YORK CITY OF YORK Strategic Flood Risk Assessment Revision 2 (March 2013) City of York Council Strategic Flood Risk Assessment Revision 2: March 2013 City of York Council Strategic Flood Risk Assessment Integrated Strategy Unit: Flood Risk Management Revision 2 : March 2013 Contents GLOSSARY ............................................................................................................................... 5 ABBREVIATIONS ...................................................................................................................... 7 EXECUTIVE SUMMARY ........................................................................................................... 8 1 INTRODUCTION .............................................................................................................. 13 1.1 Background ................................................................................................................... 13 1.2 Purpose of the Assessment .......................................................................................... 14 1.3 Contents ........................................................................................................................ 14 2 BACKGROUND ................................................................................................................ 16 2.1 River Network ............................................................................................................... 16 2.2 Broad Physical Characteristics ..................................................................................... 17 2.3 Topography, Geology, Soils and Hydrogeology ........................................................... 17 2.4 Existing Flood Defences ............................................................................................... 18 2.5 Climatic Change Influences on Flooding ...................................................................... 18 2.6 Policy Background ........................................................................................................ 19 2.7 European Context ......................................................................................................... 19 2.8 National Context ........................................................................................................... 20 2.9 Risk-Based Approach ................................................................................................... 20 2.10 The Sequential Test ...................................................................................................... 21 2.11 Exception Test .............................................................................................................. 21 2.12 Taking climate change into account.................... .................... .....................................24 2.13 Strategic and Local Planning Context .......................................................................... 24 2.14 EA Development and Flood Risk Report ...................................................................... 25 2.15 EA Standing Advice: Development & Flood Risk (England) ........................................ 26 2.16 Current Environment Agency Flood Policy ................................................................... 26 2.17 City of York Council Duties as Lead Local Flood Authority .......................................... 26 3 FLOOD RISK IN YORK – KEY ISSUES .......................................................................... 27 3.1 The River and Watercourse Network ........................................................................... 27 2 City of York Council Strategic Flood Risk Assessment Integrated Strategy Unit: Flood Risk Management Revision 2 : March 2013 3.2 Flood Risk Zones .......................................................................................................... 28 3.3 City of York Council’s Emergency Planning – Flood Risk ............................................ 30 3.4 Rapid Inundation Zones (RIZ) ...................................................................................... 30 3.5 Flood Depth Mapping ................................................................................................... 34 3.6 Climatic Change Influences on Flooding ...................................................................... 35 3.7 Freeboard Allowance .................................................................................................... 36 3.8 River Ouse .................................................................................................................... 36 3.9 River Foss ..................................................................................................................... 48 3.10 River Derwent ............................................................................................................... 52 4 APPROACH TO FLOOD RISK ........................................................................................ 56 4.1 Policy Recommendations and Development Management Guidance ......................... 56 4.1.a Policy Recommendations for Forward Planning ........................................................... 56 4.1.b Guidance for Development Management and the Consideration of Planning Applications ............................................................................................................................. 71 4.1.c General Surface Water Drainage Guidance ................................................................. 81 4.2 Specific Comments on Development in High Risk Flood Zone 3 Areas ...................... 84 5 THE SEQUENTIAL TEST AND EXCEPTION TEST ....................................................... 86 5.1 The Sequential Test and Exception Test for Forward Planning ................................... 86 5.2 The Sequential Test and Exception Test for Development Management .................... 88 APPENDIX 1: SOURCES OF INFORMATION ....................................................................... 93 APPENDIX 2: CONSULTEES ................................................................................................. 94 APPENDIX 3: CITY OF YORK DRAFT LOCAL PLAN INCORPORATING THE 4TH SET OF CHANGES – DEVELOPMENT CONTROL LOCAL PLAN: APPROVED APRIL 2005. .......... 95 APPENDIX 4: CITY OF YORK COUNCIL LOCAL DEVELOPMENT FRAMEWORK CORE STRATEGY DRAFT SUBMISSION (MARCH 2011). .............................................................. 97 3 City of York Council Strategic Flood Risk Assessment Integrated Strategy Unit: Flood Risk Management Revision 2 : March 2013 Figures (Please see accompanying map booklet) Figure 1: Main River and Tributary Network in York Figure 2: River Ouse and Foss Catchment Boundaries (in body of the report) …..................................100 Figure 3: River Derwent Catchment Boundary (in body of the report)…….………............................…..101 Figure 4: Internal Drainage Board Boundaries Figure 5: River Ouse Yearly Maximum Flood Levels Figure 6: River Zones in York Figure 7: Existing York Flood Defences Figure 8: Environment Agency Flood Zones Figure 9: Local Plan Map Extracts Figure 10: Flood Risk Areas within Zone 1, 2 & 3 (key plan) Figure 10a: Flood Risk Areas within Zone 1, 2 & 3 – North Figure 10b: Flood Risk Areas within Zone 1, 2 & 3 – South Figure 10c: Flood Risk Areas within Zone 1, 2 & 3 – City Centre Figure 11: Plan view of Danger to People from Breach Scenario (in body of report)………….....33 Figure 12: Sectional view of Danger to People from Breach Scenario (in body of Report……….33 Figure 13: Flooded Domestic Properties in 2000 – Key Plan Figure 13a: Flooded Domestic Properties in 2000 – Rawcliffe Figure 13b: Flooded Domestic Properties in 2000 – City Centre and Clementhorpe Figure 13c: Flooded Domestic Properties in 2000 – Fulford Figure 13d: Flooded Domestic Properties in 2000 – Bishopthorpe Figure 13e: Flooded Domestic Properties in 2000 – Naburn and Acaster Malbis Figure 13f: Flooded Domestic Properties in 2000 – Elvington Tables Table 2.1: Technical Guidance on the National Planning Policy Framework (TG) Flood Zones and the Sequential Test........................................................................................................ ................................22 Table 2.2: Recommended national precautionary sensitivity ranges for peak rainfall intensities, peak river flows, offshore wind speeds and wave heights...........................................................................24 Table 3.1: Relationship between Flood Hazard and Distance Away from a Flood Defence assuming a Defence Breach (HR Wallingford, 2005) .............................................................................................. ...31 Table 3.2: Danger to People – relationship between Flood Depth and Flood Velocity assuming a Defence Breach (HR Walling ford, 2005) .............................................................................................. ..32 Table 0.1: Flood Risk Vulnerability Classification ……………………………………………………...57 Table 4.2: Flood Risk Vulnerability and Flood Zone ‘Compatibility’………………………………………... 58 Table 5.1a: Exception Test Sustainability Considerations – Forward Planning.................................. .....87 Table 5.1b: Exception Test Sustainability Considerations – Development Management ................. .......89 Table 5.2: Application of the Sequential Test ..................................................................................... .....90 Table 5.3: Environment Agency checklist