calder valley strategic flood risk assessment · • the sfra is a strategic review of flood risk,...

Calderdale and KirkleesMetropolitan Borough

Council, and the City ofWakefield Metropolitan

District Council

Calder ValleyStrategic Flood Risk

Assessment

November 2008

FINAL REPORT

JBA ConsultingThe Brew HouseWilderspool ParkGreenhall's AvenueWARRINGTONWA4 6HLUKt: +44 (0)1925 437 020f: +44 (0)1925 437 [email protected]

Calder ValleyStrategic Flood Risk AssessmentNovember 2008

JBA Consultingwww.jbaconsulting.co.uk

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REVISION HISTORY

Revision Ref./Date Issued

Amendments Issued to

Draft Report

13th June 2008

Peter Gooding, City ofWakefield MDC

Phil Ratcliffe, Calderdale MBC

Les Reason, Kirklees MBC

Gary Cliff, EnvironmentAgency – North East Region

Final Draft Report

27th August 2008

Comments included from:

Peter Gooding 15/07/08

Steve Wright 26/06/08

Amy Heys & EA FloodMapping team 04/07/08 &18/07/08

Peter Gooding, Peter Davies,Phil Ratcliffe, Les Reason &Steve Wright

Gary Cliff & Amy Heys

Final Report

November 2008

Comments included from:

Peter Davis 23/09/08

Steve Wright 01/09/08

Amy Heys & EA FloodMapping team 03/10/08

Peter Gooding, Peter Davies,Phil Ratcliffe, Les Reason &Steve Wright

Gary Cliff & Amy Heys

CONTRACT

This report describes work commissioned by each council under PLA00197 of 02/06/2008. TheCouncil’s representatives for the contract were Les Reason, Peter Gooding and Phil Ratcliff. ChrisIsherwood, Mervyn Pettifor and Jonathan Cooper of JBA Consulting carried out the work.

Prepared by: ................................................... Chris Isherwood, BSc CertWEM DipWEMAnalyst

.................................................Mervyn Pettifor, IEng AMICE MCIWEM FIWODirector, Flood Management Support Services Ltd

Reviewed by: ................................................... Jonathan Cooper, BEng MSc CEng MICE MICWEMMIoD

Divisional Manager



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PURPOSE

This document has been prepared solely as a Final Report for Calderdale and Kirklees MetropolitanBorough Council, and the City of Wakefield Metropolitan District Council. JBA Consulting acceptsno responsibility or liability for any use that is made of this document other than by the Client for thepurposes for which it was originally commissioned and prepared.

ACKNOWLEDGMENTS

The provision of EA data on flood risk arising from the JBA’s NE Broadscale modelling project hasprovided each local authority with a powerful data source to inform and influence spatialplanning. Amy Heys, Gary Cliff and Sam Kipling of the EA were extremely helpful. Appreciationalso goes to Les Reason for his management and support of the project.



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EXECUTIVE SUMMARY

Executive Summary Heading

The purpose of this Strategic Flood Risk Assessment (SFRA) is to identify and analyse current andfuture broad scale flooding issues for key locations in Calderdale, Kirklees and Wakefield localauthority areas and provide support for further assessment and sequential testing of proposeddevelopment allocations. It will form a key component of each council’s Strategic EnvironmentalAssessment (SEA), as required for the production of their Local Development Framework (LDF). Inturn the SEA will be used to inform each council’s Sustainability Appraisal (SA) and selection ofspecific development allocation sites.

Planning Policy Statement 25 (PPS 25) and the Practice Guide to PPS 25, provide the latestGovernment thinking on development and flood risk. The Departments for Communities & LocalGovernment, and Environment, Food & Rural Affairs came together to produce this policy andguidance in December 2006, in recognition of the critical role that land use planning can play inavoiding and protecting people and property from flooding from all sources, and helpingcommunities to adapt to a changing climate.

Flood risk is a material consideration in planning and Calderdale, Kirklees and Wakefield LPAs allrecognise this by having flood risk related “saved” policies in their recently updated UDPs. Work ondeveloping LDFs is underway and these “saved” policies will be further updated and strengthenedto better reflect the increasing nature of flood risk and the importance of a balanced andsustainable approach to ensuring necessary safe regeneration, growth and economic investmentacross the region.

LPA members and officers play a critical role in furthering the integration and synergies of land useplanning and flood risk management. In order to help better identify these synergies and assistthem with their planning and development control decision making; better risk data andinformation for existing and future communities is required on actual flood risk (as opposed totheoretical risk); this is one of the primary objectives of the SFRA.

JBA have developed a suite of flood maps to support the SFRA. The SFRA Flood Risk Maps usedshow Fluvial Flood Extent and Depth, Areas Naturally Vulnerable to Surface Water Flooding andareas sensitive to predicted Climate Change. They are an essential element to the effectivedelivery of the flood risk Sequential and Exception Tests for proposed land use allocations, asrequired by PPS 25. They provide a valuable source of broad scale, current and future flood riskinformation and assist with early and strategic consideration of development allocations andrelated planning management decisions. In addition they provide valuable information toemergency planners and emergency services organisations in the planning and delivery of theirduties and responsibilities.

The Sequential and Exception Tests are essential requirements of PPS 25 and this SFRA explains theRisk Based Sequential Approach in which these tests are carried out for proposed developmentallocations; and recommends the use of flood risk indicators and a flood risk balance sheet to assistplanners in their strategic land use considerations. A suite of SFRA Flood Risk Maps for key locationswithin local authority areas are provided in paper format to supplement the Environment Agency’sFlood Maps along with information on their use and interpretation. These Maps have also beenprovided for the whole district in GIS layers. These maps should be used to assist local authorityplanners, development control teams and developers in carrying out a sieving process towardsSequential Testing taking an approach of avoidance and substitution before mitigation. Guidanceis also provided on undertaking detailed flood risk assessments for specific development proposalsand planning applications.



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The Region is experiencing significant growth and there is a need to provide sufficient homes andjobs to support this growth. This need for growth, regeneration and economic developmentpresents both opportunities and challenges for flood risk management. PPS 25 requires that newdevelopment should be made safe and not increase flood risk elsewhere and with carefulplanning, appropriate design and layout etc. developments can meet these requirements.

In order to evaluate sites for development allocation, the Councils may consider the following:

• Sites put forward for development should be assessed against the SFRA flood maps.Sites should be selected at lower risk of flooding in preference to higher risk areas.Developers will need to provide sufficient information to enable the Council toassess a Sequential Test which will demonstrate that there are no reasonablyavailable, alternative sites that are situated in a lower flood risk zone. Where phaseddevelopment is planned, Sequential Testing for the development should be used toidentify those areas where development should be discouraged or avoided.

• Before some sites are allocated and if a site is considered to be critical toregeneration and/or the core strategy, the Council should opt to undertake a FloodRisk Assessment (including sequential and, where necessary, exceptions tests) inorder to first justify the sustainability and the deliverability of the allocation

• Departures from the Sequential Flood Risk Test involving the need for development inhigher risk zones need to be justified. A developer will need to work with the LPA andprovide reasoned justification wherever the Exception Test needs to be applied tomeet current land use policies.

• The SFRA is a strategic review of flood risk, based on existing available informationand does not provide the site specific consideration of flood risk and mitigationmeasures required of a Flood Risk Assessment. The developer will need to undertakea detailed Flood Risk Assessment to address relevant parts of the Exceptions Test.

• The developable area may further be reduced by the need for a maintenanceeasement where there is a watercourse within or adjacent to a site. Typically an 8maccess strip, void of development, is required along the bank top for maintenancepurposes. This is likely to reduce the available developable area.

• Where residential development in Flood Zone 3 is proposed, passing the ExceptionTest is likely to be harder and applications are likely to be opposed by theEnvironment Agency. Any development planned within Flood Zone 3 will require aFlood Risk Assessment to demonstrate that development is sustainable and safe.

• Where development sites encroach into Flood Zone 3, the Council should considerrecommending that Flood Zone 3 areas should only be developed as watercompatible uses or Public Open Space.

• Where employment or residential developments are proposed within higher riskzones, the site specific Flood Risk Assessment should consider the likely depth offlooding as this will indicate the likely extent of mitigation measures required. Thedepth of flooding can be used as an indication of whether or not the Exception Testis likely to be passed. This will be less likely where the depth of flooding is likely torequire substantial mitigation.

• A site specific Flood Risk Assessment should consider all sources of flooding andmitigation measures will be required to compensate for loss of floodplain storage.Depending on the extent of flooding, mitigation measure in these instances maysignificantly reduce the developable area. Consideration should also be given tothe likely impact of development elsewhere. For example, surface water drainagefrom greenfield development is likely to increase flood risk to neighbouringdevelopments unless surface water drainage is effectively managed.



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• The determination of acceptability remains with the LPA, and will draw upon theadvice of the Environment Agency and the Emergency Planning officer.

Balancing and appropriately weighing key sustainable development factors including flood riskcan deliver sustainable growth whist reducing overall flood risks to people and property.



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ABBREVIATIONS

CFMP Catchment Flood Management PlanDC District CouncilCOW Critical Ordinary WatercourseDPD Development Planning DocumentEA Environment AgencyEI Essential InfrastructureEU European UnionFEH Flood Estimation HandbookFRA Flood Risk AssessmentFZ Flood ZoneHV Highly VulnerableIDB Internal Drainage BoardIDD Internal Drainage DistrictLDF Local Development FrameworkLDS Local Development SchemeLiDAR Light Detection and RangingLPA Local Planning AuthorityLV Less VulnerableMV More VulnerableNFCDD National Fluvial and Coastal Defence DatabaseODPM Office of the Deputy Prime MinisterOS Ordnance SurveyPPG Planning Policy GuidancePPS Planning Policy StatementRFRA Regional Flood Risk AssessmentRPB Regional Planning BodyRPG Regional Planning GuidanceRSS Regional Spatial StrategySA Sustainability AppraisalSEA Strategic Environmental AssessmentSFRA Strategic Flood Risk AssessmentSMP Shoreline Management PlanSuDs Sustainable Drainage SystemsSWAMP Surface Water Management PlansUDP Unitary Development PlanUHCS Urban Housing Capacity StudyW Water-compatible



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CONTENTS

PageREVISION HISTORY iCONTRACT iPURPOSE iiACKNOWLEDGEMENTS iiEXECUTIVE SUMMARY iiiCONTENTS vi

1� INTRODUCTION ----------------------------------------------------------------------------------1�1.1� Background ....................................................................................................................................... 1�1.2� Study Objectives............................................................................................................................... 2�1.3� Format of the SFRA and Key Outputs ........................................................................................... 2�

2� UNDERSTANDING FLOOD RISK FROM ALL SOURCES -------------------------------------------3�2.1� Introduction ....................................................................................................................................... 3�2.2� Flood Risk Management Drivers .................................................................................................... 4�2.3� Climate Change............................................................................................................................... 7�2.4� Basic Elements of Flood Risk Assessment...................................................................................... 8�2.5� Environment Agency FRM Plans, Strategies and Schemes.................................................... 11�

3� INTEGRATED FLOOD RISK WITH LOCAL AUTHORITY PLANNING ----------------------------- 17�3.1� Introduction ..................................................................................................................................... 17�3.2� Key Strategic Links between FRM and Planning ...................................................................... 17�3.3� National Planning Policy ............................................................................................................... 19�3.4� Regional Planning Policy............................................................................................................... 22�3.5� Local Planning Policy..................................................................................................................... 23�3.6� Balanced and Sustainable Approach ....................................................................................... 26�

4� RISK BASED SEQUENTIAL APPROACH--------------------------------------------------------- 28�4.1� Introduction ..................................................................................................................................... 28�4.2� Summary of the Risk Based Sequential Approach .................................................................. 28�4.3� Levels of Flood Risk Assessment ................................................................................................... 30�4.4� Delineation of Flood Zones ........................................................................................................... 31�4.5� Application of the Sequential Test .............................................................................................. 33�4.6� Flood Risk Vulnerability Classification.......................................................................................... 35�4.7� Application of the Exceptions Test.............................................................................................. 36�4.8� Management Decisions and Actions......................................................................................... 38�4.9� Flood Risk Indicators and Balance Sheet................................................................................... 40�4.10� Influencing Land Use Planning..................................................................................................... 41�

5� OVERVIEW OF FLOOD RISKS ------------------------------------------------------------------ 44�5.1� Introduction ..................................................................................................................................... 44�5.2� Main River Flooding........................................................................................................................ 44�5.3� Calder Catchment......................................................................................................................... 45�5.4� Aire Catchment .............................................................................................................................. 46�5.5� Don Catchment.............................................................................................................................. 47�5.6� Ordinary Watercourse Flooding .................................................................................................. 48�5.7� Surface Water Flooding................................................................................................................. 48�5.8� Groundwater Flooding .................................................................................................................. 49�5.9� Reservoir Flooding .......................................................................................................................... 49�5.10� Condition of Flood Defences....................................................................................................... 51�5.11 Residual Flood Risk.......................................................................................................................... 51



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CONTENTS

Page

6� SFRA FLOOD RISK MAPS----------------------------------------------------------------------- 53�6.1� Introduction ..................................................................................................................................... 53�6.2� PPS 25 Flood Zone Maps ............................................................................................................... 54�6.3� SFRA Risk Maps: Interpretation and use ..................................................................................... 54�6.4� Fluvial Flood Extent and Depth Maps......................................................................................... 55�6.5� Climate Change Sensitivity Maps ............................................................................................... 56�6.6� Areas Naturally Vulnerable to Surface Water Flooding Maps............................................... 57�6.7� Conclusion and Further use of SFRA Flood Risk Maps ............................................................. 57�

7� GUIDANCE FOR DETAILED FLOOD RISK ASSESSMENTS--------------------------------------- 60�7.1� Introduction ..................................................................................................................................... 60�7.2� General Principles........................................................................................................................... 61�7.3� Assessment and Mitigation of Fluvial Risk................................................................................... 62�7.4� Assessment of Surface Water Drainage Issues.......................................................................... 63�7.5� Flood Zone 3b – The Functional Floodplain............................................................................... 63�7.6� Flood Zone 3a – High Probability ................................................................................................. 64�7.7� Other Known Flood Risk Areas Including Internal Drainage Districts.................................... 69�

8� CONCLUSION---------------------------------------------------------------------------------- 71�8.1� Overview of SFRA Outcomes ....................................................................................................... 71�8.2� Level 2 SFRA..................................................................................................................................... 72�8.3� Surface Water Management Plans ............................................................................................ 73�8.4� Guidance for Development Control .......................................................................................... 74�8.5� Monitoring........................................................................................................................................ 75�

APPENDICES:

APPENDIX A: -� FLOOD RISK ZONES / FLOOD RISK VULNERABILITY CLASSIFICATION�

APPENDIX B: -� EXAMPLE FLOOD RISK BALANCE SHEET�

APPENDIX C: -� LPA FLOOD ZONE 3B CONFIRMATION LETTERS�

FIGURES

TABLES

MAPS



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LIST OF FIGURES

Figure 2-1: Flooding From All Sources ................................................................................................................. 8�

Figure 2-2: Source – Pathway – Receptor Model........................................................................................... 10�

Figure 2-3: Calder CFMP Policy Units ................................................................................................................ 13�

Figure 3-1: Flood Risk in an Integrated Planning Framework ....................................................................... 18�

Figure 4-1: Overview of Risk Based Sequential Approach........................................................................... 29�

Figure 4-2: Sequential Test Sieving Process...................................................................................................... 34�

Figure 4-3: Where the Exception Test Applies................................................................................................. 37�

Figure 7-1: Illustration of the Undefended Area Case .................................................................................. 65�

Figure 7-2: Illustration of the Defended Area Case ....................................................................................... 65�

LIST OF TABLES

Table 2-1: Calder CFMP Draft Actions ............................................................................................................. 14�

Table 4-1: Suggested Screening Criteria for Mitigation Measures.............................................................. 39�

Table 4-2: Scoring of Indicators in Reviewing Indicative Acceptability of Proposed Development... 43�

Table 5-1: Previously Designated Critical Ordinary Watercourses.............................................................. 48�

Table 5-2: Reservoir Location Details................................................................................................................ 49�

Table 5-3: Reservoir Consequence Classification.......................................................................................... 50�

Table 5-4: NFCDD Condition Ratings for Flood Defences ............................................................................ 51�

Table 7-1: Flood Hazard Thresholds .................................................................................................................. 69�



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LIST OF MAPS

Calderdale, Kirklees and Wakefield Councils have only been supplied with SFRA Flood Risk Mapsfor their region. The Environment Agency has been supplied with all maps.

SET A CALDERDALE, KIRKLEES & WAKEFIELD PPS 25 FLOOD ZONE MAPSFigure A 1-1 Calderdale PPS 25 Flood Zone MapsFigure A 2-1 Kirklees PPS 25 Flood Zone MapsFigure A 3-1 Wakefield PPS 25 Flood Zone Maps

SET B INDIVIDUAL FLOOD ZONE MAPSFigure B 1-1 BrighouseFigure B 1-2 Hebden BridgeFigure B 1-3 LuddendenFigure B 1-4 MytholmroydFigure B 1-5 Sowerby BridgeFigure B 1-6 TodmordenFigure B 2-1 DewsburyFigure B 2-2 HolmfirthFigure B 2-3 Honley and NeileyFigure B 2-4 HuddersfieldFigure B 2-5 MarsdenFigure B 2-6 MelthamFigure B 2-7 MirfieldFigure B 2-8 SlaithwaiteFigure B 3-1 HorburyFigure B 3-2 KnottingleyFigure B 3-3 NormatonFigure B 3-4 WakefieldFigure B 3-5 CastlefordFigure B 3-6 Pontefract

SET C FLUVIAL FLOOD EXTENT AND DEPTH MAPSFigure C 1-1 BrighouseFigure C 1-2 Hebden BridgeFigure C 1-3 LuddendenFigure C 1-4 MytholmroydFigure C 1-5 Sowerby BridgeFigure C 1-6 TodmordenFigure C 2-1 DewsburyFigure C 2-2 HolmfirthFigure C 2-3 Honley and NeileyFigure C 2-4 HuddersfieldFigure C 2-5 MarsdenFigure C 2-6 MelthamFigure C 2-7 MirfieldFigure C 2-8 SlaithwaiteFigure C 3-1 HorburyFigure C 3-2 KnottingleyFigure C 3-3 NormatonFigure C 3-4 WakefieldFigure C 3-5 CastlefordFigure C 3-6 Pontefract



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SET D CLIMATE CHANGE SENSITIVITY MAPSFigure D 1-1 BrighouseFigure D 1-2 Hebden BridgeFigure D 1-3 LuddendenFigure D 1-4 MytholmroydFigure D 1-5 Sowerby BridgeFigure D 1-6 TodmordenFigure D 2-1 DewsburyFigure D 2-2 HolmfirthFigure D 2-3 Honley and NeileyFigure D 2-4 HuddersfieldFigure D 2-5 MarsdenFigure D 2-6 MelthamFigure D 2-7 MirfieldFigure D 2-8 SlaithwaiteFigure D 3-1 HorburyFigure D 3-2 KnottingleyFigure D 3-3 NormatonFigure D 3-4 WakefieldFigure D 3-5 CastlefordFigure D 3-6 Pontefract

SET E AREAS VULNERABLE TO SURFACE WATER FLOODING MAPS (1:100yr)Figure E 1-1 TodmordenFigure E 1-2 Hebden BridgeFigure E 1-3 MytholmroydFigure E 1-4 Sowerby BridgeFigure F 1-5 BrighouseFigure E 1-6 HuddersfieldFigure E 1-7 MirfieldFigure E 1-8 DewsburyFigure E 1-9 NW WakefiedFigure E 1-10 SE WakefieldFigure E 1-11 CastlefordFigure E 1-12 Pontefract

SET F AREAS VULNERABLE TO SURFACE WATER FLOODING MAPS (1:1000yr)Figure F 1-1 TodmordenFigure F 1-2 Hebden BridgeFigure F 1-3 MytholmroydFigure F 1-4 Sowerby BridgeFigure F 1-5 BrighouseFigure F 1-6 HuddersfieldFigure F 1-7 MirfieldFigure F 1-8 DewsburyFigure F 1-9 NW WakefiedFigure F 1-10 SE WakefieldFigure F 1-11 CastlefordFigure F 1-12 Pontefract

SET G CALDERDALE, KIRKLEES AND WAKEFIELD FORMER COWS AND IDD MAPSFigure G 1-1 Calderdale COWs and IDD MapFigure G 2-1 Kirklees COWs and IDD MapFigure G 3-1 Wakefield COWs and IDD Map



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1 INTRODUCTION

1.1 Background

JBA Consulting was commissioned in February 2008 by Calderdale, Kirklees and WakefieldCouncils to undertake a review of the existing Strategic Flood Risk Assessment (SFRA) fortheir combined districts and update it, in accordance with the current requirements ofPlanning Policy Statement 25 (PPS 25). Building on information already available a Level 1SFRA study was undertaken to identify and analyse current and future flooding issues for keylocations in each local authority area to support LPA assessment of specific developmentallocation sites.

Key additional areas of work building on the previous SFRA include:

• Taking account of advances in risk information from data collection and process;

• Inclusion of climate change mapping;

• Provision of flood extent, depth and hazard maps;

• Identification of functional floodplain;

• Consideration of flooding from “other sources”; and

• A greater focus on the application of the PPS 25 Exception Test.

It is recognised that considerable land use pressures for regeneration, inward investmentand economic growth exist across the districts and this SFRA will inform/support the RegionalSpatial Strategy (RSS) and guide council’s in their strategies, policies and decision making inrespect of their Local Development Frameworks (LDFs) and Local Development Documents(LDDs).

Much of the three local authority districts are located within the River Calder catchment.Flood processes and flood risk issues across the districts are inextricably linked by the RiverCalder and its many tributaries and the Councils agreed yet again to take a joint approachto producing a SFRA. This is a sensible approach and continues to provide efficiency inunderstanding flood processes and flood risk issues, and allows for improved and integratedconsideration of inter-district flood risk linkages.

The study was carried out according to current best practice and the requirements of PPS25 and the supporting guidance, “Development and Flood Risk: A Practice Guide”. The

This section introduces the SFRA and confirms the study format, objectives and keyt t

Key messages:

• This SFRA reflects the requirements of PPS 25 and supersedes the previous SFRAdated May 2005; and

• It is presented in one volume reflecting the general needs of Calderdale, Kirkleesand Wakefield LPAs and incorporates specific flood risk maps for key locations ineach local authority area.



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emerging Yorkshire and Humber Regional Assembly’s Regional Flood Risk Appraisal and theYorkshire and Humber Regional Spatial Strategy (RSS) have also been referred to.

1.2 Study Objectives

Current Government policy requires local authorities to demonstrate that due regard hasbeen given to the issue of flood risk as part of the planning process. It also requires thatflood risk is managed in an effective and sustainable manner and where new developmentis exceptionally necessary in flood risk areas, the policy aim is to make it safe withoutincreasing flood risk elsewhere. Where possible flood risks should be reduced overall.

The key objectives of this SFRA are to:

• Provide strategic flood risk guidance and advice to planners and developers to helpthem better understand flood risk and planning related issues, both generally and forspecific locations across the study area;

• Investigate and identify the extent and severity of flood risk to the area. Thisassessment will help councils to strike an appropriate balance of various sustainabledevelopment drivers and factors whilst wherever possible, sequentially steeringdevelopment away from areas at highest risk;

• Help LPAs to identify specific locations where further and more detailed flood riskdata and assessment work is required as part of a Level 2 SFRA, prior to theallocation of specific developments;

• Provide data and guidance in the application of the Sequential and Exception Testsfor LPAs to assess specific development sites;

• Supplement current policy guidelines by providing guidance on flood risk assessmentrequirements and a risk based approach to development considerations. This is tohelp ensure that areas allocated for development can be developed in a safe andsustainable manner and is aimed at both councils and developers;

• Contribute to the council’s Strategic Environmental Assessment (SEA), LDF and LDD.The SEA will be used to inform the council’s Sustainability Appraisal (SA), which willaid the selection of suitable land allocations; and

• Be used as a reference document to which all parties involved in planning and floodrisk can reliably turn to for initial advice.

1.3 Format of the SFRA and Key Outputs

The Level 1 SFRA has been prepared in one volume reflecting the general needs ofCalderdale, Kirklees and Wakefield LPAs. In addition, specific SFRA Flood Risk Maps for keylocations with development potential in each local authority area are provided. GIS layershave also been provided for the whole district.

Content and key outputs include:

• Understanding flood risk from all sources;

• Integrating flood risk with local authority land use planning;

• Risk based approach to the SFRA;

• Overview of flood risks for LPAs;

• Data sources and interpretation of maps;

• General guidance for detailed FRAs; and

• SFRA Flood Risk Maps for key locations with development potential.



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2 UNDERSTANDING FLOOD RISK FROM ALL SOURCES

2.1 Introduction

Flooding is a natural process and can happen at any time in a wide variety of locations. Itconstitutes a temporary covering of land not normally covered by water and presents a riskwhen people, human and environmental assets are present in the area which floods. Assetsat risk from flooding can include housing, transport and public service infrastructure,commercial and industrial enterprises, agricultural land and the environmental and culturalheritage.

Climate change predictions are that flood risk will increase due to more frequent severestorms bringing higher intensity rainfall and increasing run-off from land and buildings. Thiswill cause rivers and streams to experience higher than normal flood flows and levels, andsewers and drains to surcharge more frequently than at present. The focus of activity inmeeting these challenges will in future be on flood risk management as opposed to simplyproviding flood defences. It is now widely recognised that whilst we can’t always preventflooding occurring we can manage the risks of it happening and reduce the consequenceswhen flooding does happen.

All operating authorities (Environment Agency, Local Authorities, Internal Drainage Boards),should embrace effective flood risk management issues and actions, and aim to reduceflood risks through a variety on measures including:

• Ensuring planning activities locate vulnerable land uses away from high flood riskareas;

• Providing flood warning and emergency planning activities in flood risk areas;

• Generally raising awareness of flood risks amongst vulnerable communities;

• Constructing and maintaining appropriately designed surface water sewers andculverts;

Key messages:

• Flooding can result from many different sources;

• Flood risk is increasing due to the impacts of climate change;

• Continuing to build and improve flood defences will become increasingly morecostly and difficult to achieve in the future;

• The focus of activity and effort needs to move from flood defence to flood riskmanagement; and

• Local Authority Planners have a key role to play and can benefit greatly fromcurrent flood risk policy guidance and information.

This section contains information and guidance on: Key Flood Risk Management (FRM)policy drivers, climate change, technical assessment of flood risk and flood riskmanagement activities.



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• Using temporary and demountable flood defences and various flood preventionsystems to buildings where appropriate;

• Constructing new flood defences where they are sustainable, and improving andmaintaining those already existing and;

• Constructing weirs, sluices and other flood flow control/management structures.

Pro-active land use planning has a key role to play in flood risk management as it is one ofthe few activities that can result in the avoidance of flood risk as opposed to other activitiesthat can only hope to reduce it. Effective flood risk management through the planningsystem is achieved through a hierarchy where:

• Avoidance of inappropriate development in high risk zones must take priority, before

• Substitution of lower vulnerability uses where avoidance is not possible is considered.Only if avoidance and substitution are not possible,

• Mitigation of the risks through a variety of techniques should be used.

Flood risk assessment at all levels of planning and for all major developments is critical toinform decision making by planners and developers. This is further explained in Section 4 ofthis report.

2.2 Flood Risk Management Drivers

Current FRM policy drivers are principally related to the need to take account of projectedclimate change implications and the availability of funding for all operating authorities tobe able to invest in the provision of sustainable flood risk management. This includesavoidance, substitution and mitigation through land use planning, having regard toflooding from all sources (particularly surface water and not just from rivers), and improvingand maintaining existing flood defences where justified, to protect increasingly vulnerablecommunities. Current key policy related documents provide LPAs with important andvaluable knowledge on the strategic direction of flood risk management and assist theirstrategic land use planning decision making for regeneration, inward investment andgrowth etc.

Key documents currently influencing FRM policy are:

• Future Water – The Government’s water strategy for England – HMGovernment/Defra – Published in February 2008;

• Improving Surface Water Drainage – Consultation to accompany proposals set outin the Government’s Water Strategy, Future Water – Defra – Published in February2008;

• Making Space for Water - Taking forward a new Government strategy for flood andcoastal erosion risk management in England First Government response to theautumn 2004 - Making space for water consultation exercise – Published in March20051;

• Adapting to Changing Coastlines and Rivers – Making Space for Water: Strand SD2Taking forward a new Government strategy for flood and coastal erosion riskmanagement. – Developing a Broader Portfolio of Options to Deliver Flooding andCoastal Solutions – Defra – Executive Summary published in July 2006

• Planning Policy Statement 25 (PPS 25): Development and Flood Risk – Department forCommunities and Local Government - Published in December 20062;

• Planning Policy Statement 25 (PPS 25): Development and Flood Risk Practice Guide –Department for Communities and Local Government – Published in June 20083;



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• Learning lessons from the 2007 floods – An independent review by Sir Michael Pitt –Published in June 20084; and

• Catchment Flood Management Plans (CFMPs) and Shoreline Management Plans(SMPs) – currently being produced by the Environment Agency.

PPS 25 and the Practice Guide are considered further in Section 3 of this report however; it ishelpful to consider some relevant key aspects from the other documents at this point.

2.2.1 Improving Surface Water Drainage

The “Improving Surface Water Drainage” consultation document was produced in supportof the Government’s water strategy and in line with Sir Michael Pitt’s initial conclusions. Thisconsultation considers policy measures to improve the way surface water runoff ismanaged. In particular, it proposes:

1. Issuing Surface Water Management Plans as a tool to improve co-ordinationbetween stakeholders involved in drainage and local management of flood risk;

2. Increasing uptake of sustainable drainage systems by clarifying responsibilities foradoption and management; and

3. Reviewing the ability for premises to connect surface water drainage automaticallyinto the public sewer system.

Current roles and responsibilities are considered along with various options for improving thecurrent surface water drainage situation. In particular the document recognises that SFRAsand Surface Water Management Plans (SWMPs) already form part of the PPS 25 planningframework and there is an aim to enhance their role and make stronger links betweensurface water drainage and strategic planning.

2.2.2 Making Space for Water Strategy

The “Making Space for Water Strategy” is a milestone document that confirms theGovernment’s strategic direction for flood and coastal erosion risk management (FCERM).Over the 20-year lifetime of the new strategy, Government will implement a more holisticapproach to managing flood and coastal erosion risks in England. The approach willinvolve taking account of all sources of flooding, embedding flood and coastal riskmanagement across a range of Government policies, and reflecting other relevantGovernment policies in the policies and operations of operating authorities for flood andcoastal erosion risk management.

The 2004 consultation document “Making Space for Water” sets out the following vision:

“…we want to make space for water so that we can manage the adverse human andeconomic consequences of flooding and coastal erosion while achieving environmentaland social benefits in line with wider government objectives.”

In other words, the aim of the strategy is to balance the three pillars of sustainability,managing flood risk and ensuring that the social and economic benefits which accrue fromgrowth and development are attained. This balanced approach, integrating sustainabledevelopment with responsible risk management, has underpinned this SFRA.

Section 7 of the consultation document deals with measures to reduce flood risk throughland-use planning. This section emphasises the Government’s commitment to ensuring thatthe planning system aims to reduce flood risk wherever possible and, in any event, shouldnot add to it. However, it is acknowledged that 10% of England is already within mappedareas of flood risk and that contained within these areas are some of the brownfield siteswhich other areas of Government policy has identified as a priority for future housingprovision. The document asserts that over the past five years, 11% of new houses were builtin flood-risk areas. The document identifies three sets of measures which may beundertaken to manage flood risk when development is sited in such areas:



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• Protection measures to provide, at minimum, the standards of protection specified inPPS 25;

• Provision of features such as sacrificial areas and compartmentalisation to reducethe consequences of a flood event should one occur (such as functionalfloodplain); and

• Use of construction techniques that increase the flood resistance and resilience ofbuildings.

The document proposes that RSSs and LDFs should take full account of flood risk andincorporate the sequential approach in PPS 25. Moreover, the document encouragesintegration with other planning systems, in particular Catchment Flood Management Plans.Use of European Union (EU) funding streams, such as Intgerreg IIIB is recommended whereapplicable, to enable Local Authorities to undertake trans-national projects aimed atadvancing knowledge and good practice in flood risk management.

The “Making Space for Water: Programme of Work” was developed following consultationand will take account of any relevant recommendations that emerge from theindependent lessons learned review into the 2007 floods that affected many parts ofEngland. One of Defra’s and CLG’s early outputs from the Making Space for WaterProgramme was the publication, of PPS 25 in December 2006. This work, together with thePractice Guide forms the Governments required approach to managing and reducing floodrisk through the land use planning system.

A valuable piece of work looking at “Developing a Broader Portfolio of Options to DeliverFlooding and Coastal Solutions” has been carried out as part of this programme and will bevery useful to local authorities and other operating authorities, in their strategic planning offlood risk management. Outputs from this work are available from Defra.

Quarterly update reports are released providing details of progress made and keyachievements. These reports can be access via the Making Space for Water website athttp://www.defra.gov.uk/environ/fcd/policy/strategy.htm

2.2.3 The Pitt Review

The “Pitt Review” has been carried out following the severe floods of summer 2007 and is akey document for Local Authorities in their consideration of flood risk management. SirMichael Pitt was asked by ministers to conduct an independent review of events and reporton the lessons that should be learned.

The final report has published in June 2008 after 10 months of evidence collection andconsultation. This included examining over 1000 written statements submitted by victims ofthe floods, considering the experiences of other countries and visiting the communities ofthe affected areas.

The report presents a schedule of interim conclusions, many of which relate to localauthorities. These interim conclusions are intended to shape the National approach toflood management and can be accessed via the Defra website.

Pitt’s findings, conclusions and recommendations for action are challenging but will beextremely important in guiding local authorities and other operating authorities in theirconsideration of future flood risk management activities, including land use planning.

2.2.4 Catchment Flood Management Plans (CFMPs)

CFMPs are strategic plans produced by the Environment Agency in consultation with keypartners. They assess current flood risks from all forms of flooding across the wholecatchment and how those risks may change in the long-term (50 to 100 years). These plansconsider relevant multiple sustainability objectives, when exploring and appraising variouspotential policies for sustainable FRM. They then indicate appropriate FRM policies to helplocal authorities and other operating authorities to understand the scale and extent of



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current and future flooding problems from all sources; before taking key decisions on landuse, production of FRM strategies and plans, and investment in flood risk managementprojects or actions, to protect existing and future communities. Recognition of thesestrategic plans is very important to local authority planners when planning for the future andconsidering long term land use options for regeneration, inward investment and growth.

The CFMPs help to prioritise activities, focus resources where there is greatest need, anddetermine what flood risk management responses need to be considered further (andwhich responses will not be effective). The responses to flood risk will be broader than thosetraditionally used for flood defence to reflect the full range of management optionsavailable. CFMPs support an integrated approach to spatial planning and river basinmanagement, in line with the Water Framework Directive and the EU Directive on theassessment and management of flood risk; they cover all geographical areas in Englandand Wales and are crucial in the planning of sustainable flood risk management. CFMPscovering the Calder Valley are at the Draft Main Stage. these early documents containvaluable flood risk information and should be used by local authorities in their initial planningconsiderations.

2.3 Climate Change

Climate change impacts continue to provide an increasing challenge to sustainable floodrisk management for government and operating authorities. The severe floodingexperienced across the country in recent years and in particular during the summer 2007were, in the words of Sir Michael Pitt, “a wake up call”.

Flood risk related climate change issues are extremely important to the future managementof flood risk in the UK and beyond. These issues need to be taken seriously and mitigationand adaptation measures planned and adopted by Regional and Local Authorities.

Principle adverse flood risk effects of climate change threatening people and propertyinclude:

• More frequent and intense rainfall events causing flash flooding to low lying areas;

• More and faster surface water runoff and overland flows causing sewers, drains,rivers and streams to overflow;

• Increased sea level rise, storminess and frequency of storm surges threatening lowlying coastal communities; and

• Rising groundwater levels causing increased spring source activity and higher springflows increasing the risk of flooding.

If not addressed, these effects are likely to have a significant impact on many communitiesand in particular new developments in areas at high risk of flooding. Recent climatechange trends are contained within a UK Climate Impacts Programme document: TheClimate of the United Kingdom and Recent Trends published in December 2007 and isavailable on their website. The next UKCIP08 report containing further climate changescenarios and is planned for launch in late 2008.

In recognition of the Governments increasing concerns about the effects of climatechange on flood risk management, Defra produced a “Supplementary Note to OperatingAuthorities – Climate Change Impacts” in October 2006 in which they updated the climatechange policy for flood and coastal management. This document is available on the Defrawebsite. In conjunction with Defra, CLG then provided the recommended climate changecontingency allowances for sea level rise and precautionary sensitivity ranges for peakrainfall intensities and peak river flows etc. in Annex B of PPS 25. These figures should beused in all aspects of flood risk management including the consideration of newdevelopments and changes of land use in flood risk areas.



8

Yorkshire and Humber Region’s Climate Change Action Plan, was published in 2005 withYorkshire Forward, the Yorkshire and Humber Assembly and the Government Office forYorkshire and the Humber being key signatories to the plan. It identified a number ofactions for named partners such as Yorkshire Forward, the Assembly and the EnvironmentAgency to deliver. These organisations are currently progressing their actions. The Yorkshireand Humber Assembly’s thirteenth scrutiny review is considering how Yorkshire Forward isaddressing climate change and in February 2008, the Scrutiny Board identified three lines ofenquiry for the review: Climate Change Targets and Regional Performance, BalancingClimate Change Action and Economic Growth and Adapting to Climate Change. Thisaction plan and its review are likely to play an increasingly important role in the futuremanagement of flood risk as impacted upon by climate change.

In addition, Yorkshire and Humber Region’s proposed Single Integrated Regional Strategywill provide opportunities to bring together climate change adaptation through economicdevelopment, spatial planning, housing and transport.

2.4 Basic Elements of Flood Risk Assessment

Flooding can occur from many different and combined sources and in many differentways. Different types and forms of flooding present a range of different risks and the floodhazards of speed of inundation, depth and duration of flooding can vary greatly. SeeFigure 2-1 below.

With climate change, the frequency, pattern and severity of flooding are expected tochange and become more damaging.

Figure 2-1: Flooding From All Sources

Major causes of flooding are:

• Coastal flooding is caused by higher sea levels than normal resulting in the seaoverflowing onto the land;



9

• Inland flooding is caused by prolonged and/or intense rainfall resulting in excesswater flowing overland, ponding in natural hollows and low-lying areas or behindobstructions;

• River flooding occurs when the capacity of a watercourse is exceeded or a channelis blocked and excess water spills out from the channel onto adjacent low-lyingareas (the floodplain);

• Flooding from artificial drainage systems occurs when flow entering a system, such asan urban storm water drainage system, exceeds its discharge capacity, it becomesblocked or it cannot discharge due to a high water level in the receivingwatercourse;

• Groundwater flooding occurs when the level of water stored in the ground rises as aresult of prolonged rainfall to meet the ground surface and flow out over it;

• Estuarial flooding may occur due to a combination of tidal and fluvial flows, withtidal levels being dominant in most cases; and

• A less frequent form of flooding arises from the failure of infrastructure designed tostore or carry water (e.g., the breach of a dam, a leaking canal, or a burst watermain), or to protect an area against flooding (e.g., Breach of a flood defence,failure of a flap valve or pumping station or blockage of a pipe or culvert). Becauseof the sudden onset, the impacts of this form of flooding can be severe.

Prior to the major flood events in summer of 2007, non Main River flooding was based onanecdotal evidence or described with Critical Ordinary Watercourse (COW) investigationsundertaken by the Environment Agency. Little data could be abstracted from the watercompanies on sensitive drainage catchments where runoff impacts of new developmentcould be significant on combined sewer systems. However, a significant proportion ofrecent flood insurance claims are due to flooding from non main river sources, so this issuewill become larger with a more energised climate.

Historically the adopted approach in many SFRAs has been not to consider other sources offlooding as a spatial or strategic issue. Through good design and attenuation of drainageinputs to sensitive watercourses, mitigation was the accepted way forward.

Summer 2007 provided a stark reminder that the significance of capacity exceedance ofartificial and natural drainage systems can be severe for many communities. Therefore aclear reminder was provided that flooding from all sources should be scoped into a SFRA,and that new methods of rapid screening of these risks are required. The Pitt review into the2007 floods has recommended that the Environment Agency should proceed in developinga map of these sources and it is believed that this may be available as early as autumn2008.

In more recent SFRA updates JBA have utilised a screening technique based on theapplication of a blanket rainfall over a drainage area, and the simulation of its passagethrough the urban environment. This was developed from research for the Making Spacefor Water programme and the SFRA Actual Flood Risk Maps contained within this report area result from much of this work.

Increases in flooding impacting on people and property, due to development can becaused:

• Upstream by restricting the capacity and conveyance function of the watercourseand floodplain system;

• Downstream by decreasing the volume available for flood storage on thefloodplain, altering flow routes on the floodplain or by changes to the channelwhich can increase the flow discharged to downstream locations; and



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• By increasing run-off from reduced permeability surfaces, such as roads, roofs andcar parks.

2.4.1 Flooding Impacts on Property

Flooding impacts on property can cause severe damage. Flood water is likely to damageinternal finishes, contents, electrical and other services and possibly cause structuraldamage. The physical effects can have significant long-term impacts, with re-occupationsometimes not being possible for over a year. The costs of flooding are increasing, partlydue to increasing amounts of electrical and other sophisticated equipment withindevelopments. Sea-water flooding may cause additional damage due to corrosion.

Coastal erosion of both the foreshore and the shoreline itself can pose a direct threat to lifeand property as well as increasing the risk of flooding.

2.4.2 Flooding Impacts on People

Impacts on people can be severe. In small urban or steep upland catchments which havea very rapid response to rainfall, or with flooding due to infrastructure failure, flood waterscan rise very quickly and put life at risk. Even shallow water flowing at 2 metres/second canknock children and many adults off their feet and vehicles can be moved by water of300mm depth. The risks rise if the flood water is carrying debris. The impact on people as aresult of the stress and trauma of being flooded, or even of being under the threat offlooding, can be immense. This also extends to whole communities. Long-term impacts canarise due to chronic illnesses and stress. Flood water contaminated by sewage or otherpollutants (e.g. chemicals stored in garages or commercial properties) is particularly likelyto cause such illnesses, either directly as a result of contact with the polluted flood water orindirectly as a result of sediments left behind.

2.4.3 Flooding Impacts on the Environment

Environmental impacts can be significant and include soil erosion, bank erosion, land slidingand damage to vegetation as well as the impacts on water quality, habitats and flora andfauna caused by bacteria and other pollutants carried by floodwater.

Flood risk is generally accepted to be a combination of the likelihood of flooding and thepotential consequences arising. It is assessed using the source – pathway – receptor modelas shown in Figure 2-2 below. This is a standard environmental risk model common to manyhazards and should be starting point of any flood-risk assessment. However, it should beremembered that flood risk can occur from many different sources and pathways and notsimply those shown in the simple form below.

Figure 2-2: Source – Pathway – Receptor Model

The principal sources are rainfall or higher than normal sea levels, the principal pathwaysare rivers, drains, sewers, overland flow and river and coastal floodplains and their defenceassets and the receptors can include people, their property and the environment. All three

Pathway(e.g. defence)

Source(River or sea)

Receptor(e.g. people in the floodplain)

Pathway(e.g. defence)





Sewer flooding

Overlandflooding

Groundwater flooding



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elements must be present for flood risk to arise. Mitigation measures have little or no effecton sources of flooding but they can block or impede pathways or remove receptors. Theplanning process is primarily concerned with the location of receptors, taking appropriateaccount of potential sources and pathways that might put those receptors at risk.

It is important to define the components of flood risk in order to apply this guidance in aconsistent manner. Flood risk is a combination of the likelihood of flooding and thepotential consequences arising.

2.4.4 Likelihood

Likelihood of flooding is normally expressed as the percentage probability based on theaverage frequency measured or extrapolated from records over a large number of years.A 1% probability indicates the flood level that is expected to be exceeded on averageonce in 100 years, i.e. it has a 1 in 100 chance of occurring in any one year. Consideredover the lifetime of development, such an apparently low-frequency or rare flood has asignificant probability of occurring. For example a 1% flood has a 22% (1 in 5) chance ofoccurring at least once in a 25-year period (the period of a typical residential mortgage)and a 53% (1 in 2) chance of occurring in a 75-year period (a typical human lifetime).

2.4.5 Consequence

Consequences of flooding depend on the hazards caused by flooding (depth of water,speed of flow, rate of onset, duration, wave-action effects, water quality) and thevulnerability of receptors (type of development , nature, e.g. age-structure, of thepopulation, presence and reliability of mitigation measures etc).

Flood risk is then normally expresses in terms of the following relationship:

Flood risk = Probability of flooding x Consequences of flooding

Vulnerability of development to flooding depends on the nature of the development, itsoccupation and the construction methods used. A sheltered housing complex would bemore vulnerable than a retail unit. A broad classification of vulnerability is contained inTable D2 of PPS 25 and Appendix A: -of this report and a key objective of the spatialplanning process are to avoid flood risk to an inappropriate land use.

Transport and strategic utilities infrastructure can be particularly vulnerable to floodingbecause interruption of their function can have widespread effects well beyond the area offlooding. For example, flooding of primary roads or railways can deny access to areas forthe duration of the flooding, as well as causing damage to the road or railway. Flooding ofwater distribution infrastructure such as pumping stations or of electricity sub-stations canresult in loss of water or power over large areas. This can magnify the impact of floodingbeyond the immediate community and reinforces why decisions to locate development infloodplain should be taken very carefully.

Further consideration of flood risk is contained within Section 4 of this report.

2.5 Environment Agency FRM Plans, Strategies and Schemes

A number of Environment Agency flood risk management plans, strategies and assetimprovement schemes have been carried out over recent years and others are at theplanning stage. The latest headline information gathered on these initiatives can be foundin their relative CFMP showing the Environment Agency’s current Draft Long Term Plan. Thisplan includes the production of CFMPs and Strategies and delivering ImprovementSchemes to rivers and structures.

The River Calder, River Aire and River Don CFMPs are currently under development and areplanned for completion in September 2008. These plans will be a major element in



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delivering an integrated approach to flood risk. The CFMPs contain a significant amount offlood risk management data and information and are a valuable reference for LPAs. Theyare strategic planning tools to identify and agree policies for sustainable flood riskmanagement on a river catchment basis over a 50 to 100 year timeframe.

Strategies provide a more detailed understanding of flood process, appraisal of alternativemanagement measures and selection of preferences to deliver CFMP policies for specificareas within the catchment. However within the Calder, Aire and Don catchments severalstrategies have been completed prior to completion of the CFMPs. The strategiescompleted within Calderdale, Wakefield and Kirklees provided information on flood risk andstandard of protection aiding the production of this SFRA and associated maps.

The Government emphasises the need for early support of RSSs and LDFs. CFMPs should beused at an early stage to inform the formulation of policy options, including allocation ofland for development. CFMPs should also be used in SAs and SEAs to test and enhance therobustness of Spatial Strategies, Frameworks and Plans. Spatial planning documents shouldtherefore include aspects of CFMPs that may affect land use e.g. areas at high risk offlooding, where additional flood storage or flooding is necessary, or where changes in landmanagement are proposed.

Catchment boundaries often encompass many more than one planning district, therefore itis imperative that the planning process ensures that policies adapted within the currentplanning timeframe are consistent with the longer term vision for the wider catchment, andtake account of the impacts that decisions may have upon adjoining districts. In thisrespect the decision for the three councils to undertake a joint SFRA was a wise one andshould to some extent address this issue.

2.5.1 River Calder Catchment Flood Management Plan

There are three CFMPs which cover the districts within this SFRA. The Calder CFMPencompasses the majority of the area, influencing the main flood risk areas within theCalder SFRA. The River Calder CFMP commenced in May 2003. The CFMP is investigatingwhat factors influence flood risk at the catchment scale and will assess the impacts thatclimate change, land use change and urbanisation may have on flood risk over the next 50to 100 years. The CFMP will establish a policy framework for flood risk management acrossthe catchment through which future flood defence management strategies andprogrammes will be formulated.

The Calder CFMP is currently at Draft Main Stage, and flood risk management policies havebeen proposed for specific areas of the catchment (policy units). The CFMP is programmedfor completion in mid-late 2008 and is likely to be revised on a 5 yearly basis. The CFMP willinvolve a programme of consultation whereby stakeholders will be given the opportunity tocomment and input into the findings, catchment objectives and policies.

The Calder CFMP has been split into 8 policy units covering the LPAs of the Calder SFRA.Each Policy unit has a unique strategic vision towards managing flood risk and sets out anumber of draft actions, indicators and targets for the area identified in Figure 2-3.



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Figure 2-3: Calder CFMP Policy Units

Source: Calder CFMP (2008) Draft Main Stage Summary Report June 2008

Policy Units include:

1. Calder Headwaters – includes Walsden, Todmorden, Hebden Bridge andMytholmroyd

2. Ryburn & Hebble Brook – includes Sowerby Bridge and Halifax

3. Brighouse and Greetland

4. Colne, Holme and Fenay Beck – includes Huddersfield, and Colne, Holme andFenay Beck asset systems

5. Spen – includes Cleckheaton, Heckmondwike and Liversedge

6. Mid Calder – includes Mirfield, Dewsbury and Batley

7. Wakefield

8. Lower Calder

A number of the key draft policy actions for three main policy units are outlined below inTable 2-1.



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Table 2-1: Calder CFMP Draft Actions

Calder Headwaters Colne, Holme & Fenay Beck WakefieldLiaise with Calderdalecouncil to removepermitted developmentrights for Todmorden underarticle 4 of the GPDO

Ensure SoP is adequatethrough the completion of adetailed system assetmanagement plan

Continue improving the SoPby implementing theWakefield Phase ThreeScheme

Develop a sustainable landmanagement officer towork with landowners andEA partners to promotesustainable landmanagement in order toreduce risk of sheet runoffand sedimentation

Develop a sustainable landmanagement officer towork with landowners andEA partners to promotesustainable landmanagement in order toreduce risk of sheet runoffand sedimentation

Reduce to risk of floodingfrom Ings Beck, bydeveloping upstreamstorage, new flooddefences, raise existingdefences and improveculverts and debris screens

Produce soil managementplans for the policy unit

Produce a culvertmanagement planincluding location forremoval and improvements

Improve left hand bank ofthe Calder to protectresidential and commercialproperty

Improve flood warninguptake up throughout thepolicy unit

Develop a detailed focusedflood warning campaign

Develop a detailed focusedflood warning campaign

Carry out detailed analysisinto feasibility of providingfurther flood reduction toHebden Bridge

Ensure the condition ofdefences and structuresthroughout the policy unitdo not deteriorate

Carry out a Surface WaterManagement Planhighlighting issues regardingincapacity and aginginfrastructure.

Produce reservoirmanagement plans andensure issues are taken intoaccount in planningdocuments

Produce a detailed registerof

culverts including theirlocation, capacity andownership.

Install level and flowrecorders on Aire andCalder canal to enablemonitoring and forecastingof canal flooding

Source: Calder CFMP (2008) Draft Main Stage Summary Report June 2008Upper Calder Policy Unit includes: Walsden, Todmorden, Hebden Bridge and MytholmroydColne, Holme & Fenay Beck Policy Unit includes: Huddersfield, and Colne, Holme & Fenay Beck asset systems

Other Policy Units such as Ryburn and Hebble Brook and Brighouse the Environment Agencyis proposing to increase the standard of protection of a number of its defences. Otherareas such as Mid Calder, the Environment Agency are planning to ensure the condition ofdefence structures are adequate and sustainable, whilst in the Lower Calder they will belooking to reduce the current level of flood risk management and explore opportunities formanaging the existing washlands more effectively.

2.5.2 Upper Calder Improvements Strategy

The Environment Agency commissioned the Upper Calder Improvements Strategy in 2000and the first revision of the final strategy was completed in January 2001. The strategy hasbeen updated a number of times since then with the latest revision being completed in July2004.

The strategy involved a detailed investigation of flood risk across the main rivers andtributaries of the Calder catchment upstream of the River Colne confluence. Floodinghistory, catchment hydrology, existing defences, past studies and existing strategies fed into



15

an investigation of policy options and economic appraisal. This process delivered a numberof recommended flood defence schemes and other measures to manage flood risk. Flooddefence schemes are recommended at the following locations:

• Todmorden

• Brighouse

• Tenterfields

• Hollas Bridge

• Hebden Bridge

• Clifton Beck

• Sowerby Bridge

• Mytholmroyd

Other measures recommended include:

• Short term reinforcement of informal, non Agency owned/maintained defences(including filling of gaps in defences)

• Improved flood warning provisions

• Improved public awareness of the high flood risk experienced in the upper Calder

• En-maining of critical ordinary watercourses to strengthen the Agency’s regulatorypowers

• Adoption of sustainable urban drainage systems on all new and brownfielddevelopment

• Identification of sites susceptible to sediment deposition (shoal formation) andformalisation of sediment extraction programme

• Comprehensive inspection/survey of defences

• Assessment of contribution of sediment from Hebden Water and consideration to theconstruction of a boulder trap

The strategy is likely to be updated following the completion of the River Calder CFMP.

2.5.3 Wakefield Area Flood Defence Improvements Strategy

The Wakefield Area Flood Defence Improvements Strategy was first published in 1999 andupdated in March 2004. The strategy area extends from Dewsbury to Calder Bridge at BelleVue (eastern fringes of Wakefield).

The strategy considers three flood defence schemes. The first of these is the WakefieldScheme. Phase 1 of this scheme has been constructed and Phase 2 is ongoing. Thescheme comprises of storage upstream of Wakefield and containment works throughWakefield. The scheme is designed to deliver a 100 year standard of protection toWakefield.

The second is the Ings Beck Scheme which is currently in design. The preferred option asidentified in the feasibility study was storage upstream of Wakefield and containment andchannel improvement works in the urban areas. The scheme is being designed to provide a75 year standard of protection.

The third is the Horbury Scheme which is at feasibility study stage.



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2.5.4 Flood Defence Capital Improvements Strategy

The River Calder flood defence capital works programme has been developed largelybased on recommendations of the Upper Calder Improvements Strategy and the WakefieldArea Flood Defence Improvements Strategy. There is considerable uncertainty associatedwith the implementation of the programme as many of the schemes are at an early stageof investigation and funding for the schemes is not guaranteed.

The majority of the floodplain systems are partially defended and as such planningdecisions guided by the sequential test are taken ignoring the mitigation provided bycurrent or planned defences, particularly in the Upper Calder and Colne catchments.



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3 INTEGRATED FLOOD RISK WITH LOCAL AUTHORITY PLANNING

3.1 Introduction

The land use planning process is driven by a whole host of policy guidance on a national,regional and local level. Whilst the majority of these policies are not aimed at mitigatingflood risk, there are key links at strategic, tactical and operational levels between land useand spatial planning (Regional and Local Government), and FRM planning (EnvironmentAgency), which should be considered as part of a planned and integrated approach todelivering sustainable development. The sustainability appraisal will help draw togetherthese links and balance the application of wider social, economic and environmentalplanning policy and guidance. Flood risk assessment is required at all levels of the planningprocess and for all major developments in flood risk areas; these play and increasinglyimportant role in assisting effective delivery of key planning objectives.

3.2 Key Strategic Links between FRM and Planning

Making Space for Water recognises the importance of understanding current and futureflood risks, and their drivers, including the need for community growth, regeneration andinward investment to deliver sustainable development. Maximising flood risk managementopportunities presented by the land use planning system is essential to achieve thisobjective. However, this is best achieved as part of an integrated planning framework foroperating authorities to join forces and adopt a strategic approach as opposed tooperating in an uncoordinated way. This planning framework supports the implementationof statutory guidance from Defra and CLG to contribute towards sustainable development,and Government guidance on the management of environmental risks. This planningframework is shown below in Figure 3-1.

This section contains information and guidance on: Key links between FRM activities andthe wider planning system, current relevant National, Regional and Local planningpolicies, overview of PPS 25: Development and Flood Risk and the Practice Guide, andthe need for a balanced approach when considering flood risk alongside other keysustainable development factors.

Key messages:

• Flood risk is a material planning consideration and should be taken into accountearly, and at all stages of the planning process;

• Effective land use planning can avoid flood risk to people, property and theenvironment;

• The needs of flood risk management should be balanced with other social,economic and environmental sustainable development factors in deliveringsustainable development; and

• Impacts of climate change need to be planned for and adaptation measures



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Figure 3-1: Flood Risk in an Integrated Planning Framework

(Source: Environment Agency (2004) Catchment Flood Management Plans Volume 1 – Policy Guidance)

The primary reasons of the Environment Agency’s strategic assessment of food risk are toinform their own strategic planning for flood risk management and to inform and influencethe decisions and actions of other organisations and the public, in respect of flood riskreduction. Strong links between this process and the local authority planning process areessential.

SFRAs help provide this strong link and are an important vehicle to integrate flood riskmanagement planning, land use development planning and sustainability appraisals. Theyenable the consideration of key flood risk infrastructure and other flood risk investmentdecisions and delivery plans, to influence spatial planning considerations and vice-versa.This can be achieved at RSS, LDF/D and Planning Application scales and levels. The SFRAassists the land use spatial planning system to play its vital role in delivering sustainabledevelopment by taking full account of flood risk. Further information is available in the jointDefra and EA R&D Report FD2320 and this can be accessed via the Defra website.

A further key role for SFRAs has been suggested by Defra in their “Improving Surface WaterDrainage” consultation – February 2008, to identify critical drainage areas and inform the

National & European Legislation and Government Policy

Socio-economicSustainable Development

Sustainable Water ManagementSustainable Agriculture, Fisheries & Forestry etc

Natural EnvironmentHabitats Directive

Water Framework DirectiveFloods Directive

Climate Change etc

KEYPrimaryInfluence

SecondaryInfluence

DRIVERS

SOCIO-ECONOMIC & NATURAL ENVIRONMENT PLANNING(Taking into account natural coastal, fluvial and climate PROCESSES)

RURAL LANDMANAGEMENT

RuralDevelopment

Plans

Agriculture &ForestryPlanning

EnvironmentalStewardship

Schemes

LAND USE &SPATIAL

PLANNING(Regional & Local

Government)

RegionalSpatial

StrategiesRegional/Structure

Plans

LocalDevelopmentFrameworks

(LDPs in Wales)and associated

plans & guidance

FLOOD RISKMANAGEMENT

PLANNING (EnvironmentAgency)

Delivery PlansIncluding

Strategy Plansif & where appropriate

Projects &Actions

OTHER WATERMANAGEMENT

PLANNING(Environment Agency, Local

Authorities, Water Companiesand IDBs)

WATER RESOURCESPLANS (e.g. CAMS)

WATER UTILITY PLANS

LAND & URBANDRAINAGE PLANS

RIVER BASINMANAGEMENT PLANS

CFMPs

(& SMPs)

BIODIVERSITYACTION PLANS

NATIONAL FUNDING &STRATEGIC INVESTMENT

PROGRAMME

MAJOR INCIDENT PLANS(including flood response

and recovery plans)



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development of surface water management plans to help reduce risks from surface waterflooding in urban areas. Flood risk management is not an issue of infrastructure provision,but a constraint that needs a careful hierarchical approach to location, land use and finallymitigation. Further information of levels and content of FRAs is provided later in 4 and 7 ofthis report.

3.3 National Planning Policy

3.3.1 Development and Flood Risk

The introduction of PPG 25 in July 2001 reinforced the responsibility that Local PlanningAuthorities (LPAs) have to ensure that flood risk is understood and managed effectivelyusing a risk based approach as an integral part of the planning process. PPG 25represented a marked shift from the reactive resolution of flooding problems as a result ofdevelopment (i.e. flood defence) to the effective management of flood risk within theplanning system.

Notwithstanding this, it is widely recognised that flood risk is one of many of policyconstraints placed upon the local planning system. Development must facilitate the socio-economic needs of a community, and spatially must sit within an existing framework oflandscape and infrastructure. For this reason, a balance must be sought betweendevelopment need and the risk posed to existing and future development in an area andthis balance is further discussed in Section 3.6 later.

The role of the Environment Agency is to provide advice to LPAs to ensure the managementof flood risk in an effective manner as part of the planning process. The Government hasset an objective for the Environment Agency to reduce the risks to people and to thedeveloped and natural environment from flooding. In response to this the EnvironmentAgency has set a target to seek to influence planning activities to prevent 100% ofinappropriate development inside floodplains.

3.3.2 Planning Policy Statement 25: Development and Flood Risk

Whilst it is generally agreed that PPG 25 has worked well, and highlighted the importance offlood risk in the development process, it has been recognised that there is a need to focuson core policies that are clearer and easier to understand.

In December 2006 Planning Policy Statement 25 (PPS 25) was published, superseding PPG25. The new PPS 25 is accompanied by a Practice Guide, which was published in June2008.

The Government, through PPS 25, provides clarity on what is required at a regional andlocal level to ensure that appropriate and timely decisions are made to deliver sustainableplanning for development. The key planning objectives are as follows:

Regional planning bodies (RPBs) and local planning authorities (LPAs) should prepare andimplement planning strategies that help to deliver sustainable development by:

• Identifying land at risk and the degree of risk of flooding from river, sea and othersources in their areas;

• Preparing Regional or Strategic Flood Risk Assessments (RFRAs / SFRAs) asappropriate, as a freestanding assessment that contributes to the SustainabilityAppraisal of their plans;

• Framing policies for the location of development which avoid flood risk to peopleand property where possible, and manage any residual risk, taking account of theimpacts of climate change;



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• Only permitting development in areas of flood risk when there are no suitablealternative sites in areas of lower flood risk and the benefits of the developmentoutweigh the risks from flooding;

• Safeguarding land from development that is required for current and future floodmanagement e.g. conveyance and storage of flood water, and flood defences;

• Reducing flood risk to and from new development through location, layout anddesign, incorporating sustainable drainage systems (SUDS);

• Using opportunities offered by new development to reduce the cause and impactsof flooding e.g. surface water management plans; making the most of the benefitsof green infrastructure for flood storage, conveyance and SUDS; re-creatingfunctional floodplain; and setting back defences;

• Working effectively with the Environment Agency, other operating authorities andother stakeholders to ensure that best use is made of their expertise and informationso that plans are effective and decisions on planning applications can be deliveredexpeditiously; and

• Ensuring spatial planning supports flood risk management policies and plans, RiverBasin Management Plans and emergency planning.

• The Sequential Test remains a key part of PPS 25, which steers new development toareas at the lowest risk of flooding. This Test is intended to provide a rigorousunderstanding of flood risk within their area, delineating the extent and nature offlooding in accordance with the flood risk zones set out within PPS 25. This mustconsider the planning context and provide the framework for robust and sustainableflood risk management solutions within those areas where a balance is requiredbetween susceptibility to flooding and wider spatial planning pressures.

In addition, PPS 25 introduces the Exception Test which allows some scope for thosedevelopments at flood risk where it is necessary to meet the wider aims of sustainabledevelopment. When the use of the Exception Test is required, decision makers should applyit at the earliest stage in the preparation of all LDDs. All three elements of the Exception Testneed to be passed before development is permitted. The Sequential and Exception Testsare discussed further in Section 4 of this report.

PPS 25 clarifies that the potential impacts of climate change should be addressed in FloodRisk Assessments, and includes advice on current sources of information on climate changeincluding PPS Planning and Climate Change5 which is a supplementary document to PPS 1,to ensure that plans and planning decisions are fully informed about climate change.

PPS 25 introduces the proposal for the Town and Country Planning (Flooding) (England)Direction 2007 which came into force on 1 January 2007. This document makes theEnvironment Agency a Statutory Consultee on all applications for development in flood riskareas (except minor development), including those in areas with critical drainage problemsand for any development on land exceeding 1 hectare outside flood risk areas. TheDirection also introduces the requirement for LPAs to notify the Secretary of State wherethey are minded to approve a planning application contrary to a sustained objection bythe Environment Agency. PPS 25 also includes provision to extend the criteria used todetermine when the Environment Agency should be consulted on a planning application.

The Practice Guide to PPS 25 was published by the Department for Communities and LocalGovernment (CLG) in June 2008. It provides advice on the practical implementation of PPS25 policy and reflects extensive discussion with local authorities, the Environment Agencyand other key stakeholders and practitioners.

Local Authority planners and developers are advised to refer to and use PPS 25 and thepractice guide in conjunction with the further advice contained within this report.



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Catchment boundaries often encompass many more than one planning district, therefore,it is imperative that the planning process ensures that policies adopted within the currentplanning timeframe are consistent with the longer term vision for the wider catchment ascontained in the CFMP (discussed in Section 2.2 of this report), and take adequate accountof the impacts that the decisions made may have upon adjoining districts.

3.3.3 Other Planning Policy Statements

PPS 1 published in February 2005, sets out the overarching planning policies for the deliveryof sustainable development across the planning system and sets the tone for other planningpolicy statements. PPS 1 explicitly states that development plan policies should takeaccount of flooding, including flood risk. It proposes that new development in areas at riskfrom flooding should be avoided. Planning authorities are also advised to ensure thatdevelopments are “sustainable, durable and adaptable” including taking into accountnatural hazards such as flooding.

PPS 1 also places an emphasis on ‘spatial planning’ in contrast to the more rigid ‘land useplanning’ approach which it supersedes. Planning authorities will still produce site specificallocations and a proposals map as LDDs, but their Core Strategy will be more strategic andvisionary in content and will take into account the desirability of achieving integrated andmixed use development and will consider a broader range of community needs than in thepast. With regard to flood risk, it will be important for the Core Strategies andaccompanying Supplementary Planning Documents to recognise the contribution that non-structural measures can make to flood management.

Planning Policy Statement: Planning and Climate Change, a supplement to PPS 1, publishedin December 2007, sets out how the Government expects the planning system to addressclimate change. It explains that there is a compelling scientific consensus that humanactivity is changing the world’s climate. The evidence that climate change is happening,and that man-made emissions are its main cause, is strong. The Intergovernmental Panel onClimate Change highlights that we are already experiencing the effects of climate changeand if these changes deepen and intensify, as they are predicted to do without the rightresponses locally and globally, we will see even more extreme impacts.

One of the predicted impacts of climate change is more intense periods of rainfall andconsequent flooding. The PPS 1 supplement requires Regional Spatial Strategies and LocalDevelopment Frameworks to shape sustainable communities that are resilient to sucheffects. A key objective of the planning system being to secure new development andshape places that minimise vulnerability and provide resilience to climate change in waysthat are consistent with social cohesion and inclusion. Accordingly new developmentshould be planned to minimise future vulnerability in a changing climate. The SFRAincorporating Sequential and Exception Test information is essential in meeting theobjectives of the PPS 1 supplement Planning and Climate Change.

Whilst not directly relevant to the development of an SFRA, it is important to recognise thatthe exercise takes place within the context of other planning policy guidance andstatements, some of which also require sequential testing of site allocations anddevelopment proposals. PPS 3 (Housing), emerging PPS 4 (Planning for SustainableEconomic Development) and PPS 6 (Planning for Town Centres) are intrinsic within theplanning process and, therefore, an understanding of the constraints faced as a result ofthis additional policy guidance is required.

For example, whilst the PPS 3 Sequential Test recognises flood risk as a materialconsideration, its main emphasis is to seek the re-use of previously developed sites andempty or under-used buildings for housing. PPS 25 attempts to reconcile the emphasiswhich Government places on development of previously developed (brownfield) land forhousing with the reality that a significant proportion of this land is located alongside riversand vulnerable to flooding. Paragraph D14 of PPS 25 states:



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“Criterion b) of para. D9 (The Exceptions Test) reflects the Government’s commitment tomake the most efficient and effective use of land in line with the principles of sustainabledevelopment. Reflecting this, Planning Policy Statement 3 (PPS 3): Housing sets out theGovernment’s objectives for a flexible, responsive supply of land for housing which givespriority to the use of previously-developed land for development. However, flood risk shouldbe taken into account in determining the suitability of the land for development.”

It also recommends in Paragraph 52 that local authorities should consider combining theSequential Test for flood risk assessment with reviews of housing land allocations under PPS 3.There is some cause for concern as to whether challenging housing targets can be metwhen both these potentially conflicting Sequential Tests have been satisfied. One possiblesolution has been put forward by the Association of British Insurers:

“…when developing on higher-elevation greenfield sites… leaving an equivalent area oflow lying brownfield land for flood storage could be the most effective way to minimiseflood risk”.

This solution will require developers and urban designers to seek innovative design solutionsto accommodate the necessary levels of development, whilst ensuring practical andmanageable solutions are designed to address the issue of flood risk. Notwithstanding theabove, PPS 3 (November 2006) removes the requirement for sequential testing of housingsites and instead places emphasis on providing housing within sustainable locations and theeffective use of brownfield sites. PPS 3 identifies that in preparing Development PlanDocuments relating to housing, Local Planning Authorities should assess their potential andsuitability for development against the physical and environmental constraints ondevelopment of land, including, for example, the level of contamination, severity of floodrisk; taking into account that such risks may increase as a result of climate change.

In determining which sites to include as housing allocations, regard should also be made tothe sustainability appraisal of the site allocation. It is considered likely that all LocalAuthorities will include within their sustainability appraisal framework an element regardingpotential impacts on flood risk. This along with an SFRA document should help to inform theidentification of appropriate sites which are either not at risk of flooding or are consideredsustainable and can incorporate adequate mitigation measures.

3.4 Regional Planning Policy

3.4.1 Regional Spatial Strategy

The Government published The Yorkshire and Humber Plan - The Plan (The Regional SpatialStrategy) in May 2008. The Plan sets out the broad development strategy for the Region. Itcovers topics such as housing, economic development, transport, the environment andregeneration. Flood risk is referred to in the Core Area policies as well as many of the SubArea and Thematic or Specific Topic Based Area Policies. For example:

Policy ENV1: Development and flood risk, states:

• The Region will manage flood risk pro-actively by reducing the causes of flooding toexisting and future development, especially in tidal areas, and avoid development inhigh flood risk areas where possible.

• Allocation of areas for development will follow a sequential approach and will be inthe lowest risk sites appropriate for the development (identified by Strategic FloodRisk Assessments).

• Flood management will be required to:

1. Facilitate development in the cities of Leeds, Bradford, Sheffield, Hull and York,coastal towns including Bridlington, Grimsby, Scarborough, and Whitby, inlandurban areas including Doncaster, Goole, Halifax, Scunthorpe, Selby andWakefield where there is little development land available outside high flood



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risk zones, and land on the south bank of the Humber, provided the sequentialapproach has been used to inform decisions regarding flood risk`.

2. Protect parts of the strategic transport network, especially the Selby-Hull,Doncaster-York, and Doncaster- Immingham transport corridors.

3. Provide flood storage, habitat creation and managed realignment in areasaround the Humber, and other river corridors as required.

4. Provide positive land management for flood alleviation, particularly in theupland areas of the Yorkshire Dales, the North York Moors, the Howardian Hillsand the Pennines.

Policy YH1: Overall approach and key special priorities states:

• Avoid increasing flood risk, and manage land and river catchments for floodmitigation, renewable energy generation, biodiversity enhancement and increasetree cover.

Policy YH2: Climate change and resource use states:

Plan for the successful adaptation to the predicted impacts of climate change by:

• Minimise threats from and impacts of coastal erosion, increased flood risk, increasedstorminess, habitat disturbance, increased pressure on water resources, supply anddrainage systems.

Policy YH8: Green infrastructure states:

• Identify the functional role of green infrastructure in supporting the provision ofrenewable energy, urban micro climate control, and flood risk management

3.4.2 Single Integrated Regional Strategy for Yorkshire and Humber

The Government’s Sub-National Review of Economic Development and Regeneration (SNR)was published in summer 2007, and it identified a number of changes and newresponsibilities for the Regional Development Agencies (RDAs), namely planning, transportand housing. RDAs will be responsible for developing the Single integrated RegionalStrategy, and this document will bring together the climate change and other sustainabledevelopment elements of the current individual regional strategies for economicdevelopment, spatial planning, housing and transport.

It is clear that the SNR will fundamentally change the role and responsibilities of YorkshireForward and provide an opportunity to integrate housing and planning with economicdevelopment, and to achieve climate change mitigation and adaptation through spatialplanning and other measures. Innovative ways will be needed to influence the type ofbuildings and developments that are granted planning permission, where thedevelopments occur in the region, and how buildings and other infrastructure areconstructed.

3.5 Local Planning Policy

3.5.1 Local Development Frameworks

Under the terms of the Planning and Compulsory Purchase Act 2004 each council isrequired to prepare a LDF to replace its existing UDP. Amongst other things the LDF willprovide a policy framework for decisions about the use and development of land.

The government set a target for LDFs to begin to replace existing plans by March 2007. Ithas not been possible within this timescale to replace all current plans in their entiretyhowever; the legislation allows for existing plans to be "saved" in whole or part and



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incorporated into the LDF. The saved plans will be replaced later by additions to the LDFwhich will bring it up to date.

The commissioning of this SFRA has been timed to provide flood risk information to assist inthe allocation of sustainable development sites within and emerging LDFs.

3.5.2 Calderdale Metropolitan Borough Council

Background to UDP

Calderdale’s first UDP was developed in the early 1990’s and adopted in April 1997.Calderdale MBC commenced review of the UDP in 2000 and the First Deposit ReplacementUDP was opened for public review in November 2002. The Revised Deposit was opened forpublic review in March 2004. Pre-inquiry changes to the Draft Replacement UDP werepublished for six weeks of consultation November 2004. Objections to the UDP will be heardat Public Enquiry commencing 1 February 2005.

The replacement Calderdale UDP came into effect on 25 August 2006. It is now "saved"under the terms of the Planning & Compulsory Purchase Act 2004 until 24 August 2009(unless a Direction is issued by the Secretary of State indicating which Policies are saved fora further period). Development of documents within the LDF are now underway with keymilestones such as public participation on preferred options and submission to Secretary ofState planned leading to adoption and publication of the Core Strategy in 2010 and LandAllocations and Designations in 2012. Given the recent UDP review, the LDF is likely to drawheavily on the revised UDP.

Framework for Flood Risk Management

The replacement Calderdale UDP provides extensive “saved” policies regardingmanagement of flood risk. These include:

• EP15 Development alongside Waterways;

• EP16 Protection of Washland and Functional Floodplain;

• EP17 Protection of Indicative Floodplain;

• EP18 Development behind Flood Defences;

• EP19 Development outside Floodplains;

• EP20 Protection from Flood Risk;

• EP21 Developments Involving Watercourse Improvements;

• EP22 Sustainable Drainage Systems; and

• EP23 Culverting of Watercourses

The replacement UPD should be referred to in detail to gain information on the exactwording of flood risk related policies.

3.5.3 Kirklees Metropolitan Borough Council

Background to UDP

The Kirklees UDP was adopted on 1 March 1999. At the time of adoption it was envisagedthat the strategic guidance would remain valid at least until there has been significantrevision of the guidance whilst in terms of land supply the plan covers the period 1 April 1993to 1 April 2006. In early 2007, a policy saving exercise, examined whether UDP policiesshould be saved or not saved. The council submitted a schedule of all UDP policies to theSecretary of State on 29 March 2007 indicating with reasons which policies it wished to saveand those which it did not consider should be saved. The Secretary of State issued a



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direction on 17 September 2007 specifying which policies were saved. Formulation of theLDF is underway.


Since the UDP was developed and adopted considerable guidance on managing flood riskin relation to development has been provided by various levels of government. Policy setout in the UDP could not draw on this guidance and was consequently brief.

The Kirklees UDP Policy EP3 establishes that:

“Development will not be permitted within designated washland … except where:

a) it would not significantly affect the function of the washland or it incorporatesadequate alternative floodwater storage capacity

b) there would be no serious risk to the development from flood debris or pollution”

In addition Policy EP3A states:

“Culverting or canalisation of watercourses within or related to development sites will notnormally be permitted, unless there are public safety considerations. In appropriatelocations development proposals should incorporate reopening of culverts and restorationof canalised watercourses to a more natural state.”

The new LDF will be able to draw on the wealth of policy guidance provided in PPS 25 andthe Practice Guide along with the contents of this SFRA and will contain further moredetailed provisions regarding development and flood risk issues.

3.5.4 Wakefield Metropolitan District Council

Background to UDP

The original Wakefield UDP was adopted in 1994. In February 1998 approval was given forthe Wakefield UDP Review to roll the existing Plan for Wakefield forward to 2006. The Reviewconsists of a limited series of alterations to the original adopted plan, considered necessaryin the light of current Government guidance. The UDP First Alteration was formerly adoptedin January 2003.

Similar to Kirklees, Wakefield MDC has “saved polices” under its UDP and has commencedthe formulation of its LDF. Once again the SFRA provides an ideal opportunity to guideWakefield MDC in the selection of sustainable development sites and formulation ofeffective flood risk management policy.


The Wakefield UDP policy in relation to flood risk is covered in the environmental impactpolicy E44. The council’s philosophy is further endorsed with reference to land drainage,policy E65 and the protection of Washlands, policy OL6.

Wakefield UDP Policy E44 on flood risk:

“Development which would be at risk from flooding or which would give rise to floodingproblems for any proposed or existing properties will not normally be permitted”

Wakefield UDP Policy E65 on land drainage:

“Development will only be permitted where the council is satisfied that suitable measuresdesigned to mitigate any adverse effects of surface water run-off are included as anintegral part of the development. Wherever possible the council will support the use ofsustainable urban drainage measures to achieve more sustainable management of surfacewater run-off.”



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Justification and further advice is provided on the Councils flood risk and land drainagepolicy in paragraphs 3.7.16 to 3.7.18 of the Wakefield UDP.

“The Council seeks to preclude development which would be at risk from flooding or wouldcreate additional flooding problems. The Environment Agency have produced IndicativeFloodplain Maps showing areas at risk from flooding. Planning applications fordevelopment of sites over 0.4 hectares and development sites identified in the UDP willrequire a surface water catchment survey to be undertaken, which may identify the needfor substantial flow balancing and off-site watercourse improvement works. Fordevelopment to be acceptable, the Council must be satisfied that water courses on andoff a development site are adequate to meet additional flows, or will be improved to anappropriate standard. Applications for development must provide sufficient details for suchan assessment to be carried out prior to determination. The Council will expect sustainableenvironmental solutions and will consult with the Environment Agency on these matterswhere appropriate. This general requirement is in addition to the washlands protectionpolicy OL6”

“The traditional practice for the disposal of surface water is to pipe it away to the nearestwatercourse in order to ensure rapid run-off. This can lead to an increased risk of flooding,aquifers not being recharged, reduced retention of water in the subsoil, and increasing therisk of transmission of pollutants to watercourses. In order to achieve a sustainable methodof discharge of surface water, sustainable urban drainage methods should be employed.”

“A range of sustainable urban drainage techniques are available to tackle flooding,pollution and other problems generated by conventional piped solutions. An importantelement in these techniques is "source control", which is the practise of controlling run-off asclose to its origin as possible. Sustainable urban drainage techniques include use ofsoakaways, permeable paved surfaces, swales, reed beds, detention and retention ponds.Some techniques also offer other benefits, ponds and reed beds for example, offeropportunities for environmental and landscape enhancement improving biodiversity andlocal amenity. Even where sustainable urban drainage techniques alone cannot providetotal surface water drainage solutions, they can be beneficially used in conjunction withconventional piped systems.”

Wakefield UDP Policy OL6 on washland:

“Development will not normally be permitted in designated washlands except where:

a) the proposed development would not significantly affect the function of thewashlands

b) there would be no serious risk to the development from flood debris or pollution”

Designated washlands are shown on maps accompanying the UDP. Further adviceregarding washlands is provided in paragraphs 10.5.43 and 10.5.44 of the Wakefield UDP.

“Policy OL6 provides the greater protection from development considered necessary forthese important areas. However, it does not preclude all development and uses which areenvisaged as being acceptable. These include playing fields, agriculture use, open space,allotments etc. The appropriate use will depend on frequency of flooding, anddevelopment proposals will be the subject of consultations with the Environment Agency.”

“There are many other areas of land in the District that are subject to flooding on whichdevelopment maybe possible subject to appropriate compensatory works and/or floodprotection. The washland areas designated on the proposal maps are the most importantareas that must be protected from inappropriate development.”

3.6 Balanced and Sustainable Approach

The Yorkshire and Humber Plan – Spatial Vision, presents a Regional SustainableDevelopment Framework (RSDF) in which the Regional Economic, Spatial, Housing and



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Cultural Strategies inextricably link and guide the development of local strategies andprogrammes such as LDFs, Sub-Regional Investment Plans and LSP/Community Plans. TheRegional Development Agency and the Regional Housing Board have prepared theirstrategies based on the RSDF.

The Region is experiencing a growth in the number of households, greater than seen in theprevious 10-15 years and there is a need to provide sufficient homes to house the additionalhouseholds expected to form across the Region. There is also a need to manage therelease of housing land to support housing market re-structuring in low demand areas andincrease the provision of affordable housing, particularly in areas of high need. With regardto economic development, sites are needed to ensure that a package and new homesand jobs are provided.

This need for growth and economic development presents both opportunities andchallenges for flood risk management. The Regional target for the proportion of housingdevelopment taking place on previously used land is 65% and inevitably many of theseareas are subject to flood risk. The LPA should provide appropriate weight to flood riskalongside other sustainable development factors and where for wider sustainabledevelopment reasons, development proceeds in high flood risk areas, PPS 25 requires thatnew development should be made safe and not increase flood risk elsewhere.

Having regard to the vulnerability of the site (e.g. residential use, offices, manufacturingetc.) and the nature of the flood hazard (e.g. slow/fast flowing and/or shallow/deep floodwater etc.), and with careful planning, appropriate design and layout; developments canmeet these requirements. Site use, topography, flood levels, flood defences, floor levelsand various mitigation measures are key factors that should be brought together in theflood risk assessment to determine the appropriateness of the development.

Balancing and appropriately weighing key sustainable development factors including floodrisk can deliver sustainable growth whist reducing overall flood risks to people and property.Further guidance on flood risk avoidance, substitution and mitigation and the Sequentialand Exception Tests required by PPS 25 is provided in Section 4 of this report.



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4 RISK BASED SEQUENTIAL APPROACH

4.1 Introduction

The SFRA is a planning tool that is used to inform the spatial planning and developmentmanagement process. It helps to ensure new development is appropriate where this takesplace in areas at risk of flooding, and that developments are sustainable. Due to the needfor growth, regeneration and inward investment, suitable development land has to beidentified and it’s land use changed where necessary, in order to meet this demand.

Flooding is a natural process and does not respect political demarcations or administrativeboundaries; it is influenced principally by natural elements of rainfall, tides, geology,topography, rivers and streams and man made interventions such as flood defences, roads,buildings, sewers and other infrastructure. As was seen in the summer 2007 floods, floodingcan cause massive disruption to communities, damage to property and possessions andeven loss of life. For this reason it is very important to try and avoid developing in flood riskareas in the first instance. Where this is not possible then the vulnerability of the proposedland use to flooding should be considered and measures taken to minimise flood risk topeople, property and the environment. This is the thrust of the risk based sequentialapproach to managing flood risk and it is the backbone of PPS 25. This approach isexplored further and explained below.

4.2 Summary of the Risk Based Sequential Approach

The sequential approach to flood risk is all embracing and should be adopted at theearliest opportunity, and at all levels of the planning process. Flooding from all sourcesshould be considered and it is helpful to break flood risk down into the basic components ofsource, pathway and receptor as described earlier in Section 2.4.

The risk based sequential approach requires;

• Strategic avoidance of increasing flood risk from all sources;

This section contains information and guidance on: the risk based approach, levels offlood risk assessment, delineation of flood risk zones, flood risk vulnerability classifications,principles of the sequential and exception tests, management decisions and actionsand flood risk indicators and balance sheet.

Key messages:

• Locate development to avoid flood risk wherever possible;

• Opportunities for management actions to avoid, substitute and/or mitigate floodrisk can be taken at all levels of the planning process and for all developmenttypes in all locations;

• Only on completion of the Sequential Test should the Exception Test be used tojustify allocations or developments in high risk areas. However the Exceptions Testmust not be used as a tool to place inappropriate development in high risk areas;

• Use a risk based sequential approach in all decision making to minimise flood risk;and



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• Managing flood pathways to reduce the likelihood of flooding; and

• Reducing the adverse consequences of flooding to receptors by avoidinginappropriate development.

Key elements of this approach are:

• Management actions taken at all levels of the planning process for all land uses in alllocations;

• Identification of designated flood zones;

• Vulnerability classifications for certain land uses;

• Appropriate flood risk assessment at regional, strategic and site levels;

• Sequential consideration of first avoiding, then substituting and then mitigating floodrisk. This applies throughout the whole risk based approach, at all levels and stagesof planning and for all land uses and sizes of development;

• Sequential Test to seek compatibility between proposed land use and then it’svulnerability to flooding; and

• Exception Test where necessary;

To be able to deliver the sequential approach, many flood risk factors need to be broughttogether in an appropriate FRA as detailed later in this Section. Figure 4-1 below shows thekey elements of the approach.

Figure 4-1: Overview of Risk Based Sequential Approach

Management Decisions and Actions to Avoid > Substitute > Mitigate (always in mind)

Management Decisions and Actions to Avoid > Substitute > Mitigate (always in mind)

Compatibility of land use with flood zones (always in mind)

Compatibility of land use with flood zones (always in mind)

Flood Risk Information (source, pathway & receptor – floodingfrom all sources – data & maps)

Sequential Test (compatibility of flood zones with land usevulnerability classification – prioritisation ofsites)

Exception Test (wider sustainable benefit – previouslydeveloped land or no reasonable alternative– remains safe)

Land Use PlanningRSS, LDF, LDD and Planning Application



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Working through Figure 4-1 above it can be seen that management actions to avoid,substitute and/or mitigate flood risk along with the need to do all that is possible to ensurecompatibility of land use with PPS 25 flood zones, embrace the approach. It is usually thecase that opportunities to enable some avoidance, substitution and mitigation of flood riskcan be created at many, if not all stages of the process and these opportunities should betaken. Once an appropriate SFRA has been completed this allows the important stages ofthe Sequential Test, and where necessary the Exception Test to be carried out. TheSequential Test is used to prioritise sites in order of probability to flooding and theiracceptability in terms of development and the Exception Test ensures the development issustainable and remains safe. Appropriate policies, allocations and conditions etc. canthen be used in the planning process to secure appropriate and sustainable development.More information on all these key elements now follows.

4.3 Levels of Flood Risk Assessment

Within the hierarchy of regional, strategic and site-specific flood-risk assessments, a tieredapproach ensures that the level of information is appropriate to the scale and nature of theflood-risk issues and the location and type of development proposed, avoiding expensiveflood modelling and development of mitigation measures where it is not necessary. Asstated in PPS 25 the three principle levels of assessment comprise:

• Regional Flood Risk Appraisal (RFRA) – a broad overview of flood risk issues across aregion to influence spatial allocations for growth in housing and employment as wellas to identify where flood risk management measures may be required at a regionallevel to support the proposed growth;

• Strategic Flood Risk Assessment (SFRA) – an assessment of all types of flood riskinforming land use planning decisions. This will enable the LPA to apply theSequential Test in PPS 25 and allocate appropriate sites for development, whilstidentifying opportunities for reducing flood risk; and

• Site Specific Flood Risk Assessment (FRA) – site or project specific flood riskassessment to consider all types of flood risk associated with the site and proposeappropriate site management and mitigation measures to reduce flood risk to andfrom the site to an acceptable level.

In a plan-led system, implementation of the sequential risk-based approach requires thatforward planning policy decisions in RSSs and LDF/LDDs are guided by information on floodrisk to ensure that allocating inappropriate development does not unnecessarily raiseexpectations of landowners and developers. This should be achieved through the use ofRFRAs and SFRAs, which are generally broad-brush assessments of the risk of flooding, toguide strategic planning decisions. They involve the collection and collation of data onflooding and flood-risk management from all available sources to provide information to thenecessary level of detail to allow decision-makers to:

• Prepare appropriate policies for flood-risk management within RSSs and LDFs;

• Produce a strategic understanding of the scale, extent and nature of the flood risk ata community level and how that would alter with any proposed development;

• Apply a risk-based, sequential approach, providing risk data to inform the ExceptionTest and to confirm the compatibility between the flood risk vulnerability of theproposed allocation and the Flood Zone;

• Inform the strategic environmental assessment of RSSs and LDFs;

• Translate the national guidance into locally specific guidance, including theidentification of areas of floodplain that should be safeguarded for floodmanagement purposes



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• Identify the level of detail required for site-specific flood-risk assessments in particularlocations; and

• Determine the acceptability of flood risk in relation to emergency planningcapability and how the existing and proposed community would respond to a floodevent.

4.4 Delineation of Flood Zones

4.4.1 Environment Agency Flood Maps

These provide an overview of areas considered susceptible to flood risk in the study area asa result of fluvial and tidal flooding. These maps have been prepared in a consistentmanner across England and Wales and provide an estimation of the extent of flooding forboth the 1% and 0.1% events.

PPS 25 divides the country into three basic flood zones, Flood Zones 1, 2 and 3,corresponding to areas of low, medium and high flood risk, respectively. The flood zonesare based on the Environment Agency’s Flood Maps. Therefore they refer to the probabilityof flooding from rivers, the sea and tidal sources (where appropriate) and ignore thepresence of existing defences, because these can be breached, overtopped and may notbe in existence for the lifetime of the development. They do not consider other forms offlooding and do not take account of climate change.

4.4.2 Delineation of Low Risk Zone 1

PPS 25 considers areas within Flood Zone 1 to be at low risk to flooding. The annualprobability of flooding within this zone is less than 0.1% or can be easily defined as areaswithin the District/Borough Council area located outside either Flood Zone 2 or 3.

Generally there is no constraint to development, in terms of flood risk, within Flood Zone 1although, It will be necessary for all developments proposals to be accompanied by a sitespecific Screening Study (as per PPS25 Practice Guide Level 1 FRA). Localised drainagearrangements should be discussed and consideration of drainage needs to ensure thatdevelopment will be safe and there will be no increase in flood risk elsewhere. In line withEnvironment Agency Standing Advice any development over 1ha should be accompaniedby a full Flood Risk Assessment.

4.4.3 Delineation of Medium Risk Zone 2

PPS 25 considers areas within Flood Zone 2 to be at medium risk of flooding. The annualprobability of fluvial flooding within this zone is between 0.1% and 1% (or between 0.5% and0.1% for tidal flooding). In general, Flood Zone 2 is considered suitable for mostdevelopment once the Sequential Test has been carried out, except highly vulnerable landuses where the Exception Test is required, such as police stations, fire stations andambulance stations.

However a risk-based assessment of allocations within Zone 2 must be undertaken.Although more vulnerable land uses such as hospitals, residential institutions and residentialdevelopment are permitted in Flood Zone 2, it will be extremely important that detailedFlood Risk Assessments are carried out. These will need to clearly quantify actual flood risk,show that there is safe access and egress and show that any residual risk can be safelymanaged, especially when development is in the form of hospitals. Consideration of localdrainage issues will also be required.

4.4.4 Delineation of High Risk Zone 3

PPS 25 considers areas within Flood Zone 3 to be at high risk of flooding. PPS 25 defines HighRisk Flood Zone 3 as two sub-zones 3a and 3b, which correspond to high probability floodingand the functional floodplain.



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• Flood Zone 3a: High Probability

In accordance with Table D.1 of PPS 25 “This zone comprises land assessed as havingbetween a 1% and 0.1% annual probability of flooding or between a 0.5% and 0.1%annual probability of sea flooding in any year.”

• Flood Zone 3b: The Functional Floodplain

In accordance with Table D.1 of PPS 25 “This zone comprises land where water has toflow or be stored in times of flood”

4.4.5 Delineation of the Functional Floodplain

PPS 25 considers the functional floodplain as areas compromising land within Flood Zone 3where water has to flow or be stored in times of flooding, and SFRAs are tasked with theresponsibility of identifying this Flood Zone, known as 3b.

PPS 25 suggests the 5% annual probability flood event for the baseline of a functionalfloodplain however; a larger probability can be used where appropriate, depending oncatchment characteristics and on agreement between the LPA and the EnvironmentAgency.

SFRAs also have the ability to identify where it might be appropriate to extend the 5% (orhigher) flood outline to areas within Flood Zone 2 and 3 to restore or expand the functionalfloodplain. The ability to identify and safeguard large enough areas againstredevelopment and development in both urban and rural areas, means that existing openspace can potentially be used for flood storage, effectively reducing flood risk downstream.This process assists Flood Zone 3 policy aims, identified in table D.1 in PPS 25, which include:

1. “Reduce the overall level of flood risk in the area through the layout and form or thedevelopment and the appropriate application of sustainable drainage systems,”

2. “Create space for flooding to occur by restoring functional floodplain and floodflow pathways and by identifying, allocation and safeguarding open space forflood storage.”

In many cases the extent of natural floodplain brought into use during a 5% annualprobability flood event is very similar to that used in a 1% event. Differences observed andrecorded are usually in terms of increased depth and speed of flow and this is dependenton the topography and shape of land on which water flows in the Calder Valley.

Acknowledging these specific topographical characterisations of the Calder Valley and inrecognition of PPS 25, the 1% flood extent, in the first instance, has been used and isconsidered the Functional Floodplain.

Flood management in the Calder Valley is reliant on designated washlands. These largeareas on the Calder floodplain upstream and downstream of major urban areas are usedto store water in times of flood and to offset a number of flood defence schemes. Thesedesignated washlands are also included within the functional floodplain.

In keeping with the recommendations of PPS 25 areas already benefiting from defences orthose which are developed and/or sustainable have not been considered as FunctionalFloodplain. Major transport infrastructure e.g. motorways and railways have also beenexcluded from functional floodplain areas, as well as the removal of ‘dry islands’ definedusing the ‘size standards’ within the Environment Agency SFRM Specification for Flood RiskMapping6. It has been acknowledged that there are some inaccuracies on minorwatercourses, in particular non-main rivers due to scale and misalignment issues. Thereforeas it is critical that the outline for the functional floodplain is as accurate as possible, non-main rivers have been excluded. Therefore it is important these areas are assessed in moredetail at a site-specific FRA level or during any subsequent Surface Water managementPlan.



33

There are also a number of sewage treatment plants within Calderdale, Kirklees andWakefield that are at high risk of flooding. It is recommended that infrastructure associatedwith Sewage Treatment Works will be permitted on these sites, but if the Sewage TreatmentWorks becomes redundant the land shall revert back to functional floodplain.

As the designation of Flood Zone 3b within the SFRA will dramatically affect the futuredevelopment potential of the areas concerned it is important that the extent is examined insome detail by the Local Planning Authority by both planners and drainage engineers.

All councils have accepted the outline and have written to confirm their acceptance to theEnvironment Agency stating they are satisfied with the extent of the functional floodplain.Copies of the confirmation letters are provided in Appendix C: - Further information on floodrisk zones is contained in Appendix A: - of this report.

The SFRA should be fully integrated with CFMPs and other Strategies that show, atcatchment scale, the need to protect the floodplain and avoid inappropriatedevelopment in high flood risk areas.

4.5 Application of the Sequential Test

The SFRA provides a framework to undertake both the Sequential and Exception Tests aspart of the sequential approach. The PPS 25 Sequential Test “sieving” process focuses onconsidering flood risk, and if required, its mitigation through each tier. The process caninvolve creating long lists of ‘reasonably available land’ and then comparing all of thesesites to flood maps in the SFRA, and explaining in detail why certain areas in theDistrict/Borough can or cannot be appropriately developed. Under PPS 25, followingapplication of the sequential test, it is not possible, consistent with wider sustainabilityobjectives, for the development to be located in zones of lower probability of flooding; theException Test can be applied. The principle of the sequential test sieving processembracing the Sequential and Exception Tests is shown in Figure 4-2 below.

The Sequential Test sieving process comprises seven key stages, designed to “sieve out” thedevelopment allocations at an early stage that may be considered inappropriate inaccordance with PPS 25 and where the Exception Test is required are unlikely to meet theflood risk management requirements. A key element of the sieving process is to minimisethe number of development proposals needing to be subjected to the Exception Test andthen to estimate the likely outcome of those that do. This is to do all that is possible at theSFRA stage to ensure cost effective use of time and resources and to avoid inappropriatedevelopment in flood risk areas in accordance with PPS 25. As previously shown in Figure4-1, this is achieved using a hierarchical approach to risk management, by first avoiding therisk wherever possible, then if this cannot be done, substituting it for a less vulnerable landuse and then finally incorporate mitigation measures to reduce flood risk to people andproperty both on the site and elsewhere.

Having completed the Sequential Test the Exception Test aims to provide a method ofmanaging flood risk whilst still allowing necessary development to occur in the interests ofsustainable development.



34

Figure 4-2: Sequential Test Sieving Process



35

4.6 Flood Risk Vulnerability Classification

Flood risk vulnerability classifications are provided in Table D.2 of PPS 25 and Appendix A: -of his report. These provide recognition that not all land uses have the same vulnerability toflooding. Some land uses such as residential developments are more vulnerable to thepotential loss of life and damage to personal property and possessions than say shops andoffices. Five flood risk vulnerability classifications are contained in PPS 25 and these are:

• Essential infrastructure

• Highly vulnerable

• More vulnerable

• Less vulnerable

• Water compatible development.

4.6.1 Flood Zone 1 – Low Probability

From a flood risk perspective all land uses are acceptable within Flood Zone 1. Flood risk isnot considered to be a significant constraint to development and all land uses listed beloware appropriate in this zone


• Highly vulnerable

• More vulnerable

• Less vulnerable


A Screening Study, as per PPS25 Practice Guide, will be required for development in thiszone – this will determine whether further assessment of flood risk is required. This will takeaccount of historical flood records of localised flooding, site specific considerations and thesurface water proposals for the development, including mitigation.

However, due to their potential impact on the local flood risk, a full Flood Risk Assessmentwill be required for all developments greater than 1ha in size. This will include furtherconsideration of surface water drainage and onsite mitigation measures that may berequired, particularly where the capacity of the surface water sewer or receivingwatercourse is limited. This assessment will be undertaken by the developer of the site andshould be appropriate to the scale, nature and location of the development. The Council’sDrainage Engineers and the Environment Agency will be able to advise potentialdevelopers as to their specific requirements on a site by site basis.

4.6.2 Flood Zone 2 – Medium Probability

Subject to the application of the Sequential Flood Risk Test, PPS 25 specifies suitable types ofdevelopment in Flood Zone 2 as:


• More vulnerable

• Less vulnerable




36

Highly vulnerable uses should only be permitted in this zone if the Exception Test is passed.The SFRA is unable to assess whether the site will pass parts a. and b. of the Exception Test.However, the council must be able to demonstrate the need for development through thespatial planning process.

A Flood Risk Assessment will be required for all development in this zone. The Flood RiskAssessment will need to assess the current level of flood risk as well as the level of flood riskfollowing development. Development plans for the site will need to demonstrate that floodrisk can be effectively and safely managed without increasing flood risk elsewhere.

Proposals will also need to demonstrate that access and egress to the development can bemaintained during an extreme flood event and that development is set at an appropriatelevel. A further level of analysis may be required where development is planned behind oradjacent to existing defences in order to test the sustainability and robustness of themitigation measures. In keeping with Flood Zone 1 other flood risk constraints, such asincidents of localised flooding and other site specific considerations will need to beaddressed. Again, detailed FRAs will be undertaken by the developer of the site and theEnvironment Agency will be able to advise potential developers as to their specificrequirements on a site by site basis. The Flood Risk Assessment will need to address part c. ofthe Exceptions Test and should only be commenced when the planning justification isclearly established.

4.6.3 Flood Zone 3 – High Probability

A Sequential Flood Risk Test is used to prioritise sites in order of vulnerability to flood risk andtheir acceptability for development. Developers should primarily focus on lower FloodZones in preference to Flood Zone 3. Any proposals for development within Flood Zone 3will require developers to undertake a detailed Flood Risk Assessment. It should be notedthat constraints to development are likely to be significant and developers should seekadvice from the Councils and the Environment Agency as to the specific requirements forassessment.

Flood Zone 3 is subdivided into Zones 3a and 3b. Flood Zone 3b is the portion of floodplainthat provides natural and/or managed attenuation. It can be all or part of the flow areaand owing to the frequency of inundation, Zone 3b areas are considered to be FunctionalFloodplain. Urban areas are generally considered to be Zone 3a, so for the purpose of thisSFRA, brownfield sites will be assumed Zone 3a.

Zone 3a is potentially suitable for water compatible and less vulnerable land uses. The morevulnerable and essential infrastructure uses should only be permitted in this zone if theException Test is passed. Highly vulnerable development should not be permitted in thiszone.

In Zone 3b, only essential infrastructure (subject to exception testing) and water-compatibleuses may be permitted.

Where sites are partially located within Flood Zone 3b, it is recommended that Councilsshould avoid development by specifying water compatible uses or Public Open Space forthese areas.

Land use vulnerability classifications and flood zones are carried forward into Table D.3 forapplication of the Exception Test.

4.7 Application of the Exceptions Test

Once the Sequential Test has been carried out and where new development isexceptionally necessary within areas at risk of flooding, Government policy aims to make itsafe without increasing flood risk elsewhere and where possible reducing overall flood risk.This is in accordance with paragraph 19 of PPS 25, which states:



37

“The Exception Test is only appropriate for use when there are large areas in Flood Zones 2and 3, where the Sequential Test alone cannot deliver acceptable sites, but where somecontinuing development is necessary for wider sustainable development reasons, takinginto account the need to avoid social or economical blight and the need for essential civilinfrastructure to remain operational during floods…”

PPS 25 explains where and for what type of development the Exception Test needs to beapplied. In some situations, for certain types of development, it is not appropriate to usethe Exception Test to justify development. For example, highly vulnerable developmentcannot be justified within the high risk zone through the use of the Exception Test. Figure 4-3below shows flood risk vulnerability and flood zone compatibility and indicates situationswhere it is necessary and appropriate to apply the Exception Test.

Figure 4-3: Where the Exception Test Applies

There are three stringent conditions, all of which must be fulfilled before the Exception Testcan be passed. These conditions (see paragraph D9 of PPS 25) are as follows:

a) It must be demonstrated that the development provides wider sustainability benefitsto the community that outweigh flood risk, informed by a SFRA where one has beenprepared. If the LDD has reached the ‘submission’ stage (see Figure 4.1 of PPS 12:Local Development Frameworks) the benefits of the development should contributeto the Core Strategy’s Sustainability Appraisal (SA);

b) The development must be on developable previously-developed land or, if it is noton previously-developed land, that there are no reasonable alternative sites ondevelopable previously-developed land; and



38

c) A site-specific Flood Risk Assessment must demonstrate that the development will besafe, without increasing flood risk elsewhere, and, where possible, will reduce floodrisk overall.

The SFRA provides sufficient information to complete the Sequential Test in terms of floodrisk. However it can only provide information on where it will be necessary to complete theException Test and areas where part c) of the Exception Test is most likely to be met. It willnot provide sufficient information to complete the Exception Test. To pass part c) moredetailed assessment of risk will still be required. Only on completion of the Sequential Testshould the Exception Test be used to justify allocations or developments in high risk areas.Whilst the SFRA has been undertaken in conjunction with the Environment Agency, it is likelythey will object to some of the sites, and may maintain objections to these on site specificflood risk grounds unless sufficient information can be provided to show the risks can besafely mitigated in the design.

This is a matter of detail that cannot be addressed in a SFRA however; elements that willneed to be considered in the delivery of the Exception Test include:

• Will the development be safe? Can all the risks be designed out and can theresidual risks to people and property be managed by an emergency plan or bylimiting the type of land use?

• Will the site be deliverable? This involves a review of economic and design aspects,together with an understanding of how complicated the assessment will need to beand how “exceptional” the development would need to be.

• How well does the development fit with the current mix of land uses and futureprovision of flood management measures? Can development within the policyarea reduce flood risk to other areas; will it require further more expensive provisionof flood defence infrastructure?

4.8 Management Decisions and Actions

Throughout the risk based sequential approach, management actions to avoid, substituteand mitigate flood risk should always be kept in mind and opportunities taken to minimiseflood risk at every stage of the planning process. The principle aim of these actions is toensure that risks to receptors are reduced to acceptable levels and the risks of flooding topeople, their property and the environment.

As previously discussed the hierarchy of management decisions and actions include:

• Avoidance by locating new development outside areas at risk of flooding;

• Substitution by changing from a more to a less vulnerable land use; and

• Mitigation by instituting measures such as flood-protection schemes to protectproperty against flooding.

Whilst avoidance is clearly the preferred solution for new development, there are alreadysubstantial areas of development within flood-risk areas and some new development willhave to take place there. For these situations, mitigation is needed to reduce flood risks toan acceptable level. This can comprise community protection through the use of floodprotection barriers (flood walls or embankments), flood-detention reservoirs to attenuateflow upstream from the receptors at risk, increasing the flow capacity of rivers throughdredging and construction of diversion channels. It can also include protection toindividual properties using flood-resistance measures, such as temporary flood barriers to beinstalled on receipt of flood warning, and flood-resilience measures to make propertiesmore easily repairable after a flood.

The fact that mitigation measures are discussed in this SFRA should not be taken as apresumption that the Sequential Test has been short circuited. It is included to give



39

improved understanding of the consequences associated with allocation of a site fordevelopment, or assessing development proposals on a site in high risk areas. It is also usedto provide additional indicative evidence for assessment of the Exception Test. Mitigationmeasures must be designed to provide an appropriate level of flood mitigation to a site forthe lifetime of the development. At most sites it is technically feasible to mitigate ormanage flood risk (if potential off-site impacts are ignored). However, where the depth offlooding is substantial, these mitigation measures may result in practical constraints todevelopment with significant financial implications. The Exception Test needs to explicitlyunderstand offsite impacts of development as well as the limiting factors that influenceflood risk.

Often the determining factor in deciding whether a particular development can proceed isthe financial feasibility of flood risk mitigation rather than technical limitations. It is importantthat recommendations for allocation should not be made when there is little or no chanceof feasible and cost effective mitigation measures being realised. Demonstrating that a sitecan be developed is, however, difficult without a detailed Flood Risk Assessment.

At the SFRA stage broad assumptions need to be made about the feasibility of flood riskmitigation so that sites with realistic development potential are put forward. In this contextthe assumptions shown in the following table have been made. It is assumed that floor levelraising will continue to be the traditional mitigation measure, however, it should be notedthat the Environment Agency consider land raising to be a final option rather than a desiredapproach to flood risk management.

Suggested screening criteria for mitigation measures are shown in Table 4-1 below. Thistable refers to indicative depths of flooding before mitigation measures are put in placeand should not be mistaken for acceptable levels of flooding after mitigation. These depthsdo NOT represent acceptable flooding.

Table 4-1: Suggested Screening Criteria for Mitigation Measures

Depth of Inundation* Comments0 to 1.0 m Sustainable mitigation and flood risk management may be

feasible for both housing and employment purposes. There is agreater likelihood that the Exception Test can be passed.

1.0 to 1.5 m Mitigation is likely to be costly and may not be economicallyjustifiable for low value land uses. Housing allocations areconsidered appropriate, provided flood risk can be managed ormitigated (e.g. by using lower levels for car parks or public areas).Floor level raising for employment purposes is unlikely to beeconomically viable and employment allocations should bereconsidered in favour of alternative lower risk sites. The likelihoodof passing the Exception Test is lower.

Above 1.5 m Flood risk mitigation measures are unlikely to be economicallyjustifiable and both housing and employment allocations shouldbe reconsidered in favour of alternative lower risk sites.Development is unlikely to be sustainable and the likelihood ofpassing the Exception Test is low.

Notes: * Based on predicted depth of inundation for the 1% (Fluvial) event + 20% additional flow for ClimateChange as per PPS 25. Environment Agency flood zone data.

In addition other screening factors may be used including:

• Speed and direction of flooding;

• Ability to achieve safe access and egress;

• Emergency Services ability to undertake safe and effective evacuation;

• Risk from multiple and combined flooding sources;



40

• Existing flood warning arrangements in place and/or potential for further application;

• Level of community awareness; and

• Impacts on local essential services infrastructure etc.

It is recognised that in some locations urban regeneration and redevelopment will beessential to maintain the long term viability and vitality of communities and the balance ofplanning considerations may support redevelopment. These social and economicconsiderations may justify some flexibility of the screening criteria set out above and theretention of housing and employment sites in certain areas. In these instances thecommercial viability of the development and risks to public safety will need to be givencareful considerations during the planning of the development. A range of floodmanagement and flood proofing measures are available that can reduce the financialimpacts of flooding.

Whilst flooding mitigation measures can be implemented in most sites, it is worth noting thatin some instances the findings of individual Flood Risk Assessments may determine that therisk of flooding to a proposed development is too great and mitigation measures are notfeasible. In these instances, the development will be subject to an objection by theEnvironment Agency. Further details on avoidance, substitution and mitigation arecontained in the recent Department for Communities and Local Government publication“Improving the flood performance of new buildings - Flood resilient construction - May 2007.

As part of the hierarchy of management decisions and actions to help provide a degree ofconfidence that individual development allocations may or may not pass the ExceptionTest, a small suite of flood risk indicators can be used to balance and weigh various sitesand uses. This process is described below.

4.9 Flood Risk Indicators and Balance Sheet

The SFRA is precautionary, applying a longer term holistic approach to ensuringdevelopment does not compromise future flood management measures and vice versa.The Exception Test is not black and white, and needs to assess the acceptability of theresidual risks. Where the residual risks are significant it is unlikely that further investmentwould exceptionally be justified, particularly if it introduces significantly more people intothe flood risk area.

To provide this longer term view to spatial planning in flood risk areas a number of indicatorshave been developed to allow a comparison of the appropriate land uses in each policyarea and how they would fare within the PPS 25 Exception Test. Whilst these indicatorsfocus on flood risk issues, alternative sustainability measures could be added to the list toencapsulate all relevant issues into the assessment and help LPA assess whetherdevelopments have passed Part ‘a’ of the Exceptions Test. Further indicators could befound in the relevant LPA Sustainability Appraisal. The main flood risk indicators suggestedwithin this SFRA are as follows:

• Development is within existing flood risk area – existing flood warning andevacuation in place. Importantly how easily will the area recover following a floodevent? New development may lose local services for 12months if an event occurs.

• Residual risk measures are easily applied and within a norm – Low depths of floodingcan be easily designed out by modest alteration of ground or floor levels. 1st flooraccommodation has implications for the urban design and place setting of thedevelopment.

• Egress and access. Impact on emergency planning provision and whetherdevelopment would be safe – This is a key issue and prime test in the PPS 25Exception Test. Access routes need to be natural and accessible in a flood to theemergency services



41

• Change in the number of people at risk as result of development – Introduction ofmore people will put a greater strain on the emergency services in an event. Whilstthey may be accommodated at high elevation they will require support very quicklyeven after the inundation has stopped.

• Change in number of properties at risk in 1% and 0.1% event before and after.Assumes mitigation measures put in place – From an economic viewpointdevelopment can replace existing property with lower vulnerability land uses andalso development that is designed to be flood resistant or resilient. A reduction ineconomic risk can be achieved.

• Scale and nature of flood risks – The residual risk maps indicate likely depths and flowroutes. From running the surface water screening assessment the scale and extentof the surface water flood risks can be considered.

• Impact of mitigation measure on other areas downstream and adjacent – How wideranging does the impact assessment need to be to take account of the effects ofsignificant land raising or alteration or blockage of flow routes.

LPAs should use these indicators to qualitatively assess each key type of vulnerable land useproposed in each of the policy areas being considered by the SFRA. Each of the indicatorsshould be scored according to the system outlined in Table 4-2 below to produce a flood-risk balance sheet. The results should be assessed to produce one of five possible outcomeson the acceptability of a particular type of development within a policy area. The fivepotential outcomes are:

• Counter to strategic approach, flood risk unacceptable. It would be difficult tomeet the criteria of the Exception Test. Development not recommended;

• Sequentially not preferred but a limited range of land uses might be possible;

• Sequentially not preferred but a wider range of land uses could be brought forwardafter careful consideration and subject to an appropriate site-specific FRA;

• Acceptable with some detailed consideration of flood-risk issues to be resolved byan appropriate site-specific FRA; and

• Acceptable subject to a satisfactory appropriate site-specific FRA.

This simple assessment through the flood-risk balance sheet allows an initial sequentialapproach to be adopted against flood-risk criteria to deliver a hierarchy of recommendedland uses and development allocations that meet the criteria of the Exception Test, whereappropriate. This will help support appropriate policies within LDFs & LDDs and provide theevidence for the LPA in reviewing any subsequent planning applications that attempt touse the Exception Test to support alternative land uses in these areas. An example of acompleted flood risk balance sheet is contained in Appendix B: - of this report.

It should be noted that a detailed flood risk assessment will always be required.

4.10 Influencing Land Use Planning

Flood risk is a material consideration in land use planning decision making and can greatlyimpact on the sustainability of various land uses in all locations. Having completed anappropriate flood risk assessment for a development proposal under consideration, andapplied the Sequential Test and Exception Test where necessary, the resultant assessment ofappropriateness and associated flood risk information will then influence the land useplanning decision at whatever level it is being considered. Land use policies and widerstrategic decisions involving social and economic development in RSS, LDFs and LDDs willbe influenced and shaped by the sequential approach informed by the RFRA and LocalAuthority SFRAs. In turn, individual planning applications will be influenced by the site-specific FRA having regard to the LDF and LDD, and either granted with flood risk conditions



42

or rejected by the LPA. Planners and developers should take full account of the sequentialapproach taken, including the results of the sequential and exception tests to assist theirdecision making.

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44

5 OVERVIEW OF FLOOD RISKS

5.1 Introduction

As discussed in Section 2 of this report flooding can occur from many different sources andPPS 25 requires all of these flood risks to be considered at all stages of the planning process.The Calder, Aire and Don catchments all have their own unique characteristics andflooding issues that need to be considered as part of the land use planning process. It willbe helpful to planners and developers to have an overview of these factors prior toundertaking the Sequential and Exception Tests as part of the risk based sequentialapproach and then allocating proposed development sites in these catchments. Theprinciple catchment characteristics and flooding issues from different sources are discussedbelow.

5.2 Main River Flooding

The Calderdale, Kirklees and Wakefield Districts contain reaches of 27 designated mainrivers. These main rivers are located in 3 different catchments, the Calder, Aire and Don.The River Calder flows into the River Aire near Castleford. Both the River Aire and the RiverDon flow into the River Ouse near Goole.

The upper Calder and its tributaries are sensitive to sediment accumulation. Theuncontrolled accumulation of sediment has the potential to increase flood risk and anumber of sediment traps have been constructed. To allow the Environment Agency toinstall, manage and maintain these sediment traps the watercourses on which they arelocated have been enmained, often for only very short reaches (e.g. Tower Clough which isonly enmained for 26 m).

The Aire, Calder and Don and Rother CFMPs contains summaries of historical flood eventsalong with current and future levels of flood risk impacting on land, people, buildings andthe environment.

This section contains information and guidance on: The River Calder flow responses,catchment descriptions, flood risk issues from different sources, identification ofwatercourses and historical flood events.

Key messages:

• Significant lengths of rivers and watercourses exist in the study area which cangive rise to flooding problems;

• Whilst many urban areas are outside the flood plain some built up areas are at riskof flooding from a number of different sources;

• SFRA Flood Risk Maps provide a valuable starting point in considering flood risk asa material consideration in land use planning decisions and;

• Detailed FRAs need to explore the condition and longevity of flood defencesthoroughly; and

• Close liaison should be maintained with the Environment Agency to always ensurespecific FRM data and information used is the latest and most recent available.



45

5.3 Calder Catchment

5.3.1 Catchment Descriptors

The River Calder rises on the Pennine Moors west of Todmorden. It is predominantly anurban river, flowing through the West Yorkshire towns of Brighouse, Huddersfield, Dewsburyand Wakefield, before it joins the River Aire at Castleford.

The catchment has an area of approximately 960 km² and a population of approximately800,000. There are approximately 13,300 properties at risk of flooding in the Calder, Colne,Holme, Spen and Ings Beck catchments.

The upper reaches of the Calder and many of its tributaries flow through steep andrelatively narrow valleys, which means they react quickly to rainfall – or are “flashy”. Heavyrainfall causes rapid rises in water level, which contributes to the flood risk in many of thecommunities.

Downstream of Dewsbury the floodplains of the Calder broaden and include large areas ofwashland. These washlands act as flood storages attenuating peak flows. Consequentlywater levels rise and fall more slowly and peak flows are often lower than upstream ofDewsbury.

5.3.2 Flooding Issues

In the upper reaches of the Calder catchment and its many tributaries (including RiversColne and Holme) valleys are generally narrow and steep sided, and consequently floodzones are narrow. Existing development is mostly housing, commercial or small areas of lightindustry.

Where present flood defences typically consist of discontinuous flood walls in mixedcondition. The standard of protection provided by defences is typically low, mostly less than25 years and less than 50 years throughout. The condition of defences exposes them to riskof failure in extreme flood events. The capacity of structures such as culverts and bridgealso contributes to flood risk, as does the tendency for coarse sediment to accumulate atstructures and in certain reaches. In many locations flood risk is considered to be very highwith estimated flood depths of between 1 and 3 m not uncommon in Zone 3a areas.

In the middle catchment (i.e. River Calder downstream of Elland, River Colne downstreamof River Holme – to Dewsbury) the topography of the valley is not as steep, the floodplainbroadens and land use changes to include large areas of heavy industry. Some largehousing areas are located in the high risk zone in Mirfield and Dewsbury. A review of flowgauge records shows that whilst the floodplain broadens there is no significant attenuationof peak flows and consequently flood waters continue to rise and fall quickly. Defences arediscontinuous and consist of a mix of flood walls and earth embankments. Where defencesare present they typically provide a standard of protection of 20 years or greater.

Downstream of Dewsbury the floodplain broadens further and the river takes on a lowlandcharacter. The floodplain includes large areas of engineered washland which act toattenuate peak flows. Consequently flood levels rise and fall slower and peak flows do notreach the levels experienced upstream. The floodplain includes large areas of urbandevelopment in Wakefield and at Horbury Bridge. Defences are more widespread,continuous and in fair to good condition. Defence crest levels are typically near or abovethe 1% water level although gaps are present in some locations which reduce the overallstandard of protection to as low as 10 years in some places.

The Wakefield flood defence scheme will fill many of these gaps and provide a 100 yearstandard of protection to Wakefield. Where defences are less than the 100 year standardand the depth of flooding exceeds 1 metre these areas are unsuitable for developmentand allocations.



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The Draft CFMP identifies a number of key points in respect of flooding in the Caldercatchment as below:

• The current number of people at risk of flooding during a 1% AEP flood event is36,234. Future flood risk analysis indicates that this figure may increase by 2,116 to38,350, showing a 6% increase;

• The current number of people at risk of flooding during a 5% AEP flood is 26,370. Thisfigure may increase by 6,182 to 32,552, an increase of 23%;

• Currently there are 20,904 properties at risk of flooding during a 1% AEP flood event.In the future this may increase by 960 properties to 21,864, being a 5% increase in theflood risk;

• The general risk of flooding in the future is likely to be from a greater increase duringsmall floods than the 1% AEP. Flooding is likely not only going to become morefrequent through climate change, but the consequences of this flooding are goingto increase significantly;

• The risk of flooding to the natural and cultural environment is limited both now and inthe future; and

• Significant lengths of the transport network are at risk of flooding. Currently 58kilometres are at risk during a 1% flood however; this raises to 63 kilometres in thefuture, an increase of over 4 kilometres.

5.4 Aire Catchment


The River Aire flows in a general south easterly direction from its source in the Yorkshire Dalesnear Malham to its confluence with the River Ouse near Goole. The catchment has anarea of approximately 2,060 km2 (including the River Calder).

The catchment is predominantly rural in nature. The River Aire has been considerablymodified for flood defence purposes. Long reaches of the channel are embanked andthere are several controlled washland (floodplain) areas. These controlled washlands andalso a number of uncontrolled washlands significantly attenuate peak flows along the river.

Castleford and Knottingley (in Wakefield district) are situated on the right (southern) banksof the River Aire. Large areas of the River Aire floodplain through this reach are designatedas washland and flood flows are attenuated substantially by these washland systems. Thewashlands are predominantly located on the left (north) bank of the River Aire.

The River Aire catchment also contains Wash Dike and Oulton Beck which drain parts ofWakefield district (Pontefract, Knottingley and Lofthouse Gate).


The existing settlements of Castleford and Knottingley are mostly located on elevated landand are above the 1% water level.

The part of Castleford located on the left bank of the River Aire is on low lying land and isdefended by earth embankments which are in good condition. The River Aire modelsuggests that these defences provide less than 100 year standard of protection and theright bank of the River Aire through Castleford is elevated and mostly above the 1% waterlevel.

Eastern parts of Knottingley (including housing and industrial areas) are located within thehigh risk zone and are below the estimated 1% water level within the River Aire. These areasbenefit from right bank defences of the River Aire comprising flood walls and earthembankments. The defence crest levels are above the 1% water level. However, NFCDD



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suggests that the earth embankments are in poor condition as a result of erosion bylivestock.

Wash Dike is a tributary which flows into the Aire at Knottingley and its catchment drainsPontefract and surrounding areas. Whilst flood zones in this area are narrow and are largelyremote from existing development, Wash Dike and its tributaries have a history of floodingand future development in this catchment will need to be sensitive to these historical issues.

The relatively flat topography of this area means that small increases in water level canresult in large expansion in flood extent.

The Draft CFMP identifies a number of key points in respect of flooding in the Airecatchment as below:

• Due to the location of development, fluvial flood risk is significantly high during smallflood events as well as significant events;

• During a 1% flood event, 21 percent of the population are at risk of fluvial flooding;

• 10 % of the transport network at risk of fluvial flooding during a 5% AEP flood, thisincreases to 15% during a 0.1% flood;

• There are a large number of gas and electricity installations at risk of fluvial flooding.Autumn 2000 gave a clear indication of the potential consequences of theseinstallation flooding; and

• There are between 3,056 and 4,112 commercial properties at risk of fluvial floodingand flooding of these properties would have significant impacts on the local andwider economy.

• In total 348 properties have reported sewer flooding. 179 of these experiencedinternal sewer flooding whilst 169 experienced external sewer flooding.

5.5 Don Catchment


The River Don rises on the Southern Pennines, an area of high ground formed of MillstoneGrit and Coal Measures. The river generally flows in a northerly direction toward the RiverOuse. The Don’s two main tributaries are the River Rother to the South and the Dearne tothe North. A further two main rivers, Ea Beck and the River Went, join the Don downstreamof Doncaster. The total area of the Don Catchment is 1,682 km².

Wakefield district includes the upper parts of the River Went and Ea Beck catchments.These catchments are low lying and very flat. Within Wakefield district the catchments arepartly drained under the management of the Went and Dun Internal Drainage Boards.

Kirklees district includes the upper reaches of the River Dearne and catchment. The upperreaches of the Dearne catchment are more elevated and much steeper than the RiverWent and Ea Beck and consequently these watercourses respond quickly to rainfall.


Flood zones in the River Dearne, River Went and Ea Beck catchments are typically remotefrom areas of existing development. The designation of a number of tributaries of thesecatchments as COWs however indicates that flooding is an issue in some areas. Futuredevelopment adjacent to these watercourses will need to consider these flood risks anddevelopment with the catchments will need to employ sustainable urban drainage or flowretention systems to prevent an increase in flood risk.



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5.6 Ordinary Watercourse Flooding

Ordinary watercourses are those that are not designated ‘Main River’ and therefore comeunder the control of the local authority, who have Permissive Powers to carryout worksshould this be deemed necessary.

A number of the ordinary watercourses within Calderdale and Kirklees MBC and WakefieldMDC were previously designated by the Environment Agency as Critical OrdinaryWatercourses (COWs). This designation reflects a known issue with respect to flooding, andis generally associated with (for example) limited channel capacity, channel constrictionsand/or a poor maintenance regime. In 2006/7 the Environment Agency enmained all theremaining COWs and took over responsibility for their maintenance and management. Allthe previous COWs are now defined as ‘Main Rivers’.

A summary of previously designated COWs within Calderdale and Kirklees MBC andWakefield MDC areas are presented in Table 5-1 below:

Table 5-1: Previously Designated Critical Ordinary Watercourses

Council Authority Number Length (km)

Calderdale 5 6.88

Kirklees 28 53.27

Wakefield 15 26.94

For the purposes of the SFRA, flooding issues in respect of COWs have been considered tobe a good summary of the entire current non-main river flooding issues, although when FRAsare undertaken, full consultation with the Environment Agency and relevant LocalAuthorities should take place.

The fluvial flood extent and depth maps discussed in Section 5 of this report and attachedfor key local authority areas; identify the potential scale of flood inundation and should beused to guide the sequential approach and detailed FRAs.

5.7 Surface Water Flooding

Development allocations often represent an infill into an existing urban environment. Assuch, the development of that allocation has the potential to alter flood risk on localwatercourses and drainage infrastructure. The impact that the development may haveupon the current flooding regime is varied, and is dependant largely upon the existingcatchment hydrology (e.g. topography, percentage urbanised, drainage system capacityetc).

Surface water flooding occurs where high rainfall events exceed the drainage capacity inan area and these events can lead to serious flooding of property and possessions asdemonstrated by the summer 2007 floods. In addition, large amounts of surface waterrunoff can lead to water quality problems and potential health risks to people. Theseimpacts can typically be mitigated through the implementation of established ‘bestpractice’ drainage techniques including Sustainable Urban Drainage Systems (SUDS) at theplanning application stage. However, in some circumstances site constraints dictate that acatchment-wide, holistic approach to surface water flood management is required throughurban catchment planning and strategic consideration of the design, construction,maintenance and improvement of sewers and watercourses. Close liaison between WaterCompanies, Local Authorities and the Environment Agency is essential to ensure aconsistent and co-ordinated approach to surface water management and this may bebest achieved by the production of appropriate surface water management plans asdiscussed in the Pitt Review.



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The areas naturally vulnerable to surface water flooding maps discussed in Section 5 of thisreport and attached for key local authority areas, show actual surface water flood extentand variation in depths due to an extreme rainfall event. Again, these maps should not onlybe used to assist the strategic consideration of the impacts of surface water flooding butalso the sequential approach, the production of Surface Water Management Plans(SWMPs), and detailed FRAs for specific development proposals.

5.8 Groundwater Flooding

Groundwater flooding is caused by the emergence of water originating from underground.The water may emerge from either point or diffuse locations. The occurrence ofgroundwater flooding is usually very local.

Unlike flooding from rivers and the sea, groundwater flooding does not generally pose asignificant risk to life, but is more associated with significant damage to property, withflooding persisting over a number of weeks for some types of groundwater flooding.Groundwater flooding is a significant but localised issue that has attracted an increasingamount of public concern in recent years.

Groundwater flooding arises from:

• Natural exceptional rises in groundwater level, reactivating springs and short livedwatercourses (often referred to as ‘clearwater’ flooding);

• Rising groundwater (rebound) following reductions in historic abstraction;

• Mine water recovering to natural levels following cessation of pumping; and

• Local shallow drainage/flooding problems unrelated to deep groundwaterresponses.

Key issues are:

• Groundwater flooding is sporadic in time and location, but when it occurs it usuallylasts longer than surface water flooding and interferes with property andinfrastructure (such as roads).

• In most cases groundwater flooding cannot be easily managed or lasting solutionsengineered.

There are many other localised and site-specific reasons for water to emerge at the surfaceor to appear in basements, for example, leaking water mains and sewers, blocked drains,and impedance of natural drainage routes by urban development or deepening of cellarsto below the natural water table.

Groundwater flooding has been the focus of one of the key projects under Defra’s makingspace for water programme and the outputs are available on the Defra website.

5.9 Reservoir Flooding

According to the Environment Agency’s Register of Reservoirs, there are 72 ‘large raisedreservoirs’ located within the boundaries of the Calder SFRA boundary, 2 of which are underconstruction and 1 has been abandoned. Reservoirs can attenuate flows in a similarmanner to washlands and floodplains, depending upon how they are managed. Atpresent these reservoirs are often full in winter and so provide little attenuation for flooding.

Table 5-2: Reservoir Location Details

Local Authority Number Total Capacity

Calderdale 27 23,265,600 m³



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Table 5-2: Reservoir Location Details

Local Authority Number Total Capacity

Kirklees 27 22,799,112 m³

Wakefield 18 6,215,483 m³

Total 72 52,280,195 m³Source: EA Register of Reservoirs 2008

The construction of new specific flood storage reservoirs such as the Central Vale Park FSA inTodmorden can help reduce peak waters in the upper reaches of the River Calder. Theycan also attenuate flood waters so flood peaks do not occur simultaneous and thus can beused as an effective flood management control. Reservoirs located at the head of thevalley also play a vital role in maintaining river flow throughout the year which has widerenvironmental benefits.

Reservoirs can also act as a major source of floor risk, as experienced recently during the2007 summer floods, where 18 reservoirs were affected across England. Reservoir flooding istherefore an important source of flood risk which has been noted within Pitt Review andacknowledged by Hilary Benn, the Secretary of State for Environment, Food and RuralAffairs, who has pledged £1 million to improve reservoir safety specifically includes forinundation mapping.

Whilst the probability of dam failure or breaching occurring is very small, the consequencesof such an event can be devastating thereby presenting a risk of flooding which has to beconsidered. Reservoirs are classified on a consequence of failure basis outlined below inTable 5-3 and it is now suggested that a better risk-based approach to reservoir safety isneeded, focusing on those reservoirs that pose the greatest risk to the public, even if they’renot currently covered by the regulations.

Table 5-3: Reservoir Consequence Classification

Dam Category Potential Consequence of Reservoir FailureA At least 10 lives at risk and extensive property damage

B Fewer than 10 lives at risk or extensive property damage

C Negligible risk to human life but some property damage

D Negligible risk to human life and very limited propertydamage

Currently the Water Act 2003, which amended the Reservoirs Act 1975, requires all reservoirundertakers to prepare flood plans for those reservoirs where the dam failure could putpeople’s lives at risk or lead to major damage. These plans are expected to become alegal requirement in spring 2009. Defra is currently funding a project to produce a ‘Guide toEmergency Planning for UK Reservoirs’, which will ultimately use the flood plans.

The reservoir flood plan will include:

• An inundation analysis to identify the extent and severity of flooding which couldresult from an uncontrolled release of water (i.e. breaching or failure).

• An on-site plan setting out what the undertaker would do in an emergency to tryand to contain and limit the effects of the incident, and

• A communications plan with external organisations, mainly the emergency services.



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Until the new Water and Floods Bill is implemented it is unclear how reservoir safety, flood riskfrom breach and planning will be dealt with. In the meantime any allocations orapplication for development immediately downstream of a reservoir should be consideredcarefully in liaison with the Environment Agency. It should be noted that the hazard is wellmanaged through effective legislation and it is unlikely that the impact zone downstream ofa reservoir would not allow permitted development, or require mitigation measures. It islikely it would remain an emergency planning issue.

5.10 Condition of Flood Defences

The condition of existing flood defences is an important consideration for local authorityplanners when allocating new development. PPS 25 considers that defended areas (i.e.those areas that are protected to some degree against flooding by the presence of aformalised flood defence) are still at risk of flooding, and therefore sites within these areasmust be assessed with respect to the adequacy of the defences.

The location and condition of all flood defences is provided by the Environment Agency viathe National Fluvial and Coastal Defence Database (NFCDD).

The condition of existing defences is provided in the form of a ‘rating’ (1 to 5), and is areflection of any signs of ‘obvious’ structural problems. The condition rating is determinedon the basis of visual inspection, focussing on obvious signs of structural defect (e.g.slippage, cracking, poor maintenance), designed to inform the maintenance programme.A summary of the NFCDD condition rating allocations is shown in Table 5-4 below.

Table 5-4: NFCDD Condition Ratings for Flood Defences

ConditionRating

Condition Condition Description

1 Very Good Fully serviceable.

2 Good Minor defects.

3 Fair Some cause for concern. Requires careful monitoring.

4 Poor Structurally unsound now or in the future.

5 Very Poor Completely failed and derelict.

The condition of existing flood defences and whether they will continue to be maintainedand/or improved in the future, is an issue than needs to be considered as part of the riskbased sequential approach and in the light of this, whether proposed land allocations areappropriate and sustainable. In addition, detailed FRAs will need to explore the conditionof defences thoroughly, especially where these defences are informal and contain a widevariation of condition grades.

5.11 Residual Flood Risk

Residual risks are the risks that remain after all risk avoidance, substitution and mitigationmeasures have been taken. The residual risks in the Calder Valley are therefore related tothe occurrence of events of low probability, such as extreme flood events greater than thedesign capacity of the constrained river system or failure of these flood defences.

In the case of the Calder Valley, present flood defences typically consist of discontinuousflood walls in mixed condition. The Standard of Protection provided is typically low, mostlyless than 25 years and less than 50 years throughout. The quality of the formal riverdefences are high and the probability of flooding in these areas is low to moderate.However, the consequences of flooding are very large. The topography of the land behinddefences, flow routes, land use and access and egress are all key factors in identifyingthese higher flood risk areas. Areas directly adjacent to the defences can be subject tohigh flow velocities should the defence overtop or fail, known as rapid inundation zones,



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whilst low lying areas further away from the defences are at risk from the sheer depth offlooding.

A typical range of defence standard for the Upper Calder Valley is between a 5% (1:20y)and a 1.3% (1:75y) flood event with areas such as Central Wakefield benefiting fromprotection up to a 1% (1:100y) event. However, there is always the possibility of a largerevent occurring and overtopping the defence, which must be investigated.

Whilst Environment Agency Flood Maps provide a sufficient starting point in investigatingflood risk in the Calder Valley, they do not provide the level of detail needed to assess theresidual risk, especially those which lie behind defences.

This SFRA has provided sufficient data and information to enable Calderdale, Kirklees andWakefield to apply to Sequential Test and goes some way in investigating residual risk inproviding a suit of SFRA Flood Risk Maps (discussed in the next section). However it maybeappropriate for each council to consider undertaking a level 2 SFRA in specificdevelopment locations to gain a better understanding of actual residual risks andfloodplain mechanisms.



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6 SFRA FLOOD RISK MAPS

6.1 Introduction

The investigation and identification of the extent and level of flood risk to an area isassessed primarily geographically. Whilst the Environment Agency’s Flood Maps are veryuseful in this respect in showing indicative land use planning zones as required by PPS 25,they are a starting point in the consideration of flood risk in a particular area.

Environment Agency Flood Maps should be used primarily to enable the sequential test tobe carried out, firstly in avoiding inappropriate development and then secondly, to seekcompatibility between flood risk vulnerability and flood zones as required in Table D3 of PPS25.

However, consideration of actual flood risk factors is also needed to gain a greaterunderstanding of the varying degree of flood risk at a district level. These include:

• Presence of defences

• Functional floodplain

• Speed of flood flow

• Variations in depth of flood water

• Flooding from other sources

• The impact of climate change on flood extents and depths

• Ability for emergency evacuation in extreme events

At this SFRA level, it is not appropriate to look at flood risks in detail for individualdevelopment allocations, as this is a requirement of the site specific FRA and will beundertaken by developers in respect of specific development proposal and prior tosubmitting a planning application.

However, there is a need to undertake a broad assessment of flood risk issues, at the SFRAlevel, to assist the LA in making the spatial planning decisions required. This will enable a

This section contains information and guidance on: types of risk maps available, whatthey show and how they may be interpreted to assist the sequential approach.

Key messages:

• Flood risk maps provide a valuable source of broad scale current and future floodrisk information, to assist with the sequential approach sieving process.

• These maps supplement the Environment Agency’s Flood Maps, in so far as theydescribe the hazard to receptor in the floodplain for a range of events.

• The suite of maps should be viewed collectively and not as individual maps inisolation.

• These maps are appropriate for early and strategic consideration of development



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degree of certainty that the proposed development allocations put forward in the LDD,can comply with the Sequential and Exception Tests in PPS 25 and importantly thedevelopments will be safe for occupants and users.

This broad assessment is assisted greatly by the use of SFRA Flood Risk Maps providinginformation on flood risk factors needing to be taken into account. The EnvironmentAgency Flood Risk Map along with the supporting SFRA Flood Risk Maps, what they showand how they may be interpreted are explained below.

6.2 PPS 25 Flood Zone Maps

SET A: Figures A 1-1, A 2-1 and A 3-1

SET B: Figures B 1-1 to B 1-6, B 2-1 to B 2-8 and B 3-1 to B 3-5

The Environment Agency Flood Map has been provided on one key map at a councildistrict level. Version 3.8 of the Environment Agency Flood Zones issued in March 2008 hasbeen used as the latest flood zones in this area, whilst the functional floodplain has beendelineated using the method outline in Section 4.4.5.

This map illustrates:

• Flood Zone 2

• Flood Zone 3a

• Flood Zone 3b (Functional Floodplain)

• Defences

This key map should be used for the facilitating the undertaking of the Sequential Test byplanners and developers according to PPS 25, as discussed previously in Section 4.5 andillustrated within stage 1 of the Sequential Test sieving process.

Areas under greater development pressures within each LA have been provided with theirown map and been made available within the suite of SFRA Risk Maps discussed below.

The SFRA Risk Maps discussed below should be used to support the Environment AgencyFlood Maps in Sequential Testing as a second or third pass of the sieving process.

6.3 SFRA Risk Maps: Interpretation and use

Three sets of maps have been produced in support of the Environment Agency’s latestFlood Maps.

These maps should be considered as a complementary suite of broad scale flood riskinformation sources in support of the Environment Agency Flood Zone Maps and no onemap should be considered in isolation without reference to the others.

All three sets of maps need to be interpreted consistently for various proposed developmentlocations in order to complete the second or third pass of the sequential approach sievingprocess after the Environment Agency Flood Map has been used to carry out the first sweepor sequential testing. They can also be used “outside” of the sieving process to gain anunderstanding of various flood risk factors appertaining to non development locations andmore general areas of interest.

The detail provided in the SFRA Risk Maps will also facilitate the application of theExceptions Test where applicable.

All maps show flood extents and flood water depths, which are colour coded to representvarious depth ranges.

The three sets of maps include:



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• Fluvial Flood Extent and Depth Maps

• Climate Change Sensitivity Maps

• Areas Naturally Vulnerable to Surface Water Flooding Maps

6.4 Fluvial Flood Extent and Depth Maps

SET C: Figures C 1-1 to C 1-6, C 2-1 to C 2-8 and C 3-1 to C 3-5

The fluvial flood extent and depth maps show the potential scale of flood inundation duringovertopping of different standards of flood defence during a range of flood events (Theydo not include the input of a breach or failure of defences).

With specific regard to this SFRA, the typical range of defence standard for the UpperCalder Valley is to protect between a 5% (1:20y) and a 1.3% (1:75y) flood event. Each mapsheet shows four different sub-maps in boxes, each with their own particular characteristics.Each box relates to a standard of protection afforded to the land adjacent to the MainRivers and the magnitude of the fluvial flood event being considered.

Reading anti-clockwise from top right hand corner, these include:

• Boxed map 1 (BM1) - 1% (1:100y) flood event assuming flood defences existproviding a 5% (1:20y) standard of defences labelled ‘S20Q100’;

• Boxed map 2 (BM2) - 1% (1:100y) flood event assuming flood defences existproviding a 1.3% (1:75y) standard of defences labelled ‘S75Q100’;

• Boxed map 3 (BM3) - 0.1% (1:1000y) flood event assuming flood defences existproviding 1.3% (1:75y) standard of defences labelled ‘S75Q1000’; and

• Boxed map 4 (BM4) - 0.1% (1:1000y) flood event assuming flood defences existproviding 1% (1:100y) standard of defences labelled ‘S100Q1000’.

The deeper Main River channels are easily identified generally by yellow, orange or redcolours and the variation and graduation of colours from red to dark blue clearly shows theflood water depth at any particular point across the flooded area. Directional informationon depth is also available as for example, moving from shallower to deeper water, thegraduation of colours change from dark blue to red.

One of the key benefits with showing flood extents and depths for a range of flood eventsand standard of protection is to allow the user to make comparisons and draw conclusionsin the overall understanding of flood risk applicable to a specific proposed developmentallocation.

Examples of typical comparisons between these maps include:

• Comparing BM1 & BM2 it can clearly be seen that areas of land would not beflooded in a 1% flood event if the standard of defences were raised from 5% to 1.3%.The indication of depths can guide consideration of floor levels for buildings andsteer the improving flood defences in particular areas where depth differencesbetween levels of Stand of Protection are the greatest in critical developmentareas;

• Comparing BM3 & BM4 the effect of flooding on areas of land can be seen in anextreme 0.1% event, if the standard of defences were raised from 1.3% to 1%. Insome cases the flood extent may not vary greatly but the depth colours maychange significantly. This gives an indication that increased depth of water in anextreme event will need to be considered as a major hazard to occupants and theEmergency Services;



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• In comparing all four BMs in respect of a particular development allocation thevariation in colour and hence the depth of flood water at that site can bedetermined and avoidance, substituting (for a lower vulnerability use) andmitigation measures can start to be considered; and

• In comparing all four BMs, consistently coloured areas of floodplain indicate thatthese areas will flood to a similar depth for the 1% and the 0.1% events and will floodindependently of the existence of flood defences up to and including the 1%standard. Other than those coloured dark blue, these indicate areas wheredevelopment should be avoided. Open areas are likely to be frequently floodedand this flooding capacity should not be restricted.

6.5 Climate Change Sensitivity Maps

SET D: Figures D 1-1 to D 1-6, D 2-1 to D 2-8 and D 3-1 to D 3-5

Climate change sensitivity maps show actual fluvial flood extent and depths from MainRivers and extent and depths variations, for an undefended floodplain with a 1% (1:100y)flood flow plus a 20% increase in volume of flood flows. This allows for the effects of climatechange over the next 100 years. Each map sheet shows three different sub-maps in boxes,each with their own particular characteristics.

Reading anti-clockwise from the top left hand corner, these include:

• Boxed map 1 (BM1) – present day 1% (1:100y) flood assuming an undefendedfloodplain labelled ‘S2Q100’;

• Boxed map 2 (BM2) – future 1% (1:100y) including a 20% increase in flood flows totake account of current climate change prediction, assuming an undefendedfloodplain ‘S2Q100 + Climate change’; and

• Boxed map 3 (BM3) – the extent of depth change of flood water between BM1 andBM2 labelled ‘Depth Difference Map’.

As with the fluvial flood risk maps, depths of flooding for BMs 1 & 2 are indicated by differentcolours ranging from dark blue (0 - 0.5m) and red (5m+). BM3 shows a range of flood waterdepth differences between yellow (0.2 – 0.4m) and red (1m+).

When comparing BM1 and BM2 the increase in flooding extent due to climate change isevident with a number of areas of land currently not at flood risk being flooded in 100 yearstime, (assuming no intervention over that period). Where possible new developmentallocations should be considered more carefully in areas where climate is expected torequire adaptation of the development layout and design. Ideally development shouldtake a precautionary approach and be placed outside of the flood extent shown on BM2so as to avoid flood risk in the future.

PPS 25 requires the consideration of the sensitivity to new developments of climate changeto be considered as part of an appropriate FRA and these maps provide an early indicationof this sensitivity. In addition emergency evacuation routes and “high point” areas can beidentified at this broad scale and planned for outside of the flood extent, so as not to beoverwhelmed and put at risk in the future.

Reference to BM3 provides an indication of the increase in flood depth in various locationsdue to climate change, NOT to be confused with the actual depth of flood water. Thecolour shown and hence the depth figure indicates the DEPTH CHANGE. This informationcan be particularly useful when considering new developments and/or changes of use toland and existing buildings i.e. in regeneration areas.

The sensitivity of a particular location and land use to climate change can be factored intodecisions regarding floor levels, building uses and safe access and egress etc. Greaterchanges in depth can be associated with greater increases in flood risk and in these areas,



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where this risk cannot be avoided, or substituted, mitigation measures are likely to beextensive and for some developments, the FRA may not be able to demonstrate continuedsafety for occupants as required by the Exception Test in PPS 25.

The sequential approach requires early consideration of the effects climate change onflood risk and these maps help greatly in this respect.

6.6 Areas Naturally Vulnerable to Surface Water Flooding Maps

SET E: Figures E 1-1 to E 1-11 (1:100 year)

SET F: Figures F 1-1 to F 1-11 (1:1000 year)

The areas naturally vulnerable to surface water flooding maps show actual surface waterflood extent and variation in depths for particular geographical areas of interest, assuminga 0.1% (1:1000yr) and a 1% (1:100yr) rainfall event; and 10% (1:10yr) sewer capacity. Themodelling technique includes the presence of flood defences and how water may pondbehind these defences. The outline extent of the Environment Agency’s Flood Zone 3 isshown for comparison.

There is one map per location area and the extent and variation in depth of potentialflooding due to surface water is shown in a yellow to red scale where the darker the red incolour, the deeper the flood water. These maps are extremely helpful in supplementing theFluvial Flood Extent and Depth Maps as they show where localised, flash flooding can causeproblems, even if the Main Rivers are not overflowing. This is often due to high intensityrainfall events, which exceed the capacity of sewer systems. As a result, surface water isunable to drain away safely and flooding results.

The maps typically show shallower (light yellow) flooded areas on tributaries and feederstreams to Main Rivers, where steeper sloping valleys exist and on the edge of the naturalfloodplain of Main Rivers, again where land levels tend to rise more steeply. The deeper(darker red) flooded areas are predominantly in valley bottoms and in the Main Riverfloodplain. From the maps it can be seen that there are many areas of land outside FloodZone 3, that are at risk from deep surface water flooding and this needs to be considered asan integral part of the assessment.

It is usual however; that surface water flood risks alone can be effectively mitigated,whereas fluvial flood risks or combined surface water and fluvial flood risk at a particularlocation can cause serious risks to people and property.

These maps are extremely helpful in supporting the Environment Agency Flood Map duringthe Sequential Test as indicated above to assess the relative degree of flood risk and wheresurface water flooding is sufficiently hazardous to jeopardise the principle of development.In particular they show where vulnerable areas are and if development allocations areproposed in these vulnerable areas then appropriate avoidance, substitution andmitigation measures are needed.

Many of the specific ways in which these maps are helpful to the consideration of flood riskare the same as stated above for the fluvial flood risk maps but acknowledging the risk isfrom a different source. However, the same areas of land coloured by both sets of mapsindicate a combined flood risk from fluvial and surface water sources.

6.7 Conclusion and Further use of SFRA Flood Risk Maps

Examples of conclusions and further uses of these maps include:

• Identifying general extents and depths of Main River flooding;

• Comparing flood extents generally and for specific areas, with those shown on theEnvironment Agency Flood Zone Maps;

• Comparing flood extent and depth relating to existing and future land uses;



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• Identifying where flooding problems are likely currently, and in the future in terms of:

• residential areas;

• business parks and industrial areas;

• schools, hospitals and civic buildings;

• transport activities including road and rail disruption;

• utility infrastructure such as water and sewage treatment works, pumpingstations, power stations and electricity supply sub stations etc;

• Assisting a sequential approach to locating new development in lower flood riskareas, having first carried out the sequential test using the Environment Agency’sFlood Zone Maps;

• Identifying the scope for maximising a sequential approach to the developmentallocation including layout and design.

• Identify areas of floodplain where preparations for emergencies are neededincluding emergency plans, flood warnings and evacuation etc;

• Assist emergency services activities on the ground to help avoid deep andpotentially fast flowing water;

• Identify the location of open space areas that currently flood and provide floodstorage without causing too much disruption to existing land uses and people andproperty; and

• Identify where these flood storage areas might be better utilised in future andlocations for potential new flood storage areas and washlands where developmentshould be avoided.

The maps are extremely useful in answering specific questions about specific developmentallocations, prior to the decision for the proposal to be subjected to the Exception Test inPPS 25. In particular, they are helpful by:

• Providing an early indication prior to detailed hydrological and hydraulic modelling,of the likelihood of the site and it’s occupants remaining safe in a 1% and a 0.1%flood event and the proposal being able to pass condition c) of the exception testin PPS 25;

• Showing where narrow or wide floodplains exist and the potential difficulties foremergency evacuation in an extreme event by land vehicles as opposed to boatuse or aircraft;

• Indicating current and future extents and depth of flooding in the proposeddevelopment area for 1% and 0.1% and 1% plus climate change flood events;

• Targeting valuable time and resources towards those development allocations thatare likely to succeeded as opposed to those which are likely not to pass theException Test and not gain planning approval due to flood risk constraints;

• Giving an early indication of the feasibility of providing appropriate mitigationmeasures. As flood water depths increase, effective and viable mitigation measurescan become less likely and more costly;

• Knowing the likely design, engineering and building requirements early on in theconsideration of the suitability of the site for the proposed development to assistfinancial estimates and consideration of the overall viability of development projectat that site;



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• Early appreciation and commitment to likely expenditure to make the site safe asrequired in PPS 25; and

• Early identification of flood storage and/or floodplain restoration as part of theoverall development proposal.



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7 GUIDANCE FOR DETAILED FLOOD RISK ASSESSMENTS

7.1 Introduction

As discussed in Section 3 of this report there are principally three levels of flood riskassessment namely, Regional Flood Risk Appraisals (RFRAs), Strategic Flood Risk Assessments(SFRAs) and Site-specific (known as Detailed) Flood Risk Assessments (FRAs). The FRAs aresite or project specific and are the responsibility of those proposing development toundertake. The principle aims of a FRA are to determine the acceptable management offlood risk to the development proposal itself and any impacts elsewhere, and to ensure thatthe development and its users/occupants remain safe in times of flood. The FRA willdetermine any effective flood mitigation measures necessary and include these in thedevelopment proposal. The FRA needs to demonstrate that the proposed development willnot increase flood risk either upstream or downstream of the site and all sources of flood risk,including fluvial, surface water runoff and drainage need to be considered. The FRA willthen be submitted to the LPA in support of the developers outline and/or detailed planningapplication.

Flood Risk Assessments for proposed development should follow the approachrecommended by:

• The Environment Agency (see its National Standing Advice to Local PlanningAuthorities for Planning Applications – Development and Flood Risk in England

This section contains information and guidance on: key FRA reference documents,general principles of flood risk assessment, surface water drainage, Flood Zones 3a and3b (including defended and undefended areas, public safety and rapid inundation,and the feasibility of flood risk mitigation), Flood Zone 2 and Flood Zone 1, and flood riskissues relating to other known flood risk areas including Internal Drainage Districts.

Key messages:

• Primary sources (PPS 25, Practice Guide and CIRIA Report 624) should be used forFRAs and be supplemented by information in this SFRA;

• FRAs are required for all development proposals in Flood Zones 2 and 3 and alsofor developments over 1 ha in Flood Zone 1;

• Surface water drainage assessments are required as an integral part of the FRA;

• Demonstration that technically feasible flood risk mitigation options are availableis required;

• Overtopping and breach of flood defences should be considered along withemergency access, egress and evacuation;

• FRAs should demonstrate that the development and it’s users and occupiers willremain safe in times of flood; and

• Functional floodplain should be considered as essential green infrastructure andsafeguarded wherever possible.



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(March 2007). See www.pipernetworking.com for all guidance on the scoping andundertaking of detailed FRAs.

• CIRIA Report C624 Development and Flood Risk – Guidance for the ConstructionIndustry (2004)

• PPS 25 and its Practice Guide.

These documents describe when a FRA is required, what it should contain and areextremely helpful in guiding developers to produce a “fit for purpose” FRA and arecommensurate with the advice given in this SFRA. All proposed development sites requireat least an initial assessment of flood risks. A detailed FRA will be required for alldevelopments that fall in the Flood Zone 2 and 3 and other sites where significant flood risk isidentified. A full FRA will be required for sites in Flood Zone 1, which are greater than 1ha.For smaller sites a Screening Study will determine whether further FRA is required.

The information that follows serves to highlight key aspects of detailed FRAs and should beused in conjunction with the principle sources of information identified above.

7.2 General Principles

Annex E of PPS 25 provides information on the general principles of flood risk assessmentand states the minimum requirements for all stages of the planning process. These include:

• Be proportionate to the risk and appropriate to the scale, nature and location of thedevelopment;

• Consider the risk arising fro the development in addition to the risk of flooding to thedevelopment;

• Take the impacts of climate change into account;

• Be undertaken as early as possible in the planning process;

• Consider potential adverse and beneficial aspects of flood risk managementinfrastructure;

• Consider the vulnerability of the users of the development;

• Consider and quantify difference types of flooding from all sources;

• Include the assessment of residual risks;

• Consider surface water drainage systems; and

• Be supported by appropriate data and information.

Figure 3.5 of the Practice Guide provides information on the scope of FRAs and this shouldbe used as a starting point for all development proposals and then supplemented to reflectany specific peculiarities or issues in respect of the particular development proposal or siteunder consideration.

Information on levels of flood risk assessment is provided in both the CIRIA C624 Publicationand Figure 3.4 of the Practice Guide. There are principally three levels of FRA:

• Level 1 – Screening study, to identify whether there are any flooding or surface watermanagement issues that need to be considered further;

• Level 2 – Scoping study, to be undertaken if the Level 1 FRA indicates that there areflood risk issues needing further consideration and these risk can be readilyquantified; and



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• Level 3 – Detailed study, where further quantitative analysis is required toappropriately assess flood related issues and determine any effective mitigationmeasures needed to be put in place.

Figure 3.6 in the Practice Guide provides a helpful list of typical sources of information tohelp undertake an appropriate FRA.

In addition, typical outputs of a Level 1 or Level 2 FRA, supported by guidance notes and aFRA pro-forma are contained in the Practice Guide and these include:

• Development description and location;

• Definition of flood hazard;

• Probability of flooding;

• Effects of climate change;

• Detailed development proposals;

• Flood risk impacts and management measures; and

• Consideration and management of off site and residual risks.

For all levels of FRA developers are advised to make early contact with the EnvironmentAgency and the LPA to discuss their proposals in outline and consider the site in respect ofthe risk based sequential approach contained within the SFRA.

7.3 Assessment and Mitigation of Fluvial Risk

The mitigation design criterion for development within floodplain areas are generally set toprotect against the flood event coinciding with a 1% annual probability of occurrence,including the impact of climate change. Detailed consideration will need to be given tothe impact these mitigation measures may have and it is a requirement to ensure that floodrisk is not increased elsewhere as a result of development. Compensation measures maytake the form of compensatory flood storage as mitigation for loss of floodplain, enhancedflood defences and flood compatible master planning. Compensation measures will beneeded in both defended and undefended floodplains. This concept is included in PPS 25and ensures that residual risk is appropriately managed in new and existing development.

Before embarking on detailed modelling, and in light of this SFRA, proposals fordevelopment should be discussed in detail with the Environment Agency at an early stage.

Detailed FRAs may need to be carried out using hydraulic models. However, before anymodelling is undertaken a review of available information should be conducted to assess ifmodelling is necessary. For fluvial floodplains an assessment of the hydrological regime isrequired. This should be undertaken using available gauged records and Flood EstimationHandbook (FEH) techniques. Where hydraulic modelling is necessary, it will need to includestructures, such as bridges and weirs that influence flood levels. This modelling should alsoinclude floodplains to accurately determine the depth and extent of flooding.

Whenever possible models should be verified using historical records of flooding. Itssensitivity to modelling assumptions and climate change should also be investigated.Mapping the extent of flooding in a specific location will assist the risk of flooding to aspecific development to be assessed.

Where allocations remain in high risk flood zone areas for other material considerations, itneeds to be demonstrated that technically feasible flood mitigation options are available.A fuller appreciation of the sustainability of the site and its mitigation measures will beaddressed via the Sustainability Appraisal. These measures must be designed to provide anappropriate level of flood mitigation to a site for the lifetime of the development. At mostsites it is technically feasible to mitigate or manage flood risk (if potential off-site impacts are



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ignored), however the measures required may result in some practical constraints ondevelopment and/or require significant financial cost where flood risk is high. The detailedFRA should build on initial potential mitigation measures considered when determining thelikelihood of the Exception Test being met as indicated earlier in Section 4 of this report.

7.4 Assessment of Surface Water Drainage Issues

Opportunities for developing an Integrated Water or Drainage Management Strategyacross development site boundaries should be explored, and a catchment led approachshould be adopted. This approach has been recognised in the consultation paper byDefra, Making Space for Water. An integrated approach to controlling surface waterdrainage can lead to a more efficient and reliable surface water management system as itenables a wider variety of potential flood mitigation options to be used. In addition tocontrolling flood risk, integrated management of surface water has potential benefits,including improved water quality and a reduction of water demand through grey waterrecycling.

Integrated drainage systems may be considered suitable for catchments where otherdevelopment is being planned or constructed, and where on-site measures are set inisolation of the systems and processes downstream.

Surface water drainage assessments are required where proposed development may besusceptible to flooding from surface water drainage systems. The potential impact uponareas downstream of the development, including the impact on a receiving watercourse,also needs careful consideration.

The specific requirements for surface water drainage systems will need to be discussed withthe Council’s Land Drainage Engineers, Environment Agency and the Water Company.Consideration should be given to whether a “greenfield runoff approach” to theassessment of source control is appropriate. This method is generally satisfactory in thecases where the development is relatively small, isolated from other planned sites and therunoff processes are fully understood.

The FRA should then conclude with an assessment of the scale of the impact, and therecommended approach to controlling surface water discharge from a proposeddevelopment.

The recent Government consultation on surface water drainage as discussed in Section 2 ofthis report should be considered when assessing surface water drainage as part of the FRA.In addition, Guidance for Developers and Regulators in Scotland on Drainage ImpactAssessments has been produced by the Scottish Environment Protection Agency (SPA) andothers, and this is a valuable reference document.

7.5 Flood Zone 3b – The Functional Floodplain

In PPS 25 only the water compatible uses are allowed in this Flood Zone once the SequentialTest has been carried out. Essential Infrastructure can be permitted after the Exceptions Testis passed. According to PPS 25, developers and local authorities should:

• Reduce overall level of flood risk in the area through the layout and form of thedevelopment and the appropriate application of sustainable drainage techniques;and

• Relocate existing development to land with a lower probability of flooding

In addition, according to PPS 25, essential infrastructure should:

• Remain operational and safe for users in times of flood;

• Result in no net loss of floodplain storage;



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• Not impede water flows; and

• Not increase flood risk elsewhere.

As discussed in Section 4.4.5 of this report, functional floodplain should be considered asessential green space infrastructure and be retained for the natural use of flood waterwherever possible.

7.6 Flood Zone 3a – High Probability

PPS 25 states that the water-compatible uses and less vulnerable development are allowedin this Flood Zone, following testing within the sequential process. According to PPS 25 highlyvulnerable development is not permitted. Essential infrastructure and more vulnerabledevelopment need to pass the Exception Test, while essential infrastructure should bedesigned and constructed to remain operational and safe for users in times of flood.

According to PPS 25, developers and local authorities should implement the following policyaims:

• Reduce the overall level of flood risk in the area through the layout and form of thedevelopment and the appropriate application of sustainable drainage techniques;

• Relocate existing development to land in zones with a lower probability of flooding;and

• Create space for flooding to occur by restoring functional floodplain and flood flowpathways and by identifying, allocating and safeguarding open space for floodstorage

The delineation of the subset zones of Flood Zone 3 may be sufficient to allow the spatialplanning process to continue, with development steered away from these high risk zones.However, regeneration of land or change in land use behind existing defended areas in theHigh Risk Zone will continue to require a more detailed assessment of the flood risk (i.e.whether the scale of risk is worth taking, and how sustainable and effective the mitigationmeasures would be (i.e. whether the risk could be managed). Where, due to widersustainable development reasons, there are no other suitable sites available in lower riskzones then an assessment of the actual risk within Flood Zone 3 is required. Annex G in PPS25 deals with managing residual flood risk.

It is for the developer to demonstrate how in planning terms this safety can be achievedand how the residual risks will be managed. A clear distinction between commercial floodstandards of protection and management of loss of life should be explored in the FRA. Agreater reliance on flood warning may be required, which is not always a tangiblealternative to accepting a lower standard of protection.

In the context of this discussion, an undefended area of floodplain as shown in Figure 7-1below is considered to be an area where the water level for the 1% event will be similar tothat in the relevant watercourse. These areas may be entirely undefended or if defencesare present they are discontinuous or constructed to a low standard. Figure 7-1 illustrateswhere the standard of protection is low and floodplain small and fills to the same level asthe river.



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Figure 7-1: Illustration of the Undefended Area Case

A defended area as shown in Figure 7-2 below is considered to be an area of floodplainwhere the defences will result in a water level for the 1% event that is considerably lowerthan in the source watercourse. This means the defences substantially (but not necessarilycompletely) mitigate the flood risk associated with the 1% event. These areas will bedefended to a minimum standard promoted by Defra, but not always necessarily to the 1%standard. Figure 7-2 illustrates where the overtopping or breach volume is small comparedto the floodplain receptor and allows a refined assessment of residual risk.

Figure 7-2: Illustration of the Defended Area Case

7.6.1 Undefended Areas – Flood Risk Mitigation

Within undefended or poorly defended Zone 3a areas, floor levels for housingdevelopments should, as a minimum, be situated above the acceptable standard of safetywith sufficient freeboard to account for uncertainties in flood level prediction and climatechange.

In accordance with PPS 25 development within Zone 3a may require flood riskmanagement measures, constructed with the operating authority’s satisfaction with adedicated financial sum to fully fund whole life maintenance and future climate changeadaptability costs. The following paragraphs help to define an appropriate standard offlood risk mitigation in undefended areas in the context of this SFRA.

The Sequential Test should be applied within the development site area, and it is consideredappropriate to direct more vulnerable land uses to parts of the site at less probability andresidual risk of flooding. The lower floors of buildings in areas at both medium and highprobability of flooding should seek to develop water-compatible and less vulnerable landuses, including car parks or other public areas.

River Defence Floodplain

Predicted 1% flood level. Fully inundates thefloodplain, as shown on Flood Zone Map

Lowerresidualrisk area

River Defence Floodplain

Level inferred by Flood ZoneMap

Level calculated from breachor overtopping modelling



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Housing developments (more vulnerable development) should provide a minimumhabitable space floor level above the estimated 1% year water level with the addition ofallowances for modelling uncertainty and climate change (i.e. freeboard). This may beachieved by providing car parking or other public areas at ground floor level.

Employment development (less vulnerable development) should provide a similar standardof flood defence as housing developments. Within undefended or poorly defended Zone3a areas, employment development should remain dry during the 1% event (or breachscenario where defences are in poor condition), with sufficient freeboard to account foruncertainties in flood level prediction and climate change. Developers will need tocarefully consider the commercial viability of developing in these areas. In exceptionalcircumstances, where there is significant planning justification for development and theprovision of this standard of defence is not feasible, a greater acceptance of flood risk maybe permitted for less vulnerable development in areas of high probability of flooding withthe focus on providing safety to occupants, flood proofing and designing buildings tominimise flood damage.

Flood proofing may be considered in circumstances where there is a low probability oflimited shallow depth water entry and buildings are not subjected to severe inundationdepths. This type of construction is designed to reduce the consequences of flooding andfacilitate recovery from the effect sooner than conventional buildings.

This may be achieved “through the use of water-resistant materials for floors, walls andfixtures and the siting of electrical controls, cables and appliances at a higher than normallevel.” and flood resistant construction to either reduce the amount of water or prevententry of water into a building where resistant techniques are used. A means of safe accessand egress in times of flooding must be provided, especially when considering those withrestricted mobility.

Further information on resistance and resilience techniques is provided by Defra in theirrecent publication titled “Improving the Flood Performance of New Buildings – FloodResilient Construction” and this is available on their website.

Whilst the basic level of protection afforded to residential and commercial development isthe same, it is clear that approaches to how residual risk is managed may differ betweenthese two types of developments. For residential development residual risk is a societalissue, for which a presumption of avoidance and removal is appropriate. Hence asignificant freeboard should be incorporated into housing development floor levels,whereas for a commercial property the end user and insurer can assess and transfer thisresidual risk as appropriate. Therefore commercial and employment uses have a suitablydifferent approach to the management of the residual risk, above that provided by thebasic mitigation works. The onus would be on the local authorities to determine whetherthese risks are acceptable, in conjunction with advice from the Environment Agency. PPS25 advocates a risk based approach linked to vulnerability, and does not provide aprescriptive set of flood protection standards. Wherever possible as high a standard shouldbe provided, but in exceptional circumstances, where alternative or complementary floodrisk management measures can be taken and are sustainable, a lower standard may beacceptable. Care must be taken that such an approach would not result in future publicexpenditure on retrospective flood alleviation measures. Therefore this approach isexceptional and only applicable in limited locations where the flood risks are fullyunderstood.

Isolated small greenfield developments may be sustainable in terms of their impact onfloodplain storage and conveyance, however the cumulative effects of many smalldevelopments can be large and greenfield sites must be viewed within a widerperspective.



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7.6.2 Defended Areas

Within defended areas flood risk is primarily associated with overtopping and breach ofdefences (and localised flooding associated with drainage systems in some locations).These risks are related to the likelihood (standard of protection and structural integrity ofdefences) and consequences of flooding (depth, speed and duration of flooding, velocityof flood waters, and land use within defended area).

The likelihood of overtopping can be estimated by comparison of modelled water levels(where available) and defence crest levels. An indication of the likelihood of defencebreach can be gained by reviewing the flood defence condition data held within theNational Flood and Coastal Defence Database (NFCDD), as discussed in Section 5 of thisreport, and more detailed surveys and investigations undertaken by the EnvironmentAgency and/or others. The consequences of defence overtopping or breach failure canbe estimated using flood inundation modelling and mapping.

For developments to proceed it must also be shown that the development will not increaseflood risk elsewhere through a loss of breach storage or conveyance.

7.6.3 Overtopping

Where assessments show an area to be at risk of defence overtopping in the 1% event (withclimate change), measures should be employed to mitigate the risk. Where floor levelraising is the preferred mitigation technique, minimum floor levels for housing developmentsshould be set above the estimated water level that would result behind the defences (withan allowance for uncertainty and climate change). In exceptional circumstances, wherethere is significant planning justification for development and the provision of this standardof risk mitigation is not feasible, a lower degree of flood risk mitigation may be permitted inemployment developments with the focus on providing safety to occupants, flood proofingand designing buildings to minimise flood damage.

Assuming it can be demonstrated that occupants remain safe a maximum inundationdepth of 0.6 m may be considered appropriate for the 1% event with the addition ofallowances for modelling uncertainty and climate change. Minimum floor levels may belower than the main river level if the floodplain is large.

Where the defences consist of earth embankments, overtopping of the defences is likely tolead to erosion and weakening of the defence structure. In these circumstances failure ofthe defences is considered highly probable and an assessment of the consequences ofdefence breach is also required.

7.6.4 Breach

Where the defences are shown to be at risk of overtopping and/or NFCDD data oradditional information indicate that the flood defences are in poor or very poor condition,for the purposes of the SFRA it may be assumed that there is a reasonable likelihood ofdefence breach in a major flood event during the lifetime of any new development. A highdegree of flood risk mitigation needs therefore to be provided or it may be that due to thehigh risk, the location is deemed to be unsuitable for development. If mitigation measuresare acceptable, then minimum floor levels in housing developments should be set abovethe estimated maximum breach water level for the 1% event with allowance for climatechange and other uncertainties.

In locations where the defence is of a high standard, both in terms of stability and height,then the probability of a breach occurring is reduced and hence the risk reduces as well.The overall probability of the consequences associated with a breach occurring extend tothe extreme end of the risk continuum. This does allow a more considered approach toresidual risk, and some flooding of non-sensitive or vulnerable developments may beconsidered acceptable.



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Where the defences are shown to provide a standard of protection greater than the 1%event (with climate change), NFCDD data indicate that the defences are in good or verygood condition, and there is an absence of detailed survey data to suggest otherwise, forthe purposes of the SFRA it may be assumed that the likelihood of defence failure in a majorflood event is low. With the defences mitigating risk substantially, a lesser degree of site-based flood risk mitigation may be adopted, with the focus on providing safety to thedevelopment and its occupants from residual risks. Assuming it can be demonstrated thatoccupants remain safe, for housing developments it is recommended that minimum floorlevels be set to the maximum breach level for a 1% event less 300 mm, or 600 mm abovenatural surface level, whichever is greater.

A maximum inundation depth of 0.6m may be considered acceptable when combinedwith the 1% (1 in 100 yr) event and a breach in these well defended areas in employmentdevelopments under these circumstances after consideration of uncertainty and climatechange has been added to the minimum floor levels. However, occupants and users stillneed to remain safe. Identification of the rapid inundation zone is essential in thesecircumstances, before deploying a relaxation of the residual risk accepted within thedesign. In comparison to residential areas, where societal risks are generally designed out, itis considered appropriate to possibly transfer these residual risks via insurance or resilience inthe design of the commercial use, if the users of the site can remain safe.

The effects of land raising within defended areas on potential breach risk also warrantscareful consideration in the flood risk assessment. In confined floodplains where breachlevels approach those in the main river, land raising is unlikely to have any impact onbreach water levels and extents. However, where the floodplain is not confined by naturalhigh ground or secondary defences, or where the passage of breach floodwater isrestricted by partial barriers such as road or rail embankments, and consequently breachlevels do not approach the main river level, then there is potential for land raising to lead toan increase in flood risk (extent and depth of breach) elsewhere. The potential forincreasing breach related flood risk elsewhere is directly related to the loss of breachstorage volume and conveyance, and single, small-scale developments are unlikely tohave a significant impact. However, the cumulative effect of individual developmentproposals needs to be considered. Quantitative assessment of these effects may requiredetailed breach modelling to be undertaken in individual flood risk assessments. Thisguidance is not restricted to Zone 3a and applies to any site that is located with adefended area that is at risk of flooding from defence failure.

7.6.5 Public Safety and Rapid Inundation

For all Zone 3a allocations, and particularly in defended areas where a development site isclose to a defence (i.e. within 500m), consideration must be given to residual risks and therisk to public safety associated with access and egress from properties. Residual risks arethose associated with very low likelihood events, such as events of frequency less than 1%annual exceedance probability and failure of defences where defences provide a highstandard of protection.

Development should not be sited where these risks unduly threaten public safety and/or thestructural integrity of buildings and infrastructure. Early discussion with the EnvironmentAgency, LPA and County Emergency Planning Officer is required in the consideration of thedepth of flooding, flow velocity, rate of inundation and safe access / egress to assess theserisks. This assessment is particularly applicable to areas at risk from both breach andovertopping.

There is a range of research and guidance available on flood hazards and public safety.DEFRA / Environment Agency Flood and Coastal Flood Defence Research andDevelopment Programme, Project FD2317, Flood Risks to People consolidates flood hazardresearch from many sources.

The most recent flood hazard formula proposed by Phase 2 of the Risks to People Project is:



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Flood hazard = d (v+0.5) +DF

Where:

d is depth m

v is velocity ms-1

DF is the debris factor with a value of 0-1

A number of flood hazard thresholds have been identified describing a flood hazard as“Dangerous for some”, “Dangerous for most” and “Dangerous for all”. At present the lowerthreshold for “dangerous for some” of 0.75 is appropriate with a conservative upperthreshold of 1.5. The threshold of 2.5 for “Dangerous to all” has been set with a lessconservative view and it should be noted that hazard is not purely a function of flooddepth. Flood hazard thresholds are shown in Table 7-1 below.

Table 7-1: Flood Hazard Thresholds

Flood Hazard d(v+0.5)+DF Description Alternative Name / HazardClass

0 Safe (dry) None

0 to 0.75 Caution Low

0.75 to 1.5 Dangerous for some Moderate

1.5 to 2.5 Dangerous for most Significant

Over 2.5 Dangerous for all Extreme

For the purpose of the SFRA it is considered appropriate to provide a low hazardenvironment in access and egress routes associated with new housing developments.Environment Agency guidance suggests that all development should have a dry accessand egress in the 1% event. This should be the aim, but in exceptional circumstances a lowhazard condition may be acceptable if the flood warning is robust and occupants remainsafe. Greater depth and velocity may be permitted where elevated and safe access /egress to safe ground are provided.

7.7 Other Known Flood Risk Areas Including Internal Drainage Districts

Sites that are situated upstream of an area that is known to be susceptible to localisedflooding (e.g. as a result of problematic surface water drainage) must be managedeffectively to ensure that the impact upon downstream properties is fully mitigated.Wherever possible, this should be achieved through the implementation of a sustainabledrainage or flow retention system, constructed within the boundaries of the developmentsite.

The capacity of drainage infrastructure is often limited and at or near capacity underexisting conditions. Development that leads to increased peak runoff within the drainagecatchments may lead to infrastructure capacity being exceeded, with the potential forincreased flood risk. In adopting the precautionary approach it is therefore consideredprudent to manage all development within Internal Drainage Districts (IDDs), to ensure peakdischarges do not increase and potential impacts on downstream properties are fullymitigated. Wherever possible, this should be achieved through the implementation of asustainable drainage or flow retention system, constructed within the boundaries of thedevelopment site. Early discussion is needed with the Environment Agency and the InternalDrainage Board (IDB) where appropriate.

A flood risk assessment will be required in each instance to design appropriate mitigationmeasures and demonstrate that the development will not adversely affect existing floodingconditions. The FRA should define and address the constraints that will govern the design ofthe drainage system.



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The effectiveness of a flow management scheme within a single site is heavily limited by siteconstraints including (but not limited to) topography, geology (soil permeability), andavailable area. The design, construction and ongoing maintenance regime of such ascheme must be carefully defined, and a clear and comprehensive understanding of thecatchment hydrological processes (i.e. nature and capacity of the existing drainagesystem) is essential. In these areas a flood risk assessment will be required that demonstratesthat the proposed development will not adversely affect existing flooding conditions.

Prior to the planning application stage, discussions should be held with the EnvironmentAgency, LPA, IDB and Water Company to ascertain the specific nature and mostappropriate means of managing the flood risk.

The integration of drainage management is highlighted within the Defra strategy for floodand coastal erosion risk management in England, detailed within the consultationdocument ‘Making space for Water’. As discussed in Section 2.2.2 of this report, thestrategy aims to achieve better overall management of surface water drainage throughbetter co-ordination between the different bodies.

Only the south east area of Wakefield District Council is covered by an IDD in the CalderValley. The Went and Dun IDD are included within the Shire Group IDB, covering thesettlement of Ackworth Moor Top, East Hardwick, Thorpe Audlin and South Elmsall.

Where development is proposed in these locations or may impact upon its drainage, theShire Group IDB should be consulted in each instance to ensure the development iscompatible with all drainage systems. There may be instances where additional drainagesystem capacity is available and increased peak runoff is acceptable, but these areas areexceptional, can only be identified by the relevant IDB and development proposals will stillrequire a detailed flood risk assessment.



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8 CONCLUSION

8.1 Overview of SFRA Outcomes

Calderdale MBC, Kikrlees MBC and Wakefield MDC are embarking on the development ofLDFs to replace their existing UDPs. Amongst other things the LDF will provide a policyframework for decisions about the use and development of land. To ensure that the LDF’sfully addresses the requirements of PPS 25, this SFRA was commissioned. The SFRA will formpart of the SEA which in turn will feed into the SA of the forthcoming LDF. As part of theappraisal the results of the SFRA can be used as an indicator to determine the sustainabilityof policies and allocations. The use of the word ‘sustainable’ within the SFRA is inconnection with flood risk only. An individual application will need to address otherplanning issues to be considered sustainable.

The majority of these three districts are located with the River Calder catchment. With floodprocesses and flood risk issues across the districts inextricably linked by the River Calder andits many tributaries the councils took the wise decision to undertake a joint SFRA. Thisprovided efficiency in understanding flood processes and flood issues, and allowed forimproved and integrated consideration of inter-district flood risk linkages.

This SFRA has taken a step forward from the original SFRA created by JBA under PPG 25 in itsreview of flood risk, to take account of recent guidance and approaches in PPS 25. Firstly,flood zones have been updated and mapped across the district to provide a broad-scale,high level filter for assessing flood risk in developing areas. In combination with the genericpolicies set out throughout the SFRA these maps allow for consistent assessment of flood riskand the adoption of sustainable allocations supported by PPS 25.

Secondly, this SFRA provides additional information and has been able to develop theunderstanding of flood risk throughout each council area by providing a suite of SFRA floodrisk maps, which include:

• Fluvial Flood Extent and Depth Maps

• Areas Naturally Vulnerable to Surface Water Flooding Maps

• Climate Change Sensitivity Maps

These maps along with the Environment Agency Flood Maps supply the detail andunderstanding of flood risk across the councils, providing the level of detail needed toassess current and future allocations in line with PPS 25.

The councils are now able to implement the Sequential Test as a sieving process to avoidinappropriate development in high risk zones. Where this may not be possible due to widersocial and economic reasons, substitution of more appropriate development would beappropriate. After the many repetitions of the Sequential Testing and sites have beenidentified as requiring the Exceptions Test, the SFRA Flood Risk Maps can be used to gain abetter understanding of the likelihood of sites passing the test and the level of appropriatemitigation need to make to site safe.

It is highlighted that there are a range of national and regional planning policy which LPAsmust consider in the allocation of land for development. PPS 25 is only one of these policiesand is not considered to preclude development within flood risk areas. Where the risk isconsidered unacceptably high however, the exclusion of development may be deemed tobe the only sustainable solution. As discussed the SFRA process is a journey, which involvesmany iterations of the Sequential Test. This SFRA follows the whole journey without being



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distracted by the justification of the development under wider drivers which will beconsidered in the SA. Hence, a discussion and consideration of mitigation measures isincluded in the SFRA.

When allocating land in development plans or deciding applications for development atany particular location, those responsible for the decision would be expected todemonstrate through the SEA and SA in combination that there are no reasonable optionsavailable in a lower-risk category consistent with other sustainable development objectives.Only once this process has been undertaken can land within the flood zones be consideredfor development. No allocations for built development will be permitted in Zone 3b apartfrom water compatible or essential infrastructure when justified by the Exceptions Test.Development within Zone 3a will only be allowed by the Environment Agency underexceptional circumstances. Climate Change will increase the probability of flooding in thefuture and as a result land within High Risk Zone 3 should be safeguarded from developmentwhere possible, to obviate the need to return at a later date to upgrade its standard offlood protection.

These are all elements that will need to be considered in the delivery of the Exception Test,but an SFRA needs to be suitably precautionary, applying a longer term holistic approachto ensuring development does not compromise future flood management measures andvice versa. Where the council have identified those sites which are required to provide longterm social and economic sustainability this SFRA has introduced a number of indicatorsalong with a flood risk balance sheet. The flood risk balance sheet allows a simplesequential approach assessment to be delivered against flood risk criteria and a hierarchyof recommended land uses and how they would fare within the PPS 25 Exceptions Test. Thislevel of assessment would support appropriate policies and would provide the evidence forthe LPA in reviewing any subsequent planning applications that decide to use theException Test to justify the need for alternative land uses in these areas.

Where uncertainty exists in the broad datasets describing flood risk a precautionaryapproach was taken, and in these circumstances there is merit in more detailedassessments within the context of a FRA.

However, for the spatial decision making to be consistent the information in the SFRA issufficient to apply the Sequential Test. Continued use of the SFRA, engagement of theplanning and emergency planning teams through SFRA Masterclasses will ensure that floodrisk is considered with the appropriate weight and scale throughout the planning cycle. Itshould be noted that the previous workshops raised awareness, but continuedreinforcement and re-education of new users of these documents is recommended

8.2 Level 2 SFRA

The Level 1 assessment contained herein identifies where it would be appropriate for eachcouncil to undertake a level 2 SFRA. These more detailed assessments would concentrateon specific locations where flood risk has been identified as a critical issue but developmentis still required to meet the wider sustainable objectives.

For those sites identified will need to follow the Exception Test criteria and assess whether thesites or allocations would in all likelihood pass the Test and be deliverable. The test is asfollows:

a) It must be demonstrated that the development provides wider sustainability benefitsto the community that outweigh flood risk, informed by a SFRA where one has beenprepared. If the LDD has reached the ‘submission’ stage (see Figure 4.1 of PPS 12:Local Development Frameworks) the benefits of the development should contributeto the Core Strategy’s Sustainability Appraisal (SA);

b) The development must be on developable previously-developed land or, if it is noton previously-developed land, that there are no reasonable alternative sites ondevelopable previously-developed land; and



73

c) A site-specific Flood Risk Assessment must demonstrate that the development will besafe, without increasing flood risk elsewhere, and, where possible, will reduce floodrisk overall.

A level 2 SFRA will help provide the next stage of information and will further collate theevidence base within each LDF to facilitate the application of the Exception Test. Theinvestigations carried out within the level 2 SFRA will inform the flood risk balance sheet andconfirm the sequential approach to site layout and the design of possible mitigationmeasures.

Suggested level 2 SFRA locations include but are not limited to:

• Sowerby Bridge/Halifax

• Kirklees Strategic Economic Zone – Aspley to Cooper Bridge

• South Dewsbury area

• Central Wakefield – Level 2 SFRA completed in May 2008

• Castleford - Comprehensive FRA undertaken for Hickson and Welch site, whichaddressed a number of strategic issues

8.3 Surface Water Management Plans

Surface water flooding is a major source of flood risk and as demonstrated by the summer2007 floods can lead to serious flooding of property and possessions.

Surface Water Management Plans (SWMP), introduced in PPS 25 and more recently withinthe Pitt Review, are being discussed as playing an important and crucial role in managingsurface water flooding and reducing overall flood risk, both for existing and newdevelopment.

It has long been recognised that there is fragmented responsibilities for managing surfacewater drainage. By developing a shared understanding of local flood risks, prioritisation ofactions, maintenance needs and links into local development frameworks and emergencyplans, SWMPs could provide a much needed co-ordination mechanism helping mitigateand reduce flood risk to local communities. SWMPs also have the wider opportunity toreduce clean-up costs and improve water quality.

Their concept are imbedded in the Governments new Water Strategy, Future Water7, settingout a vision for more effective drainage of surface water, in order to deal with the duelpressures of climate change and housing development.

In order to achieve this, SWMPs should:

• Map and quantify surface flows and drainage with sufficient detail to enable localas well as strategic flooding problems to be tackled;

• Produce a delivery plan that clarifies responsibilities and then directs resources attackling surface water, prioritising areas at greatest risk first;

• Influence local planning policy such that new development occurs primarily in areasof low surface water flood risk8 or where flood risk can be managed effectively,making use of sustainable drainage solutions where appropriate; and

• Be periodically reviewed, possibly including independent scrutiny of planning andresource decisions to gauge progress in tackling the most serious problems.

The evidence supplied within this SFRA has identified those areas which are naturallyvulnerable to surface water flooding by providing a suite of vulnerability maps. These maps,along with areas know to be sensitive to climate change and have high development



74

pressures, should give each council an indication of locations which would benefit from aSWMP.

Using the information provided, suggested SWMP locations include but are not limited to:

• Sowerby Bridge

• Brighouse

• Huddersfield

• Central Wakefield including Ings Beck – as suggested within the Draft Calder CFMPand noted in the Level 2 SFRA

• Castleford

• Pontefract (in conjunction with the flood alleviation scheme currently beingassessed by the EA)

A detailed practice guide on SWMPs will be produced within Defra’s Water Strategy and isdue for publication in Autumn 2008, where delivery of SWMPs should be planned for 2010.

Until a SWMP has been completed, all developments should adhere to the guidance in PPS25 and the recommendations outlined in Section 7 in this SFRA, in particular the use of SuDs.Integrated drainage solutions should be prepared for larger sites or areas.

8.4 Guidance for Development Control

It must be made clear that this SFRA does not preclude the need for site specific flood riskassessments. Site specific flood risk assessments will be required for all development withinZones 2 and 3, and for all development with the catchment of a Critical OrdinaryWatercourse (COW) or Internal Drainage District (IDD). A full FRA will also be required for alloperational development greater than 1ha in size in Zone 1, for smaller sites a ScreeningStudy will determine whether further assessment is required.

This SFRA has identified flood risk areas i.e. Zone 1, 2, 3a and 3b using the EnvironmentAgency Flood Map and provided further SFRA Flood Risk Maps. Former COWS and IDDareas have also been mapped within each district area in order to facilitate therequirement for FRA in these locations. The primary objective of the FRA should be todemonstrate adherence to policy requirements surrounding flood risk, as defined by therecommendations of the SFRA.

In line with the Environment Agency standing advice for development and flood risk, FRA’swill also be required for operational development greater than 1ha within Zone 1. The FRAwill be required to demonstrate that it will be feasible to balance surface water runoff to thegreenfield runoff rate up to the 1 in 100 years event. LPAs may also require a minimumdesign for drainage systems for example to be able to cope with a 1:30 year event. Theymay also require that this includes the balancing of the predicted climate change volume,which will also need to be agreed with the LPA and tackled within the FRA. However, itmust be acknowledged that in specific circumstances, attenuation to greenfield runoff ratemay not be achievable, which would need to be dealt with through a site specific FRA.Sustainable drainage techniques (SuDs) will have to be investigated and any obstacles tothe use of SuDs will need to clearly justified within the FRA.

PPS 25 provides some guidance with respect to the preparation of site-based FRA in AnnexE. A pragmatic and risk-based approach should be taken to the preparation of a FRA,commensurate to the degree of flood risk posed to (and/or by) development of the site.The detail included within the FRA should follow the Flood Response matrix included in thecurrent standing advice from the Environment Agency (see www.pipernetworking.com), theguidance provided by the CIRIA Report C624 (Development and flood risk – guidance forthe construction industry) and the guidance provided in this SFRA in Section 7.

The Environment Agency standing advice has been produced to enable LPAs in England tomake decisions on low risk planning applications where flood risk is an issue without directly



75

consulting the Environment Agency for an individual response. In the instance wheredevelopment sites lie with former COW, IDD areas or other sensitive areas the FRA should bediscussed with the relevant body such as the Internal Drainage Board, sewerageundertakers, highways authority and reservoir owners and operators prior to application.This SFRA has provided a map identifying former COWs and IDD to facilitate this process.The Environment Agency standing advice also identifies those higher risk developmentsituations where case by case consultation with the Agency should continue.

Flood Risk Assessment Notes (FRAN) also provided as part of the Environments Agency’sstanding advice provides advice on general topics to do with flood risk potential that arenot fully included within the SFRA as well as covering topics covered in more detail withinthe SFRA.

The Environment Agency anticipates that the information provided within the SFRA will feeddirectly into FRAs. Floor levels/inundation depths suggested by the SFRA should be taken asa starting point. Further investigation as part of the individual FRAs could reveal moreaccurate data and floor levels should be set around these calculations and modelling andnot that provided by the SFRA.

8.5 Monitoring

This SFRA should be viewed as a ‘living’ document which should be used in the day-to-dayprocess of planning and development.

Whilst this SFRA has been produced using the most up-to-date national guidance and floodrisk data (including climate change), it is recommended that the SFRA should be updatedon a regular basis. The Environment Agency has suggested this be every 3 to 4 years, unlessthere is a significant flood affecting the areas, giving arise to new information or areas atflood risk, or there are any major national policy changes. There are key outputs from anumber of possible future studies which should be incorporated in any update. Including:

• Final version of the Calder, Aire and Don and Rother CFMP

• Flood risk mapping studies

• Flood risk management studies



76

FIGURES



77

MAPS



78

APPENDICES



79

Appendix A: - Flood Risk Zones / Flood Risk Vulnerability Classification



80

A.1 FLOOD RISK ZONES

Table A - 1: Flood Risk Zones9

Zone 1: Low ProbabilityDefinition

This zone comprises land assessed as having a less than 1 in 1000 annual probability of river and sea flooding inany year (<0.1%).

Appropriate uses

All uses of land are appropriate in this zone

FRA requirements

For development proposals on sites comprising one hectare or above the vulnerability to flooding from othersources as well as from river and sea flooding, and the potential to increase flood risk elsewhere through theaddition of hard surfaces and the effect of the new development on surface water run-off, should beincorporated in an FRA [Flood Risk Assessment]. This need only be brief unless the factors above or other localconsiderations require particular attention. See Annex E (of PPS 25) for minimum requirements

Policy aims

In this zone, developers and local authorities should seek opportunities to reduce the overall level of flood risk inthe area and beyond through the layout and form of the development and the appropriate application ofsustainable drainage techniques.

Zone 2: Medium Probability

Definition

This zone comprises land assessed as having between a 1 in 100 and 1 in 1000 annual probability of river flooding(1% – 0.1%) and between a 1 in 200 and 1 in 1000 annual probability of sea flooding (0.5% – 0.1%) in any year.

Appropriate uses

The water-compatible, less vulnerable and more vulnerable uses of land and essential infrastructure listedin…[the Flood Risk Vulnerability Classification, see Table A-2] are appropriate in this zone.

Subject to the Sequential Test being applied, the highly vulnerable uses in Table D.2 (of PPS 25 and Table B-2 ofthis report) are only appropriate in this zone if the Exception Test is passed

FRA requirements.

All development proposals in this zone should be accompanied by a FRA,. See Annex E (of PPS 25) for minimumrequirements

Policy Aims

In this zone, developers and local authorities should seek opportunities to reduce the overall level of flood risk inthe area through the layout and form of the development and the appropriate application of sustainabledrainage techniques.

Zone 3a: High Probability

Definition

This zone comprises land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%) and a1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year.



81

Appropriate uses

The water-compatible and less vulnerable uses of land listed in Table D.2 (of PPS 25 and Table A-2 of this report)are appropriate in this zone.

The highly vulnerable uses listed in Table D.2 (of PPS 25 and Table A-2 of this report) should not be permitted inthis zone.

The more vulnerable and essential infrastructure listed in the Table D.2 (of PPS 25 and Table B-2 of this report)should only be permitted in this zone if the Exception Test is passed. Essential Infrastructure permitted in this zoneshould be designed and constructed to remain operational and safe for user in times of flood.

FRA requirements

All development proposals in this zone should be accompanied by a FRA, See Annex E (of PPS 25) for minimumrequirements.

Policy Aims

In this zone, developers and local authorities should seek opportunities to:

i. reduce the overall level of flood risk in the area through the layout and form of the development and theappropriate application of sustainable drainage techniques;

ii. relocate existing development to land in lower Flood Zones; and

iii. Create space for flooding to occur by restoring functional floodplain and flood flow pathways and byidentifying, allocation and safeguarding open space for flood storage.

Zone 3b: The Functional Floodplain

Definition

This zone comprises land where water has to flow or be stored in times of flood. SFRAs should identify this FloodZone (land which would flood with an annual probability of 1 in 20 (5%) or greater in any year or is designed toflood in an extreme (0.1%) flood, or at another probability to be agreed between the LPA and the EnvironmentAgency, including water conveyance routes).

Appropriate uses

Only the water-compatible uses and the essential infrastructure listed in Table D.2 (of PPS 25 and Table B-2 of thisreport) that has to be there should be permitted in this zone. It should be designed and constructed to

– remain operational in times of flood;

– result in no net loss of floodplain storage;

– not impede water flows; and

– not increase flood risk elsewhere.

Essential infrastructure in this zone should pass the Exception Test.

FRA requirements

All development proposals in this zone should be accompanied by a FRA,. See Annex E for minimumrequirements.

Policy aims

In this zone, developers and local authorities should seek opportunities to:

i. reduce the overall level of flood risk in the area through the layout and form of the development and theappropriate application of sustainable drainage techniques; and

ii. Relocate existing development to land with a lower probability of flooding.

Note 1: These Flood Zones refer to the probability of river and sea flooding ignoring the presence of defences



82

A.2 FLOOD RISK VULNERABILITY CLASSIFICATION

Table A - 2: Flood Risk Vulnerability Classification

Classification DescriptionEssential Infrastructure • Essential transport infrastructure (including mass evacuation routes) which has to cross the

area at risk and strategic utility infrastructure, including electricity generating powerstations and grid and primary substations.

Highly Vulnerable • Police stations, Ambulance stations and Fire stations and Command Centres andtelecommunications installations required to be operational during flooding.

• Emergency dispersal points.

• Basement dwellings.

• Caravans, mobile homes and park homes intended for permanent residential use.

• Installations requiring hazardous substances consent (1)

More Vulnerable • Hospitals.

• Residential institutions such as residential care homes, children’s homes, social serviceshomes, 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. (2)

• Sites used for holiday or short-let caravans and camping, subject to a specific warmingand evacuation plan

Less Vulnerable • Buildings used for: shops; financial, professional and other services; restaurants and cafes;hot food takeaways; offices; general industry; storage and distribution; non–residentialinstitutions not included in ‘more vulnerable’; 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 plants.

• Sewage treatment plants (if adequate pollution control measures are in place).

Water-compatibleDevelopment

• Flood control infrastructure.

• Water transmission infrastructure and pumping stations.

• Sewage transmission infrastructure and pumping stations.

• Sand and gravel workings.

• Docks, marinas and wharves.

• Navigation facilities.

• MOD defence installations.

• Ship building, repairing and dismantling, dockside fish processing and refrigeration andcompatible activities requiring a waterside location.

• Water-based recreation (excluding sleeping accommodation).



83

Table A - 2: Flood Risk Vulnerability Classification

Classification Description• Lifeguard and coastguard stations.

• Amenity open space, nature conservation and biodiversity, outdoor sports and recreationand essential facilities such as changing rooms.

• Essential ancillary sleeping or residential accommodation for staff required by uses in thiscategory, subject to a specific warning and evacuation plan.

Note 1: This classification is based on advice from the Environment Agency on the flood risks to people and the need ofsome uses to keep functioning during flooding.Note 2: Buildings that combine a mixture of uses should be placed into the higher of the relevant classes of flood risksensitivity. Developments that allow uses to be distributed over the site may fall within several classes of flood sensitivity.

(1)DETA Cicular 04/00 – para. 18: Planning controls for hazardous substances.www.communities.gov.uk/index.asp?id=1144377(2)See Planning for Sustainable Waste Management: Companion Guide to Planning Policy Statement 10 for definition.www.communities.gov.uk/index.asp?id=1500757

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87

Appendix C: - LPA Flood Zone 3b Confirmation Letters



88

C.1 LPA FLOOD ZONE 3B CONFIRMATION LETTERS

Calderdale Council

From: Phil RatcliffTo: Chris IsherwoodSubject: SFRA - CaderdaleSent: 04/11/2008

Chris,

Thanks for holding off on the SFRA. I confirm that we have resolved all the little difficultiesand I agree that the SFRA is now signed off as far as Calderdale Council is concerned.

Many thanks for all the work over the past months,

Best wishes,

Phil Ratcliffe

Kirklees Council

From: Patrick AutersonTo: Amy HeysSubject: SFRA Functional Flood plainSent: 30/10/2008

Amy

We have agreed a number of amendments with Chris Isherwood to the FFP plan hesupplied on 6 October. I can confirm that the FFP with these amendments is acceptable toKirklees Council.

I hope to be in touch in the near future about the sequential test for development proposalsin south Dewsbury, as discussed on the phone some weeks ago.

Patrick Auterson

Gateshead Council

From: Peter GoodingTo: Amy HeysSubject: Calder SFRA Final Draft – Functional FloodplainSent: 09/10/2008

Amy,

I have today checked the latest SFRA flood zones plan of Wakefield District incorporatingfunctional floodplain v6.08.10, which was received from JBA yesterday, and can confirmthat as far as Wakefield officers are concerned the relationship of the functional floodplainwith the urban area as shown provides a reasonable basis for the application of guidance



89

in PPS25. In addition I agree with your view regarding sewage treatment works andfunctional floodplain and the need for the zone boundaries to be as detailed as possible.

Peter Gooding



90

REFERENCES



91

References

1 Defra (2005) Making Space for Water: Developing a new Government Strategy for Flood &Coastal Erosion Risk Management in England London: Defra

2 Communities and Local Government (2006) Planning Policy Statement (PPS) 25 Development andFlood Risk

3 Communities and Local Government (2008) Planning Policy Statement (PPS) 25 Development andFlood Risk Practice Guide

4 Cabinet Office (2008) The Pitt Review: Lesson Learnt from the 2007 Floods

5 Communities and Local Government. 2006. Planning Policy Statement: Planning and ClimateChange. December 2006.http://www.communities.gov.uk/documents/planningandbuilding/pdf/153119

6 Environment Agency (2006) Strategic Flood Risk Management Specification for Flood RiskMapping. Release 1.2. August 2006

7 Foresight (2008) Future Flooding.http://www.foresight.gov.uk/Previous_Projects/Flood_and_Coastal_Defence/index.html

8 Defra (2006) Scoping study: Integrated Urban Drainage Pilots,http://www.defra.gov.uk/environ/fcd/policy/strategy/scoperev.pdf

9 Communities and Local Government. 2006. Planning Policy Statement 25: Development andFlood Risk. December 2006.http://www.communities.gov.uk/pub/955/PlanningPolicyStatement25DevelopmentandFloodRisk_id1504955.pdf