Water Cheshire West and Chester Council October 2012 Winsford Area Flood Risk Assessment Prepared by: ............................................................. Checked by: ........................................................................ Glynne J Pritchard Jenny Belcher Principal Engineer Flood Risk Consultant Approved by: ............................................................. Checked by: Graham Knott Roy Lobley Regional Director Associate director Winsford Area Flood Risk Assessment Rev No Comments Checked by Approved by Date 0 Final Issued to Client JB/RL GK March 2013 5th Floor, 2 City Walk, Leeds, LS11 9AR Telephone: 0113 391 6800 Website: http://www.aecom.com Job No 60038336 Reference 59928/GJP/9881 Date Created April 2008 This document has been prepared by AECOM Limited for the sole use of our client (the “Client”) and in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM Limited and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM Limited. Table of Contents 1 Introduction ....................................................................................................................................................................... 1 1.1 Reason for the Report ........................................................................................................................................... 1 1.2 Requirements for PPS25 ....................................................................................................................................... 1 1.3 Scope of Services .................................................................................................................................................. 3 1.4 Sources of Information........................................................................................................................................... 4 2 Background Information ................................................................................................................................................... 6 2.1 Catchment Description .......................................................................................................................................... 6 2.2 Potential Development Areas ................................................................................................................................ 6 2.3 Sources and Causes of Flooding ........................................................................................................................... 8 2.4 Flood History ......................................................................................................................................................... 8 2.5 Existing Flood Risk Management .......................................................................................................................... 9 2.6 Flood Risk Assessment ......................................................................................................................................... 9 2.7 West Cheshire Strategic Flood Risk Assessment ................................................................................................. 9 3 Assessment of Flood Risk ............................................................................................................................................. 10 3.1 Site Visit ............................................................................................................................................................... 10 3.2 Fluvial Flooding .................................................................................................................................................... 10 3.3 Probability ............................................................................................................................................................ 12 3.4 Additional Flood Zone Analysis............................................................................................................................ 13 3.5 Climate Change ................................................................................................................................................... 17 3.6 Finished Floor Levels ........................................................................................................................................... 18 3.7 Flood Risk to People ............................................................................................................................................ 18 3.8 Displacement of Floodwater ................................................................................................................................ 19 3.9 Run-off................................................................................................................................................................. 20 4 Sequential Testing .......................................................................................................................................................... 21 4.1 Introduction .......................................................................................................................................................... 21 4.2 Sequential Test .................................................................................................................................................... 21 4.3 Exception Test ..................................................................................................................................................... 21 5 Flood Mitigation Measures ............................................................................................................................................. 22 5.1 Fluvial Measures .................................................................................................................................................. 22 5.2 Land Raising ........................................................................................................................................................ 22 5.3 Foul and Surface Water Arrangements ............................................................................................................... 22 5.4 Sustainable Drainage Systems ............................................................................................................................ 22 5.5 Flood Proofing ..................................................................................................................................................... 23 5.6 Access and Egress .............................................................................................................................................. 26 5.7 Residual Risks ..................................................................................................................................................... 26 5.8 Emergency Access .............................................................................................................................................. 27 6 Summary.......................................................................................................................................................................... 28 6.1 Overview of Flood Risk ........................................................................................................................................ 28 6.2 Overview of Development Proposals ................................................................................................................... 28 References .................................................................................................................................................................................... 29 Appendix A: Figures and Plans ................................................................................................................................................... 31 Appendix B: Site Matrix ............................................................................................................................................................... 32 Glossary ........................................................................................................................................................................................ 33 List of Tables Table 1: PPS25 Flood Zones ...........................................................................................................................................................2 Table 2: Flood Risk Vulnerability Classification from PPS25 ...........................................................................................................3 Table 3: Data received .....................................................................................................................................................................4 Table 4: Winsford Potential Development Areas at Risk of Fluvial Flood ........................................................................................ 7 Table 5: Sources of Flooding ...........................................................................................................................................................8 Table 6: Peak 1 in 200 year Water