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.

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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/)

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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).

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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, it is concluded that there is a negligible annual flood risk to the site from these sources.

Surface Water Flood Risk

3.7. A review of the SFRA has identified that there are no historic records of surface water flooding at the site.

3.8. The London Borough of Islington Preliminary Flood Risk Assessment (PFRA; Halcrow, April 2011) has been reviewed and the site is not shown to be located within a Local Flood Risk Zone.

3.9. Furthermore, the EA risk of flooding from surface water map identifies that the site is at a ‘Very Low’ risk, which is defined as follows: “very low means that each year, this area has a chance of flooding of less than 1 in 1000 (0.1%).” Rodney Street, to the west of the site, is also shown to be in an area of ‘Very Low’ risk of surface water flooding.

3.10. It is concluded that, based on information contained in the PFRA and the EA data, that the site has a negligible annual risk of flooding from surface water.

4 Flood Zone 3 is defined as high risk (with an annual probability of flooding of greater than 0.5% for tidal areas and greater than 1.0% for rivers).

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Sewer and Burst Mains Flood Risk

3.11. Map 13 of the SFRA (refer to Appendix B) shows the number of sewer flooding incidents by postcode for the period August 1997 to August 2007. This has been extracted from information provided by Thames Water and indicates that up to three flood events have occurred within proposed development postcode area.

3.12. The precise location, scale and exact cause of the individual flood events were unavailable for the SFRA, therefore flood records were identified by postcode only. Sewer flooding generally results in localised short term flooding caused by intense rainfall events which surcharge the drainage system. Furthermore, localised variables, such as the presence of buildings, roads, walls and fences influence the behaviour of surface water and therefore the outcome of a sewer flood event cannot be clearly predicted.

3.13. Similar to sewer flooding, water mains flooding cannot be clearly predicted and the extent of flooding will depend on the size of main, location, duration and localised variables.

3.14. There are no records of water mains flooding within the local area; however, it cannot be definitely proven that the site is not at any risk of flooding from this source. Therefore, it is concluded that a negligible to low annual probability of flooding from sewers and burst mains is appropriate for the proposed development.

Groundwater Flood Risk

3.15. The SFRA states that “Very few groundwater flooding records have been provided by the EA and all those that are recorded lie within the London Borough of Enfield.” The site is underlain by the London Clay Formation and no superficial deposits have been recorded at the site.

3.16. It is therefore concluded that the site has a negligible annual flood risk from groundwater sources.

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4 DRAINAGE STRATEGY

Introduction

4.1. The NPPF states that those proposing development are responsible for drainage designs which reduce flood risk to the development and elsewhere, potentially through the use of Sustainable Drainage Systems (SUDS).

4.2. Surface water arising from a developed site should, as far as is practicable, be managed to mimic the surface water flows arising from the site prior to the proposed development, while reducing the flood risk to the site itself and elsewhere.

4.3. In this instance, there is no change in the impermeable area at the site as the proposed development is an internal conversion and the site is already 100% hardstanding. Therefore, there will be no change in the amount of surface water leaving the site and, as such, there is no requirement (or opportunity) to alter the site’s current drainage arrangement. It is anticipated that the site currently discharges to either surface water or combined sewer.

Designing for Exceedance Events

4.4. Current best practice guidance on flood risk requires an evaluation of how rainfall events beyond the design capacity of the proposed drainage system would be managed and what effects they are likely to have on flood risk at the site or surrounding areas.

4.5. For the proposed development, should a rainfall event exceeding the 100 year plus climate change event occur, it is expected that some shallow ponding may occur adjacent to the site and excess surface water is likely to flow towards Rodney Street to the west.

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5 CONCLUSIONS

5.1. This 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.

5.2. The EA’s indicative flood map for the area shows that the site lies entirely within Flood Zone 1 and, therefore, fluvial and tidal flood risk are considered to be low.

5.3. This FRS has also assessed flood risk to the proposed development from other sources including other waterbodies, surface water, sewers, burst mains and groundwater. For all of these sources, it is concluded that the annual probability of flood risk to the site is either negligible or negligible to low.

5.4. The NPPF states that those proposing development are responsible for drainage designs which reduce flood risk to the development and elsewhere, potentially through the use of Sustainable Drainage Systems (SUDS).

5.5. In this instance, there is no change in the impermeable area at the site as the proposed development is an internal conversion and the site is already 100% hardstanding. Therefore, there will be no change in the amount of surface water leaving the site and, as such, there is no requirement (or opportunity) to alter the site’s current drainage arrangement. It is anticipated that the site currently discharges to either surface water or combined sewer.

5.6. This FRS has therefore demonstrated that there will be no increase in flood risk at the site or elsewhere as a result of the proposed development and that the development itself has a negligible or negligible to low risk of flooding.

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Figures

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Figure 1.1: Site Location Plan

Project Name: Rodney Street, London

Client: Dentons Sipp D J Baker, A Baker, D R Booker, MJ Cue and M C Thompson

Project Number: RMA-C1316

Date: 14/03/2014

Drawn by: RMA Environmental/ML

RMA Environmental Limited Suite 4, Swallow Court, Devonshire Gate, Tiverton, Devon, EX16 7EJ Tel: 01884 842740 Ordnance Survey © Crown Copyright 2011. All rights reserved. Licence number 100022432 Web: www.rma-environmental.co.uk KEY: Approximate Site Location

Figure 2.1: Indicative Flood Map

Project Name: Rodney Street, London

Client: Dentons Sipp D J Baker, A Baker, D R Booker, MJ Cue and M C Thompson

Project Number: RMA-C1316

Date: 14/03/2014

Drawn by: RMA Environmental/ML

RMA Environmental Limited Suite 4, Swallow Court, Devonshire Gate, Tiverton, Devon, EX16 7EJ Tel: 01884 842740 Ordnance Survey © Crown Copyright 2011. All rights reserved. Licence number 100022432 Web: www.rma-environmental.co.uk Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS

M J Cue and M C Thompson

Appendix A: SFRA Map 11

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Turkey and Cuffley Brooks & Tributaries Rammey Marsh, Cobbins Brook & Tributaries Unknown

Barnet Ditches & Mimmshall Brook

Hertfordshire

Unknown

Essex

Enfield Salmon's Brook, Boundary Ditch & Tributaries

Unknown

River Ching

Barnet Dollis Brook & Tributaries Pymmes Brook Silk Stream & Tributaries

Harrow

Banbury Reservoir

Waltham Forest Unknown Moselle Brook

Redbridge Haringey

Stonebridge & Hermitage Brook

Dagenham Brook

Unknown Unknown

Hackney Brook

Unknown

Brent Unknown Unknown River Brent & Tributaries Hackney Unknown

Islington Regents Canal Unknown Camden

River Fleet Unknown

Newham River Westbourne

Shoreditch

Unknown Blackditch Tower Hamlets Westminster Counters Creek & Park's Ditch Stamford Brook River Walbrook Unknown Unknown

River Tyburn City of London

All design, comments and recommendations are done so on behalf of Mouchel Client Parkman and no individual responsibility is taken or implied in anyway, by recieving and acting on this infomation you, the client or any third party, are accepting that no North London Waste Plan Legend individual is personally liable in contract, tort or breach of statutory duty (including negligence). Project North London Strategic Flood Risk Assessment Borough Boundaries This map is based upon Ordance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office. Crown copyright. Unauthorised reproduction infringes Crown copyright and may lead to Purpose Drawing Title Canals prosecution or civil proceedings. Information Map 11: FEH Catchments and Watercourses Data Origin Drawn SL Chckd KR Apprvd FP Watercourses FEH catchments taken from FEH v2 (2006) Layer drawn by Mouchel. Watercourse Date 07/08/08 Date 07/08/08 Date 08/08/08 data provided by the EA. Draft Scale (at A1 size) Issuing Office Sutton Coldfield Drawing Number Rev B Issue 1:40,000 Telephone 0121 355 8949 722586/011 Dentons Sipp D J Baker, A Baker, D R Booker, 4-8 Rodney Street, Residential Conversion FRS

M J Cue and M C Thompson

Appendix B: SFRA Map 13

Issue 2 RMA Environmental March 2014 10 RMA-C1316 Hertfordshire

Essex

Enfield

Barnet

Harrow

Waltham Forest

Haringey Redbridge

Brent

Hackney

Islington Camden

Newham

Tower Hamlets Westminster

City of London

Legend Note (Data not mapped) All design, comments and recommendations are done so on behalf of Mouchel Client Parkman and no individual responsibility is taken or implied in anyway, by recieving North London Waste Plan LB of Islington Emergency Planning Unit responded to flooding incidents that and acting on this infomation you, the client or any third party, are accepting that no Borough Boundaries Flooding Events 6-7 affected (probably) more than 40 buildings. Exact locatation of flooding is not individual is personally liable in contract, tort or breach of statutory duty (including known but were in the following streets: negligence). Project North London Strategic Flood Risk Assessment Watercourses Total 8-9 24 Nov 03 Wallace Road Resulting from 30” watermain burst This map is based upon Ordance Survey material with the permission of Ordnance 3 Feb 06 – Water main burst Upper Street Survey on behalf of the Controller of Her Majesty's Stationery Office. Crown Purpose Drawing Title Canals 0 10-12 copyright. Unauthorised reproduction infringes Crown copyright and may lead to Information prosecution or civil proceedings. Map 13: Sewer Flooding Incidents by Postcode 1 13-19 Drawn SL Chckd Apprvd Data Origin KR FP From August 1997 to August 2007 Date 25/03/08 Date 25/03/08 Date 07/04/08 2-3 20-44 Sewer Flooding data provided by Thames Water. Draft Scale (at A1 size) Issuing Office Sutton Coldfield Drawing Number Rev B 4-5 45-69 Issue 1:40,000 Telephone 0121 355 8949 722586/013