Michael D Joyce Associates LLP Flood Risk Assessment
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Flood Risk Assessment FOXCOVERT FISHERIES STOKEHAM ROAD LANEHAM RETFORD for Mr. S. Ashworth Report Number 4093 February 2021 Michael D Joyce Associates LLP Geotechnical and Geoenvironmental Consultants Charnock Court 6 South Parade Wakefield West Yorkshire WF1 1LR UK T +44(0)1924 360458 E [email protected] W www.geoenvironmental.co.uk Flood Risk Assessment for Foxcovert Fisheries, Stokeham Road, Laneham, Retford Flood Risk Assessment FOXCOVERT FISHERIES, STOKEHAM ROAD, LANEHAM, RETFORD Contents 1. Introduction 2. The Property 3. Geology 4. Site Specific Flood Risk Assessment 5. Conclusions and Recommendations Figures Figure 1 Site Location Figure 2 Site Plan Appendices Appendix 1 Environment Agency Flood Map for Planning Appendix 2 Correspondence from the Environment Agency Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 1 1 INTRODUCTION 1.1 At the request of Mr. Simon Ashworth, a Flood Risk Assessment has been carried out at Foxcovert Fisheries in Laneham near Retford. It is proposed to use a small section of the site along the western boundary for the parking of mobile touring caravans. 1.2 The Flood Risk Assessment has been prepared in accordance with The National Planning Policy Framework (NPPF), which is the official document that regulates the assessment of flood risks and their appropriate mitigation measures in the planning process. To accompany the NPPF there is the “Technical Guidance to the National Planning Framework” document of March 2012. This replaces PPS25: Development and Flood Risk. 1.3 The National Planning Policy Framework sets strict tests to protect people and property from flooding which all local planning authorities are expected to follow. Where these tests are not met, national policy is clear that new development should not be allowed. The mains steps to be followed are set out below which, in summary, are designed to ensure that if there are better sites in terms of flood risk, or a proposed development cannot be made safe, it should not be permitted. 1.4 In areas at risk of flooding (including change of use) or for sites of 1 hectare or more, developers undertake a site-specific flood risk assessment to accompany applications for planning permission. 1.5 A site-specific flood risk assessment is carried out by (or on behalf of) a developer to assess the flood risk to and from a development site. Where necessary in the Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 2 National Planning Policy Framework, the assessment should accompany a planning application submitted to the local planning authority. The assessment should demonstrate to the decision-maker how flood risk will be managed now and over the development’s lifetime, taking climate change into account, and with regard to the vulnerability of its users. 1.6 The information provided in the flood risk assessment should be credible and fit for purpose. Site-specific flood risk assessments should always be proportionate to the degree of flood risk and make optimum use of information already available, including information in a Strategic Flood Risk Assessment for the area, and the interactive flood risk maps available on the Environment Agency’s web site. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 3 2 THE PROPERTY 2.1 Foxcovert Fisheries is located off Stokeham Road, approximately 10km southeast of Retford. The Ordnance Survey National Grid Reference is 479240, 376240. It presently comprises two fishing lakes with a fisherman’s bothy and car park at the eastern end of the site. The lakes do not have an inlet or outlet, and represent the natural groundwater level. According to Mr. Ashworth, the water level does not vary very much, and is generally 1m below groundlevel most of the year. 2.2 It is proposed to use a section of the westernmost part of the site as an area for up to ten mobile touring caravans. This is on a raised area, approximately 0.5m above the rest of the site. The existing site layout is shown on figure 1, with the area proposed for caravans also shown. The area will be accessed via a gravel track. 2.3 LiDAR Data (OS Terrain 50 DTM) from the British Geological Society indicates that the site for the caravans lies at 8.4 mAOD, with the adjacent pond level at 7.5 mAOD. 2.3 Open drains lie just to the northern and southern boundaries of the site. Mr. Ashworth is not aware of the site as ever having flooded. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 4 Area proposed for Caravans View towards the Bothy from area proposed for caravans illustrating water levels Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 5 Area proposed for Caravans View towards the Bothy from area proposed for caravans Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 6 3 GEOLOGY 3.1 According to the British Geological Survey’s (BGS) GeoIndex mapping, the site is underlain by alluvium comprising clay, silt, sand and gravel. Bedrock comprises the mudstone of The Mercia Mudstone Group which is Triassic in Age. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 7 4 SITE SPECIFIC FLOOD RISK ASSESSMENT 4.1 The assessment is based on the Environment Agency’s maps of flood risk zones. These cover all of England and Wales and map areas prone to flooding in terms of the following: Zone 1 - Low Probability (Little or No Risk) This zone comprises land assessed as having a less than 1 in 1000 annual probability of river or sea flooding in any year. There are no development constraints. Zone 2 - Medium Probability (Low to Medium Risk) This zone comprises land assessed as having between a 1 in 100 (1%) and 1 in 1000 (0.1%) annual probability of river flooding or between a 1 in 200 and 1 in 1000 annual probability of sea flooding in any year. Zone 3a - High Probability (High Risk) This zone and the site itself comprises land assessed as having a 1 in 100 or greater annual probability of river flooding or a 1 in 200 or greater annual probability of flooding from sea in any year. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 8 Zone 3b - Functional Floodplain This zone comprises land where water has to flow or be stored in times of flood. The annual probability that such land will flood will be 1 in 20 or greater. 4.2 In terms of vulnerability to flooding appropriate developments for each flood zone are given. The proposed use of the site as a caravan site falls under the “more vulnerable” category. Flood Essential Water Highly More Less Vulnerability Infrastructure Compatible Vulnerable Vulnerable Vulnerable Zone Development 1 Appropriate Appropriate Appropriate Appropriate Appropriate 2 Appropriate Appropriate Exception Appropriate Appropriate test required 3a Exception test Appropriate Inappropriate Exception Appropriate required Test required 3b Exception test Appropriate Inappropriate Inappropriate Inappropriate required 4.3 A search has been made of the Environment Agency’s on-line Flood Map for Planning and the report is attached in Appendix 1. The site lies in Zone 3. According to the present owner of the property, the area has not flooded, even during the extensive flooding last year. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 9 4.4 The Environment Agency has also been contacted directly in order to determine if any additional information is available. The response from the Environment Agency is presented in Appendix 2. 4.5 The Environment Agency provided modelled flood level data for the River Trent at its nearest point to the site. Based on a 1 in 100 year flood event, the flood level would not exceed 7.5 mAOD, compared to the site ground level of 8.4 mAOD. 4.6 Even if a climate change allowance of +20% is assumed, the maximum flood level would be 9 mAOD, i.e. 500mm above existing ground level. As such, the area for the caravans is proposed to be raised to 9 mAOD (+0.5m) and consequently, will be unaffected by flooding. Surface Water Management 4.7 The proposed use of the site will have no effect on the current surface water drainage of the site. No hardstanding is proposed and surface water will infiltrate the ground as it does at present. Future Users of the Site 4.8 It is proposed that a maximum of ten touring caravans will occupy the site at any one time. Michael D Joyce Associates LLP Report No. 4093 Flood Risk Assessment - Foxcovert Fisheries, Stokeham Road, Laneham, Retford 10 5 CONCLUSIONS AND RECOMMENDATIONS 5.1 The site falls within the “More Vulnerable” category in respect of the proposed use as a caravan park. This requires an ‘Exception Test’ be carried out. This essentially comprises two parts; i. Sustainability benefits to the community outweigh the flood risks ii. That it will be safe for its lifetime, without increasing the flood risk elsewhere. Commentary on the sustainability benefits of the proposals is outside the scope of this report, as this is essentially a planning issue. 5.2 The current 1 in 100 year flood level event corresponds to a flood level of 7.5 mAOD which is below current ground level. If a climate change allowance of +20% is factored in, the maximum flood level is 9 mAOD, over the next 100 years 5.3 It is proposed that the area for the caravans will be at 9 mAOD, which is 0.6m above the general ground level of the site.