Strategy Approval Report Authority Strategy IMSW000584 Reference Defra / WAG LDW WXS003E/001A/001A Number FSOD F/1011/0135 Promoting Authority Environment Agency – South West Region Strategy Name Parrett Estuary Flood Risk Management Strategy View of Parrett Estuary during 1981 flood from Stockland Bristol north west to Highbridge Date June 2010 Version 7 PAGE LEFT BLANK FOR DOUBLE SIDED PRINTING StAR for Parrett Estuary Flood Risk Management Strategy * * Version 7 – Changes only to Executive Summary Left blank for double sided printing Environment Agency – SW Region PEFRMS June 2010 CONTENTS 1 Executive Summary .....................................................................................................1 1.1 Introduction and Background ...................................................................................1 1.2 Problem ...................................................................................................................2 1.3 Options ....................................................................................................................2 1.4 Recommended Strategy ..........................................................................................2 1.5 Economic case and outcome measures ..................................................................3 1.6 Environmental and social considerations .................................................................3 1.7 Risks........................................................................................................................4 1.8 Implementation ........................................................................................................4 1.9 Contributions and funding ........................................................................................5 1.10 Status ......................................................................................................................5 1.11 Recommendations...................................................................................................5 2 Business case..............................................................................................................2 2.1 Introduction and Background ...................................................................................2 2.2 Problem ...................................................................................................................5 2.3 Options Considered ...............................................................................................10 2.4 Economics.............................................................................................................13 2.5 Environmental and Social Issues ...........................................................................18 2.6 Choice of Preferred Option ....................................................................................22 2.7 Other Considerations.............................................................................................27 3 Strategy Plan..............................................................................................................30 TABLES Table 1.1 Economic case and outcome measures on FMU basis Table 1.2 Strategy main risks Table 1.3 Cost of Strategy 2011 / 2014 / 2017 Table 2.1 Flood Management Units Table 2.2 Designations Table 2.3 Strategy Objectives Parrett Estuary Flood Risk Management Strategy Table 2.4 Significant Flood Events Table 2.5 Properties at risk Table 2.6 Summary of flood risk management options Table 2.7 Short listed options - Cannington / Huntspill and Pawlett FMUs Table 2.8 Summary of Potential Options – Bridgwater West and East FMUs Table 2.9 Summary of whole life cost and PV cost Table 2.10 Cost of Strategy 2011 / 2014 / 2017 Table 2.11 Preferred strategic options for each FMU – damages (£k) Table 2.12 Not Used Table 2.13 Environmental and social impacts affecting option selection Table 2.14 Summary of Option Assessment Table 2.15 Recommended overall preferred option and outcome measures Table 2.16 Environmental impacts and opportunities Table 2.17 Outcome Measure 1 Economic Benefits to 2017 CSR i Environment Agency – SW Region PEFRMS June 2010 Table 2.18 Outcome Measure 2 Number of households moved out of any flood probability category to a lower one to 2017 CSR Table 2.19 Outcome Measure 2b Number of households moved from the very significant or significant flood probability (high risk) category to the moderate or low category (low risk) to 2017 CSR Table 2.20 Final Outcome Measures to 2017 CSR Table 2.21 Strategy main risks Table 3.1 Comparison against strategy objectives Table 3.2 Cannington outfalls programme of work Table 3.3 Cannington embankments programme of work Table 3.4 Bridgwater programme of work Table 3.5 Spend profile FIGURES Figure 2.1 Parrett fluvial catchment Figure 2.2 Restriction of floodplain by M5 Figure 2.3 Important points of environmental interest Figure 2.4 Outline plan of 1981 flood extent (affecting PEFRMS area) Figure 2.5a Cannington and Bridgwater West- Current standards of defence and standards of protection Figure 2.5b Bridgwater East - Current standards of defence and standards of protection Figure 2.5c Huntspill and Pawlett FMU - Current standards of defence and standards of protection Figure 2.6a Standards of defence through time accounting for sea level rise, current condition and deterioration if no action taken – Cannington / Bridgwater West FMUs. Figure 2.6b Standards of defence through time accounting for sea level rise, current condition and deterioration if no action taken – Bridgwater East FMU Figure 2.6c Standards of defence through time accounting for sea level rise, current condition and deterioration if no action taken – Pawlett & Huntspill FMU Figure 2.7 Potential managed realignment options Figure 3.1 Summary of Our Plan Figure 3.2 Preferred strategic option Figure 3.3 Vulnerability plans (sequence of requirement for improvement work, if defences maintained as today) APPENDICES Appendix A Figures Appendix B Option development Appendix C Economics Appendix D Sedgemoor District Council commitment Appendix E Flood risk analysis Appendix F Rate of deterioration Appendix G Geomorphology Appendix H Strategic Environmental Assessment H1 SEA – Non Technical Summary H2 SEA H3 SEA – Appendices H4 Responses H5 Statement of Case H6 Consultation Brochure Appendix J Carbon footprinting Appendix K NRG approval history ii Environment Agency – SW Region PEFRMS June 2010 iii Environment Agency – SW Region PEFRMS June 2010 PAGE LEFT BLANK FOR DOUBLE SIDED PRINTING iv Environment Agency – SW Region PEFRMS June 2010 v Environment Agency – SW Region PEFRMS June 2010 PAGE LEFT BLANK FOR DOUBLE SIDED PRINTING vi Environment Agency – SW Region PEFRMS June 2010 1 Executive Summary SUBMISSION TO OBTAIN STRATEGY APPROVAL South West Region: Parrett Estuary Flood Risk Management Strategy (PEFRMS) Approval Value: £ 200M Sponsoring Director: Director of Operations APPROVAL ROUTE Section A9 of the Financial Scheme of Delegation states that, for whole life costs in a Flood Risk Management Strategy Agency Board approval is required in excess of £50,000,000. Route: National Capital Programme Manager Miles Jordan National Review Group Ken Allison Regional Director Richard Cresswell Director of Operations David Jordan Director of Finance Mark McLaughlin Chief Executive Paul Leinster Board Defra /WAG required (Natura 2000) 1.1 Introduction and Background 1.1.1 This report presents a 100 year flood risk management strategy for the Parrett Estuary through and downstream of Bridgwater, Somerset. It covers the flood cells that are only within the Parrett. Those flood cells at the estuary mouth will be considered within the Severn Estuary Flood Risk Management Strategy (SEFRMS) to be submitted for approval in 2010. Refer to key plan. 1.1.2 We instigated this strategy as many properties alongside the estuary currently receive a low standard of protection. It is timed to ensure that it is reflected in Sedgemoor District Council’s (SDC) Local Development Framework. As a consequence the Council has set a tariff for developer contributions within its supplementary planning guidance. 1.1.3 The Parrett Estuary is part of the Severn Estuary/Bristol Channel system with one of the highest tidal ranges in the world of up to 14m and is navigable to Bridgwater. More than 11,000 properties and 3,000 hectares of agricultural land are located within the River Parrett tidal floodplain, which makes up our strategy area. Most of the properties at risk lie within Bridgwater, including local emergency facilities. 1.1.4 The defences are located immediately adjacent to the estuary throughout the area and comprise earth embankments and walls. The land behind is generally level at approximately 6m AOD and defence levels range typically between 7.5m and 8.5m AOD. Flood warning and flood awareness systems are in place, but do not cover all those at risk if the defences breach. 1.1.5 We divided the strategy area into four hydraulically independent flood management units (FMUs), divided by topographic watersheds. The key plan shows the boundaries. 1.1.6 We considered National and European policy including the Water Framework and Habitats Directives. We drew on the following previous studies, strategies and projects: Shoreline Management Plan (Bridgwater Bay to Bideford Bay) (1998)(recommended Observe and Monitor in conjunction with possibly retreating the defence line); Coastal Habitat Management Plan (CHaMP) (2006), The Parrett Tidal Sluice Appraisal