Shropshire Council Strategic Flood Risk Assessment for Local Development Framework Level 1 - Update Volume 1 June 2012 Halcrow Group Limited Strategic Flood Risk Assessment Shropshire Council This page has been left intentionally blank Strategic Flood Risk Assessment Shropshire Council Shropshire Council Strategic Flood Risk Assessment for Local Development Framework Level 1 - Update Volume 1 Contents Amendment Record This report has been issued and amended as follows: Issue Revision Description Date Signed 1 - Draft Final Report January 2012 2 1 Revised Draft Final May Report 2012 3 2 Final Issued Report June 2012 Strategic Flood Risk Assessment Shropshire Council This page has been left intentionally blank Strategic Flood Risk Assessment Shropshire Council Contents Contents.................................................................................................................................................1 Executive Summary ..............................................................................................................................3 1 Introduction...................................................................................................................................5 1.1 Terms of Reference ...................................................................................................................5 1.2 Project Objectives ......................................................................................................................5 1.3 Methodology...............................................................................................................................6 1.4 Project Deliverables ...................................................................................................................6 1.5 SFRA Context ............................................................................................................................7 1.6 Shropshire Council.....................................................................................................................8 2 Planning Context ........................................................................................................................11 2.1 Introduction ..............................................................................................................................11 2.2 National Planning Policy ..........................................................................................................11 2.3 Regional Planning Policy .........................................................................................................11 2.4 Local Planning Policy...............................................................................................................12 3 Flood Zone Maps........................................................................................................................14 3.1 Introduction ..............................................................................................................................14 3.2 NPPF Flood Zones...................................................................................................................14 3.3 Environment Agency Flood Zones...........................................................................................15 3.4 SFRA Flood Maps....................................................................................................................15 3.5 SFRA Climate Change Maps...................................................................................................15 4 Overview of the NPPF Technical Guidance on Flood Risk....................................................17 4.1 Key Aims ..................................................................................................................................17 4.2 Outcomes of the SFRA Process ..............................................................................................18 4.3 The Sequential Test.................................................................................................................18 4.4 The Exception Test ..................................................................................................................18 5 Study Methodology ....................................................................................................................20 5.1 The Practice Guide Companion to PPS 25..............................................................................20 5.2 Level 1 SFRA ...........................................................................................................................21 5.3 Approach to Data Gathering ....................................................................................................22 5.4 Production of Flood Maps ........................................................................................................23 5.5 Forms of Flooding and Data Limitations ..................................................................................27 5.6 Wider Published Studies and New Legislation ........................................................................30 1 Strategic Flood Risk Assessment Shropshire Council 6 Flood Risk in the Study Area ....................................................................................................32 6.1 Hydrology .................................................................................................................................32 6.2 Geology....................................................................................................................................34 6.3 Historical Flooding....................................................................................................................35 7 Flood Warning Systems and Flood Management Measures .................................................50 8 Flood Risk Management Policies .............................................................................................56 8.1 Catchment Flood Management Plans......................................................................................56 8.2 Policy Considerations...............................................................................................................61 9 Guidance on the Application of the Sequential Test..............................................................63 9.1 Step One: Strategic Overview of flood risk across all potential development areas ...............63 9.2 Step Two: Flood Risk Issues in Zone 1 ...................................................................................63 9.3 Step Three: Sequential Test in Zones 2 and 3 ........................................................................64 10 Guidance for the Preparation of Flood Risk Assessments....................................................65 10.1 Proposed Developments Within Flood Zone 3a ..................................................................69 10.2 Proposed Developments Within Medium Probability Flood Zone 2 ....................................70 10.3 Proposed Developments Within Flood Zones 1 and 2 ........................................................70 10.4 Raised Floor Levels and Basements (Freeboard)...............................................................70 11 Guidance for the Application of Sustainable Drainage Systems (SuDS) .............................71 11.1 Introduction ..........................................................................................................................71 11.2 Types of SuDS Systems......................................................................................................71 11.3 Application of SuDS for Shropshire .....................................................................................72 12 Gap Analysis...............................................................................................................................78 12.1 Introduction ..........................................................................................................................78 12.2 Missing or Incomplete Data .................................................................................................78 12.3 Level 2 SFRAs.....................................................................................................................78 13 References/Glossary..................................................................................................................81 APPENDIX A ........................................................................................................................................85 APPENDIX B ........................................................................................................................................87 APPENDIX C ........................................................................................................................................89 2 Strategic Flood Risk Assessment Shropshire Council Executive Summary The Districts and Boroughs of Shropshire as well as Shropshire County Council and the Unitary Authority Telford and Wrekin Council, commissioned Halcrow in 2007 to produce a Level 1 Strategic Flood Risk Assessment (SFRA) in accordance with Planning Policy Statement 25 (PPS 25). The project was delivered in September 2007, which comprised a series of reports (one for each District and Borough, plus the Unitary Authority of Telford and Wrekin. On the 1st April 2009 Shropshire County Council and its Districts and Boroughs were