Derbyshire Dales District Council Strategic Flood Risk Assessment for Local Development Framework Level 1 Volume 2 - FINAL September 2008 Halcrow Group Limited Strategic Flood Risk Assessment Derbyshire Dales District Council Strategic Flood Risk Assessment Derbyshire Dales District Council Derbyshire Dales District Council Strategic Flood Risk Assessment for Local Development Framework Level 1 - FINAL Volume 1 Contents Amendment Record This report has been issued and amended as follows: Issue Revision Description Date Signed 1 Draft Report 23/03/08 RD 2 Final Report 21/07/08 RD 2 1 Final Report 11/09/08 RD Prepared by: Beccy Dunn/Caroline Mills Checked by: John Parkin Approved by: Shirel Saranga Strategic Flood Risk Assessment Derbyshire Dales District Council This page is left intentionally blank 1 Strategic Flood Risk Assessment Derbyshire Dales District Council Contents Contents.................................................................................................................................................2 List of Tables & Figures .......................................................................................................................5 Executive Summary ..............................................................................................................................8 1 Introduction.................................................................................................................................10 1.1 Terms of Reference .................................................................................................................10 1.2 Project Aims .............................................................................................................................10 1.3 Project Objectives ....................................................................................................................10 1.4 Project Deliverables .................................................................................................................11 1.5 Outcomes of the SFRA Process ..............................................................................................11 1.6 SFRA Context ..........................................................................................................................14 1.7 The Study Area ........................................................................................................................15 2 Study Methodology ....................................................................................................................20 2.1 Level 1 SFRA Methodology .....................................................................................................20 2.2 Need for a Level 2 SFRA .........................................................................................................21 2.3 Technical Background..............................................................................................................21 2.4 Environment Agency Flood Zone Maps...................................................................................22 3 Planning Context........................................................................................................................23 3.1 Introduction ..............................................................................................................................24 3.2 Planning Policy Framework .....................................................................................................24 3.3 National Planning Policy ..........................................................................................................24 3.4 Regional Planning Policy .........................................................................................................26 3.5 Local Planning Policy...............................................................................................................29 4 Data Collection and Review ......................................................................................................31 4.1 Overview of Flooding Sources .................................................................................................32 4.2 Approach to Data Gathering ....................................................................................................32 4.3 Findings of the Regional Flood Risk Appraisal ........................................................................32 4.4 Historical Flooding....................................................................................................................34 4.5 Fluvial Flood Risk in Derbyshire Dales ....................................................................................35 4.6 Fluvial Flood Risk in the Plan Area ..........................................................................................37 4.7 Issues With Existing Flood Zone Maps....................................................................................39 4.8 Flooding from Other Sources Introduction...............................................................................40 4.9 Flooding from Artificial Drainage Systems and Surface Water Runoff ....................................40 4.10 Flooding from Impounded Water Bodies .............................................................................45 2 Strategic Flood Risk Assessment Derbyshire Dales District Council 4.11 Flooding from Groundwater.................................................................................................47 5 Strategic Flood Risk Mapping...................................................................................................48 5.1 Strategic Flood Risk Maps .......................................................................................................48 5.2 Climate Change .......................................................................................................................52 6 Flood Warning Systems and Flood Risk Management Measures.........................................58 6.1 Flood Risk Management Introduction ......................................................................................58 6.2 Catchment Flood Management Plans......................................................................................58 6.3 Flood Risk Management Strategies.........................................................................................60 6.4 Flood Defences........................................................................................................................61 6.5 Culverts ....................................................................................................................................67 6.6 Storage Areas ..........................................................................................................................68 6.7 Residual Risk ...........................................................................................................................69 6.8 Existing Flood Warning System ...............................................................................................70 6.9 Flood Response Plan...............................................................................................................72 7 Flood Risk Management Policy Considerations .....................................................................74 7.1 Overview ..................................................................................................................................74 7.2 Policy Considerations...............................................................................................................74 7.3 Council-Specific Policy Considerations (Plan Area) ................................................................76 7.4 Development Control Policies..................................................................................................77 7.5 Sensitive Development Locations............................................................................................80 8 Guidance on the Application of the Sequential Test..............................................................82 8.1 Step One: Strategic Overview of flood risk across all potential development areas ...............82 8.2 Step Two: Flood Risk Issues in Zone 1 ...................................................................................82 8.3 Step Three: Sequential Test in Zones 2 and 3 ........................................................................83 9 Guidance for Developers...........................................................................................................84 9.2 Raised Floor Levels and Basements (Freeboard) ...................................................................87 9.3 Developer Contributions...........................................................................................................88 10 Guidance for the Application of Sustainable Drainage Systems ..........................................90 10.1 Introduction ..........................................................................................................................90 10.2 Types of SUDS Systems .....................................................................................................90 10.3 Application of SUDS for Derbyshire Dales Plan Area .........................................................92 10.4 Adoption and Maintenance of SUDS...................................................................................94 11 Recommendations