Flood Risk Statement Proposed Residential Conversion 4-8 Rodney
Total Page：16
File Type：pdf, Size：1020Kb
Flood Risk Statement Proposed Residential Conversion 4-8 Rodney Street, London, N1 9JH Prepared for: Dentons Sipp D J Baker, A Baker, D R Booker, M J Cue and M C Thompson Prepared by: RMA Environmental Ltd Date: 14th March 2014 Project Number: RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson Issued by: RMA Environmental Limited Suite 4 Swallow Court Devonshire Gate Nr Tiverton Devon EX16 7EJ www.rma-environmental.co.uk Client: DENTONS SIPP D J BAKER, A BAKER, D R BOOKER, M J CUE AND M C THOMPSON Project: PROPOSED RESIDENTIAL CONVERSION, 4-8 RODNEY STREET, LONDON, N1 9JH Title: FLOOD RISK STATEMENT Status: DRAFT Date: MARCH 2014 Document Production Record: Issue Number Name Signature Prepared Ben Lewis Checked Rob Murdock Approved Rob Murdock Document Revision Record: Issue Number Date Revision Details 1 12th March 2014 Draft 2 14th March 2014 Final RMA Environmental Limited has prepared this report in accordance with the instructions of the above named client for their sole and specific use. Any third parties who may use the information contained herein do so at their own risk. Issue 2 RMA Environmental March 2014 RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson CONTENTS 1 INTRODUCTION ......................................................................................................... 1 Background ............................................................................................................................ 1 Site Location ........................................................................................................................... 1 Proposed Development .......................................................................................................... 1 2 BASELINE ENVIRONMENTAL CONDITIONS ............................................................ 2 Topography And Land Use .................................................................................................... 2 Hydrology ............................................................................................................................... 2 Flood Zone Classification ....................................................................................................... 2 Historic Flooding..................................................................................................................... 2 Geology And Hydrogeology ................................................................................................... 3 3 EXTERNAL FLOOD RISK ........................................................................................... 4 Flooding Mechanisms ............................................................................................................ 4 4 DRAINAGE STRATEGY ............................................................................................. 6 Introduction ............................................................................................................................. 6 Designing For Exceedance Events ........................................................................................ 6 5 CONCLUSIONS .......................................................................................................... 7 FIGURES Figure 1.1: Site Location Plan Figure 2.1: EA Indicative Flood Map APPENDICES Appendix A: SFRA Map 11 Appendix B: SFRA Map 13 Issue 2 RMA Environmental March 2014 RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson 1 INTRODUCTION Background 1.1. RMA Environmental Limited was commissioned by Dentons Sipp D J Baker, A Baker, D R Booker, M J Cue and M C Thompson to prepare a Flood Risk Statement (FRS) for a proposed residential conversion at 4-8 Rodney Street, London, N1 9JH. 1.2. This FRS has been prepared to support a Prior Notification application submitted to the London Borough of Islington Council. The Prior Notification is submitted in accordance with the Town and Country Planning (General Permitted Development) (Amendment) Order 2013. 1.3. The FRS has been prepared to identify if there will be a material change to the risk of flooding at the site or elsewhere as a result of the proposed development. The proposed development falls under permitted development rights and therefore an FRA in accordance with the National Planning Policy Framework (NPPF) is not required. Site Location 1.4. The site is located at Rodney Street, to the north of Pentonville Road (A501) in the London Borough of Islington (refer to Figure 1.1) and is centred on National Grid Reference (NGR) TQ 30918 83131. 1.5. Further details on topography, hydrology and sources of flood risk at the site are set out in Sections 2 and 3. Proposed Development 1.6. The proposed development includes the change of use of existing office floor space to create approximately 17 residential units, these will comprise of 16 one bedroom and 1 three bedroom apartments. Issue 2 RMA Environmental March 2014 1 RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson 2 BASELINE ENVIRONMENTAL CONDITIONS Topography and Land Use 2.1. Ordnance survey mapping of the site and surrounding area identifies that the proposed development is elevated approximately 30 metres Above Ordnance Datum (mAOD; refer to Figure 1.1) and has a gradual downward slope in a westerly direction. 2.2. The site is occupied by a five storey building with a two storey extension to the north and east. The property has a GEA of 1,255 sqm. Rodney House is located immediately to the north, office uses to the east and a car rental facility to the south. Hydrology 2.3. There are no ‘main rivers’1 or ordinary watercourses within a 1 km radius of the site. 2.4. Map 11 of the North London Strategic Flood Risk Assessment (SFRA: Mouchel, August 2008) shows that the site is located within the River Fleet catchment (refer to Appendix A). However, this has been entirely incorporated within the sewer network which is owned and maintained by Thames Water. 2.5. The Regent’s Canal is located approximately 320 m to the north of the site and is open where it joins the Grand Union Canal. The Regent’s Canal enters a tunnelled section before re-opening approximately 770 m east of the site. 2.6. A covered reservoir is located approximately 200 m to the south-east of the site. There are no other significant water interests within a 1 km radius of the site. Flood Zone Classification 2.7. The Environment Agency (EA’s) indicative flood map2 (refer to Figure 2.1) shows that the site lies entirely within Flood Zone 1 (low risk). Land in Flood Zone 1 is predicted to flood with an annual probability of less than 0.1% from rivers and the sea. Historic Flooding 2.8. The British Hydrological Society database3 of historical flood events has been reviewed for records of flooding in the area and no specific data has been found for the site or its immediate vicinity. 2.9. Details of flood records contained in the SFRA and Preliminary Flood Risk Assessment for London Borough of Islington (PFRA; Halcrow, April 2011) are discussed in Section 3. 1 Main river is defined by the EA as any watercourse that contributes significantly to the hydrology of a catchment. 2 EA Indicative Flood map available at: http://www.environment-agency.gov.uk/homeandleisure/37793.aspx 3 Chronology of British Hydrological Events (www.dundee.ac.uk/geography/cbhe/) Issue 2 RMA Environmental March 2014 2 RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson Geology and Hydrogeology 2.10. The British Geological Survey (BGS) online Geology of Britain Viewer shows that the site is underlain by the bedrock geology of the London Clay Formation consisting of clay, silt and sand. There is no recorded superficial geology. 2.11. The underlying bedrock geology is classified as Unproductive Strata by the EA, which is defined as: “rock layers or drift deposits with low permeability that have negligible significance for water supply or base river flow.” 2.12. The site is not located within a groundwater Source Protection Zone (SPZ). Issue 2 RMA Environmental March 2014 3 RMA-C1316 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS M J Cue and M C Thompson 3 EXTERNAL FLOOD RISK Flooding Mechanisms 3.1. This section identifies and reviews potential sources of flood risk to the site in line with best practice guidance. Fluvial and Tidal Flood Risk 3.2. As discussed in Section 2, the EA’s indicative flood map (Figure 2.1) shows that the site lies entirely within Flood Zone 1; this is defined by the EA as land with ‘little or no flood risk’. 3.3. The Flood Zone 34 floodplain associated with the River Thames is at a considerable distance and at an elevation of approximately 20 m lower than the site. It is therefore concluded that the site would remain in Flood Zone 1 for its assumed operational lifetime (i.e. 100 years). Canal and Reservoir Flood Risk 3.4. It is considered that flood risk from the Grand Union and Regent’s Canals is minimal as it is understood that none of the canals are on embankments, surface water inputs are likely to be minimal and water levels are controlled. 3.5. The EA risk of flooding from reservoirs map indicates that the site is not located within a reservoir flood risk zone. 3.6. Therefore,