Strategic Flood Risk Assessment
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West Lindsey District Council STRATEGIC FLOOD RISK ASSESSMENT SFRA Final Report – July 2009 EVIDENCE BASE Prepared by: ................................................ Checked by: ................................................. Clare Marsh Philip McLoughlin Graduate Engineer Regional Director Approved by: ................................................ Roy Lobley Associate Director Rev Comments Checked Approved Date No by by 01G Final version issued to client PML RL 3/7/09 1 The Forum, Minerva Business Park, Lynch Wood, Peterborough, PE2 6FT Telephone: 01733 391456 Fax: 01733 391139 Website: http://www.aecom.com Job No 60035618 Reference 01G Date Created July 2009 This document has been prepared by AECOM Limited (“AECOM”) 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 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. f:\projects\52179i west lindsey dc sfra\reports\final report\final 001g.doc As of 4th May 2009, Faber Maunsell Limited has changed its name to AECOM Limited and has rebranded as AECOM, as part of our parent company’s strategy to integrate across business lines and regions globally. AECOM is a global provider of professional technical and management support services with over 43,000 people in more than 100 countries and is a leader in the delivery of Building Engineering, Transportation, Water, Environment, Programme Management, Energy and Planning & Design services. As a result of this global integration process, we can provide a broad array of solutions, through numerous geographic locations, with highly capable staff and cutting-edge technologies to address your needs and the challenges you face. Though our name is changing, our commitment to our clients and their projects remains the same. Our people working with you will continue to work with you. Our goal remains to continue providing clients with high-quality, responsive service and to make this organisational change transparent to you as we move forward. Some material contained within this document may refer to our previous name Faber Maunsell, but is also applicable to AECOM. www.aecom.com Table of Contents Contents…………………………………………………………………………………………………..i List of Tables and Figures ........................................................................................................ vii Executive Summary .................................................................................................................... v 1 Introduction ..................................................................................................................... 1 2 Level 1 SFRA ................................................................................................................... 5 Planning Policy Statement 25 ........................................................................................... 5 Sequential Test ................................................................................................................. 5 Flood Risk ......................................................................................................................... 5 Flood Zones ...................................................................................................................... 5 Indicative Floodplain Maps ................................................................................................ 6 Flood Zone Maps .............................................................................................................. 7 Flood Maps ........................................................................................................................ 7 3 Causes of Flooding ....................................................................................................... 11 Overflowing of Watercourses .......................................................................................... 11 Breaching of Embankments ............................................................................................ 12 Mechanical, Structural or Operational Failure ................................................................. 13 Localised Flooding .......................................................................................................... 14 Tidal Flooding .................................................................................................................. 15 Functional Floodplains and Washlands .......................................................................... 15 Other Sources of Flooding .............................................................................................. 15 4 Flooding in West Lindsey ............................................................................................. 19 Classes of Flooding ......................................................................................................... 19 Records of Flooding ........................................................................................................ 20 Flood Alleviation Measures ............................................................................................. 27 Operational and Emergency Planning ............................................................................ 29 5 Climate Change ............................................................................................................. 33 6 Sequential Test .............................................................................................................. 37 Gainsborough .................................................................................................................. 37 Market Rasen .................................................................................................................. 37 Saxilby 37 Bardney ........................................................................................................................... 37 7 Exception Test ............................................................................................................... 41 Settlements Requiring Level 2 SFRA ............................................................................. 41 Gainsborough .................................................................................................................. 41 Bardney ........................................................................................................................... 41 Saxilby 41 Market Rasen .................................................................................................................. 41 8 Level 2 SFRA ................................................................................................................. 45 Planning Policy Statement 25 ......................................................................................... 45 9 Actual Flood Risk .......................................................................................................... 49 Definition of Actual Flood risk .......................................................................................... 49 General Methodology ...................................................................................................... 49 Topographic Divisions ..................................................................................................... 52 Anthropogenic Influences ................................................................................................ 53 Hydraulic Models ............................................................................................................. 54 Actual Flood Risk Mapping ............................................................................................. 56 Flood Risk Mapping – Climate Change Scenario ........................................................... 57 Flood Hazard Mapping .................................................................................................... 57 Impact of Climate Change ............................................................................................... 58 10 Assessment of Flood Risk in the Study Areas .......................................................... 63 11 Study Areas in West Lindsey ....................................................................................... 67 GAINSBOROUGH .......................................................................................................... 68 MARKET RASEN ............................................................................................................ 70 SAXILBY ......................................................................................................................... 72 BARDNEY ....................................................................................................................... 74 12 Surface Water Drainage in Gainsborough .................................................................. 79 13 Sequential Approach .................................................................................................... 83 Gainsborough .................................................................................................................. 83 Bardney ..........................................................................................................................