Wembley Area Action Plan WAAP... · Area Action Plan. 5.3 Similarly, the source of reasonably available alternative sites for comparison includes any sites within the Wembley Growth

Wembley Area Action Plan: Flood Risk Analysis for Site Proposals

Including sequential and exception tests

December 2012


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Contents

Page

1. Purpose 3

2. Policy context 3

3. Brent’s Strategic Flood Risk Assessment 4

4. Brent’s Surface Water Management Plan 4

5. Area for Applying the Test 5

6. Findings 6

7. Changes to Wembley Area Action Plan 7

Appendices

A. Sequential Test 14

B. Site-specific Analysis 18

C. Brent’s Strategic Flood Risk Assessment (2007)

Extract - planning recommendations

34


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1. Purpose

1.1 The National Planning Policy Framework (NPPF) requires Local Plans to apply a sequential, risk-

based approach to the locations of development in order to avoid flood risk. This document

fulfils these requirements by undertaking a sequential and, where appropriate, an exception test

for site proposals in the Wembley Area Action Plan. It also incorporates policy

recommendations in Brent’s Strategic Flood Risk Assessment Level 1 (2007), Wembley

Masterplan Level 2 Strategic Flood Risk Assessment (2008) and the Surface Water Management

Plan (2011).

1.2 All forms of flood risk are considered including:

• Fluvial – flooding from Wealdstone Brook

• Surface water flooding

• Ground water flooding

1.3 This document proposes changes and additions to the Wembley Area Action Plan in light of the

flood risk analysis and policy recommendations.

2. Policy Context

2.1 The National Planning Policy Framework (NPPF) (March 2012) requires Local Plans to apply a

sequential, risk-based approach to the locations of development in order to avoid flood risk. The

aim of the Sequential Test is to steer new development to areas with the lowest probability of

flooding. Development should not be allocated or permitted if there are reasonably available

sites appropriate for the proposed development in areas with a lower probability of flooding.

Where new development is exceptionally necessary in such areas, policy aims to make it safe

without increasing flood risk elsewhere and where possible, reducing flood risk overall.

2.2 Brent’s Strategic Flood Risk Assessment (SFRA) level 1 acknowledges that in areas like the

London Borough of Brent, restricting ‘more vulnerable’ development from areas designated as

Zone 3a (high probability of flooding) may heavily compromise the viability of existing

communities within the Borough. Where a local planning authority has identified that there is a

strong planning based argument for a development to proceed that does not meet the

requirements of the Sequential Test, it will be necessary for the Council to demonstrate that the

Exception Test can be satisfied. This document provides the analysis for the Sequential and

Exception Tests using the methodology and guidance set out in the NPPF Technical Guidance

(March 2012).

2.3 For the Exception Test to be passed:

• it must be demonstrated that the development provides wider sustainability benefits to the

community that outweigh flood risk, informed by a Strategic Flood Risk Assessment where

one has been prepared; and

• a site-specific flood risk assessment must demonstrate that the development will be safe for

its lifetime taking account of the vulnerability of its users, without increasing flood risk

elsewhere, and, where possible, will reduce flood risk overall.


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3. Brent’s Strategic Flood Risk Assessment

3.1 Brent’s Strategic Flood Risk Assessment (SRFA) Level 1 (2007) provides a spatial overview of the

risks posed by flooding (from various sources) across the borough. The SFRA should be used by

the Council to inform the application of the Sequential Test. A Level 2 SFRA (2008) has been

prepared for the Wembley Masterplan Area which assesses flood risk on the sites in more detail.

3.2 When considering the suitability of sites for future development, the SFRA (2007) states:

It is considered unreasonable to restrict future development within areas that may have

suffered a localised flooding incident in years past. It is essential however not to overlook the

potential risk of localised flooding during the design process. Whilst the incidents that have

been identified will typically not result in widespread damage or disruption, a proactive

approach to risk reduction through design can mitigate the potential for damage, both to the

development itself and elsewhere. Specific development control recommendations have been

provided accordingly.

3.3 The SFRA provides an assessment of flood risk in Wembley. It says:

Wembley is situated to the West of the Borough bordering the River Brent in the South and

Wealdstone Brook to the East.

A number of properties in the area are in the Flood Risk Zone 3a, High Probability of River

Brent and Wealdstone Brook. There are some areas falling within Zone 2, Medium

Probability.

The majority of the Wembley Area belongs to Zone 1, Low Probability.

Even though the flood outline is relatively narrow, the number of properties affected by a

Zone 3a and 2 event could be high as the area is densely developed. The area near the

confluence of the Wealdstone Brook and River Brent near Tokyngton has been identified as a

problem area for combined sewer flooding.

Overview of Development Pressure

Wembley is a major city centre and Opportunity Area of the Borough for regeneration which

enjoy good transport links. High density residential developments are encouraged in the

Town Centre to promote regeneration objectives. Key development centres are in the

Wembley Park/Stadium area east of the town centre. As a major visitor centre and venue for

national and international sports events, the area is under tremendous pressure for

development.

4. Brent’s Surface Water Management Plan

4.1 Brent’s Surface Water Management Plan outlines the preferred surface water management

strategy for the London Borough of Brent and includes consideration of flooding from sewers,

drains, groundwater and runoff from land, small watercourses and ditches that occurs as a result

of heavy rainfall.

4.2 The Plan identifies Critical Drainage Areas (CDA) where multiple sources of flood risk (surface

water, groundwater, sewer, river) cause flooding in one or more Local Flood Risk Zones (LFRZ). A


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LFRZ is defined as a discrete area of flooding that does not exceed the national criteria for a

‘Flood Risk Area’ but still affects houses, businesses or infrastructure.

4.3 In Wembley, the areas particularly susceptible to overland flow are formed by the river valleys of

the Wealdstone Brook and River Brent. Several stretches of the main line (Wembley Stadium),

are susceptible to surface water flooding and, if flooded, will impact services into and out of

London.

4.4 Most of the WAAP site proposals are within the Wembley Stadium Critical Drainage Area which

several areas of surface water ponding within the CDA affecting commercial property and critical

infrastructure. Critical Infrastructure affected- 2 x Electrical Installation. Sites W3, W4 and W6

are within a LFRZ.

4.5 Wembley is not an area where surface water flooding is likely to be caused by pluvial, sewer and

groundwater flooding.

4.6 The SWMP sets out recommendations for borough wide planning policies with the aim of

reducing surface water runoff. The Wembley Area Action Plan section of this document shows

how these recommendations have been incorporated.

4.7 From 2013 all new developments will be required to submit information to Brent’s SUDS

Approval Board (SAB) which has a duty to ensure that all new developments have incorporated

SUDS to deal with the surface water run off from the development.

5. Area for Applying the Test

5.1 This document applies the sequential test to each site proposal in the Wembley Area Action Plan

that falls within Flood Zones 2 and 3 and, where necessary, the exception test.

5.2 The geographical area of search over which the sequential test will be applied is restricted to the

Wembley Growth Area, defined in Core Strategy policy CP7, and taken forward by the Wembley

Area Action Plan.

5.3 Similarly, the source of reasonably available alternative sites for comparison includes any sites

within the Wembley Growth Area that are known to the council and that are available and

suitable for delivering growth. Specifically, these are sites W1-W31 in the Wembley Area Action

Plan. Some sites are not appropriate for certain uses; for example residential use in the

Strategic Industrial Location (sites W29-31) or retail outside the town centre (sites W14-W19

and W25-W31). When comparing sites, only those capable of accommodating the same use

class(es) will be considered ‘available’.

5.4 The reason for limiting the geographical area of search for the sequential test and the source of

alternative sites to the Growth Area is because Wembley is designated as an Opportunity Area in

the London Plan with targets for growth including 11,000 new jobs and 11,500 new homes.

London Plan Policy 2.13 requires the borough to develop detailed proposals for the Wembley

Opportunity Area in order to deliver these strategic targets.

5.5 London Plan Table A1.1 Opportunity Areas sets out the following policy direction for Wembley:

New housing and leisure-related development should be integrated with the iconic and

world-class stadium and other facilities, including the Arena and Conference Centre.


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Supported by upgrades to the three stations, improved public transport will play a key role in

managing heavy demand for mass movement, links between the stations and the strategic

leisure facilities should be improved. Development should contribute to the regeneration,

vitality and viability of Wembley as a town centre, including its expansion eastwards.

Proposals should enhance permeability and connectivity to the wider hinterland and the

potential to locate a civic facility including a school adjacent to Olympic Way should be

explored.

5.6 In order to deliver this growth in Wembley all available suitable sites must be considered. It is

not appropriate to consider sites outside of Wembley Growth Area for comparison because they

do not form part of the Growth Area and cannot contribute to meeting the identified growth.

5.7 The source used for comparing flood risk between sites is the council’s Site Specific Allocations

PPS25 Sequential Test (June 2010), Strategic Flood Risk Assessment Level 2: Wembley

Masterplan Area (November 2008) and associated map.

6. Findings

6.1 The council has a proactive approach to risk reduction when considering the suitability of sites

for future development in the Wembley Area Action Plan, in line with the recommendations of

the SFRA.

6.2 The table in Appendix A compares each of the Wembley Area Action Plan proposals sites (W1-

W31) with any reasonably available sites in the Wembley Growth Area with a lower probability

of flooding that would be appropriate to the type of land use proposed.

6.3 The analysis shows that the majority of available sites in the Wembley Area Action Plan are in

Flood Zone 1 where all development uses are permitted and therefore the sequential test is not

necessary. For all sites however, it is essential that sustainable drainage techniques are

stipulated as a development control recommendation to reduce the runoff from the site,

thereby not exacerbating existing localised drainage problems nearby. This is a key

recommendation of the Level 1 SFRA (section 6.4.8).

6.4 Detailed analysis was carried out on the remaining eight sites which fall partly or wholly into

flood zones 2 and 3 shown at Appendix B.

6.5 Three of the sites (W13, W15, W27) are in flood zones 1 and 2. The analysis found that there are

no reasonably available alternative sites wholly in Flood Zone 1, but there is low flood risk

vulnerability as the proposed uses are compatible with flood zones 1 and 2.

6.6 Four of the sites (W14, W16, W21, W26) are in flood zones 1-3. The analysis found that there

are no reasonably available alternative sites in zones 1 and 2. More vulnerable uses such as

residential, residential care homes, certain community facilities, education, student

accommodation and hotels require an Exception Test in flood zone 3a. None of the proposed

uses are compatible with flood zone 3b. An Exception Test was carried out for each of these

sites and included in the site specific analysis below.

6.7 One site (W25) is in flood zones 2-3. The analysis found that there are no reasonably available

alternative sites in zones 1 and 2. More vulnerable uses such as residential, residential care

homes, certain community facilities, education, student accommodation and hotels require an

Exception Test in flood zone 3a. None of the proposed uses are compatible with flood zone 3b.


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An Exception Test was carried out for each of these sites and included in the site specific analysis

below.

6.8 Sites W3, W4 and W6 are in a Local Flood Risk Zone (LFRZ) in the Wembley Stadium Critical

Drainage Area (CDA) which has several areas of surface water flooding affecting property and

critical infrastructure. The SWMP identifies preferred options for mitigating flood risk in the

LFRZ which include Road side Rain Garden, Detention basins and Land Management practices.

There may be opportunities to alleviate surface water flooding as part of the development of

this site.

7. Changes to Wembley Area Action Plan

7.1 This section sets out additions and changes to the draft Wembley Area Action Plan in light of the

findings from the NPPF sequential and exception tests, Brent’s Strategic Flood Risk Assessment

Level 1 (2007), Wembley Masterplan Level 2 Strategic Flood Risk Assessment (2008) and the

Surface Water Management Plan (2011).

Proposed changes to Policy WEM35

7.2 In line with para 100 of the National Planning Policy Framework (NPPF) and in order to improve

the strategic approach to flood risk in policy WEM35, the following changes are suggested:

WEM35: Flood Risk

All proposed development in Flood Zones 2 and 3 will require a detailed Flood Risk Assessment

(FRA), in accordance with Section 6.7 of Brent’s Strategic Flood Risk Assessment.

Applications will be assessed against the site-specific flood risk mitigation requirements set out

for individual Site Proposals.

Development is not suitable in Flood Zone 3b.

Application of a site-level sequential approach will be expected to locate development towards

areas of lowest risk within the site. More vulnerable development will not usually be

appropriate in Flood Zone 3a. Where it is proposed in exceptional circumstances, an Exception

Test will be required.

Proposals within Flood Risk Zones 3a (High Probability and Climate Change) and 2 (Medium

Probability) will be required to pass the Sequential Test, and where a site is affected by Flood

Zone 3a, the Exception Test must be applied. Proposals will need to demonstrate how flood risk

is reduced by sequential layout of the site and form of development. All proposals for

development in Flood Zones 2 and 3a&b will require a full Flood Risk Assessment (FRA).

Proposals in Flood Zone 1 which are over 1 hectare in size will also require a site specific FRA.

Development proposals in the area above must demonstrate that there will be no net loss in

floodplain storage nor an increase in maximum flood levels, within adjoining properties as

recommended by Brent's Strategic Flood Risk Assessment Report Level 1 (2007).

Developments will be required to implement SUDS to ensure that runoff from the site (post

redevelopment) does not exceed Greenfield runoff rates.

In order to reduce surface water flood risk in the area, all major proposals will be required to

apply SUDS in accordance with Brent Surface Water Management Plan.


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Developers will also be required to demonstrate whether there is sufficient capacity both on and

off site in the foul sewer network to support development. Where insufficient capacity exists

developers will be required to identify how any necessary upgrades will be delivered ahead of

the occupation of development.

Proposed changes to Chapter 10: Response to climate change

7.3 The SWMP sets out recommendations for borough wide planning policies with the aim of

reducing surface water runoff. The table below shows how the policy requirements have been

incorporated into the Wembley Area Action Plan, where appropriate.

SWMP Policy Requirement Wembley Area Action Plan

Wembley Central Critical Drainage Area Para 10.13 –

In most of the urban area, roads and land are

usually impermeable which can lead to surface

water flooding. Much of Wembley is prone to

surface water flooding. The Flood and Water

Management Act 2010 requires local

authorities across England and Wales to

develop, maintain, apply and monitor a

strategy for local flood risk management in

their areas. Brent Surface Water Management

Plan (BSWMP), which contains the

Preliminary Flood Risk Assessment and a Flood

Risk Management Plan, designates the

Wembley Stadium Critical Drainage Area (CDA)

which has several areas of surface water

flooding affecting property and critical

infrastructure. The SWMP identifies mitigation

measures which aims to help manage and

reduce surface water flood risk in Brent.

Wembley Stadium CDA Action - Encourage

uptake of green roofs in new developments.

WEM34

Wembley Stadium CDA Action – Encourage

permeable paving

WEM35

Wembley Stadium CDA Action - Identify

potential locations suitable for retrofitting

Road Side Rain Gardens, and where swales

and detention basins could be installed

Add text to 10.14:

Measures to alleviate surface water flooding

through SUDS will be required as part of the

development of sites W3-W4, W6-W20 and

W25-W29.

Ponds should be included as part of a wider

SuDS scheme for the redevelopment of this

area

Add “ponds” to para 10.14

Undertake further topographical survey to

determine the extent to which kerbs could

be altered

Add “re-profiling of ground levels” to para

10.14

Undertake further topographical survey to

determine the extent to which ground levels

could be changed

Add “re-profiling of ground levels” to para

10.14


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A specific river corridor management policy

to provide flood defence, recreation,

amenity and biodiversity

WEM42

Development must achieve surface water

runoff at or below present greenfield runoff

rates

Add to policy WEM35

Development must be safe from flooding

over its whole lifetime, including for the

impacts of climate change, and should use

all opportunities to reduce flood risk overall

Add new para to supporting text:

10.16 Specific flood risk reduction measures

and Flood Risk Assessment requirements are

set out for each site proposal (chapters 12-16).

This includes recommendations from the SFRA,

SWMP and site-specific sequential

considerations. From 2013 all new

developments will be required to submit

information to Brent’s SUDS Approval Board

(SAB) which has a duty to ensure that all new

developments have incorporated SUDS to deal

with the surface water run off from the

development.

Add flood mitigation/ FRA recommendations

for each site proposal (chapters 12-16 – see

section 7.5 below).

Green Infrastructure within development

should protect existing floodplains and

provide an opportunity for linking habitats

and creating environmental highways

through the integration of SuDS through

urban areas

See above

SuDS should be used to control the rate and

volume of runoff. Pollution controls should

be incorporated within them to protect and

improve watercourse quality

See above

All developments exceeding 0.5 hectares

must include source control and/or natural

surface water storage options within the site

boundary; and design for greenfield run off

rates

See above

New developments should demonstrate that

during events that exceed the design

capacity of the surface water drainage

system excess water is safely stored or

conveyed from the site without adverse

impacts

See above

The long term management and

responsibility for the maintenance of any

new SuDS systems must be agreed with the

council (until such time as the SuDS Approval

Body is in place) prior to the granting of

planning permission

See above

All development pre commencement of See above


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construction must submit and be approved

by Brent Drainage Section (LLFA) detailed

drainage design including storage

calculations for the attenuated flows and

flow restriction methods

All new properties within a fluvial flood zone

or local flood risk zone should have a

finished floor level at least 0.3m above

surrounding ground levels and be fitted with

flood resilience measures up to 0.5m above

finished floor level. (However this will not

negate other planning requirements, for

example to achieve inclusive access to new

development)

See above

Guidelines on the provision of onsite storage

including the AEP event and necessary

freeboard

Technical information as part of Flood Risk

Management Plan

Guidelines on the need for strategic

mitigation measures, particularly in

identified regeneration areas, required to

contribute to managing surface water flood

risk on a wider scale

WEM35, development management policies

Guidance on what is classed as permitted

development within a CDA or policy area

and any deviation from national guidance via

local development orders for example

Include in borough-wide development

management policy

Load-reduction targets must be achieved

when assessing the post-developed sites

SuDS treatment train

Part of site assessment criteria

7.4 In light of policy requirements from the SWMP and elsewhere, the following changes are

proposed for WAAP paragraphs 10.11-10.15 as well as an additional paragraph inserted as

10.16:

Flooding

10.11 There are two types of floods in the area, one is associated with the river when the actual

amount of river flow is larger than the amount that the channel can hold, and river will overflow

its banks and flood the areas alongside the river. Land adjacent to the Wealdstone Brook is the

area at risk of flooding. The map shows the areas at risk of flooding. Brent seeks to ensure that

all new development in flood risk areas is appropriately flood resilient and resistant and that

any residual risk can be safely managed.

10.12 As required by the National Planning Framework, the council has undertaken a sequential

approach should be used in areas known to be for sites at risk from any form of flooding

including fluvial and surface water flooding. Planning recommendations are provided for sites

at risk of flooding in the Site Proposals chapters. Inappropriate The council has a proactive

approach to risk reduction when considering the suitability of sites for future development in

the Wembley Area Action Plan, in line with the recommendations of the SFRA. New

development in areas at risk of flooding will be required to apply a site-level sequential test to


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ensure should be avoided by directing development is steered away from areas at highest risk

and located in line with the NPPF flood risk vulnerability classification but where development is

necessary, making it safe without increasing flood risk elsewhere.

10.13 In most of the urban area, roads and land are usually impermeable which can lead to

surface water flooding. Much of Wembley is prone to surface water flooding. The Flood and

Water Management Act 2010 requires local authorities across England and Wales to develop,

maintain, apply and monitor a Brent’s Surface Water Management Plan (SWMP) provides a

strategy for local flood risk management in the borough. their areas. Brent Surface Water

Management Plan (BSWMP), which contains the Preliminary Flood Risk Assessment and a Flood

Risk Management Plan, The document identifies and designates a Critical Drainage Area (CDA)

for the Wembley Stadium area which has several areas of surface water flooding affecting

property and critical infrastructure. Three WAAP sites fall into a Local Flood Risk Zone (LFRZ).

aims to help manage and reduce surface water flood risk in Brent.

10.14 The Act also introduces the requirements for d Developers are required to construct

include sustainable urban drainage systems (SUDS) in their schemes. The SWMP identifies

specific SUDS measures for the Wembley Stadium CDA to relieve pressures on the drainage

system, reduce flood risk and the demand for fresh water. These include rainwater harvesting

and grey water recycling, can help relieve pressures on the drainage system, It can reduce flood

risk and the demand for fresh water. SUDS such as green roofs, filter strips and swales, storm

water storage tanks, permeable and porous pavements, re-profiling of ground levels, basins,

ponds, reed beds can help reduce the volume and speed of water flowing into drains and

eliminate surface water flooding. BSWMP favours the application of SUDS. Measures to

alleviate surface water flooding through SUDS will be required as part of the development of

sites W3-W4, W6-W20 and W25-W29. Specific SUDS requirements for sites in the LFRZ are set

out in the appropriate Site Proposals.

10.15 In addition, Most of the sewer network in the Wembley area is undersized. Careful

consideration must be given to issues of sewer flooding, both on and off site, as a result of new

development. Developers may be required to carry out studies to ascertain whether proposed

development will lead to overloading of the existing sewer infrastructure.

10.16 Specific flood risk reduction measures and Flood Risk Assessment requirements are set

out for each site proposal (chapters 12-16). This includes recommendations from the SFRA,

SWMP and site-specific sequential considerations. From 2013 all new developments will be

required to submit information to Brent’s SUDS Approval Board (SAB) which has a duty to

ensure that all new developments have incorporated SUDS to deal with the surface water run

off from the development.

Proposed changes to Chapters 12-16: Site Proposals

7.5 Key recommendations should be incorporated for each site affected by flooding. It is suggested

the following additional paragraphs are added or replace the section on flooding for Site

Proposals (chapters 12-16):

W3

Site W3 is in a Local Flood Risk Zone (LFRZ) in the Wembley Stadium Critical Drainage Area (CDA)

which has several areas of surface water flooding affecting property and critical infrastructure.

Brent’s Surface Water Management Plan (SWMP) identifies mitigation measures for the LFRZ


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which include road side rain gardens, detention basins and re-profiling ground levels. Measures

to alleviate surface water flooding will be required as part of the development of this site.

W4

Part of Site W4 is in a Local Flood Risk Zone (LFRZ) in the Wembley Stadium Critical Drainage

Area (CDA) which has several areas of surface water flooding affecting property and critical

infrastructure. Brent’s Surface Water Management Plan (SWMP) identifies mitigation measures

for the LFRZ which include road side rain gardens, detention basins and re-profiling ground

levels. Measures to alleviate surface water flooding will be required as part of the development

of this site.

W6

Site W6 is in a Local Flood Risk Zone (LFRZ) in the Wembley Stadium Critical Drainage Area (CDA)

which has several areas of surface water flooding affecting property and critical infrastructure.

Brent’s Surface Water Management Plan (SWMP) identifies mitigation measures for the LFRZ

which include road side rain gardens, detention basins and re-profiling ground levels. Measures

to alleviate surface water flooding will be required as part of the development of this site.

W13

The site is in flood zones 1 and 2. All proposed development will require a detailed Flood Risk

Assessment (FRA), in accordance with Section 6.7 of the Brent Borough SFRA. The ‘sequential

approach’ at site level should be applied to steer more vulnerable development such as

residential, student accommodation, hotels, and certain community uses towards areas of

lowest risk within the site; north west area and southern edge. Density should be varied to

reduce the number of vulnerable units in high risk areas. Further site-specific details are set out

in the sequential test assessment for the WAAP.

W14

The site is in flood zones 1-3. All proposed development will require a detailed Flood Risk

Assessment (FRA), in accordance with Section 6.7 of the Brent Borough SFRA. While the council

considers that developing the site provides wider sustainability benefits to the community that

outweigh flood risk, a ‘sequential approach’ at site level should be applied to steer more

vulnerable development such as education, student accommodation and hotels uses towards

areas of lowest risk within the site; to the western area. None of the proposed uses are

compatible with flood zone 3b. Density should be varied to reduce the number of vulnerable

units in high risk areas. A minimum 8 metres buffer zone must be provided for the waterway

and development should contribute to the re-naturalisation of Wealdstone Brook. Further site-

specific details are set out in the sequential test assessment for the WAAP.

W15

The site is in flood zones 1 and 2. All proposed development will require a detailed Flood Risk

Assessment (FRA), in accordance with Section 6.7 of the Brent Borough SFRA. The ‘sequential

approach’ at site level should be applied to steer more vulnerable development such as

residential, and hotel uses towards areas of lowest risk within the site; area from north west to

south. Density should be varied to reduce the number of vulnerable units in high risk areas.

Further site-specific details are set out in the sequential test assessment for the WAAP.

W16





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vulnerable development towards areas of lowest risk within the site; to the north. None of the

proposed uses are compatible with flood zone 3b. Density should be varied to reduce the

number of vulnerable units in high risk areas. A minimum 8 metres buffer zone must be

provided for the waterway and development should contribute to the re-naturalisation of

Wealdstone Brook. Further site-specific details are set out in the sequential test assessment for

the WAAP.

W21




outweigh flood risk, a ‘sequential approach’ at site level should be applied to locate homes

towards area of lowest risk within the site; along Brook Avenue. The proposed use is not

compatible with flood zone 3b. Density should be varied to reduce the number of vulnerable

units in high risk areas. A minimum 8 metres buffer zone must be provided for the waterway

and development should contribute to the re-naturalisation of Wealdstone Brook. Further site-

specific details are set out in the sequential test assessment for the WAAP.

W25





vulnerable development such as residential uses towards areas of lowest risk within the site;

northern and southern areas. None of the proposed uses are compatible with flood zone 3b.

Density should be varied to reduce the number of vulnerable units in high risk areas. Further

site-specific details are set out in the sequential test assessment for the WAAP.

W26





vulnerable development such as residential, residential care homes, and certain community uses

towards areas of lowest risk within the site; western and southern areas. None of the proposed

uses are compatible with flood zone 3b. Density should be varied to reduce the number of

vulnerable units in high risk areas. Further site-specific details are set out in the sequential test

assessment for the WAAP.

W27

The majority of the site is in flood zone 1; however there are small sections of flood zone 2

adjacent to the Wealdstone Brook. The buffer strip will remove the developable area of the site

wholly into flood zone 1.


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Appendix A – Sequential Test

ID Name Type Existing use

Proposed / Potential use

Flood Zone

Known Surface / Ground Water Issues

Permissible Land Use (Sequential Test) Proposed Uses Compatible?

Site in FZ1?

Alternative site in FZ1?

Site in FZ 2?


Site in FZ3?

Alternative site in FZ3a?

Planning solution

Essential Infrastructure

Highly Vulnerable

More Vulnerable

Less Vulnerable

Water Compatible

W1 Wembley West End

Brownfield

Retail, residential and carpark

Mixed use - retail/residential /car park/bus lane

1 No ✓ yes Development in Zone 1 should consider the requirements of SFRA Section 6.4.8.

W2 London Road

Brownfield

Retail, office, takeaway, restaurant

Mixed use – retail, town centre uses


W3 Chiltern Line Cutting North

Brownfield

Railside embankments

Mix use retail, residential, office & open space

1 Yes LFRZ

✓ yes Development in Zone 1 should consider the requirements of SFRA Section 6.4.8. Mitigation requirements for LFRZ in SWMP.

W4 Wembley High Road/ Chiltern Line Cutting South

Brownfield Office

Mixed use - hotel & retail

1 Yes LFRZ


W5 Copland School & Brent House

Brownfield Office, petrol filling station & residential

Mixed use - residential/ office/retail


W6 South Way Site

Brownfield

Vacant Mixed use including retail, Pubs, bars, cafes, residential and student accommodation

1 Yes LFRZ


W7 Mahatma Gandhi House

Brownfield

Office Residential or office use


W8 Land West of Stadium

Brownfield

Under construction

Mixed use – retail, leisure, housing, student accommodation, hotel


W9 York House

Brownfield

Office Mixed use 1 No ✓ yes Development in Zone 1 should consider the requirements of SFRA Section 6.4.8.

W10 Dexion House

Brownfield

Office Mixed use - retail, office, leisure, residential, student accommodation and hotel


W11 Malcolm Brownfield Cleared site Mixed use - retail, 1 No ✓ yes Development in Zone 1


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Flood Zone



Site in FZ1?


Site in FZ 2?


Site in FZ3?


Planning solution


Highly Vulnerable

More Vulnerable

Less Vulnerable

Water Compatible

House office, leisure, residential, hotel and community use.

should consider the requirements of SFRA Section 6.4.8.

W12 North West Lands

Brownfield

Demolition and construction site

Mixed use - Civic centre, retail, office, leisure, residential, student accommodation, hotel and community use.


W13 Stadium Retail Park

Brownfield

Retail Mixed use - retail, office, leisure, student accommodation, hotel and community use with a limited amount of residential.

1,2 No ✓

No highly vulnerable uses proposed on site

yes no no Yes no N/A Land use in Zone 2 should be restricted to ‘water-compatible’, ‘less vulnerable’ and ‘more vulnerable’ category, or essential infrastructure, with reference to SFRA section 6.4.7

W14 Arena House

Brownfield

Vacant Mixed use - offices, education, student housing or hotel


W14 Crescent House

Brownfield

Education Mixed use - offices, education, student housing or hotel

1,2,3 No Exception Test required for education, student accommodation, hotels in 3a; None of the uses are compatible with 3b

yes no yes no yes no Development within Zone 3a should be restricted to ‘less vulnerable’ land uses with regard to SFRA sections 6.4.4-6. ‘More vulnerable’ land uses should be steered towards zones 1&2

W15 Apex & Karma House

Brownfield

Industrial and office units

Mixed use - Residential, commercial, workspace

1,2 No ✓


yes no yes no no N/A Land use in Zone 2 should be restricted to ‘water-compatible’, ‘less vulnerable’ and ‘more vulnerable’ category, or essential infrastructure, with reference to SFRA section 6.4.7

W16 1 Olympic Way

Brownfield

Office Mixed use to include office

1,2,3 No Partly. Any ‘more vulnerable’ uses proposed as part of mixed use scheme will be subject to an Exception Test


W17 Olympic Way Office

Brownfield

Office Mixed use – Office, hotel, residential, cafes, restaurants, bars, open space



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Flood Zone



Site in FZ1?


Site in FZ 2?


Site in FZ3?


Planning solution


Highly Vulnerable

More Vulnerable

Less Vulnerable

Water Compatible

W18 Wembley Retail Park

Brownfield

Retail, restaurant

Residential 1 No ✓ yes Development in Zone 1 should consider the requirements of SFRA Section 6.4.8.

W19 Stadium Car Park

Brownfield

Car park Mixed use including leisure


W20 Cottrelll House

Brownfield

Residential, office and restaurant

Mixed use - residential, retail, commercial and community facilities


W21 21-31 Brook Avenue

Brownfield

Residential Residential 1,2,3 No Partly. An Exception Test is required for residential uses in 3a. Residential is not compatible with Zone 3b


W22 Wembley Park Station Car Park

Brownfield

Car park Residential 1 No ✓

yes Development in Zone 1 should consider the requirements of SFRA Section 6.4.8.

W23 The Torch/ Kwik Fit

Brownfield

Public house, Kwik Fit

Mixed use – residential, retail


W24 Town Hall Brownfield Listed building with administrative, political and ceremonial roles

Mixed use - office/residential/ community


W25 Amex House

Brownfield

Industry Mixed use - residential/ industry

2,3 No Partly. An Exception Test is required for residential uses in 3a. None of the uses are compatible with Zone 3b

No no yes no yes no Development within Zone 3a should be restricted to ‘less vulnerable’ land uses with regard to SFRA sections 6.4.4-6. ‘More vulnerable’ land uses should be steered towards zones 1&2

W26 Watkin House

Brownfield Car repair garages, industrial, storage and ancillary office buildings.

Office, leisure, residential, managed affordable workspace, community use

1,2,3 No Partly. An Exception Test is required for residential, residential

yes no yes no Yes no Development within Zone 3a should be restricted to ‘less vulnerable’ land uses with regard to SFRA sections 6.4.4-6. ‘More vulnerable’ land uses


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Flood Zone



Site in FZ1?


Site in FZ 2?


Site in FZ3?


Planning solution


Highly Vulnerable

More Vulnerable

Less Vulnerable

Water Compatible

care homes, and some community facilities uses in 3a. None of the uses are compatible with Zone 3b

should be steered towards zones 1&2

W27 Euro Car Parts

Brownfield

Retail, industrial Mixed use - office, leisure, residential, student accommodation, managed affordable workspace, hotel and community use

1,2 No ✓


yes no yes no no N/A The proposed buffer strip will remove the developable area of the site wholly into flood zone 1. Development in Zone 1 should consider the requirements of SFRA Section 6.4.8.

W28 First Way Brownfield

Industrial/retail /warehouses /waste facility

residential/offices/leisure


W29 Second Way

Brownfield

Light industry, offices, storage

Offices, light industry, storage and distribution, some transport related functions, utilities and wholesale markets.


W30 Drury Way

Brownfield

Builder's storage yard and depot

Industrial and employment uses


W31 Great Central Way

Brownfield

Vacant site Industrial, warehousing or other business uses



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Appendix B - Site-Specific Analysis

Site: W13 Stadium Retail Park

Key

Flood Zone 2 Flood Zone 3 Site Boundary/Reference

Medium Probability of flooding High Probability of flooding

Site Information

Area of Site (Ha): 1.1 hectares

Flood Zone(s) 1,2

Proposed Land Use: Mixed use development with predominantly commercial uses,

including retail, office, leisure, student accommodation, hotel

and community use with a limited amount of residential.

Vulnerability Classification of uses: Highly vulnerable: none

More vulnerable: student accommodation, hotels, some

community uses, residential

Less vulnerable: office, leisure

Sequential Test: More vulnerable uses are compatible with Flood Zones 1&2

Less vulnerable uses are compatible with Flood Zones 1&2

Overview of Flood Risk from SFRA Level 2: Wembley Masterplan Area

• Source of Flooding – Wealdstone Brook

• The site is not situated in the immediate vicinity of the river


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• Approx 70% of the site lies in Flood Zone 2 with a medium probability of flooding. The remainder is

in Flood Zone 1

• The site is offered a degree of protection in the form of the bordering wall

• Flood depths are shallow and the speed of the flood waters will be negligible

• Water is unlikely to inundate the site for any longer than approximately 6 hours

• Risk to life will be low under normal operating conditions

Planning Recommendations from SFRA Level 2: Wembley Masterplan Area

• Refer to Appendix C for Strategic Flood Risk Assessment SFRA) Level 1 (2007) recommendations for

Future Development within Zone 2 Medium Probability and Zone 1 Low Probability

• All proposed development will require a detailed Flood Risk Assessment (FRA), in accordance with

Section 6.7 of the Brent Borough SFRA

• The ‘sequential approach’ at site level should be applied to steer development towards areas of

lowest risk within the site

• Density should be varied to reduce the number of vulnerable units in high risk areas

• A positive reduction in the risk of flooding within the Borough must be demonstrated as an outcome

of the proposed development

• Floor levels must be situated above the 1 in 100 year fluvial predicted maximum flood level plus

climate change, incorporating an allowance for freeboard (refer to section 6.8 of the SFRA)

• Implement SUDS to ensure that runoff from the site (post redevelopment) does not exceed

Greenfield runoff rates. Any SUDS design must take due account of groundwater and geological

conditions (refer Section 6.9 of the SFRA)

• To ensure the safety of the residents and employees during a flood, access and egress routes must

be designed to meet Environment Agency defined criteria, as set out in Appendix D of the SFRA

• Ensure that there is no net loss in floodplain storage as a result of the proposed development

• It must be demonstrated that the proposed development does not result in an increase in maximum

flood levels, within adjoining properties


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Site: W14 Crescent House

Key

Site Information


Flood Zone(s) 1,2,3

Proposed Land Use: Offices, education, student housing or hotel


More vulnerable: education, student accommodation, hotels

Less vulnerable: office



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Less vulnerable uses are compatible with Zones 1,2&3a

An Exception Test is required for ‘more vulnerable’ uses in 3a

None of the proposed uses are compatible with Zone 3b

Exception Test • Developing the site to deliver new jobs and homes in the

Wembley Growth Area provides wider sustainability

benefits to the community that outweigh flood risk

• Any development on W13 must meet the planning

requirements set out below in order to meet the second

part of the exception test

Overview of Flood Risk


• The majority of the site is situated within Flood Zone 2 Medium Probability.

• Small areas adjoining the watercourse fall within Flood Zone 3a High Probability

• The remainder is in Flood Zone 1

• The site is not offered any form of protection from raised formal defences

• The depth of flooding across much of the site is likely to be minimal

• Floodwaters will inundate the site for a short period, not exceeding 12 hours

• The potential risk to life is considered negligible

• The potential risk of groundwater flooding within the site is considered negligible



Future Development within Zone 3b Functional Floodplain (Undeveloped Areas), Zone 2 Medium

Probability and Zone 1 Low Probability






• Development should be avoided in the small area of the site that is situated in Flood Zone 3





• Within Flood Zone 3a High Probability, self contained basements that do not have internal access to

higher floors within the building should not be permitted. Self contained basements that do have

internal access to higher floors within the building may be permitted, however sleeping

accommodation should not be provided at basement level









• A minimum 8 metres buffer zone must be provided for the waterway

• The development should contribute to the re-naturalisation of Wealdstone Brook


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Site: W15 Apex and Karma House

Key



Site Information


Flood Zone(s) 1,2

Proposed Land Use: Mixed use development with hotel, residential, commercial

including affordable workspace


More vulnerable: hotels, residential

Less vulnerable: office, general industry



Overview of Flood Risk from SFRA Level 2: Wembley Masterplan Area


• The site is not situated in the immediate vicinity of the river


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• Approx 30% of the site lies in Flood Zone 2 with a medium probability of flooding. The remainder is

in Flood Zone 1

• floodwaters will inundate the site for a short period, not exceeding 12 hours

• The potential risk to life is considered negligible





Future Development within Zone 2 Medium Probability and Zone 1 Low Probability
















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Site: W16 1 Olympic Way

Key

Site Information


Flood Zone(s) 1,2,3

Proposed Land Use: Redevelopment should re-provide office floor space.


More vulnerable: none identified but could form part of

mixed use development

Less vulnerable: office

Sequential Test: Less vulnerable uses are compatible with Zones 1,2&3a

More vulnerable uses are compatible with Flood Zones 1&2

More vulnerable uses will be subject to an Exception Test

The proposed use is not compatible with Zone 3b


December 2012

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• Source of Flooding – overland flow that has exceeded the capacity of the adjacent Wealdstone Brook

• The majority of the site is situated within Flood Zone 2 Medium Probability

• Small areas adjoining the watercourse fall within Flood Zone 3 High Probability

• The remainder is in Flood Zone 1


• Floodwaters will inundate the site for a short period, not exceeding 12 hours

• Indicative flood depths at the site exceed 1000 mm in some areas

• The potential risk to life within inundated areas of the site is considered relatively high

• Development should be avoided in these areas



• Refer to Appendix C for Strategic Flood Risk Assessment SFRA) Level 1 (2007) planning

recommendations for Future Development within Zone 3b Functional Floodplain (Undeveloped

Areas), Zone 3a High Probability, Zone 2 Medium Probability and Zone 1 Low Probability


• Wherever possible, development of the site should be steered towards areas of the site that are not

currently affected by flooding


























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Site: W21 21-31 Brook Avenue

Key

Site Information


Flood Zone(s) 1,2,3

Proposed Land Use: Residential use and associated amenity space


More vulnerable: residential

Less vulnerable: none



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An Exception Test is required for ‘more vulnerable’ uses in 3a

The proposed use is not compatible with Zone 3b









• Some of the site adjacent to Wealdstone Brook is in the functional flood plain (Zone 3b)

• Approximately half the site is in flood zone 1

• The site also includes areas within Flood Zone 3 High Probability and Flood Zone 2 Medium

Probability

Planning Recommendations



Areas), Zone 3b Functional Floodplain (Developed Areas), Zone 3a High Probability, Zone 2 Medium


• Encroachment into the Functional Flood Plain will not be permitted




• Residential developments in Zone 3a should pass an Exception Test


Section 6.7 of the Brent Borough SFRA including an assessment of flood extent, depth and speed




climate change, incorporating an allowance for freeboard (refer to section 6.8 of the SFRA).








• To ensure the safety of the residents during a flood, access and egress routes must be designed to

meet Environment Agency defined criteria, as set out in Appendix D of the SFRA


• Flow routes should not be obstructed






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Site: W25 Amex House

Key

Site Information


Flood Zone(s) 2,3

Proposed Land Use: Mixed use development, including residential, office and

managed affordable workspace for creative industries


More vulnerable: residential

Less vulnerable: office, general industry

Sequential Test: Less vulnerable and more vulnerable uses are compatible with

Flood Zone 2

More vulnerable uses require an Exception Test for zone 3a

None of the proposed uses are compatible with zone 3b


December 2012

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• Approximately half the site lies in flood zone 2 and half in flood zone 3

• Some parts adjacent to the watercourse could lie in the Functional Flood Plain

Planning Recommendations from Site Specific Allocations PPS25 Sequential Test (June 2010)



Areas), Zone 3a High Probability and Zone 2 Medium Probability

• Encroachment into the Functional Flood Plain will not be permitted




• Residential developments in Zone 3a should pass an Exception Test

• Highly vulnerable development should be avoided within this site


Section 6.7 of the Brent Borough SFRA including an assessment of flood extent, depth, speed and

whether the existing buildings are permeable to flood waters


















• A buffer zone must be provided for the waterway



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Site: W26 Watkin Road

Key

Site Information


Flood Zone(s) 1,2,3

Proposed Land Use: Mixed use development including office, leisure, residential,

managed affordable workspace, and community use. Extra

care housing or family housing could form part of any housing

mix.


More vulnerable: residential, residential care homes, some

community facilities

Less vulnerable: offices, general industry, leisure

Sequential Test: Less vulnerable and more vulnerable uses are compatible with

Flood Zone 2

More vulnerable uses require an Exception Test for zone 3a

None of the proposed uses are compatible with zone 3b




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• Source of Flooding – overland flow that has exceeded the capacity of the adjacent Wealdstone Brook

• Most of the site lies in Flood Zone 2 with a medium probability of flooding. Some parts adjacent to

the watercourse lie in Flood Zone 3

• Some low areas adjoining the river are affected by Zone 3b Functional Floodplain

• floodwaters will inundate the site for a short period, not exceeding 12 hours

• The site has no protection from raised formal defences


• The potential risk to life within inundated areas (zones 3a and 3b) is considered relatively high.

Development should be avoided in these areas

• The potential risk to life in Zone 2 is considered negligible

Planning Recommendations from Site Specific Allocations PPS25 Sequential Test (June 2010)



Areas), Zone 3b Functional Floodplain (Developed Areas), Zone 3a High Probability, Zone 2 Medium





• ‘More vulnerable’ uses (residential, residential care homes, community facilities) should be located

away from Flood Zone 3

• Any ‘more vulnerable’ uses proposed in Flood Zone 3a will be subject to the Exception Test

• Highly vulnerable development should be avoided within this site

• Encroachment into the Functional Flood Plain (3b) will not be permitted

• All proposed redevelopment within Site W26 will require a detailed Flood Risk Assessment (FRA), in

accordance with Section 6.7 of the Brent Borough SFRA

• Throughout the site, (re)development must deliver a measurable reduction in flood risk. Risk

reduction measures for consideration should include SUDS to seek a reduction in the rate of runoff

from the site





• Threshold floor levels should be kept above predicted 1 in 100 year flood levels plus an allowance for

climate change (refer to section 6.8 of the SFRA)

• Loss of flood plain storage due to new development should be compensated



Greenfield runoff rates

• Any SUDS design must take due account of groundwater and geological conditions (refer Section 6.9

of the SFRA)

• Safe dry access and egress should be provided (see Appendix D of the SFRA)

• A buffer zone must be provided for all culverted and open waterways


Site: W27 Euro Car Parts


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Key



Site Information


Flood Zone(s) 1,2

Proposed Land Use: Mixed use development including office, leisure, residential,

student accommodation, managed affordable workspace,

hotel and community use.


More vulnerable: student accommodation, hotels, some

community uses, residential

Less vulnerable: office, leisure, general industry





• Approx 95% of the site lies in Flood Zone 1

• Sections close to the Wealdstone Brook are in Flood Zone 2 with a medium probability of flooding


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Planning Recommendations


recommendations for Future Development within Zone 2 Medium Probability and Zone 1 Low

Probability








• A buffer zone must be provided for the waterway



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Appendix C - Strategic Flood Risk Assessment SFRA) Level 1 (2007)

Extract - planning recommendations

Future Development within Zone 3b Functional Floodplain (Undeveloped Areas)

Planning Recommendations – Allocation of Land for Future Development (relevant only following

the application of the Sequential Test) Areas of Functional Floodplain that are currently

undeveloped should be protected for flood storage purposes. Future development should be

restricted to water-compatible uses and essential infrastructure that has to be there (in accordance

with PPS25). Careful consideration should be given to the Council’s emergency response in times of

flood to ensure that public safety is not compromised.

Future Development within Zone 3b Functional Floodplain (Developed Areas)

It is important to recognise that, within Zone 3b Functional Floodplain, ‘previously developed land’

relates solely to existing buildings that are impermeable to flood water. The land surrounding

these buildings are important flow paths and/or flood storage areas that must be retained.


the application of the Sequential Test)

1. Future redevelopment of previously developed land within Zone 3b Functional Floodplain

(Developed Areas) will only be permitted within the footprint of an existing building that is

impermeable to flooding. Development must be restricted to ‘less vulnerable’ land uses. ‘More

vulnerable’ land uses must be actively discouraged, and should only be considered within sites of an

equivalent existing land use.

2. In all instances, it will be necessary to ensure that the requirements of the Exception Test are

satisfied. In planning terms, it must be demonstrated that “the development provides wider

sustainability benefits to the community that outweigh flood risk”. It should be recognised that

property situated within Zone 3b Functional Floodplain will be subject to frequent flooding, on

average, no less than once in every 20 years. There are clear sustainability implications to be

considered in this regard, and it is highly questionable whether insurance against flooding related

damages will be available in the longer term.

3. There should be a presumption against all building extensions (including outbuildings) within Zone

3b Functional Floodplain.

4. To satisfy the remaining criteria of the Exception Test, all development within Zone 3b Functional

Floodplain (existing developed areas only) should be designed in accordance with the development

control recommendations below.

Future Development within Zone 3a High Probability

Defended Areas within Zone 3a High Probability There are not many raised defences in the Borough

and few existing defences offer some degree of protection to the properties in Wembley and

Kingsbury areas. Whilst it is recognised that there is a government led commitment to the retention

of this system of defences, the statutory responsibility for flood defence remains with the individual

landowner. For this reason, all future development must assess (and mitigate) the residual risk of

flooding should the defences fail and/or fall into disrepair in future years. The assessment of flood

hazard (refer Section 5.3) has identified areas within which there may be a risk to life should these

raised defences fail in a catastrophic manner (i.e. the Rapid Inundation Zone). Where possible,

future development should be avoided in these areas. For all areas of Zone 3a High Probability


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situated behind raised defences, a suite of specific development control recommendations have

been provided, as detailed below.



1. Future development within Zone 3a High Probability should be restricted to ‘less vulnerable’ land

uses, in accordance with PPS25 (Appendix D) Table D2. ‘More vulnerable’ land uses, including

residential development, should be steered towards zones of lower flood risk (i.e. Zone 2 Medium

Probability or Zone 1 Low Probability) within which suitable land may be available in adjoining

character areas.

2. Where non-flood risk related planning matters dictate that ‘more vulnerable’ (residential)

development should be considered further, it will be necessary to ensure that the requirements of

the Exception Test are satisfied. In planning terms, it must be demonstrated that “the development

provides wider sustainability benefits to the community that outweigh flood risk”, and that “the

development is on developable previously developed land, or that there are no reasonable

alternative sites on previously developed land”.

3. To satisfy the remaining criteria of the Exception Test, all development within Zone 3a High

Probability should be designed in accordance with the development control recommendations

below

Future Development within Zone 2 Medium Probability



1. In accordance with PPS25, land use within Zone 2 Medium Probability should be restricted to the

‘water-compatible’, ‘less vulnerable’ and ‘more vulnerable’ category (including residential

development), or essential infrastructure, to satisfy the requirements of the Sequential Test

2. Where non-flood risk related planning matters dictate that ‘highly vulnerable’ development

should be considered further, it will be necessary to ensure that the requirements of the Exception

Test are satisfied. In planning terms, it must be demonstrated that “the development provides wider

sustainability benefits to the community that outweigh flood risk”, and that “the development is on

developable previously developed land, or that there are no reasonable alternative sites on

previously developed land”.

3. To satisfy the remaining criteria of the Exception Test, all development within Zone 2 Medium

Probability should be designed in accordance with the development control recommendations

below.

Future Development within Zone 1 Low Probability

Planning Recommendations – Allocation of Land for Future Development

There are generally no flood risk related constraints placed upon land use within Zone 1 Low

Probability (in accordance with PPS25), however it is important to recognise that future

development within this zone may adversely impact upon the existing flooding regime if not

carefully managed. Flooding related issues of a localised nature may also occur within Zone 1 Low

Probability. For this reason, all development should be carried out in accordance with the

development control recommendation below. Within ‘dry island’ areas that are surrounded by a

degree of flood risk, effective emergency planning measures should be in place to ensure that the

risk to life is minimised in case of flooding.

Documents

Wembley Area Action Plan WAAP... · Area Action Plan. 5.3 Similarly, the source of reasonably available alternative sites for comparison includes any sites within the Wembley Growth