
London Plan support residential development on underutilised sites in areas of good public
transport accessibility, such as this one. Given the high levels of development around this site,
it would benefit from good access to local shops and services. The site is likely to be surplus to
the college’s requirements as part of a process of consolidation of better facilities on another
site within Wembley Park. The site’s location on Olympic Way provides an opportunity to
create a high quality development to act as a gateway from Wembley Park Station to the
stadium.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Stadium Retail Park & Fountain
Studios
In the London Plan this site is within the Wembley Opportunity Area. It is also within the
Wembley Growth Area, which is identified to meet a significant proportion of the borough’s
housing and employment need.
The NPPF and London Plan support residential development on underutilised sites in areas of
good public transport accessibility, such as this one which has excellent public transport
access and the close proximity to bus, rail and underground transport interchanges. The site
offers substantial development potential as an integral part of the wider Wembley Park
development area. The Wembley Masterplan suggests that there are a number of mixed use
options where creative office and other accommodation can be combined with educational and
commercial accommodation at lower levels with residential development in upper storeys.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Table 4. Policy Review – due to fluvial flood zone
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Site Wider Benefits
Turpin’s Yard This site is partly within a location identified in the London Plan as an Area for Regeneration,
being in the top 20% most deprived areas. This is a low density local employment site. The site
benefits from good public transport access having a PTAL rating of 4. The NPPF and London
Plan support residential development on underutilised sites in areas of good public transport
accessibility, such as this one.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Park Avenue Garage This is a low density local employment site. The site benefits from good public transport access
having a PTAL rating of 3/4 and being in walking distance to Willesden Green Station. The
NPPF and London Plan support residential development on underutilised sites in areas of good
public transport accessibility, such as this one.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Hereford & Exeter Court In the London Plan this site is within an Area for Regeneration, being in the top 20% most
deprived areas. It is a Growth Area and the Council is leading on a 15-year programme which
is about half way through. The Council’s objective is to improve living conditions in South
Kilburn by providing new facilities and high quality homes including 1,200 affordable homes for
social rent for existing South Kilburn secure tenants, supported by homes for market sale. The
funding model of the programme means failure to deliver one phase could prejudice the wider
masterplan for the growth area.
The existing buildings are of poor design and construction creating poor housing conditions
and potential for anti-social behaviour in communal spaces which cannot be remedied cost
efficiently through refurbishment. The opportunity exists to provide better housing along sound
urban design principles creating a human scale environment that integrates with the
surrounding area and is more sympathetic in scale to the conservation area. It will be at a
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density that reflects the PTAL rating and reinforces the street hierarchy and setting of Carlton
Vale in particular, subject to the Council being able to ensure Granville Road is reopened
between this site and the Carlton and Granville Centres which subsequently will result in the
existing Granville Open Space being developed for housing, this site will incorporate its
replacement open space. This will provide a better quality open space with greater opportunity
for sunlight penetration, overlooking/sense of security and due to its prominence more likely to
be used by the surrounding population.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Neasden Station Growth Area The London Plan identifies the area surrounding these sites as an Area for Regeneration,
being in the top 20% most deprived areas. The site adjacent to Neasden Lane is currently
mostly low intensity used Strategic Industrial Land and Locally Significant Industrial Sites that
are adjacent to a station with very high public transport accessibility. This accessibility makes
them from a planning perspective a prime site for more intensive use of land. Given Brent’s
status as a ‘provide capacity’ borough for employment space in the London Plan, the SIL and
LSIS also provide a vital role in meeting future employment needs. Site owners/ developers
are showing interest in bringing sites forward. The proposed West London Orbital route
requires appropriate safeguarding of land, but also provides an opportunity to increase the
area’s accessibility and potential for regeneration. In addition, a large potential development
site is the College of North West London’s campus which is to be disposed of to fund a move to
Wembley and improved facilities. Taking these factors together there is an opportunity to
properly plan a wider ‘Growth Area’. This can comprehensively reconsider the area’s role, to
potentially increase its performance as an employment area, but also address other strategic
needs, such as using land more effectively, providing new homes, ensure successful delivery
of a key piece of transport infrastructure and improve the image of Brent on a gateway site. It
also will assist in providing additional population to support Church End and Neasden town
centres.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
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Queensbury LSIS & Morrisons The NPPF and London Plan support residential development on underutilised sites in areas of good public transport accessibility, such as this one. Furthermore, London Plan policy encourages the comprehensive redevelopment of low-density supermarket sites.
Within the boundary of the site are two areas of locally significant industrial sites, which are not
intensively used and contain buildings which are in poor condition. Given Brent’s status as a
‘provide capacity’ borough in the London Plan, the proposed intensification and co-location at
these sites will contribute towards meeting future employment needs.
In conclusion, alternative sites would not bring the regenerative benefits and are insufficient to
provide the capacity to meet London Plan housing targets.
Table 5. Policy Review – due to surface water flood zone
3.5 The Sustainability Appraisal which underpins Brent’s Local Plan takes the form of an Integrated Impact Assessment incorporating the
requirement of Strategic Environmental Assessment, Health Impact Assessment and Equality Impact Assessment. This has created 24 criteria against which all sites are assessed. Criteria listed in Table 6 below.
Social
Prosperity, Inequalities and Social Inclusion
S1. To promote social inclusion, narrow inequalities and address poverty for all communities within the borough.
Health and Well-being
S2: To improve the health of the population and reduce health inequalities through access to necessary healthcare facilities and an
environment that promotes physical and mental well-being
Housing
S3: To provide everybody with the opportunity to live in a home which is suitable to their identified needs
Quality of surroundings
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S4: To provide a safe, high quality and healthy environment for the borough residents to live, work and enjoy.
Crime and Preventing and Community Safety
S5: To enhance community safety by reducing and preventing crime, anti-social activity and the perception of potential harm to
personal safety
Community Identity
S6: To recognise and provide for Brent’s population diversity while encouraging a shared sense of community and cultural
identity/belonging, as well as engagement in local, high quality community services and facilities
Accessibility
S7: To maintain and enhance the role and vitality and viability of Brent’s town centres and where possible improve accessibility to a
range of services and facilities, such as healthcare and education, especially for the most vulnerable
Environmental
Traffic
EN1: To reduce the effect of traffic on the environment through actively reducing the need to travel and promoting sustainable
modes of movement
Waste Management
EN2: To reduce the production of waste and use of non-renewable materials and maximising re-use and recycling.
Water Quality and Resources
EN3: To improve quality of the water bodies within the borough to ‘good’, protect ground water quality, conserve water resources
and provide for sustainable sources of water supply.
Environmental Health
EN4: Minimise air, noise and light pollution and improve existing areas of poor air quality and contaminated land.
Biodiversity
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EN5: To conserve and enhance the borough’s natural habitats, biodiversity, flora and fauna, water bodies and increase
opportunities for people to access nature in all areas of the borough.
Landscape and Townscape
EN6: Create, enhance and maintain attractive and clean environments including protecting and enhancing the borough’s landscape
and townscape.
Historic Environment and Cultural Assets
EN7: To protect and where appropriate enhance the historic environment and cultural assets.
Climate Change Mitigation
EN8: To mitigate against the impacts of climate change, predominately through reducing greenhouse gas emissions
Climate Change Adaption
EN9: Promote measures which adapt against the impact of climate change
Land and Soil
EN10: To safeguard and conserve soil quality and quantity within the borough
Open Space
EN11: Protect, enhance, and where possible increase the amount of open spaces that are high quality, easily accessible and multi-
functional.
Flood Risk
EN12: To reduce the risk of flooding and resulting detriment to public well-being, the economy and the environment
Economic
Growth and Regeneration
EC1: To actively promote sustainable, resilient and inclusive economic growth and regeneration which tangibly benefits Brent
residents and the environment
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Employment
EC2: To offer everybody the opportunity for rewarding and satisfying employment /self-employment
Investment
EC3: To facilitate both indigenous and inward investment within the borough
Education and Skills
EC4: Maximise the potential for everybody to contribute economically through increasing and improving the provision of and access
to childcare, education and training facilities, volunteering opportunities and informal employment
Efficient Infrastructure
EC5: To encourage efficient infrastructure to support economic growth
Table 6. IIA Criteria 3.6 The Brent Local Plan IIA contains an assessment for all sites in flood zone 2 and 3. In summary, although potential negative impacts in
terms of flood risk were identified, overall the sites demonstrated wider sustainability benefits that meet the objectives set in the IIA of the Local Plan. In particular, the sites scored positively against social objectives as they will help meet need for housing including affordable housing in areas which benefits from good public transport accessibility.
3.7 Part 2 – safe for its lifetime
3.8 PPG states ‘Wider safety issues need to be considered as part of the plan preparation. If infrastructure fails, then people may not be able to stay in their homes. Flood warnings and evacuation issues therefore need to be considered in design and layout of planned developments. In considering an allocation in a Local Plan a level 2 Strategic Flood Risk Assessment should inform consideration of the second part of the Exception Test.’
3.9 The lifetime of the development is considered 100 years for residential, and 60 years for non-residential as defined in the Level 1 SFRA.
3.10 There are a number of ways a new development can be made safe outlined in PPG, including by:
designing buildings to avoid flooding by, for example, raising floor levels;
providing adequate flood risk management infrastructure which will be maintained for the lifetime of the development;
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leaving space in developments for flood risk management infrastructure to be maintained and enhanced, and;
mitigating the potential impacts of flooding through design and flood resilient and resistant construction.
3.11 Specific local circumstances which need to be taken into account, include:
the characteristics of a possible flood event, e.g. the type and source of flooding and frequency, depth, velocity and speed of onset;
the safety of people within a building if it floods and also the safety of people around a building and in adjacent areas, including people who are less mobile or who have a physical impairment. This includes the ability of residents and users to safely access and exit a building during a design flood and to evacuate before an extreme flood;
the structural safety of buildings, and;
the impact of a flood on the essential services provided to a development.
3.12 The Level 1 SFRA provides detailed development management recommendations informed by the local context which will inform local plan policy. In addition, it sets out a checklist regarding what is required to be included in a Site Specific Flood Risk Assessments and Drainage Strategies, informed by the criteria above. The following section of this Level 2 SFRA provides site specific guidance for development within medium to high risk sites to ensure it’s safe for its lifetime.
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4.0 Site Assessments
SFRA Level 2 required due to fluvial flood risk
Site Name: Bridge Park
& Unisys
Site Allocation Ref. BSSA7
Location: Brentfield,
Stonebridge,
NW10 0RG
Site Area (ha): 2.7
Proposed Use: Leisure
centre, office
and
residential
Vulnerability Classification: More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
100% 100% 0
Peak flood level in a 1 in 20yr flood event
(AOD)
Peak flood level in a 1 in 100yr flood event
(AOD)
Peak modelled flow in a 1 in 100yr flood
event (cumecs)
26.27m 26.72m 111.62
The site in its entirety is within flood zone 2 and 3a. The River Brent runs approximately 60 metres to the north west of the site and is the source
of fluvial flooding. This section of the River Brent is culverted. The flood depths within the site are up to 600mm at the lowest point in the 1% (1 in
100 year) design event, and whilst relatively slow moving (and therefore unlikely to pose a direct risk to life), it is anticipated that water will sit
within the site for an extended period (exceeding 10 to 12 hours). The predicted peak design flood levels within the site are 25.03m AOD and
26.72m AOD in the 5% (1 in 20 year) and 1% (1 in 100 year) events respectively.
The EA have recorded historic flood events encompassing the north of the site including the Unisys buildings. The site does not benefit from
flood defences. Flood defences for the River Brent are located further upstream at Brent River Park.
Main River 35% Climate Change Surface Water 1 in 30yr Surface Water 1 in 100yr (increase)
100% 15% 4%
Surface water flooding is likely to increase in frequency due to climate change.
Geology and Groundwater
Groundwater susceptibility 25%-50%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is in a Critical Drainage Area and has
increased potential for elevated groundwater.
Other Sources
Sewer 57% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection
holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where
flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. Thames Water have
recorded incidents of sewer flooding surrounding to the south on land encompassing Technology House and the scrap yard, and to the north on
land surrounding the Unisys Buildings.
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Site Layout and Design
More vulnerable uses should be located on upper floors and ground floor uses made resilient and resistant to flooding. Highly vulnerable uses
and habitable basements will not be permitted on the site.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems
(SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water
runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space and green infrastructure maximised to ensure space for water to flow during times of
flood. Within flood zone 3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr
Risk of Flooding from Surface Water mapping or depth predicted for the site.
Finished Floor Levels
Finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the wider area. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
22
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to further assess the flood frequency, depth, velocity and speed of onset.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
23
Site Name: Coombe Road Site Allocation Ref. BESA1
Location: Land at Coombe Road Site Area (ha): 1.35
Proposed Use: Housing and
employment
Vulnerability
Classification:
More Vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
100% 26% 1%
Peak flood level in a 1 in 20yr
flood event (AOD)
Peak flood level in a 1 in 100yr flood
event (AOD)
Peak modelled flow in a 1 in 100yr flood event (cumecs)
31.12m 32.27m 84.73
The site is bounded on its western side by the River Brent and to the east a culverted canal feeder, both of which flows from Welsh Harp
Reservoir. As a result, the site is within flood zone 2, and the edges flood zone 3a. The river which bounds the site is functional floodplain.
24
25
Surface water flooding
Flood zone 3a 0
Climate Change
Main River 35% Climate
Change
Surface Water 1 in 30yr Surface Water 1 in
100yr (increase)
100% 0 0
Geology and Groundwater
Groundwater susceptibility 25%-50%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site has potential for elevated
groundwater.
Other Sources
Sewer 94% site
Reservoir 100% site
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection
holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where
flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. They hold no records of
historic sewer flooding instances within this site as of 2017.
Should the Welsh Harp reservoir be breached or fail, the entirety of the site would be at risk of flooding.
26
Site Layout and Design
More vulnerable uses, including residential development should be avoided in the area defined as flood zone 3a; instead less vulnerable and
water compatible uses including landscaped open space should be located here.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
Development should contribute to the restoration of the River Brent and naturalisation of waterways, providing an appropriate landscaped set-
back.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems
(SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water
runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Set-back Distance
An 8m wide undeveloped buffer strip should be retained along main rivers to provide access for maintenance. Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
27
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Particular regard should be given to procedures in the event of reservoir failure. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to assess the flood frequency, depth, velocity and speed of onset.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
28
Site Name: Watkin Road Site Allocation Ref. BCSA6
Location: Wembley, HA9 0NL Site Area (ha): 1.41
Proposed Use: Residential and employment Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
88% 17% 0
Peak flood level in a 1 in 20yr flood event
(AOD)
Peak flood level in a 1 in 100yr flood
event (AOD)
Peak modelled flow in a 1 in 100yr flood event (cumecs)
30.54m 31.37 45.76
The Wealdstone Brook runs along the northern boundary of the site and is a source of flooding. Some low areas adjoining the river are
functional flood plain, although these are outside of the site allocation boundary. 88% of the site is in flood zone 2, whilst areas to the north in
proximity to the brook are in flood zone 3a.
Modelling work to inform the Wembley Area Action Plan indicate in a fluvial flood event floodwater will inundate the site for a short period, not
exceeding 12 hours. The site has no protection from raised formal flood defences.
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The
Environment Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is in a Critical
Drainage Area. There is increased potential for elevated groundwater to the north of the site.
Other Sources
Sewer 97% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
32
Site Layout and Design
The sequential approach should be applied at site level. More vulnerable uses should be restricted to areas of lowest flood risk to the south of
the site outside of flood zone 3a. Highly vulnerable development should be avoided within this site. Encroachment into Functional Floodplain
will not be permitted. Residential basements will not be acceptable in flood zone 3a.
Flow routes should not be obstructed.
Redevelopment must deliver a measurable reduction in flood risk. The development should contribute to flood alleviation schemes and re-
naturalisation to Wealdstone Brook. Planting should be reinforced along the brook.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage
Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that
surface water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood
zone 3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding
from Surface Water mapping or depth predicted for the site.
Set-back Distance
An 8m wide undeveloped buffer strip should be retained along main the Wealdstone Brook to provide access for maintenance. Finished Floor Levels
For residential development within the flood extent finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site.
33
Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to assess the flood frequency, depth, velocity and speed of onset.
34
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
35
Site Name: Argenta House & Wembley Point Site
Allocation
Ref.
BSSA6
Location: Argenta Way, NW10 0AZ Site Area
(ha):
1.2
Proposed Use: Residential and employment Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
100% 99% 72%
Peak flood level in a 1 in
20yr flood event (AOD)
Peak flood level in a 1 in 100yr flood event
(AOD)
Peak modelled flow in a 1 in 100yr flood event (cumecs)
26.27m 26.72m 122.20
Wembley Brook intersects the site. The brook is in a concrete channel which connects to the River Brent via a culvert River Brent and its
Main River 35% Climate Change Surface Water 1 in 30yr Surface Water 1 in 100yr (increase)
100% 36% 20%
Geology and Groundwater
Groundwater susceptibility 25%-50%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is in a Critical Drainage Area with
increased potential for elevated groundwater.
Other Sources
Sewer 87% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
39
Site Layout and Design
Development, other than water compatible uses, will not be acceptable within the functional flood plain (flood zone 3b). More vulnerable uses
should be restricted to areas of lowest flood risk and on upper floors. Ground floors should be designed to be resistant and resilient to flood risk.
Basement dwellings will not be acceptable on the site.
Through works to the Wembley Brook proposals should reduce flood risk overall and not increase the risk of flooding on adjoining sites. Flood
flow routes improved and not restricted. Proposals should seek to naturalise the Wembley Brook in accordance with the Thames River Basin
Management Plan and Brent River Corridor Improvement Plan.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of SuDS. SuDS should aim to
achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is managed as close to
the source as possible in accordance with the London Plan drainage hierarchy. The Wembley Brook is an opportunity for natural SuDS.
Permeable surfaces should be increased, planting and open space maximised to ensure space for water to flow during times of flood. Within
flood zone 3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding
from Surface Water mapping or depth predicted for the site.
Set-back Distance
An undeveloped buffer strip should be retained along main rivers to provide access for maintenance. Generally, this should be 8m wide, however, given the scale of the site the size of the buffer should be informed by detailed discussions with the Environment Agency.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm above the 1 in 100 flood level plus an appropriate allowance for climate change flood level. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
40
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
structural columns and stills should be circular design to avoid collection of debris during a flood event
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the development is 100 years. Emergency Planning
The site is in an EA flood warning area. Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to assess the flood frequency, depth, velocity and speed of onset.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
41
Site Name: Brook Avenue Site Allocation Ref. BCSA3
Location: Wembley, HA9 Site Area (ha): 1.5
Proposed Use: Residential Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
82% 68% 6%
Peak flood level in a 1 in 20yr
flood event (AOD)
Peak flood level in a 1 in 100yr flood
event (AOD)
Peak modelled flow in a 1 in 100yr flood event (cumecs)
31.95m 32.58m 31.80
The Wealdstone Brook runs in a culvert to the north west of the site and is a source of flooding. The south western corner of the site is in flood
zone 3a due to fluvial flooding, and the majority of the site is in flood zone 2. The low lying areas adjoining the river is functional floodplain.
The extent of flood zone 3a will extend to encompass additional properties as a result of climate change, as will the area of surface water
flooding.
Geology and Groundwater
Groundwater susceptibility <25%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is within a Critical Drainage Area.
Other Sources
Sewer 100% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. The rear of the site
has been subject to sewer flooding historically.
45
Site Layout and Design
More vulnerable uses should be restricted to upper floors and areas of lowest flood risk to the north. Lower vulnerability uses including
landscaped open space or gardens should be located in flood zone 3a. Encroachment into functional floodplain adjacent the site boundary will
not be permitted. Flow routes should not be obstructed.
A positive reduction in the risk of flooding must be demonstrated. It must be demonstrated that the proposed development does not result in an
increase in maximum flood levels, within adjoining properties.
The development should contribute to flood alleviation and re-naturalisation to Wealdstone Brook.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage
Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface
water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone
3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from
Surface Water mapping or depth predicted for the site.
Set-back Distance
An 8m wide undeveloped buffer strip should be retained along main rivers to provide access for maintenance. Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
46
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning The majority of the site is in an EA flood warning area, with the exception of numbers 24 to 28. Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to assess the flood frequency, depth, velocity and speed of onset.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
47
Site Name: College of North West
London Wembley
Site Allocation Ref. BCSA11
Location: Wembley, HA9 Site Area (ha): 0.37
Proposed Use: Mixed-use Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
79% 17% 16%
Peak flood level in a 1 in 20yr
flood event (AOD)
Peak flood level in a 1 in 100yr flood event
(AOD)
Peak modelled flow in a 1 in 100yr flood event (cumecs)
31.95m 32.58m 31.80
The Wealdstone Brook runs in a culvert to the north of the site and is a source of flooding. The majority of the site is in flood zone 2. The low lying
areas adjoining the river is functional floodplain.
The extent of flood zone 3a will extend to encompass additional properties as a result of climate change, as will the area of surface water flooding.
Geology and Groundwater
Groundwater susceptibility <25%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it. However,
because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment Agency identify
the susceptibility of ground water flooding in this location as between 25 and 50%. The site has increased potential for elevated groundwater.
Other Sources
Sewer 21% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes,
causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding occurs.
Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. There are no records of historic sewer flooding
on the site.
51
Site Layout and Design
More vulnerable uses should be restricted to upper floors and areas of lowest flood risk to the west. Lower vulnerability uses including landscaped
open space or gardens should be located in flood zone 3a. Encroachment into functional floodplain adjacent the site boundary will not be permitted.
Flow routes should not be obstructed.
A positive reduction in the risk of flooding must be demonstrated. It must be demonstrated that the proposed development does not result in an
increase in maximum flood levels, within adjoining properties.
The development should contribute to flood alleviation and re-naturalisation to Wealdstone Brook.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS).
SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is
managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a
(surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface
Water mapping or depth predicted for the site.
Set-back Distance
An 8m wide undeveloped buffer strip should be retained along main rivers to provide access for maintenance. Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
52
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
The majority of the site is in an EA flood warning area. Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Developments will be required to sign up to the Environment Agency flood warning system. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by modelling to assess the flood frequency, depth, velocity and speed of onset.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
53
Site Name: Stadium Retail Park
& Fountain Studios
Site
Allocation
Ref.
BCSA2
Location: Wembley Park
Drive, HA9 8TS
Site Area
(ha):
1.67
Proposed Use: Residential and
commercial
Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
49% 0 0
The Wealdstone Brook runs 50 metres to the north of the site and is a source of fluvial flooding. The east of the site is within flood zone 2.
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is in a Critical Drainage Area and the
north eastern corner of the site has increased potential for elevated groundwater.
Other Sources
Sewer 77% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes,
causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding
occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
Site Layout and Design
More vulnerable uses should be restricted to areas of lowest flood risk to the south west of the site. Lower vulnerability uses including landscaping
open space should be located to the east of the site.
57
A positive reduction in the risk of flooding must be demonstrated as part of any development. It must be demonstrated that proposed development
does not result in an increase in maximum flood levels, within adjoining properties.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS).
SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is
managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a
(surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface
Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
The east of the site is in an EA flood warning area. Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the development is 100 years.
58
Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2) of the Exception Test subject to submission of a detailed site specific FRA.
59
SFRA Level 2 required due to surface water
Site Name: Turpin’s Yard Site Allocation Ref. BSESA31
Location: Oakland Road, NW2
6LL
Site Area (ha): 0.4
Proposed Use: Residential and
employment
Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 25%
Surface water ponding is predicted on hard standing in the centre of the site during the 1 in 30-year pluvial event or greater. An overland flow
path is observed along the surrounding road network. Surface water flooding occurs as a result of high intensity rainfall when water is ponding
or flowing over the ground surface before it enters the underground drainage network or a watercourse. The majority of the ground coverage in
the site is impermeable car parking or storage. This area is subject to ponding.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 900mm on the site during the 1% annual
Surface water flooding will increase as a result of climate change.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 87% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. Thames Water hold
no records of incidents of sewer flooding on this site.
Site Layout and Design
More vulnerable uses such as residential development should be avoided in areas identified to be at risk of surface water flooding; instead
lower vulnerability uses including landscaped open space should be located here.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated
that the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
62
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage
Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface
water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone
3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from
Surface Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the development is 100 years.
63
Emergency Planning Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The FRA should be informed by EA data on flood depth, speed and direction. Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed site specific FRA.
64
Site Name: Park Avenue Garage Site Allocation Ref. BCSA25
Location: St Paul’s Avenue, NW2 5TG Site Area (ha): 0.23
Proposed Use: Residential Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 25%
Surface water ponding is predicted on the western boundary and eastern corner of the site during the 1 in 30-year pluvial event or greater. An
overland flow path is observed along the surrounding road network The majority of the ground coverage in the site is impermeable as it is
heavily urbanised. This can compound surface water flooding as the runoff rate is greater on impermeable grounds compared to permeable
areas.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 1200mm on the site during the 1% annual
Climate change is likely to result in a slight increase in surface water flooding on the site.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 54% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. Thames Water hold
no records of incidents of sewer flooding on this site.
Site Layout and Design
Residential development should be avoided in areas identified to be at risk of surface water flooding; instead lower vulnerability uses including
landscaped open space should be located here.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated
that the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
67
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage
Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface
water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone
3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from
Surface Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years.
68
Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the
risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency
evacuation procedures in the design and layout of the proposed development.
Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction. Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
69
Site Name: Hereford & Exeter Court Site Allocation Ref. BSESA8
Location: 1-124 Hereford House & 1-
32 Exeter Court Carlton Vale
Site Area (ha): 0.8
Proposed Use: Residential and open space Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 36%
Surface water ponding is predicted on around the building footprint on impermeable surfaces such as car parking and the highway during the 1
in 30-year pluvial event or greater. The majority of the ground coverage in the site is impermeable as it is heavily urbanised. This can
compound surface water flooding as the runoff rate is greater on impermeable grounds compared to permeable areas. In addition, less water is
able to drain away through infiltration, which increases the surface water flood risk in these areas.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 900mm on the site during the 1% annual
Climate change will increase surface water flooding on this site.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 86% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water
levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage
inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks
where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. Thames Water
have recorded instances of sewer flooding on the site.
Site Layout and Design
Lower vulnerability uses including landscaped open space should be directed to areas at risk of surface water flooding.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated
that the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
72
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The
drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage
Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface
water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone
3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from
Surface Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years.
73
Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction. Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
74
Site Name: Neasden Station Growth
Area 1
Site Allocation Ref. BEGA1
Location: Neasden Lane NW10 2UJ Site Area (ha): 0.73
Proposed Use: Residential and employment Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 74%
Surface water ponding is predicted on large impermeable surface used as yard space during the 1 in 30-year pluvial event or greater. Exceptions
include areas of tree planting. This can compound surface water flooding as the runoff rate is greater on impermeable grounds compared to
permeable areas. In addition, less water is able to drain away through infiltration, which increases the surface water flood risk in these areas. An
overland flow path is observed along the railway line to the north.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 900mm on the site during the 1% annual
Surface water flooding will increase as a result of climate change.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 92% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection
holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where
flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
Site Layout and Design
The site is proposed for mixed-use development. More vulnerable uses should be located on upper floors and less vulnerable uses at ground
floor. Open space and soft landscaping should be increased.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems
77
(SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water
runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone
3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from
Surface Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the
risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency
evacuation procedures in the design and layout of the proposed development.
78
Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the
Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
79
Site Name: Neasden Station Growth
Area 2
Site Allocation Ref. BEGA1
Location: Neasden Lane, NW10
2UG
Site Area (ha): 1.73
Proposed Use: Residential and
employment
Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 52%
Surface water ponding is predicted on large expanses of imperable surface used as yard space during the 1 in 30-year pluvial event or greater.
This can compound surface water flooding as the runoff rate is greater on impermeable grounds compared to permeable areas. In addition, less
water is able to drain away through infiltration, which increases the surface water flood risk in these areas. An overland flow path is observed
along the railway line to the north.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 1200mm on the site during the 1% annual
Climate change will increase surface water flooding on the site.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 62% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes,
causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding
occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
Site Layout and Design
Mixed-use development is proposed on the site. More vulnerable uses should be located on upper floors and less vulnerable, such as
employment space, on ground floors. Open space and soft landscaping should be directed to areas of flood risk.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS).
82
SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is
managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a
(surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface
Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development.
83
Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the
Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
84
Site Name: Neasden Station Growth Area
3
Site Allocation Ref. BEGA1
Location: Neasden Lane, NW10 2UE Site Area (ha): 0.28
Proposed Use: Residential and employment Vulnerability Classification: More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 58%
Surface water ponding is predicted on hard standing in the south west of the site during the 1 in 30-year pluvial event or greater. An overland flow
path is observed along the surrounding road network. The majority of the site comprises impermeable surfaces with the exception of an area of
landscaping to the south. The adjacent railway lines can be a source of run off. This can compound surface water flooding as the runoff rate is
greater on impermeable grounds compared to permeable areas. In addition, less water is able to drain away through infiltration, which increases
the surface water flood risk in these areas.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 1200mm on the site during the 1% annual
Climate change will result in a significant increase in surface water flooding on the site.
Geology and Groundwater
Groundwater susceptibility 0
Other Sources
Sewer 100% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes,
causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding
occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough.
Site Layout and Design
More vulnerable uses should be located on upper floors and less vulnerable uses at ground floor. Open space and soft landscaping should be
located on areas of flood risk.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
87
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS).
SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is
managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a
(surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface
Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the property is 100 years. Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development.
88
Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
89
Site Name: 438-444 Neasden
Lane & 1-24 Pit
House
Site
Allocation
Ref.
N/A intensification corridor
Location: Press Road, NW10
0DA
Site Area
(ha):
0.45
Proposed Use: Residential and
commercial
Vulnerability
Classification:
More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
0 0 0
Surface water flooding
Flood zone 3a 46%
Surface water ponding is predicted on land surrounding the buildings to the south of the site during the 1 in 30-year pluvial event or greater. An
overland flow path is observed along the surrounding road network. Surface water flooding occurs as a result of high intensity rainfall when water
is ponding or flowing over the ground surface before it enters the underground drainage network or a watercourse. Although the land surrounding
the properties is predominantly landscaped, the surrounding road network can compound surface water flooding as the runoff rate is greater on
impermeable grounds compared to permeable areas. In addition, less water is able to drain away through infiltration, which increases the surface
water flood risk in these areas.
The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 300mm on the site during the 1% annual
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy
clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it.
However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment
Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is in a Critical Drainage Area.
Other Sources
Sewer 100% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which
exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels,
water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes,
causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding
occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. They hold no records of historic
sewer flooding instances within this site as of 2017.
92
Site Layout and Design
More vulnerable uses should be located on upper floors and less vulnerable uses at ground floor. Open space and soft landscaping should be
located on areas of flood risk.
A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that
the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
Surface Water
A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage
strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS).
SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is
managed as close to the source as possible in accordance with the London Plan drainage hierarchy.
Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a
(surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface
Water mapping or depth predicted for the site.
Finished Floor Levels
If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 300mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures
A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level
installing flood doors and barriers, to ensure water stays out of a property to a given height
providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
93
Access/Egress
Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the
lifetime of the development is 100 years.
Emergency Planning
Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation
It is recommended that potential developers contact Brent Council as the LLFA for further information prior to taking forward site specific plans. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2) of the Exception Test subject to submission of a detailed site specific FRA.
94
Site Name: Queensbury LSIS and Morrisons
Site Allocation Ref. BNSA3
Location: Honey Pot Lane, NW9 Site Area (ha): 8.24
Proposed Use: Residential and commercial Vulnerability Classification: More vulnerable
Fluvial flooding
Flood zone 2 Flood zone 3a Flood zone 3b
15% 0 0
The Wealdstone Brook runs through the south of the site in a culvert and is a source of flooding. The majority of the site has a low probability of fluvial flooding. However, low lying areas adjoining the Wealdstone Brook are at risk of flooding and within flood zone 2.
95
96
Surface water flooding
Flood zone 3a 14%
Surface water ponding is predicted on the highway during the 1 in 30-year pluvial event or greater. An overland flow path is observed along the surrounding road network. The majority of the ground coverage in the site is impermeable, comprising a large expanse of car parking and industrial units. This can compound surface water flooding as the runoff rate is greater on impermeable grounds compared to permeable areas. In addition, less water is able to drain away through infiltration, which increases the surface water flood risk in these areas. The Environment Agency’s surface water depth modelling identifies the potential for depths of 0 - 900mm on the site during the 1% annual chance.
Main River 35% Climate Change Surface Water 1 in 30yr Surface Water 1 in 100yr (increase)
0 14% 7%
Geology and Groundwater
Groundwater susceptibility <25%
The site is underlain by Thames Group (also referred to as London Clay) bedrock, a composition of silty clay/mudstone, sandy silts and sandy clayey silts of marine origin. Thames Group generally has a low hydraulic conductivity which means water does not easily move through it. However, because of this characteristic and poor drainage, ponding can occur if London Clay is downhill of aquifer outcrops. The Environment Agency identify the susceptibility of ground water flooding in this location as between 25 and 50%. The site is within a Critical Drainage Area.
Other Sources
Sewer 74% site
Reservoir 0
Canal 0
Sewer flooding can occur due to sewer infrastructure failure or due to an increased flow and volume of water entering a sewer system which exceeds its hydraulic capacity, causing the system to surcharge. If sewer outfall points are either blocked or submerged due to high water levels, water can back up in a sewer system and cause flooding. These issues can result in water overflowing from gullies and drainage inspection holes, causing flooding in the local area. The south of the borough has a combined sewer, leading to increased environmental risks where flooding occurs. Thames Water Utilities Ltd provide surface water, foul and combined sewer systems in the borough. Thames Water have recorded incidents of sewer flooding in the south western corner of the site.
Site Layout and Design Vulnerable uses should be restricted to areas of lowest flood risk. Residential development should be avoided to the south defined as Flood Zone 2, and in areas identified to be at risk of surface water flooding; instead lower vulnerability uses including landscaped open space should be located here. Overland flow paths should not be obstructed. Subject to the recommendations of the Site Specific FRA, development should seek to deculvert and naturalise the Wealdstone Brook. A positive reduction in the risk of flooding must be demonstrated and flood flow routes improved and not restricted. It must be demonstrated that the proposed development does not result in an increase in maximum flood levels, within adjoining properties.
98
Surface Water A drainage strategy will be required which accords with the Drainage Strategy Submission Checklist included in the Level 1 SFRA. The drainage strategy for the site must be considered early in the site planning process to ensure adequate inclusion of Sustainable Drainage Systems (SuDS). SuDS should aim to achieve greenfield run off rates, providing management and attenuation features that ensure that surface water runoff is managed as close to the source as possible in accordance with the London Plan drainage hierarchy. Permeable surfaces should be increased, and open space maximised to ensure space for water to flow during times of flood. Within flood zone 3a (surface water), flood plain compensation must account for predicted flood depths for the 1 in 30yr and 1 in 100yr Risk of Flooding from Surface Water mapping or depth predicted for the site. Set-back Distance An 8m wide undeveloped buffer strip should be retained along the Wealdstone Brook to provide access for maintenance. The EA should be contacted to obtain an Environmental Permit for main rivers, further information can be found on their website: www.gov.uk/guidance/flood-risk-activities-environmental-permits Finished Floor Levels If residential development cannot be avoided within the flood extent, finished floor levels should be set at least 600mm freeboard above the 1 in 100 flood level plus an appropriate allowance for climate change. Internal access to higher floors is required. It important to consider the implications of diverting the water on the flood risk of the rest of the site. Resilience and Resistant Measures A number of flood resistance and resilience measures can also be implemented into new developments to mitigate potential flooding. These could include:
installing electrical equipment above flood level installing flood doors and barriers, to ensure water stays out of a property to a given height providing adequate flood risk management infrastructure. Space should be left in developments for flood risk management infrastructure to be maintained and enhanced.
99
Access/Egress Safe dry access to and from the site should be provided for the lifetime of the property, factoring in the impacts of climate change. In this case the lifetime of the development is 100 years. Emergency Planning The south of the site is within a flood alert area. Details will be required on the flood related risks that will remain once the proposed mitigation measures have been implemented, and how the risks will be managed over the development’s lifetime. Flood warnings and/ or flood alerts need to be considered along with the emergency evacuation procedures in the design and layout of the proposed development. Details will be required on flood warning and emergency evacuation procedures as well as details regarding safe refuge areas above ground floor if dry egress routes for evacuation cannot be guaranteed. This should consider the safety of people within the building and also the safety of people around the building and in adjacent areas, including those who are less mobile. LLFA Consultation It is recommended that potential developers contact the Environment Agency and Brent Council as the LLFA for further information prior to taking forward site specific plans. A Site Specific FRA will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The FRA should be informed by modelling to assess the flood extent, depth and speed. Site Specific FRA A Site Specific Flood Risk Assessment will be required which meets the requirements of the Flood Risk Assessment Submission Checklist in the Level 1 SFRA. The Site Specific FRA should be informed by EA data on flood depth, speed and direction.
Summary
Based on the strategic assessment of flood risk and the recommendations for mitigation measures set out above, it is considered that proposed development on this site could be suitably designed to satisfy part 2 of the Exception Test subject to submission of a detailed Site Specific FRA.
100
Appendix A – Screening Assessment Site Allocations P
olic
y N
o.
Site
Nam
e
Pro
po
sed
Use
Vu
lne
rab
ility
Cla
ssif
icat
ion
Site
Are
a (s
qm
)
FZ2
(%
of
site
are
a)
FZ3
a (F
luvi
al &
Tid
al -
% o
f si
te
are
a)
FZ3
b (
Flu
vial
& T
idal
- %
of
site
are
a)
Mai
n R
ive
r 3
5%
CC
(%
of
site
are
a)
FZ3
a (S
urf
ace
Wat
er -
% o
f si
te
are
a)
1 in
30
yr R
oFS
W E
xten
t (%
of
site
ar
ea)
Surf
ace
Wat
er F
loo
d R
isk
Incr
eas
e d
ue
to
Clim
ate
Ch
ange
Gro
un
dw
ate
r Su
sce
pti
bili
ty
Ban
din
g
Sew
er
Flo
od
ing?
Re
serv
oir
Flo
od
ing?
Seq
ue
nti
al T
est
Re
qu
ire
d?
Exce
pti
on
Te
st R
eq
uir
ed
?
Leve
l 2 S
FRA
Rec
om
me
nd
ed?
BCSA1 The Torch/ Kwikfit Mixed-use
More vulnerable 3823
< 25% 100% No No No
BCSA1 ASDA Wembley Mixed-use More vulnerable 30794 6% 6% 2%
