Strategic Flood Risk Assessment (SFRA)
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Elmbridge Borough Council Level 1 Strategic Flood Risk Assessment (SFRA) May 2015 47069767 UNITED KINGDOM & IRELAND Prepared for: Elmbridge Borough Council — Strategic Flood Risk Assessment REVISION SCHEDULE Rev Date Details Prepared by Reviewed by Approved by 1 May 2014 1st Draft Sarah Littlewood Sarah Kelly Jon Robinson Consultant Principal Consultant Operations Director Edward Byers Tom Hargreaves Consultant Associate Director Neil Mackenzie Principal Hydrogeologist 2 Aug 2014 2nd Draft including Sarah Littlewood Sarah Kelly Jon Robinson comments from Consultant Principal Consultant Operations Director Elmbridge BC and Environment Agency 3 Dec 2014 Final Draft Report Sarah Littlewood Sarah Kelly Michael Timmins including comments Consultant Principal Consultant Technical Director from Elmbridge BC 4 May 2015 Final Issue Sarah Littlewood Emily Craven Michael Timmins including Consultant Principal Consultant Technical Director consultation comments URS Infrastructure and Environment UK Ltd 6-8 Greencoat Place London SW1P 1PL United Kingdom Telephone: +44(0)20 7798 5000 Fax: +44(0)20 7798 5001 www.urs.com/uki FINAL REPORT 47069767 May 2015 i Elmbridge Borough Council — Strategic Flood Risk Assessment Limitations URS Infrastructure & Environment UK Limited (“URS”) has prepared this Report for the sole use of Elmbridge Borough Council (“Client”) in accordance with the Agreement under which our services were performed (‘Elmbridge Borough Council Conditions of Contract: Contract for Strategic Flood Risk Assessment SFRA 2013 (December 2013)’ and URS Quotation of Services ‘ElmbridgeBC_Quotation_of_Services_2014-01-09.pdf’). 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FINAL REPORT 47069767 May 2015 ii Elmbridge Borough Council — Strategic Flood Risk Assessment TABLE OF CONTENTS ABBREVIATIONS ................................................................................ 5 GLOSSARY OF TERMS ...................................................................... 6 1 INTRODUCTION AND USER GUIDE ............................... 8 1.1 Introduction ...................................................................... 8 1.2 Approach to Flood Risk Management ........................... 8 1.3 Purpose of the SFRA ..................................................... 10 1.4 Flood Risk Policy and Guidance .................................. 10 1.5 User Guide ...................................................................... 11 1.6 Living Document ............................................................ 13 2 METHODOLOGY ............................................................ 14 2.1 Overview ......................................................................... 14 2.2 Consultation ................................................................... 14 2.3 Data Collection ............................................................... 16 3 ASSESSING FLOOD RISK ............................................. 28 3.1 Overview ......................................................................... 28 3.2 Area ................................................................................. 28 3.3 Character ........................................................................ 29 3.4 Topography .................................................................... 29 3.5 Geology ........................................................................... 29 3.6 Aquifers .......................................................................... 30 3.7 Groundwater Vulnerability ............................................ 30 3.8 Main Rivers ..................................................................... 30 3.9 Ordinary Watercourses ................................................. 31 3.10 Flooding from Rivers ..................................................... 31 3.11 Flooding from Land ....................................................... 37 3.12 Flooding from Groundwater ......................................... 38 3.13 Flooding from Sewers ................................................... 38 3.14 Flooding from Reservoirs ............................................. 39 4 AVOIDING FLOOD RISK ................................................ 41 4.1 Sequential Approach ..................................................... 41 4.2 Applying Sequential Test – Plan-Making..................... 41 4.3 Applying Sequential Test – Planning Applications .... 45 4.4 Exception Test ............................................................... 46 5 MANAGING AND MITIGATING FLOOD RISK .............. 49 5.1 Overview ......................................................................... 49 5.2 Development Layout and Sequential Approach ......... 49 FINAL REPORT 47069767 May 2015 iii Elmbridge Borough Council — Strategic Flood Risk Assessment 5.3 Finished Floor Levels .................................................... 49 5.4 Flood Resistance ‘Water Exclusion Strategy’ ............ 51 5.5 Flood Resilience ‘Water Entry Strategy’...................... 53 5.6 Safe Access and Egress ............................................... 54 5.7 Floodplain Compensation Storage .............................. 55 5.8 Flood Routing ................................................................. 57 5.9 Riverside Development ................................................. 58 5.10 Surface Water Management .......................................... 58 5.11 Flood Warning and Evacuation Plans ......................... 62 6 GUIDANCE FOR SITE-SPECIFIC FRAS ....................... 65 6.1 What is a Flood Risk Assessment? ............................. 65 6.2 When is a Flood Risk Assessment required? ............. 65 6.3 How detailed should a FRA be? ................................... 65 6.4 What needs to be addressed in a Flood Risk Assessment? .................................................................. 67 6.5 Flood Risk Assessment Checklist ............................... 68 6.6 Pre-application Advice .................................................. 71 7 FLOOD RISK POLICY AND DEVELOPMENT MANAGEMENT APPROACH ......................................... 72 7.1 Overview ......................................................................... 72 7.2 Policy Approach ............................................................. 72 7.3 Development Management Measures .......................... 76 APPENDIX A DATA REGISTER ....................................................... 82 APPENDIX B BOROUGH SCALE MAPPING .................................. 86 APPENDIX C FLUVIAL FLOOD ZONE MAPPING ........................... 88 APPENDIX D SURFACE WATER FLOOD RISK MAPPING ........... 90 APPENDIX E SETTLEMENT AREA SCHEDULES .......................... 92 APPENDIX F SAMPLE SITE ASSESSMENTS .............................. 118 FINAL REPORT 47069767 May 2015 iv Elmbridge Borough Council — Strategic Flood Risk Assessment ABBREVIATIONS ACRONYM DEFINITION AOD Above Ordnance Datum AIMS Asset Information Management System BGS British Geological Survey CFMP Catchment Flood Management Plan CLG (Department for) Communities and Local Government Defra Department for Environment, Flood and Rural Affairs EBC Elmbridge Borough Council FRA Flood Risk Assessment FWMA Flood and Water Management Act 2010 GIS Geographical Information System LiDAR Light Detection and Ranging LLFA Lead Local Flood Authority LPA Local Planning Authority LRF Local Resilience Forum PPG Planning Practice Guidance NPPF National Planning Policy Framework RAMSAR RAMSAR Sites RTD River Terrace Deposits S&G Sand and Gravel SCC Surrey County Council SFRA Strategic