Unit 1A, Botley Road, Oxford, Ox2 0Hd
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UNIT 1A, BOTLEY ROAD, OXFORD, OX2 0HD FLOOD RISK ASSESSMENT Final Report v1.1 March 2021 Weetwood Services Ltd Suite C22 Joseph’s Well Hanover Walk Leeds LS3 1AB 0113 244 1377 [email protected] www.weetwood.net Unit 1A, Botley Road, Oxford, OX2 0HD Flood Risk Assessment Report Title Unit 1A, Botley Road, Oxford, OX2 0HD Flood Risk Assessment Final Report v1.1 Client Westminster Project Services Limited Date of issue 23 March 2021 Prepared by Kevin Tilford BSc MSc PhD MBA CWEM FCIWEM CEnv Managing Director Checked by: Keely Bonser BSc (Hons) MSc PhD Associate Director Approved by Kevin Tilford BSc MSc PhD MBA CWEM FCIWEM CEnv Managing Director This document has been prepared solely as a Flood Risk Assessment for Westminster Project Services Limited. This report is confidential to Westminster Project Services Limited and Weetwood Services Ltd accepts no responsibility or liability for any use that is made of this document other than by Westminster Project Services Limited for the purposes for which it was originally commissioned and prepared. ©Weetwood 5135/FRA/Final/v1.012021-03-23 www.weetwood.net i Unit 1A, Botley Road, Oxford, OX2 0HD Flood Risk Assessment Contents Signature Sheet i Contents ii List of Tables, Figures & Appendices iii 1 INTRODUCTION............................................................................................................................ 1 1.1 Purpose of Report ..................................................................................................................................................... 1 1.2 Structure of the Report ............................................................................................................................................. 1 1.3 Relevant Documents ................................................................................................................................................. 1 2 SITE DETAILS AND PROPOSED DEVELOPMENT............................................................................ 2 2.1 Site Location .............................................................................................................................................................. 2 2.2 Existing and Proposed Development ........................................................................................................................ 2 2.3 Waterbodies in the Vicinity of the Site ..................................................................................................................... 2 2.4 Topography ............................................................................................................................................................... 3 2.5 Flood Zone Designation ............................................................................................................................................. 3 3 PLANNING POLICY AND GUIDANCE ............................................................................................. 6 3.1 National Planning Policy and Guidance ..................................................................................................................... 6 3.2 Local Planning Policy and Guidance .......................................................................................................................... 6 4 REVIEW OF FLOOD RISK ............................................................................................................... 8 4.1 Sequential Test and Exception Test ........................................................................................................................... 8 4.2 Historical records of flooding .................................................................................................................................... 8 4.3 Flood defences .......................................................................................................................................................... 9 4.4 Flood Risk from the River Ribble ............................................................................................................................... 9 4.5 Flood Risk from Surface Water ................................................................................................................................ 12 4.6 Flood Risk from Reservoirs, Canals and Other Artificial Sources ............................................................................ 12 4.7 Flood Risk from Groundwater ................................................................................................................................. 12 5 FLOOD RISK MITIGATION MEASURES ........................................................................................ 14 6 SURFACE WATER MANAGEMENT .............................................................................................. 15 7 SUMMARY AND RECOMMENDATIONS ..................................................................................... 16 ©Weetwood 5135/FRA/Final/v1.012021-03-23 www.weetwood.net ii Unit 1A, Botley Road, Oxford, OX2 0HD Flood Risk Assessment List of Tables Table 1: Peak Modelled Water Levels ............................................................................................................................... 10 List of Figures Figure 1: Site Location and Watercourses .......................................................................................................................... 2 Figure 2: Digital Terrain Model - LiDAR ............................................................................................................................... 3 Figure 3: Flood Map for Planning ........................................................................................................................................ 4 Figure 4: Flood Map (Main Rivers) ...................................................................................................................................... 4 Figure 5: Functional Floodplain ........................................................................................................................................... 5 Figure 6: Extent of Historic Flooding ................................................................................................................................... 8 Figure 7: Recorded Flood Events ........................................................................................................................................ 9 Figure 8: Model Node Locations ....................................................................................................................................... 10 Figure 9: Peak Flood Depth in the Vicinity of the Site....................................................................................................... 11 Figure 10: Flood Hazard (1 in 100 AEP plus 35% climate change event) .......................................................................... 11 Figure 11: Flood Risk from Surface Water ........................................................................................................................ 12 Figure 12: Risk of Reservoir Flooding ................................................................................................................................ 13 Figure 13: JBA Groundwater Flood Map ........................................................................................................................... 13 Figure 14: Environment Agency Flood Warning Areas ..................................................................................................... 14 List of Appendices Appendix A: Existing and Proposed Site Layout ©Weetwood 5135/FRA/Final/v1.012021-03-23 www.weetwood.net iii Unit 1A, Botley Road, Oxford, OX2 0HD Flood Risk Assessment 1 INTRODUCTION 1.1 PURPOSE OF REPORT Weetwood Services Ltd ('Weetwood') has been instructed by Westminster Project Services Ltd to prepare a Flood Risk Assessment (FRA) report to accompany a planning application for proposed changes to Unit 1a Botley Road, Oxford (“the site”). The assessment has been undertaken in accordance with the requirements of the revised National Planning Policy Framework (NPPF) updated on 19 June 2019 and the National Planning Practice Guidance (NPPG) updated on 1 October 2019. 1.2 STRUCTURE OF THE REPORT The report is structured as follows: Section 1 Introduction and report structure Section 2 Presents national and local flood risk and drainage planning policy Section 3 Provides background information relating to the development site, the development proposals, ground conditions and existing site access arrangements Section 4 Assesses the potential sources of flooding to the development site Section 5 Presents flood risk mitigation measures based on the findings of the assessment Section 6 Addresses the effect of the proposed development on surface water runoff Section 7 Presents a summary of key findings and recommendations 1.3 RELEVANT DOCUMENTS The assessment has been informed by the following documents: • Oxford City Level 1 Strategic Flood Risk Assessment, November 2017 • West Oxford / New Botley Area Flood Response Plan, Oxford Area Flood Partnership, August 2014 • Oxford City Council pre-application opinion letter dated 8 January 2021 (letter ref: 20/03265/PAC) • Oxford City Council Sustainable Drainage - Design and Evaluation Guide, 2018 • Oxford Baseline Hydraulic Modelling Report, CH2M, Doc ref: RP-HY-0147, March 2018 ©Weetwood 5135/FRA/Final/v1.012021-03-23 www.weetwood.net 1 Unit 1A, Botley Road, Oxford,