Land North of Solent Road, Havant

Havant Borough Council Hearing Statement Matter 1 – Legal Compliance

Prepared on behalf of Portsmouth Water

Email: [email protected] tetratecheurope.com Tetra Tech Limited. Registered in England number: 1959704 Registered Office: 3 Sovereign Square, Sovereign Street, Leeds LS1 4ER VAT No: 431-0326-08.

Matter 1 Hearing Statement HBC Examination

Document control

Document: HBC Local Plan Stage 1 Examinations – Matter 1 Hearing Statement

Project: Land North of Solent Road, Havant

Client: Portsmouth Water

Job Number: 784 – A114230

File Origin: \\SOUTHAMPTON14\Shared\data\2019\HP19088 - A114230 Solent Road - new HQ Building

Revision:

Date: 16.06.2021

Prepared by Checked by Approved By Justin Packman Chris Lyons Chris Lyons

tetratecheurope.com 1 Matter 1 Hearing Statement HBC Examination

1. Introduction

1.1 This statement has been prepared in support of representations made towards the emerging Havant Brough Local Plan on behalf of Portsmouth Water in respect of their site at Land North of Solent Road Havant as identified on the plan attached at Appendix 1.

1.2 The site comprises undeveloped scrubland, with a small area of hard standing forming a tennis court located towards the eastern edge of the site. Its area measures circa 1.50ha. The site is relatively well enclosed and screened by existing planting, particularly on its northern and southern boundaries and is located in a highly sustainable with excellent access to facilities and services due to its central location in Havant, and its proximity to public transport and the strategic road network.

1.3 Tetra Tech Planning (formerly WYG) have previously made representations in response to the Regulation 19 Havant Local Plan 2036 in December 2020 and March 2019.

1.4 This Hearing Statement sets out our Client’s position in relation to Matter 1 of the examination in relation to Legal Compliance.

1.5 In relation to Matter 1, we do not consider the submitted local plan meets the Legal Requirements for plan making and, as presently drafted, is no considered sound.

1.6 Specifically we consider that the plan fails to meet matter 1.3 as set out in the Schedule of Matters and Issues for the Examination (Stage 1 Hearings), specifically the Plan’s formulation has not:

‘…been based on a sound process of SA in accordance with the regulations and relevant guidance, including the testing and/or consideration of reasonable alternatives for all policies in the Plan’

1.7 This statement contains details of: • Those parts of the plan are considered not sound; • The soundness test the plan fails and why, and • What changes are required to make the plan sound.

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1 Matter 1 Hearing Statement HBC Examination

1.8 This statement should be read alongside the previously submitted Regulation 19 submissions which will be expanded upon verbally at the relevant hearing sessions.

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2. Sustainability Appraisal

2.1 Our client’s representations relate to employment elements of Policy DR1 (Delivering Sustainable Development in Havant Borough), Paragraphs 2.43 – 2.54 and Table 3.

2.2 The plan is considered not sound because it fails to meet test ‘b’ as set out in paragraph 35 of the National Planning Policy Framework. Test ‘b’ requires plans to be:

‘b) Justified – an appropriate strategy, taking into account the reasonable alternatives, and based on proportionate evidence’

2.3 In this instance the Policy is not justified for two reasons.

1 - Havant Borough Council (HBC) have failed to allocate additional employment land despite being presented with overwhelming evidence relating to the need for significant more housing numbers which in turn results in the need for more employment land to provide jobs for those residents;

2 – The exclusion of our client’s site at Solent Road from the employment allocations within the plan despite being presented with robust evidence relating to the site’s suitability.

1. Need for additional employment land

2.4 Evidence presented elsewhere (including that presented by Portsmouth Water) clearly indicates that the draft Local plan substantially underprovides for the future housing needs of the borough. As new housing development has a significant bearing on employment land requirements, HBCs shortfall in housing land suggests a similar shortfall in employment land. Even if HBC were not to fully accept the housing evidence provided, additional employment land should be allocated to provide added flexibility1 to enable HBC to react to changes in employment requirements during the plan period.

1 NPPF para.s 11 (a) and 81 (d) tetratecheurope.com

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2. Suitability of site for new Development

2.5 The exclusion of the site appears to stem from the Council’s Strategic Flood Risk Assessment (SFRA) from November 2018, which dismissed the allocation of the site due to its failure to meet the sequential test for Flood Risk.

2.6 The conclusion reached within the SFRA was that:

‘The EA have indicated that the key issue on this site is the offsite implications of flooding from development of the site i.e. floodplain compensation. Previous work has given confidence that an employment use can be safely delivered. On that basis, there is a prospect of safe delivery, although a detailed assessment of this would be required at application stage, in particular in relation to flood storage compensation, so any allocation policy would need to be heavily caveated with assessment requirements.’

2.7 The site had been previously allocated for a new Headquarters building for Portsmouth Water (Site BD14 Adopted Allocations Plan 2014) and had passed the sequential test for operational reasons as there were no other reasonable alternative sites suitable for Portsmouth Water’s needs.

2.8 Whilst during the period following allocation Portsmouth Water had considered other sites, this did not in itself provide a justification for removing the employment allocation from the site. As stated in our previous representations EA flood advice on the sequential test clearly does not require the sequential test to be carried out again for developments of the same type.

2.9 Notwithstanding this Portsmouth Water are now fully committed to relocating to Solent Road and the Council are fully aware of this and were involved in a public meeting with Portsmouth Water about the new site. Tetra Tech Planning have recently submitted an application to HBC on behalf of Chancerygate who are pursuing the development of the site

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4 Matter 1 Hearing Statement HBC Examination

for Portsmouth Water. The proposal is for:

‘Proposed Portsmouth Water HQ (E(g)(i) and new employment (b2/B8/E(g)(iii) floorspace and associated access, landscaping and works at land north of Solent Road.’

2.10 The application has been registered under reference APP/21/00601.

2.11 Submitted with the planning application is a comprehensive Flood Risk Assessment (FRA) prepared by I & L Consulting (April 2021). A copy of the FRA is attached as Appendix 2.

2.12 The submitted FRA confirms that Portsmouth Water are ‘undertaking flood alleviation works to the adjoining watercourse. This work is being undertaken under Environmental Permit licence number EPR/PB3294JJ. The works are underway and when completed the site will remain flood free during the 1 in 100 year plus climate change scenario. This flood alleviation works will therefore satisfy the concerns raised in the SFRA and therefore the proposed commercial use for the site is acceptable.’

2.13 With the works completed the site will be located in Flood Zone 1 and therefore will be a sequentially preferable site, suitable for the proposed scheme currently at application stage.

Changes required to the plan

2.14 In order to make the emerging Local Plan sound, land north of Solent Road should be reinstated as an employment allocation. It was incorrect to remove the site in the first instance as the sequential test had already been passed on the site but now the Council is aware that Portsmouth Water are still intending to locate their headquarters on the site and the planning application demonstrates this is achievable in flood terms. This would be the most appropriate strategy for the site based on the evidence submitted about flood risk, and the steps being taken to mitigate that risk.

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3. Summary and Conclusions 3.1 This statement demonstrates that the plan, as currently drafted has not been based on a sound process of Sustainability Appraisal with the conclusions reached in the SFRA being ill informed. Evidence has been submitted (now and through earlier representations) to demonstrate that the conclusions reached relating to flood risk at Solent Road were incorrect. Work is being undertaken to mitigate flood risk at the site, placing the site into Flood Zone 1 and making it sequentially preferable in terms of flood risk.

3.2 Given the above, reinstating the employment allocation at Solent Road would now be entirely justified and represents the most appropriate strategy in terms of the allocation of employment land, by both allowing a major local employer to relocate their headquarters within the Borough and deliver additional employment floorspace to retain flexibility within the spatial strategy throughout the plan period.

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Appendix 1 Location Plan for Land North of Solent Road

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NOTES

Reproduced from the Ordnance Survey map with the permission of the Controller of Her Majesty's Stationery Office, © Crown Copyright.

C A Cornish & Associates Ltd Licence no LIG0908.

Subject to Statutory Approvals. Portsmouth Water

7.3m

5 The Wendy N

House 7

6.1m Brockhampton Springs

Water

Issues

Tank D 9

R Rev Description Chk Date N The Old O

T Manor House

M e

r A Peer House t

S K Tennis Courts 8 -14 Verulam Street C n

O t London WC1X 8LZ

R p

c tel +44(0)20 7400 2120

r B SITE [email protected]

1 t

o 6 architects

t www.cornisharchitects.com o

0 Manor Court

o cornish

1 6 4 1 Project Title.

The 0

5 Bosmere

SOLENT ROAD

Medical Centre 2

2 HAVANT

6 Drawing Title. 2 E N A L N SITE LOCATION PLAN O T P M A H K C O Drawing Status. Gas Gov R B TOWN PLANNING

SOLENT ROAD 0 12.5 75 metres

Drawn By. Scale. Date. Chk'd By.

27 ED 1:1250@ A3 17/09/2020 XX

Drawing No. Rev. 19003 - TP - 001 -

Appendix 2 Flood Risk Assessment for Land North of Solent Road prepared by I&L Consulting Ltd.

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Land North of Solent Road, Havant

Flood Risk Assessment

Chancerygate (Erdington) Limited

21-012_Land North of Solent Road, Havant

13th April 2021

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Quality Control

Prepared by Checked by Approved by

Rishad Manil Ismail Laher Ismail Laher Senior Engineer Director Director

Revision History

Revision Revision date Details Authorized Name Position

Final 14.04.2021 Submission for Full Planning IL Ismail Laher Director

Prepared for: CHANCERYGATE (ERDINGTON) LIMITED

Prepared by:

I&L Consulting Ltd. 29-31 Castle Street, High Wycombe, Buckinghamshire, HP13 6RU

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

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Table of Contents

1. Introduction ...... 4 2. Planning Policy and Evidence ...... 6 3. Site Description ...... 8 4. Existing Flood Risk ...... 10 5. Flood Risk from the Proposed Development ...... 13 6. Conclusion ...... 20 Appendix A Ardent flood modelling + EA permit (EPR/PB3294JJ) ...... 21 Appendix B SFRA assessment of site ref HB36 ...... 22 Appendix C Topographical Survey & Utility Maps ...... 23 Appendix D Proposed Development Plan ...... 24 Appendix E Proposed Drainage Strategy Layout ...... 25 Appendix F Hydraulic Calculation ...... 26

Figures

Figure 1: Site Location Plan ...... 8 Figure 2: See Appendix A for full Ardent flood model details ...... 10 Figure 3: Surface Water Flood Risk Map (Source: https://flood-warning-information.service.gov.uk) ...... 11

Tables

Table 1: Collected Data ...... 5 Table 2: Peak rainfall intensity allowance in small and urban catchments (Ref: Flood risk assessments: climate change allowances Guidance by EA, February 2016) ...... 7 Table 3: Summary of flood risk to the Site ...... 12 Table 4: Existing/Proposed Surface Water Runoff………………………………………………………………………..14 Table 5: Pollution Mitigation Assessment for the site……………………………………………………………………..14 Table 6: Assessment of Suitability of SuDS at the site as the drainage hierarchy ...... 15 Table 7: Management and Maintenance Strategy ...... 18 Table 8: Summary of flood risk to the development...... 19

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

1. Introduction

I&L Consulting Limited (I&L) was commissioned by the Applicant, Chancerygate (Erdington) Limited, to undertake a Flood Risk Assessment (FRA) for a new headquarter for Portsmouth Water along with new industrial/warehouse units off Solent Road in Havant. The site lies within the authority of Havant Borough Council (HBC).

The relevant national planning guidance is set out by the National Planning Policy Framework (NPPF, updated in 2019). A FRA is required because the proposed development is over 1 ha. The FRA must assess all aspects of flood risk both to the proposed development itself and also the potential impact on people and property elsewhere within the catchment.

1.1 Study Aims and Objectives

The overall objective of this study was to carry out a FRA that meets the requirements of the NPPF and HBC flood risk policies. These consider surface water runoff management and the specific needs of the Environment Agency (EA), HBC and Southern Water. The study is required to assess all aspects of flood risk to the proposed development, the potential impacts of the development on people and property elsewhere within the catchment and identify possible mitigation measures to ensure that the development is safe in the event of a flood. To achieve this aim, the following key actions were undertaken:

• Obtain flood data from the EA and HBC;

• Review topographical and flood risk data to identify the existing flood risk posed to the site from all sources;

• Assess the residual flood risk post-development;

• Consider the vulnerability of the users and the development, taking account of the vulnerability classification;

• Assess the safety of the route of access/egress from the site in a flood event;

• Identify suitable mitigation measures to protect the development site against flooding; and

• The production of a conceptual surface water drainage strategy for the proposed development.

1.2 Scope of Works

In order to meet the above objectives, the following scope of work and tasks were undertaken:

• Task 1: Data Collection. I&L Consulting collected relevant available information on the nature of the flooding at the site. The Applicant and their consultant team have provided information about the site and proposed development layout and design.

• Task 2: Identification of Current and Post-Development Flood Risk. The existing and post- development flood risk posed to the site was assessed from the data that was collected in Task 1. The assessment identifies the flood risk from all potential sources of flooding and includes consideration of the impact of climate change on flood risk.

• Task 3: Assessment of Site Safety. I&L Consulting considered whether flood resilience measures needed to be undertaken and the safety of the route of access/egress from the site.

1.3 Data Collected

Table 1 lists the data that has been collected as part of this assessment. Comments on the source and the nature of the data are also provided.

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Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Table 1: Collected Data

Purpose Data and Source Comments

Identification of site location Ordnance Survey Map Identifies the position of the site and local hydrological features

Identification of flood risk Environment Agency Flood Map Risk of flood from tidal and fluvial sources Topographical Survey Existing site levels and topography

Development details (drawings for Information on the layout of the existing site and proposed proposed development development)

Strategic Flood Risk Assessment Reports that identify existing flood risk (SFRA) information within the area and considerations for development.

Portsmouth Water / Ardent Consulting Flood modelling along with flood Engineers (Flood Alleviation works to alleviation works are in the process of adjoining watercourse) being completed to the adjoining watercourse. These works have a material impact on the flood risk to the site, reducing the risk from the site from high to low/medium.

Identification of the existing drainage Sitewide Drainage Plan Asset plans and drainage drawings network identify public and private sewers nearest to the site.

Identification of ground conditions British Geological Society (BGS) Identifies the type of aquifer, borehole logs and site investigation groundwater level, permeability and reports. geotechnical information

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

2. Planning Policy and Evidence

2.1 National Planning Policy Framework

The NPPF sets out what needs to be taken into account by developers to assess whether a proposed development is likely to be at risk of flooding or has the potential to increase flood risk elsewhere. Within the recently published updated NPPF (February 2019), the principles relating to flood risk management remain mostly unchanged from the 2012 version.

The overall objective of the NPPF is to steer development towards areas of lowest flood risk. NPPF policy aims to ensure flood risks have been taken into account and appropriate measures put in place to ensure that:

• The development is safe;

• Where possible, the flood risk overall is reduced;

• Increased flood risk does not occur elsewhere; and

• Appropriate mitigation measures are employed to deal with these effects and risks.

Paragraph 163 and footnote 50 of the NPPF outlines 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.

The current EA Flood Map shows that a large part of the site is located in land designated as Flood Zone 3 (high probability of fluvial flooding) and is shown as undefended. The north eastern corner is shown to be in Flood Zone 1 (low probability of flooding). The site is greater than 1 ha.

Portsmouth Water along with their consultant Ardent have submitted flood modelling and are undertaking flood alleviation works to the adjoining watercourse. This work is being undertaken under Environmental Permit licence number EPR/PB3294JJ. The works are underway and when completed the site will remain flood free during the 1 in 100 year plus climate change scenario. See Appendix A for relevant information.

The NPPF considers the vulnerability of different forms of development to flooding; and classifies the proposed development as ‘Less Vulnerable’.

2.2 Havant Borough Council – Core Strategy

Policy CS15 Flood and Coastal Erosion Risk

Development in areas at risk of flooding now and in the future as identified on the latest Environment Agency flood risk maps and Strategic Flood Risk Assessment climate change maps will only be permitted where:

1. It meets the sequential and exception test (where required) in relation to PPS25.

2. The site is located in a low hazard area as defined in the Strategic Flood Risk Assessment.

3. A site-specific flood risk assessment demonstrates that the development will be safe, including the access, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall.

4. The scheme incorporates flood protection, flood resilience and resistance measures appropriate to the character and biodiversity of the area and the specific requirements of the site.

5. Appropriate flood warning and evacuation plans are in place.

6. New site drainage systems are designed taking account of events which exceed the normal design standard.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

All development will be required to ensure that there is no net increase in surface water run off. Priority should be given to incorporating Sustainable Drainage Systems (SuDS) to manage surface water drainage, unless it is proven that SuDS are not appropriate. Where SuDs are provided arrangements must be put in place for their whole life management and maintenance.

The council will work with partners to implement the Coastal Policy Zones in the North Solent Shoreline Management Plan to ensure that development avoids areas at risk from coastal erosion and coastal flooding and that areas required to offset coastal squeeze and prevent habitat fragmentation, to allow species to adapt to climate change, are identified and protected from development.

2.3 Strategic Flood Risk Assessment (Local Plan Sites), November 2018

The proposed site has been assessed to show that flood risk has been fully taken into account when allocating this site. The SFRA assessment has been appended to this report as Appendix B. Extract from the report as follows:

Conclusion on prospect of safe development in light of flood risk

The EA have indicated that the key issue on this site is the offsite implications of flooding from development of the site i.e. floodplain compensation. Previous work has given confidence that an employment use can be safely delivered. On that basis, there is a prospect of safe delivery, although a detailed assessment of this would be required at application stage, in particular in relation to flood storage compensation, so any allocation policy would need to be heavily caveated with assessment requirements

Portsmouth Water along with their consultant Ardent are undertaking flood alleviation works to the adjoining watercourse. This work is being undertaken under Environmental Permit licence number EPR/PB3294JJ. The works are underway and when completed the site will remain flood free during the 1 in 100 year plus climate change scenario.

This flood alleviation works will therefore satisfy the concerns raised in the SFRA and therefore the proposed commercial use for the site is acceptable.

2.4 Climate Change

The Flood risk assessments: Climate Change Allowances Guidance published in February 2016 indicates that climate change is currently expected to result in increased rainfall and rising sea levels. Table 2 below shows anticipated changes in extreme rainfall intensity in small and urban catchments.

Table 2: Peak rainfall intensity allowance in small and urban catchments (Ref: Flood risk assessments: climate change allowances Guidance by EA, February 2016)

Applies across all of Total potential change Total potential change Total potential change England anticipated for the ‘2020s’ anticipated for the ‘2050s’ anticipated for the ‘2080s’ (2015 to 2039) (2040 to 2069) (2070 to 2115)

Upper End 10% 20% 40%

Central 5% 10% 20%

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

3. Site Description

The proposed development site which is the subject of this Flood Risk Assessment (FRA) is situated in a strategic location north of Solent Road in Havant. The development will be accessed via the existing access road off Solent road which currently serves the existing medical centre.

The proposed development will consist of a new headquarter for Portsmouth Water along with a terrace of new industrial/warehouse units with associated parking, soft landscaping and HGV turning areas. The total development site rises gently from west to east with a total site area of 1.4983Ha.

The existing site is undeveloped. The proposal would be to drain the developed site by gravity and discharge at a Greenfield restricted rate using a flow control into either the existing private surface water sewer crossing the site or direct to the adjoining watercourse, see Appendix E.

The site location plan is shown in Figure 1 below.

Figure 1: Site Location Plan 3.1 Topography and Hydrological Setting

Environment Agency (EA) river mapping shows that the nearest watercourse is the Brockhampton Stream, which is located to the north and west of the site.

The topographic survey (Appendix C) indicates that the site levels fall from west to east. Spot levels taken from topographical survey as follows east (5.75m AOD) to west (5.00m AOD).

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Existing site survey and utility plan shows a potential surface water private sewer crossing the site from the north east to the south west where this connects into the Watercourse. The proposal would be to either connect the new drainage from the development to this sewer or make a new connection via a headwall to the adjoining watercourse. Surface water will be restricted to a Greenfield discharge rate.

The existing public Foul Water sewer crossing the site will be diverted prior to undertaking any works on site. This proposed diversion works has been agreed with Southern Water.

Please see Appendix D.

3.2 Geology and Hydrogeology

British Geological Survey (BGS) mapping indicates the site is located on permeable chalk geology with impermeable London Clay Formation bedrock to the north.

An intrusive site investigation has been undertaken by Delta-Simons. The investigations found the site to consist of a variable thickness of topsoil and Made Ground, which is in turn underlain by superficial deposits comprising of Alluvium, Head Deposits and River Terrace Deposits, followed by Chalk bedrock. Monitoring of standpipes identified shallow groundwater at the Site.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

4. Existing Flood Risk

This section of the report identifies the existing risks from the different forms of flooding identified in NPPF.

4.1 Fluvial & Tidal Flooding

The EA has produced Flood Zone maps for much of England and Wales. The current displayed map for the site shows that a large part of the site is located in land designated as Flood Zone 3 (high probability of fluvial flooding) and is shown as undefended. The north eastern corner is shown to be in Flood Zone 1 (low probability of flooding).

Figure 2 below has been extracted from the approved revised flood model assessment which shows that following completion of the flood alleviation works the site will lie within Flood Zone 1 (low risk).

Figure 2: See Appendix A for full Ardent flood model details

On the coast storm surges and high tides can threaten low lying coastal areas and can be sometimes large and rapid enough to overtop defence works, causing significantly more damage than river flooding. Tidal flooding is not considered a risk to the site due to the inland location of the development.

Therefore, flood risk from fluvial and tidal sources to the site is considered to be low.

4.2 Surface Water Flooding

Surface water flooding occurs when rainfall is unable to infiltrate into the ground and/or engineered drainage networks and accumulates on the surface.

The risk of flooding from surface water is presented in the GOV.UK online map at a strategic scale. It can be seen from the surface water flood map in Figure 3 that the site is shown to have a medium risk of flooding

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

but this surface water flooding is associated with the adjoining watercourse and network of drainage in the area. Following the flood alleviation works the risk from surface water flooding from the site will be low level and unlikely to cause any risk to the site.

Figure 3: Surface Water Flood Risk Map (Source: https://flood-warning-information.service.gov.uk) Given the topography, existing drainage system and surface water flood map information, the site is understood to be at a low risk from surface water flooding.

4.3 Groundwater Flooding

The site geology is expected to consist of a Made Ground, which is in turn underlain by superficial deposits comprising of Alluvium, Head Deposits and River Terrace Deposits, followed by Chalk bedrock. Shallow groundwater has been recorded at the Site. The proposed finished surface and finished floor levels will be raised from current ground levels. The impact of water level rises in the adjoining watercourse and subsequent groundwater levels rising would therefore have limited impact on the proposed development.

The existing flood risk from groundwater is therefore considered to be medium risk.

4.4 Sewer Flooding

A sewer flood is often caused by surface water drains discharging into the combined sewer systems; sewer capacity is exceeded in large rainfall events causing the backing up of floodwaters within properties or discharging through manholes. Most adopted surface water drainage networks are designed to the criteria set out in Sewers for Adoption. One of the design parameters is that sewer systems be designed such that no flooding of any part of the site occurs in a 1 in 30-year rainfall event. By definition a 1 in 100- year event would exceed the capacity of the surrounding sewer network as well as any proposed drainage.

To ensure that sewer and surface water flooding is not exacerbated; surface water must be considered within the design of the site. This ensures that any additional surface water and overland flows are managed correctly, to minimise flood risk to the site and the surrounding area.

As mentioned in section 3.1 above, the site is will have new surface and foul water connection points. The discharge from the site will be restricted to Greenfield runoff rates therefore not increasing flows from the site.

Therefore, the risk of sewer flooding to the site is considered low.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

4.5 Artificial Sources of Flooding

The EA Flood Risk from Reservoirs mapping indicates that the site is located outside of an area of potential risk from flooding. There has been no loss of life in the UK from reservoir flooding since 1925.

Figure 4: Reservoir Flood Risk Map. (Source: https://flood-warning-information.service.gov.uk)

Therefore, the risk from this type of flooding can be considered low.

4.6 Summary of Existing Flood Risk

The flood risk from fluvial & tidal flooding, surface water flooding, sewer flooding and groundwater is assessed to be low.

The flood risk to the site is summarised in Table 3.

Table 3: Summary of flood risk to the Site

Type of Flooding Source of Flooding Existing Flood Risk

Brockhampton Stream (flood alleviation works Fluvial and Tidal underway Environmental Permit licence Low number EPR/PB3294JJ)

Surface Water Runoff from the site and surrounding land Low

Sewers Surrounding public foul drainage systems Low

Ground Water Underlying geology and groundwater levels Medium

Artificial Sources none n/a

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

5. Flood Risk from the Proposed Development

The proposal aims to provide new headquarter office/water testing premises for Portsmouth Water, new industrial/warehouse units together with access, servicing, parking and landscaping on a site of circa 1.498 hectares to the North of Solent Road, Havant.

The proposed development drawing is included in Appendix D.

5.1 Fluvial and Tidal Flooding

The proposed development work would not have any impact on the fluvial or tidal flooding once the flood alleviation works are complete.

Therefore, the risk of flooding from fluvial and tidal sources has therefore been assessed as low.

5.2 Surface Water Flooding and Proposed Drainage Strategy

Recommendation provided in Strategic Flood Risk Assessment for new developments is that surface water is restricted to Greenfield runoff rates where possible for new developments.

Equivalent GREENFIELD Site Peak Flows – ICP SUDS

The existing greenfield run-off for the original site has been calculated using ICP SUDS. This is based on the IH 124 method which is suitable for all catchments up to 200ha. For catchments smaller than 50ha the equivalent runoff from a 50ha site must be calculated using IH124, it is then possible to pro-rata this value to give the peak run-off for the smaller site. ICP SUDS calculation automatically carries out the pro rata conversion reducing the possibility of human error.

Taking into account the sites characteristics SAAR 725, soil figure of 0.4 and area of 1.498ha the Greenfield run-off rate has been calculated for the site at 5.3 l/s (rural)

Calculations can be seen in Appendix F.

As mentioned under section 3.2 the existing site geology consists of a variable thickness of topsoil and Made Ground, which is in turn underlain by superficial deposits comprising of Alluvium. A high groundwater levels has also been recorded. Infiltration will therefore not be possible at this site and the initial design provided as part of this report has therefore allowed for no infiltration.

The surface water drainage network for the proposed development is in line with the principles of integrated Construction Industry Research and Information Association (CIRIA) Sustainable Drainage System SuDS and source control methods to convey surface water runoff flows from the site as well as national and local standard.

• Runoff from the site to be restricted at the Greenfield rate of 5.3L/s for all the events from 1 in 1 year to 1 in 100 year return periods, including climate change allowances; • Appropriate attenuation to be provided onsite; • The onsite surface water drainage design will follow the principles listed in the Approved Document Part H of the Building Regulations and Sewers for Adoption 7th Edition. The Building Regulations established a hierarchy for surface water disposal which encourages a SuDS approach; • No surcharge for the 1:1year rainfall event except for the outfall pipe which may surcharge due to restriction

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

• Onsite surface water sewers shall be designed to a 1 in 30 year no flooding standard in accordance with BS EN 752: 2017. There will be no flooding of buildings or off-site areas during a 1 in 100- year return period storm event including climate change allowance; • Any onsite flooding in the 1:100+20% event, will be directed into a safe place or mitigation measures to be provided on site for any flooding over 5m3. The proposed drainage network and attenuation requirements are modelled using industry standard hydraulic modelling software and included in Appendix F. The controlled discharge will be to either the existing private onsite surface water drainage crossing the site or via a new headwall to the adjoining watercourse, Appendix E.

Therefore, the risk of surface water flooding from the proposed development will remain low.

Assessment of Surface Water Management Options

For sustainable management of surface water run-off from a new development, the use of SuDS is recommended. Table 6 provides a comparison of the different kinds of SuDS systems and their suitability for use at the development site.

5.3 Water Quality

Table 26.2 of the CIRIA C753 SuDS Manual identifies that the pollution hazard level associated with the land uses within the Proposed Development as being ‘Medium’. On a scale from 0 – 1, ‘Commercial Yard & delivery areas’ are deemed to have the following pollution hazard indices:

• Total suspended solids = 0.7

• Metals = 0.6

• Hydrocarbons = 0.7

The SuDS Manual confirms that in England and Wales, where the destination of runoff is to a watercourse then surface water indices should be used for the surface water discharge (Table 26.3 of The SuDS Manual).

The proposed surface water drainage strategy discharges via a new headwall into a watercourse. Therefore, the use of the surface water indices approach is deemed to be appropriate.

In terms of pollution control the car parking for the Portsmouth Water office building discharges via porous paving prior to connecting to the new drainage system. The industrial unit’s commercial yard and delivery areas are to be protected by Class 1 bypass petrol interceptor. The pollution mitigation assessment is summarised in Tables 5 below. The pollution removal characteristics of the pollution control features are based on data in CIRIA C753 and data provided by the product manufacturers.

Table 5: Pollution Mitigation Assessment for the site

Total Type of SuDS component suspended Metals Hydrocarbons solids (TSS)

Class 1 Bypass Petrol Interceptor 0.4* 0.6* 0.8* (Kingspan or similar)

Total 0.4 0.6 0.8

*subject to manufactures details

The results in Table 5 show that there is a minor residual impact associated with the Total Suspended Solids. However, whilst Pollution Mitigation Index data is not provided in CIRIA C753 for gullies/catch pit manholes, it is anticipated that sumps at the base of the gullies and catch pits will provide a positive improvement that would mitigate the residual impact for the Total Suspended Solids.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Table 6: Assessment of Suitability of SuDS at the site as the drainage hierarchy

SUDS Group Technique Image Description Advantages Disadvantages Suitable for Use at Site Retention Balancing Pond Provides both storm water Good removal of No reduction in run- attenuation and treatment. Run- pollutants, can be used off volume, land take Not suitable for the type off from each rain event is where groundwater is may limit use in high of development detained and treated in the pool. vulnerable, good density sites. The retention time promotes community pollutant removal through acceptability, high sedimentation. ecological, and amenity benefits. Sub-surface Oversized pipes, tank systems Modular and flexible, No water quality ✓ Storage and modular geocellular systems dual usage treatment. Sub-surface storage is that can be used to create a below (infiltration/storage, recommended. ground storage structure. high void ratios), can be installed beneath trafficked and soft landscaped areas. Wetland Shallow wetland Wetlands provide storm water Good pollutant removal Land take is high, Extended attenuation and treatment. They and if lined can be used requires base flow, Wetlands are not detention wetland comprise shallow ponds and where groundwater I little reduction in run- possible due to the high Pond wetland marshy areas, covered in aquatic vulnerable. Good off volume, not land take required Pocket wetland vegetation. Wetlands detail flows community suitable for steep for an extended period to allow acceptability, ecological sites. Submerged gravel sediments to settle and to remove and amenity benefits. wetland contaminants. They can provide Wetland channel significant ecological benefits. Infiltration Infiltration trench Surface water run-off can be Reduces the volume of Requires appropriate discharged directly to ground for run-off, effective at pre-treatment, basins Infiltration unlikely with infiltration by soakaways, basins, pollutant removal, require a large flat the alluvium soils and Infiltration basin or trenches. A prerequisite is that contributes to area, offset from high-water table

both groundwater and ground groundwater recharge, foundations. identified on site. Soakaway conditions are appropriate to simple and cost- receive the quality and quantity of effective, easy water generated. performance observation.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

SUDS Group Technique Image Description Advantages Disadvantages Suitable for Use at Site Porous paving Block or porous paving allows run- Reduces the volume of Not suitable for ✓ off to infiltrate through to subbase run-off and if designed heavily trafficked Porous paving to the layer. Water can then be for infiltration areas or adoptable car parking areas has infiltrated into ground or conveyed contributes towards roads. Requires been proposed. Permeable paving into storage or drainage systems. groundwater recharge. regular sweeping to East to install and prevent clogging with retrofit. Simple to dirt. manage. If lined can be used where groundwater is sensitive. Filtration Surface sand filter Structures designed to treat Flexibility of design, Not for high sediment surface water run-off through efficient in removing content, detention There is no requirement filtration using a sand bed filter pollutants, suitable for times can support for high pollution Sub-surface sand medium. The filters can be retrofits and in tightly algae growth, reduction at this site filter designed with or without constrained urban minimum hydraulic Perimeter sand infiltration. Temporary storage of locations. head of 1.2m filter run-off is achieved through required, possible ponding above the filter layer. odour problems, high They are used where particularly capital and high pollutant removal is required. maintenance cost. Bioretention/filter Vegetated strips of land designed Landscaping features, Requires landscaping swale to accept run-off as overland effective in removing and management, No requirement for high sheet flow between a hard- pollutants, flexible large land required, pollution reduction; surfaced area and a receiving layout to fit into not suitable for steep large land areas not system. landscape, suited for sites; no significant available. highly impervious attenuation or areas, good retrofit, reduction of flows. capability, effective pre- treatment option. Filter trench/drain Shallow excavations filled with Hydraulic benefits High clogging rubble or stone that create achieved with filter potential without Not feasible for the temporary subsurface storage for trenches, trenches can effective pre- proposed development filtration of storm water run-off. be incorporated into treatment, limited to site landscaping and fit small catchments,

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

SUDS Group Technique Image Description Advantages Disadvantages Suitable for Use at Site Receive lateral inflow from an well beside roads and high cost of replacing adjacent impermeable surface. car parks. filter material. Detention Detention basin Surface storage basins that Cater for a wide range Land take, little provide flow control through of rainfall events, can reduction in run-off Not suitable and not attenuation. Normally dry and in be used where volume, detention required for this site certain situations the land may groundwater is depths constrained by also function as a recreational vulnerable, potential for levels.

facility dual land use, easy to maintain. Enhanced dry Swales are linear vegetated Incorporate into Not suitable for steep swale drainage features in which surface landscaping, good areas, significant land Not suitable and not water can be stored or conveyed. removal of pollutants, take, not suitable in required for this site They can be designed to allow reduces run-off rates areas with roadside infiltration, where appropriate. and volumes, low cost. parking. Enhanced wet swale Conveyance Conveyance Formal linear drainage features in Negate the need for Potential trip/wheel swales which surface water can be stored underground pipework. hazard, disable Not suitable and not or conveyed. They can be Can provide some access issues. required for this site Rills incorporated with water features attenuation. Possible such as ponds or waterfalls where reduction in run-off appropriate. volume via plant uptake and infiltration. Source Green/brown roof Multi-layered system that covers Mimics greenfield state Additional weight, not control the roof of a building with of building footprint for appropriate for steep Not suitable for the vegetation cover/landscaping over high density roofs, maintenance of proposed structure at a drainage layer. Designed to developments, good roof vegetation. this site intercept and retain precipitation, removal of pollutants, reducing the volume of run-off and ecological benefits, attenuating peak flows. insulates buildings, sound absorption.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

5.3.1 Maintenance of SuDS

The on-site drainage will be managed by the site management company who will be responsible to maintain any on-site services including drainage. The off-site private drainage is managed by a management company managing the business park. Table 7: Management and Maintenance Strategy

Drainage Feature Regular Maintenance Occasional/Remedial Maintenance Monitoring Drainage • Inspections will include gratings; covers including • Channel/Slot cleaning will be by flushing with • Inspect every 4 months channels/Gullies their locking bolts; sumps and sump buckets; water or high-pressure jetting (no boiling water or after large storm. exposed concrete surround and adjacent or cleaning agent will be used). All silt buckets surfacing. and sumps will be cleaned out replaced back • Check for accumulation of debris and silt and into the units ensuring they are correctly fitted. cleaned as necessary • All channel surfaces and joints will be checked • Gratings, frames and all associated locking parts and repaired as necessary. to be checked for damage. • Repair/rehabilitation of inlets, outlet, as required. • Exposed concrete and adjacent surfacing to be checked for cracking and general damage. • Check condition of inlet and outlet pipes, flow controls, baffles and isolation structures Manholes/Inspecti • Check for accumulation of debris and silt and • Clean as necessary. • Inspect every 6 months on Chambers clean as necessary. • All manhole and inspection chamber covers and or after large storm. • Covers and frames to be checked for damage. frames to be replaced as necessary. • Exposed concrete and adjacent surfacing to be • Repair exposed concrete and surfacing as checked for cracking and general damage. necessary • Check condition of inlet and outlet pipes, flap • Repair/rehabilitation of inlets, outlet, overflows valves, baffles etc. and vents, as required. Attenuation Tank • Check for accumulation of debris and silt and • Clean as necessary. • Inspect every 6 months clean as necessary. • Repair/rehabilitation of inlets and outlet, as or after large storm. • Check condition of inlet and outlet pipes and required. ventilation structures Pumping Station • Check for accumulation of debris and silt and • Clean as necessary. • Inspect every 6 months clean as necessary. • Repair/rehabilitation of inlets and outlet, as or after large storm. • Check condition of inlet and outlet pipes and required. ventilation structures

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

5.4 Sewer Flooding

The site will form a new foul water connection point to the public Southern Water manhole formed on the diverted public sewer crossing the site. The peak discharge rate from the industrial development will be minimal and have limited impact on wider infrastructure.

Therefore, the risk of sewer flooding to the site post development work would remain unchanged.

5.5 Groundwater Flooding

The proposed development is likely to be constructed using CMC piled foundations and unlikely to impact the groundwater below the site.

Therefore, the risk from groundwater flooding will be remain as low.

5.6 Artificial Sources of Flooding

The proposed development work will not have an impact on artificial sources of flood risk.

5.7 Summary of Flood Risk from the Proposed Development

The flood risk to and from the proposed development has been assessed to remain low from all sources.

The flood risk to the development is summarised in Table 8.

Table 8: Summary of flood risk to the development

Type of Flooding Source of Flooding Flood Risk Proposed Mitigation

Flood alleviation works underway Environmental Fluvial and Tidal Brockhampton Stream Low Permit licence number EPR/PB3294JJ

Discharge into the private surface water network or Surface Water Runoff from the site and surrounding land Low watercourse at a restricted Greenfield runoff rate and onsite attenuation.

Diversion and discharge into Sewers Surrounding public foul drainage systems Low the existing drainage network

Underlying geology and groundwater Ground Water Low Development levels raised. levels

Artificial Sources none Not applicable

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

6. Conclusion

The existing flood risk to the development area from all sources has been assessed from a review of all available data. Future climate change has also been considered. Using the proposed development plan, the extent of the flood risk has been determined for the site as well as the effect that the development might have on flood risk elsewhere.

The assessment can be summarised as follows:

• The Strategic Flood Risk Assessment (Local Plan Sites) completed in November 2018 for this site (Land North of Solent Road – Site Ref: HB36), has shown this site is suitable for commercial use.

• Portsmouth Water along with their consultant Ardent are undertaking flood alleviation works to the adjoining watercourse. This work is being undertaken under Environmental Permit licence number EPR/PB3294JJ. The site will remain flood free during the 1 in 100 year plus climate change scenario and provide necessary flood alleviation to address concerns raised in the SFRA.

• Following completion of flood alleviation works the site will be located in Flood Zone 1. • The site is at low risk of flooding from all sources.

• The proposed development is classified as ‘Less Vulnerable’ and suitable for this location. • The proposed development work would not increase the risk of flooding from any sources; • A drainage strategy is proposed in consideration with the local and national standard and would not increase the flood risk;

• Recommendation provided in the Strategic Flood Risk Assessment for new developments is that surface water runoff is restricted to Greenfield runoff rate. ICP SUDS Greenfield calculation has been undertaken giving a discharge rate of 5.3L/s for the 1.49ha site which has been adopted for this site.

• The development site has a high-water table which limits the use of infiltration systems on site. The proposal includes SuDS measure in the form of attenuation tank and porous paving for parking areas.

• In conclusion, the proposed development work will not increase the risk of flooding to the site or surrounding areas in accordance with the provisions of relevant national and local planning policies.

Prepared for: Chancerygate (Erdington) Limited

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix A Ardent flood modelling + EA permit (EPR/PB3294JJ)

Prepared for: Chancerygate (Erdington) Limited

The Environmental Permitting (England & Wales) Regulations 2016

Portsmouth Water Limited

The removal of a 2.5m length of 450mm diameter cast iron culvert and associated groundworks on the Brockhampton Stream

National Grid Reference[s]: SU7115206195

Located on the Brockhampton Stream approximately 120m south of the Portsmouth Water ltd. compound at West Street, Havant, PO9 1LG and approximately 420m south west from the bifurcation of the Brockhampton Stream from the Lavant Stream.

Permit number EPR/PB3294JJ

Permit number EPR/PB3294JJ 1 Introductory note

This introductory note does not form a part of the permit

The main features of the permit are as follows. Flood risk activity comprising of the removal of in-channel structures, namely the removal of a 2.5m length of 450mm diameter cast iron culvert and associated groundworks on the Brockhampton Stream. The status log of the permit does not form part of the permit. It sets out the permitting history, including changes to the permit or permit reference number.

Status log of the permit Description Date Comments Application EPR/PB3294JJ Duly made Application for the removal of a 2.5m length of 11 450mm diameter cast iron culvert on the November Brockhampton Stream 2020 Permit determined EPR/PB3294JJ 14 January Permit issued to Portsmouth Water Limited 2021 End of introductory note

Permit number EPR/PB3294JJ 2 Permit

The Environmental Permitting (England and Wales) Regulations 2016 Permit number EPR/PB3294JJ The Environment Agency hereby authorises, under regulation 13 of the Environmental Permitting (England and Wales) Regulations 2016 Portsmouth Water Limited whose registered office is Po Box No8 West Street Havant Hampshire PO9 1LG company registration number [02536455] to operate the following flood risk activities: The removal of in-channel structures, namely the removal of a 2.5m length of 450mm diameter cast iron culvert and associated groundworks on the Brockhampton Stream. at the Brockhampton Stream approximately 120m south of the Portsmouth Water ltd. compound at West Street, Havant, PO9 1LG and approximately 420m south west from the bifurcation of the Brockhampton Stream from the Lavant Stream.

National Grid Reference(s) SU7115206195 to the extent authorised by and subject to the conditions of this permit.

Name Date

14/01/2021

Wesley Jones Partnership and Strategic Overview Team Leader East Hampshire and Isle of Wight Solent and South Downs

Authorised on behalf of the Environment Agency

Permit number EPR/PB3294JJ 3 Conditions

1 Management

1.1 General management

1.1.1 The operator shall manage and operate the activities: (a) in accordance with a written management system that identifies and minimises risks of flooding, impact on drainage and environmental harm so far as is reasonably practicable, including those risks arising from operations, maintenance, accidents, incidents, non-conformances and those drawn to the attention of the operator as a result of complaints; and (b) using sufficient competent persons and resources. 1.1.2 Records demonstrating compliance with condition 1.1.1 shall be maintained. 1.1.3 Any person having duties that are or may be affected by the matters set out in this permit shall have convenient access to a copy of the permit.

2 Operations

2.1 Permitted activities

2.1.1 The operator is only authorised to carry out the activities specified in schedule 1 table S1.1 (the

2.2 The site

2.2.1 The activities shall not extend beyond the site, being the land shown edged in blue on the site plan at schedule 2 to this permit and showing National Grid Reference SU7115206195.

2.3 Operating techniques

2.3.1 The operator shall use appropriate measures, including but not limited to those in the approved Method of Work. (a) to minimise sediment mobilisation (b) to minimise impact on biodiversity (c) to ensure there is no increase to flood risk or detrimental impact on drainage; (d) for the storage and disposal or waste produced; and (e) to prevent and minimise environmental harm. 2.3.2 All liquids in containers, whose emission to water or land could cause pollution, shall be provided with secondary containment, unless the operator has used other appropriate measures to prevent or where that is not practicable, to minimise, leakage and spillage from the primary container. 2.3.3 Measures shall be taken to ensure that the activities do not cause the spread of invasive non-native species or plant or animal diseases. 2.3.4 No vegetation clearance or site clearance shall be take place during nesting season (1 March-31 July inclusive each year). 2.3.5 No works shall take place until a fish screen (maximum 2mm mesh spacing) is installed on the pump or a fish friendly pump is used to prevent the entrapment, entrainment or impingement of fish and eel

Permit number EPR/PB3294JJ 4 (including elver) during over pumping. The fish/eel screen shall be maintained in accordance with the man records kept of such maintenance available for inspection by the Environment Agency. 2.3.6 The fish rescue will be undertaken in line with the methodology provided by Pisces Conservation Ltd. dated 15 Dec 2020. Records of species caught to be provided to the Environment Agency within 1 month of capture. 2.3.7 Nothing shall be done or permitted to occur during the works which would materially reduce the capacity of the floodplain. 2.3.8 The operator shall sign up to receive flood warnings from the Environment Agency. Upon receipt of the warning the works shall cease and temporary works removed as directed by the Environment Agency. An emergency 24 hour contact has been supplied in case of any flood warnings: - Portsmouth Water Operations Centre: 02392449091 2.3.9 The activities shall, subject to the conditions of this permit, be operated using the techniques and in the manner described in the documentation specified in schedule 1, table S1.2, unless otherwise agreed in writing by the Environment Agency.

3 Information

3.1 Records

3.1.1 All records required to be made by this permit shall: (a) be legible; (b) be made as soon as reasonably practicable; (c) if amended, be amended in such a way that the original and any subsequent amendments remain legible, or are capable of retrieval; and (d) be retained, unless otherwise agreed in writing by the Environment Agency, for at least 6 years from the date when the records were made 3.1.2 The operator shall keep on site all records, plans and the management system required to be maintained by this permit, unless otherwise agreed in writing by the Environment Agency.

3.2 Reporting

3.2.1 The operator shall send all reports and notifications required by the permit to the Environment Agency using the contact details supplied in writing by the Environment Agency.

3.3 Notifications

3.3.1 The Environment Agency shall be notified no less than 7 days before the commencement of the activities. 3.3.2 The Environment Agency shall be notified no less than 7 days after the activities are completed. 3.3.3 The Environment Agency shall be notified without delay following the detection of any breach of a limit specified in the permit or any significant environmental effects resulting from the activities or of any breach of the permit. 3.3.4 Written confirmation of actual or potential incidents or effects and breaches referred to in 3.3.3 shall be submitted within 24 hours. 3.3.5 The Environment Agency shall be notified within 14 days of the occurrence of the following matters, except where such disclosure is prohibited by Stock Exchange rules:

Permit number EPR/PB3294JJ 5 Where the operator is a registered company: (a) (b) any steps taken with a view to the operator going into administration, entering into a company voluntary arrangement or being wound up. Where the operator is a corporate body other than a registered company: (a) (b) any steps taken with a view to the dissolution of the operator. In any other case: (a) the death of any of the named operators (where the operator consists of more than one named individual); (b) (c) any steps taken with a view to the operator, or any one of them, going into bankruptcy, entering into a composition or arrangement with creditors, or, in the case of them being in a partnership, dissolving the partnership. 3.3.6 Where the operator proposes to make a change in the nature or functioning, or an extension of the activities, which may have consequences for flood risk, drainage or the environment and the change is not otherwise the subject of an application for approval under the Regulations or this permit: (a) the Environment Agency shall be notified at least 14 days before making the change; and (b) the notification shall contain a description of the proposed change in operation.

3.4 Interpretation

3.4.1 In this permit the expressions listed in schedule 3 shall have the meaning given in that schedule. 3.4.2 In this permit references to reports and notifications mean written reports and notifications, except

by telephone. 3.4.3 Any reference to a distance of a number of metres from a flood defence structure, drainage work, remote defence or sea defence is a reference to that distance as measured from the foot of the foregoing as the case may be. 3.4.4 Any reference to a distance of a number of metres from a river control work is a reference to that distance as measured from the nearest part of the river control work. 3.4.5 Any reference to a distance of a number of metres from a watercourse is a reference to that distance as measured horizontally from the foot of the bank on the landward side of the watercourse

Permit number EPR/PB3294JJ 6 Schedule 1 Operations

Table S1.1 activities Activity Description of Limits of activities reference activities Permanent Works P1 The removal of in- The activity shall be commenced within 3 years of the date of the channel structures, grant of the permit and completed within 4 months of namely the removal commencement. of a 2.5m length of 450mm diameter The activities shall be carried out in accordance with the cast iron culvert and application form dated 04 November 2019 associated groundworks on the and Brockhampton Stream. Removal of 2.5m x 450mm Cast iron pipe work from stream and re-instate stream to natural habitat.

and

Risk Assessment with Reference RA- 01 dated 01/10/2019 Authored by Steve Brown

and

Flood Risk Assessment Culvert Removal 191920-07 and dated July 2020 authored by Ardent Consulting Engineers.

and

Plan and cross- 191921-002 revision A and dated October 2020.

and

Plan and cross- Proposed flood alleviation Earthworks 191921-003 revision A and dated October 2020.

and

Schedule 5 Notice Solent Road Simon Deacon.

and

Method statement electric fishing at Lavant stream, Havant Pices Conservation Ltd.

The activities shall only be carried out on the Brockhampton Stream main river.

Permit number EPR/PB3294JJ 7 Table S1.2 Operating techniques Date Requirement Measures (if measures are specified) Document reference Received Method Statement with Subject

Condition Approved Method of Work Cast iron pipe work from stream 04/11/2019 2.3.1 and re-instate stream to natural

Brown and dated 06/09/2019. No vegetation clearance or site clearance Email with Reference: Condition shall be take place during nesting season 13/01/2021 2.3.4 (1 March-31 July inclusive each year). Fish Rescue Plan titled No works shall take place until a fish electric screen (maximum 2mm mesh spacing) is 21/12/2020 fishing at Lavant stream, installed on the pump or a fish friendly d 15/12/2020 and pump is used to prevent the entrapment, produced by Pices entrainment or impingement of fish and Condition Conservation Ltd. eel (including elver) during over pumping. 2.3.5 The fish/eel screen shall be maintained in And

specifications and records kept of such Email with Reference: maintenance available for inspection by 13/01/2021 the Environment Agency.

Fish Rescue Plan titled electric 21/12/2020 fishing at Lavant stream, The fish rescue will be undertaken in line with the methodology provided by Pisces produced by Pices Condition Conservation Ltd. dated 15 Dec 2020. Conservation Ltd. 2.3.6 Records of species caught to be provided to the Environment Agency within 1 month And of capture. Email with Reference: 294JJ Confirmation 13/01/2021 of Conditions Plan and cross-sectional

alleviation

number 191921-003 revision A 21/12/2020 and dated October 2020.

And

Email with Reference: Nothing shall be done or permitted to Condition occur during the works which would 13/01/2021 2.3.7 materially reduce the capacity of the floodplain. And

Flood Risk Assessment titled Flood Risk Assessment Culvert Removal reference number 191920-07 22/07/2020 and dated July 2020 authored by Ardent Consulting Engineers.

Permit number EPR/PB3294JJ 8 Table S1.2 Operating techniques Date Requirement Measures (if measures are specified) Document reference Received The operator shall sign up to receive flood warnings from the Environment Agency. Upon receipt of the warning the works shall cease and temporary works removed Email with Reference: Condition as directed by the Environment Agency. 13/01/2021 2.3.8 of Conditions An emergency 24 hour contact has been supplied in case of any flood warnings: - Portsmouth Water Operations Centre: 02392449091

Permit number EPR/PB3294JJ 9 Schedule 2 Site Plan

Permit number EPR/PB3294JJ 10

Schedule 3 Interpretation

operator as part of the application and any response to a notice served under Schedule 5 to the EP Regulations. ed by the Environment Agency under section 108(1) of The Environment Act 1995 to exercise, in accordance with the terms of any such authorisation, any power specified in section 108(4) of that Act. and and Wales) Regulations SI 2016 No.1154 and words and expressions used in this permit which are also used in the Regulations have the same meanings as in those Regulations. er on the statutory main river map held by the Environment Agency. working methods for carrying out the activity and what measures will be taken to avoid or minimise the risks of environmental effects.

(a) flooding or risk of flooding; (b) harm to the environment or risk of harm to the environment; and (c) detrimental impact on drainage or risk of detrimental impact on drainage.

(a) cause harm to the conservation, protection and enhancement of any species and habitat s designated under any enactment as having special protection or priority; (b) prevent the achievement of environmental objectives within the meaning of the Water Framework Directive 2000/60/EC; (c) cause pollution; or (d) otherwise adversely affect the protection and enhancement of the environment.

END OF PERMIT

Permit number EPR/PB3294JJ 11

PORTSMOUTH WATER

WARD SOLENT ROAD HOMES

FLOOD RISK ASSESSMENT – CULVERT REMOVAL (Flood Risk Activities Permit Application)

Report Ref NO. 191920-07 Project No. 191920 JULY 2020

PORTSMOUTH WATER

SOLENT ROAD

FLOOD RISK ASSESSMENT – CULVERT REMOVAL (Flood Risk Activities Permit Application)

Ardent Consulting Engineers 3rd Floor The Hallmark Building 52-56 Leadenhall Street LONDON EC3M 5JE Tel: 020 7680 4088 Fax: 020 7488 3736 [email protected]

REPORT REF NO. 191920-07 PROJECT NO. 191920 JULY 2020 SOLENT ROAD 191920-07

FLOOD RISK ASSESSMENT – CULVERT REMOVAL JULY 2020

CONTENTS Page

1. INTRODUCTION 1

2. SITE DESCRIPTION 3 Site Location 3 Waterbodies in the Vicinity of the Site 3 Existing Development 5 Topography 5 Ground Conditions 6

3. BASELINE FLOOD RISK 8 Flood Zone Designation 8 Environment Agency Flood Map for Planning 8 Hydraulic Model Build 9 Hydrology 10 Data sources 12 Baseline Modelling Results 15 Mitigation Modelling 18 Mitigation Model Results 19 Sensitivity Testing 20

4. CONCLUSIONS 23

JE/191920/Reports/191920-07 (i) SOLENT ROAD 191920-07

FLOOD RISK ASSESSMENT – CULVERT REMOVAL JULY 2020

FIGURES Figure 2-1: Site location plan...... 3 Figure 2-2: Waterbodies in the vicinity of the site ...... 5 Figure 2-3: 1m resolution LiDAR data ...... 6 Figure 2-4: British Geological Survey data ...... 7 Figure 4-1: EA Flood Map for Planning (Rivers and Sea) ...... 9 Figure 4-2: Penstock control structure downstream of Lavant Link Pipe ... 14 Figure 4-3: 1 in 100 year plus 45% climate change baseline scenario maximum flood depth ...... 16 Figure 4-4: 2.0 m high wall curtailing western boundary of the Site ...... 17 Figure 4-5: 1 in 100 year plus 45% climate change, mitigation scenario maximum flood depths ...... 19 Figure 4-6: Comparison of baseline vs climate change hydrograph ...... 22

TABLES Table 4-1: Manning's 'n' values for 2D domain 15

JE/191920/Reports/191920-07 (ii) SOLENT ROAD 191920-07

FLOOD RISK ASSESSMENT – CULVERT REMOVAL JULY 2020

APPENDICES Appendix A EA PSO Team Modelling Methodology Approval Appendix B Hydrology Report Appendix C Hydraulic Model Extents Appendix D EA Lavant Link Pipe Consultation Appendix E Baseline Modelling Results Appendix F Proposed Mitigation Works Appendix G Mitigation Modelling Results Appendix H Sensitivity Modelling Results

JE/191920/Reports/191920-07 (iii) SOLENT ROAD 191920-07

FLOOD RISK ASSESSMENT – CULVERT REMOVAL JULY 2020

DOCUMENT CONTROL SHEET

REV ISSUE PURPOSE AUTHOR CHECKED APPROVED DATE

- Final JE JE BC 22-07-20

JE/191920/Reports/191920-07 (iv) SOLENT ROAD 191920-07

Flood Risk Assessment JULY 2020

1. INTRODUCTION

1.1. Ardent Consulting Engineers (hereafter referred to as “Ardent”) has been commissioned by Portsmouth Water to undertake Flood Risk Assessment (FRA) in support of a Flood Risk Activities Permit (FRAP) application to the Environment Agency (EA) in order to facilitate the removal of a small culvert on the Lavant Stream where it flows through the centre of a proposed development site located on Portsmouth Water owned land at Solent Road, Havant (hereafter referred to as ‘the site’).

1.2. Ardent have undertaken a hydraulic modelling study of the watercourse in order to assess the risk of flooding to the development site. The conclusion of the modelling study identified that the site is at risk of flooding during the 1 in 100 year event however this is due in large part due to the throttling effect of a 600 mm dia culvert on the Lavant Stream that acts as the main hydraulic control along this reach resulting in out of bank flows and a shallow flow path being formed across the site. Consequently, it has been proposed that by removing the culvert the risk of flooding to the site can be mitigated. Ardent have carried out modelling runs with the culvert removed to demonstrate this. An interim hydraulic modelling note (report ref 191920-03) was submitted to the EA Partnership and Strategic Overview (PSO) team as part of a Flood Risk Activities Permit application to remove the culvert and demonstrate that the modelling methodology was sound and that removal of the culvert did not result in an increase in flood risk offsite.

1.3. As part of the FRAP review process the EA have provided several iterations of comments and Ardent have responded accordingly to answer these queries. The outcome of which is that on the 26th June 2020 the EA confirmed that the hydraulic model was fit for the purpose of the FRAP application (refer to Appendix A). However, the EA also requested that a Flood Risk Assessment (FFRA) was prepared to appraise the baseline flood risk and determine the risk of flooding both on and off site as a result of the culvert removal.

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1.4. This FRA has been prepared to specifically address the EA’s request and satisfy the requirements of the FRAP application. The scope is therefore limited and is not intended to support any proposed planning application.

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2. SITE DESCRIPTION

Site Location

2.1. The Site is approximately 1.6 ha and is centred at Ordnance Survey grid reference SU 71106 06165 on Solent Road, Havant with the nearest post code being PO9 1LX. The Site is located within Portsmouth Water owned land to the rear of Portsmouth Water headquarters at West Street, Havant, PO9 1LG. The Lavant Stream (EA ‘main river’) flows through the centre of the Portsmouth Water owned land and marks the boundary along the northern edge of the site. Refer to Figure 2-1 below for site Location Plan.

Legend West Street Portsmouth Water owned land Site outline

Portsmouth Water Headquarters

Lavant Stream

Solent Road

Figure 2-1: Site location plan

Waterbodies in the Vicinity of the Site 2.2. There are several waterbodies within the vicinity of the site (refer to Figure 2-2). The Lavant Stream flows from east to west along the northern boundary of the Site and southwards along the western boundary. The Lavant Stream is classified as ‘main river’. The upper catchment of the Lavant Stream is situated on chalk bedrock before flowing through the urban area of Havant through multiple culverted sections. The channel is artificially diverged approximately 400 m

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upstream of the Site for the creation of a flood bypass channel which flows southwards through the urban area.

2.3. The Site lies adjacent to a boundary between permeable chalk bedrock an impermeable London Clay Formation to the north. Consequently, several springs are present in the area including the Brockhampton Springs on the Portsmouth Water site which give rise to the two ponds to the north of the site. A spring is also present in the south west corner of the Portsmouth Water owned land which joins the Lavant Stream adjacent to Solent Road. Also adjacent to the south of the development site are two ditches in open and culverted section which are understood to be fed by the urban drainage network to the east and north. These are understood to discharge into the Lavant Stream south of the site.

2.4. Approximately 350 m to the north west of the Site, the Hermitage Stream flows from north to south. A flood relief culvert is present on the Lavant Stream approximately 1.5 km upstream of the Site which is designed to transfer flows from the Lavant Stream catchment into the Hermitage Stream during extreme rainfall events. Both the Hermitage Stream and the Lavant Stream discharge to the estuary approximately 1.0 km to the south of the Site.

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Legend Development site outline

Hermitage Stream Lavant Stream Brockhampton Springs

Bypass channel Lavant Stream

Ditches

Figure 2-2: Waterbodies in the vicinity of the site

Existing Development

2.5. The existing site is currently formed of undeveloped Greenfield land with the exception of a disused former tennis court in the western part of the Site.

Topography

2.6. Ardent have obtained EA 1 metre resolution LiDAR data of the study area. The LiDAR data shows that elevations on the site fall from approximately 5.8 m AOD in the north west corner of the Site adjacent to the Lavant Stream down to 4.8 m AOD in the south western corner (refer to Figure 2-3 below). This is a gradient of approximately 1:120.

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Legend Elevation (m AOD)

Lavant Stream

Solent Road

Figure 2-3: 1m resolution LiDAR data

Ground Conditions

2.7. As mentioned in Section 2.2 above, the geology of the local area is quite complex. British Geological Survey data (refer to Figure 2-4) shows that the Site is located on permeable chalk geology with impermeable London Clay Formation bedrock to the north. This change in permeability results in the emergence of several springs in the vicinity of the Site.

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Legend Chalk Formation Lambeth Group - Clay, Silt And Sand London Clay Formation - Clay, Silt And Sand Bognor Sand Member - Sand London Clay Formation - Sand

The Site

Figure 2-4: British Geological Survey data

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3. BASELINE FLOOD RISK

Flood Zone Designation

3.1. Flood Zones refer to the probability of river and sea flooding, ignoring the presence of defences. The National Planning Policy Framework (NPPF) Planning Practice Guidance defines Flood Zones as follows:

• Flood Zone 1: Low Probability. Land having a less than 1 in 1,000 annual probability of river or sea flooding.

• Flood Zone 2: Medium Probability. Land having between a 1 in 100 and 1 in 1,000 annual probability of river flooding; or Land having between a 1 in 200 and 1 in 1,000 annual probability of sea flooding.

• Flood Zone 3a: High Probability. Land having a 1 in 100 or greater annual probability of river flooding; or Land having a 1 in 200 or greater annual probability of sea flooding.

• Flood Zone 3b: The Functional Floodplain. This zone comprises land where water has to flow or be stored in times of flood. Local planning authorities should identify in their Strategic Flood Risk Assessments areas of functional floodplain and its boundaries accordingly, in agreement with the Environment Agency.

3.2. The Flood Zones are shown on the EA Flood Map for Planning (Rivers and Sea). The Planning Practice Guidance states that the Zones shown on the EA Flood Map do not take account of the possible impacts of climate change and consequent changes in the future probability of flooding.

Environment Agency Flood Map for Planning

3.3. According to the EA Flood Map for Planning (Figure 4-1) a large part of the site is located in land designated as Flood Zone 3 (high probability of fluvial flooding) and is shown as undefended. The north eastern corner is shown to be in Flood Zone 1 (low probability of flooding). However, the flood outlines have been derived from a hydraulic model constructed in 2008 using hydraulic modelling software InfoWorks CS and RS. Through consultation with the Environment Agency (EA) it became apparent that the hydrology associated with the model was outdated and would need revising and that also, several structures within the model were not accurately

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represented or were not included. Therefore, confidence in the modelling outputs and flood outlines was reduced but this represented the best available information. As part of the assessment of flood risk to the Site it was therefore decided to update the hydrology and make an assessment based on the latest climate change guidance and update the hydraulic model with new survey data.

Legend Flood Zone 3 Areas Benefiting from Defence Lavant Stream Flood Zone 2 Flood Zone 1 Flood Defence Main Rivers Flood Storage Area

Solent Road

Figure 4-1: EA Flood Map for Planning (Rivers and Sea)

Hydraulic Model Build

3.4. The original EA hydraulic model of the Lavant Stream was constructed in 2008 by Atkins using Infoworks CS and RS as part of the Havant Flood Mapping Study.

3.5. InfoWorks CS allows for modelling of the urban drainage network or sewer system. InfoWorks RS allows the modelling of the river network. These are legacy software packages and are no longer supported.

3.6. Therefore in order to adequately appraise flood risk to the Site it was decided to construct a dynamically linked 1D-2D model of the Lavant

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Stream and floodplain using FMP (1D) and Tuflow (2D) software packages based on new cross sectional channel survey data as well as utilising data, river sections and sewer sections taken from the original Infoworks models where appropriate.

Hydrology

Fluvial Inflows

3.7. As part of this study, the EA advised that the hydrology of the model would likely need updating to include more recent data and would also require an assessment of the latest climate change scenarios.

3.8. A hydrology report was prepared by consultant hydrologist Dr Paul Garrad and is included in Appendix B. The report identifies that the catchment of the Lavant Stream is divided into the upper, rural, chalk dominated catchment and the lower, urban, clay catchment (approximately 56 km² and 1.5 km² respectively) and that these two distinct catchments influence the hydrology of the system significantly.

3.9. Flows for the larger, predominantly rural, chalk catchment were derived using the Flood Estimation Handbook statistical method. Flows for the smaller, urban, clay catchment were derived using the ReFH method. Peak flows are included within the hydrology report in Appendix B.

3.10. The hydrology of the Lavant Stream is complex within the urban area of Havant. As with most urban catchments, runoff is contributed to the stream at multiple points along its reach from the surrounding urban sewer system and surface water network. The Lavant Stream is also characterised by the presence of several long culverts as it flows through the town centre. In addition, the main channel divides into two separate watercourses upstream of the Site adjacent to Park Road North. The bypass channel, as it’s known, flows south adjacent to Park Road South and towards the estuary. The other channel flows westwards and southwards in culverted section towards the Site where it is fed by a series of springs at a boundary between clay and

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chalk geology. At this location the Lavant Stream is sometimes referred to as “Brockhampton Springs”.

3.11. Upstream of the urban area, a flood relief culvert known as the Lavant Link Pipe is present. This structure is designed to transfer flows from the Lavant Stream to the neighbouring Hermitage Stream during peak flows.

3.12. Due to the complex nature of the urban hydrology outlined above, it was considered that it would not be appropriate to apply the urban hydrology to the model as a single inflow at the upstream of the model reach. Instead, the urban hydrology has been divided and applied incrementally along the urban reach based on the urban subcatchments as defined in the original EA Infoworks CS model.

3.13. In accordance with the EA’s latest guidance, an assessment of the impact of climate change has been taken into consideration by increasing fluvial and sewer flows as well as the tidal boundary levels. Suitable allowance for increased river flow due to climate change were considered based on the EA’s February 2016 guidance.

3.14. The current Site is located in the South East Region and is allocated for commercial development. The central allowance is therefore appropriate in this instance, however as a conservative assessment the higher central allowance has been used in this study i.e. the 1 in 100 year plus 45% event.

Tidal Boundary

3.15. The Tidal boundary was updated based on the East Solent Tidal Model built by JBA in July 2018. The model domain covering the area of interest is that of the Hayling Island model and the closest node to the Site of interest is BNDRY_5. The remaining nodes are located further east and south away from the Site of interest.

3.16. The 1 in 2 year climate change tidal curve was used in the model. The 2 year present day tidal peak level, according to the East Solent Modelling study undertaken by JBA in July 2018, is 2.91 m AOD.

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Guidance from the EA states1 that the anticipated rise in sea level for the south east of England up to the year 2115 is expected to be 1.21 m. Therefore, this value was used for the Climate Change adjustment. Based on the above the 2 year climate change tidal peak level is 4.11m AOD.

Data sources

1D Domain

3.17. The 1D model has been constructed using a mixture of different data sources.

3.18. The primary data source that has informed the 1D domain is channel survey cross sections collected by Terrain Geomatics in May 2019 of the Lavant Stream. The surveyed reach extends from Farringdon Road down to the estuary but did not include the Bypass Channel and also, due to access restrictions, did not include details of the Lavant Link Pipe.

3.19. The modelled reach was supplemented with data from the original EA InfoWorks RS model. Cross sectional data was extracted and incorporated to the FMP model extending the reach approximately 600 m upstream of Farringdon Road as well as at other selected locations.

3.20. Cross sections for the Bypass Channel adjacent to Park Road North were also extracted from the RS Model and incorporated into the FMP model. Details of the Lavant Link Pipe were extracted from the CS model. The total 1D model extent therefore extends from north of Bartons Road approximately 3.0 km upstream of the Site down towards the estuary 700 m downstream of the Site where the tidal boundary is applied. These extents are considered appropriate for the scope of the study. Full 1D and 2D model extents are provided in Appendix C.

1 https://www.gov.uk/guidance/flood-risk-assessments-climate-change- allowances#future-flood-risk-management

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3.21. Observations and measurements of additional structures and features were also made during a walkover of the Site and modelled reach.

3.22. Manning’s ‘n’ values have been applied to the 1D domain based on Manning’s ‘n’ for Channels from Chow, 1959 and a review of photographic data provided by the surveyor as well as observations made on Site. Where EA cross sections have been utilised the Manning’s ‘n’ values have only been adjusted where information to the contrary is available. For in channel, Manning’s ‘n’ values are typically in the range between 0.03-0.04 but are as low as 0.025 for some stretches of concrete lined channel and 0.015 for a short section of brick lined channel between nodes S31-S30. Manning’s ‘n’ values of between 0.025-0.035 have been adopted for concrete structures and culverts throughout the 1D domain. The values for the 1D domain are within the range of typical Manning's 'n' values for in channel and are industry standard practice. They are therefore considered to be appropriate to the study.

3.23. Further details regarding the control structure immediately downstream of the inlet to the Lavant Link Pipe at Crossland Drive were obtained through consultation with the EA (refer to Appendix D). The consultation established that a penstock is present downstream of the inlet which restricts flows during peak events and elevates the upstream water level. This enables flow to enter the Lavant Link Pipe which is subsequently transferred to the Hermitage Stream catchment to the west.

3.24. Due to access restrictions, the surveyors were unable to collect data of this structure directly. Therefore, the details supplied by the EA represent the best available information of this structure. The penstock was represented in the model using two orifice units with assumptions made on the dimensions of the structure based on the photograph provided by the EA in Figure 4-2 below.

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Figure 4-2: Penstock control structure downstream of Lavant Link Pipe

2D domain

3.25. The floodplain has been represented within the 2D domain of the model using LiDAR data. 1m resolution LiDAR data of the study area was obtained from the EA and incorporated into the hydraulic model. The hydraulic model has been run with a 2m cell size to represent the 2D domain. This provides sufficient resolution to accurately model flood flow paths whilst also ensuring model run times are not excessive.

3.26. OS OpenMap Local shapefile data was obtained from Ordnance Survey. This was then used to inform the ‘materials’ file within Tuflow. The ‘materials’ file allows for a Manning’s ‘n’ roughness value to be applied to the floodplain.

3.27. Together, the LiDAR data and ‘materials’ file allow for an accurate representation of over land flow paths throughout the 2D model domain.

3.28. Manning’s ‘n’ values for the 2D domain are presented in Table 4-1 below. These are within the range of typical Manning’s ‘n’ values for floodplain and are industry standard practice. They are therefore considered to be appropriate to the study.

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Table 4-1: Manning's 'n' values for 2D domain

Manning's Land use 'n' value Open Water 0.02 Roads/Tarmac 0.025 Default Grassed Areas / Car parks 0.035 Railway Tracks 0.04 Pasture / light vegetation 0.055 Urban areas/ Fenced Gardens 0.06 Dense vegetation / Wooded areas 0.08 Warehouse type Buildings 0.1 Masonry / Concrete Buildings 0.3 Stability Patch 0.9

Baseline Modelling Results

3.29. The Ardent baseline hydraulic model has been run for the following events:

• 1 in 100 year

• 1 in 100 year plus 45% climate change

• 1 in 1000 year

• 1 in 1000 year plus 45% climate change

3.30. The hydraulic model was run in the following software versions:

• Tuflow; 2018-03-AE-iDP-w64

• Flood Modeller Pro; 4.5.1

3.31. The model was run with a 1 second timestep for both the 1D and 2D domains. It is usual modelling practice to model the 1D domain with a timestep that is half that of the 2D domain if possible, however due to the inclusion of multiple structures in the urban reach a reduced 1D timestep was not possible due to instabilities.

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3.32. Model plots for all baseline events are included in Appendix E. Figure 4-3 below shows the maximum flood depths on Site during the 1 in 100 year plus 45% climate change baseline scenario overlain with the EA model flood extents for the 1 in 100 year plus 20% climate change scenario.

Legend Flood Depth (metres)

Figure 4-3: 1 in 100 year plus 45% climate change baseline scenario maximum flood depth

3.33. The EA flood outline covers the majority of the western and southern portions of the Site. However, the Ardent flood extent impacts the majority of the Site. The EA outline suggests that flood water is coming out of bank on the Lavant Stream on the western boundary of the Site as the watercourse flows southwards. However, analysis of aerial photography and site visits have confirmed that the presence of a 2.0 m high wall running the length of the channel at this location (Figure 4-4) prohibits any water from coming out of bank. Further interrogation of the EA model indicates that this wall has not been included within the model. The EA outputs are therefore misrepresentative.

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3.34. The EA were consulted regarding their modelled outputs who stated that the wall has not been included in their model as the Flood Map for Planning does not take into account the presence of flood defences (despite the wall not being a formal flood defence).

Figure 4-4: 2.0 m high wall curtailing western boundary of the Site

3.35. In the Ardent outputs, the 2.0 m wall is included which prevents any out of bank flow occurring at this location. The Site however becomes flooded as a result of the limiting capacity of a 600 mm diameter culvert on the northern boundary of the Site. This constriction results in water levels becoming elevated upstream of the culvert and spilling over the left bank of the watercourse. This forms a shallow flow path across the Site (less than 100 mm depth) with water propagating westward. Water is unable to re-enter the watercourse in the Ardent model as the 2.0 m high wall is included. Instead, flood water flows south where a drainage ditch is present along the southern boundary of the Site adjacent to Solent Road. This ditch, and a series of

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culverts, serve to convey flood flows away from the Site and back into the Lavant Stream downstream of the Site.

3.36. This flooding mechanism was also observed for the other modelled baseline events (refer to model plots in Appendix E).

3.37. In order to alleviate the flood risk to the Site, it was proposed to remove the 600 mm culvert in order to remove the hydraulic control. This is discussed in the following section.

Mitigation Modelling

3.38. In order to mitigate the risk of flooding to the Site, Ardent undertook an iterative process firstly be removing the 600 mm culvert on the Lavant Stream on the northern boundary of the Site from the 1D model domain. Elevations along the northern bank of the watercourse were also lowered in order to provide a degree of attenuation in order to reduce the potential risk in flooding downstream as a result of the increase in flows. In total a 145 m length of the northern bank was lowered to an elevation of 5.2 m AOD (average 750 mm depth of material). This served to alleviate the risk of flooding to the Site without impacting flood risk downstream. However, following an ecological assessment of the Site, it was confirmed that several trees had Tree Preservation Order (TPO) status and that it would not be possible to excavate the full 145 m reach. Therefore, targeted locations for excavation were established and it was proposed to also include a low level bund along the southern edge of the Lavant Stream. 3.39. The bund is to be set 5.0 m back from the watercourse with additional minor excavations carried out to provide additional attenuation. The bund is intended to tie in with brick arch culvert headwall at the north west corner of the Site. The bund has been designed to be typically 500 mm – 600 mm in height above adjacent ground levels. The proposed bund and excavation works are shown on drawing number 191920-001 in Appendix F. 3.40. In order to represent the bund and proposed excavation works within the 2D domain of the model, a series of ‘z_shapes’ were used that

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allow the ground model utilised within Tuflow to be manipulated by either lowering or raising elevations. This in addition to the culvert removal from the 1D domain were the only changes made between the baseline and mitigation modelling scenarios.

Mitigation Model Results

3.41. Figure 4-5 below shows the post development maximum flood depths for the 1 in 100 year plus 45% climate change mitigation scenario in comparison to the baseline flood extents. Model plots and comparison plots for all modelled events are included in Appendix G. It can be seen that the proposed mitigation measures of removing the culvert and the associated bund and excavation works have served to completely mitigate the risk of flooding to the Site. In addition, there is a de minimis impact on flood extents offsite as a result of the proposed works.

Legend Baseline flood extent Proposed bund Excavation works Flood Depth (metres)

Figure 4-5: 1 in 100 year plus 45% climate change, mitigation scenario maximum flood depths

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Sensitivity Testing

3.42. In order to test the accuracy of the model, it would be desirable to compare the modelled outputs against observed data and flood extents in order to calibrate and validate the model. However, there is currently no calibration data available which to test the model against. As a compromise, Ardent have modelled a range of return period events for both the baseline and proposed scenario as well as undertaken a series of sensitivity tests to determine the robustness and suitability of the model as well as to determine the impact of the proposed works offsite. This is considered to be wholly adequate given the scale of the proposed works and the nature of the FRAP application. 3.43. Standard modelling practice typically involves sensitivity testing of the following parameters:

• Boundary Conditions o Inflows o Downstream boundary (+/- gradient 20%) • Manning’s ‘n’ roughness (+/- 20%)

3.44. In testing the climate change scenario of the study area, the boundary conditions have been adjusted with an uplift in flows against the present day conditions but also at the downstream boundary. As discussed in Section 3.16, the study site is located within 1 km of the estuary and there is therefore a tidal influence at the downstream boundary. In the baseline scenario this has been accounted for by applying the 1 in 2 year maximum tidal curve taken from the JBA East Solent Tidal Model (2018). The 2 year present day tidal peak level, according to the East Solent Modelling study undertaken by JBA in July 2018, is 2.91m AOD. Guidance from the EA (December 2019) states that the anticipated rise in sea level for the south east of England (higher central allowance) up to the year 2115 is expected to be 1.21 m. Therefore, this value was used for the Climate Change adjustment. Based on the above the 2 year climate change tidal peak level is 4.11m AOD. 3.45. The results show that as expected with the uplift in inflows, there is an increase in maximum stage within the 1D results as well as an

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increase in flood extents in the 2D where flood water is coming out of bank. With respect to the downstream boundary, the additional application of 1.21 m due to climate change elevates maximum water level downstream of the Site (see Appendix H). It is this which is the dominant hydraulic control influencing flood level at this location as opposed to the gradient of the bed level in this downstream reach. The results show that the Site, and the culvert are sufficiently elevated above this maximum tidal level so as not to be influenced by the impact of tide locking. 3.46. With regard to the Manning’s ‘n’ roughness value sensitivity test, Ardent initially attempted to test this during the 1 in 100 year plus climate change event in the culvert removed scenario. However, due to the urbanised nature of the watercourse which flows through multiple culverts and structures, the 1D component of the model is quite sensitive when these structures become surcharged. During the climate change scenario, the steepness or ‘flashy’ nature of the urban hydrographs is amplified due to the significant uplift of 45% in peak flows (refer to example below) and exacerbates these instabilities. While testing Manning’s ‘n’ in the 1 in 100 year plus climate change scenario, the 1D component of the model routinely crashed before the peak flood level was reached due to the factors mentioned above. Therefore, in order to ensure a complete test of Manning’s ‘n’ could be assessed, the sensitivity test was carried out on the 1 in 100 year scenario without the application of climate change instead.

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Figure 4-6: Comparison of baseline vs climate change hydrograph

3.47. The 1D, 1 in 100 year Manning’s ‘n’ sensitivity results are presented in Appendix H. The results show that as expected, an increase in maximum stage within the 1D model associated with increase in Manning’s ‘n’ and a decrease in maximum stage associated with a reduction in Manning’s ‘n’. 3.48. This is also broadly reflected in the 2D results (Appendix H) with an increase in flooding associated with an increase in Manning’s ‘n’ and vice versa with a reduction. However, there are a couple of exceptions where the flood the +20% flood extent is less than the baseline scenario where flooding forms an overland flow path across roads and tarmacked areas. In the baseline scenario these areas have a Manning’s ‘n’ value of 0.025. In the +20% scenario this increases to 0.030. This increase in resistance reduces velocities and prevents the flood flow path propagating further. In the –20% scenario, despite there being even less resistance in these areas, there is less volume coming out of bank to cause an increase in flood extent. The model is therefore considered to be robust to changes in Manning’s ‘n’ with no significant changes as a result to changes in this parameter.

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4. CONCLUSIONS

4.1. This FRA has been produced to support the Flood Risk Activities Permit (FRAP) application for the removal of a 600 mm diameter culvert on the Lavant Stream where it flows through Portsmouth Water owned land at Solent Road, Havant.

4.2. In constructing a new hydraulic model of the Lavant Stream based on new survey data and updated hydrological inputs, Ardent have been able to make a more robust, accurate and up to date assessment of baseline flood risk at the Site when compared to the EA outputs shown on the Flood Map for Planning. The Ardent baseline modelling outputs established that the Site was at risk of flooding due to the insufficient capacity of the 600 mm diameter culvert which acts as the main hydraulic control along this reach. The culvert has a throttling effect thereby elevating the upstream water level resulting in flows coming out of bank and propagating across the Site.

4.3. Ardent have undertaken proposed mitigation modelling scenarios to determine the potential impact of removing the culvert to alleviate flood risk at the Site. There was a risk that by removing the culvert flood risk downstream of the Site could be increased as a result of the additional flow volumes being conveyed within the channel. Consequently, earthworks were proposed along the north bank of the Lavant Stream to provide a degree of attenuation and reduce any potential offsite impacts. However, due to the presence of Tree Protection Orders, opportunities to excavate here would be limited. A 145 m bund was therefore also proposed on the left bank of the watercourse set back by a distance of 5 metres. This would allow for further attenuation whilst also ensuring the Site remains flood free during the 1 in 100 year plus climate change scenario.

4.4. The results of the mitigation modelling simulations showed that there was de minimis impact on flood risk offsite with the culvert removed when compared to the baseline modelling results. Sensitivity testing of key parameters has demonstrated that the model is fit for purpose.

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4.5. In conclusion then this FRA has demonstrated that the FRAP application for removal of the culvert is acceptable in terms of not increasing flood risk offsite.

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Appendix A

EA PSO Team Modelling Methodology Consultation

John Easton

From: Partnership and Strategic Overview team, HIOW Sent: 26 June 2020 15:06 To: John Easton Cc: Chris Hardyman; Jenna Dewhurst; 'Tony Chalkley'; Simon Deacon; Steve Cross; Brian Cafferkey; Georgia Athanasia Subject: RE: EPR/PB3294JJ Ardent Flood Risk Report - Solent Road Havant [Filed 02 Jul 2020 11:28] Attachments: EPR_PB3294JJ Schedule 5 Notice of request for more information.pdf

Hi John,

Thank you for your comments.

Our response is as follows:

Thank you for submitting the extra clarification and justification behind some of the modelling techniques. We can confirm that we deem that the model is fit for the purpose of this Flood Risk Activity Permit, we caveat this statement with the fact that if this was to come in as part of a planning application the model may be scrutinised further.

As part of the FRAP we ask that you now produce a flood risk assessment using the model and the scenarios you have produced to clearly conclude an assessment of flood risk both on site and off site. Any FRA should be clear on the methodology used and this justified where appropriate. If the FRA finds that flood risk is increased as part of the proposal, mitigation measures should be outlined to tackle this. We should note that this does not have to be a lengthy document, but needs to assess the baseline and proposed flood risk of the works and clearly conclude this alongside any potential mitigation measures.

Chris, as Agent for this FRAP I attach the Schedule 5 request for information. When we have seen the updated FRA this will likely satisfy schedule 1 regarding addressing the flood risk. We still await a response to schedule 2-9 regarding the environmental concerns.

Thank you for your patience in reviewing this Flood Risk Report.

I would like to stress that as per our policy on culverts, we hope to facilitate the removal of culverts where possible through our role as regulator.

As such we are more than keen to help these works proceed. If you have any questions please do let me know.

We look forward to receiving your FRA as per above.

Kindly,

Nathan Bayley

Flood and Coastal Risk Management Officer – New Forest, Test & Itchen Environment Agency Partnership & Strategic Overview Team Environment Agency | Romsey Depot, Canal Walk, Romsey. SO51 7LP 020 7714 1072 [email protected]

Appendix G

Mitigation Modelling Results

Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix B SFRA assessment of site ref HB36

Prepared for: Chancerygate (Erdington) Limited

Land North of Solent Road – Site Ref: HB36 Basic Information The Site: The site is located north of Solent Road, east of Brockhampton Road and directly south of the current headquarters of Portsmouth Water.

Site Area: 1.68 ha

Allocation Proposal: Commercial (‘less vulnerable’)

Flood Risk Information Source / Pathway: Fluvial from Brockhampton Stream

Level of Flood Risk: A large part of the site is in FZ2 and 3, both in the present day and with climate change. As the vast majority of the site is shown to be in the area at risk of flooding, it cannot be avoided within the site.

The site benefits from defences along the Brockhampton Stream for the 1 in 40 year scenario. The defences consist of high ground and a wall and most of them are in good condition based on the last inspection undertaken in 2018;The 1D model results for the 1 in 100 year event (Flood Zone 2) indicate that the levels on the Brockhampton Stream range from 5.90 m AOD1 at the eastern (upstream) end of the watercourse site to 5.15 m AOD at the western (downstream) end of the watercourse.The 1D model results for the 1 in 1000 year event (Flood Zone 1) indicate that the levels on the Brockhampton Stream range from 5.93 m AOD in the eastern (upstream) end to 5.41 mAOD in the western (downstream) end of the watercourse.

Access / egress to the site is via Solent Road. However, the Environment Agency’s flood risk mapping indicates that Solent Road to the south of the site is in Flood Zone 3 and therefore at high risk of flooding. It is recommended that site-specific hydraulic modelling should be undertaken to refine the flood zone extents at the site and consequently determine if any mitigation measures are required to facilitate safe access / egress.

Current Day Zones 2 & 3 vs Climate Change 2115. Source: EA Flood Map and PUSH SFRA Sequential Approach - Can areas of flood risk be avoided? No – the vast majority of the site is in FZ2 and 3, both in the present day and with climate change. The access is also on FZ3. If flood risk cannot be avoided, what is the preferred approach? It may be possible to modify the shape of a fluvial floodplain to generate a more favourable flood outline that allows the development area of a site to be maximised. If that is to be pursued, it would be necessary to demonstrate that compensatory storage can be provided on a level for level basis for any floodplain displaced by a development. If it is proposed to develop areas in fluvial Flood Zone 3, compensatory 50 Land North of Solent Road – Site Ref: HB36 storage would be required. The feasibility of providing compensation at the site depends on ground conditions and groundwater levels below the site. It would also be necessary to demonstrate through hydraulic modelling that the proposed compensatory storage is effective at mitigating the loss of floodplain and effective at maintaining the current level of flood risk to neighbouring property. Conclusion on prospect of safe development in light of flood risk The EA have indicated that the key issue on this site is the offsite implications of flooding from development of the site i.e. floodplain compensation. Previous work has given confidence that an employment use can be safely delivered. On that basis, there is a prospect of safe delivery, although a detailed assessment of this would be required at application stage, in particular in relation to flood storage compensation, so any allocation policy would need to be heavily caveated with assessment requirements Implications for Local Plan 2036 It is acknowledged that the site was allocated in the previous Local Plan for a new Portsmouth Water HQ. The sequential test at that time was passed on the basis that the HQ had to be in this location for operational reasons, being close to a water source. The company has since decided to locate their HQ elsewhere and is promoting this site for general B1 or B8 (trade counter) use. The council considers that there are other sequentially preferable sites in the Borough for general employment use, and the exception made for the HQ use therefore falls away. Therefore, although it had been accepted in the past that there may be a prospect of safe delivery, this question does not arise, as the sequential test is not passed. An allocation for general employment use is not supported.

51 Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix C Topographical Survey & Utility Maps

Prepared for: Chancerygate (Erdington) Limited

5.75

So 5.37 Headwall WL 4.88 Bottom of bank level 4.85

17.59 5.14 Unable to survey 5.57 due to dense 5.68 4.70 vegetation. E: WL 14.56 4.75 Watercourse 5.16 OS Note: E: Wall ht 2m 5.40 Some services may have been omitted due to parked vehicles. 12.16 5.30 Watercourse The Ordnance Survey tile is to be used as a guide only. R: 5.78 5.34 4.99 14.37 Vegetation 5.15 5.15 5.52 OS Buildings Surveyed Buildings 5.11 WL 5.17 4.69 5.07 5.97 5.49 Unable to survey This survey has been orientated to the Ordnance Survey due to dense E: (O.S) National Grid OSGB36(15) via Global Navigation Satellite 5.30 vegetation. 5.62 13.07 Systems (GNSS) and the O.S. Active Network (OS Net). 5.33 5.33 R: 5.07 Vegetation A true OSGB36 coordinate has been established near to the 15.94 GH4 Unable to survey site centre via a transformation using the OSTN15GB & 5.395 due to dense OSGM15GB transformation models. vegetation. 5.62 5.69 5.0 5.22 Unable to survey The survey has been correlated to this point and a further one 5.24 due to dense 5.13 5.06 or more OSGB36 (15) points established to create a true O.S. 4.95 vegetation. bearing for angle orientation.

5.54 No scale factor has been applied to the survey therefore the 5.34 5.09 5.24 5.71 coordinates shown are arbitrary & not true O.S. Coordinates 5.35 5.46 which have a scale factor applied. Please refer to Survey Station Table to enable establishment 5.13 5.79

5.03 of the on-site grid and datum. 5.0 5.46 5.71 5.38 5.41

5.03 5.18 5.37 Tarmac 4.97 5.02 5.78 Legend: 5.03 5.65 5.82 Buildings Overhead Cable IC Inspection chamber Bo Bollard

5.71 5.85 Wall Concrete edge PInv Pipe invert IB Illuminated bollard R: Kerb line Tarmac edge Gy Gully Bin Rubbish bin 12.59 5.03 5.05 5.26 Line marking Grass verge Bg Back gully Vp Vent pipe 5.80 E: 5.0 5.35 Drop kerb Canopy/Overhang Dp Down pipe Grl Ground light 10.94 5.29 Centre line Verge Lbox Letter box MG 5.78 Pipe Pipe above ground 4.99 5.40 5.87 MG Top of bank Bottom of bank MH Manhole Stmp Tree Stump

4.93 Station and Name WL Water level Sty Stile Vegetation 5.77 5.78 1 5.30 100.000 Station Level Fl Flood light IFL Internal floor level R: 5.15 Lp Lamp post THL Threshold level 14.09 Bush Sap 4.88 Tree / Bush / Sapling Tp Telegraph post Sp Sign post

Wall ht 2m 4.85 Ep Electricity post TH Trialhole 5.73 Area of Undergrowth 4.89 5.83 Tl Traffic light BH Borehole Woodland 5.22 Bus Bus stop ELC Electric 5.73 5.04 5.5 R: 5.23 5.44 R: Ridge Level Sv Stop valve BT British Telecom

R: 4.95 4.99 14.10 5.52 12.91 5.31 6.02 E: Eaves Level St Stop tap C'box Control box 5.71 5.86 F: Flat Roof Level 5.61 Er Earth rod TT Tactile Vegetation MG Gate E: 5.83 Wm Water meter BP Brick paved C/L FenceFence ht 2m types: 10.92 4.92 5.51 MG Gas Gas valve CPS Concrete paving slabs Vegetation I\W Interwoven 5.25 Av Air valve CVR Cover I\R Vegetation 5.35 5.35 Iron Railings 5.33 ICU Unidentified inspection R/wall Retaining wall 4.92 5.20 5.26 W\M 4.86 5.76 Wire Mesh Wo Wash out TWL Top of Wall Level 4.78 S/M Fence ht 2m 5.55 4.82 5.55 P\R 5.60 Post & Rail Re Rodding eye TCL Tree canopy level P/F ht 1.8m P\W BB Belisha beacon G: Girth Post & Wire CTV Cable tv MG Multi girth C\L Chain Link

5.0 IC Inspection chamber 5.02 Mkr Marker post 4.93 W\P Wooden Panels 4.85 5.24 Gmkr Gas marker post CL: Cover level 4.94 C\B Close Boarded So Soffit IL: Invert level S\P Steel Palisade Fh Fire hydrant UTL Unable to lift

4.85 5.15 4.88 R: 5.17 13.17 4.85 4.89 4.86 4.75 E: 11.57 Rev Date Description Drawn Q. Ref. 4.92 GH3 G2.6 4.965 4.92 5.02 5.08 5.28

4.93

MG 5.03 5.18 5.12 5.0 IC 4.81 reenhatch 5.69 5.27 g S/M Fence ht 2m

5.25 group

5.0 5.32 5.28 4.88 Topographical Surveys Measured Building Surveys Site Engineering 3D Laser Scanning 5.35 5.0 4.94 R: Utility / CCTV Surveys Revit & BIM Models 9.99 5.31 4.84 4.92 Rowan House Vegetation Vegetation Duffield Road Vegetation Unable to survey IC 5.55 5.30 Little Eaton due to dense 5.28 4.74 E: vegetation. 5.03 Derby 5.26

5.60 8.64 DE21 5DR 5.52

5.33 5.59 4.69 Gy Tel (01332) 830044 Fax (01332) 830055

5.56 5.45 5.42 5.45 [email protected] 4.67 4.89 www.greenhatch-group.co.uk 5.54 5.43 St Albans Newcastle London

Hedge ht 2.8m Grass 5.23 27, Cornwall Terrace Mews 4.84 5.45 Unit B, The Courtyard 24 Riverside Studios Amethyst Road 5.18 Alban Park Regents Park 5.28 4.90 5.57 5.34 5.58 5.41 St Albans Newcastle Bus. Park London 4.98 Newcastle-U-Tyne 5.47 Hertfordshire 5.0 AL4 0LA NE4 7YL NW1 5LL

5.55 4.95 5.44 4.92 5.35 t. (01727) 854481 t. (01912) 736391 t. (02072) 241806 5.46 4.96

5.10 5.28 5.5 IC 5.16 4.95 CLIENT MG Tarmac 5.0 5.02 5.34 5.57 5.02 5.03 5.42 Gy WL 5.52 Chancerygate Group Ltd

4.72 4.78 Vegetation 5.42 WL Stmp 5.0 Lp 4.93 O/B Fence ht 1.8m Wall ht 1.8m 4.21 5.10 TCL: G2.2 5.0 Valve Barbed Wire topped 22.20 5.59 4.63 4.72 Sign 5.02 C/L Fence ht 1.8m 5.15 4.80 5.06 5.59 5.12 5.04 PInv 5.17 5.21 Vegetation 5.57 Ø0.45 Watercourse 4.86 Barbed Wire topped 4.98 4.97 2 trees missed Vegetation 5.46 4.75 4.99 3.98 Outfall C/L Fence ht 1.8m Due to dense vegetation IC 4.93

5.55 Vegetation 4.96 5.44 PROJECT 4.93 4.79 4.74 4.40 Vegetation 4.93 4.62 4.18 4.72 5.61 4.69 TCL: G0.7 Sp Headwall 5.39 G1.6 4.33 4.67 4.95 MG 5.13 C\L Fence ht 1.8m Sign Solent Road, 22.13 PInv 5.00 Gy 5.46 Gy PInv G0.6 G0.5 5.63 5.94 CTV 5.20 Ø0.45 G1.6 G0.6 G0.9 4.95 4.27 Headwall Ø0.6 TCL: G1.0 MG 4.46 4.42 5.47 5.45 5.53 4.15 5.91 Tarmac 5.66 5.49 4.14 Grass G0.8 5.15 4.88 5.71 Havant, 5.64 5.54 5.45 23.10 Headwall 5.26 5.08 5.48 5.40 5.11 5.55 5.81 TT 5.44 5.56 5.34 5.40 5.35 Lp 5.04 5.45 Gy 5.33 Grass MH G1.7 PInv 4.65 5.44 5.38 5.30 5.29 5.30 Tarmac 5.61 5.55 5.30 5.27 5.27 Bus 5.07 5.48 Ø0.6 4.86 4.85 PO9 1DQ 5.21 5.27 TCL: 4.16 5.39 5.92 Gy 5.20 5.19 5.22 Lp 5.59 5.44 5.79 5.17 5.24 5.29 22.39 TCL: G0.9 5.48 5.63 5.23 5.28 5.36 5.44 5.53 Gy 5.33 5.42 TT 16.80 5.56 Grass 5.40 5.12 5.37 Tarmac 5.47 TT TITLE 5.34 5.12 5.14 5.51 5.40 5.64 SOLENT ROAD 5.28 Gy 5.23 5.43 5.43 5.24 5.27 5.53 5.55 5.60 Tarmac 5.62 5.23 5.19 5.52 Lp Sp Topographical 5.80 5.53 5.24 5.33 5.38 5.42 5.57 5.67 Gy 5.26 5.42 5.61 5.90 5.42 5.31 Gy 5.77 5.31 5.19 5.37 5.46 CTV 5.21 5.13 5.43 5.42 5.50 Survey Tarmac TT 5.52 5.41 5.21 Gy 5.47 5.95 CTV Concrete 5.15 Gy 5.54 5.81 5.64 5.31 5.28 5.15 5.19 5.60 DATE 5.50 Lp 5.25 5.17 SOLENT ROAD 5.61 SCALE CBX 5.47 CTV Tarmac 5.24 5.25 Gy 5.25 5.28 5.26

GH1 TT 5.36 5.34 5.21 5.30 5.42 July 2019 5.324 Lp 5.31 5.36 5.34 A2@ 1: 500 5.27 TT CTV 5.40 5.39 Gy 5.24 Tarmac 5.44 5.46 Lp 5.38 Lp 5.49 5.50 5.48 5.44 St 5.56 DRAWN QUALITY REF 5.47 CTV 5.58 5.52 GH2 5.55 5.529 5.52 5.60 GH5411 5.66 LP

Level datum See note Grid orientation See note

Job number 34028

Drawing No. Rev. E: 13.08 R: 14.07 Station Information: 34028_T 0

R: F: 14.75 12.67 Station Easting (m) Northing (m) Level (m) Comments E: 13.90 This plan should only be used for its original purpose. Greenhatch Group accepts no responsibility GH1 471027.717 106076.764 5.324 for this plan if supplied to any party other than the original client. GH2 471118.766 106072.894 5.529 All dimensions should be checked on site prior to design and construction. GH3 471068.998 106137.864 4.965 Drainage information (where applicable) has been visually inspected from the surface and therefore should be treated as approximate only. GH4 471106.783 106198.564 5.395 Notes:

C Copyright Greenhatch Group. 06/07/13

OSA OSA

5.80 5.95

5.90

5.81

5.94

5.92

5.91

BT BT

LV SVY AREA

0.35d B2 0.35d

0.45d B2 0.45d

CTV

BT BT LV SVY AREA SVY AREA

Vegetation

Tarmac

5.81

5.67

5.77

5.79

BT BT LV

SVY AREA Wall ht 1.8m

4.63

Ø0.45

BT BT LV 3.98

PInv

5.66 Tarmac

4.21 5.39

SVY AREA

BT Watercourse BT WL LV 4.72

Outfall 5.64

5.55

5.64 Gy

5.53 Gy B4 AR

Valve

5.63

BT BT LV SVY AREA 5.02

4.78 SOLENT ROAD SOLENT MG

5.02

4.40

BT LV

SVY AREA

Stopped Rod

SVY AREA

5.44

5.54

Barbed Wire topped Wire Barbed C/L Fence ht 1.8m ht Fence C/L

E&C 5.34 Padlocked

BT BT

0.35d B2 0.35d

0.45d B2 0.45d 0.25d B2 0.25d SVY AREA UTR

5.57

5.49 TT

5.50 5.53

ED FO

E&C

5.52 SVY AREA

5.42

5.48 Unable tosurvey 5.38

CTV due todense

vegetation. TFR B4 TFR

BT BT 471000E

LV E&C

SVY AREA

5.12

FO CBX

CTV 5.18

LV SVY AREA 5.20

5.28 5.15

E&C SVY AREA

5.31

5.41

5.45

4.62

5.47

5.30

5.40

BT LV

SVY AREA

E&C

Concrete

BT BT

5.17 FO Grass

SVY AREA E&C

5.34

LV 5.25

TFR B4 TFR SVY AREA

FO 5.30

Padlocked

5.21

E&C

ED 4.69 TFR B4 TFR

SVY AREA

BT BT LV 5.32 UTR 5.28 IC 5.23

5.33 SVY AREA Gy

FO 5.33

E: 5.34

13.08 5.40 ED Ø150

Padlocked

E&C

BT BT LV Vegetation

5.31 UTR 5.69

IC FO 5.10 5.16 SVY AREA

5.28 5.26 ED

5.20 TFR B4

4.86

BT LV

SVY AREA 22.13 E&C

TCL: 5.35

0.35d B2 0.35d 5.23

0.45d B2 0.45d

0.25d B2 0.25d

5.36

FO 5.21 5.31 5.28 SVY AREA

Vegetation

5.30

BT BT LV

E&C

5.35 FO

5.19 SVY AREA R: 12" C.I. INLET PIPE TFR B4 14.07

SVY AREA LV ED 5.324 GH1

SL4.47

BT LV B4 TFR 5.0 5.12 Vegetation 4.93 14.10 R:

IC 5.28 5.19

Gy 5.29

14.37 E&C

OSA Ø300 R:

23.10 LV

G1.6 FO TCL: Lp

5.28 SVY AREA

BT LV BT 1.40d B2

LV 5.34 12.16 Headwall E: 4.89 4.93 14.56 Ø0.45 4.95

FO E&C 4.14

PInv CTV 17.59

4.98 ED

4.74 SVY AREA LV R:

4.75 B4 TFR

BT BT LV Ø300 4.92

Ø450 4.79 4.89 5.0 12.91 R:

OSA 4.94

FO Barbed Wire topped Wire Barbed

5.17 LV

5.27 TFR

C/L Fence ht 1.8m ht Fence C/L E&C 14.09

G1.6 4.86 12.59

5.0 R:

BT LV MH -TFR

UTL -DenseVegetation Approx Location

10.92

Grass 5.31 22.20 E: 4.80

TCL: LV

5.15 5.25

5.03 5.30

MG FO 10.94 E: G2.6

5.02

E&C ED

4.18 4.85

Ø225 TFR Ø225 LV

BT BT LV

4.88 5.24

4.74 4.94 SVY AREA G2.2 G0.8

SVY AREA Tarmac 4.72

15.94 FO

LV R:

TFR B4 TFR ED

13.07 E&C E:

Stmp

BT BT

LV 4.85 Tarmac LV SVY AREA

4.69 4.92

FO LV Watercourse G0.6

4.93 ED Vegetation SVY AREA 5.21 SVY AREA

LV SVY AREA SVY AREA

BT LV BT E&C 5.24 E&C TFR B4 4.95 Wall ht 2m Lp 4.86 5.13 E&C Overflow Level Sensor Cable LV 4.99 5.97 Gy

5.12 5.03

4.93 E&C

5.21 FO Gy LV

G0.5 E&C LV 1.40d B2 SVY AREA E&C Ø150 LV

ED E&C LV 1.40d B2 5.13 5.27 4.92 LV 5.30 LV 4.75

E&C LV WL

BT BT LV LV 4.69

5.27 E&C Ø375 TFR LV

G0.6

0.35d B2 0.35d

0.45d B2 0.45d 0.25d B2 0.25d 5.23 E&C TFR B4 4.89 4.93 4.97 LV

E&C LV

4.99 5.30

4.81 5.03 LV FO E&C 12" C.I. INLET PIPE TFR B4 R:

14.75 E&C TFR LV 5.68 5.34 471050E

G0.7 E&C

ED E&C LV SVY AREA

5.0 12" C.I. INLET PIPE TFR B4

BT BT

LV E&C

5.06 5.07 1.20d B2 Wall ht 2m4.70

Ø225 TFR Ø225 E&C 5.15 5.25 LV E&C

G0.9 Vegetation 4.85 E&C

FO LV 5.22

5.12 E&C E&C E&C

ED E&C TFR B4 LV 5.57 4.85

4.96 E&C

BT SVY AREA LV

BT E&C Overflow Level Sensor Cable TT E&C 4.95 E&C LV

4.78 E&C 5.04 E&C

E&C LV

FO 4.33 E&C

MH -TFR

UTL -DenseVegetation Approx Location E&C SVY AREA

OSA ED MH -TFR UTL -DenseVegetation Approx Location

4.93 E&C LV

SVY AREA

BT BT G1.0 LV 5.15 5.28 E&C E:

13.90 5.0 E&C

LV 0.60d B2 SVY AREA TFR B4 ØUNK

FO E&C 5.03 4.67

5.03

5.27 E&C ED 5.24 5.14 LV

5.0

LV BT 4.95 E&C AREA SVY

5.0 LV Vegetation

SVY AREA 5.26

Bottom ofbank 5.75

5.37 FO So MG 4.88 E&C OSA

5.15 ED Ø375 TFR

level 4.85 5.14 4.88

5.24 TFR B4 Headwall

BT BT LV Ø100 TFR TFR B4

Vegetation

5.17 SVY AREA SVY 4.75

ED Ø100 TFR

BT BT LV 5.16

Vegetation

4.88 Stopped

4.82

Rod 4.27

SVY AREA

SVY AREA SVY

LV BT

4.72 5.26 4.965 GH3 TFR B4

FO 5.29

4.84 4.88

BT BT 0.35d B2 0.35d LV 5.24 B2 0.40d F: 12.67

Vegetation

Ø375 TFR Ø375 4.98 AREA SVY

SVY AREA FO

5.21 4.96

BT BT LV 5.02

4.84

5.19

Gy 5.28 FO Ø150

5.19 SVY AREA SVY 4.97

TT Gy Unable tosurvey

BT 5.15

LV BT due todense

5.06 5.08 4.92

vegetation. FO

SVY AREA

BT 5.11 BT

LV 4.46 SVY AREA SVY

4.93

4.67

5.33 5.23

FO 5.0

5.38

5.31

BT BT LV

TFR B4

Grass 5.36

SVY AREA SVY FO 4.99

4.90

SVY AREA

4.95

BT BT LV

5.03

Stopped

Rod

0.35d B2 0.35d

5.26 0.45d B2 0.45d 5.36

Ø225 TFR Ø225 SVY AREA SVY

4.92

BT BT LV

SVY AREA

Due todensevegetation 5.0

5.11 5.0

5.27

5.37

4.95 4.42 5.09 Bus 2 treesmissed

5.08

BT LV

SVY AREA SVY

5.42 5.33

CTV 5.44

5.37

BT BT LV

5.02

5.33 SVY AREA SVY

SVY AREA

Tarmac

5.30

5.40

4.99

5.52

BT LV

5.40

5.04 471100E 5.13 5.07

Vegetation

SVY AREA SVY Ø225

5.04

SVY AREA 5.02 4.92

BT BT LV

Watercourse

5.47 C\L Fence ht 1.8m ht Fence C\L Vegetation 5.03

5.05

5.33

5.43

5.22

BT BT LV

SVY AREA SVY

5.27

5.43 5.0

5.47

Tarmac

5.49

5.13 5.17

5.395 GH4

0.35d B2 0.35d

5.78 0.45d B2 0.45d

IL3.63

BT LV 5.07

SVY AREA MH

5.17 Vegetation

Ø225

5.24

5.34

5.44

BT BT LV SVY AREA SVY 22.39

5.48 5.51

G1.7 5.38 TCL: 5.20

5.00 5.10 5.43

SVY AREA

5.15

SOLENT ROAD SOLENT

BT BT LV

Headwall

5.52

Ø0.6 AREA SVY 4.16 PInv

5.47 OSA

O/B Fence5.5 ht 1.8m

BT BT LV 5.61 5.59 Hedge ht 2.8m

5.529 GH2 5.58 TT 5.59 5.60

5.40

5.24 SVY AREA SVY SVY AREA 5.55 5.63 5.18

Lp 5.59

BT BT LV 5.47 5.57 Tarmac

Gy 5.55 5.57 5.18

Ø600 5.44 5.565.59

5.42 5.55

5.46 5.15 5.39 5.49 5.44 5.46 5.45 Blocked NVE

5.42 5.42

BT BT

LV Gy SVY AREA SVY

5.45 Gy 5.45 5.45 5.34 Blocked NVE 5.42

5.44 5.45 5.44 5.55 5.25 SVY AREA SVY

Sp AREA SVY

Sign AREA SVY

SVY AREA SVY 5.47 SVY AREA SVY

BT AREA SVY BT 5.56

5.55 AREA SVY

SVY AREA SVY

5.52 AREA SVY 5.52 5.25 5.43

Sign AREA SVY

Lp AREA SVY 5.28

SVY AREA 5.61 AREA SVY

SVY AREA SVY

5.54

SVY AREA SVY

5.35 SVY AREA SVY

5.42 5.24

SVY AREA SVY 5.53

S/M Fence ht 2m AREA SVY 5.53 OSA

5.30

5.39

LV 5.35

5.41

0.40d B2 0.40d 0.45d B2 0.45d

5.46 4.65 Headwall 5.37

5.42 5.50 Gy Ø0.6 4.15

PInv

5.55

5.54 SVY AREA

5.52 SVY AREA SVY

BT BT LV 8.64 St 5.42

SVY AREA 5.52

SVY AREA Ø150 5.35 R:

9.99

BT BT

5.35 5.60 16.80

TCL: 5.46

SVY AREA

BT BT LV Unable tosurvey

Vegetation SVY AREA SVY

G0.9

5.46 5.60 due todense 5.56

5.56 Tarmac E: vegetation. 11.57 5.22 R:

SVY AREA

13.17

BT BT

LV 4.86

SVY AREA 5.71

SVY AREA

5.26

5.46

5.57

5.60

5.62 5.48

Grass

CTV SVY AREA SVY AREA SVY Lp

SVY AREA

BT BT

5.33

SVY AREA

5.38

0.40d B2 0.40d

0.45d B2 0.45d

SVY AREA SVY

BT BT LV

S/M Fence ht 2m ht Fence S/M 471150E

5.41

5.66 5.48

SVY AREA

5.58

5.61

BT LV Sp 5.23

SVY AREA

5.50

5.61 5.29

5.34

5.44 5.64

SVY AREA SVY

OSA OSA 4.85

SVY AREA

SVY AREA TFR B4

WTR 5.35 9" ST TFR B4 5.26 WTR WTR

WTR Abandoned Main 5.40 9" ST TFR WTRB4 SVY AREA WTR WTR

SVY AREA WTR Abandoned5.46 Main 5.31 WTR WTR EOT NDI B3 SVY AREA

WTR Dense Vegetation 5.65

SVY AREA EOT WTR Dense 9" ST TFRWTR B4

WTR Vegetation 5.44 5.77 Unable tosurvey TFR B4 Abandoned Main MG due todense

vegetation. SVY AREA 5.5 SVY AREA

5.52 5.54 5.55

SVY AREA 5.51

5.71 5.71

Ø375 TFR

SVY AREA

5.83 Chamber Extents Unable toSurvey Above Ground Silt Level Back Drop Off SurveyArea Taken FromRecords Weak Signal Head ofRun End ofTrace Depth toTopofService(m) Contracted SurveyArea UTILITY SURVEYINFORMATION Fibre Optic Electric Overhead Electric HighVoltage Electric LowVoltage Electric &Comms NOTES Empty Duct Earth Cable Drainage -StormWater Drainage -FoulWater Drainage -CombinedWater Communication Cable CCTV /CableTelevision British TelecomOverhead British Telecom Air Line UTILITY LINETYPES

In allcasespleasecalltheBTDialbeforeyoudigservicetomarktheirownplantanysiteworks commence

0800 9173993 Always consultutilityplans

1. 3. 2.

SVY AREA 5.62

5.78

record searchesundertaken.Thisinformationhasbeenaddedfromtheseplans(DwgNo.s62/90C/40, 62/90C/SH& Please notethatwewerepresentedwithonsiterecordswhichshowedapparatusnothighlighted thestatutory been madetocorrectlyidentifytheduty/pipes/chamberdetail,itisrecommendedthatthisinformation shouldbe Drainage Informationprovidedhasbeendeterminedwithoutmanentryintothechambers.Whilstevery efforthas 62/90C/??) of asondeorCCTVsurvey. checked inareasthatarecriticaltothefutureproposal/development.

All sewerrunsarepresumedtobestraightlineconnectionsbetweenchambersunlessprovenotherwise bytheuse SVY AREA 5.55 5.71 5.86 MG Tarmac SVY AREA

SVY AREA 5.83 5.80

SVY AREA 5.60 Ø150 Ø150 Ø150 5.62 0.40d 5.71 OSA EOT TFR HoR A/G WS BD SL

SVY AREA SVY AREA SVY Multiple Services Route GPR Anomaly No DepthIndicated No PipesVisible No VisibleExit Sound Connection Assumed Connection Assumed Route Unable toTrace Unable toRaise(cover) Unable toSurvey Trench Scar Water Vent Line Vapour Recovery Unknown Traffic LightSignals Telecom Rising Main Oil Pipe Offset Fills Heating Pipes GPR Line Gauge Line Gas Line Fuel Line

5.61 5.69

P/F ht 1.8m

5.78 471200E

SVY AREA SVY SVY AREA SVY

5.87 AREA SVY 5.76 5.79

TFR B4

SVY AREA SVY SVY AREA SVY MG

Unable tosurvey SVY AREA SVY 5.73

due todense

vegetation.

5.85

SVY AREA SVY SVY AREA SVY NPV NVE ACP UTR UTT UTS NDI S/C

AR 5.73

purpose. GreenhatchGroup acceptsnoresponsibility

Notes: Comments should betreated asapproximateonly. visually inspectedfrom the surfaceandtherefore Drainage information(where applicable)hasbeen to designandconstruction. All dimensionsshouldbe checkedonsiteprior the originalclient. for thisplanifsuppliedto anypartyotherthan This planshouldonlybe usedforitsoriginal

Drawing No. Unit B,TheCourtyard LEGEND Grid orientation Level datum C Rev Job number

CLIENT TITLE PROJECT

St Albans

t. (01727)854481 Line marking Top ofbank Centre line g 100.000 1 Drop kerb Buildings Kerb line Topographical Surveys Hertfordshire Tel (01332)830044 S\P C\B W\P C\L P\W P\R W\M I\R I\W Utility /CCTVSurveys A2@ 1: TYPE B-DETECTION SURVEY CATEGORY Alban Park Wall F: E: R: St Albans Chancerygate GroupLtd Bush AL4 0LA

Site Engineering Date reenhatch Sap

Flat RoofLevel Eaves Level Ridge Level

SCALE DRAWN

Tree /BushSapling Station Level Station andName

Close Boarded Wooden Panels Chain Link Post &Wire Post &Rail Wire Mesh Iron Railings Interwoven Area ofUndergrowth Steel Palisade Gate Woodland 34028_T_UG Canopy/Overhang Overhead Cable Bottom ofbank RW Concrete edge Tarmac edge Grass verge [email protected] Verge www.greenhatch-group.co.uk 500 Solent Road, Rowan House Duffield Road

Newcastle PO9 1DQ DISCLAIMER

24 RiversideStudios

Little Eaton

Newcastle Bus.Park

34028 See note t. (01912)736391 See note Havant, DE21 5DR Newcastle-U-Tyne

Survey Amethyst Road Description Utility PAS 128:2014 Fh So Gmkr Mkr CTV BB Re Wo ICU Av Gas Wm Er St Sv Bus Tl Ep Tp Lp Fl WL MH Pipe Dp Bg Gy PInv IC Derby QUALITY LEVEL group NE4 7YL QL-B2 QL-B3 QL-B4 QL-B1

N Unidentified inspection Fire hydrant Soffit Gas markerpost Marker post Cable tv Belisha beacon Rodding eye Wash out Air valve Gas valve Water meter Earth rod Stop tap Stop valve Bus stop Traffic light Electricity post Telegraph post Lamp post Flood light Water level Manhole Pipe aboveground Down pipe Back gully Gully Pipe invert Inspection chamber Fax (01332)830055

Measured BuildingSurveys QUALITY REF Revit &BIMModels July 2019 3D LaserScanning GH5411 POSITION POSITION POSITION OFTHEUTILITYDETECTEDBYONE (EML ORGPRDETECTIONWITHCONFIDENCEIN THEREFORE SHOWNASANASSUMEDROUTE. A UTILITYSEGMENTWHICHISSUSPECTEDTO BY ONEOFTHEGEOPHYSICALTECHNIQUES.

CRITERIA USEDINTHEDETERMINATIONOF DATE BY MULTIPLEGEOPHYSICALTECHNIQUES. EXIST BUTHASNOTBEENDETECTEDAND 27, CornwallTerraceMews (EML ORGPRDETECTIONWITHLIMITED London IFL Sty Lbox Grl Vp Bin IB Bo TT C'box BT ELC BH TH Sp THL TWL R/wall CVR CPS BP Stmp UTL THE GEOPHYSICALTECHNIQUES.

t. (02072)241806 MG G: TCL

IL: CL: IC Drawn AND DEPTH AND DEPTH (NO DETECTIONPOSSIBLE) (EML +GPRDETECTION) CONFIDENCE INDEPTH) Regents Park QUALITY LEVEL Bollard Internal floorlevel Stile Letter box Ground light Vent pipe Rubbish bin Illuminated bollard Unable tolocate Invert level Cover level Inspection chamber Multi girth Girth Tree canopylevel Top ofWallLevel Retaining wall Cover Concrete pavingslabs Brick paved Tactile Control box British Telecom Electric Borehole Trialhole Sign post Threshold level Tree Stump NW1 5LL

DEPTH)

London OFTHEUTILITYDETECTED OFTHEUTILITYDETECTED

Q. Ref. Rev. Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix D Proposed Development Plan

Prepared for: Chancerygate (Erdington) Limited

N NOTES

Reproduced from the Ordnance Survey map with the permission of the Controller of Her Majesty's Stationery Brockhampton Springs Office, © Crown Copyright.

C A Cornish & Associates Ltd Licence no LIG0908. Water Subject to Statutory Approvals. Water Landscaping is indicative, please refer to Landscape Architect's drawing(s) for details of trees & planting Issues

Tank

KEY

8 . 2M HIGH BLACK WELDMESH FENCE WITH

9 T P MATCHING GATES

. .

P T

W . 8 CHARCOAL BLOCK PAVING 10

3 BUFF BLOCK PAVING

1 The Old 1 3

7 Manor House 2 GAS m (enclosure/ CONCRETE

53 27 g TBC) a fencin

r 3 TARMAC

7 0

0 12

n EXISTING TREES TO BE RETAINED

0 o 2

t REFUSE/ 0 p 1

RECYCLE PROPOSED TREES (enclosure/ 1

m fencing TBC) 9 5 a O h FFIC

k E

o A4

1 4

to 6 100 CAR SPACES

P.T.W.

o Rev Description Chk Date

0 Manor Court 4

A3 1 Peer House 8 -14 Verulam Street London WC1X 8LZ

3 SIGN tel +44(0)20 7400 2120

[email protected]

architects 5 6 www.cornisharchitects.com A2 1 1

The 0

4 Bosmere Medical Centre cornish Project Title. A1 SOLENT ROAD HAVANT 5 S 6 S 2 E E N Drawing Title. R A G L SITE PLANO N R BLO P CK A O AS PROPOSED T N

S/S P I

1 5 1 M Drawing Status. K A R H O K TOWN PLANNING W C TOTEM O SIGN Gas Gov R B 0 5 40 metres

Drawn By. Scale. Date. Chk'd By. RP 1:500 @ A2 14/10/2020 ED SOLENT ROAD EXISTING ACCESS WIDENED TO HIGHWAYS REQUIREMENT

Drawing No. Rev. 19003 - TP - 003 -

Copyright of Cornish Architects c 27 Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix E Proposed Drainage Strategy Layout

Prepared for: Chancerygate (Erdington) Limited

E&C

LV 0.60d B2

E&C LV

E&C

LV WL

E&C

E&C LV TFR B4

LV E&C

TFR B4

E&C WL

LV TFR B4 TFR

1.20d B2 E&C 1:80 LV

TFR B4

E&C WTR

WTR Ø375 TFR

E&C TFR B4

WTR 10 9" ST TFR B4 TFR ST 9"

E&C LV Main Abandoned

POROUS PARKING -2 WTR

LV Contributing area = 1,100m²

E&C

5.80 WTR Subbase storage area = 1,040m² 11 POROUS PARKING -1 LV Permeable block to the parking bays only and

1200000 E&C MH - TFR 5.25 L.6.0m Ø375 @1:

700000 Contributing area = 1,570m²

subbase storage max.320mm to the carpark areas. WTR Approx Location Ø375 TFR XXX(TBC) 2752775 LV UTL - Dense Vegetation outfall restricted by Ø100 pipe GAS Subbase storage area = 1,420m² 12" C.I. INLET PIPE TFR B4 E&C

2752775 WTR Permeable block to the parking bays only and

Overflow Level Sensor Cable LV subbase storage max.320mm to the carpark areas.

E&C 1:60 WTR outfall restricted by Ø100 pipe. 3

700000 Ø375 TFR

1200000

WTR 5.70

E&C

5.30 B4 TFR ST 9" LV Main Abandoned 1:4

5.40 WTR

5.50

E&C 5.52 5.60 LV 5.60 1:3 5.70

L.27.0m Ø375 @1: XXX(TBC) WTR

LV E&C

1:4 20 EXISTING Ø375 SW SEWER TO BE 1.40d B2 WTR 6.02 DIVERTED BUILD NEW MANHOLE

LV E&C REFUSE/ BUILD NEW MANHOLE ON

ON EXISTING Ø375 SW WTR 1:5 RECYCLE EXISTING Ø375 SW SEWER,

LV SEWER, IL TO BE TFR B4

1:3

E&C IL TO BE CONFIRMED

Ø100 TFR CONFIRMED WTR 6.47 Ø100 TFR 8m BUFFER ZONE TO THE 1:40

LV EDGE OF WATERCOURSE WTR

E&C 1:36 OFFICE UNIT FFL= 5.70 LV Surface water to drain

E&C

to watercourse with new Vegetation Dense

LV 1:40 EOT Headwall

1 E&C

LV WTR 12" C.I. INLET PIPE TFR B4 A4

1.40d B2 E&C B3 NDI

1:42 WTR 5.50

Brockhampton Stream

E&C SW rising main

TFR B4 5.40 Vegetation Dense

TFR EOT

LV MH - TFR E&C Approx Location 3

UTL - Dense Vegetation 1:40 5.30 WTR

E&C 1:39 1:4 4

1:3 WTR 1 to 6 LV Flow Control (pump) restricted 1:40

E&C 1:60

to 5.3 l/s (Greenfield rate) 5.20 WTR

LV PS 1:60 1:33

E&C WTR

LV 9" ST TFR B4 TFR ST 9" Abandoned Main Abandoned

E&C

LV 1:40 LV 4

E&C

EXISTING WATER MAIN TO BE B4 TFR A3 1 DIVERTED SUBJECT TO FURTHER LV

E&C INVESTIGATION

LV 5.10

5.10

Flood volume for 100yr+40%cc 5.20

E&C

LV 6.31 5.30

5.40

5.40 5.30

Total Volume = 60.0 m³ 5.20 TFR B4 LV accommodated within site at max. depth LEGEND E&C at 120mm, max. flood level = 5.14m LV

3 EXISTING PUBLIC FOUL WATER PIPE Ø375 TFR

LV E&C Ø225 TFR NEW FOUL WATER PIPE LV 1:60 NEW FOUL WATER INSPECTION CHAMBER

E&C LV ATTENUATION TANK NEW FOUL WATER MANHOLE MH - TFR LV Approx Location E&C EXISTING PRIVATE/PUBLIC STORM WATER PIPE 1.40d B2 UTL - Dense Vegetation Surface Water Attenuation Tank LV 1:40 PROPOSED BUND 650m² x 0.8m x 95% Porosity ABANDONED EXISTING STORM WATER PIPE

TOTAL VOLUME = 1,120m³ E&C LV SIDE SLOPE = 1:3 UNIT FFL= 5.20 Water Volume = 494 m³ NEW DIVERTED STORM WATER PIPE MAX. HEIGHT = 1.5m Drained Area = 8,830 m² LV 5 NEW STORM WATER PIPE E&C (Designed for 30yr) A2 1 NEW STORM WATER INSPECTION CHAMBER16 Ø225 TFR E&C NEW STORM WATER MANHOLE 12" C.I. INLET PIPE TFR B4 TFR B4 1:40

E&C PS NEW PUMP

PI PETROL INTERCEPTOR

E&C The RA LINEAR DRAINAGE CHANNEL 20

E&C ROAD GULLY

4 1:60 Bosmere

E&C PROPOSED CELLULAR STORAGE

EXISTING Ø225 FW SEWER TO BE 1:38 E&C Medical Centre 5.75 DIVERTED 1:4 POROUS SUBBASE

E&C

8m BUFFER ZONE TO THE EDGE

E&C 1:60 A1 OF WATERCOURSE

5.10 SITE BOUNDARY

E&C 5.20 Gy

5.30

5.40 5.40 5.42 5.40NVE E&C 5 Blocked Service yard and other vehicular

Overflow Level Sensor Cable E&C accessed areas (3,430m²) to 1:70 pass through petrol interceptor 26

E&C before draining to the tank.

PI-1

5.86

E&C 1:60 TFR B4 Ø225 TFR

E&C TFR

E&C N

S/S 1:75

1 Gy

E&C 5 1 OSA Ø300 5.42 Lp Stmp NVE TCL: P1 12.04.21 FOR PLANNING APPROVAL RM IL TFR B4 E&C Blocked E&C E&C 22.20 E&C E&C E&C E&C Rev. Date Description Technician Reviewer E&C E&C

Drawing Ø225 DRAINAGE LAYOUT 1:48 4.93 BUILD NEW MANHOLE ON & CONSULTING ltd. SL4.47 EXISTING Ø225 FW SEWER Sp I L Gas Gov PInv Gy Gy PInv E: [email protected]

Ø150 BROCKHAMPTON LANE 5.47 5.45 TCL: Project Scale Project Number Drawing Number Revision 23.10 Ø150 Ø225 Lp Ex.MH 1:250 @ A1 FO Ø600 ED BT ED BT FO FO MH PInv BT BT ED BT ED BT FO FO SOLENT ROAD, HAVANT 21-012-CHA D00 P1 BT BT ED BT BT FO LV LV BT ED BT ED BT FO BT FO 5.07 LV LV BT ED BT ED BT FO BT FO Ø225 1:500 @ A3 LV BT ED BT BT FO BT 5.07 LV LV ED BT ED FO BT FO BT LV BT ED BT FO BT Bus Ø150 LV LV ED BT ED BT FO BT BT LV ED BT FO BT FO BT BT IL3.63 TCL: Rod Lp IL3.63

Ø300 Flood Risk Assessment 21-012_Land North of Solent Road, Havant North of Solent Road, Havant

Appendix F Hydraulic Calculation

Prepared for: Chancerygate (Erdington) Limited

I&L Consultants (Dubai) Page 1 29-31 Castle Street High Wycombe Buckinghamshire, HP13 6RU Date 05/04/2021 17:44 Designed by RishadMannil File Checked by Innovyze Source Control 2020.1.3

ICP SUDS Mean Annual Flood

Input

Return Period (years) 2 Soil 0.400 Area (ha) 1.500 Urban 0.000 SAAR (mm) 725 Region Number Region 7

Results l/s

QBAR Rural 5.3 QBAR Urban 5.3

Q2 years 4.7

Q1 year 4.5 Q30 years 12.1 Q100 years 17.0

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-1 or 30yr.SRC

ste utl el tutues

(None) ank or 30yr.SRC (None)

Hal Drain ime : 169 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 5.101 0.031 0.0 0.4 0.4 13.0 30 min Summer 5.115 0.045 0.0 0.9 0.9 19.2 60 min Summer 5.129 0.059 0.0 1.7 1.7 25.0 120 min Summer 5.138 0.068 0.0 2.0 2.0 28.9 180 min Summer 5.142 0.072 0.0 2.2 2.2 30.5 240 min Summer 5.144 0.074 0.0 2.3 2.3 31.5 360 min Summer 5.146 0.076 0.0 2.4 2.4 32.5 480 min Summer 5.147 0.077 0.0 2.4 2.4 32.8 600 min Summer 5.147 0.077 0.0 2.4 2.4 32.8 720 min Summer 5.146 0.076 0.0 2.4 2.4 32.5 960 min Summer 5.144 0.074 0.0 2.3 2.3 31.6 1440 min Summer 5.139 0.069 0.0 2.1 2.1 29.6 2160 min Summer 5.133 0.063 0.0 1.9 1.9 26.9 2880 min Summer 5.129 0.059 0.0 1.7 1.7 24.9 4320 min Summer 5.122 0.052 0.0 1.3 1.3 22.3 5760 min Summer 5.118 0.048 0.0 1.1 1.1 20.5 7200 min Summer 5.115 0.045 0.0 0.9 0.9 19.0

t R le se ee et / lue lue s

15 min Summer 69.220 0.0 10.2 19 30 min Summer 46.082 0.0 16.5 33 60 min Summer 29.395 0.0 25.4 62 120 min Summer 18.205 0.0 33.5 114 180 min Summer 13.601 0.0 38.4 140 240 min Summer 11.003 0.0 42.0 170 360 min Summer 8.144 0.0 47.3 238 480 min Summer 6.575 0.0 51.2 304 600 min Summer 5.565 0.0 54.4 370 720 min Summer 4.855 0.0 57.0 436 960 min Summer 3.911 0.0 61.2 566 1440 min Summer 2.880 0.0 67.0 812 2160 min Summer 2.117 0.0 74.9 1172 2880 min Summer 1.701 0.0 78.9 1532 4320 min Summer 1.247 0.0 83.5 2252 5760 min Summer 1.000 0.0 88.2 3000 7200 min Summer 0.843 0.0 89.7 3744

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-1 or 30yr.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 5.112 0.042 0.0 0.8 0.8 17.7 10080 min Summer 5.109 0.039 0.0 0.7 0.7 16.6 15 min Winter 5.106 0.036 0.0 0.6 0.6 15.4 30 min Winter 5.122 0.052 0.0 1.3 1.3 22.3 60 min Winter 5.137 0.067 0.0 2.0 2.0 28.6 120 min Winter 5.148 0.078 0.0 2.5 2.5 33.1 180 min Winter 5.151 0.081 0.0 2.6 2.6 34.7 240 min Winter 5.153 0.083 0.0 2.8 2.8 35.4 360 min Winter 5.154 0.084 0.0 2.8 2.8 35.7 480 min Winter 5.153 0.083 0.0 2.7 2.7 35.3 600 min Winter 5.151 0.081 0.0 2.6 2.6 34.6 720 min Winter 5.149 0.079 0.0 2.5 2.5 33.7 960 min Winter 5.145 0.075 0.0 2.3 2.3 31.9 1440 min Winter 5.137 0.067 0.0 2.0 2.0 28.7 2160 min Winter 5.129 0.059 0.0 1.7 1.7 25.2 2880 min Winter 5.124 0.054 0.0 1.4 1.4 23.1 4320 min Winter 5.118 0.048 0.0 1.0 1.0 20.4 5760 min Winter 5.113 0.043 0.0 0.8 0.8 18.1 7200 min Winter 5.109 0.039 0.0 0.7 0.7 16.5 8640 min Winter 5.106 0.036 0.0 0.6 0.6 15.3 10080 min Winter 5.104 0.034 0.0 0.5 0.5 14.4

t R le se ee et / lue lue s

8640 min Summer 0.733 0.0 90.4 4488 10080 min Summer 0.651 0.0 90.2 5152 15 min Winter 69.220 0.0 12.5 19 30 min Winter 46.082 0.0 19.7 32 60 min Winter 29.395 0.0 29.6 60 120 min Winter 18.205 0.0 38.6 114 180 min Winter 13.601 0.0 44.1 142 240 min Winter 11.003 0.0 48.2 178 360 min Winter 8.144 0.0 54.1 252 480 min Winter 6.575 0.0 58.6 324 600 min Winter 5.565 0.0 62.2 392 720 min Winter 4.855 0.0 65.2 462 960 min Winter 3.911 0.0 70.0 596 1440 min Winter 2.880 0.0 76.8 850 2160 min Winter 2.117 0.0 85.7 1208 2880 min Winter 1.701 0.0 90.5 1560 4320 min Winter 1.247 0.0 96.3 2332 5760 min Winter 1.000 0.0 102.0 3056 7200 min Winter 0.843 0.0 104.4 3816 8640 min Winter 0.733 0.0 105.8 4560 10080 min Winter 0.651 0.0 106.4 5248

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or PP-1 or 30yr.SRC

Rainall Model FSR Winter Storms es Return Period (years) 30 Cv (Summer) 0.750 Region ngland and Wales Cv (Winter) 0.840 M5-60 (mm) 19.100 Shortest Storm (mins) 15 Ratio R 0.350 Longest Storm (mins) 10080 Summer Storms es Climate Change 0

ime Area Diagram

otal Area (ha) 0.157

e s e

0 4 0.157

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or PP-1 or 30yr.SRC

Storage is nline Cover Level (m) 5.520

Porous Car Park Structure

Iniltration Coeicient Base (m/hr) 0.00000 Width (m) 32.0 Membrane Percolation (mm/hr) 1000 Length (m) 44.4 Ma Percolation (l/s) 394.7 Slope (1:) 0.0 Saety Factor 2.0 Depression Storage (mm) 5 Porosity 0.30 vaporation (mm/day) 3 Invert Level (m) 5.070 Membrane Depth (m) 0

Pipe utlo Control

Diameter (m) 0.100 ntry Loss Coeicient 0.500 Slope (1:) 150.0 Coeicient o Contraction 0.600 Length (m) 10.000 Upstream Invert Level (m) 5.070 Roughness k (mm) 0.600

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-2 or 30yr.SRC

ste utl el tutues

(None) ank or 30yr.SRC (None)

Hal Drain ime : 137 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 4.829 0.029 0.0 0.4 0.4 8.9 30 min Summer 4.842 0.042 0.0 0.8 0.8 13.1 60 min Summer 4.854 0.054 0.0 1.4 1.4 16.9 120 min Summer 4.862 0.062 0.0 1.8 1.8 19.2 180 min Summer 4.865 0.065 0.0 1.9 1.9 20.2 240 min Summer 4.867 0.067 0.0 2.0 2.0 20.8 360 min Summer 4.868 0.068 0.0 2.1 2.1 21.3 480 min Summer 4.868 0.068 0.0 2.1 2.1 21.3 600 min Summer 4.868 0.068 0.0 2.0 2.0 21.1 720 min Summer 4.867 0.067 0.0 2.0 2.0 20.8 960 min Summer 4.864 0.064 0.0 1.9 1.9 20.0 1440 min Summer 4.860 0.060 0.0 1.7 1.7 18.6 2160 min Summer 4.854 0.054 0.0 1.4 1.4 17.0 2880 min Summer 4.851 0.051 0.0 1.2 1.2 15.8 4320 min Summer 4.845 0.045 0.0 0.9 0.9 14.0 5760 min Summer 4.840 0.040 0.0 0.8 0.8 12.6 7200 min Summer 4.837 0.037 0.0 0.7 0.7 11.6

t R le se ee et / lue lue s

15 min Summer 69.220 0.0 7.3 19 30 min Summer 46.082 0.0 11.9 33 60 min Summer 29.395 0.0 17.9 62 120 min Summer 18.205 0.0 23.5 100 180 min Summer 13.601 0.0 27.0 130 240 min Summer 11.003 0.0 29.5 162 360 min Summer 8.144 0.0 33.2 230 480 min Summer 6.575 0.0 36.0 296 600 min Summer 5.565 0.0 38.2 362 720 min Summer 4.855 0.0 40.1 426 960 min Summer 3.911 0.0 43.0 550 1440 min Summer 2.880 0.0 47.1 794 2160 min Summer 2.117 0.0 52.3 1164 2880 min Summer 1.701 0.0 55.1 1528 4320 min Summer 1.247 0.0 58.2 2252 5760 min Summer 1.000 0.0 61.2 3000 7200 min Summer 0.843 0.0 62.2 3744

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-2 or 30yr.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 4.835 0.035 0.0 0.6 0.6 10.8 10080 min Summer 4.833 0.033 0.0 0.5 0.5 10.3 15 min Winter 4.834 0.034 0.0 0.5 0.5 10.5 30 min Winter 4.849 0.049 0.0 1.1 1.1 15.3 60 min Winter 4.862 0.062 0.0 1.8 1.8 19.3 120 min Winter 4.870 0.070 0.0 2.1 2.1 21.8 180 min Winter 4.873 0.073 0.0 2.3 2.3 22.9 240 min Winter 4.875 0.075 0.0 2.3 2.3 23.2 360 min Winter 4.874 0.074 0.0 2.3 2.3 23.0 480 min Winter 4.872 0.072 0.0 2.2 2.2 22.5 600 min Winter 4.870 0.070 0.0 2.1 2.1 21.8 720 min Winter 4.868 0.068 0.0 2.0 2.0 21.1 960 min Winter 4.863 0.063 0.0 1.9 1.9 19.7 1440 min Winter 4.857 0.057 0.0 1.5 1.5 17.7 2160 min Winter 4.851 0.051 0.0 1.2 1.2 15.8 2880 min Winter 4.847 0.047 0.0 1.0 1.0 14.5 4320 min Winter 4.840 0.040 0.0 0.7 0.7 12.3 5760 min Winter 4.835 0.035 0.0 0.6 0.6 11.0 7200 min Winter 4.833 0.033 0.0 0.5 0.5 10.1 8640 min Winter 4.830 0.030 0.0 0.4 0.4 9.4 10080 min Winter 4.828 0.028 0.0 0.4 0.4 8.8

t R le se ee et / lue lue s

8640 min Summer 0.733 0.0 62.5 4416 10080 min Summer 0.651 0.0 62.3 5152 15 min Winter 69.220 0.0 9.0 18 30 min Winter 46.082 0.0 14.1 32 60 min Winter 29.395 0.0 20.8 60 120 min Winter 18.205 0.0 27.1 100 180 min Winter 13.601 0.0 31.0 136 240 min Winter 11.003 0.0 33.9 172 360 min Winter 8.144 0.0 38.0 244 480 min Winter 6.575 0.0 41.2 314 600 min Winter 5.565 0.0 43.7 380 720 min Winter 4.855 0.0 45.8 446 960 min Winter 3.911 0.0 49.2 572 1440 min Winter 2.880 0.0 53.9 822 2160 min Winter 2.117 0.0 59.9 1188 2880 min Winter 1.701 0.0 63.2 1560 4320 min Winter 1.247 0.0 67.2 2292 5760 min Winter 1.000 0.0 70.9 3056 7200 min Winter 0.843 0.0 72.5 3712 8640 min Winter 0.733 0.0 73.4 4504 10080 min Winter 0.651 0.0 73.7 5240

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or PP-2 or 30yr.SRC

ime Area Diagram

otal Area (ha) 0.110

e s e

0 4 0.110

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or PP-2 or 30yr.SRC

Storage is nline Cover Level (m) 5.250

Porous Car Park Structure

Iniltration Coeicient Base (m/hr) 0.00000 Width (m) 17.6 Membrane Percolation (mm/hr) 1000 Length (m) 59.0 Ma Percolation (l/s) 288.4 Slope (1:) 0.0 Saety Factor 2.0 Depression Storage (mm) 5 Porosity 0.30 vaporation (mm/day) 3 Invert Level (m) 4.800 Membrane Depth (m) 0

Pipe utlo Control

Diameter (m) 0.100 ntry Loss Coeicient 0.500 Slope (1:) 150.0 Coeicient o Contraction 0.600 Length (m) 10.000 Upstream Invert Level (m) 4.800 Roughness k (mm) 0.600

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or ank or 30yr.SRC

ste utl el tutues

PP-1 or 30yr.SRC (None) (None) PP-2 or 30yr.SRC

Hal Drain ime : 393 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 3.127 0.127 0.0 3.4 3.4 78.5 30 min Summer 3.167 0.167 0.0 4.4 4.4 103.4 60 min Summer 3.210 0.210 0.0 5.3 5.3 129.9 120 min Summer 3.257 0.257 0.0 5.3 5.3 158.7 180 min Summer 3.284 0.284 0.0 5.3 5.3 175.4 240 min Summer 3.302 0.302 0.0 5.3 5.3 186.2 360 min Summer 3.321 0.321 0.0 5.3 5.3 198.5 480 min Summer 3.329 0.329 0.0 5.3 5.3 203.2 600 min Summer 3.332 0.332 0.0 5.3 5.3 205.2 720 min Summer 3.334 0.334 0.0 5.3 5.3 206.1 960 min Summer 3.333 0.333 0.0 5.3 5.3 205.7 1440 min Summer 3.324 0.324 0.0 5.3 5.3 199.8 2160 min Summer 3.299 0.299 0.0 5.3 5.3 184.8 2880 min Summer 3.271 0.271 0.0 5.3 5.3 167.6 4320 min Summer 3.221 0.221 0.0 5.3 5.3 136.7 5760 min Summer 3.191 0.191 0.0 5.1 5.1 117.7 7200 min Summer 3.171 0.171 0.0 4.5 4.5 105.5

t R le se ee et / lue lue s

15 min Summer 69.220 0.0 93.5 19 30 min Summer 46.082 0.0 129.4 33 60 min Summer 29.395 0.0 178.7 64 120 min Summer 18.205 0.0 224.7 124 180 min Summer 13.601 0.0 253.3 182 240 min Summer 11.003 0.0 274.2 242 360 min Summer 8.144 0.0 305.4 362 480 min Summer 6.575 0.0 329.3 466 600 min Summer 5.565 0.0 348.5 522 720 min Summer 4.855 0.0 364.7 586 960 min Summer 3.911 0.0 391.1 712 1440 min Summer 2.880 0.0 428.7 972 2160 min Summer 2.117 0.0 479.5 1364 2880 min Summer 1.701 0.0 511.3 1756 4320 min Summer 1.247 0.0 555.9 2464 5760 min Summer 1.000 0.0 593.5 3168 7200 min Summer 0.843 0.0 619.4 3896

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or ank or 30yr.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 3.155 0.155 0.0 4.1 4.1 95.8 10080 min Summer 3.143 0.143 0.0 3.8 3.8 88.0 15 min Winter 3.143 0.143 0.0 3.8 3.8 88.0 30 min Winter 3.188 0.188 0.0 5.0 5.0 116.2 60 min Winter 3.238 0.238 0.0 5.3 5.3 146.9 120 min Winter 3.292 0.292 0.0 5.3 5.3 180.6 180 min Winter 3.325 0.325 0.0 5.3 5.3 200.7 240 min Winter 3.347 0.347 0.0 5.3 5.3 214.1 360 min Winter 3.373 0.373 0.0 5.3 5.3 230.6 480 min Winter 3.386 0.386 0.0 5.3 5.3 238.6 600 min Winter 3.390 0.390 0.0 5.3 5.3 241.1 720 min Winter 3.389 0.389 0.0 5.3 5.3 240.3 960 min Winter 3.384 0.384 0.0 5.3 5.3 236.9 1440 min Winter 3.363 0.363 0.0 5.3 5.3 224.1 2160 min Winter 3.317 0.317 0.0 5.3 5.3 196.0 2880 min Winter 3.270 0.270 0.0 5.3 5.3 166.8 4320 min Winter 3.200 0.200 0.0 5.3 5.3 123.4 5760 min Winter 3.170 0.170 0.0 4.5 4.5 104.7 7200 min Winter 3.147 0.147 0.0 3.9 3.9 91.0 8640 min Winter 3.131 0.131 0.0 3.5 3.5 80.6 10080 min Winter 3.118 0.118 0.0 3.1 3.1 72.6

t R le se ee et / lue lue s

8640 min Summer 0.733 0.0 640.8 4616 10080 min Summer 0.651 0.0 658.3 5344 15 min Winter 69.220 0.0 106.5 19 30 min Winter 46.082 0.0 146.9 33 60 min Winter 29.395 0.0 202.0 62 120 min Winter 18.205 0.0 253.6 122 180 min Winter 13.601 0.0 285.7 182 240 min Winter 11.003 0.0 309.1 240 360 min Winter 8.144 0.0 344.1 356 480 min Winter 6.575 0.0 370.9 468 600 min Winter 5.565 0.0 392.5 572 720 min Winter 4.855 0.0 410.7 660 960 min Winter 3.911 0.0 440.2 762 1440 min Winter 2.880 0.0 482.3 1052 2160 min Winter 2.117 0.0 540.3 1468 2880 min Winter 1.701 0.0 576.4 1848 4320 min Winter 1.247 0.0 627.5 2508 5760 min Winter 1.000 0.0 670.4 3232 7200 min Winter 0.843 0.0 700.6 3968 8640 min Winter 0.733 0.0 725.8 4736 10080 min Winter 0.651 0.0 746.6 5440

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or ank or 30yr.SRC

ime Area Diagram

otal Area (ha) 0.617

e s e

0 4 0.617

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 30yr Date 12/04/2021 15:41 Designed by RM File Cascade 30yr.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or ank or 30yr.SRC

Storage is nline Cover Level (m) 5.000

Cellular Storage Structure

Invert Level (m) 3.000 Saety Factor 2.0 Iniltration Coeicient Base (m/hr) 0.00000 Porosity 0.95 Iniltration Coeicient Side (m/hr) 0.00000

et e e et e e

0.000 650.0 0.0 0.801 0.0 0.0 0.800 650.0 0.0

Pump utlo Control

Invert Level (m) 3.000

et ll/s et ll/s et ll/s et ll/s

0.200 5.3000 0.400 5.3000 0.600 5.3000 0.800 5.3000

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-1 or 100yr40cc.SRC

ste utl el tutues

(None) ank or 100yr40cc.SRC (None)

Hal Drain ime : 140 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 5.138 0.068 0.0 2.0 2.0 28.8 30 min Summer 5.163 0.093 0.0 3.3 3.3 39.7 60 min Summer 5.185 0.115 0.0 4.5 4.5 48.9 120 min Summer 5.199 0.129 0.0 4.9 4.9 55.1 180 min Summer 5.206 0.136 0.0 5.1 5.1 57.8 240 min Summer 5.208 0.138 0.0 5.1 5.1 58.8 360 min Summer 5.209 0.139 0.0 5.1 5.1 59.1 480 min Summer 5.207 0.137 0.0 5.1 5.1 58.3 600 min Summer 5.203 0.133 0.0 5.0 5.0 56.9 720 min Summer 5.200 0.130 0.0 4.9 4.9 55.3 960 min Summer 5.192 0.122 0.0 4.7 4.7 52.0 1440 min Summer 5.179 0.109 0.0 4.3 4.3 46.4 2160 min Summer 5.166 0.096 0.0 3.5 3.5 41.0 2880 min Summer 5.157 0.087 0.0 3.0 3.0 37.1 4320 min Summer 5.144 0.074 0.0 2.3 2.3 31.4 5760 min Summer 5.135 0.065 0.0 1.9 1.9 27.7 7200 min Summer 5.129 0.059 0.0 1.7 1.7 25.2

t R le se ee et / lue lue s

15 min Summer 125.353 0.0 26.1 18 30 min Summer 84.267 0.0 38.6 33 60 min Summer 54.074 0.0 54.4 60 120 min Summer 33.506 0.0 69.4 98 180 min Summer 24.949 0.0 78.4 130 240 min Summer 20.093 0.0 84.7 164 360 min Summer 14.773 0.0 94.0 232 480 min Summer 11.871 0.0 101.0 298 600 min Summer 10.010 0.0 106.6 364 720 min Summer 8.703 0.0 111.3 428 960 min Summer 6.973 0.0 118.8 556 1440 min Summer 5.093 0.0 129.3 794 2160 min Summer 3.711 0.0 142.4 1168 2880 min Summer 2.961 0.0 150.1 1528 4320 min Summer 2.150 0.0 159.7 2252 5760 min Summer 1.711 0.0 168.5 2992 7200 min Summer 1.432 0.0 172.9 3680

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-1 or 100yr40cc.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 5.125 0.055 0.0 1.5 1.5 23.6 10080 min Summer 5.123 0.053 0.0 1.3 1.3 22.4 15 min Winter 5.148 0.078 0.0 2.5 2.5 33.1 30 min Winter 5.176 0.106 0.0 4.1 4.1 45.2 60 min Winter 5.201 0.131 0.0 4.9 4.9 55.9 120 min Winter 5.217 0.147 0.0 5.3 5.3 62.7 180 min Winter 5.223 0.153 0.0 5.5 5.5 65.1 Flood Risk 240 min Winter 5.223 0.153 0.0 5.5 5.5 65.4 Flood Risk 360 min Winter 5.220 0.150 0.0 5.4 5.4 64.0 Flood Risk 480 min Winter 5.214 0.144 0.0 5.3 5.3 61.5 600 min Winter 5.208 0.138 0.0 5.1 5.1 58.6 720 min Winter 5.201 0.131 0.0 4.9 4.9 55.8 960 min Winter 5.189 0.119 0.0 4.6 4.6 50.6 1440 min Winter 5.173 0.103 0.0 3.9 3.9 43.7 2160 min Winter 5.158 0.088 0.0 3.0 3.0 37.4 2880 min Winter 5.148 0.078 0.0 2.5 2.5 33.1 4320 min Winter 5.133 0.063 0.0 1.9 1.9 27.0 5760 min Winter 5.126 0.056 0.0 1.5 1.5 23.9 7200 min Winter 5.122 0.052 0.0 1.3 1.3 22.0 8640 min Winter 5.119 0.049 0.0 1.1 1.1 20.7 10080 min Winter 5.116 0.046 0.0 1.0 1.0 19.6

t R le se ee et / lue lue s

8640 min Summer 1.240 0.0 176.1 4408 10080 min Summer 1.098 0.0 178.0 5144 15 min Winter 125.353 0.0 30.5 18 30 min Winter 84.267 0.0 44.4 32 60 min Winter 54.074 0.0 62.0 60 120 min Winter 33.506 0.0 78.8 110 180 min Winter 24.949 0.0 89.0 138 240 min Winter 20.093 0.0 96.0 176 360 min Winter 14.773 0.0 106.5 250 480 min Winter 11.871 0.0 114.4 320 600 min Winter 10.010 0.0 120.8 388 720 min Winter 8.703 0.0 126.1 454 960 min Winter 6.973 0.0 134.6 578 1440 min Winter 5.093 0.0 146.6 822 2160 min Winter 3.711 0.0 161.3 1192 2880 min Winter 2.961 0.0 170.2 1560 4320 min Winter 2.150 0.0 181.7 2292 5760 min Winter 1.711 0.0 191.9 2976 7200 min Winter 1.432 0.0 197.5 3680 8640 min Winter 1.240 0.0 201.8 4408 10080 min Winter 1.098 0.0 204.6 5240

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or PP-1 or 100yr40cc.SRC

Rainall Model FSR Winter Storms es Return Period (years) 100 Cv (Summer) 0.750 Region ngland and Wales Cv (Winter) 0.840 M5-60 (mm) 19.100 Shortest Storm (mins) 15 Ratio R 0.350 Longest Storm (mins) 10080 Summer Storms es Climate Change 40

ime Area Diagram

otal Area (ha) 0.157

e s e

0 4 0.157

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe Porous 1 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or PP-1 or 100yr40cc.SRC

Storage is nline Cover Level (m) 5.520

Porous Car Park Structure

Pipe utlo Control

Diameter (m) 0.100 ntry Loss Coeicient 0.500 Slope (1:) 150.0 Coeicient o Contraction 0.600 Length (m) 10.000 Upstream Invert Level (m) 5.070 Roughness k (mm) 0.600

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-2 or 100yr40cc.SRC

ste utl el tutues

(None) ank or 100yr40cc.SRC (None)

Hal Drain ime : 103 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 4.864 0.064 0.0 1.9 1.9 19.8 30 min Summer 4.887 0.087 0.0 3.0 3.0 27.1 60 min Summer 4.905 0.105 0.0 4.0 4.0 32.7 120 min Summer 4.917 0.117 0.0 4.6 4.6 36.4 180 min Summer 4.921 0.121 0.0 4.7 4.7 37.8 240 min Summer 4.923 0.123 0.0 4.7 4.7 38.2 360 min Summer 4.921 0.121 0.0 4.7 4.7 37.7 480 min Summer 4.917 0.117 0.0 4.6 4.6 36.6 600 min Summer 4.913 0.113 0.0 4.5 4.5 35.3 720 min Summer 4.909 0.109 0.0 4.3 4.3 34.1 960 min Summer 4.903 0.103 0.0 3.9 3.9 32.0 1440 min Summer 4.892 0.092 0.0 3.3 3.3 28.6 2160 min Summer 4.880 0.080 0.0 2.6 2.6 25.0 2880 min Summer 4.871 0.071 0.0 2.2 2.2 22.2 4320 min Summer 4.860 0.060 0.0 1.7 1.7 18.7 5760 min Summer 4.854 0.054 0.0 1.4 1.4 17.0 7200 min Summer 4.851 0.051 0.0 1.2 1.2 15.8

t R le se ee et / lue lue s

15 min Summer 125.353 0.0 18.7 18 30 min Summer 84.267 0.0 27.5 32 60 min Summer 54.074 0.0 38.2 60 120 min Summer 33.506 0.0 48.8 88 180 min Summer 24.949 0.0 55.1 122 240 min Summer 20.093 0.0 59.5 156 360 min Summer 14.773 0.0 66.0 222 480 min Summer 11.871 0.0 70.9 288 600 min Summer 10.010 0.0 74.8 350 720 min Summer 8.703 0.0 78.1 412 960 min Summer 6.973 0.0 83.4 538 1440 min Summer 5.093 0.0 90.8 780 2160 min Summer 3.711 0.0 99.6 1148 2880 min Summer 2.961 0.0 104.9 1504 4320 min Summer 2.150 0.0 111.7 2244 5760 min Summer 1.711 0.0 117.5 2944 7200 min Summer 1.432 0.0 120.5 3672

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or PP-2 or 100yr40cc.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 4.848 0.048 0.0 1.0 1.0 14.8 10080 min Summer 4.845 0.045 0.0 0.9 0.9 13.9 15 min Winter 4.873 0.073 0.0 2.3 2.3 22.8 30 min Winter 4.899 0.099 0.0 3.7 3.7 30.8 60 min Winter 4.919 0.119 0.0 4.6 4.6 37.2 120 min Winter 4.932 0.132 0.0 5.0 5.0 41.1 180 min Winter 4.935 0.135 0.0 5.0 5.0 42.0 240 min Winter 4.933 0.133 0.0 5.0 5.0 41.6 360 min Winter 4.927 0.127 0.0 4.8 4.8 39.6 480 min Winter 4.920 0.120 0.0 4.6 4.6 37.3 600 min Winter 4.913 0.113 0.0 4.4 4.4 35.1 720 min Winter 4.907 0.107 0.0 4.2 4.2 33.4 960 min Winter 4.898 0.098 0.0 3.6 3.6 30.5 1440 min Winter 4.885 0.085 0.0 2.9 2.9 26.4 2160 min Winter 4.871 0.071 0.0 2.2 2.2 22.1 2880 min Winter 4.862 0.062 0.0 1.8 1.8 19.3 4320 min Winter 4.853 0.053 0.0 1.3 1.3 16.5 5760 min Winter 4.848 0.048 0.0 1.1 1.1 15.0 7200 min Winter 4.844 0.044 0.0 0.9 0.9 13.7 8640 min Winter 4.840 0.040 0.0 0.8 0.8 12.6 10080 min Winter 4.838 0.038 0.0 0.7 0.7 11.7

t R le se ee et / lue lue s

8640 min Summer 1.240 0.0 122.7 4408 10080 min Summer 1.098 0.0 123.9 5144 15 min Winter 125.353 0.0 21.8 18 30 min Winter 84.267 0.0 31.6 32 60 min Winter 54.074 0.0 43.6 58 120 min Winter 33.506 0.0 55.4 94 180 min Winter 24.949 0.0 62.5 132 240 min Winter 20.093 0.0 67.4 168 360 min Winter 14.773 0.0 74.8 238 480 min Winter 11.871 0.0 80.3 304 600 min Winter 10.010 0.0 84.7 368 720 min Winter 8.703 0.0 88.4 428 960 min Winter 6.973 0.0 94.4 558 1440 min Winter 5.093 0.0 102.9 808 2160 min Winter 3.711 0.0 112.9 1172 2880 min Winter 2.961 0.0 119.1 1532 4320 min Winter 2.150 0.0 127.1 2252 5760 min Winter 1.711 0.0 133.9 2944 7200 min Winter 1.432 0.0 137.7 3752 8640 min Winter 1.240 0.0 140.6 4496 10080 min Winter 1.098 0.0 142.6 5144

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or PP-2 or 100yr40cc.SRC

ime Area Diagram

otal Area (ha) 0.110

e s e

0 4 0.110

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe Porous 2 Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:40 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or PP-2 or 100yr40cc.SRC

Storage is nline Cover Level (m) 5.250

Porous Car Park Structure

Pipe utlo Control

Diameter (m) 0.100 ntry Loss Coeicient 0.500 Slope (1:) 150.0 Coeicient o Contraction 0.600 Length (m) 10.000 Upstream Invert Level (m) 4.800 Roughness k (mm) 0.600

©1982-2020 Innovyze I&L Consultants (Dubai) Page 1 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:39 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or ank or 100yr40cc.SRC

ste utl el tutues

PP-1 or 100yr40cc.SRC (None) (None) PP-2 or 100yr40cc.SRC

Hal Drain ime : 874 minutes.

t ttus et eel et ltt tl utl lue l/s l/s l/s

15 min Summer 3.232 0.232 0.0 5.3 5.3 143.5 30 min Summer 3.315 0.315 0.0 5.3 5.3 194.5 60 min Summer 3.416 0.416 0.0 5.3 5.3 256.7 120 min Summer 3.527 0.527 0.0 5.3 5.3 325.2 180 min Summer 3.592 0.592 0.0 5.3 5.3 365.3 240 min Summer 3.635 0.635 0.0 5.3 5.3 392.2 360 min Summer 3.695 0.695 0.0 5.3 5.3 429.3 480 min Summer 3.734 0.734 0.0 5.3 5.3 453.4 600 min Summer 3.757 0.757 0.0 5.3 5.3 467.2 720 min Summer 3.767 0.767 0.0 5.3 5.3 473.9 960 min Summer 3.768 0.768 0.0 5.3 5.3 474.1 1440 min Summer 3.751 0.751 0.0 5.3 5.3 463.9 2160 min Summer 3.714 0.714 0.0 5.3 5.3 440.9 2880 min Summer 3.670 0.670 0.0 5.3 5.3 413.6 4320 min Summer 3.577 0.577 0.0 5.3 5.3 356.1 5760 min Summer 3.488 0.488 0.0 5.3 5.3 301.4 7200 min Summer 3.409 0.409 0.0 5.3 5.3 252.6

t R le se ee et / lue lue s

15 min Summer 125.353 0.0 182.3 19 30 min Summer 84.267 0.0 249.5 52 60 min Summer 54.074 0.0 341.8 114 120 min Summer 33.506 0.0 426.7 186 180 min Summer 24.949 0.0 477.7 240 240 min Summer 20.093 0.0 513.3 288 360 min Summer 14.773 0.0 565.9 376 480 min Summer 11.871 0.0 605.2 484 600 min Summer 10.010 0.0 636.1 602 720 min Summer 8.703 0.0 661.2 722 960 min Summer 6.973 0.0 698.9 914 1440 min Summer 5.093 0.0 737.9 1144 2160 min Summer 3.711 0.0 860.0 1528 2880 min Summer 2.961 0.0 912.1 1928 4320 min Summer 2.150 0.0 984.6 2720 5760 min Summer 1.711 0.0 1045.8 3464 7200 min Summer 1.432 0.0 1088.4 4184

©1982-2020 Innovyze I&L Consultants (Dubai) Page 2 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:39 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Summary o Results or ank or 100yr40cc.SRC

t ttus et eel et ltt tl utl lue l/s l/s l/s

8640 min Summer 3.343 0.343 0.0 5.3 5.3 211.7 10080 min Summer 3.289 0.289 0.0 5.3 5.3 178.4 15 min Winter 3.261 0.261 0.0 5.3 5.3 161.2 30 min Winter 3.358 0.358 0.0 5.3 5.3 220.9 60 min Winter 3.474 0.474 0.0 5.3 5.3 292.7 120 min Winter 3.600 0.600 0.0 5.3 5.3 370.4 180 min Winter 3.674 0.674 0.0 5.3 5.3 416.1 240 min Winter 3.724 0.724 0.0 5.3 5.3 447.0 360 min Winter 3.793 0.793 0.0 5.3 5.3 489.9 480 min Winter 5.024 2.024 0.0 5.3 5.3 519.1 FLD 600 min Winter 5.042 2.042 0.0 5.3 5.3 537.6 FLD 720 min Winter 5.053 2.053 0.0 5.3 5.3 548.0 FLD 960 min Winter 5.058 2.058 0.0 5.3 5.3 553.8 FLD 1440 min Winter 5.041 2.041 0.0 5.3 5.3 536.3 FLD 2160 min Winter 5.006 2.006 0.0 5.3 5.3 501.4 FLD 2880 min Winter 3.743 0.743 0.0 5.3 5.3 458.8 4320 min Winter 3.596 0.596 0.0 5.3 5.3 368.0 5760 min Winter 3.459 0.459 0.0 5.3 5.3 283.4 7200 min Winter 3.343 0.343 0.0 5.3 5.3 211.8 8640 min Winter 3.255 0.255 0.0 5.3 5.3 157.4 10080 min Winter 3.201 0.201 0.0 5.3 5.3 124.3

t R le se ee et / lue lue s

8640 min Summer 1.240 0.0 1124.8 4920 10080 min Summer 1.098 0.0 1154.3 5552 15 min Winter 125.353 0.0 206.0 19 30 min Winter 84.267 0.0 280.1 73 60 min Winter 54.074 0.0 384.6 136 120 min Winter 33.506 0.0 479.5 208 180 min Winter 24.949 0.0 536.3 264 240 min Winter 20.093 0.0 575.9 310 360 min Winter 14.773 0.0 633.8 396 480 min Winter 11.871 24.9 676.5 484 600 min Winter 10.010 43.4 709.3 596 720 min Winter 8.703 53.8 735.1 708 960 min Winter 6.973 59.6 770.8 926 1440 min Winter 5.093 42.1 790.8 1256 2160 min Winter 3.711 7.2 966.2 1644 2880 min Winter 2.961 0.0 1025.1 2076 4320 min Winter 2.150 0.0 1106.9 2900 5760 min Winter 1.711 0.0 1176.9 3688 7200 min Winter 1.432 0.0 1225.8 4392 8640 min Winter 1.240 0.0 1267.5 4984 10080 min Winter 1.098 0.0 1302.0 5448

©1982-2020 Innovyze I&L Consultants (Dubai) Page 3 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:39 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Rainall Details or ank or 100yr40cc.SRC

ime Area Diagram

otal Area (ha) 0.617

e s e

0 4 0.617

©1982-2020 Innovyze I&L Consultants (Dubai) Page 4 29-31 Castle Street Solent Road High Wycombe ank Buckinghamshire, HP13 6RU 100yr40cc Date 12/04/2021 15:39 Designed by RM File Cascade 100yr40.CAS Checked by IL Innovyze Source Control 2020.1.3

Cascade Model Details or ank or 100yr40cc.SRC

Storage is nline Cover Level (m) 5.000

Cellular Storage Structure

Invert Level (m) 3.000 Saety Factor 2.0 Iniltration Coeicient Base (m/hr) 0.00000 Porosity 0.95 Iniltration Coeicient Side (m/hr) 0.00000

et e e et e e

0.000 650.0 0.0 0.801 0.0 0.0 0.800 650.0 0.0

Pump utlo Control

Invert Level (m) 3.000

et ll/s et ll/s et ll/s et ll/s

0.200 5.3000 0.400 5.3000 0.600 5.3000 0.800 5.3000