Cheshire Minerals Development Framework
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Cheshire Minerals Development Framework Core Strategy & Site Specific Policies & Allocations - Issues and Options Strategic Flood Risk Assessment September 2007 Minerals Development Framework Cheshire County Council Minerals Development Framework Strategic Flood Risk Assessment Cheshire County Council – SFRA Minerals Issues and Options 1 documents. September 2007 (v1) Cheshire County Council CHESHIRE MINERALS DEVELOPMENT FRAMEWORK STRATEGIC FLOOD RISK ASSESSMENT Andy Farrow Strategic Planning Manager Waste and Planning Service Cheshire County Council Backford Hall Chester CH1 6PZ For further information please contact: Louise Hilder Daniel Stafford Tel: (01244) 976756 Tel: (01244) 972954 E-mail: E-mail: [email protected] [email protected] This document is available in alternative formats, including large print, Braille, tapes and other languages, on request from Cheshire County Council Media and Promotion Team, County Hall, Chester, CH1 1SF. Phone: 0845 11 333 11 Web site: www.cheshire.gov.uk Email: [email protected] Paper and CDrom copies can be obtained: By post: Pat Fricker Team Leader, Information Management Waste and Planning Service Cheshire County Council Backford Hall Backford Chester CH1 6PZ Tel: 01244 973766 Fax 01244 603033 Email: [email protected] Web site: www.cheshire.gov.uk/Planning/ Cheshire County Council – SFRA Minerals Issues and Options 1 documents. September 2007 (v1) Contents 1.0 Introduction 1 Planning Policy Statement 25 1 Approach to Producing SFRA 2 2.0 Summary of Flood Risk in Cheshire 3 Climate Change 3 Potential Minerals Development 4 3.0 The Weaver Gowy Catchment 6 Overview 6 Current Flood Risks and Management 7 4.0 The Upper Mersey Catchment 9 Overview 9 Current Flood Risks and Management 10 5.0 The Lower Mersey Catchment 11 Overview 11 Current Flood Risks and Management 12 6.0 The River Dee Catchment 13 Overview 13 Current Flood Risks and Management 13 7.0 Minerals Development 14 Issues at Existing Sites 14 Mitigating Flood Risk at Minerals Workings 14 Opportunities to Reduce Flood Risk 15 8.0 Conclusions 16 References 17 Appendix 1 - Historical Flooding in Cheshire 18 Table of Figures Figure 1 - Catchments in the North West (source: Mersey Estuary CFMP Scoping Report, March 2007) 3 Figure 2 - Flood risk in Cheshire and active and proposed minerals sites 5 Figure 3 - Weaver Gowy Catchment (source: Weaver Gowy CFMP Scoping Report, feb 2007) 6 Figure 4 - Upper Mersey Catchment (source: Upper Mersey CFMP Scoping Report, January 2006) 10 Figure 5 - The Mersey Estuary Catchment (source: Mersey Estuary CFMP Scoping Report, March 2007) 11 (Please note: Figures 1, 3, 4 and 5 supplied by the Environment Agency) 1.0 Introduction 1.1 Strategic Flood Risk Assessment (SFRA) is the term currently used for the type of assessment of flood risk undertaken to inform the spatial planning process at the sub-regional or local scale. However, it is unclear whether an additional SFRA is needed at the County tier as neither PPS25 nor its Practice Guide provides effective guidance on this matter. 1.2 The purpose of this report is to collect information in relation to flooding and flood risk in Cheshire as part of the baseline evidence of the Sustainability Appraisal of the Minerals Development Framework Core Strategy and Site Specific Policies and Allocations which are currently at the Issues and Options stage of Development Plan Production. Planning Policy Statement 25 (PPS25) 1.3 PPS25: Development and Flood Risk requires all Planning Authorities to carry out a SFRA to inform the development of Development Plan Documents (DPDs). PPS12: Local Development Frameworks establishes that development plans must be based upon a robust and credible evidence base. Therefore, the County Council considers that an SFRA is necessary to inform the development of both the Cheshire Minerals Development Framework (MDF) Core Strategy and Site Specific Policies and Allocations DPDs. It will also go on to inform the Sustainability Appraisals of any future Minerals DPDs. 1.4 The SFRA has been developed in consultation with the Environment Agency. 1.5 The aim of this SFRA is to refine information on the probability of flooding from all sources in Cheshire. It will also take climate change into account. It will provide the basis for applying the sequential test to the location of development, on the basis of the zones set out in Table D.1 of PPS25. These are: • Zone 1: Low Probability o This zone comprises land assessed as having a less than 1 in 1000 annual probability of river or sea flooding in any year (<0.1%) • Zone 2: Medium Probability o This zone comprises land assessed as having between a 1 in 100 and 1 in 1000 annual probability of river flooding (1% - 0.1%) or between a 1 in 200 and 1 in 1000 probability of sea flooding (0.5% - 00.1%) in any year. • Zone 3a: High Probability o This zone comprises land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%) or a 1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year. • Zone 3b: The Functional Floodplain Cheshire County Council – SFRA Minerals Issues and Options 1 documents. September 2007 (v1) o This zone comprises land where water has to flow or be stored in times of flood. 1.6 PPS25 states that non-natural or artificial flooding may arise from operational and redundant industrial processes including mining, quarrying and sand and gravel extraction as they may increase floodwater depths and velocities in adjacent areas. The effects of dewatering through sand and gravel extraction may also impact on the flood risk in the receiving water course. 1.7 The over-all aim of PPS25 is to steer new development to flood zone 1. However, minerals development presents a number of unique issues in relation to flood risk that may prevent this: • Minerals can only be worked where they are found, restricting the use of the sequential test to guide development away from areas of higher flood risk. • Sand and gravel workings are defined as “water compatible development” and are therefore appropriate in all flood zones. Therefore, the sequential test does not need to be carried out in relation to sand and gravel workings. • Other minerals workings and processing (not sand and gravel) are defined as “less vulnerable development” and are appropriate in all flood zones except Zone 3b. Again, this limits the application of the sequential test as new minerals development need only be steered away from flood zone 3b. • The greenfield/rural nature of minerals development limits flood risk and surface run-off issues. Approach to Producing SFRA 1.8 Although the issues outlined above limit the detail appropriate to this SFRA, the general flood risk issues in Cheshire in relation to minerals development will be set out with an assessment of the implications of climate change. 1.9 In line with the Environment Agency’s Catchment Flood Management Plans, the general issues will be examined on a catchment basis. The catchments within Cheshire are the Weaver Gowy, Lower Mersey and Upper Mersey (see figure 1). An examination of Environmental Statements will allow existing hydrological issues to be set out for the active mineral sites within Cheshire. This SFRA will also set out the general principles towards mitigating any flood risk issues at a site specific level and the possible opportunities that minerals development may have on reducing flood risk in the County. Cheshire County Council – SFRA Minerals Issues and Options 2 documents. September 2007 (v1) 2.0 Summary of Flood Risk in Cheshire 2.1 This section will provide an overview of the catchments that cover Cheshire and the general flood risk issues that exist within them. An examination of flood risk issues at individual active sites will also be included. Figure 1 - Catchments in the North West (source: Mersey Estuary CFMP Scoping Report, March 2007) Map supplied by the Environment Agency for use by Cheshire County Council Climate Change 2.2 Climate change is an important driver in terms of flood risk as it has catchment wide influence on peak flows across the whole of Cheshire. A figure of +20% (on peak flows) has become a simple benchmark for the allowance that should reasonably be given for climate change impacts for all flood return periods. This is in line with Defra and CFMP guidance. An allowance for the impact of climate change on tidal levels has been set for the North West of England of +2.5mm/yr up to 2025 (see table B.1 of PPS25) for North West England. Post 2025, sea level rise is predicted to be around 7mm/yr from 2025-2055, 10mm/yr from 2055-2085 and 13mm/yr from 2085 to 2115. Sea level rise may increase the chances of “tidal locking” of the lower reaches of the rivers increasing the risk of flooding. It should also be noted that extreme wave heights are expected to increase by +5% up to 2055 and +10% up to 2115 (see table B.2 of PPS25). This may increase the instances of sea defences being overtopped. Cheshire County Council – SFRA Minerals Issues and Options 3 documents. September 2007 (v1) Potential Minerals Development 2.3 The map below (figure 2) shows the topography of Cheshire, the location of the active minerals sites, the main rivers and flood zones 2 and 3, and potential mineral sites, areas of search and preferred areas (it should be noted that the proposed sites have been put forward by consultees and have not yet been through the plan making process). Due to their nature, especially sand (silica and construction) workings, the minerals sites tend to be located in the floodplains of the main rivers in Cheshire.