Taunton-Deane-Strategic-Flood-Risk-Assessment-Jba-Consulting-2011.Pdf
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Taunton Deane Borough Council Strategic Flood Risk Assessment FINAL May 2011 Taunton Deane Borough Council The Deane House Belvedere Rd Taunton Somerset TA1 1HE JBA Office Aberdeen House South Road HAYWARDS HEATH West Sussex RH19 1NG JBA Project Manager Alastair Dale Revision History Revision Ref / Date Issued Amendments Issued to Ralph Willoughby-Foster TDBC Planning First Draft 22/11/2010 N/A Nigel Smith Environment Agency Significant changes to Ralph Willoughby-Foster all sections in light of TDBC Planning Second Draft 08/02/2011 Environment Agency Nigel Smith Comments Environment Agency Consideration of Norton Fitzwarren Ralph Willoughby-Foster Dam, inclusion of TDBC Planning Final Report 31/05/2011 Flood Map for Surface Nigel Smith Water and minor Environment Agency corrections to text Contract This is a study commissioned by Taunton Deane Borough Council relating to prepare a Strategic Flood Risk Assessment. This document has been prepared in response to a commission awarded by Taunton Deane borough Council in August 2010. Prepared by .................................................. Oliver Francis MEng MSc Reviewed by ................................................. Alastair Dale BSc PGDip MIAHR Purpose This document has been prepared as a report for Taunton Deane Borough Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by Taunton Deane Borough Council for the purposes for which it was originally commissioned and prepared. Copyright © Jeremy Benn Associates Limited 2011 Carbon Footprint 577g A printed copy of the main text in this document will result in a carbon footprint of 454g if 100% post-consumer recycled paper is used and 577g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex. JBA is a carbon neutral company and the carbon emissions from our activities are offset. Contents 1. Introduction .......................................................................................................... 2 1.1 About this report .................................................................................................... 2 1.2 SFRA objectives .................................................................................................... 3 1.3 How to find what you need in the SFRA ................................................................ 3 1.4 Scope of assessment ............................................................................................ 4 1.5 Approach ............................................................................................................... 7 1.6 Consultation ........................................................................................................... 9 1.7 Legislation and Regulation .................................................................................... 9 2. Understanding flood risk in the Borough ......................................................... 10 2.1 Why flood risk is an issue ...................................................................................... 10 2.2 How flood risk is assessed .................................................................................... 19 2.3 Understanding flooding in the Borough ................................................................. 23 2.4 Possible responses to flooding .............................................................................. 29 2.5 Policy considerations ............................................................................................. 30 3. Mapping and risk based approach .................................................................... 33 3.1 Summary of mapping for all sources of flood risk ................................................. 33 3.2 Other relevant flood risk information ...................................................................... 34 3.3 Sequential approach .............................................................................................. 35 3.4 Sequential test ....................................................................................................... 35 3.5 Exception test ........................................................................................................ 38 4. Overview of future development ........................................................................ 39 4.1 Overview and vision for new development ............................................................ 39 4.2 Extent and type of development ............................................................................ 39 4.3 Timing of development .......................................................................................... 41 5. Strategic assessment of future development ................................................... 42 5.1 Summary of flood risk issues ................................................................................. 42 5.2 Development over next 5 years ............................................................................. 42 5.3 Longer term development up to 2028 .................................................................... 42 6. Strategic responses ............................................................................................ 44 6.1 Introduction ............................................................................................................ 44 6.2 Review and assessment of options ....................................................................... 44 6.3 Description of strategic options considered ........................................................... 48 6.4 Requirements for Development ............................................................................. 51 6.5 Generic guidance on applicable SUDs techniques ............................................... 53 7. Summary assessment of development sites .................................................... 56 7.1 Introduction ............................................................................................................ 56 7.2 Summary tables and FRA requirements ............................................................... 56 8. Strategic management plan ................................................................................ 57 8.1 Reasons why a plan is needed .............................................................................. 57 8.2 Key issues ............................................................................................................. 57 8.3 The Plan ................................................................................................................ 58 Appendices........................................................................................................................ I A. Update of historical flood database ................................................................... II B. Assessment of Norton Fitzwarren Dam ............................................................ III C. Section 7 Maps ..................................................................................................... IV D. Summary of Modelling Work .............................................................................. XXXIX E. Flood Defences within the borough .................................................................. XLII F. Surface Runoff Calculations .............................................................................. XLIV G. Procedure for Flood Zone Challenges .............................................................. XLV H. Mapping ................................................................................................................ XLVII 1. Introduction 1.1 About this report This version of the Taunton Deane Borough Council SFRA replaces the previous document "Taunton Deane Strategic Flood Risk assessment Main Report - Final - September 2007". The primary objective for updating the previous version of the SFRA was to prepare a document that was compliant with the latest guidance described in the Planning Policy Statement 25 (PPS25) Practice Guide1. The key issues being: The information on sequential testing was out of date; The flood modelling needed to be updated to reflect recent changes; and The flood outlines needed to be updated to reflect the latest master planning proposals. The report contains information on flood zones and an assessment of risks from all sources of flooding and also provides more detailed information on the nature of flood hazards that exist in areas that do flood. In addition the strategic responses that should be considered to address the effect of proposed development allocations are described to address conditions as they are now and as they will be in the future. The study area is outlined in Figure 1-1. Figure 1-1: Assessment Area and extent of river hazard mapping 1 Planning Policy Statement 25: Development & Flood Risk Practice Guide (Communities and Local Government, December 2009) TDBC SFRA v3.2 (FINAL).docx 2 1.2 SFRA objectives SFRAs should be a key part of the evidence base to help inform the allocation of development in a local plan area through the preparation of Local Development Documents. The primary objective of the SFRA is that is should form part of the evidence base of the Local Development Framework to inform Core Strategy allocations and ensure that they are in accordance with PPS252. In order to achieve this, the Practice Guide1 states that SFRAs need to provide sufficient