Strategic Flood Risk Assessment for the Surrey Minerals Plan

Strategic Flood Risk Assessment Report

Aggregates Recycling DPD (Submission Version)

August 2011

Contents

Page

Level 1 Strategic Flood Risk Assessment Checklist iii

Abbreviations & Acronyms iii

Chapter 1 Introduction to the Strategic Flood Risk Assessment 1 1.1 Introduction 1 1.2 The requirement for SFRA of land use plans 1 1.3 The requirements of PPS 25 1 1.4 Status of SFRA work in Surrey 3 1.5 Catchment flood management planning for rivers in Surrey 4 1.6 Sources of information used in the SFRA 4 1.7 Types of flooding addressed in the SFRA 5

Chapter 2 The Addlestone Bourne, Cut & Emm Brook CFMP 6 2.1 Introduction 6 2.2 Flooding from rivers 6 2.3 Flooding from the land 6 2.4 Flooding from groundwater 7 2.5 Flooding from sewers & drains 7 2.6 Flooding from reservoirs, canals & other artificial sources 7 2.7 Conclusions for the CFMP & the Aggregates Recycling DPD 7

Chapter 3 The Byfleet & Weybridge CFMP 8 3.1 Introduction 8 3.2 Flooding from rivers 8 3.3 Flooding from the land 8 3.4 Flooding from groundwater 9 3.5 Flooding from sewers & drains 9 3.6 Flooding from reservoirs, canals & other artificial sources 10 3.7 Conclusions for the CFMP & the Aggregates Recycling DPD 10

Chapter 4 The Colne CFMP 11 4.1 Introduction 11 4.2 Flooding from rivers 11 4.3 Flooding from the land 11 4.4 Flooding from groundwater 12 4.5 Flooding from sewers & drains 12 4.6 Flooding from reservoirs, canals & other artificial sources 12 4.7 Conclusions for the CFMP & the Aggregates Recycling DPD 13

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Chapter 5 The Lower Thames CFMP 14 5.1 Introduction 14 5.2 Flooding from rivers 14 5.3 Flooding from the land 16 5.4 Flooding from groundwater 16 5.5 Flooding from sewers & drains 17 5.6 Flooding from reservoirs, canals & other artificial sources 18 5.7 Conclusions for the CFMP & the Aggregates Recycling DPD 18

Chapter 6 The Lower, Middle & Upper River Mole CFMP 19 6.1 Introduction 19 6.2 Flooding from rivers 19 6.3 Flooding from the land 20 6.4 Flooding from groundwater 20 6.5 Flooding from sewers & drains 20 6.6 Flooding from reservoirs, canals & other artificial sources 21 6.7 Conclusions for the CFMP & the Aggregates Recycling DPD 21

Chapter 7 The Rural Wey CFMP 22 7.1 Introduction 22 7.2 Flooding from rivers 22 7.3 Flooding from the land 23 7.4 Flooding from groundwater 23 7.5 Flooding from sewers & drains 23 7.6 Flooding from reservoirs, canals & other artificial sources 24 7.7 Conclusions for the CFMP & the Aggregates Recycling DPD 24

Chapter 8 Guidance for Site Specific Flood Risk Assessment (FRA) 25 8.1 Introduction 25 8.2 FRA requirements for Aggregates Recycling DPD sites 25 8.3 Environment Agency advice on the content of site specific FRA 26 8.4 Advice on the content of site specific FRA from the PPS25 Practice Guide 27

Bibliography 31

The following are separate documents:

Appendix 1 Flood Risk Maps

Appendix 2 Sequential Test

Appendix 3 Groundwater & Non-Fluvial Flooding Information

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Level 1 Strategic Flood Risk Assessment Checklist

Outputs of a Level 1 Strategic Flood Risk Assessment

A Level 1 SFRA should contain: Location of relevant information within the SFRA report

Plans showing the LPA area, main rivers, ordinary watercourses & flood zones, including the functional floodplain where appropriate, across the LPA area as See Appendix 1 defined in table D1 of PPS 25, as well as all allocated development sites.

An assessment of the implications of climate change for flood risk at allocated development sites over an See relevant maps in Appendix 1 appropriate time period, if this has not been factored into the plans above.

Areas at risk of flooding from sources other than the rivers See Chapters 2 to 7 and the sea.

The location of any flood risk management measures, including both infrastructure and the coverage of flood See Chapters 2 to 7 warning systems.

Locations where additional development may significantly This issue is most appropriately addressed at the site specific increase flood risk elsewhere. FRA level in consultation with the Environment Agency.

Guidance on the preparation of FRAs for allocated See Chapter 8 development sites.

Guidance on the likely applicability of different sustainable This issue is most appropriately addressed at the site specific drainage systems (SuDS) techniques for managing surface FRA level in consultation with the Environment Agency. water run-off at key development sites.

Abbreviations & Acronyms

DCLG Department for Communities & Local Government Defra Department for Environment, Food & Rural Affairs DPD Development Plan Document EU European Union FRA Flood risk assessment GIS Geographical information systems LDD Local Development Document LDF Local Development Framework LPA Local planning authority ODPM Office of the Deputy Prime Minister PPS 25 Planning Policy Statement 25 SAC Special Area for Conservation (designated under the EU Habitats Directive) SFRA Strategic flood risk assessment SPA Special Protection Area (designated under the EU Birds Directive) SPZ Source Protection Zone SSSI Site of Special Scientific Interest STW Sewage treatment works SuDS Sustainable drainage systems UKCIP United Kingdom Climate Impacts Programme Flood Zone 1 Areas of land at risk fluvial flooding less frequently than once in 1,000 years. Flood Zone 2 Areas of land at risk of a 1 in 1,000 year fluvial flood event Flood Zone 3 (3a) Areas of land at risk of a 1 in 100 year fluvial flood event Flood Zone 3b Areas of land at risk of a 1 in 20 year fluvial flood event

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Chapter 1: Introduction to the Strategic Flood Risk Assessment

1.1 Introduction

The purpose of this chapter is to outline the way in which the strategic flood risk assessment (SFRA) for the submission version of the Aggregates Recycling Development Plan Document (DPD) (which will form part of the Surrey Minerals Plan) has been prepared. The SFRA is informed by work on the issue of flooding undertaken by the district and borough councils within Surrey.

The Aggregates Recycling DPD, once adopted and in combination with the Core Strategy DPD and the Primary Aggregates DPD, will provide the strategic context for the provision of temporary and permanent aggregate recycling facilities in Surrey up to the year 2026.

1.2 The Requirement for SFRA of Land Use Plans

The requirement for land use plans to undergo SFRA derives from Planning Policy Statement (PPS) 25: Development & Flood Risk, published in December 2006. The purpose of SFRA is to enable the plan-making process to steer new development away from areas that are known, or have the potential, to be at risk of flooding from a range of sources.

SFRA focuses on a single issue, whilst development plan preparation has to address a wide range of concerns, and promote the achievement of combined environmental, economic and social objectives1. The PPS 25 Practice Guide (published in June 2008) advises that in preparing Local Development Documents (LDDs), planning authorities should seek to maintain a balance between the issue of flood risk and wider sustainable development concerns2.

Following changes to the planning system introduced under the Planning & Compulsory Purchase Act 2004, minerals and waste planning authorities are required to prepare development frameworks for mineral production and waste management in accordance with the procedures that apply to local development frameworks (LDFs). The PPS 25 Practice Guide advises that minerals and waste planning authorities (MWPAs) should take account of any relevant SFRAs that are available3. The practice guide acknowledges the particular issues that MWPAs can face, especially in respect of mineral extraction, and advises that the sequential test should be applied so far as possible4.

The Aggregates Recycling DPD SFRA is based on the Surrey Minerals Plan SFRA, published in November 2009, which was informed by work undertaken on flooding by the districts and boroughs in Surrey, and by the Environment Agency’s on Catchment Flood Management Plans (CFMPs).

1.3 The Requirements of PPS 25

The PPS 25 practice guide identifies two levels of SFRA that can be produced in respect of LDFs. • A Level 1 SFRA should provide sufficient information to enable the LPA to apply the sequential test (see section 1.3.3) and determine whether the exception test (see 1.3.4) may need to be used (in which case a Level 2 SFRA will be required). A Level 1 SFRA should be a desk based exercise and make use of existing information5. The main outputs of a Level 1 SFRA are: − Plans showing the LPA area, main rivers, ordinary watercourses and flood zones, including the functional floodplain where appropriate, and allocated development sites. − An assessment of the implications of climate change for flood risk at allocated development sites over an appropriate time period. − Areas at risk of flooding from sources other than the rivers and the sea. − The location of any flood risk management measures, including both infrastructure and the coverage of flood warning systems. − Locations where additional development may significantly increase flood risk elsewhere.

1 Office of the Deputy Prime Minister (ODPM) (2005) PPS 1: Delivering Sustainable Development, Paragraph 13(i). HMSO, London. 2 Department of Communities & Local Government (DCLG) (2008) PPS 25: Development & Flood Risk Practice Guide, p.9, paragraph 2.8. DCLG, London 3 Ibid, p.15, Paragraph 2.24. 4 Ibid, p.15, Paragraph 2.27. 5 Ibid. Paragraph 3.43, p.45.

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− Guidance on the preparation of FRAs for allocated development sites. − Guidance on the likely applicability of different sustainable drainage systems (SuDS) techniques for managing surface water run-off at key development sites. • A Level 2 SFRA should take account of the presence of flood management measures, such as flood defences, and provide information about the precise nature of the flood hazard6. The Level 2 SFRA should look at the variation of flood risk within flood zones protected by flood defences, and draw conclusions and make recommendations for each site allocated for development7. The main outputs of a Level 2 SFRA are: − An appraisal of the current condition of flood defence infrastructure and of likely future policy with regard to its maintenance and upgrade. − An appraisal of the probability and consequences of overtopping or failure of flood risk management infrastructure, including an appropriate allowance for climate change. − Maps showing the distribution of flood risk across flood zones. − Guidance on the application of the Exception Test (para D9 of PPS 25 & Ch. 3 of the Practice Guide). − Guidance on the preparation of FRA for sites of varying risk across the flood zone.

The Aggregates Recycling DPD SFRA is a Level 1 assessment, so far as is possible given the variations in the information available about flood risk at the borough and district levels.

1.3.1 Sensitivity of development to flood risk The guidance in PPS 25 categorises different forms of development in terms of their sensitivity to flood risk, based on the risks to people and the need for certain types of infrastructure and facilities to remain operational during flood events8. The types of development covered by the Surrey Minerals Plan and the Aggregates Recycling DPD fall within the following vulnerability classes. • Less vulnerable development – Waste treatment (except landfill & hazardous waste facilities); Minerals working & processing (except for sand & gravel working). Such development is acceptable, according to PPS 25 in all fluvial flood risk zones, excepting Zone 3b (1 in 20 year flood event). • Water compatible development – sand & gravel workings. Such development is acceptable, according to PPS 25 in all fluvial flood risk zones.

1.3.2 The sequential test The sequential test is a risk based assessment that should be applied at all stages of the planning process, and is intended to steer development away from areas that are subject to flooding, and towards areas of least risk (i.e. Zone 1)9. Appendix 2 to the Aggregates Recycling DPD SFRA applies the sequential test to the 84 sites that were considered for inclusion in the DPD.

The sequential test is based on the Environment Agency’s definition of flood zones (see below), which deal with the probability of flooding from rivers or the sea. The Environment Agency’s indicative coastal and fluvial flood risk maps do not take account of the effects of any existing flood defences. • Flood risk Zone 1 – areas with the lowest probability of flooding or any area of land that has not been classified as subject to a Zone 2 and Zone 3 flood risk. • Flood risk Zone 2 – areas with a medium probability of flooding from rivers or the sea. • Flood risk Zone 3 – areas with a high probability of flooding from rivers or the sea.

When there are no reasonable alternatives available within Zone 1, areas within Zone 2 can be considered so long as the flood risk vulnerability of the sites proposed is taken into account in the decision making process (see PPS 25, Table D2), and where necessary the exception test is applied (see section 1.3.4). Only where no reasonable alternatives are available within Zone 1 and Zone 2 should sites within Zone 3 be considered, with due account being taken of the flood risk vulnerability of the development concerned and use of the exception test where relevant. New development should always be guided to the sites with the lowest probability of flooding, with the flood ‘vulnerability’ of the development matching the associated risk (e.g. higher vulnerability uses located on parts of the site with the lowest probability of flooding).

6 DCLG (2008) PPS 25: Development & Flood Risk Practice Guide, paragraph 3.50, p.48. DCLG, London. 7 Ibid, paragraph 3.59, p.52. 8 ODPM (2006) PPS 25: Development & Flood Risk. Annex D, Table D.2: flood risk vulnerability classification, pp.25-26. ODPM: London. 9 DCLG (2006) PPS 25: Development & Flood Risk – Annex D: The Sequential Test & the Exception Test. Paragraph D1, p.21. TSO: London.

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1.3.3 The exception test The exception test aids the decision making process by determining whether a particular development would be permitted within certain fluvial flood risk zones. In order to pass the exception test a development must: “ (a) …provide wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA ...; (b)…be on developable previously developed land or, if it is not on previously developed land, that there are no reasonable alternative sites on developable previously-developed land; and (c)… be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall.” PPS 25, Annex D, paragraph D9

The exception test should only be used subsequent to the sequential test and in the circumstances shown in Table 1.1. The test must not be used to justify highly vulnerable development, in Zone 3a or less vulnerable, more vulnerable and highly vulnerable development in Zone 3b.

Table 1.1: Circumstances requiring the exception test

Fluvial Flood Essential Highly Water compatible More Vulnerable Less Vulnerable Risk Zones Infrastructure Vulnerable

Zone 1 Acceptable Acceptable Acceptable Acceptable Acceptable

Use exception Zone 2 Acceptable Acceptable Acceptable Acceptable test

Use exception Use exception Zone 3a Acceptable Not acceptable Acceptable test test

Use exception Zone 3b Acceptable Not acceptable Not acceptable Not acceptable test

Aggregate recycling falls into the less vulnerable development category, which is not subject to the exception test.

1.4 Status of SFRA work in Surrey

The PPS 25 Practice Guide advises that MWPAs should make use of any available SFRAs that relate to the area covered by their proposals (e.g. relevant district or borough SFRAs) in the development of their plans and the application of the sequential approach to site selection. SFRAs have been published by 10 of the 11 boroughs and districts in Surrey, in support of their work on their LDFs.

The Aggregates Recycling DPD identifies 16 sites that could be developed as permanent or temporary aggregate recycling facilities up to the year 2026. The proposed sites are distributed around 6 of the 11 districts and boroughs in the county. The assessment of flood risk for the Aggregates Recycling DPD draws on the SFRAs for the 6 boroughs in which the proposed sites are located.

Table 1.2: SFRA status in Surrey & distribution of sites in the Aggregates Recycling DPD

Borough SFRA Status Aggregates Recycling DPD Sites

Guildford BC SFRA (January 2009) 1 aggregate recycling site

Reigate & Banstead BC SFRA (December 2007) 2 aggregate recycling sites lo

4 primary aggregate sites with aggregate recycling Runnymede BC SFRA (May 2009) 3 aggregate recycling sites 2 primary aggregate sites with aggregate recycling Spelthorne BC SFRA (December 2006) 3 aggregate recycling sites

Waverley BC Draft SFRA (2006) 1 aggregate recycling site

River Bourne SFRA (March 2007) Woking BC 1 aggregate recycling site River Wey SFRA (February 2007)

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1.5 Catchment Flood Management Planning for Rivers in Surrey

The area covered by the Aggregates Recycling DPD SFRA is defined by the border of the county (see Map 1 in Appendix 1). A number of main rivers arise in or traverse parts of the county, including the Thames, the Wey, the Blackwater River, the Mole, the Addlestone Bourne, the Colne and the Rythe (see Map 2 in Appendix 1). Those rivers have areas of flood risk associated with them that have been mapped and modelled by the Environment Agency as the basis for predicting the likely risk of future fluvial flood events (see Maps 3 and 4 in Appendix 1).

The Environment Agency produces Catchment Flood Management Plans (CFMPs) for the river catchments that it manages. The CFMPs identify the factors that contribute to the risk of flooding occurring within catchments and the ways in which those flood risks might be most appropriately managed over the medium to long term. There are a number of CFMPs that cover river catchments in Surrey in which the sites identified in the Aggregates Recycling DPD are located. • Addlestone Bourne, Cut & Emm Brook CFMP – 1 proposed aggregate recycling site • Byfleet & Weybridge CFMP – 2 proposed primary aggregate working & aggregate recycling sites • Colne CFMP – 2 proposed aggregate recycling sites • Lower Thames CFMP – 4 proposed primary aggregate working & aggregate recycling sites; 4 proposed aggregate recycling sites • Lower, Middle & Upper River Mole CFMP – 1 proposed primary aggregate working & aggregate recycling site; 3 proposed aggregate recycling sites • Rural Wey CFMP – 2 proposed aggregate recycling sites

The Aggregates Recycling DPD SFRA is structured around the 6 CFMPs in which the sites identified in the DPD are located.

1.6 Sources of information used in the SFRA

The Aggregates Recycling DPD SFRA draws on a number of different sources of information. • Environment Agency indicative flood risk maps, based on datasets held by Surrey County Council. • Environment Agency detailed flood risk models for a number of major rivers in Surrey: - The Lower Thames from Windsor to Walton on Thames (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The Upper Mole Catchment at Horley (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The River Rythe (1 in 100 year event (Zone 3)). - The Addlestone Bourne (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The Lower Wey (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The Hoe Stream (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The River Send (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The Upper Wey (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). - The South Wey Extension (1 in 20 year event (the functional floodplain), 1 in 100 year event (Zone 3) and 1 in 100 year + 20% for climate change event). • Information provided by the Environment Agency about locations at which incidents of non-fluvial flooding have been reported to them by members of the public between 2000 and 2005. • The Guildford BC SFRA (Capita Symonds), January 2009, covering the entire borough. • The Reigate & Banstead BC SFRA (Jacobs), December 2007, covering the entire borough. • The Runnymede BC SFRA (Entec), May 2009, covering the entire borough. • The Spelthorne BC SFRA (Jacobs), December 2006, covering the entire borough.

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• The Draft Waverley BC Core Strategy FRA, October 2006, covering the entire borough. • The Addlestone Bourne SFRA (Capita Symonds for Woking BC &Surrey Heath BC), March 2007. • The River Wey SFRA (Capita Symonds for Woking BC), February 2007. • The Surrey Minerals Plan SFRA (including the draft Aggregates Recycling DPD), November 2009.

1.7 Types of flooding addressed in the SFRA

The SFRA addresses, so far as possible based on the available information, five of the six types of flooding listed below for each of the sites identified in the Aggregates Recycling DPD. • Flooding from Rivers: Rivers flood when the volume of water exceeds the flow capacity of the watercourse, usually resulting in the spread of water into the rivers natural defence to this, the flood plain, which regulates the flow. The PPS 25 Practice Guide identifies the following forms of fluvial flooding10: (a) inundation of floodplains from rivers & watercourses; (b) inundation of areas outside the natural floodplain due to influence of bridges, embankments & other features that artificially raise water levels; (c) overtopping of defences; breaching of defences; blockages of culverts; blockages of flood channels or flood corridors. • Flooding from the Sea: Flooding from the sea affects low-lying land in coastal areas & estuaries & is generally a result of a combination of storm surges & very high tides. Such forms of flooding can be particularly dangerous in areas where coastal defences are breached, for example by storm damage. The risks of flooding from the sea are expected to become increasingly prolific in the future as a consequence of the effects of climate change. The risk of flooding from the sea is not relevant to Surrey, as the county has no coastline, and is therefore not covered by the SFRA. • Flooding from the Land: Flooding from land occurs when it is not possible for surface water, typically the result of very intense periods of rainfall, to effectively drain into the sewerage system or to groundwater. The built environment can significantly affect this by increasing the use of impervious areas (e.g. concrete & tarmac). This can lead to changes in the rates & volumes of surface water run off. • Flooding from Groundwater: Flooding from groundwater generally occurs in low-lying areas as the result of groundwater rising above surface elevations. This occurs in areas of permeable rocks or aquifers, which can be extensive & range across large regions e.g. sandstone, or be localised in the form of sands or river gravels. Groundwater levels typically increase during periods of higher rainfall & recede in periods of lower rainfall. • Flooding from Sewers & Drains: In urban areas rain-water drains into sewers or combined sewers (which contain both surface water & waste water). Flooding can occur here when these sewers are overwhelmed by heavy rainfall or as a result of blockages or inadequate capacity. When this occurs (especially in combined sewers) this can result in a high risk of flooding to property with contaminated water (surface runoff & raw sewage) & rivers from the discharge of combined sewer overflows. • Flooding from Reservoirs, Canals, & Other Artificial Sources: Artificial sources of flooding include reservoirs, canals, & redundant industrial processes including mining. Reservoir or canal flooding can occur as a result of a facility being overwhelmed or as a result of dam or bank failure. The latter, if occurring catastrophically could present significant risks to human life.

10 DCLG (2007). PPS 25: Development & Flood Risk Practice Guide’. Figure 3.2, p.34. DCLG: London.

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Chapter 2: The Addlestone Bourne, Cut & Emm Brook CFMP

2.1 Introduction

According to the Environment Agency’s guidance for the Addlestone Bourne, Cut & Emm Brook CFMP the area comprises newer and expanding areas of urban development that are often located towards the headwaters of river catchments. The main messages for the area include. • Extensive modification of the river systems (especially the Cut and Emm Brook) has taken place as development has progressed. The watercourses have been engineered (i.e. culverted and straightened) to enable them to carry specific predicted flows, but when those design flows are exceeded rapid flooding of the surrounding areas can occur. • The rivers do not feature in the landscape, and are often hidden from view, making blockages from accumulations of debris a frequent problem. There are problems with fly-tipping into dry watercourses during low-flow periods, which creates the potential for flooding (due to blockages) once the water returns. • Episodes of intense rainfall (particularly during the summer) can, periodically, lead to overloading of the surface water and sewerage systems, which coupled with increased run-off rates as a consequence of development can result in flooding.

There is one site proposed in the Aggregates Recycling DPD located within the area covered by the Addlestone Bourne, Cut & Emm Brook CFMP policy unit, at Martyrs Lane, near Woking in Woking BC.

This chapter draws on the Addlestone Bourne SFRA, and Environment Agency fluvial flood risk modelling for the Addlestone Bourne.

2.2 Flooding from Rivers

2.2.1 Findings from Addlestone Bourne SFRA The Addlestone Bourne SFRA reports that the river and its tributary, the Hale Bourne, are located to the west of London, drain into the Chertsey Bourne via the Woburn Park Stream, have a catchment area of approximately 90 km2, and have a number of smaller tributaries including Chobham Park Brook, Clappers Brook, Knaphill Brook, Lightwater Stream, Parley Brook and Windlesham Ditch11. The SFRA mapped the areas within the catchment of the Addlestone Bourne subject to Zone 3 and Zone 2 fluvial flood risk.

The mapping in the Addlestone Bourne SFRA places the Martyrs Lane site within an area of Zone 1 fluvial flood risk. The River Bourne is located to the north of the site, but Zone 2 and Zone 3 fluvial flood risk associated with the river does not extend as far south as the site.

2.2.2 Findings & conclusions for site(s) allocated in the Aggregates Recycling DPD Fluvial flood risk mapping for the Aggregates Recycling DPD, based on Environment Agency data, indicates that the Martyrs Lane site is located in an area of Zone 1 fluvial flood risk with areas of Zone 3 and Zone 2 fluvial flood risk to the north (Map 5.33a, Appendix 1). Under a climate change scenario (a 20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (Map 5.33b, Appendix 1).

Based on the fluvial flooding information in the Addlestone Bourne SFRA and provided by the Environment Agency, and taking account of the guidance in PPS25, it is concluded that the Martyrs Lane site is suitable for development as proposed in the Aggregates Recycling DPD.

2.3 Flooding from the Land

2.3.1 Findings from Addlestone Bourne SFRA The Addlestone Bourne SFRA does assess the risks of surface water flooding12, but advises that much of the area is undeveloped and therefore surface water runoff and drainage is not much altered from that which would be found under greenfield conditions13.

11 Capita Symonds (2007) Woking & Surrey Heath SFRA – Vol 2: Tech Rpt (Final). Para 5.2 & 5.3, p. 10. Woking BC & Surrey Heath BC. 12 Ibid, paragraph 9.7, p.25. 13 Ibid, Paragraph 9.1, p. 25.

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Non-fluvial flooding incidents reported to the Environment Agency for Woking BC included 5 cases of waterlogged or flooded gardens (January 2001 to May 2005), of which 2 were attributed to a pluvial source.

2.3.2 Findings & conclusions for site(s) allocated in the Aggregates Recycling DPD Any risks of surface water flooding arising from changes in land-cover associated with the development of the Martyrs Lane site as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The site is likely to require FRA, which should investigate options for surface water management (including use of sustainable drainage systems (SuDS)).

2.4 Flooding from Groundwater

2.4.1 Findings from Addlestone Bourne SFRA The Addlestone Bourne SFRA does not assess the risks of groundwater flooding. Non-fluvial flooding incidents reported to the Environment Agency for Woking BC included 5 cases of waterlogged or flooded gardens (January 2001 to May 2005), of which 2 were attributed to the emergence of springs.

2.4.2 Findings & conclusions for site(s) allocated in the Aggregates Recycling DPD Any risks of ground water flooding arising from changes in local hydrology associated with the development of an aggregate recycling facility at the Martyrs Lane site as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The site is likely to require FRA, which should investigate the risks of changes in hydrology and implications for groundwater emergence.

2.5 Flooding from Sewers & Drains

2.5.1 Findings from Addlestone Bourne SFRA The Addlestone Bourne SFRA does not assess the risks of flooding from sewers and drains.

2.5.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD The impact that the development of the Martyrs Lane site as proposed in the Aggregates Recycling DPD could have on the local sewer and foul water network would be most appropriately investigated at the planning application stage. The site is likely to require FRA, which should investigate the effects that the development may have on existing drainage capacity in the area.

2.6 Flooding from Reservoirs, Canals, & Other Artificial Sources

2.6.1 Findings from Addlestone Bourne SFRA The Addlestone Bourne SFRA considers14 the risks of flooding from the Basingstoke Canal, including a breach of the embankment, culvert failure and bypassing. The Basingstoke Canal embankment is considered to be inherently prone to failure, but the risk posed to the area is considered to be residual.

2.6.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD The development of the Martyrs Lane site near Woking as proposed in the Aggregates Recycling DPD would not affect the integrity of the Basingstoke Canal, or alter the level of flood risk attributed to it.

2.7 Conclusions for the CFMP & the Aggregates Recycling DPD

Based on the information provided by the Addlestone Bourne SFRA and the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of the Martyrs Lane site for development as an aggregate recycling facility is acceptable on flood risk grounds.

14 Capita Symonds (2007) Woking & Surrey Heath SFRA – Vol 2: Tech Rpt (Final).. Para 9.15 to 9.31, pp 27-29. Woking BC & Surrey Heath BC.

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Chapter 3: The Byfleet & Weybridge CFMP

3.1 Introduction

According to the Environment Agency’s guidance for the Byfleet & Weybridge CFMP the area is located in the downstream end of the River Wey catchment and is generally urban with no major river flood defences. The main messages for the area include. • Where possible options to reduce flood risk that are the most effective and sustainable in the long term will be progressed. Technically feasible defence options exist for most areas at risk but are often expensive to implement. • The areas at risk of flooding are often constrained historic towns, which will require adaptation of the urban environment to improve flood resilience and the location of new development in areas of lowest risk. • For large rivers it is not always possible to increase the flow capacity, the focus is on adaptation.

The Aggregates Recycling DPD proposes 2 sites in the area covered by the Byfleet & Weybridge CFMP, the Addlestone Quarry extension (Preferred Area A in the Primary Aggregates DPD), and Hamm Court Farm at Weybridge (Preferred Area C). Both sites are in the borough of Runnymede.

This chapter draws on the following sources of information Runnymede BC SFRA, and Environment Agency fluvial flood risk modelling for the River Wey.

3.2 Flooding from Rivers

3.2.1 Findings from Borough SFRA The Runnymede BC SFRA reports that at Addlestone, the area in which the two sites proposed in the Aggregates Recycling DPD are located, there are areas subject to Zone 2 and Zone 3 fluvial flood risk associated with the River Wey and the River Bourne15. The flood risk mapping reported in the Runnymede BC SFRA indicates that the proposed sites at Addlestone Quarry and Hamm Court Farm are subject to Zone 3a and Zone 3b fluvial flood risk from the River Wey. The River Wey bisects the Addlestone Quarry extension site, and runs to the east of the Hamm Court Farm site.

3.2.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Addlestone Quarry extension (Preferred Area A) – Fluvial flood risk mapping, based on Environment Agency data, indicates that the majority of the site is subject to Zone 3b fluvial flood risk (Map 5.1a, Appendix 1), and under a climate change scenario (20% increase in river levels) almost the entire site would be subject to Zone 3 fluvial flood risk (Map 5.1b, Appendix 1). Hamm Court Farm (Preferred Area C) – Fluvial flood risk mapping, based on Environment Agency data, indicates that the majority of the site is subject to either Zone 3b or Zone 3a fluvial flood risk (Map 5.3a, Appendix 1), and under a climate change scenario (20% increase in river levels) almost the entire site would be subject to Zone 3 fluvial flood risk (Map 5.3b, Appendix 1).

Based on the information provided in the borough SFRAs, and by the Environment Agency, and taking account of PPS 25 it is concluded that the proposed sites at Addlestone Quarry (Preferred Area A) and Hamm Court Farm (Preferred Area C) are suitable for development as temporary aggregate recycling facilities. In accordance with PPS 25, such facilities would need to be located those parts of the sites at least risk of fluvial flooding (i.e. Zone 1, Zone 2 or Zone 3a). Both sites are susceptible to high fluvial flood risk and would require detailed FRA at the planning application stage.

3.3 Flooding from the Land

3.3.1 Findings from Borough SFRA The Runnymede BC SFRA assesses the risks of surface water flooding16, with the majority of known incidents having occurred in Chertsey, Egham, Thorpe and Rowhill17. The SFRA reports on 50 non- fluvial flooding incidents, of which 4 were noted as having a surface water source.

15 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraph 5.3.24, p.34. Runnymede BC 16 Ibid. Chapter 6, pp.37-42. 17 Ibid, paragraph 6.1.2, p.37.

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Non-fluvial flooding incidents reported to the Environment Agency included 4 reports of waterlogged or flooded gardens or properties (June 2000 to January 2003) for Runnymede BC, of which none were attributed to surface water sources.

3.3.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks of surface water flooding arising from changes in land-cover associated with the development of temporary aggregate recycling facilities at the Addlestone Quarry extension (Preferred Area A) and Hamm Court Farm (Preferred Area C) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The sites would require site specific FRA at the planning application stage. The site specific FRAs should investigate the scope for effective surface water management (including the use of sustainable drainage systems).

3.4 Flooding from Groundwater

3.4.1 Findings from Borough SFRA The Runnymede BC SFRA assesses the risks of groundwater flooding18, reporting that the majority of known incidents have occurred in areas located within the River Thames floodplain and underlain by Thames Gravelsl19. The SFRA reports 50 non-fluvial flooding incidents, of which 1 had a groundwater source.

Non-fluvial flooding incidents reported to the Environment Agency included 4 incidents of waterlogged or flooded gardens or properties in Runnymede BC (June 2000 to January 20030, all of which were attributed to groundwater sources.

3.4.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks changes in local hydrology associated with the development of the Addlestone Quarry extension (Preferred Area A) and Hamm Court Farm (Preferred Area C) sites as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The sites would require site specific FRA at the planning application stage, which should investigate changes in hydrology associated with the development and potential effects on groundwater flood risk.

3.5 Flooding from Sewers & Drains

3.5.1 Findings from Borough SFRA The Runnymede BC SFRA assesses the risks of flooding from the drainage system20, reporting that the majority of known incidents are related to drainage and culverted watercourses21. The SFRA reports 50 non-fluvial flooding incidents, of which 38 were noted as having a drainage or sewer system source.

Non-fluvial flooding incidents reported to the Environment Agency included 4 reports of waterlogged or flooded gardens or properties (June 2000 to January 2003) in Runnymede BC, of which none could be attributed to drainage system sources.

3.5.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The impacts on the local sewer and foul water network of the development of the Addlestone Quarry extension (Preferred Area A) and Hamm Court Farm (Preferred Area C) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The sites are located in areas of Zone 3 fluvial flood risk, and each would encompass an area of more than 1 hectare requiring the submission of a FRA as part of the planning application.

18 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraphs 4.2.1 & 4.2.2, p.20. Runnymede BC 19 Ibid, paragraph 6.1.2, p.37. 20 Ibid. Paragraphs 4.1.3 & 4.1.6, pp.19-20. 21 Ibid, paragraph 4.1.3, p.19.

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3.6 Flooding from Reservoirs, Canals & Other Artificial Sources

3.6.1 Findings from Borough SFRA The Runnymede BC SFRA assesses the risks of flooding associated with the failure of water supply infrastructure22. The SFRA considers the risk from the Virginia Water reservoir and the Basingstoke Canal, and advises that for sites downstream of those sources the risks of their failure should be covered in site specific FRAs for individual developments.

3.6.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The development of the Addlestone Quarry extension (Preferred Area A) and Hamm Court Farm (Preferred Area C) as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on any parts of the water supply infrastructure located within the Byfleet & Weybridge CFMP area. The sites would require FRA as part of the planning application process, which should address the question of the potential effects of water supply infrastructure failure on the sites.

3.7 Conclusions for the CFMP & the Aggregates Recycling DPD

Based on the information presented in the Runnymede SFRA, and that provided by the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of the sites at Addlestone Quarry (Preferred Area A) and Hamm Court Farm (Preferred Area C) for development as temporary aggregate recycling facilities would be acceptable within areas subject to no greater than Zone 3a flood risk, so long as the processing facilities were located in the areas of lowest flood risk within the sites and appropriate compensation were made for the floodplain lost as a consequence of the development of aggregate recycling facilities.

22 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraphs 4.3.1-4.3.7, pp.20-22. Runnymede BC

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Chapter 4: The Colne CFMP

4.1 Introduction

According to the Environment Agency’s guidance for the Colne CFMP the area is generally urban, although a significant part is more rural in character, with some river defences in place. The main messages for the area include. • Redevelopment rates in some areas are very high and offer the opportunity to reduce the risk of and current resilience to flooding. Key to this would be making the urban environment more resilient, with a layout that offers a wider range of options for managing future flood risk and the impacts of climate change. • The existing river corridors provide opportunities for adaptation to the impacts of climate change, and need to be safeguarded from inappropriate development. A changing climate also means that existing defences will need to be adapted over time, with an increased emphasis on flood attenuation and storage capacity. • Episodes of intense rainfall (particularly during the summer) can, periodically, lead to overloading of the surface water and sewerage systems, which coupled with increased run-off rates as a consequence of development can result in flooding.

There is 1 site proposed in the Aggregates Recycling DPD located within the area covered by the Colne CFMP policy unit, at Stanwell Quarry near Stanwell in the borough of Spelthorne.

This chapter draws on the following sources of information, the Spelthorne BC SFRA, and Environment Agency fluvial flood risk modelling for the River Colne.

4.2 Flooding from Rivers

4.2.1 Findings from Borough SFRA The Spelthorne BC SFRA reports that the river Colne is particularly subject to flash flooding during periods of intense rainfall23. The SFRA maps the areas of land within the Colne catchment that are subject to Zone 3 and Zone 2 fuvial flood risk. According to the SFRA, the proposed site at Stanwell Quarry is subject to Zone 1 fluvial flood risk.

4.2.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD Mapping undertaken for the Aggregates Recycling DPD (see Map 5.37a, Appendix 1) based on Environment Agency data, indicates that the site is subject to Zone 1 fluvial flood risk. Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk to which the site is subject (Map 5.37b, Appendix 1).

Based on the fluvial flood risk information from the Spelthorne BC SFRA and provided by the Environment Agency, and taking account of the guidance set out in PPS25 it is concluded that the Stanwell Quarry site is suitable for development as proposed in the Aggregates Recycling DPD.

4.3 Flooding from the land

4.3.1 Findings from Borough SFRA The Spelthorne BC SFRA reports that flooding from surface water sources is known to be a problem during wet weather conditions24. The principal cause of surface water flooding is identified as the capacity of the Thames Gravels, that underlie much of the borough, to absorb excess surface water and the extensive use of soakaways for drainage. The SFRA advises that localised surface water flooding issues should be addressed through the design of development. Appendix A to the report gives an account of surface water conditions in the borough, and identifies Stanwell Moor as an area with a history of surface water flooding problems, particularly around Hithermoor Road.

Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC included 4 reports of flooded properties or waterlogged or flooded gardens between August 2001 and April 2005, of which none were attributed to surface water sources.

23 Jacobs (2006) Spelthorne BC Strategic Flood Risk Assessment. Paragraph 62, p.15. Spelthorne BC. 24 Ibid. Paragraphs 96-101, pp.20-21.

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4.3.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD Any risks of surface water flooding arising from changes in land-cover associated with the development of the Stanwell Quarry site as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The site would require the submission of a site specific FRA as part of the planning application, which should investigate the options for effective surface water management (including the scope for use of sustainable drainage systems).

4.4 Flooding from groundwater

4.4.1 Findings from Borough SFRA The Spelthorne BC SFRA assesses the risks of groundwater water flooding, most commonly encountered in the Staines, Shepperton and Sunbury and in areas underlain by Floodplain Gravels 25. The SFRA advises that the risk of groundwater flooding is variable and dependent on local conditions, and recommends that site specific FRAs include detailed work on the risks of groundwater flooding.

Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC included 4 reports of flooded properties or waterlogged or flooded gardens (August 2001 to April 2005), of which 2 were attributed to groundwater sources.

4.4.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD Any risks of groundwater flooding arising from changes in local hydrology associated with the development of the Stanwell Quarry site as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The site would require the submission of a site specific FRA as part of the planning application, which should investigate the likely effects of the development on hydrology and groundwater flood risk.

4.5 Flooding from Sewers & Drains

4.5.1 Findings from Borough SFRA The Spelthorne BC SFRA reviews the risks of flooding associated with sewers and drains, which most commonly arise in urban areas due to insufficient capacity in the existing drainage and sewerage networks26. The SFRA advises that the risk of flooding from sewers and drains is typically a localised problem best addressed through the design process for individual developments.

Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC included 4 reports of flooded properties or waterlogged or flooded gardens (August 2001 to April 2005), of which 1 was attributed to a problem with a soakaway.

4.5.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD The impacts on the local sewer and foul water network of the development of the Stanwell Quarry site as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. The site would require the submission of a site specific FRA as part of the planning application, which should investigate the implications of development of the existing drainage network.

4.6 Flooding from Reservoirs, Canals & Other Artificial Sources

4.6.1 Findings from Borough SFRA The Spelthorne BC SFRA includes a section on the risks of flooding associated with the failure of water supply infrastructure, it is reported that Thames Water were consulted on the risk of reservoir failure but that the strategically critical nature of the reservoirs precluded disclosure of the risk assessments27. The SFRA advises that the risk of flooding due to catastrophic failure of water supply infrastructure is considered to be minimal.

25 Jacobs (2006) Spelthorne BC Strategic Flood Risk Assessment. Paragraphs 102-105, p.21. Spelthorne BC 26 Ibid. Paragraph 98, p20. 27 Ibid. Paragraphs 106-109, p.22.

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4.6.2 Findings & Conclusions for site(s) allocated in the Aggregates Recycling DPD The development of the Stanwell Quarry site as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on any parts of the water supply infrastructure located within the Colne CFMP area. The site would require the submission of a site specific FRA as part of the planning application, which should investigate the implications of water supply infrastructure failure for the site.

4.7 Conclusions for the CFMP & the Aggregates Recycling DPD

Based on the information presented in the Spelthorne BC SFRA, and that provided by the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of Stanwell Quarry site for development as an aggregate recycling facility is acceptable on flood risk grounds.

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Chapter 5: The Lower Thames CFMP

5.1 Introduction

According to the Environment Agency’s guidance for the Lower Thames CFMP the area is generally urban with no major river flood defences in place. The key issues for the area include. • An estimated 32,500 properties within the Lower Thames catchment are subject to a 1 in 100 year or greater risk of flooding. • To reduce flood risk to those properties the preferred option would be to convey water through the Lower Thames floodplain more efficiently, but the feasibility of that approach has yet to be proven. • Any flood management works would have to be undertaken without causing significant adverse effects to the South West London Waterbodies Special Protection Area (SPA) and Ramsar Site 28 or to the non-SPA areas that are functionally linked to the SPA and Ramsar Site. • Further growth within the catchment is constrained by significant urban development, major components of water infrastructure (reservoirs), and areas of land with environmental and/or Green Belt designations that limit the scope for further expansion.

There are 8 sites proposed in the Aggregates Recycling DPD within the Lower Thames CFMP. Of those sites 5 are in the borough of Runnymede and 3 are in the borough of Spelthorne. The 4 sites at Penton Hook Marina in Chertsey, Lyne Lane in Chertsey, Trumps Farm near Longcross, and Charlton Lane in Shepperton are proposed solely for development as aggregate recycling facilities. The other 4 sites, including, Milton Park Farm (Preferred Area D) and Whitehall Farm (Preferred Area E) near Egham, Homers Farm near Bedfont (Preferred Area G), and Watersplash Farm near Halliford (Preferred Area L), are sand and gravel preferred areas (identified in the Primary Aggregates DPD), and are proposed for development as temporary aggregate recycling facilities.

This chapter draws on the following sources of information, the Runnymede BC SFRA, the Spelthorne BC SFRA, and Environment Agency fluvial flood risk modelling for the Lower Thames.

5.2 Flooding from rivers

5.2.1 Findings from Runnymede BC SFRA The Runnymede BC SFRA reports that the River Thames forms the eastern boundary of the borough, and that the floodplain of the river within the borough is extensive, due to the flat and low lying character of the land29. The fluvial flood risk mapping in the Runnymede BC SFRA indicates the following for the sites proposed in the Aggregates Recycling DPD: • Penton Hook Marina at Chertsey – the majority of the site is in an area of Zone 3b (1 in 20 year return period) fluvial flood risk. • Lyne Lane at Chertsey – the site coincides is in an area of Zone 1 fluvial flood risk. • Trumps Farm at Longcross – the site coincides with an area of Zone 1 fluvial flood risk. • Milton Park Farm near Egham (Preferred Area D) – there are areas within the site subject to Zone 3 and Zone 2 fluvial flood risk. • Whitehall Farm near Egham (Preferred Area E) – primary aggregate working and aggregate recycling – there are areas within the site subject to Zone 3 and Zone 2 fluvial flood risk.

5.2.2 Findings & Conclusions for the Aggregates Recycling DPD for sites in Runnymede BC Mapping undertaken for the Aggregates Recycling DPD using Environment Agency data indicated the following for each of the sites in Runnymede BC. •

28 The South West London Waterbodies SPA and Ramsar Site is designated under the EU Birds Directive & the Ramsar Convention on Wetlands of International Importance for the presence of 2 species of over-wintering waterfowl, the gadwall & the northern shoveler. The SPA & Ramsar Site is composed of 7 Sites of Special Scientific Interest (SSSIs): Kempton Park Reservoirs SSSI, Knight & Bessborough Reservoirs SSSI, Staines Moor SSSI, Thorpe Park No.1 Gravel it SSSI, Wraysbury & Hythe End Gravel Pits SSSI, Wraysbury No.1 Gravel Pit SSSI, & Wraysbury Reservoir SSSI. Another 28 waterbodies in the south west London area have been identified as being functionally related to the SPA & Ramsar Site. 29 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraphs 3.2.1 & 3.2.2, p.13. Runnymede BC

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Penton Hook Marina at Chertsey – the majority of the site is in an area of Zone 3b fluvial flood risk (Map 5.35a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of flood risk for the site (Map 5.35b, Appendix 1). • Lyne Lane at Chertsey – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.32a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of flood risk for the site (Map 5.32b, Appendix 1). • Land adjacent to Trumps Farm at Longcross – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.30a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of flood risk for the site (Map 5.30b, Appendix 1). • Milton Park Farm near Egham (Preferred Area D) – parts of the site are subject to Zone 3 and/or Zone 2 fluvial flood risk (see Map 5.4a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be an increase in the area of the site subject to Zone 3 fluvial flood risk (Map 5.4b, Appendix 1). • Whitehall Farm near Egham (Preferred Area E) – parts of the site are subject to Zone 3 and Zone 2 fluvial flood risk (see Map 5.5a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of flood risk for the site (Map 5.5b, Appendix 1).

Based on the information provided in the Runnymede BC SFRA and by the Environment Agency, and taking account of the guidance in PPS 25 it is concluded that the following sites are suitable for development as proposed in the Aggregates Recycling DPD: Lyne Lane at Chertsey; Trumps Farm at Longcross; Milton Park Farm near Egham (Preferred Area D); and, Whitehall Farm near Egham (Preferred Area E) so long as those facilities are located within the areas of the site at least risk of flooding. The proposed site at Penton Hook Marina at Chertsey is located in an area of Zone 3a and Zone 3b flood risk. The site is being proposed as a temporary aggregate recycling site by the Environment Agency, who have advised that the flooding issues for the site can be overcome.

5.2.3 Findings of Spelthorne BC SFRA The Spelthorne BC SFRA reports that flooding of the River Thames has affected the borough on a number of occasions, the most recent being in 200330. The SFRA maps the areas within the River Thames catchment that are subject to Zone 3 and Zone 2 fluvial flood risk.

The fluvial flood risk mapping in the Spelthorne SFRA indicates the following findings for the sites proposed in the Aggregates Recycling DPD: • Charlton Lane at Shepperton – extensive areas of the site are subject to Zone 2 fluvial flood risk according to the Spelthorne BC SFRA. • Homers Farm near Bedfont (Preferred Area G) – the site coincides with an area of Zone 1 fluvial flood risk according to the Spelthorne BC SFRA. • Watersplash Farm near Halliford (Preferred Area L) – the site is subject to Zone 3 and Zone 2 fluvial flood risk according to the Spelthorne BC SFRA.

5.2.4 Findings & Conclusions for the Aggregates Recycling DPD for sites in Spelthorne BC Mapping undertaken for the Aggregates Recycling DPD using Environment Agency data indicated the following for each of the sites in Spelthorne BC. • Charlton Lane at Shepperton – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.27a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (Map 5.27b, Appendix 1). • Homers Farm near Bedfont (Preferred Area G) – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.7a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (Map 5.7b, Appendix 1). • Watersplash Farm near Halliford (Preferred Area L) – extensive areas of the site are subject to Zone 3 and Zone 2 fluvial flood risk (see Map 5.12a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be an increase in the area of the site subject to Zone 3 fluvial flood risk (Map 5.12b, Appendix 1).

30 Jacobs (2006) Spelthorne Borough Council Strategic Flood Risk Assessment. Paragraph 59, p.15. Spelthorne BC.

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Based on the fluvial flood risk information provided in the Spelthorne BC SFRA and by the Environment Agency, and taking account of the guidance in PPS 25 it is concluded that the Charlton Lane site at Shepperton is suitable for development as proposed in the Aggregates Recycling DPD. The sites at Homers Farm near Bedfont (Preferred Area G) and Watersplash Farm near Halliford (Preferred Area L) are suitable for development as proposed in the Aggregates Recycling DPD so long as those facilities are located within the areas of the site at least risk of flooding.

5.3 Flooding from the Land

5.3.1 Findings of Runnymede BC SFRA The Runnymede BC SFRA assesses the risks of surface water flooding31, reporting that the majority of known incidents have occurred in Chertsey, Egham, Thorpe and Rowhill32. The SFRA reports on 50 non-fluvial flooding incidents, of which 4 were noted as having a surface water source.

Non-fluvial flooding incidents reported to the Environment Agency for Runnymede BC included 4 reports of waterlogged or flooded gardens or properties (June 2000 to January 2003), of which none were attributed to surface water sources.

5.3.2 Findings & Conclusions for the Aggregates Recycling DPD for sites in Runnymede BC Any risks of surface water flooding arising from changes in landcover associated with the development of the sites at Penton Hook Marina, Lyne Lane, Trumps Farm, Milton Park Farm (Preferred Area D) and Whitehall Farm (Preferred Area E) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. All of the sites would require the preparation of site specific FRA as part of the planning application, which should investigate the options for effective surface water management (including the scope for use of sustainable drainage systems).

5.3.3 Findings of Spelthorne BC SFRA The Spelthorne BC SFRA reports that flooding from surface water sources is known to be a problem during wet weather conditions33. The principal cause of surface water flooding is the capacity of the Thames Gravels, that underlie much of the borough, to absorb excess surface water and the extensive use of soakaways for drainage. The SFRA advises that localised surface water flooding issues should be addressed through the design of development.

Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC, included 4 reports of flooded properties or waterlogged or flooded gardens (August 2001 to April 2005), of which none were attributed to surface water sources.

5.3.4 Findings & Conclusions for the Aggregates Recycling DPD for sites in Spelthorne BC Any risks of surface water flooding arising from changes in landcover associated with the development of the Charlton Lane site, Homers Farm (Preferred Area G), or Watersplash Farm (Preferred Area L) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. All of the sites would require site specific FRA as part of the planning application process, which should investigate the options for effective surface water management (including the scope for use of sustainable drainage systems).

5.4 Flooding from groundwater

5.4.1 Findings of Runnymede BC SFRA The Runnymede BC SFRA assesses the risks of groundwater flooding34, reporting that the majority of known incidents have occurred in areas located within the floodplain of the River Thames and underlain by Thames Gravelsl35. The SFRA reports on 50 non-fluvial flooding incidents, of which 1 was noted as having a groundwater source.

31 Entec (2009) Runnymede Strategic Flood Risk Assessment. Chapter 6, pp.37-42. Runnymede BC 32 Ibid, paragraph 6.1.2, p.37. 33 Jacobs (2006) Spelthorne BC Strategic Flood Risk Assessment. Paragraphs 96-101, pp.20-21. Spelthorne BC. 34 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraphs 4.2.1 & 4.2.2, p.20. Runnymede BC 35 Ibid, paragraph 6.1.2, p.37.

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Non-fluvial flooding incidents reported to the Environment Agency for Runnymede BC included 4 reports of waterlogged or flooded gardens or properties (June 2000 to January 2003), which could all be attributed to groundwater sources.

5.4.2 Findings & Conclusions for the Aggregates Recycling DPD for sites in Runnymede BC Any risks of ground water flooding arising from changes in local hydrology associated with the development of Penton Hook Marina, Lyne Lane, Trumps Farm, Milton Park Farm (Preferred Area D), or Whitehall Farm (Preferred Area E) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Each site would require the submission of a site specific FRA as part of the planning application, which should investigate impacts on hydrology and groundwater.

5.4.3 Findings of Spelthorne BC SFRA The Spelthorne BC SFRA assesses the risks of groundwater water flooding, which are most commonly encountered in Staines, Shepperton and Sunbury and areas underlain by Floodplain Gravels 36. The SFRA advises that the risk of groundwater flooding is variable and dependent on local conditions, and recommends that site specific FRAs include detailed work on the risks of groundwater flooding.

Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC included 4 reports of flooded properties or waterlogged or flooded gardens (August 2001 to April 2005), of which 2 were attributed to groundwater sources.

5.4.4 Findings & Conclusions for the Aggregates Recycling DPD for sites in Spelthorne BC Any risks of groundwater flooding arising from changes in local hydrology associated with the development of Charlton Lane, Homers Farm (Preferred Area G), or Watersplash Farm (Preferred Area L) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Each site would require the submission of a site specific FRA as part of the planning application, which should investigate impacts on hydrology and groundwater.

5.5 Flooding from Sewers & Drains

5.5.1 Findings of Runnymede BC SFRA The Runnymede BC SFRA assesses the risks of flooding from the drainage system37, reporting that the majority of known incidents are related to drainage and culverted watercourses38. The SFRA reports on 50 non-fluvial flooding incidents, of which 38 were noted as having a drainage or sewer system source.

Non-fluvial flooding incidents reported to the Environment Agency for Runnymede BC included 4 reports of waterlogged or flooded gardens or properties (June 2000 to January 2003), of which none could be attributed to drainage system sources.

5.5.2 Findings & Conclusions for the Aggregates Recycling DPD for sites in Runnymede BC The impacts on the local sewer and foul water network of the development of the sites at Penton Hook Marina, Lyne Lane, Trumps Farm, Milton Park Farm (Preferred Area D), or Whitehall Farm (Preferred Area E) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Each site would require the submission of a site specific FRA as part of the planning application, which should investigate the implications for the existing drainage network.

5.5.3 Findings of Spelthorne BC SFRA The Spelthorne BC SFRA reviews the risks of flooding associated with sewers and drains, which it reports most commonly arise in urban areas due to the lack of sufficient capacity in the existing drainage and sewerage networks39. The SFRA advises that the risk of flooding from sewers and drains is typically a localised problem best addressed through the design process for individual developments.

36 Jacobs (2006) Spelthorne BC Strategic Flood Risk Assessment. Paragraphs 102-105, p.21. Spelthorne BC 37 Entec (2009) Runnymede Strategic Flood Risk Assessment. Paragraphs 4.1.3 & 4.1.6, pp.19-20. Runnymede BC 38 Ibid, paragraph 4.1.3, p.19. 39 Ibid. Paragraph 98, p.20.

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Non-fluvial flooding incidents reported to the Environment Agency for Spelthorne BC included 4 reports of flooded properties or waterlogged or flooded gardens (August 2001 to April 2005), of which 1 was attributed to a problem with a soakaway.

5.5.4 Findings & Conclusions for the Aggregates Recycling DPD for sites in Spelthorne BC The impacts on the local sewer and foul water network of the development of the sites at Charlton Lane, Homers Farm (Preferred Area G), or Watersplash Farm (Preferred Area L) as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Each site would require the submission of a site specific FRA as part of the planning application, which should investigate the implications for the existing drainage network.

5.6 Flooding from Reservoirs, Canals, & Other Artificial Sources

5.6.1 Findings of Runnymede BC SFRA The Runnymede BC SFRA assesses the risks of flooding associated with the failure of water supply infrastructure40. The SFRA considers the risk from the Virginia Water reservoir and the Basingstoke Canal, and advises that for sites downstream of the reservoir or canal the risks to the proposed development of their failure should be covered in the site specific FRA.

5.6.2 Findings & Conclusions for the Aggregates Recycling DPD for sites in Runnymede BC The development of the sites at Penton Hook Marina, Lyne Lane, Trumps Farm, or Milton Park Farm (Preferred Area D), or Whitehall Farm (Preferred Area E) as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on any parts of the water supply infrastructure located within the Lower Thames CFMP and Runnymede BC. Each site would encompass an area of more than 1 hectare, and would require the submission of a FRA as part of the planning application, which should address the question of the potential effects of water supply infrastructure failure on the site.

5.6.3 Findings of Spelthorne BC SFRA The Spelthorne BC SFRA includes a section on the risks of flooding associated with the failure of water supply infrastructure, reporting that Thames Water were consulted on the risk of reservoir failure but that the strategically critical nature of the reservoirs precluded disclosure of the risk assessments41. The SFRA advises that the risk of flooding due to catastrophic failure of water supply infrastructure is considered to be minimal.

5.6.4 Findings & Conclusions for the Aggregates Recycling DPD for sites in Spelthorne BC The development of the sites at Charlton Lane, Homers Farm (Preferred Area G), and Watersplash Farm (Preferred Area L) as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on any parts of the water supply infrastructure located within the Lower Thames CFMP and Spelthorne BC. Each site would require the submission of a site specific FRA as part of the planning application, which should investigate the implications for the existing drainage network.

5.7 Conclusions for the CFMP & the Aggregates Recycling DPD

Based on the information presented in the SFRAs for Runnymede and Spelthorne, and that provided by the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of the following sites for aggregate recycling is acceptable on flood risk grounds: Lyne Lane at Chertsey; Trumps Farm at Longcross; Charlton Lane at Shepperton; Homers Farm near Bedfont (Preferred Area G).

And at the following sites provided that the facilities are located in the areas of lowest flood risk available within the sites: Penton Hook Marina at Chertsey; Milton Park Farm near Egham; Whitehall Farm near Egham (Preferred Area E); Watersplash Farm near Halliford (Preferred Area L).

40 Ibid. Paragraphs 4.3.1-4.3.7, pp.20-22. 41 Jacobs (2006) Spelthorne BC Strategic Flood Risk Assessment. Paragraphs 106-109, p.22. Spelthorne BC

Aggregates Recycling DPD Strategic Flood Risk Assessment – August 2011 18

Chapter 6: The Lower, Middle & Upper River Mole CFMPs

6.1 Introduction

According to the Environment Agency’s guidance for the Upper River Mole CFMP the area comprises newer and expanding urban areas, often located towards the headwaters of river catchments. Key issues for the area include. • The location, layout and design of developments are vital factors in managing future flood risk, regeneration and redevelopment of some areas offers opportunities for flood risk reduction by, for example re-establishing river corridors and managing runoff more effectively. • The re-integration of rivers into the urban landscape, with reduced emphasis on the culverting and straightening of watercourses to help reduce flood risk. • The tendency of flooding to arise from a number of sources and to be localised in nature and the sensitivity of the area to rapid flooding from heavy rainfall events.

According to the Environment Agency’s guidance for the Middle River Mole CFMP the area comprises natural floodplain with market towns and villages. Key issues for the area include. • The importance of the natural floodplain in flood risk management and the need to safeguard it from inappropriate development. • The need to improve the flood resilience of development already located in the natural floodplain. • The need to develop and implement flood storage schemes that are complementary to the wider flood management objectives for the area.

According to the Environment Agency’s guidance for the Lower River Mole CFMP the area comprises urban areas with some river flood defences. Key issues for the area include. • Opportunities that redevelopment offers to reduce flood risk and improve resilience of the built environment to flooding. • The importance of safeguarding existing river corridors from inappropriate development in order to make use of them in schemes to adapt to the impacts of climate change. • The need to adapt existing flood defences and improve their capacity to cope with the impacts of climate change through a combination of flood storage, river defences and floodplain attenuation. • The need to develop capacity to deal with rapid flooding from heavy rainfall more effectively.

There are 2 sites proposed in the Aggregates Recycling DPD located within the area covered by the Lower, Middle & Upper River Mole CFMPs. Both sites are in the borough of Reigate & Banstead, Copyhold Works at Redhill, and Salfords Rail Depot in Salfords

This chapter draws on the following sources of information, the Reigate & Banstead BC SFRA, and Environment Agency fluvial flood risk modelling for the River Mole.

6.2 Flooding from rivers

6.2.1 Findings from Borough SFRA The Reigate & Banstead BC SFRA reports that the River Mole and its tributaries are located in the southern part of the borough, where much of the natural floodplain is retained, with the risk of fluvial flooding being of greatest concern in Horley and Redhill42. The flood risk mapping in the Reigate & Banstead BC SFRA indicates the following for the sites proposed in the Aggregates Recycling DPD located within the borough: • Copyhold Works at Redhill – the site coincides with an area of Zone 1 fluvial flood risk. • Salfords Rail Depot in Salfords – the site coincides with an area of Zone 1 fluvial flood risk.

6.2.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Mapping undertaken for the Aggregates Recycling DPD using Environment Agency data indicated the following for each of the sites in Reigate & Banstead BC. •

42 Jacobs (2007) Reigate & Banstead BC SFRA. Sections 6.1-6.3, pp.18-19. Reigate & Banstead BC, Reigate.

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Copyhold Works at Redhill – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.28a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (Map 5.28b, Appendix 1). • Salfords Rail Depot in Salfords – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.36a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (Map 5.36b, Appendix 1).

Based on the fluvial flood risk information provided by the Environment Agency, and taking account of the guidance in PPS 25 it is concluded that the proposed sites at Copyhold Works at Redhill, and Salfords Rail Depot in Salfords are suitable on flood risk grounds for development as aggregate recycling facilities as proposed in the Aggregates Recycling DPD.

6.3 Flooding from the land

6.3.1 Findings from Borough SFRA The Reigate & Banstead BC SFRA does not assess the risks of surface water flooding, but does report on local drainage issues43. Appendix B to the SFRA reports on 81 non-fluvial flooding incidents, of which 32 were noted as having a land drainage source.

Non-fluvial flooding incidents reported to the Environment Agency for Reigate & Banstead BC included 4 reports of waterlogged or flooded gardens or properties (June 2001 to June 2002), none of which were attributed to surface water sources.

6.3.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks of surface water flooding arising from changes in land-cover associated with the development of the sites at Copyhold Works in Redhill or Salfords Rail Depot in Salfords as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both sites would require site specific FRA as part of the planning application, which should investigate the options for effective surface water management (including the scope for use of sustainable drainage systems).

6.4 Flooding from groundwater

6.4.1 Findings from Borough SFRA The Reigate & Banstead BC SFRA reviews the risks of groundwater flooding, which is considered to be negligible across the borough44.

Non-fluvial flooding incidents reported to the Environment Agency for Reigate & Banstead BC included 4 reports of waterlogged or flooded gardens or properties (June 2001 to June 2002), of which 3 were attributed to groundwater sources.

6.4.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks of groundwater flooding arising from changes in the local hydrology associated with the development of the sites at Copyhold Works in Redhill, and Salfords Rail Depot in Salfords as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both sites would require site specific FRA as part of the planning application, which should investigate the risk to hydrology and groundwater associated with the development of the sites.

6.5 Flooding from Sewers & Drains

6.5.1 Findings from Borough SFRA The Reigate & Banstead BC SFRA reviews the risks of flooding arising as a result of problems with the local drainage system, which is considered to be negligible across the borough45. Appendix B to the SFRA reports on 81 non-fluvial flooding incidents, of which 68 were noted as having a highways drainage or public sewer source.

43 Jacobs (2007) Reigate & Banstead BC SFRA. Section 6.5, p.21. Reigate & Banstead BC, Reigate. 44 Ibid. Section 6.5, p.21. 45 Ibid. Section 6.5, p.21.

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Non-fluvial flooding incidents reported to the Environment Agency for Reigate & Banstead BC included 4 reports of waterlogged or flooded gardens or properties (June 2001 to June 2002), of which 1 was attributed to a blocked drain.

6.5.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The impacts on the local sewer and foul water network of the development of the sites at Copyhold Works in Redhill, and Salfords Rail Depot in Salfords as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both sites would require site specific FRA as part of the planning application, which should investigate the implications of the development of the sites for the existing local drainage network.

6.6 Flooding from Reservoirs, Canals, & Other Artificial Sources

6.6.1 Findings from Borough SFRA The Reigate & Banstead BC SFRA identifies 2 reservoirs within the borough that are registered under the Reservoirs Act 1975, and notes that catastrophic failure of reservoirs could pose a threat to life and property downstream46. The SFRA indicates that work undertaken by Jacobs for Defra and Thames Water suggests that the risk of a reservoir failing in any given year is 1 in 50,000.

6.6.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The development of the sites at Copyhold Works in Redhill or Salfords Rail Depot in Salfords as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on any parts of the local water supply infrastructure. Both sites would require site specific FRA as part of the planning application, which should address the question of the potential effects of water supply infrastructure failure on the sites.

6.7 Conclusions for the CFMPs & the Aggregates Recycling DPD

Based on the information presented in the Reigate & Banstead BC SFRA, and that provided by the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of the Copyhold Works at Redhill, and the Salfords Rail Depot in Salfords sites for aggregate recycling development is acceptable on flood risk grounds.

46 Jacobs (2007) Reigate & Banstead BC Strategic Flood Risk Assessment. Section 6.4, p.20. Reigate & Banstead BC, Reigate.

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Chapter 7: The Rural Wey CFMP

7.1 Introduction

According to the Environment Agency’s guidance for the Rural Wey CFMP the area comprises natural floodplain with market towns and villages. Key issues for the area include. • Maintenance of the capacity of the natural floodplain to retain water and of the capacity of watercourses to convey water in towns and villages. • Safeguarding of the natural floodplain from inappropriate development and improving the resilience of buildings located within the floodplain. • Enhancing capacity for storage of flood waters.

There are 2 sites proposed in the Aggregates Recycling DPD located within the area covered by the Rural Wey CFMP policy unit, at the former Wisley Airfield in the borough of Guildford, and at Alton Road in Farnham, in the borough of Waverley

This chapter draws on the following sources of information, the Guildford BC SFRA, the draft SFRA for Waverley BC, and Environment Agency fluvial flood risk modelling for the River Wey.

7.2 Flooding from Rivers

7.2.1 Findings from Borough SFRAs The Guildford BC SFRA reports that the River Wey is approximately 92 kilometres in length with a catchment of around 900 square kilometres47. The River Wey is navigable between the Thames and Godalming, includes a number of separate navigation channels and is engineered and canalised where it passes through major settlements including Guildford, Godalming, Farnham and Weybridge48. The river has a history of flooding, the most recent of which was recorded in the winter of 2002/0349. The flood risk mapping undertaken for the Guildford BC SFRA indicates that the proposed site at the former Wisley airfield coincides with an area of Zone 1 fluvial flood risk.

The draft Waverley BC SFRA reports that over two-thirds of the land within the borough lies in the catchment of the north branch of the River Wey, that the south east corner of the borough lies in the catchment of the south branch of the River Wey, and that those two watercourses account for the majority of flooding events that affect the area50.

7.2.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Mapping undertaken for the Aggregates Recycling DPD using Environment Agency data indicated the following for the site in Guildford BC. • Former airfield at Wisley – the site coincides with an area of Zone 1 fluvial flood risk (see Map 5.31a, Appendix 1). Under a climate change scenario (20% increase in river levels) there would be no change in the type of fluvial flood risk affecting the site (see Map 5.31b, Appendix 1). • Alton Road at Farnham – the site coincides with an area subject to Zone 1 fluvial flood risk and the access corridor to the site passes through an area of Zone 3 and Zone 2 fluvial flood risk (see Map 5.26a, Appendix 1). Under climate change a scenario (20% increase in river levels) there would be no significant change in the area of the site subject to Zone 3 fluvial flood risk (Map 5.26b, Appendix 1).

Based on the fluvial flood risk information provided in the Guildford SFRA and that provided by the Environment Agency, and taking account of the guidance in PPS 25 it is concluded that the proposed sites at the former airfield near Wisley, and at Alton Road in Farnham are suitable on flood risk grounds for development as proposed in the Aggregates Recycling DPD.

47 Capita Symonds (2009) Guildford Strategic Flood Risk Assessment: Volume 2 – Technical Report. Paragraph 2.3, p.6. Guildford BC. 48 Ibid, paragraph 2.4, p.6. 49 Ibid, paragraph 3.2, p.10 50 Waverley BC (2006) Draft Flood Risk Assessment for the Waverley BC Core Strategy. Paragraph 5.2. Waverley BC, Godalming.

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7.3 Flooding from the Land

7.3.1 Findings from Borough SFRAs The Guildford BC SFRA assesses the risks of surface water flooding51, and reports that the majority of known incidents within the borough have occurred in Guildford and in the Send, Send Marsh, Tongham, East Horsley and Effingham areas52.

The draft Waverley BC SFRA reviews flood risk from a variety of sources including surface water, and indicates where problems have been experienced in the various settlements within the borough53.

Non-fluvial flooding incidents reported to the Environment Agency included 12 reports of waterlogged or flooded gardens or properties (July 2000 to November 2002) for Guildford BC, of which 1 could be attributed to surface water sources, and 26 reports of waterlogged or flooded gardens or properties (September 2000 to March 2004) for Waverley BC, of which 9 could be attributed to surface water sources.

7.3.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks of surface water flooding arising from changes in landcover associated with the development of former airfield at Wisley, or the site at Alton Road near Farnham as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both of the sites would require site specific FRA as part of the planning application, which should investigate the options for effective surface water management (including the scope for use of sustainable drainage systems).

7.4 Flooding from Groundwater

7.4.1 Findings from Borough SFRAs The Guildford BC SFRA assesses the risks of groundwater flooding54, and reports that the areas susceptible to groundwater flooding are likely to be in the centre and the southern part of Guildford, the settlements and villages of the Tillingbourne Valley and the area around Shalford55.

The draft Waverley BC SFRA reviews flood risk from a variety of sources including groundwater, and indicates where problems have been experienced in the various settlements within the borough56.

Non-fluvial flooding incidents reported to the Environment Agency included 12 reports of waterlogged or flooded gardens or properties (July 2000 to November 2002) for Guildford BC, of which 9 could be attributed to groundwater sources, and 26 reports of waterlogged or flooded gardens or properties (September 2000 to March 2004) for Waverley BC, of which 14 could be attributed to groundwater sources.

7.4.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD Any risks of groundwater flooding arising from changes in local hydrology associated with the development of former airfield at Wisley, or the site at Alton Road near Farnham as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both of the sites would require site specific FRA as part of the planning application, which should investigate the likely impacts of development on hydrology and the risk of groundwater emergence.

7.5 Flooding from Sewers & Drains

7.5.1 Findings from Borough SFRAs The Guildford BC SFRA includes a section on the risks of flooding associated with sewers and drains, which it reports is managed by Thames Water 57.

51 Capita Symonds (2009) Guildford Strategic Flood Risk Assessment: Volume 2 – Technical Report. Paragraphs 7.1-7.13 pp.28-29. Guildford BC 52 Ibid, paragraph 7.3, p.28. 53 Waverley BC (2006) Draft Flood Risk Assessment for the Waverley BC Core Strategy. Paragraphs 13.3-13.32. Waverley BC, Godalming. 54 Capita Symonds (2009) Guildford SFRA: Vol 2 – Tech Rpt. Para 8.1.1-8.28 pp.34-42. Guildford BC 55 Ibid, paragraph 8.23, p.41. 56 Waverley BC (2006) Draft FRA for the Waverley BC Core Strategy. Paragraphs 13.3-13.32. Waverley BC, Godalming. 57 Capita Symonds (2009) Guildford SFRA: Vol 2 – Tech Rpt. Para 7.23-7.24 p.32. Guildford BC.

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The draft Waverley BC SFRA reviews flood risk from a variety of sources including drains and sewers, and indicates where problems have been experienced in the various settlements within the borough58.

Non-fluvial flooding incidents reported to the Environment Agency included 12 reports of waterlogged or flooded gardens or properties (July 2000 to November 2002) for Guildford BC, of which 3 could be attributed to drainage system sources, and 26 reports of waterlogged or flooded gardens or properties (September 2000 to March 2004) for Waverley BC, of which 3 could be attributed to drainage sources.

7.5.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The impacts on the local sewer and foul water network associated with the development of former airfield at Wisley, or the site at Alton Road near Farnham as proposed in the Aggregates Recycling DPD would be most appropriately investigated at the planning application stage. Both of the sites would require site specific FRA as part of the planning application, which should investigate the likely impacts of development on hydrology and groundwater emergence.

7.6 Flooding from Reservoirs, Canals, & Other Artificial Sources

7.6.1 Findings from Borough SFRAs The Guildford BC SFRA assesses the risks of flooding associated with a failure of the banks of the Basingstoke Canal and the Wey Navigation59. The SFRA reports that the embankment of the Basingstoke Canal is inherently prone to failure and that any development sites potentially downstream of a breakout point would require FRA in line with that required for sites in areas of Zone 3 or Zone 2 fluvial flood risk60. The SFRA reports for the Wey Navigation that, a breach of the banks of the Navigation would not be anticipated to significantly increase the predicted fluvial flood risk for the River Wey61.

The draft Waverley BC SFRA does not cover the risks of flooding as a consequence of the failure of water related infrastructure and other artificial sources.

7.6.2 Findings & Conclusions for sites allocated in the Aggregates Recycling DPD The development of former airfield at Wisley, and the site at Alton Road near Farnham as proposed in the Aggregates Recycling DPD would not give rise to significant impacts on the structure and integrity of the embankments of the Basingstoke Canal or the Wey Navigation. Both sites would require site specific FRA as part of the planning application, which should address the question of the potential effects of water supply infrastructure failure on the sites.

7.7 Conclusions for the Rural Wey CFMP & the Aggregates Recycling DPD

Based on the information presented in the SFRAs for Guildford BC and Waverley BC, and that provided by the Environment Agency, and taking account of the guidance set out in PPS 25 it is concluded that allocation of the sites at the former airfield near Wisley, and at Alton Road in Farnham for aggregate recycling development is acceptable on flood risk grounds.

58 Waverley BC (2006) Draft Flood Risk Assessment for the Waverley BC Core Strategy. Paragraphs 13.3-13.32. Waverley BC, Godalming. 59 Capita Symonds (2009) Guildford Strategic Flood Risk Assessment: Volume 2 – Technical Report. Paragraphs 9.1-9.20 pp.43-46. Guildford BC 60 Ibid, paragraphs 9.12 & 9.17, pp.45-46. 61 Ibid, Paragraph 9.18, p.46.

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Chapter 8: Guidance on Site Specific Flood Risk Assessment

8.1 Introduction

The Aggregates Recycling DPD SFRA has identified the level of flood risk associated with each of the sites proposed for aggregate recycling development, based on information drawn from the district and borough SFRAs and data provided by the Environment Agency.

All applications for planning permission relating to the sites proposed in the Aggregates Recycling DPD will have to be accompanied by a site specific FRA. The level of detail to be provided in those assessments will be determined by the size and nature of the proposed development and the severity of flood risk that affects the site and the area surrounding it.

8.2 FRA requirements for Aggregates Recycling DPD sites

The sites proposed in the Aggregates Recycling DPD fall into the following flood risk categories and will require the specified level of FRA in support of any future planning applications.

Fluvial Flood Risk Zone 1

Homers Farm, Bedfont (Preferred Area G) – proposed aggregate recycling on a primary aggregate site Level 1 FRA Copyhold Works, Redhill – proposed aggregate recycling site Level 1 FRA Former Wisley airfield, Wisley – proposed aggregate recycling site Level 1 FRA Lyne Lane, Chertsey – proposed aggregate recycling site Level 1 FRA Martyrs Lane, Woking – proposed aggregate recycling site Level 1 FRA Salfords Depot, Salfords – proposed aggregate recycling facility Level 1 FRA Stanwell Quarry, Stanwell – proposed aggregate recycling site Level 1 FRA Trumps Farm, Longcross – proposed aggregate recycling site Level 1 FRA

Fluvial Flood Risk Zone 2

Charlton Lane, Shepperton – proposed aggregate recycling site Level 2 FRA

Fluvial Flood Risk Zone 3

Addlestone Quarry Extension, Addlestone (Preferred Area A) – proposed aggregate recycling on a primary Level 3 FRA aggregate site Hamm Court Farm, Weybridge (Preferred Area C) – proposed aggregate recycling on a primary aggregate site Level 3 FRA Milton Park Farm, Egham (Preferred Area D) – proposed aggregate recycling on a primary aggregate site Level 3 FRA Whitehall Farm, Egham (Preferred Area E) – proposed aggregate recycling on a primary aggregate site Level 3 FRA Watersplash Farm, Halliford (Preferred Area L) – proposed aggregate recycling on a primary aggregate site Level 3 FRA Penton Hook Marina, Chertsey – proposed aggregate recycling site Level 3 FRA Alton Road, Farnham – proposed aggregate recycling site Level 3 FRA

For the sites located within Flood Risk Zone 2 and Flood Risk Zone 3 at which it is proposed that aggregate recycling facilities could be developed there will need to be a thorough investigation of the way in which the areas of land within those sites would be affected by flood events in order to identify areas that would be suitable for a ‘less vulnerable’ form of development as described in Table D.2 in Annex D to PPS 25.

For the five primary aggregate preferred areas that have also been identified as potential locations for temporary aggregate recycling facilities (Addlestone Quarry Extension, Hamm Court Farm, Milton Park Farm, Whitehall Farm and Watersplash Farm) that are subject to Zone 2 or Zone 3 fluvial flood risk, any aggregate recycling facilities developed at those sites must be located outside areas of Zone 3b (1

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in 20 year return period) fluvial flood risk. The site specific FRAs for any planning application made for aggregate recycling at those sites will have to demonstrate that the sequential approach has been applied to the selection of the location for the recycling plants.

The Environment Agency advises that, based on the known extent of fluvial flood risk, development of temporary aggregate recycling facilities should be feasible at the Milton Park Farm and Whitehall Farm sites at Egham and at the Watersplash Farm site at Halliford. For the Addlestone Quarry Extension site and the Hamm Court Farm site at Weybridge, based on the known extent of fluvial flood risk, the feasibility of aggregate recycling at those two sites is less certain, as both are subject to extensive Zone 3 fluvial flood risk. Detailed site specific FRA would needed at an early stage of the development of any proposals for aggregate recycling facilities at Addlestone Quarry extension and Hamm Court Farm, in order to determine whether there are sufficient areas of land within the sites subject to no greater than a Zone 3a fluvial flood risk to accommodate recycling facilities.

8.3 Environment Agency advice on the content of site specific FRAs

The Environment Agency advise that the following information needs to be provided in the site specific FRAs submitted in support of planning applications. The Environment Agency’s requirements for a site specific FRA are set out in sections 8.3.1 to 8.3.7.

Minerals sites (other than sand and gravel workings) and waste management facilities are defined in Table D.2 of PPS25 as ‘less vulnerable’ forms of development. Table D.3 of PPS25 shows that ‘less vulnerable’ land uses are appropriate for all flood zones except 3b (the functional floodplain). It will therefore be important for any site specific FRA submitted in support of an aggregate recycling application to define the extent of the functional floodplain where all or part of the proposed site is located within Flood Zone 3.

All applications for aggregate recycling on sites that are located in part or in whole within Flood Zones 2 and 3 will need to be supported by a site specific FRA. The site specific FRA will need to demonstrate that the sequential test has been carried out in respect of the selection of the site, and the selection of the specific location of development within the site, e.g. the precise location of recycling plant. All applications for sites measuring over 1 hectare, even where the site is located within Flood Zone 1, will need to provide a site specific FRA that details how surface water will be managed on site.

8.3.1 General Requirements The FRA should: • Demonstrate that the sequential test has been carried out in relation to site selection and the allocation of land for development within the site. • Include the results of topographical surveying of the site (before, during, and after). • Identify any constraints (e.g. contamination, proximity to watercourses, etc.) that may affect development of the site. • Provide details of the long term goals for the site (i.e. outline restoration plan). • Include details of proposed site layout and plans (including any buildings and extraction phases) in relation to floodplain.

8.3.2 Fluvial Flooding The FRA should: • Include fluvial flood risk mapping for the site. Flood levels and extents are available from the Environment Agency ([email protected]). Where more detail is required to define the flood extent, flood levels should be plotted on a topographical survey. Where flood levels are required for a detailed FRA but none are available, the applicant may need to produce a flood model (see 8.3.6). • Demonstrate that there will be no loss of floodplain storage up to the 1 in 100 year plus climate change flood level. • Demonstrate that the development will not impede the flow of flood waters within the site and in the surrounding area.

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8.3.3 Surface Water Flooding The FRA should: • Demonstrate that there will be no increase in the rate or volume of surface water discharge from the site as a consequence of the proposed development. • Demonstrate that any surface water flooding will be contained safely within the site. • Provide details of the measures that will be put in place to ensure that surface water is discharged to the ground (infiltration), and that only if infiltration techniques cannot be used will water from the site be discharged a watercourse or surface water sewer. • Provide sufficient information to demonstrate that the developed site will maintain or achieve the discharge characteristics of a greenfield site.

8.3.4 Other Sources of Flooding All sources of flooding should be investigated as part of the FRA. The relevant SFRAs will provide a starting point for that process. If another source of flooding does effect the site, the sequential test should be applied to that source of flooding in allocating land within the site for development (i.e. development should be located in the area at least risk of flooding from all sources).

Where other sources have been identified the FRA should demonstrate that the site can be made safe and that flood risk will not be increased elsewhere as a result of the proposed works (e.g. alterations to ground levels will not divert an overland flow path into another area).

8.3.5 Residual Risk of Flooding The site specific FRA should give consideration to the risk of flooding that remains after sequential testing, mitigation, etc. has been carried out. The FRA must demonstrate that any residual risk will be safely managed, which could include flood management and evacuation plans, flood resistant/resilient buildings, etc.

8.3.6 Flood Risk Modelling Modelling may be required to determine what the flood levels and extents are for the 1 in 20 year, 1 in 100 year and 1 in 100 year plus climate change flood events. The Environment Agency holds detailed modelling of most main rivers in Surrey and should be contacted for the most up to date information. The Environment Agency’s online flood map is updated on a quarterly basis, but in between those updates new models or surveys may be completed that may effect individual sites.

For advice on conducting flood risk modelling, refer to the Environment Agency’s guidance “Requirements for completing computer river modelling for FRAs” published in February 2009. Referring to the guidance will ensure that all the information the Environment Agency need to review the flood risk model is supplied at the earliest possible opportunity.

The Environment Agency should be consulted at the earliest opportunity, as they are able to review FRAs and flood models prior to submission, which can speed up the consultation process once an application for planning permission is submitted. The Environment Agency recommend that all sites are required to demonstrate a betterment in terms of their capacity to store water in times of flooding.

Detailed advice on FRA for a wide range of developments can be downloaded from the Environment Agency’s website (http://www.environment-agency.gov.uk/research/planning/93498.aspx ).

8.4 Advice on site specific FRAs from the PPS25 Practice Guide

The PPS 25 Development & Flood Risk Practice Guide advises on the different levels of detail expected in a site specific FRA62, and identifies sources of relevant information63.

8.4.1 Level 1 FRA A Level 1 FRA is a screening study64 to identify whether any flooding or surface water management issues related to a development site warrant further consideration. The Level 1 FRA should be based on readily available existing information, including the SFRA, Environment Agency Flood Map and

62 DCLG (2007) PPS 25: Development & Flood Risk Practice Guide. Figure 3.5, p.58. 63 Ibid, Figure 3.6, p.59. 64 Ibid, Figure 3.5, p.58.

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Standing Advice. The screening study will ascertain whether a Level 2 or Level 3 FRA is required. The following information sources be used when preparing a Level 1 FRA65. • Environment Agency Flood Map & Environment Agency Standing Advice • Table D.1 in PPS 25: Development & Flood Risk • Relevant SFRA

8.4.2 Level 2 FRA 66 A Level 2 FRA is a scoping study , undertaken if the Level 1 FRA (screening) indicates the site is at risk of flooding or may increase flood risk elsewhere. The Level 2 FRA should confirm the sources of flooding which may affect the site. The scoping study may determine that enough quantitative information is available to complete a FRA appropriate to the scale and nature of the development, and study should include the following: • An appraisal of the availability & adequacy of existing information • A qualitative appraisal of the flood risk posed to the site, & potential impact of the development on flood risk elsewhere • An appraisal of the scope of possible measures to reduce the flood risk to acceptable levels.

The following sources of information should be used in the preparation of a Level 2 FRA67. • Environment Agency Flood Map & Environment Agency Standing Advice • Table D.1 in PPS 25: Development & Flood Risk • Relevant SFRAs, & local policy statements or guidance (e.g. Local Development Documents) • CFMPs, Shoreline Management Plans (SMPs), & Surface Water Management Plans • Consultation with LPA/Environment Agency or other flood risk consultees to identify, in broad terms, what issues, related to flood risk, need to be considered including other sources of flooding • Historic maps • Local libraries & newspaper reports, & interviews with local people • Walkover survey to assess: potential sources of flooding; Likely routes for flood waters; key site features, including flood defences, & their condition. • Site survey to determine: general ground levels across the site; levels of any formal or informal flood defences relevant to the site.

8.4.3 Level 3 FRA A Level 3 FRA is a detailed study68 to be undertaken if the Level 2 FRA concludes that further quantitative analysis is required to assess flood risk issues related to the development site. The detailed study should include, quantitative appraisal of the potential flood risk to the development, quantitative appraisal of the potential impact of development site on flood risk elsewhere, and give a quantitative demonstration of the effectiveness of any proposed mitigation measures. The following sources of information should be used in the preparation of a Level 3 FRA69. • Environment Agency Flood Map & Environment Agency Standing Advice • Table D.1 in PPS 25: Development & Flood Risk • Relevant SFRAs & local policy statements or guidance (e.g. LDDs) • CFMPs, SMPs, & SWMPs • Consultation with the LPA/Environment Agency or other flood risk consultees to identify, in broad terms, what issues, related to flood risk, need to be considered including other sources of flooding • Historic maps • Local libraries & newspaper reports, & interviews with local people • Walkover survey to assess: potential sources of flooding; likely routes for flood waters; key site features, including flood defences, & their condition.

65 DCLG (2007) PPS 25: Development & Flood Risk Practice Guide, Figure 3.6, p.59. 66 Ibid, Figure 3.5, p.58. 67 Ibid, Figure 3.6, p.59. 68 Ibid, Figure 3.5, p.58. 69 Ibid, Figure 3.6, p.59.

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• Site survey to determine: general ground levels across the site; levels of any formal or informal flood defences relevant to the site. • Detailed topographical survey & detailed hydrographic survey • Site-specific hydrological & hydraulic modelling studies • Monitoring to assist with model calibration/verification • Continued consultation with the LPA, Environment Agency & other flood risk consultees.

8.4.4 Outputs of a FRA The PPS 25 Development & Flood Risk Practice Guide provides the following guidance on the outputs of a site specific FRA, and on the issues of uncertainty and the use of modelling70. The content of a FRA should always be appropriate to the scale and nature of the development. The outputs of a FRA will be site-specific and dependant on the site characteristics. A typical Level 2 or Level 3 FRA could cover the following:

Development description & location • The type of development proposed and where it will be located • The vulnerability classification (Table D.2, Annex D, PPS25) • Whether the proposed development is consistent with the Local Development Documents • Evidence that the Sequential Test and Exception Test (if necessary) has been applied in the selection of the site, or reference to this if presented in other planning documents

Definition of the flood hazard • All sources of flooding that could affect the site • Identify sources, describe how flooding would occur, with reference to any historic records wherever these are available • The existing surface water drainage arrangements for the site

Probability • The flood zone the site is within • Information from the SFRA covering the site • Probability of the site flooding, taking account of the SFRA & any further site-specific assessment • Existing rates & volumes of run-off generated by the site, including flow & rate of onset

Climate change • Effects of climate change on flood risk for the lifetime of the development – use Annex B of PPS25

Detailed development proposals • Details of development layout, referring to relevant drawings (cross refer to main application) • Demonstrate how land-uses most sensitive to flood damage have been placed in areas within the site that are at least risk of flooding (applying the Sequential Test at site level).

Flood risk management measures • How the site will be protected from flooding, including potential impacts of climate change, over the development’s lifetime

Off site impacts • Demonstrate how measures to protect the development from flooding will ensure that there will be no increased flood risk elsewhere • Measures to prevent run-off from the development causing an increased impact elsewhere • Incorporation of SUDS in the overall design of the development or justification of why not

70 DCLG (2007) PPS 25: Development & Flood Risk Practice Guide. Paragraphs 3.78-3.82, pp.60-62.

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Residual risks • Assessment of flood-related risks remaining after measures to protect the site from flooding have been implemented • Who will manage the risks & enforce compliance over the lifetime of the development

Allowing for uncertainty Where flood risk is an important issue and evidence is required to show that the planning application passes the Exception Test, FRAs may require complex analyses and the use of specialist techniques and software, particularly in the design of measures to protect vulnerable properties from flooding. Hydrologists and hydraulic modellers seldom have all the data they require in order to accurately determine the flows and flood levels associated with events with annual probabilities as low as 1%. Developers should liaise with LPAs and the Environment Agency to ensure that, where such studies are proposed, they are appropriate and the approach adopted takes adequate account of the need to: • calibrate & verify numerical models using all relevant information reasonably available • allow for uncertainties in the input parameters; & • consider the sensitivity of modelling results to uncertainty in the input parameters & adopt a precautionary approach, particularly where uncertainty could have serious consequences.

Use of modelling software The modelling software chosen for Level 3 FRAs should be capable of producing the relevant outputs identified in the scope for the FRA. It will generally be appropriate to choose commercial hydraulic/ river modelling software that is in widespread use for work in relation to river and coastal flooding. Surface water flooding and design of drainage elements may require different software. In certain circumstances, for example, where the applicability of a model to a specific situation has not been previously demonstrated, it will be necessary for those conducting the FRA to have independent benchmarking tests carried out to demonstrate model performance using standard data.

In reporting on any hydraulic modelling carried out as part of the FRA, a technical description of the model should be provided. This should include the name and version of the software used. Where non-standard software has been used, evidence should be provided to demonstrate the applicability of the model(s) to the situation in question.

A non-technical summary of modelling outputs should be produced for non-specialists to be able to understand the conclusions and implications for flood risk on and off the site.

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Bibliography

Capita Symonds (2007) Woking & Surrey Heath Strategic Flood Risk Assessment – Volume 2: Technical Report (Final). Woking Borough Council, Woking & Surrey Heath Borough Council, Camberley.

Capita Symonds (2009) Guildford Strategic Flood Risk Assessment: Volume 2 – Technical Report. Guildford Borough Council, Guildford.

Department of Communities & Local Government (DCLG) (2006) Planning Policy Statement 25: Development & Flood Risk. The Stationery Office (TSO), London.

DCLG (2008) Planning Policy Statement 25: Development & Flood Risk Practice Guide. DCLG, London.

Entec (2009) Runnymede Strategic Flood Risk Assessment. Runnymede Borough Council, Addlestone.

Jacobs (2006) Spelthorne Borough Council Strategic Flood Risk Assessment. Spelthorne Borough Council, Staines.

Jacobs (2007) Reigate & Banstead Borough Council Strategic Flood Risk Assessment. Reigate & Banstead Borough Council, Reigate.

Office of the Deputy Prime Minister (ODPM) (2005) Planning Policy Statement 1: Delivering Sustainable Development, HMSO, London.

Waverley Borough Council (2006) Draft Flood Risk Assessment for the Waverley Borough Council Core Strategy. Waverley Borough Council, Godalming.

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