Blackburn with Darwen Borough Council Level 2 Strategic Flood Risk Assessment Volume 1 – Guidance Final September 2012 Quality Management Quality Management DOCUMENT INFORMATION Title: Blackburn with Darwen Borough Council Level 2 Strategic Flood Risk Assessment Owner: Rea Psillidou Version: V5.0 Status: Final Project Number: CS/051545 File Name: S:\ZWET\SheffieldBasedJobs\CS051545_Blackburn_Level_2_SFRA\Report s\Final REVISION HISTORY Summary of Changes Completed By Date of Issue Version First Draft LT 29th November 2011 1.0 2nd Draft LT 31st January 2012 2.0 Final LT/PR 27th April 2012 3.0 Amended Final PR 10th September 2012 4.0 Minor additions PR 30th November 2012 5.0 Minor amendment PR 9th January 2013 5.1 AUTHOR Name Organisation and Role Louise Tattersall Consultant, Capita Symonds Philip Raynor Associate, Capita Symonds APPROVALS Name Title Signature Date Associate Director, Capita Philip Raynor 9th January 2013 Symonds DISTRIBUTION Name Organisation and Role Rea Psillidou BwDBC, Strategic Planning Manager Laura Gorst BwDBC, Planner RELATED DOCUMENTS Date of Doc Ref Document Title Author Version Issue Blackburn with Level 1 Blackburn with Darwen Borough N/A Darwen Borough Dec 2008 1.0 Council Strategic Flood Risk Assessment Council Blackburn with Darwen Borough Council Level 2 SFRA 2 of 95 September 2012 Executive Summary Executive Summary Capita Symonds has been commissioned to prepare a Level 2 Strategic Flood Risk Assessment (SFRA) on behalf of Blackburn with Darwen Borough Council (BwDBC). This assessment builds upon the findings of the Level 1 SFRA completed in December 2008. The purpose of the Level 2 SFRA is to support the borough’s Local Development Framework (LDF) and this was initially done in response to the guidance in ‘Planning Policy Statement 25 – Development and Flood Risk’ that states that a sequential risk-based approach should be applied to decision making at all levels of the planning process. This assessment has subsequently been updated to reflect the guidance presented within the National Planning Policy Framework (NPPF) (March, 2012) and the supporting Technical Guidance to the National Planning Policy Framework (March 2012) that covers flood risk. The fundamental concepts that underpin the Level 2 SFRA are incorporated into the NPPF and the Technical Guidance to the National Planning Policy Framework (hereafter referred to as ‘the Technical Guidance’. The guidance provided in this document 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 and Exception Test (where applicable). Failure to demonstrate that such a test has been undertaken at this level 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 to reduce reliance on built flood defences, which have long-term maintenance liabilities. Within areas at risk from flooding, it is expected that development proposals will contribute to a reduction in the overall magnitude of the flood risk. SFRAs are therefore 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 principal objective of the Level 2 SFRA is to facilitate the application of the Sequential and Exception Tests. More detailed information is required where there is deemed to be development pressure in areas that are at medium or high probability of flooding and where there are no other suitable alternative areas for development after applying the Sequential Test. A Level 2 SFRA considers the detailed nature of the flood hazard, taking account of the presence of flood risk management measures such as flood defences and in doing so it allows a sequential approach to site allocation to be adopted within a flood zone. It will also allow the development of policies to ensure that development in such areas satisfies the requirements of the Exception Test. This SFRA describes the outcome of a ‘Level 2’ assessment, which is required in locations where the Level 1 SFRA indicates that there may be a need to apply the Exception Test and in which the scope of a SFRA must be widened to consider the frequency, impact, speed of onset, depth and velocity of flooding within the flood zones. This assessment therefore contains a general assessment of risk from all sources over the whole study area and also detailed analysis for key development sites where flood risk is considered a significant issue. The specific aims of the assessment are to: Inform policies and plans to ensure future developments, where appropriate, have been subjected rigorously to the applications of the Sequential and Exception Tests, satisfying PPS25. Identify strategies to limit flood risks and adapt to climate change. Ensure the safety of new development. The Level 2 SFRA has been divided into two volumes: Volume 1 – Guidance Blackburn with Darwen Borough Council Level 2 SFRA 3 of 95 September 2012 Executive Summary Volume 2 – Mapping and Assessments of Key Development Sites This report is Volume 1 of the assessment and it identifies the flood risks within the borough and provides guidance for different groups of users on the data presented within the SFRA. The supporting mapping is contained within Volume 2 which should be read in conjunction with this report. The Level 2 SFRA is a live document that is intended to be updated as new information and guidance becomes available. The outcomes and conclusions of the Level 2 SFRA may not be valid in the event of future changes to legislation, policy or revised government guidance on flood risk. It may also become invalid if the data on flood risk is updated or the baseline flooding situation changes as a result of future flood risk management measures. Decisions also require the inclusive assessment of wider planning issues and the user should be aware that changes to decision making principles affecting other planning issues can potentially affect the outcome of the risk-based Sequential Test. It is the responsibility of the user to ensure they are using the best available information. Blackburn with Darwen Borough Council Level 2 SFRA 4 of 95 September 2012 Contents Contents Quality Management ........................................................................................................ 2 Executive Summary ......................................................................................................... 3 Contents .......................................................................................................................... 5 Glossary ........................................................................................................................... 7 1.0 Introduction .............................................................................................................. 12 1.1 Background ......................................................................................................................................... 12 1.2 Linkages with Other Plans ................................................................................................................... 13 1.3 Blackburn with Darwen Study Area ..................................................................................................... 15 2.0 Flooding in Blackburn with Darwen .......................................................................... 17 2.1 Introduction .......................................................................................................................................... 17 2.2 Fluvial Flood Risk ................................................................................................................................ 18 2.3 Groundwater Flooding ......................................................................................................................... 25 2.4 Surface Water and Sewer Flooding .................................................................................................... 26 2.5 Flooding from Artificial Sources ........................................................................................................... 27 2.6 Summary of Flood Risks ..................................................................................................................... 32 3.0 How to use the Level 2 SFRA in Forward Planning ................................................. 34 3.1 Introduction .......................................................................................................................................... 34 3.2 Sequential Test .................................................................................................................................... 34 3.3 Exception Test ..................................................................................................................................... 39 3.4 Climate change .................................................................................................................................... 41 4.0 How to use the Level 2 SFRA in Development Management .................................. 43 4.1 Introduction .........................................................................................................................................