Stroud District Council Strategic Flood Risk Assessment for Local Development Framework Level 2 Final Report March 2012 Halcrow Group Limited Level 2 Strategic Flood Risk Assessment Stroud District Council Stroud District Council Strategic Flood Risk Assessment for Local Development Framework Level 2 – Final Report Volume 1 Contents Amendment Record This report has been issued and amended as follows: Issue Revision Description Date Signed 1 0 Draft Report 21/07/11 2 1 Revised Draft Report 30/11/11 3 2 Final Report 30/01/12 4 3 Final Report 21/03/12 (Includes EA Letter of Support) Prepared by: Caroline Mills, Rebecca Bailey and John Parkin Checked by: John Parkin, Caroline Mills and Beccy Dunn Approved by: John Parkin Level 2 Strategic Flood Risk Assessment Stroud District Council This page is left intentionally blank Level 2 Strategic Flood Risk Assessment Stroud District Council Contents List of Tables & Figures ....................................................................................................................... v Executive Summary ...............................................................................................................................i 1 Introduction...................................................................................................................................1 1.1 Project Overview ........................................................................................................................1 1.2 Background to Strategic Flood Risk Assessment......................................................................1 1.3 Aims & Objectives ......................................................................................................................4 1.4 Background to the Study Area ...................................................................................................5 2 Planning Context..........................................................................................................................7 2.1 Local Planning Context ..............................................................................................................7 2.2 Relevant External Policy: Catchment Flood Management Plans & Shoreline Management Plans 7 3 Level 2 SFRA Method.................................................................................................................11 3.1 Introduction ..............................................................................................................................11 3.2 Level 2 SFRA Site Assessment Assessment Method .............................................................12 4 Hydraulic & Hydrological Modelling Approach.......................................................................15 4.2 Hydrological Approach.............................................................................................................15 4.3 Hydraulic Approach..................................................................................................................15 4.4 UK Flood Hazard......................................................................................................................15 4.5 Breach and Overtopping Scenarios .........................................................................................17 4.6 Model QA .................................................................................................................................18 5 Quedgeley Results .....................................................................................................................19 5.1 Overview ..................................................................................................................................19 5.2 Aim of Level 2 SFRA at Quedgeley .........................................................................................20 5.3 Historic Flooding ......................................................................................................................20 5.4 Assessment of Flood Risk........................................................................................................21 5.5 Residual Risk ...........................................................................................................................25 5.6 Summary..................................................................................................................................26 6 Dursley and Cam Results ..........................................................................................................27 6.1 Overview ..................................................................................................................................27 6.2 Aim of Level 2 SFRA at Dursley and Cam...............................................................................27 6.3 Historic Flooding ......................................................................................................................28 6.4 Assessment of Flood Risk........................................................................................................28 6.5 Residual Risk ...........................................................................................................................30 6.6 Summary..................................................................................................................................31 Level 2 Strategic Flood Risk Assessment Stroud District Council 7 Stroud Area Results...................................................................................................................33 7.1 Overview ..................................................................................................................................33 7.2 Aim of Level 2 SFRA at Stroud ................................................................................................33 7.3 Historic Flooding ......................................................................................................................37 7.4 Assessment of Flood Risk........................................................................................................37 7.5 Residual Risk ...........................................................................................................................45 7.6 Summary..................................................................................................................................47 8 Sharpness Area Results ............................................................................................................49 8.2 Aim of Level 2 SFRA at Sharpness .........................................................................................50 8.3 Historic Flooding ......................................................................................................................51 8.4 Assessment of Flood Risk........................................................................................................52 8.5 Residual Risk ...........................................................................................................................53 8.6 Summary..................................................................................................................................56 9 Recommendations .....................................................................................................................59 9.1 Overview ..................................................................................................................................59 9.2 Strategic Policy Recommendations for All Sites......................................................................59 Site Selection Process Recommendations .......................................................................................59 Surface Water and Historical Flooding Sequential Testing Recommendations................................61 SUDS Recommendations..................................................................................................................61 Sites located adjacent to Canals .......................................................................................................62 Sites located behind defences ..........................................................................................................62 9.3 Site Specific Policy Recommendations....................................................................................63 Quedgeley near Gloucester...............................................................................................................63 Dursley Area......................................................................................................................................65 Stroud Area .......................................................................................................................................66 Sharpness Area.................................................................................................................................68 9.4 Development Control Policies..................................................................................................69 9.5 Requirements for Flood Risk Assessments & Guidance for Dealing with Windfall Sites ........71 9.6 Guidance on the use of Level 2 SFRA Flood Zone Data.........................................................75 APPENDIX A ........................................................................................................................................77 Site Assessment Tables & Site Plans ...............................................................................................77