Bromley by Bow South Flood Risk Assessment and Preliminary

Bromley by Bow South

Flood Risk Assessment and Preliminary Drainage Strategy

April 2016 0

CONTENTS

01 Introduction 3

02 Legislative and Planning Policy Context 6

03 Risk of Flooding – to Development 13

04 Risk of Flooding – from Development 21

05 Flood Risk Mitigation Measures 24

06 Conclusions and Recommendations 28

07 References 31

Appendix A – Environment Agency Product 4 Data & Mapping

Appendix B – Flood Risk Constraints Map

Appendix C – Preliminary Drainage Strategy

This document has been prepared by AECOM Limited for the sole use of our client (the “Client”) and in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM Limited and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM Limited.

INTRODUCTION

2 01 INTRODUCTION

Introduction

1.1 AECOM Infrastructure and Environment UK Ltd (AECOM) have been instructed by Danescroft Land Ltd, on behalf of the group of landowners (Danescroft Land Ltd, Lindhill Properties Ltd, British Land PLC, Vastint Holding B.V, Southern Housing Group, LLDC), to undertake a flood risk assessment (FRA) and drainage strategy in relation to the redevelopment of the Bromley by Bow (South) site (herein referred to as ‘the Site’), allocated as Sub Area 4.1 of the London Legacy Development Corporation (LLDC) Local Plan 2015 to 2031 ( Error! Reference source not found. ).

1.2 It is the intention of the landowners to submit an illustrative masterplan to the Planning and Policy Decisions Team (PPDT) of the LLDC. This illustrative masterplan has been subject to environmental testing, and this report forms part of a series of Environmental Impact Topic Reports which have been produced to form a separate evidence base identifying any potential significant environmental effects of the operation of the maximum extents/parameters of the illustrative masterplan, and where further work might be required to support a planning application for development of the Site, or any part thereof. 1.3 Both the illustrative masterplan and Environmental Impact Topic Reports (including this FRA and drainage strategy report) will provide the basis upon which a series of redevelopment parameters and design guidelines will be developed for the Site. These parameters and guidelines will be adopted as a Supplementary Planning Document (SPD) for the Site. Both the illustrative masterplan and Environmental Impact Topic Reports will be appended to the SPD. 1.4 The Site is approximately 6ha in size and lies between the A12 to the west, the River Lea to the east and the railway line to the south. The Bow River Village (Bromley by Bow North) development borders the Site to the north. The illustrative masterplan consists of the construction of residential, retail, workspace, education and community buildings. The Site is located with the London Borough of Tower Hamlets (LBTH) and falls under the planning jurisdiction of the LLDC. 1.5 This FRA has been prepared in accordance with the National Planning Policy Framework (NPPF) (Ref. 2) and associated Planning Practice Guidance (Ref. 3). Planning History

1.6 Two planning permissions have previously been granted which cover the Site in part or whole and are summarised below. Where relevant, reference is made in this report to the information within these two planning applications:

• Hybrid planning permission (with some elements approved in detail) was granted for the Tesco application PA/09/02574 by the GLA in July 2010 for a mixed-use development, including a District Centre and a superstore. The area covered by the Tesco application sits entirely within the Site.

• Hybrid planning permission (with detailed planning permission for Phase 1) was granted for the Bromley by Bow (North) planning application PA/11/02423 by the GLA in July 2012 for a residential led mixed-use development. The Bromley by Bow (North) site comprises the area directly to the north of the Site, and includes the northern most portion of the Site. Flood Risk Assessment Methodology

1.7 To assess the risk of all forms of flooding to and from the illustrative masterplan within this FRA, the Source-Pathway-Receptor model has been adopted.

1.8 The Source-Pathway-Receptor model firstly identifies the causes or ‘sources’ of flooding to and from a development. The identification is based on a review of local conditions and consideration of effects of climate change. The nature and likely extent of flooding arising from any one source is considered, e.g. whether such flooding is likely to be localised or widespread.

1.9 The presence of a flood source does not always infer a risk. It is the exposure pathway or the ‘flooding mechanism’ that determines the risk to the receptor and the effective consequence of

exposure. For example, sewer flooding does not necessarily increase the risk of flooding unless the sewer is local to the site and ground levels encourage surcharged water to accumulate at the site.

1.10 The varying effect of flooding on the ‘receptors’ depends largely on the sensitivity of the receptor. Receptors include people and their properties, businesses and infrastructure, and the built and natural environment within the range of the flood source, which are connected to the source of flooding by a pathway.

1.11 In order for there to be a flood risk, all the elements of the model (a flood source, a pathway and a receptor) must be present. Furthermore, effective mitigation can be provided by removing one element of the model, for example by removing the pathway or receptor.

Source Pathway Receptor

1.12 Using the outputs of the Source-Pathway-Receptor model, a risk based approach has been adopted for all flood sources that have a pathway to the receptor within this FRA. The level of risk is then defined as:

The magnitude of consequence The likelihood of a flood event of a flood event X occurring

Aims and Objectives

1.13 The aim of this report is to provide a FRA Report to assess the flood risk to and from the illustrative masterplan. In order to achieve this, the following objectives have been set:

• Consider the risk of flooding arising from the illustrative masterplan in addition to the risk of flooding to the development;

• Identify and quantify the vulnerability of the illustrative masterplan to flooding from all sources, and where appropriate identify potential flood risk reduction measures;

• Where appropriate assess the remaining ‘residual’ risk after risk reduction measures have been taken into account and demonstrate that this is acceptable for the illustrative masterplan;

• Consider the vulnerability of those that could occupy and use the illustrative masterplan, taking account of the vulnerability classification, including arrangements for safe access;

• Consider how the ability of water to soak into the ground may change with development, along with how the illustrative layout may affect drainage systems. Consultation

1.14 In order to inform the preparation of this FRA, data was obtained from the Environment Agency regarding outputs from the River Lea Modelling Study (CH2MHill for the Environment Agency, 2014) as well as details of the local flood defences. In addition, members of the AECOM team attended a meeting with representatives from the Environment Agency’s planning liaison team on Monday 4 th April and flood risk teams to discuss the flood risk constraints at the Site and requirements for future development.

1.15 In addition, AECOM submitted a Scoping Opinion request to the LLDC PPDT setting out the proposed approach, methodology and scope of the Environmental Impact Topic Reports, including the FRA and drainage strategy, on the 10 th March 2016. The LLDC PPDT did not request any changes to the approach set out in the Scoping Opinion Request.

LEGISLATIVE AND PLANNING POLICY CONTEXT

5 02 LEGISLATIVE AND PLANNING POLICY CONTEXT

Introduction

2.1 This section provides a review of the legislative and planning policy context in relation to flood risk. National Planning Policy National Planning Policy Framework (NPPF) (2012)

2.2 Section 10 of the National Planning Policy Framework (NPPF) (Ref. 1) and the associated Planning Practice Guidance: Flood Risk and Coastal Change (Ref. 3) detail current policy with respect to flood risk. 2.3 Paragraph 103 (footnote 20) of the NPPF states that ‘ a site-specific flood risk assessment is required for proposals of 1 hectare or greater in Flood Zone 1; all proposals for new development (including minor development and change of use) in Flood Zones 2 and 3, or in an area within Flood Zone 1 which has critical drainage problems (as notified to the local planning authority by the Environment Agency); and where proposed development or a change of use to a more vulnerable class may be subject to other sources of flooding ’.

2.4 The Site is approximately 6 hectares and is located within Flood Zones 1 and 2. (Further information on the definition of the flood zones across the Site is presented in Section 3). In order to enable appropriate assessment of the flood risk issues throughout the masterplan process, a site specific FRA has been prepared.

2.5 Paragraph 103 of the NPPF states that when determining planning applications, local planning authorities should ensure flood risk is not increased elsewhere and only consider development appropriate in areas at risk of flooding where, informed by a site-specific flood risk assessment following the Sequential Test, and if required the Exception Test, it can be demonstrated that:

• Within the Site, the most vulnerable development is located in areas of lowest flood risk unless there are overriding reasons to prefer a different location; and

• Development is appropriately flood resilient and resistant, including safe access and escape routes where required, and that any residual risk can be safely managed, including by emergency planning; and it gives priority to the use of sustainable drainage systems. Development Vulnerability Classification

2.6 The NPPF considers the vulnerability of different types of development to flooding. The vulnerability classifications are detailed in Table 2 of the Planning Practice Guidance for Flood Risk and Climate Change, which accompanies the NPPF.

2.7 The vulnerability classifications for the development uses within the proposed masterplan are as follows:

• Residential development – More Vulnerable

• Retail – Less Vulnerable

• Employment – Less Vulnerable

• School – More Vulnerable

• Public open space – Water Compatible 2.8 Table 3 of the Planning Practice Guidance for the NPPF illustrates a matrix which identifies the vulnerability classifications which are appropriate within each flood zone (reproduced in Table 2.1).

Table 2.1 PPG (Table 3) Flood risk vulnerability and flood zone ‘compatibility’

Flood Risk Essential Water Highly More Less Vulnerability Infrastructure Compatible Vulnerable Vulnerable Vulnerable Classification 1 2 Exception Test required 3a Exception Test Exception Test required required 3b Exception Test

Flood Zone required

2.9 The matrix identifies that all the types of development within the illustrative masterplan are appropriate within Flood Zones 1 and 2. Sequential Test

2.10 The Sequential Test is a decision making process set out in the NPPF, whereby local planning authorities must ensure that development is steered towards sites at lower risk of flooding, prior to the consideration of sites at greater risk of flooding. 2.11 Following the preparation of their Level 1 SFRA in 2008 (Ref. 4), the LBTH undertook the Sequential Test on their proposed sites in 2009 (Ref. 5). The Level 1 SFRA used the available flood risk mapping at the time and as a result the Bromley by Bow area was identified as containing Flood Zone 3, high probability of flooding, in which ‘all development requires the Sequential Test and in most cases the Exception Test’. 2.12 In 2012, an increased scope Level 2 SFRA (Ref. 6) was prepared for LBTH providing a detailed assessment of their proposed allocation sites, including the Bromley by Bow site. The Level 2 SFRA also stated that ‘within the Flood Zone 3 areas of the site, More Vulnerable uses are permitted however will be subject to the Sequential and Exception Tests’. 2.13 In July 2015, the LLDC Local Plan was adopted ( Error! Reference source not found. ). A number of sub-areas are identified including sub area 4: Bromley-by-Bow, Pudding Mill, Sugar House Lane and Mill Meads. The Site is shown to be included within this sub-area which has been identified and justified for future development.

2.14 In addition, since the preparation of the Level 1 and 2 SFRAs, the flood risk mapping has been revised for the area, and the probability of flooding on the Site is now less than 1 in 1,000 year annual probability; i.e. the Site is located in Flood Zone 1 with respect to the modelled probability of flooding (further detail regarding the definition of flood zones on the Site is provided in Section 3).

2.15 As a result of the Flood Zone definition on the Site, and the allocation in the LLDC Local Plan, the Site is considered to be located in an area with low risk of flooding, and to have passed the Sequential Test. The illustrative masterplan comprises More Vulnerable and Less Vulnerable elements, both of which area appropriate in Flood Zone 1 (and Flood Zone 2), and do not require application of the Exception Test. Sequential Approach

2.16 The NPPF advocates a sequential approach to development, whereby areas at lowest risk of flooding are developed in preference to those areas where the risk is greater. On the Site, this requires the setting back of development from the edge of the River Lea and the early consideration of surface water flow paths across the Site, to ensure that development is steered towards those areas at lowest risk of flooding. Surface Water Management

2.17 Sustainable Drainage Systems (SuDS) are an approach to managing rainwater and surface water that replicates natural drainage, the key objectives being to manage the flow rate and volume of runoff at source, in order to reduce risk of flooding and to improve water quality. From 6th April 2015, the

Planning Practice Guidance for Flood Risk and Coastal Change (PPG) was amended to provide a stronger emphasis on the implementation of SuDS. LPAs (such as LBTH) are required to ensure that SuDS are incorporated in all major development plans where appropriate, and through the use of planning conditions or planning obligations, make sure that there are clear arrangements in place for ongoing maintenance over the lifetime of the development. Flood and Water Management Act

2.18 The Flood and Water Management Act 2010 (Ref. 7) introduces requirements for managing 'local' sources of flood risk such as flooding from surface water, groundwater and ordinary watercourses, through introducing a number of duties and powers for Lead Local Flood Authorities (LLFAs), in this case LBTH. 2.19 The Act also prioritises requirements for Sustainable Drainage Systems (SuDS) through the planning system, as described in 2.11. Lead Local Flood Authorities (LLFAs), as defined by the Flood and Water Management Act, are statutory consultees for surface water drainage. As the LLFA, LBTH will need to be consulted on the drainage elements of planning applications for major development to ensure they take account of the Government’s ‘Sustainable Drainage Systems: Non-Statutory Technical Guidance’ (Ref. 8). Regional Planning Policy The London Plan: The Spatial Development Strategy for London – Consolidated with Alterations since 2011 (March 2015)

2.20 The London Plan (Ref. 9) is the overall strategic plan for London that sets out an integrated economic, environmental, transport and social framework for developments in London for the next 20 – 25 years. The following policies relate to flood risk and are relevant to the proposed development: Policy 5.12 – Flood Risk Management

2.21 Policy requirements largely reflect those stated above in the NPPF; however specifically, developments in London will also need to address flood resilient design and emergency planning by demonstrating that:

• the development will remain safe and operational under flood conditions;

• a strategy of either safe evacuation and/or safe refuge is followed under flood conditions;

• key services including electricity, water etc. will continue to be provided under flood conditions; and

• buildings are designed for quick recovery following a flood. Policy 5.13 – Sustainable Drainage

2.22 Development should utilise SuDS unless there are practical reasons for not doing so, and should ensure that surface water run-off is managed as close to its source as possible. Developments should aim to achieve greenfield runoff rates where possible. Sustainable Design and Construction Supplementary Planning Guidance (2014)

2.23 The Sustainable Design and Construction Supplementary Planning Guidance (SPG) (Ref. 10), provides guidance on the implementation of London Plan policy 5.3 - Sustainable Design and Construction, as well as a range of policies relating to environmental sustainability. It is a key supporting document for the management of flood risk in London and the implementation of SuDS.

2.24 To support the flood related policies in the London Plan, the SPG includes guidance on:

• Surface water flooding and sustainable drainage, including Surface Water Management Plans (SWMP), Greenfield runoff rates, the multifunctional benefits of SuDS, management of SuDS and contributions;

• Flood resilience and resistance of buildings in flood risk areas;

• Flood risk management, including the design life of development, safety, and basements; 8

• Flood defences; and

• Other sources of flooding, including groundwater flooding, reservoir flooding and surface water flooding.

2.25 With regards to Greenfield runoff rates, the SPG states the following preferred standards: “all developments on greenfield sites must maintain greenfield runoff rates. On previously developed sites, runoff rates should not be more than three times the calculated greenfield rate. The only exceptions to this, where greater discharge rates may be acceptable, are where a pumped discharge would be required to meet the standards or where surface water drainage is to tidal waters and therefore would be able to discharge at unrestricted rates provided unacceptable scour would not result”.

2.26 However, if it is not practical to achieve greenfield runoff rates, the essential standards for runoff requires a minimum of 50% attenuation of the site’s (prior to re-development) surface water runoff at peak times. Developers are required to demonstrate and justify why greenfield runoff rate cannot be achieved, and identify which methods/opportunities have been used to minimise final site runoff, as close to greenfield rate as practical. This should be done using calculations and drawings appropriate to the scale of the application. Thames Estuary 2100 Plan (TE2100)

2.27 The TE2100 Plan (Ref. 11) is the result of a detailed assessment of the options available to manage flood risk and their economic costs, benefits and environmental impacts for the Thames estuary up to 2100. It sets out the strategic direction for managing flooding across the estuary, and contains recommendations on what actions the Environment Agency and others will need to take in the short (next 25 years), medium (the following 15 years) and long term (to the end of the century). It also identifies sites where intertidal habitat (saltmarsh and mudflat) could be created to replace habitats that are being lost due to rising sea levels.

2.28 The Plan is based on current guidance on climate change, but is adaptable to changes in predictions for sea level rise and climate change. 2.29 The Environment Agency is currently preparing a supporting implementation plan to look at the most cost-effective way to implement the recommendations in the TE2100 Plan, starting with the first 10 years. Local Planning Policy LLDC Local Plan 2015 to 2031

2.30 The London Legacy Development Corporation (LLDC) is the local planning authority for the area surrounding the Queen Elizabeth Olympic Park. The Local Plan was adopted by the LLDC in July 2015 ( Error! Reference source not found. ).

2.31 The Site is located within sub area 4: Bromley-by-Bow, Pudding Mill, Sugar House Lane and Mill Meads. One of the priorities for this sub area is ‘ to take advantage of the character and history of the waterways to bring forward new development ’.

2.32 The LLDC Local Plan sets out some policies related to the water environment over and above those set at a national and regional level, with a particularly detailed policy of flood risk and sustainable drainage. The key points of relevant policy are detailed below. 2.33 Policy S.4 Sustainable design and Construction – applications for major developments will be required to include evidence within their Design and Access statement that they have taken into account resource efficiency, living roofs and sustainable drainage systems. Residential development must demonstrate they are capable of achieving at least Code for Sustainable homes Level 4 (or any future national recognised equivalent). 2.34 Policy S.5 Water supply and waste water disposal states the following:

• LLDC encourage localised and building specific measures to reduce potable water demand and use, including greywater recycling systems, rainwater harvesting and measures to reduce domestic water use to 105 litres per person per day or less.

• Proposals for major development are expected to demonstrate that they maximise opportunities to reduce water demand and use. Where feasible for domestic use it should be demonstrated measures are capable of achieving water use of less than 105 litres per person per day.

• Proposals must demonstrate that there is sufficient existing or planned water supply and waste water disposal infrastructure capacity to meet the demands of the development. Where capacity cannot be demonstrated, the scheme must include capacity improvements to meet its needs. 2.35 Policy S.8 Flood risk and sustainable drainage systems states the following:

• A site specific flood risk assessment may be required within Local Flood Risk Zones identified in Surface Water Management Plans to ensure that the development will remain safe and will not increase flood risk to others. Where deemed necessary, the development proposals must be supported by a detailed integrated hydraulic modelling within the Flood Risk Assessment.

• Development proposals must be designed to reduce vulnerability to climate change, apply the sequential approach on site, be flood resilient and resistant, setting living accommodation above the predicted flood level, and must provide an appropriate means of escape to a higher level within the building or a safe route to a location above the predicted flood level.

• No basement development will be permitted within Flood Zones 2 or 3.

• Development proposals that create an obstruction within a watercourse or obstruct existing flood flow paths across land which cannot be mitigated through compensatory works or provision of additional flood storage capacity will not be permitted.

• The design and layout of Proposed Development should incorporate appropriate buffer strips adjacent to watercourses to allow access for flood risk maintenance and biodiversity and adequate space for sustainable drainage techniques.

• Where an existing flood defence structure exists, development proposals should be designed to maintain the integrity of the existing structure. Where the need for new or improved flood defences have been identified, relevant planning applications should demonstrate that allowance has been made for the relevant works to take place, including sufficient access for construction. Where a development proposal is dependent on the provision, improvement or repair of a river wall or other flood defence structure, these works should be included within the development applied for within the planning application.

• The rate of surface water run-off from development Sites should be restricted to no greater than the equivalent for a Green Field Site of an equivalent size using sustainable drainage techniques as a first choice and only using other methods of flow restriction where it can be shown that sustainable drainage methods are not feasible in that location, particularly in areas where a localised surface water drainage problem has been identified within a Surface Water Management Plan.

• Sustainable drainage systems that have benefits for water quality and storage, habitat and landscapes should be fully considered before other options. All drainage systems discharging to a watercourse must include appropriate anti-pollution measures that can be easily accessed and maintained. 2.36 Policy BN.13: Improving the quality of land – requires that, to prevent harm to health and the environment from the effect of contamination and the release of pollutants and to bring contaminated land into beneficial use, development proposals will be required to ensure drainage methods are suitable for the site conditions and protect groundwater. Other Relevant Policy, Standards and Guidance London Borough of Tower Hamlets Level 2 Strategic Flood Risk Assessment (2012)

2.37 The LBTH Level 2 Strategic Flood Risk Assessment (SFRA) (Ref. 6) was prepared in 2012 to assist LBTH in spatial planning decisions that are required to inform the Local Plan. Existing information and additional modelling was undertaken to identify the level of flood risk posed in the borough. The SFRA reported that eastern parts of the borough within the Lower Lea Valley may be affected by fluvial flooding on the lower reaches of the River Lea. There is also a residual tidal flood risk in the event of a

breach in the flood defences along the River Thames, however there is limited historical information on surface water, sewer flooding and groundwater flooding in LBTH. London Borough of Tower Hamlets Surface Water Management Plan (2011)

2.38 As part of the Drain London Project, a Surface Water Management Plan was prepared for LBTH (Ref. 12). A Surface Water Management Plan (SWMP) is a framework to understand the causes of surface water flooding and agree the most cost effective way of managing surface water flood risk. The main outputs are a co-ordinated Action Plan to prioritise projects to reduce surface water flood risk and detailed mapping of areas prone to surface water flood risk.

2.39 The flood risk mapping and records of historical flooding presented within the SWMP have been used to inform this FRA. London Borough of Tower Hamlets Local Flood Risk Management Strategy (2014)

2.40 As a LLFA, LBTH has a statutory duty to develop, maintain, apply and monitor a strategy for local flood risk management in their administrative area. A Draft Local Flood Risk Management Strategy (LFRMS) was prepared in 2014 (Ref. 13) and is designed to provide guidance and information for residents, businesses and developers regarding Tower Hamlets strategy for dealing with flooding within the borough. This document has been referred to during the preparation of the FRA. London Borough of Tower Hamlets SuDS Guidance

2.41 In response to Schedule 3 of the FWMA and the increasing use of SuDS by Tower Hamlets Council and developers, the Tower Hamlets SuDS Guidance has been produced (Ref. 14). http://www.towerhamlets.gov.uk/lgnl/environment_and_planning/flood_risk_management.aspx 2.42 The document was created in-house with technical expertise sought from Sustainability Centre at The University of East London. The guidance not only provides the legislative background on Flood management but also outlines six key SuDS features that are highly applicable for use within the borough; these are green roofs and small scale green roofs, engineered tree pits, rain gardens, swales, attenuating planters and permeable/porous paving. In addition the guidance also has information on calculating the water storage capacity of SuDS.

RISK OF FLOODING – TO THE SITE

12 03

RISK OF FLOODING – TO THE SITE

Introduction

3.1 The NPPF requires that all potential sources of flooding that could affect a proposed development are considered as part of a FRA. As set out in paragraph 2 of the Planning Policy Guidance (Ref. 3), this includes flooding from rivers and the sea, directly from rainfall on the ground surface and rising groundwater, overwhelmed sewers and drainage systems, and from reservoirs, canals, lakes and other artificial sources.

3.2 This Section considers the risk from each of these potential sources in turn. Tidal and Fluvial Flooding

3.3 The Lower Lea Navigation flows in a southerly direction, adjacent to the eastern boundary of the Site, to join the River Thames approximately 2.5km south east of the Site at Leamouth. The watercourse is defined as a 'Main River' by the Environment Agency. There are a number of other watercourses near to the Site with which the River Lea interacts, however the main fluvial flood risk is still considered to be solely from the River Lea Navigation. Flood Zones

3.4 The Flood Map for Planning (Rivers and Sea), available on the Environment Agency website, identifies the Site to be located in Flood Zone 1 and 2 associated with the River Lea Navigation. The definitions of Flood Zones are based on the probability of flooding from rivers and the sea, ignoring the presence of defences, and are set out in Table 1 of the Planning Practice Guidance, which has been reproduced in Table 3.1.

Table 3.1 Flood Zone Definitions (extracted from PPG, 2014)

Flood Zone Definition Probability of Flooding

Land having a less than 1 in 1,000 annual probability of river or sea flooding. Flood Zone 1 Low (Shown as ‘clear’ on the Flood Map – all land outside Zones 2 and 3). Land having between a 1 in 100 and 1 in 1,000 annual probability of river flooding; or Flood Zone 2 Land having between a 1 in 200 and 1 in 1,000 annual probability of sea flooding. Medium (Land shown in light blue on the Flood Map) Land having a 1 in 100 or greater annual probability of river flooding; or Flood Zone 3a Land having a 1 in 200 or greater annual probability of sea flooding. High (Land shown in dark blue on the Flood Map) This zone comprises land where water has to flow or be stored in times of flood. Flood Zone 3b Defined by the LPA within a SFRA. Functional Floodplain (Not separately distinguished from Zone 3a on the Flood Map).

3.5 It is noted that as well as using the probability of flooding based on the outputs from modelling studies as described in Table 3.1, the delineation of Flood Zone 2 also typically includes the extents of historic flood events that have been verified by the Environment Agency and are included on the Environment Agency Historic Flood Map.

3.6 The figures included in Appendix A show the Flood Map for Planning and the Historic Flood Map for the Site provided by the Environment Agency. These figures identify that across the Site, the extent of Flood Zone 2 is derived from a historic flood event that occurred during 1947, rather than the extent of flooding during the 1 in 1,000 annual probability flood event based on the River Lea Modelling Study (Ref. 15).

3.7 The 1947 flood event was caused by significant snowmelt and extreme rainfall, prior to installation of the present flood defences along the Lower Lea Valley. Following this event, construction of the Lea Flood Relief Channel was commissioned and became operational in 1976.

Modelled Flood Levels

3.8 The outputs from the River Lea Modelling Study show that flows remain in bank in the vicinity of the Site for all modelled return periods. The modelled flood levels for four of the model nodes adjacent to the Site boundary are shown in Table 3.2. The location of the nodes that have been referenced is shown in the figures in Appendix A. 3.9 It is noted that the modelled return periods refer to the probability of fluvial flood events in the River Lea; however this part of the watercourse is also impacted by water levels in the River Thames. To account for this, the downstream boundary of the hydraulic model has been determined using the maximum water level that would be permitted within the River Thames in accordance with the Thames Barrier closure matrix.

Table 3.2 River Lea Modelling Study 1D Modelled Flood Levels for Defended scenarios

Return Period Node Label Easting Northing 20yr 100yr 100yr + 20% 1000yr

R9A-1103 538322.4 182650.9 3.869 4.951 4.990 5.010 R9A-1187 538295.1 182734.6 3.868 4.944 4.972 4.994 R9A-1281d 538254.6 182791.8 3.867 4.941 4.967 4.984 R9A-1366 538199.0 182863.2 3.867 4.953 4.990 5.018 R9A-1441c 538175.0 182884.2 3.867 4.956 4.997 5.026

Impacts of Climate Change

3.10 The River Lea Modelling Study includes an assessment of the impact of climate change by applying a 20% increase in river flows on the 1 in 100 year annual probability event, in accordance with the guidance on climate change at the time the modelling was completed. The outputs show that the water remains in-bank, and the Site does not flood during this scenario. 3.11 In February 2016, the Environment Agency issued revised guidance on climate change allowances (Ref. 16) for peak river flow by river basin district. The allowances for the Thames river basin district are set out in Table 3.3.

Table 3.3 Peak river flow allowances for Thames river basin district (use 1961 to 1990 baseline)

River Total potential change Total potential change Allowance Total potential change anticipated basin anticipated for ‘2020s’ anticipated for ‘2050s’ category for ‘2080s’ (2070 to 2115) district (2015 to 2039) (2040 to 2069)

Upper end 25% 35% 70% Thames Higher central 15% 25% 35% Central 10% 15% 25%

3.12 For sites within Flood Zone 2 the following allowances should be considered:

• For More Vulnerable development, use the central and higher central to assess a range of allowances.

• For Less Vulnerable development, use the central allowance. 3.13 The allowances to be applied therefore range from 10% - 35%, depending on the lifetime and vulnerability classification of the proposed development.

3.14 Given that the Site is not modelled to flood during the 1 in 100 year plus a 20% climate change allowance or a 1 in 1000 year event, the risk of flooding taking into account climate change at 10-35% is considered to be low.

Flood Defences

3.15 The Environment Agency maintains an Asset Information Management System (AIMS) which provides details of flood defences and other assets. The defences adjacent to the Site are described as ‘concrete walls and sheet steel piling up to Thames Mill Lane’ and are reported to have a condition rating of 2 (where 1 is Good, and 5 is Poor). Further details are provided in Table 3.4. The extent of the defence described is shown in the figure in Appendix A.

Table 3.4 Defences adjacent to the Site (details from Environment Agency AIMS)

Design Condition of Asset Standard of Downstream Upstream Defences Asset ID Asset Type Asset Comment Protection protection Crest Level Crest Level (1=Good, (years) 5=Poor)

134371 defence fluvial Lined channel side 50 5.71 6.75 2

3.16 Table 3.3 from the Environment Agency AIMS shows that the crest levels of the flood defences are recorded to be between 5.71 and 6.75mAOD.

3.17 In this location, the statutory defence levels are:

• 5.49mAOD for the present day;

• 5.70mAOD for the year 2065; and

• 6.2mAOD for the year 2100.

3.18 At this location along the River Lea Navigation, water levels are also influenced by the tidal water levels in the River Thames, and the Site is therefore benefitting from the presence of the Thames Barrier to manage water levels in the River Thames. Summary

3.19 Based on the available datasets, the risk of flooding from tidal and fluvial sources to the Site is considered to be low. The Site is not shown to be at risk during the 1 in 1000 year annual probability flood event and is therefore designated Flood Zone 1. The definition of Flood Zone 2 across the eastern part of the Site is due to a historic flood event in 1947, prior to the development of the flood defence system along the Lower Lea Valley and not the current probability of flooding.

3.20 The risk to the Site is therefore residual, in the event of a breach in the local flood defences. 3.21 The future risk to the Site, accounting for the impacts of climate change, will depend on the maintenance of the local flood defences, and their raising in accordance with the statutory levels. Surface Water Flooding

3.22 Surface water flooding is the term used to describe flooding which occurs when intense, often short duration rainfall is unable to soak into the ground or to enter drainage systems and therefore runs over the land surface causing flooding. It is most likely to occur when soils are saturated so that they cannot infiltrate any additional water or in urban areas where buildings tarmac and concrete prevent water soaking into the ground. The excess water can pond (collect) in low points and result in the development of flow pathways often along roads but also through built up areas and open spaces. This type of flooding is usually short lived and associated with heavy downpours of rain. Ground Surface

3.23 The ground surfaces of the Site at present are almost entirely impermeable, as a result of the industrial units, supermarket, tarmac and hard standing surrounding buildings. 3.24 Ground levels across the development site generally slope in a south-easterly direction, falling towards the River Lea Navigation. Topographic survey identifies that the ground surface of the Site lies between approximately 5.0m AOD and 10.1m AOD.

Historic Records

3.25 There are no historic records of surface water flooding in this area. It is considered that the Site is not at risk from surface water. However it is difficult to assess in detail the effect of surface water during extreme events. Surface water sewers are at risk of surcharging during extreme rainfall events with flooding occurring principally from manholes and gullies. Surcharging sewers can result in overland flow which if originating at a higher elevation than a development site can potentially pose a flood risk. Updated Flood Map for Surface Water

3.26 The Environment Agency has undertaken modelling of surface water flood risk at a national scale and produced mapping identifying those areas at risk of surface water flooding during three annual probability events: 1 in 30 year (3.33% annual probability), 1 in 100 year (1% annual probability) and 1 in 1000 year (0.1% annual probability). The latest version of the mapping is referred to as the ‘updated Flood Map for Surface Water’ (uFMfSW) and is available on the Environment Agency website, where it is referred to as ‘Risk of Flooding from Surface Water’.

3.27 The uFMfSW mapping shows that roadways within the existing site layout, and the area adjacent to the River Lea, are shown to be susceptible to surface water ponding. 3.28 The LBTH SWMP (Ref. 12) shows that the Site is not located within a Critical Drainage Area (CDA). Surface water modelling completed as part of the SWMP identifies that part of the Site, adjacent to the River Lea Navigation, is shown to have Moderate hazard rating during the 1 in 100 year annual probability modelled rainfall event. Surface Water Management

3.29 The existing Site has an area of approximately 6 hectares and is estimated to be approximately 95% impermeable. Examination of topographic and services surveys for the Site show that these areas are currently drained via a traditional piped drainage system, which appears to discharge to the existing combined sewer at unrestricted rates. Four individual discharge locations have been identified, which serve the entire site area. The full-bore capacities of the existing outfalls have been assessed and are tabulated in Table 3.5. These capacities assume that the outfall will not be surcharged.

Table 3.5 Hydraulic Capacity of Existing Outfalls

Outfall Number Diameter and Approximate Gradient Capacity (Full Bore Flow) 150mm 17.6 litres /second 1 1 in 77 (assumed) 225mm 2 40.7 litres /second 1 in 125 (assumed) 300mm 3 72.5 litres /second 1 in 182 (assumed) 300mm 4 72.5 litres /second 1 in 182 (assumed) Total 203.3 litres per second

3.30 To assess the adequacy of the existing drainage network, statistical rainfall profiles for the Site have been established utilising computer software based upon "Design and Analysis of Urban Storm Drainage - The Wallingford Procedure”, with the following variables established from figures A1 and A2 from the Wallingford Procedure for the Site location:

M5-60 = 20.6mm, Ratio, R = 0.438 Average rainfall intensity figures have been calculated using the MicroDrainage computer software package to establish rates of runoff generated from the 85% impermeable area of the existing site. Results for 1 in 1 year, 1 in 2 year, 1 in 5 year, 1 in 30 year and 1 in 100 year rainfall events are tabulated in Table 3.6. It should be noted that runoff rates are calculated using the average rainfall intensity for the storm duration under consideration. Although peak rainfall rates are significantly higher during each storm they have a very short duration; therefore average runoff rates used to assess the adequacy of the outfalls represent a conservative assessment.

Table 3.6 Average Rainfall Intensities by Return Period

Return Period Average Rainfall Intensity Average Runoff Generated within the Site 60 minute storm 4 hour storm 60 minute storm 4 hour storm (mm/hr) (mm/hr) (l/sec) (l/sec) 1 in 1 year 13.2 4.9 202.7 80.8 1 in 2 year 16.7 5.9 256.5 98.2 1 in 5 year 21.1 7.4 340.4 118.8 1 in 30 year 31.7 10.9 513.0 177.3 1 in 100 year 41.7 14.3 674.5 229.6

3.31 Within Table 3.6 the calculated runoff rates from the Site have been colour coded as follows:

• The rates highlighted in orange represent those which exceed the combined capacity of the outfalls (estimated at 203.3 litres per second under full bore conditions),

• The rates highlighted in green represent those within the combined capacity of the outfalls.

3.32 It can be seen that runoff generated from the existing site is generally far in excess of the capacity of the existing outfalls under full bore conditions. It is therefore considered likely that these pipes are surcharged during higher return period storms, which may also give rise to uncontrolled flooding on the Site.

3.33 No attenuation devices have been identified on the Site, hence water will back up in the pipework and manholes and flood onto the surface once the capacity of the surface water drainage system has been exceeded. When this occurs, flood water will pond or flow overland to exit the Site in an uncontrolled manner via the low points on the Site boundary. It is apparent the storms of a shorter duration and greater average intensity are more critical to flooding than longer storms of lesser average intensity.

3.34 Based upon the above calculations, it can be concluded that the Site is currently susceptible to flooding from surface water runoff generated within the Site, with uncontrolled ponding and overland flow of flood water likely to occur on a regular basis. Summary

3.35 Given the highly impermeable nature of the existing Site the risk of surface water flooding is considered to be medium prior to mitigation. A drainage strategy is provided within Section 5 which identifies methods of enabling existing surface water to be managed more effectively within the Site in order to enable the risk of surface water flooding to be reduced. Sewer Flooding

3.36 Flooding from foul and combined sewers occurs when rainfall exceeds the capacity of networks or when there is an infrastructure failure. In the LBTH the sewer network is a largely combined foul and surface water system. Sewer Infrastructure on Site

3.37 There are three trunk sewers (ranging from 2.3m to 3.1m diameter) running across the Site from south-west to north-east at a depth to crown over 9m below ground level. The line, level, construction and condition of these sewers have not been confirmed by survey. 3.38 There are other existing combined public sewers (ranging from 150mm to 375mm diameter) within the Site boundary serving the existing development on-site and public roads as well as external areas.

3.39 Sewer systems are generally designed for storm events up to a return period of 3.3% (1 in 30 years) and there is therefore potential for the capacity of the existing network to be exceeded during extreme rainfall events. No attenuation devices have been identified within the existing Site and there is therefore potential for surface water to back up in the pipework and manholes, and flood onto the surface once the capacity of the existing network is exceeded. When this occurs, flood water will pond or flow overland to exit the Site in an uncontrolled manner via the low points on the Site boundary.

Historic Records

3.40 During the preparation of the SWMP (Ref. 12) no historical records of sewer flooding were available from the LBTH or Thames Water. This is not to say that no such incidents have occurred or that there is no future flood risk to the Site from sewer flooding. Summary

3.41 Given the highly impermeable nature of the existing Site and the existing sewer infrastructure, the current risk of flooding as a result of the local sewer system being overwhelmed is considered to be medium prior to mitigation. Groundwater Flooding Ground Conditions

3.42 Based on the intrusive site investigations undertaken as part of the 2010 planning application (Ref: PA/09/02574), the ground conditions on the Site were found to comprise between 1.1-5.5m in thickness of Made Ground overlying, in turn Alluvium, River Terrace Gravel and London Clay. The London Clay is present at between approximately 3-4.5m below ground level (bgl). Lambeth Group strata are present beneath the London Clay. The Thanet Sand Formation and the Upper Chalk are present at depth in this location (Ref. 17). Increased Potential for Elevated Groundwater

3.43 As part of the SWMP, a dataset was developed referred to as the Increased Potential Elevated Groundwater (iPEG) mapping. The iPEG mapping assists in identifying areas which have an increased potential to experience groundwater flooding. The iPEG map shows those areas within the borough where there is an increased potential for groundwater to rise sufficiently to interact with the ground surface or be within 2m of the ground surface. The assessment was carried out at a Greater London scale.

3.44 The mapping identifies that the Site is not within an area of iPEG. There are also no known historic records of flooding in this area. 3.45 The risk of groundwater flooding to the Site is currently considered to be low. Canals, Reservoirs, Artificial Sources Risk from Reservoirs Mapping

3.46 In 2009, the Environment Agency commissioned inundation mapping of all reservoirs listed under the Reservoirs Act 1975. The inundation maps show the effects of a dam breach on the downstream catchment and were produced to assist Local Authorities in their responsibilities in coordinating emergency plans. The mapping is available on the Environment Agency website and shows that the eastern edge of the Site, adjacent to the River Lea channel, would be at risk in the unlikely event of a failure of one of the reservoirs listed in Table 3.7.

Table 3.7 Risk of Flooding from Reservoirs – Reservoirs shown to impact the Site

Reservoir Name Local Authority Owner National Grid Reference

King George V Enfield Thames Water Ltd 537055, 197188 William Girling Enfield Thames Water Ltd 536414, 195188 Lockwood Waltham Forest Thames Water Ltd 535346, 190696 Banbury Waltham Forest Thames Water Ltd 536244, 191728

3.47 Reservoirs in the UK have an extremely good safety record. The Environment Agency is the enforcement authority for the Reservoirs Act 1975 in England and Wales. All large reservoirs must be inspected and supervised by reservoir panel engineers. It is assumed that these reservoirs are regularly inspected and essential safety work is carried out. These reservoirs therefore present a managed risk.

Canals

3.48 The LBTH SFRA (Ref. 6) states that following discussions with British Waterways during the preparation of the SFRA it was concluded that due to the active management and regular maintenance of the structures there is a very low risk of flooding associated with nearby canals. Summary of Flood Risk to the Site

3.49 Table 3.8 provides a summary of the risk of flooding posed to the Site.

Table 3.8 Summary of Flood Risk to the Site

Flood Source Risk of Flooding Tidal Low – Medium Flood Zone 1 and 2. Section 5 River Thames provides details of measures to mitigate the risk of flooding. Fluvial Low – Medium Flood Zone 1 and 2. Section 5 River Lea Navigation provides details of measures to mitigate the risk of flooding. Groundwater Low, subject to suitable mitigation measures during Rising groundwater levels in the underlying geology. construction phase as described in Section 5. Surface Water / Overland flow Medium. Section 5 provides details of appropriate Runoff from site and surrounding land and hard mitigation. surfaces. Drainage Current risk – Low. Surrounding public / private drainage systems Future risk – Medium when considering impact of climate change prior to additional mitigation which is described in Section 5. Artificial Sources Low Add details

RISK OF FLOODING – FROM THE ILLUSTRATIVE MASTERPLAN

20 04

RISK OF FLOODING – FROM THE ILLUSTRATIVE MASTERPLAN

Introduction

4.1 The NPPF requires consideration of the wider impacts of the illustrative masterplan on flood risk as part of a FRA. This section considers the impact of the illustrative masterplan on the risk of flooding to the surrounding area, based on the potential sources listed in paragraph 2 of the Planning Policy Guidance (Ref. 3). Proposed measures to mitigate any increase in flood risk and to enable an overall reduction in flood risk on the Site are presented in Section 5. Tidal and Fluvial Flooding

4.2 The illustrative masterplan will not impact the ability of the channel to store flood water and will therefore not result in an increase in the level of tidal or fluvial flood risk posed to the Site and surrounding area. 4.3 Potential improvements to the flood defences, in accordance with the statutory flood defence levels set out in Section 5, provide an opportunity to provide a reduction in the flood risk to the Site and surrounding area in the future. Surface Water Flooding

4.4 The illustrative masterplan will enable the impermeable area within the Site to be reduced from approximately 95% to approximately 75%; therefore the illustrative masterplan will reduce the peak rate and volume of surface water discharged from the Site. However, the surface water flooding assessment that is provided within Section 3 indicates that the runoff generated within the existing Site is generally far in excess of the capacity of the existing outfalls under full bore conditions. The reduction in impermeable area generated by the illustrative masterplan is therefore unlikely to prevent uncontrolled flooding from occurring on the Site during higher return periods.

4.5 A surface water drainage strategy is set out in Section 5, which enables surface water flood risk to be reduced through the provision of a new surface water drainage network that incorporates Sustainable Drainage Systems (SuDS) to collect, attenuate and improve the quality of surface water generated by rainfall events with return periods of up to 1 in 100 years, including an additional allowance of 40% for climate change. Sewer Flooding

4.6 The illustrative masterplan indicates that new buildings will be constructed within the Site, which have potential to conflict with existing combined sewers that extend through the Site. Smaller diameter combined sewers that serve the existing buildings should generally be diverted to avoid proposed buildings to allow them to be retained to form outfalls for foul drainage networks that are extended through the Site to accommodate foul water generated by the development. However, the illustrative masterplan should ideally be developed to incorporate easements for the existing trunk sewers to enable new buildings to be positioned 6m clear of the outer edge of the existing sewer to enable flows to be maintained, as it is unlikely to be practical to divert these strategic existing sewers.

4.7 The illustrative masterplan comprises demolition of the existing commercial and industrial units and construction of a new residential led mixed use development providing approximately 1,691 residential dwellings together with additional retail and commercial units, a primary school and a Combined Heat and Power plant. The illustrative masterplan in place will cause the peak foul discharge from the Site to increase significantly. It will therefore be necessary to consider providing a cascading system of Sustainable Drainage Systems (SuDS) to enable the peak discharge from rainfall events with a return period of 1 in 100 years plus climate change to be reduced in order to create capacity within the existing combined sewers to enable the additional foul discharge from the Site to be accommodated without increasing the risk of sewer flooding.

Groundwater Flooding

4.8 The existing Site is highly developed and comprises buildings and areas of hard standing. The illustrative masterplan includes the construction of commercial, educational and residential development along with associated car parking areas. 4.9 The underlying geology in the wider area is considered to be impermeable and therefore the potential for the construction of the foundations of the proposed buildings to affect potential pathways for groundwater flows and subsequently impact the risk of groundwater flooding to the Site and surrounding area is considered to be low. Summary of Flood Risk – from the Illustrative Masterplan

4.10 The most likely way that the illustrative masterplan could result in an increased risk of flooding to both the Site and surrounding area is through insufficient consideration of surface water runoff from the Site and inadequate measures for surface water management. Measures to mitigate this risk are included in Section 5.

FLOOD RISK MITIGATION MEASURES

23 05

FLOOD RISK MITIGATION MEASURES

Introduction

5.1 This section identifies the opportunities and constraints for redevelopment of the Site, in relation to the flood risk, surface water management and drainage requirements. 5.2 Where appropriate, design guidelines which will form part of the illustrative masterplan are also summarised. Flood Risk Mitigation Measures Set-back Distance

5.3 An 8m setback zone from the edge of the flood defences must be retained as shown in Appendix B Figure 1 Flood Risk Constraints Map. This 8m zone should be kept clear of development and hard surfaces. Should a path need to be accommodated within this zone, it should be set back as far as possible from the watercourse to encourage opportunities for biodiversity. 5.4 With regard to the illustrative masterplan, this requirement may have some implications for the south eastern corner where development is currently proposed adjacent to the flood defences. This would need to be further discussed with the Environment Agency and considered during the detailed design stage associated with any future planning application for the Site, or any part thereof. Flood Defence Requirements

5.5 The Environment Agency AIMS records the crest levels of the flood defences to be between 5.71 and 6.75mAOD. The condition is recorded to be rating 2 – Good.

5.6 In this location, the statutory defence levels are:

• 5.49mAOD for the present day;

• 5.70mAOD for the year 2065; and

• 6.2mAOD for the year 2100.

5.7 The current defences already meet the statutory level for 2065. 5.8 It is assumed that the riparian owners of the land own the defences and therefore have a responsibility to maintain the defences for the lifetime of the development. This is typically considered to be 100 years for residential development. For development to be considered appropriate at the Site, it will be necessary either to raise the defences to the statutory level for the lifetime of the development, or demonstrate that it will be possible to raise the defences in the future to meet the 6.2mAOD level for the year 2100. 5.9 The Environment Agency identified that the actions associated with the Water Framework Directive (WFD) of relevance to this Site include replacing the hard defences adjacent to the Site with soft defences to encourage biodiversity. Site Layout

5.10 The eastern part of the Site is designated Flood Zone 2.

5.11 Ideally, development uses with lower vulnerability classifications, including retail, employment, public open space, should be directed towards this area.

5.12 If the school currently located in this area in the illustrative masterplan cannot be relocated, justification needs to be provided for its location. Finished Floor Levels

5.13 Finished floor levels for new development should be set at the standard level of 300mm above ground level.

Emergency Planning

5.14 The eastern part of the Site is adjacent to the River Lea Navigation. Access to the Site is provided from the western edge, and therefore there is adequate evacuation route away from the Site to areas located in Flood Zone 1. 5.15 Given the proximity to the River Lea Navigation, occupants of the Site should consider signing up to the Environment Agency Flood Warning Service. Groundwater Monitoring During Construction

5.16 As detailed in Section 4, there may be a risk of groundwater flooding during construction of new buildings. Groundwater levels should be monitored during construction to determine the risk of flooding and inform appropriate mitigation during construction. Preliminary Drainage Strategy

5.17 The Flood and Water Management Act removes the automatic right for surface water to be discharged to existing sewers and the impermeable strata underlying the Site is unlikely to be suitable for infiltration. It will therefore be necessary to provide a new surface water drainage network that extends through the Site to enable surface water to be discharged to the River Lea. This approach ensures compliance with the hierarchy defined in the London Plan and it permits the surface water catchment of the combined sewers to be reduced in order to create capacity for additional foul flows generated by the redevelopment. 5.18 The new surface water drainage network is proposed to incorporate Sustainable Drainage Systems (SuDS) to enable the peak discharge generated during rainfall events with a return period of 1 in 1 year, 1 in 30 years and 1 in 100 years plus climate change to be restricted to three times the equivalent greenfield runoff rates in order to comply with the requirements of the London Plan and the Sustainable Design and Construction Supplementary Planning Guidance. 5.19 The greenfield runoff for the Site has been estimated in accordance with “Rainfall Runoff Management for Developments” published by the Environment Agency (EA). Detailed calculations are contained within Appendix C for the Site. The calculations have been based on the Environment Agency procedure and a Microdrainage calculation has been undertaken utilising the same variables to verify the results. Greenfield runoff for 1 in 1, 30 and 100 year events is tabulated in Table 5.1 together with the mean annual runoff rate, Qbar.

Table 5.1 Permitted Equivalent Greenfield Runoff Rates

Return Period Greenfield Runoff Rate Permitted Discharge (years) (litres/second/hectare) (Three times Greenfield Runoff Rate) (litres/second/hectare) Qbar 1.5 4.5 1 1.3 3.9 30 3.4 10.2 100 4.8 14.4

5.20 Surface water will be attenuated on-site within feasible SuDS features constructed as an integral part of the illustrative masterplan. Features will be implemented with due regard to the ‘London Borough of Towers Hamlets SuDS Guidance’. The selection of appropriate SuDS features has been undertaken by considering the proposed density of the illustrative masterplan, land use and development plan as required by the Local Planning Authority.

5.21 A preliminary drainage strategy scheme for the illustrative masterplan is shown on Drawing Reference X contained in Appendix C. The strategy will be subject to consultation with stakeholders, agreement with the relevant authorities and further detailed design (as part of a future planning application for the Site, or any part thereof), but is presented as a broad indication of the features proposed for the Site. The following five distinct forms of attenuation are therefore proposed for the illustrative masterplan:

• Green or brown roofs on the roofs of residential blocks that are not occupied by mechanical and electrical plant. These roofs are intended to reduce the volume of runoff discharged from the Site when compared to a conventional roof and to create an ecological habitat;

• Void system provided beneath landscaped areas and permeable paving on any podium deck areas that are proposed to provide attenuation at a high level;

• Rainwater harvesting systems to enable uncontaminated runoff from roofs to be recycled within proposed dwellings in order to reduce the volume of surface water discharged from the Site;

• Rain gardens adjacent to private roads and parking areas to collect, attenuate and improve the quality of surface water runoff; and

• Areas of permeable paving in private road and parking areas that discharge to geo-cellular storage to provide both attenuation of surface water and improvement to the quality of runoff.

5.22 The dense urban nature of the illustrative masterplan limits the provision of open green space. It has therefore been assumed that basins, ponds or swales will not be feasible within the illustrative masterplan. It is not anticipated that any significant infiltration will be available within the Site; therefore soakaways and infiltration trenches are unlikely to be feasible.

5.23 A computer model of the strategic surface water drainage for the illustrative masterplan has been constructed using Microdrainage software. The model has been subjected to simulated rainfall events for 1, 30 and 100 year events, with 40% allowance for climate change, to determine that the proposed Sustainable Drainage Systems will be required to provide 3,400m 3 of attenuation storage to enable the peak discharge from the illustrative masterplan to be restricted to three times the equivalent greenfield rate for the storm return period simulated. As the location, type and extents of proposed green and brown roofs is to be confirmed at detailed design stage, the attenuation volumes have been calculated without consideration of these roofs to provide a worst case scenario. It is anticipated that once the details of green/brown roofs has been agreed, the drainage design can be further refined to take suitable account of their drainage benefits. Calculation output results from Microdrainage are contained within Appendix C to support the attenuation storage shown on the preliminary drainage strategy drawing.

5.24 For future maintenance of SuDS features within private areas, it is anticipated that a management company would be set-up and responsible for the buildings and SuDS features. It is not proposed that any individual household with bear responsibility for maintenance of SuDS features. The management company will recover an annual fee from residents for the upkeep of these features.

CONCLUSIONS AND RECOMMENDATIONS

27 06

CONCLUSIONS AND RECOMMENDATIONS

Introduction

6.1 This section provides the conclusions of the Flood Risk Assessment and Drainage Report and sets out the mitigation measures and further considerations recommended for later detailed design associated with any future planning application for the Site, or any part thereof. Flood Risk to the Site

• Based on the available datasets, the risk of flooding from tidal and fluvial sources to the Site is considered to be low. The Site is not shown to be at risk during the 1 in 1000 year annual probability flood event associated with the River Lea Navigation and is therefore designated Flood Zone 1. The definition of Flood Zone 2 across the eastern part of the Site is due to a historic flood event in 1947, prior to the development of the flood defence system along the Lower Lea Valley, rather than the current probability of flooding. The risk to the Site is therefore residual, in the event of a breach in the local flood defences.

• The future risk of fluvial flooding to the Site, accounting for the impacts of climate change, will depend on the maintenance of the local flood defences, and their raising in accordance with the statutory levels.

• The chief flood risk posed to the Site is that from surface water flooding. Run-off generated from the existing Site has been assessed as far in excess of the capacity of the existing outfalls under full bore conditions. The Site is currently considered to be susceptible to flooding from surface water runoff generated within the Site, with uncontrolled ponding and overland flow of flood water likely to occur on a regular basis.

• There is potential for the capacity of the existing sewer network (which is likely to have been designed for storm events up to a return period of 3.3% (1 in 30 years)) to be exceeded during extreme rainfall events. No attenuation devices have been identified within the existing Site and there is therefore potential for surface water to back up in the pipework and manholes and flood onto the surface once the capacity of the existing network is exceeded. When this occurs, flood water will pond or flow overland to exit the Site in an uncontrolled manner via the low points on the Site boundary. Flood Risk from the Illustrative Masterplan

• The illustrative masterplan will result in a reduction of the impermeable area across the Site. A preliminary drainage strategy has been developed for the illustrative masterplan and identifies how surface water flood risk could be reduced through the provision of a new surface water drainage network that incorporates Sustainable Drainage Systems (SuDS) to collect, attenuate and improve the quality of surface water generated by rainfall events with return periods of up to 1 in 100 years, including an additional allowance of 40% for climate change.

• The illustrative masterplan indicates that new buildings will be constructed within the Site, which have the potential to conflict with existing combined sewers that extend through the Site. Smaller diameter combined sewers that serve the existing buildings should generally be diverted to avoid proposed buildings to allow them to be retained to form outfalls for foul drainage networks that are extended through the Site to accommodate foul water generated by the illustrative masterplan. However, the illustrative masterplan should ideally be developed to incorporate easements for the existing trunk sewers to enable new buildings to be positioned 6m clear of the outer edge of the existing sewer to enable flows to be maintained, as it is unlikely to be practical to divert these strategic existing sewers.

• The illustrative masterplan comprises demolition of the existing commercial and industrial units and construction of a new residential led mixed use development providing approximately 1,691 residential dwellings together with additional retail and commercial units, a primary school and a Combined Heat and Power plant. The redevelopment will cause the peak foul discharge from the 28

Site to increase significantly. It will therefore be necessary to consider providing a cascading system of Sustainable Drainage Systems (SuDS) to enable the peak discharge from rainfall events with a return period of 1 in 100 years plus climate change to be reduced in order to create capacity within the existing combined sewers to enable the additional foul discharge from the illustrative masterplan to be accommodated without increasing the risk of sewer flooding. Mitigation Measures

6.1 The following mitigation measures are recommended for consideration on the Site:

• An 8m setback zone from the edge of the flood defences must be retained as shown in Appendix B Figure 1 Flood Risk Constraints Map;

• The current levels of the flood defences along the Site boundary should be surveyed and confirmed;

• For development to be considered appropriate at the Site, it will be necessary either to raise the defences to the statutory level for the lifetime of the development, or demonstrate that it will be possible to raise the defences in the future to meet the 6.2mAOD level for the year 2100;

• The Environment Agency has identified that the actions associated with the Water Framework Directive (WFD) of relevance to this Site include replacing the hard defences adjacent to the Site with soft defences to encourage biodiversity;

• Ideally, residential development should be located in areas of the Site designated Flood Zone 1. Development uses with lower vulnerability classifications, including retail, employment, public open space, should be directed towards the area of Flood Zone 2. If the primary school currently located in this area in the illustrative masterplan cannot be relocated, justification needs to be provided for its location;

• Finished floor levels for new development should be set at the standard level of 300mm above ground level;

• Given the proximity to the River Lea Navigation, occupants of the Site should consider signing up the Environment Agency Flood Warning Service; and

• There may be a risk of groundwater flooding during construction of new buildings. Groundwater levels should be monitored during construction to determine the risk of flooding and inform appropriate mitigation during construction. Preliminary Drainage Strategy

6.2 Surface water should be attenuated on-site within feasible SuDS features constructed as an integral part of the development. Features should be implemented with due regard to the ‘London Borough of Towers Hamlets SuDS Guidance’.

5.1 The following five distinct forms of attenuation have been identified for consideration in the preliminary drainage strategy for the Site:

• Green or brown roofs;

• Void system and permeable paving;

• Rainwater harvesting systems;

• Rain gardens; and

• Areas of permeable paving.

5.2 For future maintenance of SuDS features within private areas, it is anticipated that a management company would be set-up and responsible for the buildings and SuDS features. The management company will recover an annual fee from residents for the upkeep of these features.

REFERENCES

30 09

References

Ref. 1 London Legacy Development Corporation Local Plan 2015 to 2031 (2015)

Ref. 2 DCLG (2012); National Planning Policy Framework, Communities and Local Government Publications http://planningguidance.communities.gov.uk/ Ref. 3 DCLG (2014); National Planning Practice Guidance, Communities and Local Government Publications http://planningguidance.communities.gov.uk/

Ref. 4 London Borough of Tower Hamlets Level 1 Strategic Flood Risk Assessment, Capita Symonds (2008) Ref. 5 Flood Risk and Core Strategy General Sequential Test, London Borough of Tower Hamlets (2009)

Ref. 6 London Borough of Tower Hamlets Level 2 Strategic Flood Risk Assessment, Capita Symonds (2012)

Ref. 7 HMSO (2010); Flood and Water Management Act 2010 Ref. 8 Sustainable drainage systems: non-statutory technical standards - https://www.gov.uk/government/publications/sustainable-drainage-systems-non-statutory-technical- standards

Ref. 9 The London Plan: The Spatial Development Strategy for London – Consolidated with Alterations since 2011 (March 2015)

Ref. 10 Sustainable Design and Construction Supplementary Planning Guidance (2014)

Ref. 11 Environment Agency; Thames Estuary 2100 Plan (TE2100): ‘Managing flood risk through London and the Thames Estuary, November 2012’ Ref. 12 London Borough of Tower Hamlets Surface Water Management Plan, Capita Symonds (2011)

Ref. 13 London Borough of Tower Hamlets Draft Local Flood Risk Management Strategy (2014)

Ref. 14 London Borough of Tower Hamlets Sustainable Drainage Systems Guidance Document http://www.towerhamlets.gov.uk/lgnl/environment_and_planning/flood_risk_management.aspx

Ref. 15 Environment Agency River Lea Modelling Study, CH2M Hill (2014)

Ref. 16 Environment Agency, Adapting to Climate Change: Advice to Flood & Coastal Risk Management Authorities, February 2016. Ref. 17 Bromley by Bow Masterplan Engineering and Environmental Constraints and Considerations Report, Peter Brett Associates (2015)

Appendix A – Environment Agency Product 4 Data & Mapping

Flood Map for Planning centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

W a te rw o rk s R iv e r

o r w e iv C R s r Environment Agency rk e wo e er k 2 Bishops Square Business Park at W St Albans Road West

Hatfield

r e

v Hertfordshire Le i • e R Na AL10 9EX vig a ati e o s n ( l Lo e we n

r) n

a h

C 0 137.5 275 550

e r v i e

v R i

a R Metres e s a l e

e s n l n e a n h n

a Legend C

C C

h B a o n Main Rivers w n

e C l r s e e

B e a k o Flood Map for Planning w R

i C v r e e e r k Flood Storage Area er Riv lsea Areas Benefiting from Flood Defences nne Cha Flood Zone 3 Flood Zone 2

B e

e o

a C

i e

(

) Flood Map for Planning (assuming no defences)

Flood Zone 3 shows the area that could be affected by flooding: - from the sea with a 1 in 200 or greater chance of happening each year - or from a river with a 1 in 100 or greater chance of happening each year.

) al id (T Flood Zone 2 shows the extent of an extreme es m flood from rivers or the sea with up to a 1 in ha T 1000 chance of occurring each year. Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance 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 prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Detailed FRA centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e

e e k r

C Defended Flood Outlines

o B 1 in 2 (50%) Defended r ve Ri a lse 1 in 5 (20%) Defended ne an Ch 1 in 10 (10%) Defended 1 in 20 (5%) Defended

) r e The data in this map has been extracted from the River Lee

w o 2D Flood Mapping Study (CH2M Hill, 2014). L ( This was a catchment-scale mapping study, so may need local n o i updates for site-specific decisions. It should be noted that it was t a not created to produce flood levels for specific development sites g i v within the catchment. a k N e Modelled outlines take into account catchment-wide defences. e e r e Updates to model M03 were undertaken by the Lower Hall C L

w Sluices Operational Scenario Modelling (CH2M Hill, 2014), o B and updates to model M04 by the Lower Lee Tributaries Economic Appraisal project (CH2M Hill, 2015). Flood risk data requests including an allowance for climate change will be based on the 1 in 100 flood plus 20% allowance for climate change, unless otherwise stated. You should refer to ‘Flood risk assessments: climate change allowances’ to check if this allowance is still appropriate for the type of development you are proposing and its location. You may need to undertake further assessment of future flood risk using different allowances to ensure your assessment of future flood risk is based on best available evidence. https://www.gov.uk/guidance/flood-risk-assessments- climate-change-allowances Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance 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 prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Detailed FRA centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e

e e k r

C Defended Flood Outlines

o B 1 in 50 (2%) Defended r ve Ri a lse 1 in 75 (1.3%) Defended ne an Ch 1 in 100 (1%) Defended

) r e The data in this map has been extracted from the River Lee

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e

e e k r

C Defended Flood Outlines

o B 1 in 100+20% (*CC) Defended r ve Ri a lse 1 in 200 (0.5%) Defended ne an Ch 1 in 1000 (0.1%) Defended

) r e The data in this map has been extracted from the River Lee

L e e Environment Agency !( N a v 2 Bishops Square Business Park ig a R9A-1492 t k io e St Albans Road West n e r ( L C R9B_0404 Hatfield !( o !( w w !( e o r !( R9B-0355 Hertfordshire ) L B C • R9B-0413 R9A-1441u ee R9B_0404d h !( !( N a AL10 9EX av !(n i n ga !( R9B-0355d R9A-1441c R9B-0375 tio e l n s ( e !( Lo !( w a

e R9A-1366 !( r) R

i 0 50 100 200 v

!( e R9B-0305 r R9B-0266 !( Metres R9B-0202 !( Legend R9A-1281d B !( o w Main Rivers C R9B-0272 r k e e !( e e k r

C !(

w 1D Node Results o R9B-0077i B R9B-0241 R9A-1187 !( !( !( r Node Results ve Ri R9B-0077 a lse !( ne an Ch !( L-R10-1956u R9B-0080 R9B-0159 !(R9B-0020 !( !( L-R10-1956UI R9A-1103!( !(

) r e The data in this map has been extracted from the River Lee

w o 2D Flood Mapping Study (CH2M Hill, 2014). L L-R10-1956 ( This was a catchment-scale mapping study, so may need local n !( o i updates for site-specific decisions. It should be noted that it was t a not created to produce flood levels for specific development sites g i v within the catchment. R9A-1018 a k N e Modelled outlines take into account catchment-wide defences. !( e R10-1956DI e r e Updates to model M03 were undertaken by the Lower Hall C L !( w Sluices Operational Scenario Modelling (CH2M Hill, 2014), o B and updates to model M04 by the Lower Lee Tributaries Economic Appraisal project (CH2M Hill, 2015). L-R10-1876 Flood risk data requests including an allowance for R9A-0967!( climate change will be based on the 1 in 100 flood !( plus 20% allowance for climate change, unless otherwise stated. You should refer to ‘Flood risk assessments: climate change allowances’ to check if this allowance is still appropriate for the type of development you are proposing and its location. You may need to L-R10-1801 undertake further assessment of future flood risk using !( different allowances to ensure your assessment of future flood risk is based on best available evidence. R9A-0890B https://www.gov.uk/guidance/flood-risk-assessments- !( climate-change-allowances Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance Survey Material with the permission of Ordnance Survey on behalf of the controller o!(f Her Majesty's Stationery Office Crown Copyright. Unauthorised reproduction infringes Crown Copyright and may lead to prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Environment Agency ref: HNL7246MS

The data in this map has been extracted from the River Lee 2D Modelling study (CH2M Hill, 2014). Flood risk data requests including an allowance for climate change will be based on the 1 in 100 flood plus 20% allowance for climate change, unless otherwise stated. You should refer to ‘Flood risk assessments: climate change allowances’ to check if this allowance is still appropriate for the type of development you are proposing and its location. You may need to undertake further assessment of future flood risk using different allowances to ensure your assessment of future flood risk is based on best available evidence. https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances

Caution: This model has been designed for catchmentwide flood risk mapping. It should be notedthat it was not created to produce flood levels for specific development sites within the catchment. Modelled outlines take into account catchment wide defences.

All flood levels are given in metres Above Ordnance Datum (mAOD) All flows are given in cubic metres per second (cumecs)

MODELLED FLOOD LEVEL Return Period Node Label Easting Northing 2 yr 5 yr 10 yr 20 yr 50 yr 100 yr 100 yr + 20% 200 yr 1000 yr L-R10-1801 538331.3 182462.7 4.850 4.850 4.851 4.854 4.860 4.860 4.940 4.927 4.950 L-R10-1876 538338.5 182533.8 4.850 4.850 4.853 4.860 4.861 4.863 4.944 4.934 4.956 L-R10-1956 538367.2 182616.1 4.850 4.853 4.860 4.862 4.870 4.871 4.956 4.945 4.971 L-R10-1956u 538369.3 182687.4 4.851 4.853 4.860 4.862 4.870 4.871 4.966 4.955 4.986 L-R10-1956UI 538377.9 182660.3 4.851 4.853 4.860 4.862 4.870 4.871 4.966 4.955 4.986 R10-1956DI 538350.2 182574.4 4.850 4.852 4.860 4.860 4.870 4.870 4.953 4.942 4.970 R9A-0890B 538285.0 182433.7 3.316 3.442 3.574 3.871 4.786 4.954 4.990 4.987 5.016 R9A-0967 538287.3 182521.0 3.315 3.442 3.573 3.871 4.785 4.953 4.990 4.987 5.016 R9A-1018 538297.6 182583.4 3.316 3.442 3.572 3.870 4.783 4.953 4.990 4.986 5.016 R9A-1103 538322.4 182650.9 3.316 3.442 3.571 3.869 4.782 4.951 4.990 4.983 5.010 R9A-1187 538295.1 182734.6 3.317 3.442 3.570 3.868 4.780 4.944 4.972 4.972 4.994 R9A-1281d 538254.6 182791.8 3.317 3.442 3.570 3.867 4.778 4.941 4.967 4.966 4.984 R9A-1366 538199.0 182863.2 3.320 3.443 3.569 3.867 4.778 4.953 4.990 4.986 5.018 R9A-1441c 538175.0 182884.2 3.320 3.444 3.569 3.867 4.777 4.956 4.997 4.991 5.026 R9A-1441u 538132.2 182925.6 3.320 3.444 3.569 3.867 4.777 4.956 4.997 4.991 5.026 R9A-1492 538106.0 182961.6 3.321 3.444 3.568 3.867 4.777 4.954 4.993 4.987 5.021 R9A-1579 538072.8 183038.7 3.322 3.445 3.569 3.868 4.779 4.959 5.002 4.994 5.034 R9B_0404 538546.9 182922.1 4.913 4.961 5.000 5.024 5.078 5.104 5.204 5.189 5.256 R9B_0404d 538551.7 182901.0 4.880 4.905 4.930 4.950 4.990 5.010 5.108 5.094 5.151 R9B-0020 538397.5 182680.1 4.851 4.853 4.860 4.862 4.870 4.871 4.966 4.955 4.986 R9B-0077 538352.1 182715.8 4.851 4.853 4.860 4.862 4.870 4.871 4.966 4.955 4.985 R9B-0077i 538336.5 182744.0 4.851 4.853 4.860 4.862 4.870 4.871 4.969 4.957 4.990 R9B-0080 538439.3 182689.4 4.852 4.856 4.862 4.867 4.874 4.880 4.973 4.961 4.993 R9B-0159 538482.0 182704.7 4.855 4.860 4.870 4.872 4.881 4.885 4.981 4.969 5.002 R9B-0202 538301.2 182808.1 4.851 4.853 4.860 4.862 4.870 4.870 4.968 4.957 4.990 R9B-0241 538555.8 182766.4 4.860 4.864 4.872 4.880 4.891 4.895 4.991 4.979 5.015 R9B-0266 538297.5 182836.0 4.910 4.955 4.994 5.019 5.075 5.103 5.210 5.192 5.265 R9B-0272 538562.1 182777.3 4.870 4.891 4.911 4.926 4.957 4.972 5.070 5.057 5.110 R9B-0305 538289.1 182874.5 4.910 4.960 4.997 5.022 5.079 5.108 5.214 5.197 5.270 R9B-0305u 538278.2 182880.7 4.910 4.960 4.997 5.022 5.079 5.108 5.214 5.197 5.270 R9B-0355 538320.4 182916.4 4.910 4.960 5.000 5.023 5.080 5.108 5.215 5.198 5.270 R9B-0355d 538308.7 182894.8 4.910 4.960 4.997 5.022 5.079 5.108 5.214 5.197 5.270 R9B-0375 538227.2 182906.4 4.910 4.960 4.997 5.023 5.079 5.108 5.214 5.197 5.270 R9B-0413 538199.7 182902.5 4.910 4.960 4.997 5.023 5.079 5.108 5.214 5.197 5.270 R9B-0453 538336.6 183012.2 4.923 4.980 5.024 5.052 5.114 5.145 5.245 5.228 5.302 R9B-0453d 538321.7 182927.7 4.911 4.960 5.000 5.024 5.081 5.109 5.216 5.199 5.271 R9B-0517 538526.5 183002.6 4.916 4.966 5.006 5.032 5.088 5.115 5.215 5.200 5.268 R9B-0574 538495.7 183047.4 4.920 4.970 5.011 5.038 5.095 5.123 5.223 5.207 5.277 MODELLED FLOWS Return Period Node Label Easting Northing 2 yr 5 yr 10 yr 20 yr 50 yr 100 yr 100 yr + 20% 200 yr 1000 yr L-R10-1801 538331.3 182462.7 151.948 169.692 176.133 181.126 212.815 224.129 234.681 231.775 248.970 L-R10-1876 538338.5 182533.8 150.767 168.530 174.985 179.999 212.020 223.067 233.628 230.782 247.990 L-R10-1956 538367.2 182616.1 149.254 167.073 173.564 178.605 211.014 221.730 232.366 229.535 246.750 L-R10-1956u 538369.3 182687.4 41.962 46.674 48.633 50.364 60.226 61.552 65.116 64.292 70.694 L-R10-1956UI 538377.9 182660.3 148.068 165.958 172.474 177.529 210.236 218.130 226.028 223.955 240.014 R10-1956DI 538350.2 182574.4 149.934 167.720 174.194 179.225 211.463 222.325 232.928 230.092 247.270 R9A-0890B 538285.0 182433.7 13.190 13.532 13.964 15.088 21.613 25.512 22.140 26.130 20.793 R9A-0967 538287.3 182521.0 13.386 13.596 14.212 15.434 22.170 25.715 22.630 26.390 20.752 R9A-1018 538297.6 182583.4 13.522 13.691 14.440 15.705 22.660 25.942 23.020 26.680 20.982 R9A-1103 538322.4 182650.9 13.533 13.739 14.780 14.834 20.590 26.427 29.660 33.170 36.889 R9A-1187 538295.1 182734.6 13.492 13.795 15.106 15.210 20.741 37.345 49.423 44.561 59.883 R9A-1281d 538254.6 182791.8 13.511 13.848 15.250 15.447 21.012 37.413 49.416 44.466 59.888 R9A-1366 538199.0 182863.2 13.519 13.885 15.351 15.743 21.377 37.463 49.401 44.345 59.883 R9A-1441c 538175.0 182884.2 13.709 13.914 15.412 16.000 21.730 37.475 49.383 44.309 59.856 R9A-1441u 538132.2 182925.6 13.709 13.914 15.412 16.000 26.580 37.827 49.383 45.928 59.856 R9A-1492 538106.0 182961.6 13.873 13.933 15.517 16.168 26.475 37.760 49.368 45.841 59.785 R9A-1579 538072.8 183038.7 14.111 13.959 15.724 16.402 26.296 37.647 49.352 45.698 59.737 R9B_0404 538546.9 182922.1 92.979 107.700 113.151 121.744 143.849 149.326 155.522 153.883 168.990 R9B_0404d 538551.7 182901.0 92.979 107.700 113.151 121.744 143.849 149.326 155.522 153.883 168.990 R9B-0020 538397.5 182680.1 108.115 121.936 126.849 130.408 150.363 157.053 161.102 159.952 170.614 R9B-0077 538352.1 182715.8 41.271 46.021 47.996 49.812 59.693 61.009 64.454 63.703 70.246 R9B-0077i 538336.5 182744.0 40.728 45.514 47.487 49.375 59.284 60.365 61.641 61.395 63.639 R9B-0080 538439.3 182689.4 107.486 121.339 126.262 129.850 149.996 156.636 160.684 159.568 170.425 R9B-0159 538482.0 182704.7 106.727 120.616 125.552 129.180 149.563 156.129 160.208 159.116 170.240 R9B-0202 538301.2 182808.1 39.835 44.661 46.611 48.600 58.602 59.682 60.979 60.702 63.033 R9B-0241 538555.8 182766.4 93.990 108.640 114.064 122.060 144.165 149.635 155.560 154.165 169.040 R9B-0266 538297.5 182836.0 39.801 44.629 46.580 48.569 58.586 59.663 60.979 60.702 63.033 R9B-0272 538562.1 182777.3 93.990 108.640 114.064 122.060 144.165 149.635 155.560 154.165 169.040 R9B-0305 538289.1 182874.5 39.513 44.364 46.325 48.523 58.464 59.550 60.865 60.582 62.965 R9B-0305u 538278.2 182880.7 5.707 7.229 8.698 13.419 32.737 34.100 35.100 34.800 38.875 R9B-0355 538320.4 182916.4 38.230 43.693 45.713 47.294 48.840 48.471 51.335 50.233 51.614 R9B-0355d 538308.7 182894.8 38.705 43.854 45.830 47.386 48.924 48.830 51.295 50.268 51.491 R9B-0375 538227.2 182906.4 5.396 7.068 8.576 13.296 32.609 33.980 35.030 34.722 39.583 R9B-0413 538199.7 182902.5 5.261 6.997 8.522 13.241 32.552 33.930 35.000 34.690 36.962 R9B-0453 538336.6 183012.2 37.329 42.640 44.485 46.073 47.521 47.827 49.887 48.812 50.413 R9B-0453d 538321.7 182927.7 37.329 42.640 44.485 46.073 47.521 47.827 49.887 48.812 50.413 R9B-0517 538526.5 183002.6 92.061 106.798 112.519 121.485 143.586 149.074 155.546 153.650 169.010 R9B-0574 538495.7 183047.4 91.650 106.345 112.398 121.360 143.461 148.951 155.557 153.539 169.020 Detailed FRA centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.86 2D Node Results: Heights o !( !( B !( !( !( 4.86 4.86 !( r !( !( 1 in 2 (50%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.86 2D Node Results: Heights o !( !( B !( !( !( 4.86 4.86 !( r !( !( 1 in 5 (20%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.87 2D Node Results: Heights o !( !( B !( !( !( 4.87 4.87 !( r !( !( 1 in 10 (10%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

L e e Environment Agency N a v 2 Bishops Square Business Park ig a t k io e St Albans Road West n e r ( L C Hatfield o w w

e o r Hertfordshire ) L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

r Metres Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.88 2D Node Results: Heights o !( !( B !( !( !( 4.87 4.88 !( r !( !( 1 in 20 (5%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( 4.78 4.78 4.78 4.78 4.78 !( !( !( 4!(.78!( !( !( !( !( !( !(4.7!(8!( 4.78 4.78!( 4!(.78!( 4!(.7!(8 !( !( !(4.!(78!(4.78 4.78 !( !( 4.78 !( !( !( 4.!(78 !( 4.78 !(

L 4.78 e !( !( e Environment Agency N a !( v 2 Bishops Square Business Park 4.78 ig 4.78 a !( t k io e St Albans Road West n e r ( L C Hatfield o w w

4.78 e 5.08 o r Hertfordshire !( ) !( L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e r) R

i 0 50 100 200 v

4.78 4.78 r !( !( Metres Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.89 2D Node Results: Heights o !( !( B !( !( !( 4.89 4.89 !( r !( !( 1 in 50 (2%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( 4.9 4.9 4.9 4.9 4.9 !( !( !( 4!(.9!( !( !( !( !( !( !(4.9!( 4!(.9 4.9!( 4.!(9 !(4.9!( !( !( !( !( !(4.!(9 4.9 4.9 !( !( !( 4.9 4.9 !( !( !( 4.9!( !(4.9 !( 4.9 !(

L 4.9 4.9 e !( !( e Environment Agency N a !( v 2 Bishops Square Business Park ig 4.9 a !( t k i e St Albans Road West 4.9 o n e !( r ( L C Hatfield o w w

4.9 e 5.09 o r Hertfordshire !( ) !( L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e 4.9 r) R i 0 50 100 200 !( v e

4.9 4.9 r !( !( 4.9 Metres !( Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.89 2D Node Results: Heights o !( !( B !( !( !( 4.89 4.89 !( r !( !( 1 in 75 (1.33%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( 4.96 4.96 4.96 4.96 !( !( !(4.9!(6!( !( !( !(4!(.96!( !( !( !( 4.96 4.96 !( 4.!(96!( !( !( !( 4!(.9!(1 !(4.!(96!( 4.96 !(4!(.96!( !( !(4.!(96!( !( !( 4.96 !( 4.96 4.96!( !( 4.96!( 4.96 !( !(

L e !( !( e Environment Agency N 4.96 a !( v 2 Bishops Square Business Park ig a !( t k i e St Albans Road West 4.96 4.96 o n e !( !( r ( L C Hatfield o w w

4.96 e 5.11 o r Hertfordshire !( ) !( L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e 4.96 r) R i 0 50 100 200 !( v e

4.96 4.96 r !( !( 4.95 Metres !( Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.89 2D Node Results: Heights o !( !( B !( !( !( 4.89 4.89 !( r !( !( 1 in 100 (1%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( !( !( 5.01 5 5 5 5 3.84 5.22 !(5.0!(1!( !( !( !(5!(5 !( !(5 !( 5!( !( 5!( 5 !( !( 5 5!( !( !( !( !( !( !( !( !( !( 5 5 5 5 5 5 5 5.01 !( !( 5!( !( 5!( !( !( !( 5!( 5!( !( !( 5 !( 5 5 5 !( 5!( !( 5!( 5 !( !( 5.21 4.99 !( !(5.21 Environment Agency !( !( 4.99 5.21!( 4.99 !( 2 Bishops Square Business Park !( !( !( !( k 4.99 4.99 4.47 4.37 4.3 e 5.2 St Albans Road West e !( !( !( !( !( !( r !( C 5.2 Hatfield !( !( !( !( !( !( w 5 5.21 5.21 5.19 o Hertfordshire !( !( !( !( L B C • ee h N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e 5 r) R i 0 50 100 200 !( v e

5 4.99 r !( !( 4.99 Metres !( Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.99 2D Node Results: Heights o !( !( B 4.69 4.33 !( !( !( !( !( 4.99 4.99 !( r !( !( 1 in 100+20% (*CC) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( !( 5 5 5 4.99 4.99 5.21 !( !( 5!( 5!( !( !( !( !( 4!(.9!(9 !( !( !( 4.99 5!( !( 4.!(99!( !( !( !( !(4.9!(9!(4.!(99!( 4.99 !(4!(.99!( !( !( !( !(4.!(99!( !( !( 4!(.99 4.99 !( 4.99 4.99!( !( 4.!(99!( 4.99 !( !(

L e !( !( e Environment Agency N 4.99 a !( v 2 Bishops Square Business Park ig a 4.28 !( t !( k i e St Albans Road West 4.99 4.99 o 4.51 4.37 n e !( !( !( !( !( !( r ( L 4.31 C 5.19 Hatfield o !( !( !( !( !( w w

4.99 e 5.2 5.2 o r Hertfordshire !( ) !( !( !( L B C • ee h 5.09 N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e 4.99 r) R i 0 50 100 200 !( v e

4.99 4.99 r !( !( 4.98 Metres !( Legend

B o w Main Rivers C r k e e e !( e k r

C !( !(

w 4.98 2D Node Results: Heights o !( !( B !( !( !( 4.97 4.97 !( r !( !( 1 in 200 (0.5%) Defended M04 ve Ri a lse ne an Ch

) r e The data in this map has been extracted from the River Lee

!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( 5.04 5.03 5.03 5.03 3.4 3.9 4 5.27 !( 5!(.0!(4 !(5.0!(3!( !( !( !( !( !(5.0!(3!( 3.54!( !( 3.64 !( 4.02 5.28!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( 5.04 5.04 5.03 5.03 5.03 5.03 5.03 3.67 4.03 !( !( !( !( 5!(.03 !( !( !( !( !( !( 3.74 5.03!( !( !( 5.03 5.!(03 3.93 3!(.8!( !( 4!(.96 !( 5.03 !( !( !( 3!(.9 !( !( !( 3.9!(9 !( !( !( !( 5.03 4.02 5.27 !( !( 5.02 4.27!(4.!(25!( 4!(.2!( !( !( !( 4.1 !( 5.27 !( L !( !( !( !( !( !( !( !( !( !( 5.03 e 4.26 5.26 !( !( e !( !( !( !( !( !( !( !( 4.23 !( Environment Agency N 5.02 a 4.46 4.44 4.4 5.26 !( v !( !( !( !( !( !( !( !( !( 2 Bishops Square Business Park ig a 4.35 4.33 !( t !( !( !( !( !( !( !( !( k i e St Albans Road West 5.02 5.02 o 5.02 4.76 4.6 5.26 n e !( !( !( !( !( !( !( !( !( !( r !( ( L 4.43 C 5.26 Hatfield o !( !( !( !( !( !( !( !( w w

5.03 e 5.27 5.27 5.25 o r Hertfordshire !( ) !( !( !( !( L B C • ee h 5.26 N a AL10 9EX av n i n ga tio e l n s ( e Lo w a

e 5.03 r) R i 0 50 100 200 !( v e

5.02 5.02 r !( !( 5.01 Metres !( Legend

B o w 4.17 Main Rivers C !( !( r k 4.17 3.67 3.67 3.67 e e e !( !( !( !( !( e k r

C !( !( !( !( !( !(

w 4.86 4.3 3.9 3.67 5.01 2D Node Results: Heights o !( !( !( !( !( !( !( !( !( B !( !( !( !( !( !( !( !( !( !( 4.87 4.15 4.15 4.08 5.01 5.01 !( !( !( !( !( !( !( !( !( r !( !( 1 in 1000 (0.1%) Defended M04 4.2 ve Ri !( !( !( !( a 4.2 4.16 lse !( !( !( ne 4.2 an 4.17 Ch

5.01

!( ) r e The data in this map has been extracted from the River Lee

w Sluices Operational Scenario Modelling (CH2M Hill, 2014), o B and updates to model M04 by the Lower Lee Tributaries Economic Appraisal project (CH2M Hill, 2015). Flood risk data requests including an allowance for climate change will be based on the 1 in 100 flood plus 20% allowance for climate change, unless otherwise stated. You should refer to ‘Flood risk assessments: climate change allowances’ to check if this allowance is still appropriate for the type of development you are proposing and its location. You may need to undertake further assessment of future flood risk using different allowances to ensure your assessment of future flood risk is based on best available evidence. https://www.gov.uk/guidance/flood-risk-assessments- climate-change-allowances Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance 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 prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Historic Flood Map centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

W a te rw o rk s R iv e r

o r w e iv C R s r Environment Agency rk e wo e er k 2 Bishops Square Business Park at W St Albans Road West

Hatfield

r e

v Hertfordshire Le i • e R Na AL10 9EX vig a ati e o s n ( l Lo e we n

r) n

a h

C 0 137.5 275 550

e r v i e

v R i

a R Metres e s a l e

e s n l n e a n h n

a Legend C

C C

h B a o n Main Rivers w n

e C l r s e e

B e a k o R Flood Event Outlines w

i C v r e e e r k 1953 er Riv lsea nne 1947 Cha 1928

B e

e o

a C

i e

(

)

The historic flood event outlines are based on a combination of anecdotal evidence, Environment Agency staff observations and survey. Our historic flood event outlines do not provide a definitive record of flooding. It is possible that there will be an absence of datain places where we have not been able ) al id to record the extent of flooding. (T es am It is also possible for errors occur in the Th digitisation of historic records of flooding.

Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance 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 prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Defences centred on Bromley-by-Bow, East London, E3 3DA - 01/04/2016 - HNL7246MS

1 4 1 0 4 6 2 2 8

2 2

C 4 1 h 7 4 31 a 0 2 n

n 8

e 9 Environment Agency

8 l !. s k 0 e e 3 a 2 Bishops Square Business Park e 7 r R

C i v St Albans Road West 1 w 1 e 3 o 3 r 4 3 4 B 2 Hatfield 7 29 4 13 0 14 5 6 4 Hertfordshire 6 0 0 • 3 6 wer) 3 (Lo 7 ation 78 AL10 9EX Navig 0 Lee 21

1 7 4 6 3

2 3 1 0 50 100 200 9 7 1

3 7 7 3 0 7 Metres

01 144 1 Legend 4 2 2 40 B 399 9 4 o 14 5 1 w Main Rivers C r k e e

e e k r 7 7671 14402 C ASSET_ID 3

w 9 o 7 2 r B 1 ive 73 R !. 291791 7734 14471 ea els nn 0 ha 2 C 78 DEFENCE 7736 78021

55 ASSET_ID 7820 112259 142 7305 14254 112260 4 5 2 4 7306 1 14255 132440

1 7 ) r 4 7307 e 4 14293 134369 w 1 o L (

n 7308 o 14294 134370 i t a 9 g i 6 v 7309 a 3 k 14295 134371 4 N e

3 e e 1 r e C L 7310 w 14331 135636 o B

1 7311 14399 414282 7

3 7312 1 14400 414289 7397 14401

The following information on defences 1

7 has been extracted from the Asset 6 7 Information Management System (AIMS) Produced by: Partnerships & Strategic Overview, This map is based upon Ordnance 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 prosecution or civil proceedings. Environment Agency 100024198, 2015 Hertfordshire & North London Environment Agency ref: HNL7246MS

The following information on defences has been extracted from the Asset Information Management System (AIMS)

Defences Condition of Asset Design Standard of Downstream Upstream Asset ID Asset Type Asset Comment Asset Description Defences (1=Good, 5 Protection protection (years) Crest Level Crest Level = Poor) Masonry and concrete lined channel. Sheet steel piling up to Three 134369 defence fluvial Lined channel. 25 4.94 4.93 2 Mills Lane Rd bridge 135636 defence fluvial Lined channel Steel piling and concrete lined channel. 25 6.75 4.23 2 134371 defence fluvial Lined channel side Concrete walls and sheet steel piling up to Three Mills Lane 50 5.71 6.75 2 134370 defence fluvial Lined channel Concrete and steel piling lined channel. 100 5.38 3 Channel side lined with concrete and steel sheet piling with insitu 112259 defence fluvial_tidal Lined Channel 1000 5.81 5.23 3 concrete capping. 14293 defence tidal Three Mills Lane. 1000 5.73 5.73 2 7310 defence tidal Sugar House Lane Tidal wier 1000 5.49 5.49 2 7308 defence tidal Sugar House Lane. 1000 5.51 5.51 3 14294 defence tidal Hunts Lane 1000 5.48 5.48 3 78021 defence tidal Three Mills. T6.New development on site. 1000 5.48 5.48 2 7311 defence tidal Bison Rd Footpath. Includes Prescott Lock 1000 6.59 6.59 2 414282 defence fluvial Wall 1000 7736 defence tidal Lee Valley Parks Updated for Prescott Lock 1000 5.48 5.48 2 Pre-cast concrete piles with insitu concrete capping. Crest raised by 112260 defence fluvial_tidal Lined Channel 1000mm to the rear of properties along Bisson Road, Bromley-by-Bow. 1000 5.63 5.41 2 Footpath to crest. Face out wall unseen. BW are responsible authority 414289 defence fluvial wall 1000 132440 defence fluvial_tidal Prescott Channel Sides Concrete lined channel sides 1000 5.75 5.51 3 7309 defence tidal Hunts Lane. 1000 5.48 5.48 3 7312 defence tidal Three Mills Island Studio. T6 1000 6.49 6.49 3 14400 defence tidal Three Mills 1000 4.46 4.46 2 Defence level lower than recommended design level. Problems on HW 14401 defence tidal Three Mills 1000 4.46 4.46 3 16/12/05 Advice to sandbag not heeded. Three Mills Lane London 7305 defence tidal Island section between Bow Creek & River Lee Navigation 1000 5.73 5.73 2 E3 3DU 14295 defence tidal Bison Rd footpath Requires subdivision 1000 6.49 6.49 2 Hedges & Butler/Clock 14399 defence tidal 1000 5.48 5.48 3 House. 14402 defence tidal Three Mills. 1000 5.48 5.48 2 7306 defence tidal Three Mills Green 1000 5.49 5.49 2 7734 defence tidal Mill Meads Requires subdivision. 1000 5.73 5.73 3 7307 defence tidal Three Mills. 1000 6.4 6.4 3 7820 defence tidal British Rail T6 1000 5.49 5.49 3 7397 defence tidal Three Mills Island Studio. Works planned 1000 5.49 5.49 4 14255 defence tidal Crows Rd, London E15 3 1000 5.49 5.49 3 14254 defence tidal Crows Rd, London E15 3 T6 1000 5.49 5.49 3 Bromley-by-bow District 14471 defence tidal 1000 5.49 5.49 3 Line Bridge 7671 defence tidal West Ham Gas Works Defence requires subdividing. 1000 5.49 5.49 3 14331 defence tidal Bison Rd footpath T6 1000 6.49 6.49 3 Structures Condition of Asset Asset ID Asset Type Asset Comment Structures (1=Good, 5 Protection = Poor)

291791 structure fluvial Sluice gates designed to impound water for Navigation purposes. Completion in Summer 2008. 2

Appendix B – Flood Risk Constraints Map

THIS DRAWING IS TO BE USED ONLY FOR THE PURPOSE OF ISSUE THAT IT WAS ISSUED FOR AND IS SUBJECT TO AMENDMENT LEGEND Site Boundary Development Free Buffer Zone Flood Zone 2 Illustrative Ground Floor Plan A Use B Use C Use D Use

Based up boundaries sourced from London borough planning portals Copyright Reproduced from Ordnance Survey digital map data © Crown copyright 2016. All rights reserved. Licence number 0100031673 Copyright © and Database rights Environment Agency 2016. All rights reserved. Some of the information within the Flood Map is based in part on digital spatial data licensed from the Centre for Ecology and Hydrology © NERC

Purpose of Issue DRAFT

Client d x DANESCROFT LAND LIMITED m . s t n i a r Project Title t s n o C k s i BROMLEY-BY-BOW R d o o l SOUTH F

1 e r u g i

F Drawing Title \ s p a M _ 2 0 \ h t u FLOOD RISK CONSTRAINTS o S w o B y b y Drawn Checked Approved Date e l m JW AH VN 12/04/2016 o r B AECOM Internal Project No. Scale @ A3 3 4 5

8 60488543 1:1,500 8 4

0 THIS DOCUMENT HAS BEEN PREPARED PURSUANT TO AND SUBJECT TO THE 6 \ TERMS OF AECOM'S APPOINTMENT BY ITS CLIENT. AECOM ACCEPTS NO LIABILITY s

m FOR ANY USE OF THIS DOCUMENT OTHER THAN BY ITS ORIGINAL CLIENT OR e t FOLLOWING AECOM'S EXPRESS AGREEMENT TO SUCH USE, AND ONLY FOR THE s y PURPOSES FOR WHICH IT WAS PREPARED AND PROVIDED. S n o i AECOM t a Scott House m r Alençon Link, Basingstoke o f

n Hampshire, RG21 7PP I

- Telephone (01256) 310200

4 Fax (01256) 310201 0

0 www.aecom.com 5 \ : K : Drawing Number Rev e m a N e l i 20 0 20 40 60 80 100 M ± FIGURE 1 F

Appendix C – Preliminary Drainage Strategy

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