KIDBROOKE VILLAGE MASTERPLAN PHASE 2 & EXTRA“...An Exemplar CARE for Sustainable Suburbs”
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KIDBROOKE VILLAGE MASTERPLAN PHASE 2 & EXTRA“...an exemplar CARE for sustainable suburbs” illustrative plan oth proposed masterplan 10 Berkeley Homes (East Thames) Ltd 0801 - Floodcovering Risk letter Assessment & application form 14th September November 20092008 Phase 2 Kidbrooke Regeneration Project PPS25 Flood Risk Assessm ent Berkeley Homes (East Thames) Limited September 2009 QM Issue/revision Issue 1 Revision 1 Revision 2 Revision 3 Remarks DRAFT DRAFT 2 FINAL Date 14/08/2009 07/09/2009 09/09/2009 Prepared by J. Tang J. Tang J.Tang Signature Checked by J. Greene J. Greene J.Greene Signature Authorised by A. Atkinson A. Atkinson A.Atkinson Signature Project number 11012229 11012229 11012229 File reference 2229\PH2 FRA 2229\PH2 FRA 2229\PH2 FRA WSP Development and Transportation Mountbatten House Basing View Basingstoke Hampshire RG21 4HJ Tel: +44 (0)1256 318800 Fax: +44 (0)1256 318700 http://www.wspgroup.com WSP UK Limited | Registered Address Buchanan House, 24-30 Holborn, London, EC1N 2HS, UK | Reg No. 01383511 England | WSP Group plc | Offices worldwide Contents 1 Introduction 4 2 Existing Site 6 3 Proposed Developm ent 10 4 Assessm ent of Potential Sources of Flooding to the Developm ent Site 12 5 Probability 15 6 Clim ate Change 17 7 Flood Risk M anagem ent M easures 18 8 Residual Risk 20 9 Conclusion and Recom m endations 21 Appendices APPENDIX A – REFERENCES APPENDIX B – EXISTING SITE APPENDIX C – PROPOSED DEVELOPMENT APPENDIX D – PLANNING POLICY AND CONTEXT APPENDIX E – DRAINAGE STRATEGY APPENDIX F – FLOOD RISK MAPPING 1 Introduction 1.1 BACKGROUND 1.1.1 WSP has been commissioned by Berkeley Homes (East Thames) Limited to carry out a Supplementary Flood Risk Assessment and Surface Water Drainage Strategy for the Phase 2 Area of development at the Kidbrooke Regeneration Site, located near to Greenwich in Greater London. 1.1.2 The Berkeley Homes (East Thames) Limited Application Site, for which this Flood Risk Assessment has been prepared to support, sits within the wider Kidbrooke Development Area (KDA). Berkeley Homes received Outline Planning Permission for the whole site in March 2009. The Application included a Detail Application for the Phase 1 area. 1.1.3 As part of the original application a Flood Risk Assessment was prepared by WSP in November 2008 to assess the potential flood risk at the site and to define the over-arching drainage strategy. Two Addendums to the Flood Risk Assessment were later issued to the Environment Agency to support the development in Phase 1 and to discharge the Planning Condition relating to the modelling of the Lower Kid Brook. These reports included further 1-D and 2-D modelling of the Lower Kid Brook watercourse. 1.1.4 A further planning condition was placed on development at the site to ensure that later phases were assessed based on the best available data. This Supplementary Flood Risk Assessment has been prepared to support development in the Phase 2 area of the site and to satisfy the Planning Condition. 1.1.5 The Phase 2 area of the Kidbrooke Regeneration Project will provide new residential apartment blocks and properties to the west of Kidbrooke Park Road (A2213), including Extra Care Units and the adjacent section of the Metropolitan Open Land. 1.2 OBJECTIVE OF THE STUDY 1.2.1 The objective of the study was to undertake a supplementary Flood Risk Assessment (FRA) in accordance with Planning Policy Statement 25 – Development and Flood Risk, (PPS25) to support the Environmental Impact Assessment (EIA) and the detailed Reserved Matters Application for the Phase 2 Area. This Flood Risk Assessment assesses any implications to the previously approved principles as a result of modifications to the Masterplan. 1.2.2 The study assesses flood risk to: The Phase 2 area of the proposed development and, Any impact on flood risk to other land as a result of the Phase 2 development proposals. 1.2.3 This report also provides an outline drainage strategy for the surface water flows from the proposed development which reconfirms the principles of the strategy previously agreed with the Environment Agency. The strategy demonstrates that the principles of attenuation to Greenfield runoff rates can still be achieved as the Masterplan and site plans have progressed and evolved. 11012229 N:\Kidbrooke\PHASE 2\TEXT\REPORTS\090908 KIDBROOKE 4 PH2 FRA.doc 1.3 STUDY M ETHODOLOGY 1.3.1 The previous appraisal process consisted of a desk study, data research and consultation with regulatory bodies and third parties. 1.3.2 A list of documents used to obtain data in relation to the site and the proposed development is provided in Appendix A. Consultation was sought with the Environment Agency, and copy of their response has been provided. 1.3.3 Preliminary calculations for surface water flows have been undertaken based on the requirements of the London Plan and the adopted Supplementary Planning Documents for Kidbrooke. These calculations take into account the conditions at the site, existing drainage systems and current development proposals. 1.3.4 This is an assessment of potential flooding from all principle sources, including fluvial, tidal, surface run-off, overland flows, groundwater, sewers and man made infrastructure. The assessment also identifies and examines the residual flood risk to the proposed development. 1.3.5 Whilst completing the assessment, consideration has been given to the Practice Guide June 2008. The assessment has been undertaken in accordance with CIRIA C624, ‘Development and Flood Risk - Guidance for the Construction Industry' (2004) and Flood Risk Assessment Guidance for New Development, Phase 2, R & D Technical Report FD2320/TR2 (2005). 1.4 LIM ITATIONS 1.4.1 Whilst furthermore detailed modelling work has been undertaken by WSP to discharge planning conditions at the time of writing this report the results of this modelling are being reviewed by the Environment Agency. For this reason two flood levels are used in the report, and in keeping with the precautionary approach, the highest predicted flood level has been considered in the recommendations. These flood levels are referred to as follows: EA Detailed Modelling Level (Results of the River Ravensbourne Detailed Flood Risk Mapping Study – October 2006) WSP 2D modelled flood level. The WSP modified Ravensbourne TUFLOW Model of the Quaggy – 2009 draft model). 1.4.2 It should be noted that the flood levels referred to above do not impact on the site; both the Environment Agency’s detailed mapping and WSP’s 2D modelling show that the Phase 2 Area of the Kidbrooke Development Site is situated outside of the 1 in 100 year + climate change allowance event. 1.4.3 This Flood Risk Assessment has been prepared on the best available information at the time of making this application. 11012229 N:\Kidbrooke\PHASE 2\TEXT\REPORTS\090908 KIDBROOKE 5 PH2 FRA.doc 2 Existing Site 2.1 SITE LOCATION 2.1.1 The Kidbrooke Regeneration Site is located in Kidbrooke, Greenwich, Greater London and is situated immediately east of Blackheath Park with Sutcliffe Park forming the western and southern boundaries. 2.1.2 The Phase 2 area is located in the most south western section of the site to the west of Kidbrooke Park Road (A2213) and immediately north of Weigall Road. To the north of the Phase 2 area is the area of the existing Ferrier Estate which is proposed to be developed as Phase 5 (the last phase of development). 2.1.3 The Phase 2 Application area of the Kidbrooke Development will cover approximately 5.57ha. This area is currently occupied by the dilapidated Ferrier Estate, a 1960’s de-graded housing estate which includes mainly high rise apartment blocks. Refer to Figure 1, Site Location Plan in Appendix B. 2.2 SITE DESCRIPTION 2.2.1 Table 2.1 describes the general site characteristics. A key feature plan (WSP Drawing No. 2229/GA/201) is included in Appendix B. Table 2.1 Characteristics of the site Area Phase 2 = 5.57 ha including Extra Care Units General Topography Phase 2 of the Kidbrooke Site generally slopes from north to south. Levels range from 28.00m AOD along the existing Gallas Square, north of Phase 2 area, to 21.50m AOD along Weigall Road, south-west of the Phase 2 area. Areas of artificially raised landscaping present within existing estate. Existing surfacing Approximately 75 % impermeable. Current use Phase 2 – Occupied by dilapidated Ferrier Estate Boundaries North Existing developments fronting Moorhead Way South Weigall Road East Kidbrooke Park Road (A2213) West Moorhead Way Access Vehicular: Weigall Road connecting onto Kidbrooke Park Road (A2213) and surrounding road networks Pedestrian: Permeable street network surrounds site 2.2.2 A Topographical Survey of the Application Site was undertaken by ELS Land Surveys in September 2008. An extract of the survey relating to the Phase 2 area plotted at a scale of 1:1000 is provided in Appendix B. 2.2.3 The survey shows that the Phase 2 site has levels from approximately 21.50m to 28.00m AOD. The average level of the site is approximately 24.44m AOD. 11012229 N:\Kidbrooke\PHASE 2\TEXT\REPORTS\090908 KIDBROOKE 6 PH2 FRA.doc 2.2.4 The Topographical Survey shows that Phase 2 and the area proposed for the Extra Care Units generally slope in a southern direction towards the open channel of the River Quaggy located west of Sutcliffe Park. 2.3 DRAINAGE 2.3.1 Thames Water records, (Appendix B), show that there are a number of public surface water sewers and combined sewers in the area, albeit the large majority of the existing Ferrier Estate is privately drained to one of two culverted watercourses.