SURREY HEATH STRATEGIC FLOOD RISK ASSESSMENT For SURREY HEATH BOROUGH COUNCIL SUMMARY REPORT June 2008 Capita Symonds © Capita Symonds Ltd 24-30 Holborn London EC1N 2LX Tel: 02078709300 Fax: 02078709399 Email: [email protected] Surrey Heath SFRA Surrey Heath Strategic Flood Risk Assessment Summary Document Report REV 1.0 / June 2008 This document is the property of Surrey Heath Borough Council. If you have received it in error, please return it immediately to Surrey Heath Borough Council. Job Number: CS/026472 PD: AGJD PM: RG Report status: FINAL REV 1.0 Date of issue: 18/06/08 CSL Main author(s): SC/BS CSL Checked: RG Client Approval: - This report has been prepared by Capita Symonds Limited with all reasonable skill, care and diligence within the terms of the Contract with the Client, incorporating our General Terms and Conditions of Business and taking account of the resources devoted to it by agreement with the client. We disclaim any responsibility to the client and others in respect of any matters outside the scope of the above. This report is confidential to the client and we accept no responsibility of whatsoever nature to third parties to whom this report, or any part thereof, is made known. Any such party relies on the report at their own risk Surrey Heath Borough Council i June 2008 Surrey Heath SFRA DOCUMENT REGISTER It is accepted that the content of the Surrey Heath SFRA will need to be reviewed and amended as new information becomes available. This document provides a summary of the Woking and Surrey Heath SFRA and the Blackwater Valley SFRA. When either these documents are updated, this summary report will also need to be reviewed. It is the responsibility of the reader to be satisfied that they are using the most up to date information and that this has been included within the Surrey Heath SFRA. The Surrey Heath SFRA Summary Report (this document) is a live document requiring review in the event of an improvement or change in the fundamental principles or best available data underpinning the strategy. This is likely to include, but should not be limited to: • An improvement in the best available information or a reduction in uncertainty. • Revision to relevant policy, plans or guidance. • Outcomes of neighbouring strategies. Revisions to this document should be recorded below in Table 1.0 to maintain clarity for those making decisions involving flood risk issues. Table 1.0 Document Register Version Date Issued by Issued to Rev 1.0 18 th June CSL SHBC 2008 Surrey Heath Borough Council ii June 2008 Surrey Heath SFRA CONTENTS DOCUMENT REGISTER .............................................................................................................. II FOREWORD ................................................................................................................................IV 1. INTRODUCTION ................................................................................................... 1-1 Introduction .......................................................................................................... 1-1 Study Area ............................................................................................................ 1-1 SFRA Reports....................................................................................................... 1-1 2. HOW FLOOD RISK IS ASSESSED...................................................................... 2-1 Defining Flood Risk ............................................................................................. 2-1 Assessing Flood Risk.......................................................................................... 2-1 3. SUMMARY OF FLOOD RISK IN SURREY HEATH............................................. 3-1 Flooding from Rivers........................................................................................... 3-1 Flooding from Land ............................................................................................. 3-4 Flooding from Sewers ......................................................................................... 3-5 Flooding from Groundwater ............................................................................... 3-5 Flooding from Artificial Sources ........................................................................ 3-6 4. SFRA DECISION SUPPORT GUIDANCE............................................................ 4-1 5. SFRA MAINTENANCE AND MANAGEMENT ..................................................... 5-1 Data Collection..................................................................................................... 5-1 Data Ownership.................................................................................................... 5-1 Monitoring the SFRA ........................................................................................... 5-4 Incorporating new datasets ................................................................................ 5-4 Updating SFRA reports and figures................................................................... 5-5 6. CONCLUSIONS AND RECOMMENDATIONS..................................................... 6-1 7. GLOSSARY........................................................................................................... 7-1 LIST OF FIGURES Figure A – SFRAs covering Surrey Heath Borough Figure B - Historic Flooding (all sources) Figure C - SFRA Flood Zones (2, 3a, and 3b) Figure D - Climate Change Figure E - Artificial Sources of Flooding (Canal) Surrey Heath Borough Council Page iii June 2008 Surrey Heath SFRA FOREWORD Surrey Heath Borough Council is required to prepare a Strategic Flood Risk Assessment (SFRA) to support their Local Development Frameworks (LDF). The borough is within two river catchments, the River Blackwater catchment and the Hale and Addlestone Bourne catchment. To ensure the flooding mechanisms and therefore flood risks in the different catchments were appropriately assessed two SFRAs have been completed, one for each catchment. The Hale and Addlestone Bourne (Woking and Surrey Heath) SFRA has been prepared with Woking Borough Council. The Blackwater Valley SFRA has been prepared in conjunction with Hart Borough Council. The findings of these two SFRAs in relation to Surrey Heath are summarised in this report. The SFRAs create a strategic framework for the consideration of flood risk when making planning decisions. They have been developed with reference to Planning Policy Statement 25 (PPS25): development and flood risk and additional guidance provided by the Environment Agency. The fundamental concepts that underpin the SFRA are outlined in PPS25. The guidance provided in PPS25 requires local authorities and those responsible for development decisions to demonstrate that they have applied a risk based, sequential approach in preparing development plans and consideration of flooding through the application of a sequential test. Failure to demonstrate that such a test has been undertaken potentially leaves planning decisions and land allocations open to challenge during the planning process. The underlying objective of the risk based sequential allocation of land is to reduce the exposure of new development to flooding and reduce the reliance on long-term maintenance of built flood defences. Within areas at risk from flooding, it is expected that development proposals will contribute to a reduction of flood risk. SFRAs are essential to enable a strategic and proactive approach to be applied to flood risk management. The assessment allows us to understand current flood risk on a wide-spatial scale and how this is likely to change in the future. The main objective of the Surrey Heath SFRAs is to provide a summary of flood information: • so that an evidence based and risk based sequential approach can be adopted when making planning decisions, in line with PPS25; • that is strategic in that it covers a wide spatial area and looks at flood risk today and in the future; • that supports sustainability appraisals of the local development frameworks; and • that identifies what further investigations may be required in flood risk assessments for specific development proposals. The SFRA is a live document that is intended to be updated as new information and guidance become available. The outcomes and conclusions of the SFRA may not be valid in the event of future changes to the data or the baseline flooding situation. It is the responsibility of the user to ensure they are using the best available information. Surrey Heath Borough Council Page iv June 2008 Surrey Heath SFRA 1. INTRODUCTION Introduction This document provides a summary of the Flood Risk from various sources in the Borough of Surrey Heath compiled from two Strategic Flood Risk Assessments (SFRAs) carried out in the Woking and Surrey Heath, and the Blackwater Valley area. Flood Risk in Surrey Heath has been assessed through two SFRAs due to its administrative boundaries encompassing sections of two river catchments: • the River Blackwater catchment; and • the Addlestone and Hale Bourne catchments The two SFRAs are summarised here and with this document form the Surrey Heath SFRA. The Woking and Surrey Heath SFRA concentrates mainly on the Addlestone Bourne and Hale Bourne catchment, whereas the Blackwater Valley SFRA concentrates on the River Blackwater. The areas assessed in each SFRA are outlined in the section below and the relevant SFRA to consult for information on Flood Risk is illustrated in Figure A of this report. Study Area The