Increased Scope SFRA and Sequential Testing of Sites A Technical Report Supporting the Royal Borough of Windsor & Maidenhead Borough Local Plan Published in January 2014 Royal Borough of Windsor and Maidenhead Planning & Property Services Town Hall St Ives Road Maidenhead SL6 1RF STRATEGIC FLOOD RISK ASSESSMENT (SFRA) Increased Scope SFRA and Sequential Testing of Sites Updated Flood Mapping and January 2014 Flood Event in the Royal Borough Subsequent to the production of this Increased Scope SFRA and Sequential Testing of Sites, it should be noted that in December 2013, the Environment Agency published updated Flood Maps. These and any subsequent revised Flood Maps will be taken into account in the next update of the SFRA which will also inform an update of this Increased Scope report. This report was also produced prior to the storm event of January 2014. As a result of heavy rainfall and existing ground conditions, a number of areas in the Royal Borough were affected by fluvial flooding from the River Thames and other watercourses, and other areas were affected by groundwater flooding or surface water flooding. The Council has sought to record information associated with this storm and any future update of this report, including any sequential testing of additional sites will take this into account. STRATEGIC FLOOD RISK ASSESSMENT (SFRA) Increased Scope SFRA and Sequential Testing of Sites (This page intentionally left blank) STRATEGIC FLOOD RISK ASSESSMENT (SFRA) Increased Scope SFRA and Sequential Testing of Sites Table of Contents 1 Introduction................................................................................................ 1 1.1 Context and Purpose .......................................................................... 1 1.2 The Study Area ................................................................................... 1 2 Background ............................................................................................... 3 2.1 Context ............................................................................................... 3 2.2 National Planning Policy Framework .................................................. 3 2.3 The Sequential Test ............................................................................ 3 2.4 The Exception Test ............................................................................. 3 2.5 Background to Site Selection .............................................................. 4 2.6 Scope of Report .................................................................................. 7 3 Information Sources and Methodology ...................................................... 8 3.1 General ............................................................................................... 8 3.2 Flood Map ........................................................................................... 8 3.3 Hydrodynamic Modelling ..................................................................... 9 3.4 Assessment of Risk to Life (Flood Hazard) ......................................... 9 3.4.1 General ........................................................................................ 9 3.4.2 Flood Hazard due to River Thames Flooding ............................. 10 3.4.3 Flood Hazard due to Flood Defence Failure ............................... 10 3.5 Historical Flooding ............................................................................ 11 3.6 Flood Map for Surface Water Flooding (FMfSWF) ............................ 12 3.7 Areas Susceptible to Groundwater Flooding (AStGWF) ................... 12 3.8 NPPF Vulnerability ............................................................................ 13 3.9 Site Specific Assessments ................................................................ 14 4 Individual Site Assessments – Maidenhead ............................................ 15 4.1 Order of Presentation ........................................................................ 15 5 Individual Site Assessments – Windsor & Eton ....................................... 74 5.1 Order of Presentation ........................................................................ 74 7 Individual Site Assessments – Parishes (Bisham) ................................. 119 7.1 Order of Presentation ...................................................................... 119 8 Individual Site Assessments – Parishes (Bray) ..................................... 122 8.1 Order of Presentation ...................................................................... 122 9 Individual Site Assessments – Parishes (Cookham) ............................. 129 9.1 Order of Presentation ...................................................................... 129 10 Individual Site Assessments – Parishes (Cox Green) ........................ 138 10.1 Order of Presentation .................................................................. 138 11 Individual Site Assessments – Parishes (Datchet) ............................. 141 11.1 Order of Presentation .................................................................. 141 12 Individual Site Assessments – Parishes (Hurley) ............................... 148 12.1 Order of Presentation .................................................................. 148 13 Individual Site Assessments – Parishes (Old Windsor)...................... 151 STRATEGIC FLOOD RISK ASSESSMENT (SFRA) Increased Scope SFRA and Sequential Testing of Sites 13.1 Order of Presentation .................................................................. 151 14 Individual Site Assessments – Parishes (Sunningdale) ..................... 156 14.1 Order of Presentation .................................................................. 156 15 Individual Site Assessments – Parishes (Sunninghill and Ascot) ....... 165 15.1 Order of Presentation .................................................................. 165 16 Individual Site Assessments – Parishes (White Waltham) ................. 194 16.1 Order of Presentation .................................................................. 194 17 Sequential Test Methodology ............................................................. 205 17.1 Overview...................................................................................... 205 17.2 Sequential Test Site Selection Assumptions ............................... 205 17.3 Sequential Test Site Selection ..................................................... 206 17.4 Employment Sequential Test ....................................................... 207 17.5 Conclusion ................................................................................... 213 17.6 Housing Sequential Test.............................................................. 207 17.7 Conclusion ................................................................................... 209 17.8 Housing Exception Test ............................................................... 213 Appendices Appendix A Table A1 – All sites ranked with reasons for discounting Table A2 – Housing Sites ranked with reasons for discounting Table A3 – Employment Sites ranked with reasons for discounting Appendix B Table B1 – Housing Sites – detailed information and ranking Table B2 – Employment Sites - detailed information and ranking Figures Figure A Overview of Potential Allocation Sites STRATEGIC FLOOD RISK ASSESSMENT (SFRA) Increased Scope SFRA and Sequential Testing of Sites 1 Introduction 1.1 Context and Purpose 1. This report should be read in conjunction with the Level 1 Strategic Flood Risk Assessment (SFRA) published in January 2014, the Strategic Housing Land Availability Assessment (SHLAA) and the Employment Land Review. 2. There are two parts to this report, the first part being an ‘Increased Scope’ SFRA. The purpose of the Increased Scope SFRA is to provide more detailed flood risk evidence on 89 sites identified by the Royal Borough of Windsor and Maidenhead as being potential allocation sites within its proposed Borough Local Plan (BLP). The BLP will provide a policy framework, strategy and development management policies to help guide proposals for development over the next 15 years. It will also include housing, employment and other site allocations. 3. The information provided on the sites is then used to undertake the second part of the report, the Sequential Test, which aims to meet the requirement of the National Planning Policy Framework (NPPF) to allocate development in areas of lowest flood risk (i.e. Flood Zone 1) where they are reasonable available. Where there are no available sites in Flood Zone 1, sites in Flood Zone 2 can be considered followed by Flood Zone 3 applying the Exception Test if required. This report highlights key elements that should be considered by developers undertaking Flood Risk Assessments to satisfy the second part of the Exception Test in terms of ensuring the safety of a site. 4. This report centres on potential residential and employment development in the Royal Borough and through the provision of detailed flood evidence on sites and the application of a sequential testing methodology, aims to steer development away from areas vulnerable to flooding. The list of sites that have been assessed in this report were those subject to consultation between November 2012 and January 2013. This included urban sites as well as the previously developed sites in the Green Belt that were all included in the consultation. They were tested against relevant site data sources including the Strategic