Waverley Borough Council Level 1 Strategic Flood Risk Assessment Project number: 60563228 Final November 2018 Level 1 Strategic Flood Risk Assessment FINAL Project number: 60563228 Quality information Prepared by Checked by Approved by Sarah Waite Sarah Littlewood Sarah Kelly Flood Risk Consultant Senior Flood Risk Consultant Regional Director, Water Nicole Boakye Graduate Consultant Revision History Revision Revision date Details Authorized Name Position 1 August 2018 Draft Report August 2018 Sarah Kelly Regional Director, Water 2 November 2018 Final Report incorporating November 2018 Sarah Kelly Regional Director, Water WBC, EA and SCC comments Distribution List # Hard Copies PDF Required Association / Company Name N/A Yes Waverley Borough Council Environment Agency Surrey County Council Prepared for: Waverley Borough Council Prepared by: AECOM Infrastructure and Environment UK Limited Midpoint, Alencon Link Basingstoke Hampshire RG21 7PP United Kingdom T: +44(0)1256 310200 aecom.com © 2018 AECOM Infrastructure and Environment UK Limited. All Rights Reserved. This document has been prepared by AECOM Infrastructure and Environment UK Limited (“AECOM”) for sole use of our client (the “Client”) in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM. Prepared for: Waverley Borough Council AECOM November 2018 Level 1 Strategic Flood Risk Assessment FINAL Project number: 60563228 Table of Contents 1. Introduction ...................................................................................................... 1 1.1 Background ........................................................................................................................................ 1 1.2 Approach to Flood Risk Management .................................................................................................. 1 1.3 Purpose of the SFRA .......................................................................................................................... 3 1.4 Flood Risk Policy and Guidance .......................................................................................................... 3 1.5 Report Structure .................................................................................................................................. 4 1.6 Living Document ................................................................................................................................. 5 2. Methodology .................................................................................................... 6 2.1 Consultation ........................................................................................................................................ 6 2.2 Data Collection and Mapping ............................................................................................................... 7 3. Strategic Assessment of Flood Risk ................................................................ 8 3.1 Overview ............................................................................................................................................ 8 3.2 Flooding from Rivers ......................................................................................................................... 10 3.3 Flooding from Surface Water ............................................................................................................. 18 3.4 Flooding from Groundwater ............................................................................................................... 19 3.5 Flooding from sewers ........................................................................................................................ 20 3.6 Flooding from artificial sources .......................................................................................................... 22 4. Avoiding Flood Risk – Applying the Sequential and Exception Tests ............. 24 4.1 Overview .......................................................................................................................................... 24 4.2 Applying the Sequential Test for the Local Plan .................................................................................. 24 4.3 Applying the Sequential Test for Planning Applications ....................................................................... 29 4.4 Exception Test................................................................................................................................... 30 5. Managing and Mitigating Flood Risk .............................................................. 32 5.1 Overview .......................................................................................................................................... 32 5.2 Site Layout........................................................................................................................................ 32 5.3 Development Design ......................................................................................................................... 32 5.4 Safe Access / Egress ........................................................................................................................ 34 5.5 Flood Warning and Evacuation .......................................................................................................... 35 5.6 Floodplain Compensation .................................................................................................................. 36 5.7 Flood Routing ................................................................................................................................... 38 5.8 Surface Water Management .............................................................................................................. 38 6. Preparing Site Specific FRAs ........................................................................ 43 6.1 What is a Flood Risk Assessment? .................................................................................................... 43 6.2 Level of Detail Required .................................................................................................................... 43 6.3 Detailed Flood Models ....................................................................................................................... 44 6.4 Flood Risk Assessment Checklist ...................................................................................................... 45 6.5 Pre-application Advice ....................................................................................................................... 47 7. Recommendations for Policy and Practice .................................................... 48 7.1 Using the SFRA ................................................................................................................................ 48 7.2 Emergency Planning ......................................................................................................................... 48 7.3 Strategic Planning ............................................................................................................................. 49 7.4 Level 2 SFRA .................................................................................................................................... 49 Appendix A Data Register ........................................................................................ 51 Appendix B Figures .................................................................................................. 52 Prepared for: Waverley Borough Council AECOM November 2018 Level 1 Strategic Flood Risk Assessment FINAL Project number: 60563228 Figures Figure 1-1 Taking flood risk into account in the preparation of a Local Plan (Planning Practice Guidance for Flood Risk and Coastal Change) ................................................................................................................................ 2 Figure 4-1 Application of Sequential Test for Local Plan preparation ................................................................. 25 Figure 5-1 Flood Resistant / Resilient Design Strategies, Improving Flood Performance, CLG 2007 .................. 33 Figure 5-2 Example of Floodplain Compensation Storage (Environment Agency 2009) ..................................... 37 Tables Table 1-1 Flood Risk Policy and Guidance Documents ....................................................................................... 3 Table 2-1 SFRA Stakeholder Organisations and Roles ....................................................................................... 6 Table 3-1 Fluvial Flood Zones (extracted from the PPG, 2014) ......................................................................... 10 Table 3-2 Peak river flow allowances for Thames River Basin District (use 1961 to 1990 baseline) .................... 12 Table 3-3 Mapped climate change scenarios.................................................................................................... 13 Table 3-4 Historical flooding summary ............................................................................................................. 13 Table 3-5 Environment Agency Flood