The Hideaway, Heath End Road, Baughurst, Rg26 5Nd

THE HIDEAWAY, HEATH END ROAD, BAUGHURST, RG26 5ND

FLOOD RISK ASSESSMENT AND DRAINAGE STRATEGY

FOR

NEW RESIDENTIAL DEVELOPMENT

ON BEHALF OF

GRAPHENE ARCHITECTS

34 GLOUCESTER ROAD RICHMOND, TW9 3BU

GRAR/20-0018/FRA01

APRIL 2020

DOCUMENT CONTROL

Project: The Hideaway, Heath End Road, Baughurst, RG26 5ND New Residential Development

Document: Flood Risk Assessment and Drainage Strategy

Client: Graphene Architects

Reference: GRAR/20-0018/FRA01

Document Checking:

Name Date Signature

Author: Chris Williams 24.04.2020

Checked by: Gregory Schmidt 24.04.2020

Approved by: Gregory Schmidt 24.04.2020

Status:

Issue Date Status Issued by

1. 24.04.2020 First Issue Gregory Schmidt 2. 3. 4. 5.

No part of this publication may be reproduced by any means without the prior permission of Russell Giles Partnership Limited.

GRAR/20-0018/FRA01

TABLE of CONTENTS 1 INTRODUCTION ...... 1 2 PLANNING POLICY ...... 2 2.1 National Planning Policy Framework (NPPF) ...... 2 2.2 Local Policies ...... 3 2.3 Statutory Authority Consultation ...... 3 3 PLANNING POLICY CONTEXT ...... 4 3.1 Flood Zones ...... 4 3.2 Flood Risk Vulnerability Classification ...... 4 3.3 Flood Risk Vulnerability and Flood Zone Compatibility ...... 6 3.4 Sequential test and Exception Test ...... 6 4 EXISTING SITE INFORMATION ...... 7 4.1 Site Location ...... 7 4.2 Existing Site Description ...... 7 4.3 Source Protection Zone ...... 8 4.4 Existing Geology and Hydrogeology ...... 9 4.5 Surrounding Hydrology ...... 10 5 PROPOSED DEVELOPMENT INFORMATION ...... 11 5.1 Proposed Development Description ...... 11 6 FLOOD RISK ...... 12 6.1 Flooding from Seas (Tidal) ...... 12 6.2 Flooding from Rivers (Fluvial)...... 12 6.3 Flooding from Surface Water (Pluvial) ...... 13 6.4 Flooding from Groundwater ...... 14 6.5 Flooding from Public Sewers/Highway Drains ...... 14 6.6 Flooding from Artificial Sources ...... 15 6.7 Peak Rainfall Intensity Allowance for Climate Change ...... 15 7 PROPOSED DRAINAGE STRATEGY AND SUDS ...... 16 7.1 Existing Surface Water Run-off ...... 16 7.2 Surface Water Option 1 – Infiltration Scheme and Soakaway Design Estimate ...... 16 7.3 Surface Water Option 2 – Attenuation Scheme and Tank Design Estimate...... 17 7.4 Sustainable Drainage Systems (SuDS) ...... 18 7.5 Proposed Foul Drainage Strategy ...... 24 8 SAFE ACCESS ...... 25 9 CONCLUSION ...... 26 APPENDIX 1 Site Plans APPENDIX 2 Topo Survey APPENDIX 3 Basingstoke and Deane Borough Council SFRA APPENDIX 4 Thames Water Sewer Records and Correspondance APPENDIX 5 Hampshire CC Guidance for Developers, Designers and Planners. APPENDIX 6 RGP Drainage Calculations

GRAR/20-0018/FRA01

List of Tables Table 1 – Flood Zones ...... 4 Table 2 - Flood Risk Vulnerability Classification ...... 4 Table 3 - Flood Risk Vulnerability and Flood Zone Compatibility ...... 6 Table 4 – Existing Site Surface Coverage ...... 8 Table 5 - Existing Permeable and Impermeable Surface Areas ...... 8 Table 6 – Proposed Development Surface Coverage ...... 11 Table 7 – Proposed Permeable and Impermeable Surface Areas ...... 11 Table 8 - Existing Site Surface Water Runoff Rates – IH 124 Method ...... 16 Table 9 - Proposed Soakaway Summary ...... 17 Table 10 - Proposed Attenuation Summary ...... 18 Table 11 - SuDS Assessment ...... 20

List of Figures Figure 1 - SFRA Update May 2012, Basingstoke and Deane Historic Flooding - Area 2 ...... 2 Figure 2 - Site Location Plan showing approx. Redline Boundary ...... 7 Figure 3 - Source Protection Zone Layout ...... 9 Figure 4 - Aquifer Designation Map (Defra) ...... 9 Figure 5 - Underlying Bedrock Formation ...... 10 Figure 6 - Underlying Superficial Deposits ...... 10 Figure 7 – EA Flood Map – Wider Area ...... 12 Figure 8 - EA Flood Map ...... 13 Figure 9 - EA Surface Water Flood Risk Map ...... 13 Figure 10 - EA Flood Risk from Reservoir Map ...... 15

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

1 INTRODUCTION

1.1 RGP has been commissioned by Graphene Architects (the ‘Client’) to consider the flood risk associated with the proposed development at The Hideaway, Heath End Road, Baughurst, RG26 5ND, from all potential sources of flooding, as defined by the National Planning Policy Framework (NPPF). RGP has also been commissioned to provide a Drainage Strategy for the proposed development, which is included with this FRA.

1.2 In compiling this Flood Risk Assessment and Drainage Strategy, reference has also been made to the Basingstoke and Deane Borough Council Strategic Flood Risk Assessment, updated in 2012, and Hampshire County Council Guidance for Developers, Designers and Planners.

1.3 The aim of this FRA is to review the potential flooding impact on the proposed development site due to tidal, fluvial (Rivers), pluvial (Overland), sewer, reservoir, canal and other artificial flooding sources. The FRA will also review the potential impact of the development on the flooding in the surrounding area and the measures that could be incorporated as part of the design to mitigate the potential risk.

1.4 This FRA has been developed in accordance with the requirements of Chapter 14 of the NPPF, published February 2019, the Lead Local Flood Authority (LLFA) and Thames Water.

1.5 Information used in preparing this Flood Risk Assessment was obtained from the following sources and Statutory Consultees:

(i) Environment Agency Flood Map (ii) Environment Agency Main River Map (iii) Environment Agency Long Term Flooding Map (iv) SFRA for Basingstoke and Deane Borough Council, produced by Halcrow Group Limited (2010) (v) Hampshire County Council Guidance for Developers, Designers and Planners (vi) Thames Water Asset Maps

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

2 PLANNING POLICY

The proposed development will be designed in accordance with the requirements as set out in the National Planning Policy and Local Planning Policy documents produced for Basingstoke and Deane Borough Council.

2.1 National Planning Policy Framework (NPPF)

2.1.1 Section 14 of the NPPF (2019) outlines the requirements for determining if a Flood Risk Assessment is required to be undertaken for new developments. A site-specific FRA should be provided for all sites which are located in Flood Zone 2 and 3.

2.1.2 An FRA should be provided for sites located in Flood Zone 1 where:

 The development site area > 1ha;

 The site has been identified by the LLFA / Environment Agency as having critical drainage problems;

 The site has been identified in a strategic flood risk assessment as being at increased flood risk in future; or

 Land that may be subject to other sources of flooding, where its development would introduce a more vulnerable use.

2.1.3 The development site at The Hideaway, Heath End Road, Baughurst is located within Flood Zones 1 and the overall development area is 9500m², which would generally not require submission of a formal FRA. However, the site is identified as being ‘Upstream of Critical Drainage Area’ and the LPA therefore require an FRA to be submitted for planning. Confirmation of critical drainage areas is provided on Figure 1 and the site is identified with a red star.

Figure 1 - SFRA Update May 2012, Basingstoke and Deane Historic Flooding - Area 2

2.1.4 The NPPF sets out the strategy throughout the UK for future development. The key policy provision states that:

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

 Inappropriate development in areas at risk of flooding should be avoided by directing development away from areas at highest risk (whether existing or future). Where development is necessary in such areas, the development should be made safe for its lifetime without increasing flood risk elsewhere.

 Strategic policies should be informed by a strategic flood risk assessment, and should manage flood risk from all sources. They should consider cumulative impacts in, or affecting, local areas susceptible to flooding, and take account of advice from the Environment Agency and other relevant flood risk management authorities, such as lead local flood authorities and internal drainage boards.

 All plans should apply a sequential, risk-based approach to the location of development – taking into account the current and future impacts of climate change so as to avoid, where possible, flood risk to people and property.

2.2 Local Policies

2.2.1 Basingstoke and Deane Borough Council have produced a Strategic Flood Risk Assessment (SFRA). The SFRA contains information on the flood zones and an assessment of risk from all sources of flooding that exist.

2.2.2 The SFRA includes flood risk information suitable to satisfy the requirements of a Level 1 and Level 2 SFRA.

2.2.3 As LLFA, Hampshire Council have produced a Guidance for Developers, Designers and Planners. This document sets out how Hampshire will review drainage strategies and surface water management provisions associated with applications for development.

2.2.4 The Hampshire guidance document sets out the hierarchy required to be considered by applications in terms of proposed drainage provision. The hierarchy is as follows:

“Generally, the aim should be to discharge surface run off as high up the following hierarchy of drainage options as reasonably practicable:

1. into the ground (infiltration);

2. to a surface water body;

3. to a surface water sewer, highway drain, or another drainage system;

4. to a combined sewer.”

2.2.5 This FRA and Drainage Strategy has been produced in line with the above-mentioned documentation.

2.3 Statutory Authority Consultation

2.3.1 The site is located within an area served by Thames Water. A copy of the Thames Water Asset Map information is included in APPENDIX 4 of this report. The asset map shows that there is an existing Ø225 combined water sewer running in an easterly direction along Pinks Lane, to which the existing property has a combined water lateral connection.

2.3.2 Along with the asset Search information, Thames Water have also supplied a sewer flooding report, which confirms that there are no records of flooding associated with their assets within close proximity to the development site.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

3 PLANNING POLICY CONTEXT

A site-specific FRA should be carried out to demonstrate how flood risk will be managed now and over the development’s lifetime, taking into account climate change and with regards to the vulnerability of its users.

In order to adequately consider and demonstrate how the flood risk will be managed, we need to identify what the probability is of the site flooding, what the site is going to be used for, the associated flood risk vulnerability, and the compatibility between the flood risk vulnerability and the flood zones.

This section details how the planning policy is applied to this site-specific FRA. Items highlighted in ‘Green’ in the following tables detail the site specific

3.1 Flood Zones

3.1.1 The flood zones refer to the probability of river and sea flooding, ignoring the presence of defences.

Table 1 – Flood Zones Flood Zone Probability Definition Land having a less than 1 in 1,000 annual probability of river or Flood Zone 1 Low sea flooding. (Shown as ‘clear’ on the Flood Map – all land outside Zones 2 and 3) Land having between a 1 in 100 and 1 in 1,000 annual probability of river flooding; or land having between a 1 in 200 Flood Zone 2 Medium and 1 in 1,000 annual probability of sea flooding. (Land shown in light blue on the Flood Map) Land having a 1 in 100 or greater annual probability of river flooding; or Land having a 1 in 200 or greater annual Flood Zone 3a High probability of sea flooding. (Land shown in dark blue on the Flood Map) This zone comprises land where water has to flow or be stored in times of flood. Local planning authorities should identify in Functional their Strategic Flood Risk Assessments areas of functional Flood Zone 3b Flood Plain floodplain and its boundaries accordingly, in agreement with the Environment Agency. (Not separately distinguished from Zone 3a on the Flood Map)

3.1.2 The particular flood zone(s) for the development are detailed on the Environment Agency’s ‘Flood Map for Planning’, which is available online and is detailed further in Section 6 of this report.

3.2 Flood Risk Vulnerability Classification

3.2.1 The different types of flood risk vulnerability classifications are detailed in Table 2 below:

Table 2 - Flood Risk Vulnerability Classification Classification Description Essential  Essential transport infrastructure (including mass evacuation routes) which Infrastructure has to cross the area at risk.  Essential utility infrastructure which has to be located in a flood risk area for operational reasons, including electricity generating power stations and grid and primary substations; and water treatment works that need to remain operational in times of flood.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

Classification Description  Wind turbines. Highly  Police and ambulance stations; fire stations and command centres; Vulnerable telecommunications installations required to be operational during flooding.  Emergency dispersal points.  Basement dwellings.  Caravans, mobile homes and park homes intended for permanent residential use.  Installations requiring hazardous substances consent. (Where there is a demonstrable need to locate such installations for bulk storage of materials with port or other similar facilities, or such installations with energy infrastructure or carbon capture and storage installations, that require coastal or water-side locations, or need to be located in other high flood risk areas, in these instances the facilities should be classified as ‘Essential Infrastructure’). More  Hospitals Vulnerable  Residential institutions such as residential care homes, children’s homes, social services homes, prisons and hostels.  Buildings used for dwelling houses, student halls of residence, drinking establishments, nightclubs and hotels.  Non–residential uses for health services, nurseries and educational establishments.  Landfill* and sites used for waste management facilities for hazardous waste.  Sites used for holiday or short-let caravans and camping, subject to a specific warning and evacuation plan. Less  Police, ambulance and fire stations which are not required to be Vulnerable operational during flooding.  Buildings used for shops; financial, professional and other services; restaurants, cafes and hot food takeaways; offices; general industry, storage and distribution; non-residential institutions not included in the ‘more vulnerable’ class; and assembly and leisure.  Land and buildings used for agriculture and forestry.  Waste treatment (except landfill* and hazardous waste facilities).  Minerals working and processing (except for sand and gravel working).  Water treatment works which do not need to remain operational during times of flood.  Sewage treatment works, if adequate measures to control pollution and manage sewage during flooding events are in place. Water  Flood control infrastructure. Compatible  Water transmission infrastructure and pumping stations.  Sewage transmission infrastructure and pumping stations.  Sand and gravel working.  Docks, marinas and wharves.  Navigation facilities.  Ministry of Defence installations.  Ship building, repairing and dismantling, dockside fish processing and refrigeration and compatible activities requiring a waterside location.  Water-based recreation (excluding sleeping accommodation).  Lifeguard and coastguard stations.  Amenity open space, nature conservation and biodiversity, outdoor

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

Classification Description sports and recreation and essential facilities such as changing rooms.  Essential ancillary sleeping or residential accommodation for staff required by uses in this category, subject to a specific warning and evacuation plan.

3.3 Flood Risk Vulnerability and Flood Zone Compatibility

Table 3 - Flood Risk Vulnerability and Flood Zone Compatibility Flood Risk Vulnerability Classification Essential Highly More Less Water Flood Zone Infra Vulnerable Vulnerable Vulnerable Compatible

Flood Zone 1     

Flood Zone 2      Exception Exception Flood Zone 3a†    Test Test

Flood Zone Exception    * 3b* Test

 Development Appropriate

 Development Should not be Permitted † Essential Infrastructure should be designed and constructed to remain operational and safe in times of flood

* In Flood Zone 3b (functional floodplain) essential infrastructure that has to be there and has passed the Exception Test, and water-compatible uses, should be designed and constructed to:  remain operational and safe for users in times of flood;  result in no net loss of floodplain storage;  not impede water flows and not increase flood risk elsewhere.

3.4 Sequential test and Exception Test

3.4.1 The development area of the site falls completely within Flood Zone 1. In accordance with the NPPF, the development includes demolition of a private residential dwelling and construction of 4 new dwellings, as such does not constitute a change in risk vulnerability classification (both classed as ‘More Vulnerable’). No sequential test is required.

3.4.2 Development within Flood Zone 1, for sites classed as ‘More Vulnerable’ should be permitted and as such, no exception test is required.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

4 EXISTING SITE INFORMATION

4.1 Site Location

4.1.1 The proposed development site is located at The Hideaway, Heath End Road, Baughurst, RG26 5ND (see Error! Reference source not found. below). The site is located towards the northern end of Baughurst, a residential area approx. 11.2km to the NNW of Basingstoke.

Figure 2 - Site Location Plan showing approx. Redline Boundary 4.2 Existing Site Description

4.2.1 The proposed development site currently consists of a single dwelling with garage and associated grounds. The site is bound to the north by an existing private shared road/driveway and Pinks Lane to the south, east and west by existing residential plots.

4.2.2 The approximate OS Grid Location for the development site is E: 458405, N: 162516

4.2.3 The existing site comprises a single dwelling with an overall development area of 1187m². The development includes the roof areas to the house and garage structures, existing gravel parking / driveway areas and gardens / landscaping.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

4.2.4 The extent of the various existing site surfacing is detailed in Table 4,below:

Table 4 – Existing Site Surface Coverage Item Description Area (m²) 1. Roof 82 2. Caravans / sheds (un-drained) 96 3. Concrete footways (un-drained) 36 4. Gravel driveways / open spaces 720 5. Gardens 253 Total 1,187m²

4.2.5 The permeable and impermeable areas for the existing site are summarised below in Table 5:

Table 5 - Existing Permeable and Impermeable Surface Areas Item Description Area (m²) 1. Permeable Area 973 2. Impermeable Area 214 Total 1,187m²

4.2.6 A topographical survey has been undertaken at the existing site and shows that the the site is largely flat, with existing site levels varying between 106.3m AOD to the southern end and 105.75m AOD to the north. Please see the Topo Survey Plan, included in APPENDIX 2 of this report for additional information.

4.2.7 The site is served by a combined water lateral connection which runs south from the existing dwelling and discharges to the existing Ø225 public combined sewer located on in Pinks Lane (Please see the Thames Water Asset Map included in APPENDIX 4 of this report). The existing combined water lateral connection is proposed to be reused for the foul water drainage from the new development.

4.2.8 As part of the development proposal, this combined connection is may need to also be reused for controlled discharge of surface water, should the use of infiltration be deemed unsuitable. The proposed surface water run-off is discussed in detail in Section 7 of this report. In line with building regulations, the proposed foul and surface water systems would remain separate until the final chamber prior to discharge to the off-site combined sewer.

4.2.9 Please refer to the topographical survey for additional details pertaining to the existing site layout.

4.3 Source Protection Zone

4.3.1 The site is located outside of Source Protection Zones, as is illustrated in 3, below. Please refer to Error! Reference source not found., below (red dot) which details the location of the site.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

Figure 3 - Source Protection Zone Layout 4.3.2 The Defra “Magic Map” shows that the site is located within an area which is underlain by a Secondary A Aquifer. Secondary A Aquifers as defined by the EA are “permeable layers capable of supporting water supplies at a local rather than strategic scale, and in some cases forming an important source of base flow to rivers. These are generally aquifers formerly classified as minor aquifers”. Please refer to 4, below (red dot) which details the location of the site.

I Figure 4 - Aquifer Designation Map (Defra) 4.3.3 It should not be necessary to apply for permission/approval to discharge the surface water and roof run-off from the development to soakaways as the site is located outside of source protection zones.

4.4 Existing Geology and Hydrogeology

4.4.1 Having reviewed the existing British Geological Society (BGS) online mapping, the existing site is shown to be located in an area underlain by a bedrock geology of Thames Group - clay, silt, sand and gravel. The lithology is typically silty clay/mudstone, sandy silts and sandy clayey silts of marine origin – it is also known as London Clay. Please refer to 5, below, which details the existing bedrock formation and the site location.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

Figure 5 - Underlying Bedrock Formation 4.4.2 According to the BGS online mapping, the superficial deposits recorded at the site location are Head Deposits comprising gravel, sand, silt and clay. Please refer to 6, below, which details the location of the site.

Figure 6 - Underlying Superficial Deposits 4.5 Surrounding Hydrology

4.5.1 The development site is not located close to any Main Rivers or Ordinary Water Courses. The closest Main Rivers or streams are located the over 2km away, both east and west of the site. The Worthing coastline is located approx. 3.2km south of the development site.

4.5.2 There is an existing ditch, designated as a ‘ordinary watercourse’, located approximately 130m to the east of the development site. This ditch is not proposed to be affected by the development, as it falls outside the boundary of the site, and is very unlikely to provide a suitable discharge point for proposed SW.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

5 PROPOSED DEVELOPMENT INFORMATION

5.1 Proposed Development Description

5.1.1 Please refer to APPENDIX 1 of this report for all site layout plans.

5.1.2 The proposed development includes for the demolition of the existing dwelling and associated out buildings, together with the construction of 4 new dwellings, with associated accesses and parking areas. (Please refer to drawing 2203-201, included in APPENDIX 1 of this report, for the proposed development layout)

5.1.3 It is proposed that the new driveways and parking areas will be constructed using permeable material, with the surface water drainage infiltrating into the permeable sub-base layer. The proposed surface water drainage strategy is discussed in detail in Section 7.2 of this report.

5.1.4 The extent of the proposed surfacing to be installed as part of the new development is include in Table 6, below:

Table 6 – Proposed Development Surface Coverage Item Description Area (m²) 1. Drive and Parking 365 2. Roof Area 295 3. Footpaths 210 4. Grass/Landscaping 317 Total 1,187m²

5.1.5 The proposed permeable and impermeable areas for the development site are summarised below in Table 7:

Table 7 – Proposed Permeable and Impermeable Surface Areas Item Description Area (m²) 3. Development Permeable Area 317 4. Development Impermeable Area 870 Total 1,187m²

5.1.6 The proposed impermeable surface area of the new development is approximately 656m² more than the existing impermeable area, an increase of 55%. This increase is predominantly due to the significant increase in roof area to accommodate the new dwellings.

5.1.7 Although there is an increase in impermeable area over the current situation, this will be balanced by providing either a full infiltration scheme or controlled SW discharge to Greenfield rates, in line with LLFA requirements.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

6 FLOOD RISK

6.1 Flooding from Seas (Tidal)

6.1.1 The site is located approximately 68.4 km inland from the nearest sea (at Portsmouth) and as such, the site is not affected by tidal flooding.

6.1.2 Please see Error! Reference source not found.7, which details the location of the site in relation to the wider surrounding area.

Figure 7 – EA Flood Map – Wider Area 6.1.3 Owing to the land-bound location of the site, the flood risk associated with flooding from seas has been discounted.

6.2 Flooding from Rivers (Fluvial)

6.2.1 The site is located approx. 2.7km from the River Enborne, which is north-west of the development site. There are a number of unnamed water courses and drainage ditches shown to be draining the wider Baughurst / Heath End area, which would appear to eventually feed into the River Enborne, the closest of which is approximately 480m to the south of the development site and of course the earlier mentioned ditch approximately 130m to the east. As such, the site is not affected by fluvial flooding. Please refer to 7, above which details the location of the development site in relation to the nearest rivers.

6.2.2 The EA Flood Map for Planning shows the proposed development site to be located within Flood Zone 1, which represents an annual probability of flood risk from rivers or seas of less than 0.1% (1:1000). Please refer to 8, below, which shows the site located within Flood Zone 1.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

Figure 8 - EA Flood Map 6.2.3 The flood risk associated with flooding from rivers has been assessed as very low.

6.3 Flooding from Surface Water (Pluvial)

6.3.1 In the event of excessive rainfall, where the ground has become saturated and rainfall is not able to infiltrate into the ground, the overland flow would typically flow towards the nearest watercourse/ditch. This runoff can cause localised flooding before discharging to the watercourse/ditch.

6.3.2 The EA Surface Water Flood Map shows that the site is at low risk of flooding from overland flow. There is some low risk flooding indicated at the northern site boundary, which may be attributed to existing levels along the shared driveway and detailed review of the proposed levels along that boundary will be undertaken at detailed design stage to confirm that any potential risk to property is mitigated.

6.3.3 Any overland flow associated with Pinks Lane is directed away from the development site, along the highway, in a south easterly direction towards the existing unnamed drainage ditch. Please refer to Error! Reference source not found., below.

Figure 9 - EA Surface Water Flood Risk Map

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

6.3.4 The risk of overland flooding to the site has been assessed as low.

6.4 Flooding from Groundwater

6.4.1 There are four sources, or mechanisms, of groundwater flooding referred to in the Basingstoke and Deane Borough Council SFRA. These are described by as:

 High groundwater levels producing high baseflow in the river channels which exceeds channel capacity;

 High groundwater levels which rise above the ground surface locally;

 Localised surface water runoff (direct from overland flow);

 Sewer flooding.

6.4.2 Of the abovementioned potential causes of groundwater flooding, only the first two are directly affected as a result of environmental conditions. The remaining 2 potential causes of groundwater flooding are mainly the result of man-made activities, or the stopping of such activities.

6.4.3 There are no works currently being undertaken at the development site, or planned to be undertaken at the development site that would have an impact on the 2 man- made causes of groundwater flooding and there are no recorded sewer flooding incidents in the locality, as discussed in section 6.5 below. As such, this FRA will review the impact on groundwater flooding based on the environmental conditions at the site.

6.4.4 The Basingstoke and Deane SFRA assesses the flood risk due to ground water and provides details of recorded incidents of ground water flooding within the report area, from which it is noted that there are no references to such occurrences in reasonable proximity to the proposed site; the nearest reference being to a few incidents of groundwater flooding within Tadley.

6.4.5 The SFRA goes on to state that “groundwater flooding events were at their most significant in areas underlain the chalk, and indeed recent research tends to suggest that chalk aquifers are more prone to groundwater flooding than other aquifers”. This is not applicable to the development site, which is not underlain by chalk.

6.4.6 Having reviewed the groundwater emergence maps provided in Appendix D of the SFRA, it would seem that the proposed development site does not lie within an area which is classified as being susceptible to groundwater flooding

6.4.7 Based on the above, the risk of ground water flooding has been assessed as very low.

6.5 Flooding from Public Sewers/Highway Drains

6.5.1 Sewer flooding can occur when sewer systems become overloaded. Flooding of properties usually happens when either; flood water backs up in the pipes and enters directly into low lying properties or where the capacity of the system is exceeded and water discharges from the manholes and runs overland into properties.

6.5.2 Thames Water has provided a Sewer Flooding History Enquiry which confirms no recorded incidents of public sewer related flooding in the immediate vicinity of the site (see correspondence included in APPENDIX 4 of this report).

6.5.3 The risk associated with sewer flooding has been assessed to be low.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

6.6 Flooding from Artificial Sources

6.6.1 Based on the Environment Agency’s ‘Long Term Flood Risk’ map, the site is not affected by the failure of any reservoir or other man-made infrastructure. Please refer to Error! Reference source not found., below, which details the extent of the flooding from the failure of reservoirs in the surrounding area.

Figure 10 - EA Flood Risk from Reservoir Map 6.6.2 The risk associated with flooding from reservoir failure has been assessed and very low.

6.7 Peak Rainfall Intensity Allowance for Climate Change

6.7.1 Having reviewed the EA Table 2 – “Peak Rainfall Intensity Allowance in Small and Urban Catchments”, we have assumed a climate change allowance of 40% for the proposed onsite surface water drainage design. Please refer to Section 7 for a detailed assessment of the proposed surface water drainage strategy for the development.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

7 PROPOSED DRAINAGE STRATEGY AND SUDS

7.1 Existing Surface Water Run-off

7.1.1 The existing surface water drainage network will be investigated at the detailed design stage to confirm the existing layout and also the levels of the existing lateral connection to the Thames Water combined network. The investigation could include a CCTV survey but will be finalised at the detail design stage.

7.1.2 The estimated existing impermeable site area draining un-attenuated to the public combined sewer is approximately 214m² (0.021ha). The existing surface water runoff rate has been calculated using the Wallingford Procedure (Design and analysis of Urban Storm Durations), Volume 4, The Rational Modified method. Please refer to APPENDIX 6 for the detailed calculations.

7.1.3 Using the IH124 calculations method, the greenfield surface water discharge rates generated for the 1-year, 30-year and 100-year are detailed in Table 8, below.

Table 8 - Existing Site Surface Water Runoff Rates – IH 124 Method Storm Qmax Design Qmax (l/s) (l/s) M1 0.84 5.00 M30 2.26 5.00 M100 3.14 5.00

7.1.4 The calculation has been carried out using HR Wallingford ‘Greenfield runoff rate estimation for sites on-line tool, which states that flow rates lower than 5 l/s should be set at that rate, to lower the risk of potential blockage; therefore, at any proposed design flow is to be set 5 l/s. (Please refer to APPENDIX 6 in this report for the calculations)

7.2 Surface Water Option 1 – Infiltration Scheme and Soakaway Design Estimate

7.2.1 In line with the LLFA drainage hierarchy, the favoured surface water drainage option is intended to be via infiltration, through the use of permeable paving and soakaways. However, geotechnical information is not available at this time and the drainage strategy therefore provides an alternative option, in the event that ground conditions do not support the use of infiltration.

7.2.2 The total impermeable area of the proposed development site comprises approximately 73% of the site, which is an increase of approx. 55% when compared to the existing site. The proposed new drive and carparking areas are proposed to be constructed using permeable pavement techniques which will allow the surface water runoff to infiltrate into the existing ground.

7.2.3 The existing surface water connection to the Thames Water combined water system is proposed to be terminated (but maintained for foul water discharge).

7.2.4 It is proposed that the roofs of the proposed dwellings will discharge runoff to individual plot soakaways located either within rear gardens or under the parking areas to the front of properties. Please refer to drawing “20/0018-003 – Proposed Drainage Layout”, included in APPENDIX 1 of this report, for the location of the proposed soakaways.

7.2.5 In accordance with Building Regulations, the soakaways will be positioned more than 5m away from the edge of the proposed new building.

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7.2.6 An initial assessment of the required soakaways has been undertaken utilising a conservative infiltration rate of 1 x 10-5 m/s. It has been assumed that the infiltration rate achievable at the site location, this will be confirmed by on-site infiltration testing to inform the final detailed design.

7.2.7 A summary of the proposed soakaway sizes is included below in Table 9. Please refer to APPENDIX 6 of this report, which includes the initial calculations for the soakaway sizing.

Table 9 - Proposed Soakaway Summary Soakaway Area Type Void Infiltration Length Width Depth Volume Ref: (m²) Ratio Rate (m) (m) (m) (m³) (m/s) Soakaway 1 80 Geocellular 95% 1 x 10-5 4 1 1 3.8 Soakaway 2 80 Geocellular 95% 1 x 10-5 4 1 1 3.8 Soakaway 3 80 Geocellular 95% 1 x 10-5 2 2 1 3.8 Soakaway 4 80 Geocellular 95% 1 x 10-5 2 2 1 3.8

7.2.8 The drainage system will be designed to accommodate the 1:30 year flood with no flooding on site. The abovementioned soakaway design does accommodate this requirement. However, due to the topography of the site and there being little area available to accommodate above ground flooding, the drainage system will be designed to accommodate up to the 1:100 + 40% for climate change storm event.

7.2.9 The proposed new car parking / driveway areas would discharge direct to the underlying ground by means of a permeable pavement structure. It is proposed to include a coarse graded aggregate (CGA) permeable sub-base layer approx. 250mm thick. This sub-base thickness is typically in line with the high-level drainage design components utilised for the 1:100 + climate change event and will be subject to detail design prior to construction.

7.3 Surface Water Option 2 – Attenuation Scheme and Tank Design Estimate

7.3.1 As stated above, in the event that infiltration is ruled out following site specific testing, an attenuated discharge is intended to be provided which will utilise the existing connection to the Thames water public combined sewer.

7.3.2 In order to facilitate this solution, surface water will be routed from north to south through the site, to connect into the final demarcation manhole at the last possible location prior to leaving the site. This chamber will be constructed on the line of the existing combined water lateral connection.

7.3.3 Prior to connection into the final chamber, a flow control will be installed into SIC 1, which will restrict the discharge to no greater than the design rate of 5 l/s, as described in section 7.1.3 above.

7.3.4 Attenuation of flows backing-up from the flow control will be provided by means of a cellular attenuation tank installed under the parking area for Plot 2. A summary of the proposed attenuation size is included below in 10. Please refer to APPENDIX 6 of this report, which includes the initial calculations for the attenuation sizing.

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Table 10 - Proposed Attenuation Summary Ref: Area Type Void Discharge Length Width Depth Volume (m²) Ratio Rate (l/s) (m) (m) (m) (m³) Tank 1 660 Geocellular 95% 5.0 7 4 0.5 13.3

7.3.5 The drainage system will be designed to accommodate the 1:30 year flood with no flooding on site. However, due to the topography of the site and there being little area available to accommodate above ground flooding, the drainage system will be designed to accommodate up to the 1:100 + 40% for climate change storm event.

7.4 Sustainable Drainage Systems (SuDS)

7.4.1 The SuDS Manual (CIRIA C753) identifies that “Surface water is a valuable resource, and this should be reflected in the way it is managed and used in the built environment. It can add to and enhance biodiversity, beauty, tranquillity and the natural aesthetic of buildings, places and landscapes and it can help make them more resilient to the changing climate”.

7.4.2 Also, “The philosophy of sustainable drainage systems is about maximising the benefits and minimising the negative impacts of surface water runoff from developed areas. The SuDS approach involves slowing down and reducing the quantity of surface water runoff from a developed area to manage downstream flood risk, and reducing the risk of that runoff causing pollution. This is achieved by harvesting, infiltrating, slowing, storing, conveying and treating runoff on site and, where possible, on the surface rather than underground”.

7.4.3 The implementation of sustainable water management through sustainable drainage systems and rainwater harvesting is becoming more common in an effort to use and manage water sustainably. The philosophy of SUDS is to mimic as closely as possible the natural drainage from a site before development and to treat runoff to remove pollutants.

7.4.4 SUDS provide a flexible approach to drainage, with a wide range of components from soakaways to large-scale basins or ponds. The individual techniques should be used in a management train that reinforces and, where possible, follows the natural pattern of drainage. The management train incorporates a hierarchy of techniques. These are:

 Prevention – the use of good site design and housekeeping measures on individual sites to prevent runoff and pollution (examples include minimising paved areas and the use of sweeping to remove surface dust from car parks),

 Source control – control of runoff at or very near its source (such as the use of rainwater harvesting, pervious pavements, green roofs or soakaways for individual houses).

 Site control – management of water from several sub-catchments (including routeing water from roofs and car parks to one large soakaway or infiltration basin for the whole site).

 Regional control – management of runoff from several sites, typically in a detention pond or wetland.

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7.4.5 Adopting a holistic approach towards surface water drainage provides the benefits of combined water quality and quantity control, as well as increased amenity value. This is accomplished by managing the increased flows and pollution from surface water runoff that can arise from development. Ideally, the system should utilise a management train and should achieve equal standing in all three of these areas. However, specific site considerations may mean that a balance of benefits is not always achieved.

7.4.6 The priority for the discharge of surface water run-off should be:

 Infiltration;

 Discharge to surface waters;

 Discharge to a surface water sewer, highway drain or another drainage system;

 Discharge to a combined sewer.

7.4.7 Discharge of surface water run-off should not be discharged to a foul sewer.

7.4.8 In order to manage surface water sustainably, the use of SuDS is recommended. There are a number of different options available and these are detailed and assessed below in Table 11. The various SuDS systems have been assessed to determine their suitability for the proposed development site.

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Table 11 - SuDS Assessment SuDS Suitable Description Pro’s Con’s Feature for Use Only provides detention capability within the drainage network until the tank is full. Unless the storage tank Makes use of surface water run-off as Rainwater can be sized to accommodate all Rainwater collected in an above or below ground part of the new developments water harvesting storm events (which is highly unlikely tank for reuse on site. usage strategy. Provides some detention  systems and uneconomical), RWH systems capacity within the drainage network. cannot be assumed to contribute to a reduction in peak flow rate on a consistent basis. Increased Cost (compared to Mimic predevelopment state of conventional roof), not appropriate hydraulics and hydrology, good removal A planted soil layer is created on the roof to for steep roofs, maintenance of roof capability of atmospherically deposited Green roofs create a living surface. Water is stored in the soil vegetation, any subsequent damage urban pollutants, ecological, aesthetic  and absorbed by the vegetation. to waterproof membrane likely to be and amenity benefits, no additional land more critical since water is take. encouraged to remain on the roof Not suitable for poor draining soils, field investigations required to confirm infiltration rates, not suitable for locations where infiltration water may put structural foundations at risk, or Minimal net land take, provides where infiltrating water may adversely groundwater recharge, good volume affect existing drainage patterns, not Infiltration Collect and store run-off allowing for infiltration reduction and peak flow attenuation, appropriate for draining polluted systems into the existing ground. good community acceptability, easy to runoff, increased risk of groundwater  (soakaways) construct and operate, can be pollution, some uncertainty over long- retrofitted. term performance and possible reduced performance during long wet periods, where the property owner is responsible for operation and maintenance, performance difficult to guarantee.

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SuDS Suitable Description Pro’s Con’s Feature for Use Proprietary Provide treatment of the surface water run-off treatment through the removal of contaminants.  systems Well suited to implementation adjacent Not suitable for steep sites, not to large impervious areas, encourages suitable for draining hotspot runoff or evaporation and can promote Run-off is allowed to flow over a grassed or for locations where risk of infiltration, easy to construct and low Filter Strips otherwise densely vegetated area to promote groundwater contamination, unless construction cost, effective pre-  sedimentation and filtration. infiltration is prevented, no significant treatment option, easily integrated into attenuation or reduction of extreme landscaping and can be designed to event flows provide aesthetic benefits High clogging potential without effective pre-treatment – not for sites with fine particled soils (clay/silts) in Important hydraulic benefits are upstream catchment, build-up of Run-off is temporarily stored below the surface in a achieved, can be incorporated easily pollution/ blockages difficult to see, Filter Drains gravel filled trench which provides attenuation, into site landscaping and fit well beside high historic failure rate due to poor  conveyance and treatment. roads. maintenance, wrong siting or high debris input, limited to relatively small catchments, high cost of replacing filter material should blockage occur. Easy to incorporate into landscaping, good removal of urban pollutants, Not suitable for steep areas or areas A vegetated channel that conveys surface water reduces runoff rates and volumes, low with roadside parking, limits Swales run-off. Can be ‘wet’ or ‘dry’, lined or unlined to capital cost, maintenance can be opportunities to use trees for  allow infiltration. incorporated into general landscape landscaping, risks of blockages in management, pollution and blockages connecting pipe work are visible and easily dealt with.

Shallow land depression used to allow surface Can be planned as landscaping Requires landscaping and water run-off to pond temporarily, before filtering management, susceptible to Bioretention features, very effective in removing through vegetation and underlying soils prior to clogging if surrounding landscape is Systems urban pollutants, can reduce volume  being collected or infiltrated into the existing and rate of runoff, flexible layout to fit not managed, not suitable for areas ground. into landscape, well-suited for installation with steep slope

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SuDS Suitable Description Pro’s Con’s Feature for Use in highly impervious areas, provided the system is well-engineered and adequate space is made available. Tree can be used to improve the performance of a number of SuDS features as root growth and decomposition increase infiltration capacity. They Trees can also be used as standalone features within  tree pits, collecting and storing run-off and providing treatment. Reduced peak flows to watercourses reducing the risk of flooding Cannot be used where large Surface Water run-off is allowed to flow through downstream, reduced effects of sediment loads may be the structural paving (block paving, block work or pollution in runoff on the environment, washed/carried onto the surface, in Pervious porous asphalt paving). Water can be stored in can be used in high density the UK, current practice is to use on Pavements the sub-base of the construction make-up and developments with a range of surface highways with low traffic volumes, low  often permitted to infiltrate into the underlying finishes that accept surface waters over axle loads and speeds of less than 30 ground. their area of use, reduced need for deep mph, risk of long-term clogging and excavations for drainage, which can weed growth if poorly maintained. have significant cost benefits. Storage is typically provided in large underground Modular and flexible, dual usage (i.e. storage features that are used to temporarily store infiltration and/or storage), high void Attenuation the surface water run-off before being infiltrated, ratios, lightweight and easy to install and No water quality treatment or Storage discharged under controlled conditions or re-used robust, capable of managing high flow amenity provision, performance can on site. Typically constructed from geo-cellular events, can be installed beneath (geocellular be difficult to monitor, can be difficult  storage systems, concrete tanks or oversized trafficked or non-trafficked areas, long- storage to maintain. systems) pipes. They can be lined to make them term physical and chemical stability, can impermeable or enclosed in a geotextile which be installed beneath public open allows for infiltration into the surround soil. spaces, e.g. play areas. During a rainfall event, run-off accumulates in a Can cater for a wide range of rainfall Little reduction in runoff volume, Detention landscape depression with a restricted outlet. This events, can be used where groundwater detention depths may be constrained Basins allows the run-off to fill the detention basin and is vulnerable, if lined, simple to design  provides attenuation. Basins are generally dry, and construct, potential for dual land by system inlet and outlet levels. except during and immediately after the storm use, easy to maintain, safe and visible

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SuDS Suitable Description Pro’s Con’s Feature for Use event. Vegetated detention basins allow for capture of accidental spillages. treatment of the conveyed run-off across the length of the basin. Land take is high, requires baseflow, Ponds and wetlands typically have a ‘wet’ bottom Good removal capability or urban limited depth range for flow which means the bottom of the feature holds pollutants, if lined, can be used where attenuation, may release nutrients water during the year. These features have a groundwater is vulnerable, good during non-growing season, little Ponds and restricted outlet which allows water levels to rise community acceptability, high potential reduction in run volume, not suitable Wetlands within the pond or wetland during the storm event,  ecological, aesthetic and amenity for steep sites, colonisation by before being discharged. They can support both benefits, may add value to local invasive species would increase emergent and submerged vegetation which property. maintenance, performance enhance the treatment process and biodiversity. vulnerable to high sediment inflows.

7.4.9 Based on the above assessment, the outline drainage strategy for the development could include some of the following SuDS features into the design (subject to detail design and agreement with the local authority, LLFA and the EA):

 Pervious Pavement

 Infiltration Systems (soakaways)

 Attenuation Storage systems (as an alternative to soakaways)

7.4.10 Other SuDS features detailed above in Table 11 were not suitable for inclusion into the drainage strategy due to site constraints, land limitations, topographic limitations and the general size of the development. Also, it is proposed to terminate the off-site surface water discharge to Southern Water, which also has an impact on the type and extent of some SuDS features.

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7.5 Proposed Foul Drainage Strategy

7.5.1 The existing site has a combined surface water and foul sewer connection, which discharges to the Thames Water public combined sewer network, located in Pinks Lane. Indicative record of the sewer location has been provided by Thames water and the sewer pipe diameter confirmed as Ø225 (serving both surface water and foul water) and it is proposed to maintain this discharge connection on site.

7.5.2 The majority of the existing foul water drainage at the development is proposed to be taken up as part of the works and a new underground foul water drainage network is proposed to be installed, up to a new point of connection to the existing lateral pipe immediately prior to it leaving the southern site boundary.

7.5.3 The proposed foul sewer discharge rate calculated for the 4 dwellings is 0.19 l/s, which represents a minimal increase in flow over the current single dwelling, which is estimated to be around 0.05 l/s.

7.5.4 In the event that surface water can be removed from the system via the use of infiltration techniques, there will be a useful net reduction into the Thames Water sewer.

7.5.5 An application to Southern Water for a new indirect foul sewer connection to the existing public sewer network would be submitted in order to accommodate the proposed new development. This application would be progressed once planning consent had been awarded and the detail design of the foul water drainage system has been completed.

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8 SAFE ACCESS

8.1.1 The site is located in Flood Zone 1 and has a very low probability of flooding, this FRA demonstrates that the risk to human life associated with access and egress from the proposed dwellings during a period of excessive rainfall is very low.

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9 CONCLUSION

1.6 This FRA has been undertaken in accordance with the requirements of the NPPF, SFRA Basingstoke and Deane Borough Council and Hampshire County Council Guidance for Developers, Designers and Planners.

9.1.1 The FRA has considered the potential risk of flooding for all sources and has concluded that the flood risk from all sources is low.

9.1.2 It has not been necessary to undertake a Sequential Test as the proposed development work comprises no change of use from the existing residential setting. The development site is located in Flood Zone 1 and has a flood risk vulnerability categorisation if ‘More Vulnerable’, as such, an Exception test is not required.

9.1.3 The existing surface water discharge to the Southern Water foul sewer main located on Warren Road is proposed to be terminated, with the proposed development surface water drainage being discharged to a combination of soakaways on site and permeable paving to the car parking areas. This connection will be maintained for the discharge of foul water only from the new development.

9.1.4 SuDS features, in the form of permeable paving to the car parking / driveway areas and soakaways located under gardens or car parking, are proposed as the preferred solution. To demonstrate an alternative solution, in the event that infiltration is ruled out during on-site confirmatory testing, it is proposed to include approx. 14m³ of attenuation volume, with discharge controlled to a maximum 5 l/s.

9.1.5 The proposed surface water drainage system will be designed to prevent flooding for up to the 1:30 year storm event and will accommodate the discharge from the site for up to and including the 1:100 + 40% for climate change storm event.

9.1.6 The existing foul connection on site is to be maintained and the proposed development will incorporate the existing connection into the foul water drainage strategy. The proposed foul water discharge has been assessed in accordance with current building standards.

9.1.7 Based on the information collated as part of this FRA, the proposed development flood risk from all sources has been assessed as low. The development site is located within Flood Zone 1 and the assessment of the potential future flooding of the site illustrates that this will be maintained in the future.

9.1.8 The development proposed for this site should not be precluded based on flood risk grounds.

GRAR/20-0018/FRA01 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 1 SITE PLANS

GRAR/20-0018/FRA01 N

RWP RWP

RWP

RWP RWP

P1 ISSUED FOR INFORMATION CW 24.04.20 REV DESCRIPTION BY DATE N N

Godalming Office Shackleford Suite, Mill Pool House, Mill Lane, Godalming, GU7 1EY

[T]: 01483 861 681 [F]: 01438 861 682 [e]: [email protected] www.rgp.co.uk

Transport Planning and Infrastructure Design Consultants Godalming and London Client

GRAPHENE ARCHITECTS

Project THE HIDEAWAY, HEATH END RD BAUGHURST, RG26 5ND Drawing Title PROPOSED DRAINAGE STRATEGY LAYOUT

Scale Drawn By Checked By Approved By 1:500 @ A3 CW GS NDR Date Drawing No. Rev. APRIL 2020 20 / 0018 - 003 P1 New dropped kerb

Unit 1 Unit 3

Unit 2 Unit 4

Pinks Lane

New dropped kerb

20000

Revision Date Drawn Checked Notes

34 Gloucester Rod 020 7158 0840 Richmond [email protected] TW9 3BU www.graphenearchitects.co.uk

0m 5m 10m Project Hideway, Pinks Lane Baughurst Drawing Site Plan - Scale Date 1:100 @A1 21.10.19 Drawing No Revision 2203 201 - The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 2 TOPO SURVEY

GRAR/20-0018/FRA01

The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 3 BASINGSTOKE AND DEANE BOROUGH COUNCIL SFRA

GRAR/20-0018/FRA01

Basingstoke and Deane Borough Council Strategic Flood Risk Assessment for Local Development Framework

Final January 2010

Halcrow Group Limited

Basingstoke and Deane Borough Council Strategic Flood Risk Assessment for Local Development Framework

Final January 2010

Halcrow Group Limited

Halcrow Group Limited Griffin House 135 High Street Crawley West Sussex RH10 1DQ Tel +44 (0)1293 434500 Fax +44 (0)1293 434599 www.halcrow.com

Halcrow Group Limited has prepared this report in accordance with the instructions of their client, Basingstoke and Deane Borough Council, for their sole and specific use. Any other persons who use any information contained herein do so at their own risk.

Basingstoke and Deane Borough Council Strategic Flood Risk Assessment for Local Development Framework

Contents Amendment Record This report has been issued and amended as follows:

Issue Revision Description Date Signed

1 1 Draft Sept 07 Bruno Venturini

2 1 Draft 1 Jan 08 BV and AS

3 1 Draft 2 Mar 08 BV and AS

3 2 Final July 08 BV and AS

4 1 Final Revision Jan 09 BV/AS/OE

Contents

Glossary

1 Executive Summary 1

2 Background Information 3 2.1 Terms of Reference 3 2.2 The Study Area 3 2.3 Constraints on Development due to Protected Areas 5

3 Planning Context 7 3.1 Introduction 7 3.2 The EU Water Framework Directive and River Basin Management Plans 7 3.3 ‘Making Space for Water’ and Catchment Flood Management Plans 8 3.4 National Planning Policy 8 3.5 CFMPs, SFRAs and the Water Cycle Strategy in Basingstoke and Deane 11 3.6 Regional Planning Policy 11 3.7 Local Planning Policy 12

4 PPS25 Flood Zones, Environment Agency Flood Zones and SFRA Flood Maps 13 4.1 Introduction 13 4.2 The PPS25 Flood Zones 13 4.3 Environment Agency Flood Zones 14 4.4 SFRA Flood Maps 15

5 PPS25 and its Practice Guide Companion 16 5.1 PPS25 - Key Aims 16 5.2 Outcomes of the SFRA Process 17 5.3 SFRA Levels 1 and 2 17 5.4 The Sequential Test of PPS25 18 5.5 The Exception Test of PPS25 19 5.6 The Practice Guide Companion to PPS25 20

6 Study Methodology 23 6.1 Specific Project Outputs 23

6.2 Approach to Data Gathering 23 6.3 Forms of Flooding and Data Limitations 24 6.4 Production of Flood Maps 28

7 Flood Risk in the Study Area 33 7.1 Introduction 33 7.2 Overview of Catchments 33 7.3 History of Flooding 34 7.4 Flooding Mechanism for Permeable Catchments 34 7.5 Groundwater Flooding 35 7.6 Localised Flooding Areas 37 7.7 Planned Development Areas 37 7.8 Effect of Development on Flood Risk Elsewhere 40

8 CFMPs, Flood Management Measures, Flood Warning Systems and Defences 42 8.1 Introduction 42 8.2 Catchment Flood Management Plans 42 8.3 Flood Warning Systems 47 8.4 Defences and Future Flood Risk Management Schemes 48

9 Guidance on the Application of the Sequential Test 49 9.1 Introduction 49 9.2 First Step – Strategic Overview of Flood Risk for all Potential Areas 50 9.3 Second Step – Analysis of Flood Risk Issues 50 9.4 Third Step – Apply the PPS25 Flood Risk Management Measures 51 9.5 Fourth Step – Apply the Sequential Test in Flood Zone 2 51 9.6 Fifth Step – Apply the Sequential Test in Flood Zone 3 51

10 Guidance for the Preparation of Flood Risk Assessments 53 10.1 Introduction 53 10.2 Proposed Developments within Flood Zone 3a and 2 and/or other sources of flooding 53 10.3 Proposed Development within Flood Zone 1 55 10.4 Proposed Development within Groundwater Emergence Zones 56 10.5 Raised Floor Levels 57 10.6 Basements 58 10.7 Safe Access 58

11 Guidance for the Application of Sustainable Drainage Systems 59 11.1 Introduction 59 11.2 Types of SUDS Systems 59 11.3 Effective Application of SUDS Techniques 63 11.4 Selection of SUDS for a new site development 65

12 Summary of Principle Recommendations 70

Appendices Appendix A – Details of the Environment Agency Flood Zones Appendix B – Audit Trail Database Appendix C – Loddon and Basingstoke CFMP Policy Documents Appendix D – Groundwater Emergence maps from Groundwater Flooding Scoping Study LDS 23 (Jacobs, 2004) Appendix E – Rainfall Runoff Management for Developments – Interim National Procedure Appendix F – Drainage Guidance and Runoff Calculations

Tables Table 1 – Overview of the flood risk management hierarchy Table 2 - Historical Flooding - Southern Water Table 3 – Historical Flooding - Thames Water Table 4 – Localised Flooding Areas Table 5 – Areas where drainage network might be at full capacity Table 6 – Groundwater Flooding Incidents – Southern Region Table 7 – Groundwater Flooding Incidents – Thames Region Table 8 – Other Sources of Flooding Table 9 – Recommended national precautionary sensitivity ranges Table 10 – Groundwater Flooding Incidents during the Winter 2000/2001 Table 11 – Flood Risk Within Potential Development Areas Table 12 – Flood Defences Table 13 – Watercourse Structures Table 14 – Selection of SUDS Techniques

Figures Figure 1 – Study Area Figure 2 – Distribution of Soil Permeability and Source Protection Zones Figure 3 – Test and Itchen Catchment Figure 4 – River Thames Catchment - Types of CFMP Flood Plain Figure 5 – Development planning process for flood risk Figure 6 – Schematic of the PPS25 Flood Zones Figure 7 – SUDS Management Train Tiles A to F – Flood Maps: Zones 2, 3a, 3b; Localised and Critical Flooding Areas

Tiles AS to Fs – SUDS Maps

Glossary of Terms

Annual Monitoring Report (AMR) - Assesses the implementation of the Local Development Scheme and the extent to which policies in Local Development Documents are being successfully implemented. Appropriate Assessment – Required by the Habitats Directive (92/43/EEC) for all plans or projects which, either alone or in combination with other plans or projects, would be likely to have a significant effect on a European classified conservation site, and are not directly connected with the management of the site for nature conservation. Its purpose is to assess the implications of a proposal in respect to the site’s conservation objectives. The assessment process is not specified by the regulations but is usually an iterative process at a level dependent on the location, size and significance of the proposed plan or project. English Nature can advise on whether a plan or project is likely to have a significant effect and thus require assessment. Area Action Plans – Development Plan Documents that provide a planning framework for areas of change and areas of conservation. Areas of Outstanding Natural Beauty (AONB) - Were brought into being by the same legislation as National Parks - the National Parks and Access to the Countryside Act of 1949. They are fine landscapes, of great variety in character and extent. The criteria for designation is their outstanding natural beauty. Many AONBs also fulfil a recreational role but, unlike national parks, this is not a designation criteria. The Countryside Agency and the Countryside Council for Wales are responsible for designating AONBs and advising Government on policies for their protection. Biodiversity Action Plans (BAPs) – The UK initiative, in response to the Rio Summit in 1992, to conserve and enhance biodiversity. The plan combines new and existing conservation initiatives with the emphasis on a partnership approach and seeks to promote public awareness. Catchment Flood Management Plan (CFMP) – A strategic planning tool through which the Environment Agency seeks to work with other key decision-makers within a river catchment, to identify and agree policies for sustainable flood risk management. Core Strategy - The Development Plan Document which sets the long-term spatial planning vision and objectives for the area. It contains a set of strategic policies that are required to deliver the vision including the broad approach to development. Development Plan - As set out in Section 38(6) of the Planning and Compulsory Purchase Act (2004), an authority’s development plan consists of the relevant Regional Spatial Strategy (or the Spatial Development Strategy in London) and the Development Plan Documents contained within its Local Development Framework. Development Plan Documents (DPDs) - Spatial planning documents within the Council’s Local Development Framework which set out policies for development and the use of land. Together with the Regional Spatial Strategy they form the development plan for the area. They are subject to independent examination. They are required to include a core strategy and a site allocations document, and may include area action plans if required; other DPDs may also be included, e.g. development control policies. DEFRA - Department of Environment, Food and Rural Affairs Development. Emergency Planning – Planning for and response to emergencies such as flooding, including consideration of the resilience of emergency infrastructure that will need to operate during flooding. Environment Agency - The leading public body for protecting and improving the environment in England and Wales. Flood management and defence are a statutory responsibility of the Environment Agency; it is consulted by local planning authorities on applications for development in flood risk areas, and also provides advice and support to those proposing developments and undertaking Flood Risk Assessments. The Environment Agency reports to DEFRA.

Environment Agency Flood Zones - Nationally consistent delineation of ‘high’ and ‘medium’ flood risk, published on a quarterly basis by the Environment Agency. Flood Estimation Handbook - The latest hydrological approach for the estimate of flood flows in the UK. Flood Risk Assessment – A site specific investigation usually carried out by the site developers to be submitted as part of their planning applications. It assesses both current flood risk to the site and the impact of development of the site to flood risk in the area. Flood Risk Vulnerability - PPS25 provides a vulnerability classification to assess which uses of land may be appropriate in each flood risk zone. Formal Flood Defence - A structure built and maintained specifically for flood defence purposes. Habitable Room - A room used as living accommodation within a dwelling but excludes bathrooms, toilets, halls, landings or rooms that are only capable of being used for storage. All other rooms, such as kitchens, living rooms, bedrooms, utility rooms and studies are counted. Informal Flood Defence - A structure that provides a flood defence function, but has not been built or maintained for this specific purpose (e.g. boundary wall). JFlow - A computer river model based on routeing a flood calculated by Flood Estimation Handbook methodology along a river corridor, the levels of which are derived from a Side Aperture Radar (SAR) remote sensed Digital Terrain Model. LiDAR – ‘Light Detection and Ranging’ is an airborne terrain mapping technique which uses a laser to measure the distance between the aircraft and the ground. It therefore provides accurate topographical/contour mapping. Local Development Documents (LDDs) – the collective term for Development Plan Documents and Supplementary Planning Documents. Local Development Framework (LDF) - The name for the portfolio of Local Development Documents. It consists of the Local Development Scheme, a Statement of Community Involvement, Development Plan Documents, Supplementary Planning Documents, and the Annual Monitoring Report. Local Development Scheme (LDS) - Sets out the programme for preparing Local Development Documents. All authorities must submit a Scheme to the Secretary of State for approval within six months of commencement of the 2004 Act (thus all authorities should now have submitted an LDS). LDSs are subject to review. ‘Making Space for Water’ (DEFRA 2004) - The Government’s new evolving strategy to manage the risks from flooding and coastal erosion by employing an integrated portfolio of approaches, so as to: a) reduce the threat to people and their property; b) deliver the greatest environmental, social and economic benefit, consistent with the Government's sustainable development principles, and c) secure efficient and reliable funding mechanisms that deliver the levels of investment required. National Flood Risk Assessment (NaFRA) - Flood risk assessment that uses a risk-based approach to factor in the location, type, condition and effects of flood defences. It calculates the actual likelihood of flooding to areas of land within the floodplain of an extreme flood (0.1% or 1 in 1000 chance in any year), considering the distance from the river or the sea, and factors in the probability that the flood defences will overtop or breach. A variety of scenarios are analysed in order to determine properties at low, moderate and significant flood risk. Planning Policy Statements - The Government has updated its planning advice contained within Planning Policy Guidance Notes (PPGs) with the publication of new style Planning Policy Statements (PPSs), which set out its policy for a range of topics. Previously Developed (Brownfield) Land - Land which is or was occupied by a building (excluding those used for agriculture and forestry). It also includes land within the curtilage of the building, for example a house and its garden would be considered to be previously developed land. Land used for mineral working and not subject to restoration proposals can also be regarded as Brownfield land.

Regional Spatial Strategy - Sets out the region’s policies in relation to the development and use of land and forms part of the development plan for local planning authorities. Residual Risk - The risk which remains after all risk avoidance, reduction and mitigation measures have been implemented. River Basin Management Plan (RBMP) – A strategic tool introduced by the Water Framework Directive (2000/60/EC) which integrates the management of land and water within a river basin (river catchment or group of catchments). The river basin may cover several political areas. Statement of Community Involvement (SCI) - Sets out the standards which authorities will achieve with regard to involving local communities in the preparation of local development documents and development control decisions. It is subject to independent examination. Strategic Environmental Assessment (SEA) - A generic term used to describe environmental assessment as applied to policies, plans and programmes. The European ‘SEA Directive’ (2001/42/EC) requires a formal ‘environmental assessment of certain plans and programmes, including those in the field of planning and land use’. Strategic Flood Risk Assessment (SFRA) – a Level 1 SFRA is a district-wide assessment of flood risk, usually carried out by a local authority to inform the preparation of its Local Development Documents (LDDs) and to provide the information necessary for applying the Sequential Test in planning development. A Level 2 SFRA is a more detailed assessment produced where the Exception Test is required for a potential development site, or to assist in evaluating windfall planning applications. Supplementary Planning Documents (SPDs) - Provide supplementary information in respect of the policies in Development Plan Documents. They do not form part of the Development Plan and are not subject to independent statutory examination, but are normally subject to public consultation. Sustainability Appraisal (SA) - Tool for appraising policies to ensure they reflect sustainable development objectives (i.e. social, environmental and economic factors) and required in the 2004 Act to be undertaken for all local development documents. It incorporates Strategic Environmental Assessment. Sustainable Development – “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (The World Commission on Environment and Development, 1987). Sustainable Drainage Systems (SUDS) – Surface water drainage systems which manage runoff in a more sustainable way than conventional drainage, through improved methods of managing flow rates, protecting or enhancing water quality and encouraging groundwater recharge. A variety of types are available and can be chosen as appropriate for the location and needs of the development, and many have added benefits such as enhancement of the environmental setting, provision of habitat for wildlife and amenity value for the community. The Exception Test - If, following application of the Sequential Test, it is not possible (consistent with wider sustainability objectives) to demonstrate that there are no reasonably available sites in areas with less risk of flooding that would be appropriate to the type of development or land use proposed, the Exception Test may apply. PPS25 sets out strict requirements for the application of the Test. The Sequential Test - Informed by a Strategic Flood Risk Assessment, a planning authority applies the Sequential Test to demonstrate that there are no reasonably available sites in areas with less risk of flooding that would be appropriate to the type of development or land use proposed. Windfall Sites – Any site that comes forward which has not been identified in the local development framework. It may be considered if the housing requirement for the District or a particular settlement is not being met. World Heritage Site (WHS) – Specific sites of outstanding cultural or natural importance, listed by the international UNESCO World Heritage Committee.

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1 Executive Summary

In July 2007, Basingstoke and Deane Borough Council commissioned Halcrow to produce a Strategic Flood Risk Assessment in accordance with Planning Policy Statement 25 (PPS25): Development and Flood Risk and its accompanying document Development and Flood Risk, a Practice Guide Companion to PPS25 (December 2009). This Strategic Flood Risk Assessment will inform the plan-making process of the Local Development Framework (LDF). It will in particular inform the Core Strategy, the Sustainability Appraisals of the emerging LDF documents and any other Development Plan Documents that allocate sites.

This Strategic Flood Risk Assessment (SFRA) conforms with National and Regional Planning Policy. A SFRA is a living document which is used as a tool by a planning authority to assess flood risk for spatial planning, producing development briefs, setting constraints, informing sustainability appraisals, identifying locations of emergency planning measures and requirements for flood risk assessments. This report provides information on flood risk within the borough and guidance on application of the Sequential Test and Flood Risk Assessments for development planning.

The Thames and the Test and Itchen Catchment Flood Management Plans (CFMPs) are now available and include policy unit documents covering areas within Basingstoke and Deane. It is recommended that the planning authority aligns its flood risk policies to the CFMPs and the policy units relevant to the study area. Particular policy recommendations are as follows: • New development work should be designed to ensure flood risk is not increased at the site or in neighbouring areas, and reduced where possible (PPS25 aim). The location, layout and design of developments – in that order – are the most vital factors in managing flood risk. • Existing floodplain space should be protected, and where possible enhanced. Development in areas such as along the Rivers Test, Itchen and tributaries should take into account the need to maintain and increase floodplain storage, particularly on the Itchen. Where more floodplain space is needed within built-up areas, such as within Basingstoke, over the next 100 years use redevelopment opportunities to open up the watercourse where feasible to naturalise the river channel and provide more space for river corridors (Policy Unit documents).

PPS1: Delivering Sustainable Development and PPS25 require that LPAs should promote Sustainable Drainage Systems (SUDS). LPAs should ensure policies encourage sustainable drainage practices in their Local Development Documents. Basingstoke and Deane Borough Council has produced a Design and Sustainability Supplementary Planning Document (SPD) which provides links to more detailed information on the use of SUDS which was adopted in Autumn 2008. In this SFRA report SUDS

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techniques are discussed and guidance provided, including maps specifically designed to assist with SUDS selection.

In addition, an on-line drainage tool is being developed to assist those making planning applications for development with preparing drainage calculations or Flood Risk Assessments if they are located in, or upstream of a critical drainage area. This tool identifies whether drainage calculations are required and assists in calculating the Greenfield run off rates and required attenuation storage. This will be published as a separate document.

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2 Background Information

2.1 Terms of Reference In July 2007 Basingstoke and Deane Borough Council commissioned Halcrow to produce a Strategic Flood Risk Assessment, in accordance with Planning Policy Statement 25 (PPS25): Development and Flood Risk. Advice on flood risk within the administrative boundary of the planning authority is required to support the preparation of the Local Development Framework for Basingstoke and Deane, in accordance with government guidance and advice from the Environment Agency. This report complies with the Council’s proposal for the study dated 13 June 2007.

2.2 The Study Area The Borough of Basingstoke and Deane (the study area, see Figure 1) covers an area of 245 square miles. It is predominantly a rural borough with less than 8% of the land built up. Over 75% is either agricultural land or non-wooded Greenfield and a further 15% is covered by woodland or forest.

The population of Basingstoke and Deane was nearly 157,000 in 2005. Approximately 60% of this population live within the main urban settlement of Basingstoke. The remaining 40% live within a scattering of rural towns and villages, although in the main concentrating on a few larger rural settlements namely Tadley, Baughurst, Pamber Heath, Bramley, Whitchurch, Overton, Oakley and Kingsclere.

With two distinctive geological areas, the Thames Basin and the Hampshire Downs, the north of the borough contrasts strongly with the south. The southern two-thirds is dominated by chalk Figure 3 - Test and Itchen catchment downland, a large proportion of which forms part of the Test and Itchen catchment (see Figures 2 and 3). The northern part is influenced by deposits of clay and sand and is generally more

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impermeable, except for the chalk in the River Loddon at Basingstoke. This northern area forms part of the River Thames catchment (see Figures 2 and 4) and in contrast to the southern frequently dry, groundwater-fed watercourses, it contains a complex network of rivers and streams.

Figure 4 – River Thames Catchment - Types of CFMP Flood Plain

The River Test, a nationally famous chalk river, rises upstream of Overton and runs through the southwest portion of the borough (see Figure 1). It joins with its tributary, the Bourne rivulet, just before it exits the study area. Candover Stream is also a chalk watercourse and a tributary of the River Itchen, which rises at the

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southeast corner of the borough. The River Loddon and tributaries rise in the northeast part of the study area and the River Enbourne from the northwest.

At the time of initially compiling this SFRA, the Borough of Basingstoke and Deane fell within the regulatory areas of three Environment Agency Area Offices; the South East Thames Area covering the River Loddon catchment, the West Thames Area covering the River Enbourne catchment and the Hampshire Area covering the River Test catchment. However, since 1st April 2008, following restructuring of the Environment Agency, the South East Thames Area covers the River Loddon catchment, the West Thames Area covers the River Enbourne catchment and the Solent and South Downs Area covers the River Test catchment.

2.3 Constraints on Development due to Protected Areas Much of the borough is covered by a local, national or international ecological or landscape designation. The importance of the landscape at a national level is highlighted by the designation of approximately one third of the borough within the North Wessex Downs Area of Outstanding Natural Beauty, which is one of the larger Areas of Outstanding Natural Beauty (AONB) in the UK, and a significant proportion of the remainder of the borough is classified as ‘Areas of Special Landscape Quality’ There are 19 Sites of Special Scientific Interest (SSSIs) and 767 Sites of Importance for Nature (SINCs) that are either wholly or partly sited within the borough, the extent of which results in 1.3% of the borough’s whole area being covered by SSSI designation and 9.4% of the borough covered by a SINC designation. The borough is also located within a county that has more river and wetland sites of national importance for wildlife than any other county in England. The Test River valley is itself an SSSI and subject to an Environmentally Sensitive Areas (ESA) scheme to maintain and enhance the landscape and protect archaeological and historical features. Likewise the River Loddon is classified as a high quality chalk river warranting special protection of both the water quality and ecology. The Loddon contains many important wetland and floodplain habitats which have been designated as SINCs. It is also subject to the European Union (EU) Freshwater Fish Directive and designated as an EU salmonid river. The capacity of the River Loddon to accommodate future growth is potentially a significant constraint to development and has been the subject of ongoing research as part of the Basingstoke Water Cycle Study. The first phase of this study concludes that there is limited capacity at the Basingstoke Sewage Treatment Works for additional growth. It has also identified a significant problem with phosphorus levels in the Loddon, which are higher than the standards proposed within the Water Framework Directive for good ecological status. The second

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phase of the study was completed in October 2009 and has looked at solutions to handling waste water, such as use of different types of SUDS within developments, and seeks to address concerns about the future impact of increased sewage on the quality of the Loddon catchment.

The attractive rural environment of the borough and its historic significance is characterised by 47 Conservation Areas and over 1,800 Listed Buildings. Special attention must be paid to these, both in terms of new development within the area, and for development nearby if it could affect the local setting.

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3 Planning Context

3.1 Introduction This Strategic Flood Risk Assessment (SFRA) conforms with National and Regional Planning Policy. A SFRA is a living document which is used as a tool by a planning authority to assess flood risk for spatial planning, determine planning applications, produce development briefs, set constraints, inform sustainability appraisals, identify locations of emergency planning measures and indicate requirements for site specific flood risk assessments.

The success of the Strategic Flood Risk Assessment is dependent upon the planning authority’s ability to implement the recommendations put forward for future sustainable flood risk management, in particular that of reducing overall flood risk where possible. It is their responsibility to establish policies to ensure the development of sustainable communities, in relation to flood risk.

Emerging planning policies normally cover about 20 years in advance. Planning for flood management is a longer-term practice and SFRAs consider implications for spatial planning about 100 years ahead. The planning context of SFRAs is described in detail in Sections 3.2 to 3.7.

3.2 The EU Water Framework Directive and River Basin Management Plans An integrated approach to the management of water is a key aim of the EU Water Framework Directive (Water Framework Directive, England and Wales, Regulations 2003), which aims to integrate sustainable water planning and management. The Water Framework Directive applies to all surface and ground water bodies with significant effects for spatial and development management planning (for example within the town of Basingstoke).

A new system of statutory River Basin Management Plans (RBMP) set out the actions required to meet the Water Framework Directive, with the overall aim of achieving good water status. RBMPs are strategic plans, and will be subject to Strategic Environmental Assessment and Appropriate Assessment under the Habitats Directive. All these processes are based on multi-criteria analysis to enable correlation between the objectives. RBMPs will need to take into account existing documents and studies, including this SFRA report.

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3.3 ‘Making Space for Water’ and Catchment Flood Management Plans ‘Making Space for Water’ (DEFRA 2004) is the evolving new strategy to shape flood and coastal erosion risk over the next 10-20 years. Part of the vision of the strategy is to ensure:

‘a holistic approach to the assessment of options through a strong and continuing commitment to Catchment Flood Management Plans and Shoreline Management Plans, within a broader planning matrix which will include RBMPs prepared under the Water Framework Directive and Integrated Coastal Zone Management.’

Catchment Flood Management Plans (CFMPs) are strategic planning tools through which the Environment Agency seeks to work with other key decision-makers within a river catchment, such as the Local Planning Authority, to identify and agree policies for sustainable flood risk management. The main aims of CFMPs are to: • understand the factors that contribute to flood risk within a catchment, such as how the land is used, and • recommend the best ways to manage the risk of flooding within the catchment over the next 50 to 100 years.

3.4 National Planning Policy The Government has updated its planning advice contained within Planning Policy Guidance Notes (PPGs) with the publication of new style Planning Policy Statements (PPSs). As they are policy documents PPSs carry more weight than their predecessors.

PPS3: Housing (November 2006) specifically mentions the need to have regard to Strategic Flood Risk Assessments when local authorities are producing development plan documents relating to housing.

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In December 2006 the Government published PPS25: Development and Flood Risk which reflected the general direction set out in ‘Making Space for Water’ (see Section 3.3).

The development planning process for flood risk based on National Planning Policy is clearly demonstrated in Figure 2.2 from the Practice Guide Companion to PPS25 and it is reproduced in Figure 5 below.

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Figure 5 – Development planning process for flood risk (from the Practice Guide Companion to PPS25, figure 2.2).

PPS25 advises that regional planning bodies, in preparing regional spatial strategies, should include a broad consideration of flood risk from all sources, and set out a strategy for managing it in accordance with policies and plans prepared under the EU Water Framework Directive. Local planning authorities should prepare local development documents in their LDFs that set out policies for the allocation of sites and the control of development, which avoid flood risk to people and property where possible and manage it elsewhere. The guidance also advises that flood risk should be considered alongside other spatial planning issues such as transport, housing, economic growth and natural resources, and that the findings of the SFRA should inform the sustainability appraisal of the LDF.

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3.5 CFMPs, SFRAs and the Water Cycle Strategy in Basingstoke and Deane As mentioned in Sections 3.3 and 3.4, CFMPs and SFRAs are driven by 'Making Space for Water’ and the Water Framework Directive. The effective integration of the preparation and implementation of CFMPs and SFRAs is essential for the successful completion of future River Basin Management Plans (see Section 3.2), and furthermore, is particularly important for Basingstoke and Deane as it will assist in informing the Basingstoke Water Cycle Study (see paragraph below). It is therefore recognised that there is a need to develop a strong partnership approach between the planning authority, the Environment Agency and other stakeholders.

This has to some extent already been successfully established as part of the Basingstoke Water Cycle Study whereby the Local Authority, Environment Agency, relevant water companies and Natural England are working together to better understand the potential impact of future development on the water environment. Phase 1 of the study was completed in March 2007, whilst Phase 2 was completed in October 2009.

This SFRA report provides recommendations for the effective integration of relevant CFMP policies, the SFRA and the Water Cycle Strategy (see Chapter 8).

3.6 Regional Planning Policy 3.6.1 The South East Plan The South East Plan has been prepared by the South East England Regional Assembly (SEERA) and was adopted by the Government in May 2009. It sets out the vision for the region through to 2026. The examination into the South East Plan ran from November 2006 to March 2007, and the panel report was published in August 2007 with proposed modifications to the South East Plan published in July 2008..

The adopted South East Plan sets new requirements for housing and other developments in each district or borough. It is a requirement that the Core Strategy is in general conformity with regional planning policy.

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Policy NRM3: Sustainable Flood Risk Management, indicates that the sequential approach to development in flood risk areas will be followed. In addition, the policy states that local authorities and developers, with advice from the Environment Agency, should undertake a Strategic Flood Risk Assessment. This should have regard for climate change.

3.7 Local Planning Policy 3.7.1 Local Development Framework In accordance with the Planning and Compulsory Purchase Act 2004, Basingstoke and Deane Borough Council is preparing the Local Development Framework (LDF). This consists of Development Plan Documents (including a Core Strategy), Supplementary Planning Documents, a Statement of Community Involvement, the Local Development Scheme and Annual Monitoring Reports (see Glossary of Terms).

The current Local Development Scheme for Basingstoke and Deane (May 2009) is available on the borough council’s website at http://www.basingstoke.gov.uk/planning/ldf/localdevelopmentscheme.htm, and is updated regularly to provide an accurate picture of the timescales involved in the production of the Local Development Framework.

The documents in the LDF will gradually replace the current Adopted Basingstoke and Deane Borough Local Plan 1996-2011. The first stage of preparing the Core Strategy, the Issues and Options stage, sets out Basingstoke and Deane’s strategic planning issues and the possible options for tackling them. Consultation on this stage ran from 28th January 2008 to 10th March 2008, and the results will help to inform the next stages of the Core Strategy’s development.

Information on the Council’s current adopted planning policies can be accessed on the website at: http://www.basingstoke.gov.uk/planning/.

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4 PPS25 Flood Zones, Environment Agency Flood Zones and SFRA Flood Maps

4.1 Introduction A good understanding of the PPS25 Flood Zones, the Environment Agency Flood Zones and SFRA Flood Maps is of fundamental importance for SFRAs. Flood Maps are the key elements in a SFRA as they provide a visual understanding of flood risk across the borough, not only from watercourses but also localised flooding from surface water and groundwater.

4.2 The PPS25 Flood Zones The PPS25 Flood Zones subdivide the land, according to its spatial variation of flood probability, into four classifications; the low (Flood Zone 1), medium (Flood Zone 2) and high probability (Flood Zone 3a) flood zones and the functional floodplain (Flood Zone 3b) (see Figure 6).

PPS25 defines the flood zones as follows: Figure 6 - Schematic of the PPS25 Flood Zones.

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Flood Zone 1 - Low Probability This zone comprises land assessed as having a less than 0.1% (1 in 1000) annual probability of river or sea flooding in any year.

Flood Zone 2 - Medium Probability This zone comprises land assessed as having between a 1% (1 in 100) and 0.1% (1 in 1000) annual probability of river flooding or between a 0.5% (1 in 200) and 0.1% (1 in 1000) annual probability of sea flooding in any year.

Flood Zone 3a - High Probability This zone comprises land assessed as having a 1% (1 in 100) or greater annual probability of river flooding or a 0.5% (1 in 200) or greater annual probability of flooding from the sea in any year.

Flood Zone 3b - The Functional Floodplain This zone comprises land where water has to flow or be stored in times of flood. SFRAs should identify this flood zone (land which would flood with an annual probability of 5% (1 in 20) or greater in any year or is designed to flood in an extreme (0.1%) flood, or at another probability to be agreed between the Local Planning Authority (LPA) and the Environment Agency, including water conveyance routes).

The range of probabilities covered by each flood zone is defined in PPS25, in terms of annual average probability of flooding from rivers and the sea. The term ‘average’ means that, for example, a flood that has a 100% (or 1 in 1) probability of occurrence will have occurred once a year on average, although in any given year it may have occurred more than once or not flooded at all.

4.3 Environment Agency Flood Zones Historically the Environment Agency and its predecessors have kept formal maps of tidal and fluvial flooding to the standards required by legislation. Originally this mapping simply recorded flood events, but in 2001 PPG25 (the predecessor of PPS25 – see Section 3.4) imposed a duty on the Environment Agency to produce maps which showed the predicted extent of tidal and fluvial flood zones in England and Wales. The Environment Agency flood zones are published on their website at http://www.environment-agency.gov.uk/subjects/flood/?lang=_e, and are updated on a quarterly basis as improved modelling and recent events provide data for refining flood extents. The Environment Agency flood zones differ from the PPS25 definitions quoted in Section 4.2 in that there are only three zones; Flood Zones 1 and 2 are defined as above but the higher probability flood zone includes both the Flood Zone 3a and 3b areas in one zone called Flood Zone 3 (Flood Zone 3a + Flood Zone 3b = Flood Zone 3). The division of Zone 3 into 3a and 3b was introduced only recently, in PPS25. Furthermore, Environment

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Agency policy in relation to mapping fluvial flooding is to only include flooding caused by ‘main rivers’ (where main rivers are large or locally significant watercourses as designated by DEFRA or the Welsh Assembly Government) although when producing the outlines from historical records they may also include other types of flooding or flooding along ordinary watercourses where the source of flooding has been influenced by main river. Therefore, whilst PPS25 flood zones are not intended to include flooding from groundwater or other sources, in practice they may be included if zones have been defined based on historical records where there was a combination of sources (see Appendix A for further details about the Environment Agency flood zones).

The flood zones produced by the Environment Agency are based on current environmental conditions, so do not make any allowance for climate change.

The flood zones (both the Environment Agency and PPS25 definitions) do not rely on the presence of defences (formal or informal, see Glossary of Terms) as there remains a risk that these defences can fail through overtopping or structural failure.

4.4 SFRA Flood Maps SFRA flood maps in general reproduce the Environment Agency high, medium and low probability flood zones (see Section 6.4.2) where no other more detailed or up-to-date information is available. SFRA flood maps also include assessments of the functional floodplain and the effect of climate change on the flood zones.

However, SFRA flood maps do not only show flood zones, they also show localised flooding areas (see Tiles A to F) which relate to historical flooding at individual locations (the localised flood areas are correct up to the end of January 2009). The main causes of localised flooding (see Section 6.3.5) are high groundwater levels preventing infiltration of rainwater into the soil, and inadequate drainage resulting in build up of surface runoff. The flood risk at localised flooding areas that fall in Flood Zones 1 and 2 may in some cases be significant, with deep and frequent flooding. These areas could therefore be considered as if they were high risk areas (equivalent to the fluvial/tidal Flood Zone 3a) when applying the Sequential Test (see Chapter 9).

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5 PPS25 and its Practice Guide Companion

5.1 PPS25 - Key Aims The key aims of PPS25 are reproduced below:

‘The aims of planning policy on development and flood risk are to ensure that flood risk is taken into account at all stages in the planning process to avoid inappropriate development in areas at risk of flooding, and to direct development away from areas at highest risk. Where new development is, exceptionally, necessary in such areas, policy aims to make it safe without increasing flood risk elsewhere and where possible, reducing flood risk overall. Regional planning bodies and local planning authorities (LPAs) should prepare and implement planning strategies that help to deliver sustainable development by: Appraising risk • identifying land at risk and the degree of risk of flooding from river, sea and other sources in their areas; • preparing Regional Flood Risk Appraisals (RFRAs) or Strategic Flood Risk Assessments (SFRAs) as appropriate, as freestanding assessments that contribute to the Sustainability Appraisal of their plans; Managing risk • framing policies for the location of development which avoid flood risk to people and property where possible, and manage any residual risk, taking account of the impacts of climate change; • only permitting development in areas of flood risk when there are no reasonably available sites in areas of lower flood risk and benefits of the development outweigh the risks from flooding; Reducing risk • safeguarding land from development that is required for current and future flood management e.g. conveyance and storage of flood water, and flood defences; • reducing flood risk to and from new development through location, layout and design, incorporating sustainable drainage systems (SUDS); • using opportunities offered by new development to reduce the causes and impacts of flooding e.g. surface water management plans; making the most of the benefits of green infrastructure for flood storage, conveyance and SUDS; recreating functional floodplain; and setting back defences;

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A partnership approach • working effectively with the Environment Agency, other operating authorities and other stakeholders to ensure that best use is made of their expertise and information so that plans are effective and decisions on planning applications can be delivered expeditiously (this is currently being implemented by a series of pilot projects for DEFRA) and • ensuring spatial planning supports flood risk management policies and plans, River Basin Management Plans and emergency planning.’

5.2 Outcomes of the SFRA Process The broad planning objectives of PPS25 described in Section 5.1, effectively set the scope for the specific outcomes of the SFRA process. The SFRA, in turn, then informs forward planning and development control decisions that ensure the objectives set out above can be achieved.

It is important to reiterate that PPS25 is not applied in isolation but as part of the wider planning process. The formulation of flood risk policy and the allocation of land for future development must also meet the requirements of other planning policy, while seeking an overall reduction of flood risk. Clearly, a careful balance must be sought in these instances, and the SFRA aims to assist in this process through the provision of a clear and robust evidence base upon which informed decisions can be made.

5.3 SFRA Levels 1 and 2 There are two categories of SFRAs; a ‘Level 1’ SFRA, which analyses flood risk at a strategic level across the Local Authority area, and a ‘Level 2’ SFRA, which provides a more detailed analysis of flood risk for a specified development site.

The Level 1 SFRA provides the necessary information for use as a tool for allocating development sites in the application of the Sequential Test.

However, the Sequential Test may not be able to provide a sufficient number of suitably available sites for development within zones of lower flood risk. A Level 2 SFRA is required in the event that a development is proposed in an area of flood risk, and the vulnerability of the land use requires an Exception Test. Flood risk vulnerability (or level of resilience to damages from flooding) reflects the land uses/property types within a site, and PPS25 provides a classification system for these, ranging from highly vulnerable to water-compatible, which can be cross- matched with the flood zones to determine suitable land uses for a site (see PPS25 Annex D). For a Level 2 SFRA, the scope of the SFRA is widened to a more

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detailed investigation of flooding on the site, using more detailed modelling and considering factors such as flood depth, velocity, rate of inundation and presence of defences in order to gain a greater understanding of flood hazard within the area. The Level 2 SFRA does not negate the need for a site specific flood risk assessment which is normally required for sites within the floodplain and some outside, and for which responsibility would fall upon the potential developer to submit with their planning application.

The scope of this report is a Level 1 SFRA to inform the plan-making process of the Core Strategy and other development plan documents as required (see Section 3.7). This information will be used by the planning authority to undertake sequential testing in identifying general locations for development and to formulate strategic policies, and may in some cases assist in informing the borough council’s emergency plan. The study covers the area within the administrative boundary of Basingstoke and Deane Borough Council.

As well as identifying the level of flood risk across the borough an important strategic policy is to identify opportunities that reduce overall flood risk (as opposed to a non-increase in flood risk policy) as part of the LDF process. This approach is consistent with the CFMP aims (see Section 8.2).

5.4 The Sequential Test of PPS25 In seeking to allocate a specific type of development or land use, or determining a windfall application, planning authorities should apply the Sequential Test to demonstrate that there are no reasonably available, appropriate sites in areas of less risk of flooding.

Preference should be given to locating new development in Flood Zone 1 (see Section 4.2) because this zone has the lowest risk of flooding. However, localised flooding should also be taken into account since if this is deep or frequent enough, it may be more appropriate to treat the area as if it were a higher risk flood zone (see Section 4.4). If there is no reasonably available site in Flood Zone 1, the flood vulnerability of the proposed development can be taken into account in locating development in Flood Zone 2 and then, if still no appropriate sites are available, Flood Zone 3. For example ambulance stations, being in the highly vulnerable category, may be placed in Flood Zone 1. If no reasonably available site can be found in Flood Zone 1, it may be possible to locate it in Flood Zone 2 if it passes the Exception Test. However, it would not be acceptable in Flood Zone 3.

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Within each Flood Zone new development should be directed to sites with lower flood risk (towards the adjacent zone of lower probability of flooding) from all sources as indicated by the SFRA.

5.5 The Exception Test of PPS25 If, following application of the Sequential Test, it is not possible for the development to be located in flood zones of lower probability of flooding consistent with wider sustainability objectives, the development vulnerability should be checked for ‘compatibility’ with the flood zone using Table D.3 of PPS25. Where indicated by this table the Exception Test needs to be applied. This Test provides a method of managing flood risk while still allowing necessary development to occur. The level of detail required for an Exception Test is beyond the scope of this Level 1 SFRA; in the event that an Exception Test is needed it will be necessary to carry out a Level 2 SFRA to further define the hazards within the flood zones. This includes analysis of a number of factors such as flood probability, flood depth, flood velocity and rate of onset of flooding, and takes into account the presence of flood defences, including future policies for the defences.

The Exception Test is only appropriate for use when the Sequential Test alone cannot deliver acceptable sites, but where some continuing development is necessary for wider sustainable development reasons, taking into account the need to avoid social or economic blight and the need for essential civil infrastructure to remain operational during floods. It may also be appropriate to use it where restrictive national designations such as landscape, heritage and nature conservation designations, e.g. Areas of Outstanding Natural Beauty (AONBs), Sites of Special Scientific Interest (SSSIs) and World Heritage Sites (WHS), prevent the availability of unconstrained sites in lower risk areas.

For the Exception Test to be passed: a) it must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the Development Plan Document has reached the ‘submission’ stage (see Figure 4 of PPS12: Local Development Frameworks), the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal; b) the development should be on developable previously-developed land or, if it is not on previously developed land, there are no reasonable alternative sites on developable previously-developed land; and

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c) a flood risk assessment (FRA) must demonstrate that the development will be safe, without increasing flood risk elsewhere, and where possible, will reduce flood risk overall.

5.6 The Practice Guide Companion to PPS25 A practice guide companion to PPS25 was initially published in February 2007 and subsequently updated in December 2009. It is a ‘living draft’ web-based consultation paper (see http://www.communities.gov.uk/documents/planningandbuilding/pdf/pps25gui deupdate.pdf). It is comprehensive and incorporates many recommendations from previous Guidance documents.

The guide reaffirms the adoption of a risk-based approach to flooding by following stepped hierarchical measures at all stages in the planning process. Avoidance/prevention of inappropriate development in areas of flood risk is always the first measure, followed by substitution of different development types, control of flood risk and finally mitigation. This is summarised in Table 1, which is reproduced from Figure 2.1 of the Practice Guide Companion to PPS25.

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Table 1 – Overview of the flood risk management hierarchy (from the Practice Guide Companion to PPS25, Figure 2.1).

Following the sequential approach of PPS25 is the most important flood risk management tool for spatial planning, as this ensures the high level measures of avoidance/prevention and substitution are implemented.

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6 Study Methodology

6.1 Specific Project Outputs The specific outputs are based on the required outputs for a Level 1 SFRA, as identified in the Practice Guide Companion to PPS25, as follows: i. Map existing Flood Zones 1, 2 and 3 across the plan area (see Section 6.4.2, and Tiles A to F). ii. Map Flood Zones 1, 2 and 3 for the future climate change scenarios of 2070 and 2115 as set out in PPS25 Annex B, taking account of recommended national precautionary sensitivity ranges for peak rainfall intensities and peak river flows (see Section 6.4.4). iii. Identify areas at risk of flooding from sources other than rivers and the sea (see Sections 6.3, 6.4.2, Chapter 7, Tables 2 to 7, and Tiles A to F). iv. Identify and take into account flood risk management measures including flood defences and emergency warning systems (see Chapter 8). v. Guidance on the Application of the Sequential Test (see Chapter 9). vi. Guidance for the preparation of Flood Risk Assessments (see Chapter 10). vii. Guidance on possible mitigation measures, including the likely applicability of different sustainable drainage systems (SUDS) techniques for managing surface water runoff (see Chapter 11). viii. Identify locations where development would significantly increase the risk of flooding elsewhere (see Section 7.7).

6.2 Approach to Data Gathering The main source of data for this study has been the Environment Agency, previous Halcrow projects, a number of relevant websites, Basingstoke and Deane Borough Council, Hampshire County Council, Thames Water and Southern Water (see Audit Trail Database in Appendix B).

Priority has been given to the collection of geo-referenced information in electronic format, to ensure the effective management of the data within a GIS environment. All incoming data has been recorded on a project data register by a specialist document controller/GIS data manager, specifically designated for this project.

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The quality review of the information has been carried out by an experienced core team. The team has been able to review the collected data, assess its significance and quality, and advise on which part of the collected data should be used for the SFRA.

The main approach has been to build on the large number of strategic studies and relevant available data. The Draft Test and Itchen and the Thames Catchment Flood Management Plans (CFMPs) are now available and have provided a good foundation for catchment understanding and flood risk assessment.

Valuable flood risk information for localised flooding areas (as opposed to the ‘non-localised’ flood zones) was obtained from the drainage specialists working for Basingstoke and Deane Borough Council and Hampshire County Council. Further information was gathered from two workshops at which local community groups were invited to use their local knowledge to identify known areas of localised flooding. This collected information complemented data provided by the Environment Agency, Southern Water, and Thames Water.

6.3 Forms of Flooding and Data Limitations 6.3.1 Introduction For the purpose of this assessment, forms of flooding (also defined as sources of flooding) are divided into four categories: a) river floods; b) flooding from impounded water bodies, such as canals and reservoirs; c) groundwater flooding; d) flooding from other sources, for example, sewer and surface water.

The reason for adopting this classification is to provide an understanding of data limitations and assumptions as there are different standards for the collection of each of these types of data.

The various sources of flooding within the study area are described and shown in Tables 2 to 7 and Tiles A to F.

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6.3.2 Tidal and Fluvial Flooding Fluvial and tidal flooding (flood zones) is described in Sections 4.2 and 4.3, with further details, including assumptions and limitations, in Appendix A. However, as the Borough of Basingstoke and Deane is inland, it does not experience tidal flooding.

6.3.3 Records of Flooding from Impounded Water Bodies Records of flooding from reservoirs and canals are erratic as there is no requirement for the Environment Agency to provide information on historic flooding from canals and raised reservoirs on plans. In particular, PPS25 does not require flood risk from canals and raised reservoirs to be shown on the Environment Agency Flood Zones.

Overtopping of canals can be common as they are often fed by land drainage, and often do not have controlled overflow facilities. Occasionally, major bank breaches also occur, leading to rapid and deep flooding of adjacent land. Reservoirs with an impounded volume in excess of 25,000 cubic metres (measured above natural ground level) are governed by the Reservoirs Act and are listed on a register held by the Environment Agency. Due to high standards of inspection and maintenance required by legislation, flood risk from registered reservoirs is normally moderately low.

Within Basingstoke and Deane there are no raised reservoirs. A short section of the Basingstoke Canal runs through Basingstoke and Deane, starting near Old Basing in the far east of the borough and passing through the village of Up Nately. Unfortunately no flood zones are available for the canal (see paragraphs above). However, much of the canal within the borough is either infilled or runs through tunnels, leaving only the short section through Up Nately as open water. In 1968 the canal burst its banks flooding areas of Farnborough and Aldershot, but no flood incidents have been recorded at any point of the upstream end of the canal within the Borough of Basingstoke and Deane. Following the 1968 flooding the canal, which had been in a relatively derelict condition, has been restored to full navigable condition which enables storm flow to drain effectively down the canal to reduce the risk of future flooding.

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6.3.4 Records of Groundwater Flooding Both the Environment Agency and the planning authority keep records of individual groundwater flooding events where reported. This has been included in the map Tiles A to F.

In some cases within the catchments of the River Test and Itchen, the Environment Agency has incorporated groundwater flooding within the flood zones, where its effect is not localised (see further details in Appendix A).

A study has been commissioned by DEFRA to determine groundwater emergence zones (see Section 7.5.2). Data relating to groundwater flooding is typically sparse and thus this study provides a useful indication of where there may be a risk of groundwater flooding, even if no historical incident is recorded.

6.3.5 Records of Flooding from Other Sources Information on flooding from other sources can be obtained from local government, highway authorities, the Environment Agency, sewerage undertakers, businesses, individuals and archives such as libraries.

Until 2006 methodologies for recording flooding from sources other than tidal and fluvial were not standardised, so records held of such flooding are neither complete nor to a uniform standard. As part of DEFRA’s Making Space for Water study, a report was published by the Environment Agency titled “Flooding from other sources”. The report recommended a classification system for such flooding, which was summarised in “Source report” (JBA 2006) as reproduced in the Table 8. Currently few records of flooding from other sources contain sufficient detail to enable them to be classified in accordance with the Environment Agency classification of “flooding from other sources’’ and, indeed, many flood incidents had more than one cause.

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Type Flooding Sources Pathways Receptors Hazard Phenomenon 1 Direct runoff. Intense rainfall. All surfaces People, vehicles, Deep fast water, including road properties, with high rate of network. commercial, inundation. environment. Deep water / debris / cellar flooding. Fast water – erosion. 2 Sewerage and Heavy rainfall Surcharging from People, vehicles, Cellar and drainage system over a long manholes and properties, ground floor flooding from duration or openings in the commercial, flooding with pipe capacity intense rainfall. drainage system. environment. water quality exceedance. Surcharging. issues. 3 Sewerage and Long duration or Manholes and People, vehicles, Deep ponded drainage system intense rainfall. overflows in properties, water. Cellar and flooding from drainage and commercial, ground floor ‘other causes’ sewerage environment. flooding with (blockage and network. water quality collapse). issues. 4 Restricted outlets Heavy rainfall All surfaces and People, vehicles, Deep ponded from drainage over long drainage properties, water, and water systems due to duration. network. commercial. diverted along high flood levels unexpected in the receiving routes. watercourse. 5 Surcharge from Heavy or intense All surfaces and People, vehicles, Deep ponded small (ordinary) rainfall. drainage properties, water. and ‘lost’ network. commercial. watercourses. 6 Floodplain Heavy rainfall. Ordinary People, vehicles, Deep ponded flooding from watercourse properties, water and fast ordinary embankments commercial. flowing watercourses not and floodplains. floodplain flows. covered by the flood map (catchment area > 3km2). 7 Intense rainfall Intense rainfall Land, field People, vehicles, Fast water leading to or long duration drainage, river properties, erosion of soil overland flow heavy rainfall. and watercourse commercial, for high grade including network. environment. agricultural land. mud/debris flow Rapid rates of and flow along inundation affect old drainage. road users.

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lines, roads and Runoff from railways. land on urban fringe to flood properties. 8 Heavy, long Long duration Rural surfaces People, vehicles, Deep water, duration rainfall heavy rainfall. and field properties, runoff from leading to drainage. commercial, fields onto rural ponding on for environment. roads can cause example roads or serious hazard to fields. drivers. 9 Changes to Loss of pumping Field drains, drift People, Reduction in drainage or land / irrigation. geology, properties, capacity of land management. watercourses and environment. to drain water Reduction in land surface. away – leading to agricultural ponding and or pumping / land more surface use management runoff and / drainage erosion. Await leading to findings of increased risk of FD2120 (Defra flooding. document). Table 8: Other Sources of Flooding (from JBA 2006)..

6.4 Production of Flood Maps 6.4.1 Introduction For a Level 1 SFRA and in accordance with the Practice Guide Companion to PPS25, the current and climate change flood maps assume that any defences are not present (see Section 4.3). This is a reasonable precautionary option for the application of the Sequential Test, as it gives priority to development areas that do not require the presence and maintenance of defences.

6.4.2 Current Flood Maps (without climate change allowance) The June 2009 Environment Agency Flood Zones have been used for the production of the SFRA Flood Maps (see Tiles A to F) which means that they are based on the most up-to-date information available at the time of writing this report.

However, further updates are likely to occur as more detailed studies are carried out on river catchments. Once the Environment Agency approves these studies and incorporates the new flood outlines within their flood zone maps, the SFRA flood maps can then be updated in turn. SFRAs are living documents and, in order to ensure consistency, at least the digital flood maps should be updated in

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conjunction with Environment Agency Flood Zone updates.

The scale of the Flood Map is 1:25 000 to give both a strategic overview and reasonable clarity of general features. The Flood Map extent should not be used at a greater resolution than this.

As discussed in Section 4.2, the functional floodplain covers flooding that occurs frequently, so it may in some cases be possible to estimate its extent based upon historical data. However, there is insufficient data to determine this for the whole of Basingstoke and Deane Borough, and as this method is complex and time- consuming it is not generally appropriate for a Level 1 SFRA.

In the absence of sufficient historical data or modelling work, it was not possible to identify which part of the Environment Agency Flood Zone 3 corresponded to Flood Zone 3a and which part to Flood Zone 3b (Flood Zone 3a + Flood Zone 3b = Flood Zone 3). Therefore a precautionary principle was adopted where it was assumed that Flood Zone 3b covers all of Flood Zone 3. In this case Flood Zone 3a is represented in the flood maps merely as an outline since it is subsumed completely by the functional floodplain.

PPS25 permits only water compatible and essential infrastructure land uses in Flood Zone 3b. In the event that the Sequential Test leads to a more vulnerable development being considered for a Flood Zone 3 area, a more detailed, Level 2 assessment will be required to distinguish between Flood Zones 3a and 3b.

Flooding incident records are maintained by Basingstoke and Deane Borough Council, Hampshire County Council (highways), the Water Companies and the Environment Agency (see Tiles A to F), and these provide valuable information on previous incidents. However, historical events are not necessarily indicative of future flooding since the regulatory and/or maintaining authority (or water company) may since have made improvements which mitigate the flooding, either prompted by severe or persistent flooding, or as part of general civic maintenance and development.

As mentioned in Section 6.2, valuable information for main localised flooding areas (see Tiles A to F) was obtained from the drainage specialists working for Basingstoke and Deane Borough Council and Hampshire County Council. These

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are based on the main flood incident records where the risk is still present. In addition, two workshops were held by Basingstoke and Deane Borough Council at which local communities and resident groups were invited to use their local knowledge to provide information on any known areas of localised flooding. The SFRA flood maps also provide information from Thames Water (flooding that occurs within a four digit post code) and Southern Water (indicated as points).

The Environment Agency also maintains flood incident records but these mainly relate to groundwater incidents (indicated as points in the maps) and, for the Hampshire Area, areas that occur in the vicinity of main rivers. This information is included within this SFRA, however, the Environment Agency should be consulted in relation to flood incident records during the application of the Sequential Test, (as explained in Section 9.2), to check that the most up-to-date data is used.

6.4.3 Effects of Climate Change In October 2006, DEFRA published the document Flood and Coastal Defence Appraisal Guidance FCDPAG3 Economic Appraisal (Supplementary Note to Operating Authorities – Climate Change Impacts) identifying the climate change impacts to be considered in undertaking flood risk appraisals in the United Kingdom. In addition to sea level rise of approximately 1 metre in southeast England over the next 100 years, the document also sets out how short duration rainfall could increase by 30% and river peak flows by 20%, and suggests Winters will become generally wetter. These effects will tend to increase both the size of flood zones associated with the sea and rivers, and the amount of flooding experienced from “other sources”.

During the life span of new commercial and residential developments, it is expected that peak river flows will first increase for a short period by 10% (2007- 2025) and for the remaining period by 20%. Table 9 (reproduced from PPS25) indicates that an increase of 20% in peak river flow is estimated between years 2025 and 2115.

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Parameter 1990 to 2025 2025 to 2055 2055 to 2085 2085 to 2115

Peak rainfall intensity +5% +10% +20% +30%

Peak river flow +10% +20%

Offshore wind speed +5% +10%

Extreme wave height +5% +10% Table 9 - Recommended national precautionary sensitivity ranges (from PPS25, table B.2).

A lifespan of 60 years is used for a commercial development, and 100 years for residential development, e.g. a commercial building built in 2008 could be assumed to reach the end of its design life in 2068 – so an appropriate allowance for an increase in the peak rainfall intensity would be 20%. It should however, be noted that, where possible, a managed adaptive approach to the effects of climate change should be adopted, which will allow for further adaptation in the future, as understanding of the effects of climate change improves (further guidance on the ‘managed adaptive approach’ can be found in the DEFRA FCDPAG3 supplementary note on climate change).

6.4.4 Climate Change Flood Maps As recommended by the Environment Agency, it has been assumed that commercial and residential developments planned in the LDFs will reach the end of their life in 2070 and 2115 respectively (based on projecting the lifespans quoted in Section 6.4.3). Based on an estimated increase of 20% in peak river flow (which is expected to occur during these lifespans) the following precautionary rules have been adopted for this Level 1 SFRA:

C1) ‘Climate Change’ functional floodplain Zone 3b = Current Flood Zones 3b + 3a = Current Flood Zone 3

C2) ‘Climate Change’ Flood Zone 3a = Current Flood Zone 2

Many previous flood mapping studies by Halcrow confirmed that increases in flows by 20% to Flood Zone 3, result in flood extents which are in general smaller than Flood Zone 2, so this is a conservative rule.

C3) ‘Climate Change’ Flood Zone 2 = Current Flood Zone 2

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There is little certainty about the effect that climate change will have on very extreme fluvial events, but it is currently assumed that ‘Climate Change’ Flood Zone 2 is slightly larger than Current Flood Zone 2. However, at the scale of these SFRA flood maps, it is reasonable to assume that the difference is indistinguishable.

The current flood maps (Tiles A to F) can therefore be used to take account of climate change predictions along the fluvial reaches by applying rules C1, C2 and C3. In applying the Sequential Test, the climate change scenarios should be used in order to take into account the expected lifetime of the development.

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7 Flood Risk in the Study Area

7.1 Introduction All forms of historical flooding have been considered, both in isolation and in combination. For references to locations within the study area see the set of maps, Tiles A to F.

7.2 Overview of Catchments As mentioned in Section 2.2, The River Test emerges from chalk springs (Upper Chalk aquifer, see Figure 1), and eventually flows into Southampton Water at Red Bridge next to Totton. The upper Test area is predominantly rural. The River Loddon rises at West Ham Farm, Basingstoke, and flows in a north-easterly direction for approximately 45km to its confluence with the River Thames to the west of Wargrave. In the upper Loddon catchment, which falls within the study area, the river is fed by springs which have their source in the permeable Upper Chalk aquifer.

The River Enbourne runs along the northern boundary of the borough through a relatively impermeable, narrow and long catchment, until just west of Tadley where it turns north to join the River Kennet. Flash flooding occurs along the River Enbourne and its tributaries however there are no records of major flooding of properties, due to its rural nature and small catchment area.

An analysis of the flood zones within Basingstoke and Deane indicates that about 2.8% of the borough is within the floodplain (i.e. within the areas covered by Flood Zones 2, 3a and 3b).

Further statistics are available from the National Flood Risk Assessment (NaFRA) which give an indication of the level of risk to property within the borough. Data from the most recent survey in 2006 records that 1421 properties are within the 1 in 100 flood outline (i.e. Flood Zone 3a and 3b). A more detailed analysis, for insurance purposes, classifies properties into being at low, moderate and significant risk: • Properties at significant risk have a greater than 1 in 75 (1.3%) chance of flooding in any year. There are 706 residential and 63 commercial properties at significant risk.

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• Properties at moderate risk have a 1 in 75 chance or less but greater than a 1 in 200 (0.5%) chance. There are 53 residential and 1 commercial properties at moderate risk. • Properties at low risk have a 1 in 200 chance or less of flooding each year. There are 784 residential and 69 commercial properties at low risk.

7.3 History of Flooding The flood history of the rivers Test and Loddon is characterised by high groundwater-fed baseflow which, combined with storms, may lead to overtopping of river banks. Localised groundwater flooding has been reported in the upper parts of the Loddon catchment as a result of high groundwater levels around North Warnborough in the River Whitewater sub-catchment, at Basingstoke town centre, and in the upper reaches of the River Lyde and the Upper Loddon. Similar problems affect the River Test. Flash flooding is rare in both catchments.

Notable catchment-wide flood events on the River Loddon include March 1947, September 1968, June 1971, November 1974, February 1990, October 1993 and Autumn/Winter 2000.

Records of flooding for Deane (on the River Test) indicate 3 properties affected in the period February to March 1995 due to high groundwater levels followed by fluvial flooding, and 4 properties between December 2000 and May 2001, again resulting from high groundwater levels/spring flows.

Sewer flooding is recognised as an important local issue within the borough and thus historical flooding from sewers is important for identifying areas where capacity may be limited. Several areas of Basingstoke are known to be susceptible to flooding from sewers and these have been indicated on the maps (see Tiles B, C and F).

7.4 Flooding Mechanism for Permeable Catchments Four basic flooding mechanisms that affect permeable catchments can be defined: • High groundwater levels producing high baseflow in the river channels which exceeds channel capacity; • High groundwater levels which rise above the ground surface locally; • Localised surface water runoff (direct from overland flow);

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• Sewer flooding.

Groundwater flooding is prevalent. This was demonstrated during the Autumn/Winter 2000/2001 flood event, when prolonged heavy rainfall occurred and the elevated water table was considered to be the largest cause of flooding. The long duration rainfall over the duration of the event was considered to be greater than a 1% annual probability (1 in 100 year) event, whereas the short duration rainfall during the event was considered to have a 10% (1 in 5 year) to 20% (1 in 10 year) annual probability.

The overall picture of flood risk within Basingstoke and Deane highlights the concern that progressive development has encroached on the natural floodplain (see flood zones in Tiles B, C, E and F). It also reinforces the need to take a more holistic approach to flood risk management and identify opportunities to reduce the overall flood risk in future development. The Thames CFMP for this area and its two subsequent policy unit documents, the Basingstoke policy unit and the Loddon Policy Unit (see Section 8.2 and Appendix C) in conjunction with this SFRA should be used to inform necessary policies to address this need.

7.5 Groundwater Flooding 7.5.1 Local Experience of Groundwater Flooding During the Winter of 2000/2001, extreme rainfall conditions prevailed across much of Hampshire. Numerous flooding incidents were recorded, many of which related to elevated groundwater levels and abnormally high spring flows. The Environment Agency, Southern Region commissioned an investigation into these flooding incidents which assessed flooding incidents at over 100 locations in the County. Within Basingstoke and Deane, these investigations identified a number of such incidents, specifically as shown in Table 10: Groundwater-related incidents from the Environment Agency, Southern Region general database of flooding are shown in Table 6.

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Village River No. of Types of event Period of Catchment affected flooding properties Ground floor and cellar. External Dec 2000 – Deane Test 4 flooding (roads May 2001 etc). Ground floor and St Mary Bourne Rivulet external with Dec 2000 - 2 Bourne (Test) sewage and Mar 2001 flooded roads. Ground floor and Bourne Rivulet external with Stoke 4 Dec 2000 (Test) sewage and flooded roads. Ground floor and Preston Candover Nov 2000 - 12 cellar. External Candover Stream (Itchen) May 2001 flooding on roads. Chilton and Ground floor. Candover Nov 2000 - Brown 1 External flooding Stream (Itchen) May 2001 Candover on roads.

Table 10: Groundwater Flooding Incidents during the Winter 2000/2001.

As shown, the effects of such groundwater flooding events lasted for an extended period, in some places in excess of 3 months.

Groundwater flooding was also experienced within Basingstoke Town, where six subways were blocked. Rural roads and sewage services were also severely affected. To the north and northeast of Basingstoke, groundwater flooding incidents were recorded in a number of locations including Sherbourne St John, Nateley Scures and Phoenix Green. The Environment Agency Thames Area groundwater records are shown in Table 7.

These groundwater flooding events were at their most significant in areas underlain by the chalk, and indeed recent research tends to suggest that chalk aquifers are more prone to groundwater flooding than other aquifers.

7.5.2 Recording, monitoring and assessment of groundwater flooding Subsequent to the incidents of groundwater flooding in 2000/2001, and similar (though less severe) events in 2002/2003, DEFRA has commissioned research

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into the most appropriate way to monitor, record and collate data from groundwater flooding and how this information may be used in groundwater flood risk assessments. An initial Scoping Report (Jacobs 2004) has led to a further programme of research under the Making Space for Water programme. This research is intended to produce recommendations for the effective monitoring and collation of groundwater flooding information; to identify any organisational and funding changes required to implement this; and to influence the direction of the strategic overview role of the Environment Agency with respect to groundwater flooding.

Prior to the introduction of these measures, any development within the study area must take into account the potential for groundwater flooding, if necessary through an evaluation of the historic incidence of such events. The Jacobs Scoping Report includes a set of maps indicating groundwater emergence zones (defined as the appearance of groundwater at the land surface or below the surface in sub-surface structure such as excavations, cellars, communication conduits and tunnels) for each of the Environment Agency administrative areas in England. The maps covering Basingstoke and Deane are provided in Appendix D. Once appropriate procedures have been developed, groundwater flood risk assessment measures should be applied.

7.6 Localised Flooding Areas The localised flooding areas identified by the planning authority and Hampshire County Council are shown in Tiles A to F and details are provided in Table 4.

7.7 Planned Development Areas As noted in Section 3.7, the issues and options stage of the Core Strategy was drafted and put out to public consultation February 2008; a copy of the document is available at http://www.basingstoke.gov.uk/planning/ldf/corestrategy.htm. This puts forward a target for building new housing of between 740 to 945 new homes per year. To comply with the South East Plan, this housing should be focused within the current built up areas of the Western Corridor/Blackwater Valley, including the towns of Basingstoke, Tadley, Bramley, Kingsclere and Oakley, with some more limited development outside these areas such as Overton and Whitchurch. In accordance with Government Guidance, use of suitable Brownfield development sites should be maximised, although the need to avoid excessive infilling, which could harm the quality of life of existing residents, is noted. There will still be a requirement for development on Greenfield land,

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which the South East Plan states is likely to consist of one or more urban extensions to Basingstoke, although sites around the other towns mentioned above are also being considered. As well as the houses themselves, it may be necessary for development to include other infrastructure, such as premises for business, retail, healthcare, education and leisure, in order to maintain sustainable communities.

As the exact locations for new developments are not yet known, Table 11 summarises the main flood related issues for each of the settlements mentioned above. More detailed information can be obtained from Tiles A to F once the site locations are known.

Town Tile Types of flood risk*

Basingstoke C, F The beginning of the floodplain of a River Test tributary passes the campsite in the southern tip of the town, and there is one localised flooding area in Cliddesden. Other than these the southern part of the town is at relatively low risk of flooding.

However, above Pack Lane/The Harrow Way there is significantly more flooding. Several branches of the River Loddon floodplain run through Basingstoke, putting a number of properties at risk. The Loddon is ephemeral through parts of Basingstoke and could be at risk of groundwater flooding along the valley further upstream of where the Loddon normally emerges. The groundwater emergence maps indicate a potential susceptibility to groundwater flooding, mainly in the southern part of Basingstoke, but also in Popley, Chineham and Sherbourne St John. There are numerous incidents of localised flooding, both due to drainage incapacity and to high groundwater, the latter of which is particularly concentrated in the area around Buckskin Lane.

Tadley B Central Tadley has experienced fluvial flooding along Bishop’s Wood Stream, with Swains Road and the western edge of the Mount Pleasant green area also suffering fluvially-related flooding. There are numerous incidents of flooding due to drainage incapacity of both the surface water and foul water systems, and a couple of incidents of groundwater flooding. The groundwater emergence maps show a potential susceptibility to groundwater emergence just south of Tadley.

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Bramley C Development in Greenfield areas to the south of the town could be at risk of fluvial flooding from Bow Brook. Within the town there are several areas of localised flooding, at least one of which (B068) may be related to backing up from Bramley Green Stream, although the floodplain itself is not expected to affect Bramley.

Kingsclere A, B The floodplain of the Gailey Brook runs through Kingsclere, although so far no incidents of the stream overtopping are known of. Surface runoff is a problem for The Dell in the southeast of the town (B104), and some gardens in the northwest of the town have been flooded by backwater from a nearby ditch (B002). Whilst no records of groundwater flooding have been found, this area is within the groundwater emergence zones.

Oakley B, E Oakley is at relatively low risk of flooding, with only a couple of locations having suffered flooding by the drainage system. Outside the town, a couple of the tributaries of the Test have floodplains which approach to within a kilometre of the town, and there was an incident of localised flooding along the railway line to the southwest of the town. A potential susceptibility to groundwater flooding is indicated in the groundwater emergence maps.

Overton D, E The floodplain of the River Test runs through the town. There are some properties within the floodplain (although so far no historical instances of flooding has been recorded for these), but in general there seems to be adequate green space around the river to accommodate the floodplain – further development should avoid encroaching on this area. There are 3 instances of flooding from the drainage system; all of these are close to the river so may be partly due to backing up at high water level. A potential susceptibility to groundwater flooding is indicated in the groundwater emergence maps.

Whitchurch D Whitchurch is at risk of fluvial flooding from the River Test. There are 2 instances of flooding from the drainage system, both of which are close to the river so may be partly due to backing up at high water level. A potential susceptibility to groundwater flooding is indicated in the groundwater emergence maps.

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Table 11: Flood Risk Within Potential Development Areas. *see Chapter 7 and Tables 2 to 7 and 10 for further details.

The development will have a further effect on neighbouring watercourses as the additional properties will cause an increase in foul water, after treatment, being discharged from the water treatment plants into the rivers. Discharge from Basingstoke, Bramley, Kingsclere and Tadley are likely to be into rivers on low permeability soil and thus major development work could result in significant increase in flow downstream of the discharge. Overton and Whitchurch, and possibly Oakley as well, are likely to discharge into the River Test so the affect of the additional houses may, apart from immediately after discharge, be less significant if water is able to infiltrate into the underlying chalk as it travels downstream. In rivers with low flow the additional discharge may be beneficial in maintaining water levels, particularly in drought periods, although if the percentage of effluent is too high then water quality may be adversely affected. In rivers where flow is close to channel capacity, the additional water may pose a flood risk. In particular, this is likely to be an issue for Basingstoke where much of the development is expected to take place. Historical data suggests several areas of the drainage system are close to capacity, and these are often close to the Loddon so may be related to backing up of water unable to escape into the river, particularly as it is culverted for much of the way through Basingstoke. It may be necessary to incorporate storage areas to accommodate water in times of high flow and flood, either as part of the watercourse (online) or as a separate feature into which water could be diverted and then later returned (offline). One of the recommendations of the Thames CFMP (see Chapter 8), is to encourage opening up of the watercourse, which would give the advantage of allowing more flexibility of options for designing storage. Furthermore, future development may offer the opportunity for additional financial resources to enable improvement of the drainage system, where appropriate design may benefit both the new and existing development.

7.8 Effect of Development on Flood Risk Elsewhere In addition to consideration of flood risk within the development site, it is important to consider the effect on the surrounding area. Where development takes place on an area subject to flooding, it may change the pattern of flood risk. In particular additional built-up area may reduce the space for flood water causing it to be diverted elsewhere. Development planning should include measures to avoid this, using techniques such as providing alternative flood plain storage or use of SUDS (see Chapter 11).

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Furthermore, it is not sufficient to assume that locating development away from Flood Zones 2 and 3 and localised flooding areas and the use of sustainable drainage systems (SUDS) will automatically render flood risk to third parties adequately low irrespective of location. A situation may arise in which there is no spare capacity at an outfall (for example a surface water drainage system located a few kilometres downstream from the proposed allocation). The approach could be to produce a specific policy in which development will not take place until the downstream surface water drainage system is upgraded (unless an alternative outfall is identified and subject to approval by the planning authority and the Environment Agency). It is important to note that a local upgrade in channel or pipe capacity may increase flood risk downstream which may result in the need for storage or wetland areas to attenuate flows. All surface water drainage systems need to consider the requirements in the document ‘Rainfall runoff management for developments – Interim national procedure’ including controlling the peak rates, the additional volume, and exceedance (see Appendix E).

The study of flood risk in this chapter leads to the conclusion that careful investigation of local flood risk (with a detailed investigation of flood incident records, management and maintenance issues) is required at most locations in the borough before development is allocated. A suggested policy approach for localised flooding issues could be as follows: ‘No development will be allowed unless it is demonstrated that: a) dry access and egress is provided (see Section 10.7), b) the receiving watercourse has sufficient capacity and c) flood risk is reduced where possible, or at least not increased, in the development and in surrounding areas’

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8 CFMPs, Flood Management Measures, Flood Warning Systems and Defences

8.1 Introduction SFRA reports are ‘living documents’ which should be updated when Environment Agency Flood Zones and other relevant documents (for example Catchment Flood Management Plans (CFMPs), Strategies, Flood Warning Systems) are updated. It ensures a consistent and integrated approach to flood risk management.

8.2 Catchment Flood Management Plans A Catchment Flood Management Plan (CFMP) is a high-level strategic planning tool used to identify key factors contributing to flood risk within a river catchment, such as how the land is used, and recommend the best ways of managing flooding over the next 50 to 100 years to ensure sustainable policies and an integrated approach to land use planning and management. There are four main stages in preparing a CFMP and a report is prepared for each stage. The first stage leads to the Inception Report, where a summary of relevant flood risk issues and readily available catchment data is produced. The Scoping Report builds on this data to present a fuller understanding of the catchment, and sets out possible future scenarios to be assessed at the next stage. The Draft CFMP extends this to identify policy options and develop a plan for actions on the preferred policy and monitoring of its effect. The Final CFMP updates the draft version based on the final consultation responses. Both the Scoping and Draft Report are issued for full public consultation, and following completion, the CFMP is formally reviewed on a periodic basis - generally every six years.

Basingstoke and Deane Borough falls within two CFMP boundaries; the Thames (for the River Enbourne and River Loddon) and the Test and Itchen (for the upstream River Test and Bourne Rivulet, one of its tributaries, and the Candover Stream, a tributary of the Itchen). The Thames CFMP has now reached the final version and is available from the Environment Agency.

The Test and Itchen CFMP is currently being finalised and is available on the Environment Agency website

The Thames CFMP includes policy unit documents covering Basingstoke town, the River Loddon and the River Kennet catchment (see Appendix C).

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The Basingstoke policy document concentrates on the River Loddon within the town of Basingstoke where the river is characterised by a developed floodplain and a largely culverted or concrete channel. Because of the developed nature of the catchment, opportunities to reduce flood risk are highly constrained. The policy therefore focuses on measures to naturalise the river by opening up the watercourse where feasible and moving development back from the river. This will be a long term policy enacted as redevelopment opportunities arise in the next 100 years. The specific aims from the policy document are quoted below: • Avoid further development of Greenfield sites within the floodplain. Appropriate application of the Sequential Test under PPS25 should safeguard existing floodplain. • Surface water arising from Greenfield sites outside of the floodplain should, as far as is practicable, be managed in a manner to mimic surface water flows before the proposed development. Where the redevelopment of Brownfield sites can reduce the risk of flooding to known locations, seek to reduce runoff to better represent Greenfield conditions. • Multiple benefits are realised from the redevelopment of sites in the river corridor. For instance, layouts to include set back from the river so that ultimately river corridors can be re-established and buildings are resilient to flooding. In Basingstoke this may offer an opportunity to reduce the length of culvert, recognising the need to be able to accommodate periods of low flow in the River Loddon. • To gain a more complete understanding of surface water and drainage related flooding so that any future improvements are part of a wider strategy for addressing these sources of flooding. A Surface Water Management Plan (SWMP) or Integrated Urban Drainage Plan (IUDP) could define the future approach. This is important in this policy unit because of both the existing and future risk. • Continue to reduce the impact of low order flooding in urban areas (up to a 10% to 20% AEP flood – 1 in 10 to 1 in 5 year return period) by maintaining conveyance where it is both effective and sustainable to do so.

The Loddon policy document relates to the rest of the River Loddon within the Borough of Basingstoke and Deane which still retains fairly extensive floodplains. In this case the policy focuses on maintaining, and in some places enhancing, the floodplain, and where the river runs through developed areas helping buildings and communities become more resilient to flooding. The specific aims from the policy document are quoted below:

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• Maintain the capacity and function of the undeveloped natural floodplain to retain water so that it can continue to reduce the impact of low order flood events to people and property. • Seek to enhance the capacity of the undeveloped natural floodplain. Recognising that this will require structural measures, this is more likely to be achievable upstream of sizeable communities at risk from flooding where the social, economic benefits are more clear-cut. • Align the objective of maintaining or enhancing floodplain capacity with expansion and enhancement of floodplain environments, particularly BAP habitat. • Continue to reduce the impact of low order flooding in urban areas (up to a 10% to 20% AEP flood – 1in 10 to 1 in 5 year return period) by maintaining conveyance where it is both effective and sustainable to do so. • Reduce the consequences of flooding through continued action to raise public awareness of flooding, tailoring the advice and approach (e.g. community based) to ensure those ‘at risk’ take appropriate action to respond to flooding. • Safeguard the existing undeveloped natural floodplain through the appropriate application of the Sequential Test within PPS25. • Particularly in the Lower Loddon towns such as Winnersh, Charvil and Lower Early, seek to maintain or restore river corridors so that urban areas can better accommodate flooding (location and layout) and the buildings are more resilient to flooding (design). In the long-term this should be achievable through redevelopment. It must be recognised that this is a long-term objective. • In the Lower Loddon towns, progress investigations to conclude which approaches would be most suitable to manage existing and future flood risk. This could be to manage the probability of flooding (for example through defences), or the consequences (for example through resilience). Specifically assess the viability of these options in the Lower Loddon. Option selection should be based on what is most effective and sustainable and not short-term factors (for example, the ease of capital funding streams).

The Kennet policy document (see Appendix C) includes the River Enbourne and its tributaries which flow along the northern boundary of the borough. The policy focus and specific aims here are very similar to those in the Loddon, with an overall emphasis on maintaining the capacity and function of the undeveloped

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natural floodplain to retain water, so that it can continue to reduce the impact of low order flood events to people and property.

The Bourne Rivulet and Candover Stream tributaries are not specifically covered by the Test and Itchen CFMP, and therefore it is recommended that the policies for the upstream River Test and Upstream River Itchen, respectively, are applied to these areas. The relevant policies for these catchments are Policy Unit C for the upstream River Test, and Policy Unit G for the upstream River Itchen.

The Policy Unit C area lies over permeable chalk and is largely rural in nature, but contains a number of small towns and larger villages. Flood flows are dominated by baseflow from the upstream chalk aquifers and usually caused by excessive seasonal rainfall through the Autumn and Winter. Therefore frequency of flooding is relatively low but when it does occur, tends to be prolonged. The chosen policy for this area is to ‘continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline)’. Whilst this policy allows for the potential of future minor losses within the policy unit, it is considered to support economic and social sustainability over the whole Test catchment by prioritising significant gains elsewhere. Present actions to control flood risk (such as flood warnings) will continue, and monitoring will be necessary to ensure that the policy can be reviewed should flood risk change in the future. The proposed actions for this policy unit area are: • Understanding of flood risk in this Unit should be enhanced through a pre- feasibility study. This should concentrate on the present and estimated future flood risk at Stockbridge, though it should also identify any other significant risk locations. Any study will need to consider the BAP Habitat objectives and the need to protect or enhance the River Test SSSI. • Develop the River Test Water Level Management Plan to identify and agree water level management that meets the need of flood risk management and the enhancement of wetland habitat.

Policy Unit G is similar to Policy Unit C as it lies over permeable chalk and is predominantly rural with some scattered villages. Likewise, flood flows are dominated by baseflow from the upstream chalk aquifers leading to relatively infrequent but prolonged flooding. However, in this area there is sufficient space that the chosen policy is to ‘take action to increase the frequency of flooding to deliver benefits locally or elsewhere’. This policy is expected to maintain the

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present low level of flood risk to properties and people within the area, whilst assisting in reducing flood risk downstream. However, more investigation into this scheme is yet required. The proposed actions for this policy unit area are: • A pre-feasibility study should be carried out to investigate the development of washland areas, increasing the frequency and depths of flooding, within the Middle Itchen (Policy Unit G). If feasible and sufficiently effective (in economic, social and environmental terms) then this aspect would be incorporated within the ‘Flood Risk Management Strategy’ for Winchester (Policy Unit E). The Study should focus on maximising flood storage potential and investigating potential creation of new BAP Habitat and improvement of conditions for existing BAP Habitats and Species. Also it should investigate opportunities to improve the favourable condition of the River Itchen SSSI/SAC (working in accordance with the Water Level Management Plan) and of ensuring no adverse impacts on downstream designated sites. • Develop a Land Management Plan to explore the potential for changes in land use and land management practices through the Middle Itchen (Policy Unit G), working in partnership with the agricultural industry to seek to reduce direct runoff into watercourses, which is currently introducing significant sediment and diffuse pollutants into the drainage network.

It is recommended that the planning authority aligns its flood risk policies to the CFMPs and in particular the five policy units relevant to the study area. Particular policy recommendations are as follows: • New development work should be designed to ensure flood risk is not increased at the site or in neighbouring areas, and reduced where possible (PPS25 aim). The location, layout and design of developments – in that order – are the most vital factors in managing flood risk. • Existing floodplain space should be protected, and where possible enhanced. Development in areas such as along the Rivers Test, Itchen and tributaries should take into account the need to maintain and increase floodplain storage, particularly on the Itchen. Where more floodplain space is needed within built-up areas, such as within Basingstoke, over the next 100 years use redevelopment opportunities to open up the watercourse where feasible to naturalise the river channel and provide more space for river corridors (Policy Unit documents).

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8.3 Flood Warning Systems In England and Wales the Environment Agency operates a flood warning service in areas at risk of flooding from rivers or the sea. Using the latest available technology, Agency staff monitor rainfall, river levels and sea conditions 24 hours a day and use this information to forecast the possibility of flooding. If flooding is forecast, warnings are issued using a set of four easily recognisable codes. (For further details about this service see the Environment Agency website at http://www.environment- agency.gov.uk/subjects/flood/826674/829803/946278/?lang=_e).

Each of the four codes indicates the level of danger associated with the warning. The codes are not always used in sequence; for example in the case of a flash flood a Severe Flood Warning may be issued immediately, with no other warning preceding it. • A Flood Watch would be issued when water levels along the river are forecast to overtop the banks. Flood watches are generally issued for the whole of the river catchment. • A Flood Warning is issued when the Environment Agency anticipates flooding to property. Flood Warnings are issued for a specific flood warning area within a catchment, for example the River Loddon from Basingstoke to Swallowfield. • The trigger for issue of a Severe Flood Warning is dependent on a number of factors, but is essentially used when there is thought to be extreme danger to life. This is a decision that would be made on the basis of river levels, large numbers of properties affected, response required by emergency services and local authorities, likely impact on major infrastructure etc. Severe Flood Warnings are issued for a specific warning area. • The All Clear is issued once Flood Watches or Warnings are no longer in force for the area.

The Environment Agency aims to give a two-hour warning in advance of any flooding taking place. However in certain cases this may not always be possible.

All warnings are highly dependent on the Environment Agency’s ability to forecast. They have a comprehensive raingauge network and have direct access to Met Office radar products which show rainfall intensities and amounts.

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As part of an improvements programme, the Environment Agency will be improving the flood warning service within the study area through the development of community based Flood Warning Areas. However, due to the flashy nature of this part of the catchment and being at the top of the catchment, it will be difficult to provide lead times for advance warning of flooding.

8.4 Defences and Future Flood Risk Management Schemes The Environment Agency maintains a database of informal and formal defences (see Tables 12 and 13). This records information such as the standard of protection (which is a measure of the magnitude of flooding the defence can offer protection against), type of ownership and the condition of the defences. An understanding of these factors is important for understanding the potential residual risk (overtopping for large events, breaching or blockage) when considering locating sites in areas behind defences. Level 2 SFRAs and individual flood risk assessments need to consider this and use the SFRA information as a starting point.

Flood Risk Management Schemes encompass a variety of approaches to defending a settlement, or part of a settlement, from flooding and range from works such as flood walls and embankments, channel diversions and enlargements, addition or removal of structures such as culverts or weirs, hard and soft sea defences, flood storage areas, pumping stations, channel maintenance such as dredging or vegetation clearance, environmental improvements such as wetland restoration, and changes in land management practices to reduce storm runoff. In the case of schemes such as flood storage, wetland areas or land management restrictions, since this land has been specifically designated to aid flood defence, it should be considered as a spatial constraint to development proposals. Structures, such as culverts, may also act as a constraint to future development since access will need to be maintained.

Currently there are no areas within Basingstoke and Deane that are potentially allocated for Flood Risk Management Schemes by the Environment Agency or others.

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9 Guidance on the Application of the Sequential Test

9.1 Introduction As described in Chapter 5, the application of the Sequential Test can be summarised as follows: 1) Based upon the flood zones within this SFRA, development should be first located in areas at least risk from flooding (Flood Zone 1). Only where there are no reasonably available alternative sites in areas with a lower probability of flooding that would be appropriate to the type of development or land use proposed, should development be located in Flood Zones 2 or 3. 2) Within higher probability Flood Zones 2 and 3, give preference in the order Flood Zone 2, then Flood Zone 3a, and finally Flood Zone 3b only as a last resort.

Having applied the Sequential Test, the development vulnerability (see Section 5.3) should be checked for ‘compatibility’ with the flood zone using Table D.3 of PPS25. Having followed points 1 and 2 above, where indicated by Table D.3 of PPS25, either: • where the development is compatible a site specific Flood Risk Assessment should be provided to demonstrate that the development is safe and will not increase flood risk; • the Exception Test needs to be applied – it should be noted that where there is a need to apply the Exception Test it is beyond the scope of this ‘Level 1’ SFRA, and a ‘Level 2’ SFRA must be commissioned to further consider the actual variation of hazard posed within flood zones; • or the development should not be permitted.

At all stages of the planning process, the impacts of climate change should be taken into account.

The following steps provide additional guidance to that from PPS25 and its Practice Guide, and have been produced in consultation with the Environment Agency. They provide details on how to take account of other sources of flooding (and not just the flood zones) during the application of the Sequential Test, and as

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part of a Sustainability Appraisal. To apply this approach it would need to be written into the LDF policies.

9.2 First Step – Strategic Overview of Flood Risk for all Potential Areas The recommended initial step is to determine broad extents of potential land allocations in large scale maps showing the most up-to-date flood zones (i.e. the SFRA Flood Maps -Tiles A to F). Summary tables of flood risk issues are then prepared for each location, indicating if the potential areas overlap Flood Zones 2, 3, localised flooding areas or if there are records of previous flood incidents shown in the maps. As mentioned in Section 7.7, particular care should be taken by identifying allocations that could increase flood risk elsewhere (for example upstream of areas with limited drainage capacity) and sites which, whilst not subject to flooding themselves would suffer a lack of dry access due to surrounding flooding.

9.3 Second Step – Analysis of Flood Risk Issues The next step begins the Sequential Test by analysing all potential sites within Flood Zone 1. Whilst locations in Flood Zone 1 are at low risk of flooding from rivers or the sea, they may still be subject to other sources of flooding. Sites with flood risk issues, including those that do not have dry access routes during flood events, should be identified and for these sites an assessment of likely significance of flood risk is then carried out in terms of likely probability of flooding and potential consequences/flood damages. (Advice from a drainage specialist may be required, such as the SFRA consultant, the Environment Agency, a highways drainage engineer or the planning authority drainage specialist.) The purpose is to identify sites with significant flood risk including a high probability of flooding, with deep water and high velocities causing significant flood damages which could result in loss of property and potentially loss of life.

Ideally the land uses most vulnerable to flood risk should be located in Flood Zone 1. However if a site within Flood Zone 1 is identified as having significant flood risk from other sources of flooding it would now be considered as if it was in the High Probability Flood Zone 3a for further application of the Sequential Test (see Section 9.6). Therefore if a more vulnerable land use is required for the site, it will have to pass the Sequential Test as described here and the Exception Test (see PPS25 Flood Risk Vulnerability and Flood Zone Compatibility table in the tiles).

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9.4 Third Step – Apply the PPS25 Flood Risk Management Measures Where sites in Flood Zone 1 overlap into a higher risk flood zone, it is recommended that where possible, the following actions take place prior to the application of the Sequential Test in Flood Zones 2 and 3: a) Apply the measure of avoidance/prevention (see Section 5.6) by moving the boundaries of the potential site allocations away from Flood Zones 2, 3a and 3b, for those cases where the loss of part of the site area is acceptable. b) Within the portions inside Flood Zones 2 and 3, provisionally adopt land uses that are fully compatible with the vulnerability classification of PPS25, to try to avoid the need to apply the Exception Test. This may involve rearrangement of the site layout or substitution of different land uses as appropriate. c) The new development may be an opportunity to carry out measures to reduce flood risk by including work to control flood frequency, for example, open up culverts, provide additional storage, or facilitate habitat improvement. This will not negate the need for the Exception Test but can assist in demonstrating that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. d) Mitigation measures, such as flood resilient building design, may also be applied.

It should be noted that the data in the SFRA should be regarded as initial guidance for the Sequential Test. However, as the flood data may be based on relatively course assessment (e.g. Flow modelling or historical flooding where only approximate extents are known) then a detailed site assessment, such as a Level 2 SFRA or FRA, may indicate different flood extents.

9.5 Fourth Step – Apply the Sequential Test in Flood Zone 2 Having exhausted the options in Flood Zone 1, the fourth step is to repeat the procedures in steps 2 and 3 for sites in Flood Zone 2. If any of the sites are required for more vulnerable land uses, the Exception Test will need to be applied to determine if the need for the development outweighs the flood risk. It should be noted that where there is a need to apply the Exception Test it is beyond the scope of this ‘Level 1’ SFRA, and a ‘Level 2’ SFRA must be commissioned to further consider the actual variation of hazard posed within flood zones.

9.6 Fifth Step – Apply the Sequential Test in Flood Zone 3 The fifth step is to apply the Sequential Test in Flood Zone 3, and where required the Exception Test, based on a ‘Level 2’ SFRA, in accordance with PPS25. This

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applies to all potential sites that fall within Flood Zone 3 as well as those that encroach or are located within a 100m radius from a high risk ‘localised flooding area’ in Flood Zones 1 and 2.

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10 Guidance for the Preparation of Flood Risk Assessments

10.1 Introduction Flood Risk Assessments will be required for most proposed developments and the level of detail will depend on the degree of flood risk in the site and the nature and scale of the development (see general FRA requirements for each flood zone in PPS25 Annex D tables and Annex E. Further guidance can be found in the Practice Guide Companion to PPS25).

It is imperative that site-based Flood Risk Assessments (FRAs) should be discussed early in the planning process and submitted as an integral part of the planning application. It is now a government directive that planning applications seeking approval for development within flood affected areas can be regarded as invalid if not supported by a Flood Risk Assessment. Planning applications are approved by the Local Planning Authority and the Environment Agency acts as a statutory consultant for sites in Flood Zones 2 or 3, sites larger than one hectare in Flood Zone 1 and sites less than one hectare that are within areas which are identified as having critical drainage problems.

The following section reflects best practice on what should be addressed within a FRA:

10.2 Proposed Developments within Flood Zone 3a and 2 and/or other sources of flooding All FRAs supporting proposed development within Flood Zone 3a and 2 (as the existing Flood Zone 2 could become a high risk flood zone in the future due to the effects of climate change) and/or other sources of flooding should include the following: • An assessment of the vulnerability of the development to fluvial flooding (and tidal, but this is not applicable to Basingstoke and Deane) over the lifetime of the development (including the potential impacts of climate change), for example maximum water levels, flow paths and flood extents within the property and surrounding area. The Environment Agency may have carried out detailed flood risk mapping within the site area that could be used to underpin this assessment. Where available, this will be provided at a cost to

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the developer. Where detailed modelling is not available, hydraulic modelling by suitably qualified specialists will usually be required to determine the risk of flooding to the site. There may be exceptions in the case of some minor development where modelling is not justified. Developers should contact the LA or the Environment Agency to see if they are required to undertake detailed modelling. Further information can also be found on the Agency website at http://www.pipernetworking.com/floodrisk/. • An assessment of the vulnerability of the development to flooding from other sources (for example surface water drainage, groundwater, etc). This will involve discussion with the planning authority and the Environment Agency to confirm whether a localised risk of flooding exists at the proposed site. • Demonstration that the sequential approach has been applied on-site. • An assessment of the potential of the development to increase flood risk elsewhere through the addition of hard surfaces, the effect of the new development on surface water runoff, and the effect of the new development on depth and speed of flooding to adjacent and surrounding property. This should be considered for the lifetime of the development, including an allowance for the effects of climate change, as well as suitable provision for future likely minor development such as paving of front gardens or minor extensions. It is recommended that sustainable drainage techniques are employed to ensure no worsening to existing flooding problems elsewhere within the area. The FRA should demonstrate no increase in: • The peak rate of stormwater runoff leaving the site; • The volume of runoff leaving the site; • The pollution load to receiving waters from stormwater runoff by following the SUDS ‘management train’. An assessment of overland flows and temporary flood storage across the site will also need to be undertaken. Further guidance can be found in Chapter 11 of this SFRA. • A demonstration that residual risks of flooding (after existing and proposed flood management and mitigation measures are taken into account) are acceptable. Measures may include flood defences, flood resistant and resilient design, exceedance design, escape/evacuation, effective flood warning and emergency planning.

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• Details of existing site levels, proposed site levels and proposed ground floor levels. All levels should be stated relevant to Ordnance Datum. The survey should demonstrate safe access and egress. • Demonstration that any loss of floodplain storage can be compensated on a ‘level for level’ basis. Further information can be found in the document CIRIA C624 ‘Development and Flood Risk’ Appendix A3. • Demonstration that the development will not negatively impact upon flood water flows.

It is stressed that all forms of flooding need to be considered and not just that from fluvial sources. Localised flooding is typically associated with local catchment runoff following intense rainfall and must be considered as an integral part of the detailed Flood Risk Assessment.

It is essential that developers thoroughly review the existing and future structural integrity of formal and informal defences, if present, upon which the development will rely (over the lifetime of the development), and ensure that emergency planning measures are in place to minimise risk to life in the unlikely event of overtopping or defence failure.

10.3 Proposed Development within Flood Zones 1, 2 and 3 PPS25 requires the submission of a FRA for all sites in Flood Zone 2 and 3 and for all sites greater than 1 hectares within Flood Zone 1. Applicants are advised to refer to the requirements of Planning Policy Statement 25 and general standing advice for developer/applicant in this regard.

For all other proposed developments located in Flood Zone 1 an FRA is not normally required, however exceptions are recommended for those locations where a new development is likely to overload the capacity of the existing drainage system (in particular at those locations where the localised flooding from surface water drainage is indicated on the SFRA flood maps). These areas have been identified in this study as ‘critical drainage areas’ and are highlighted in the SFRA Flood Maps (Tiles A – F). Areas which drain into the ‘critical drainage areas’ have also been identified as part of this study as ‘upstream critical drainage areas’ and are also highlighted in the SFRA Flood Maps (Tiles A – F). In such cases, depending on the scale/type of the development, the applicant may be required to submit a FRA and/or demonstrate that flows from their proposed development can be attenuated to green field run off rate by way of the submission of additional

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information. To assist in the calculation, the council has developed an online tool which will be published separately.

In addition to flooding from the river and the sea, the FRA should consider the vulnerability to flooding from other sources. For those sites with localised flooding issues such as shallow flooding and non-frequent blockages etc, development should still be acceptable provided that adequate policies are in place for mitigating the risk. Options range from using on site water balancing and other SUDS solutions, and may include contributions from the developer for the upgrade of the surface water system, if feasible.

An assessment should be made of the potential of the development to increase flood risk elsewhere through the addition of hard surfaces, the effect of the new development on surface water runoff, and the effect of the new development on depth and speed of flooding to adjacent and surrounding property. This should be considered for the lifetime of the development, including an allowance for the effects of climate change, as well as suitable provisions for future likely minor development such as paving of front gardens or minor extensions.

It is recommended that sustainable drainage systems are employed even where localised flooding does not occur, to ensure no worsening of flood risk on site or elsewhere within the area. The FRA should demonstrate no increase in: • The peak rate of stormwater runoff leaving the site; • The volume of runoff leaving the site; • The pollution load to receiving waters from stormwater runoff by following the SUDS ‘management train’.

As assessment of overland flows and temporary flood storage across the site will also need to be undertaken. Further guidance can be found in Chapter 11 of this SFRA.

10.4 Proposed Development within Groundwater Emergence Zones Appendix D contains maps showing predicted Groundwater Emergence Zones, and these should be consulted in regard to risk of groundwater flooding. In some cases, the SFRA Flood maps may show evidence of historical events of groundwater flooding, but this may not be the case for all groundwater emergence zones. This may be due the topography of the area such as a local impermeable layer protecting the surface from the underlying chalk. However, it may simply be

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due to a lack of recording of groundwater incidents, as people can be reluctant to acknowledge this due to the effect on insurance or home value, or it may be an undeveloped area where groundwater flooding has occurred but not been noticed. Furthermore, even if groundwater flooding was prevented by an impermeable layer, the excavation work during development may breach this layer, especially if basements are included in the properties. If groundwater flooding seems likely to be an issue, then there is a need for further site specific assessment proportionate to the nature and scale of development.

10.5 Raised Floor Levels To ensure damage to property is minimised, floor levels should be raised above flood level by a specified amount known as the ‘freeboard’. The current recommended flood level is the 1% annual probability peak flood level, including an appropriate allowance for the predicted effects of climate change over the lifetime of the development (see Table 9). Wherever possible, floor levels should be situated a minimum of 300 mm above the 1% with climate change flood level, determined as an outcome of the site-based FRA. If no climate change data is available then a precautionary freeboard of 600mm above the 1% annual probability floodwater level should be used. In the case of there being no 1% annual probability floodwater level available then for minor development where it is not reasonable to undertake detailed flood modelling, a conservative assumption should be made to determine the appropriate floodwater level and a suitably conservative freeboard should also be applied.

For some situations it may not be possible to raise floor levels due to other constraints, and in some instances therefore, it may be appropriate to consider flood resilient construction. Further guidance can be found in the Practice Guide Companion to PPS25 and the Communities and Local Government document ‘Improving the flood performance of new buildings’.

It is highlighted that many of those areas currently situated within Medium Probability Flood Zone 2 could, under the impacts of climate change, become part of the High Probability Flood Zone 3. This is important as it means that properties that are today at relatively low risk are likely to be, in 20 to 100 years, within High Probability Flood Zone 3a (see precautionary assumption C2 in Section 6.4.4). It is imperative therefore that planning and development control decisions take due consideration of the potential risk of flooding in future years. For this reason development in Flood Zone 2 should apply the same approach to finished floor levels and flood resilience as mentioned above.

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10.6 Basements The construction of basements within flood affected areas (fluvial and other types of flooding) should be discouraged. Basement dwellings are highly vulnerable and should not be permitted within Flood Zone 3 and have to pass the Exception Test, based on a level 2 SFRA, within Flood Zone 2. Furthermore, in areas with shallow groundwater, structures which could impede groundwater flow (such as large basements) will need to be assessed to ensure they do not increase flood risk from groundwater elsewhere. Where basement use is permitted, it is necessary to ensure that the basement access points are situated 300 mm above the 1% probability plus climate change flood level. The basement must have unimpeded access and be of waterproof construction to avoid seepage during flooding conditions. Habitable uses of basements constitute a ‘highly vulnerable’ land use and therefore should not be permitted within Flood Zones 3a and 3b, and will be subject to the Exception Test in Flood Zone 2 (see tables in PPS25 Annex D).

10.7 Safe Access As the areas affected by flooding in Basingstoke and Deane are not generally expansive in size, the Environment Agency recommendations in regard to safe access are: • ‘Safe’ access must be dry for ‘more vulnerable’ and ‘highly vulnerable’ land uses. • Dry escape for residential dwellings should be up to the 1 in 100 year event, taking into account climate change. • ‘Safe’ access should preferably be dry for other uses such as educational establishments, hotels and ‘less vulnerable’ land use classifications.

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11 Guidance for the Application of Sustainable Drainage Systems

11.1 Introduction PPS1: Delivering Sustainable Development and PPS25 require that LPAs should promote Sustainable Drainage Systems (SUDS). LPAs should ensure policies encourage sustainable drainage practices in their Local Development Documents. Basingstoke and Deane Borough Council are producing a Design and Sustainability Supplementary Planning Document (SPD) which provides links to more detailed information on the use of SUDS and is due to be adopted in Autumn 2008.

SUDS is a term which encompasses the use of a variety of drainage elements for managing surface water in a way which is more sympathetic to the natural and human environment than conventional below-ground drainage systems. Management of surface water is an essential element for reducing flood risk and SUDS techniques are often designed to achieve this in a way that mimics the natural environment. Indeed, reducing the rate of discharge from urban sites to near-Greenfield (ideally a minimum of 5% below the pre-development) runoff rates is one of the most effective ways of reducing and managing flood risk and accords with the approach adopted by the Environment Agency. For further information on methods used for the estimation of green and impermeable/paved area runoff, and the management of rainfall runoff in developments, see DEFRA/Environment Agency R&D Technical Report W5-074/A/TR/1 Revision D ‘Preliminary rainfall runoff management for developments’.

11.2 Types of SUDS Systems SUDS may improve the sustainable management of water for a site by: • controlling or reducing peak flows to watercourses or sewers and potentially reducing the risk of flooding downstream; • reducing volumes of water flowing directly to watercourses or sewers from developed sites; • improving water quality, compared with conventional surface water sewers, by removing pollutants from diffuse pollutant sources; • reducing potable water demand through rainwater harvesting;

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• improving amenity through the provision of aesthetic elements and varied habitat within the public open space; • replicating natural drainage patterns, including the recharge of groundwater so that base flows are maintained.

To meet the requirements of PPS25 to reduce flood risk: • development should comply with the document ‘Rainfall runoff management for developments – interim national procedure’ included in Appendix E. • there needs to be a reduction in the current instantaneous runoff rates. Development on Greenfield sites will be expected to mimic the existing Greenfield drainage conditions. Development on Brownfield sites will be expected to make a positive reduction to revert the site back to Greenfield conditions unless for exceptional reasons agreed with Basingstoke and Deane Borough Council and the Environment Agency it is not possible or reasonable to achieve this. In such instances a positive reduction will still be required however the amount will need to be agreed based upon what is possible and reasonable; • there should preferably be a reduction in the volume of runoff by the use of infiltration in accordance with the Building Regulations Part H3.

If this is applied across a catchment, the cumulative effect, particularly in the future as the impacts of climate change increase, from a number of sites could be significant.

There are numerous different ways that SUDS can be incorporated into a development, and many of the devices can be applied to both new and existing developments. The appropriate application of a SUDS scheme to a specific development is heavily dependent upon the topography and geology of the site and the surrounding areas. Careful consideration of the site characteristics is necessary to ensure the future sustainability of the adopted drainage system.

The most commonly found surface elements of a SUDS system are described below:

Pervious surfaces:- Surfaces that allow infiltration of rainwater into the underlying soil or construction, such as porous surfacing (e.g. gravel), permeable hard surfacing, permeable block paving, porous tarmac and porous concrete. The

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storage can be created within the sub-base of these surfaces given careful selection of the stone fill or use of plastic box systems.

Green roofs:- Vegetated roofs that reduce the volume and rate of runoff and remove pollution. These also create habitat in urban areas and can improve air quality.

Filter drains:- Linear drains consisting of trenches filled with a permeable material, often with a perforated pipe in the base of the trench to assist drainage, to store and conduct water. They may also permit infiltration.

Filter strips:- Vegetated areas of gently sloping ground designed to drain water evenly off impermeable areas and to filter out silt and other particulates.

Swales:- Shallow vegetated channels that conduct and can retain water in larger storm events. The vegetation filters out particulate matter in the flow thus providing treatment and improving water quality. They may also permit infiltration.

Basins:- Ponds and Wetlands Areas that may be utilised for surface runoff storage.

Infiltration Devices:- Structures to promote the infiltration of surface water into the ground. They can be trenches, basins or soakaways.

Bio-retention areas:- Vegetated areas designed to collect and treat water before discharge via a piped system or infiltration to the ground.

The most commonly found sub-surface elements of a SUDS system are described below. These are particularly useful where there is limited open space on the site. Some are the only options where sections of the drainage network are to be adopted. Plastic Box Storage:- Sub-surface storage structure that has a very high void ratio (proportion of empty space to solid fill) and thus occupies a reduced space compared to other options, e.g. stone-filled trenches. Particularly useful where there is limited open space in the site. It can also be used as a very effective infiltration device due to the very large areas in contact with the ground.

Large diameter pipes, culverts or tanks:- Provide a volume of below ground storage with a high void ratio and good man entry provision to allow for future maintenance and cleaning. These would generally be suitable for adoption in most circumstances.

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Pipes and accessories:- A series of conduits and their accessories, normally laid underground, that convey surface water to a suitable location for treatment and/or disposal (these drainage elements should generally only be considered where at- surface SUDS techniques are not practicable, e.g. under a road crossing).

For more guidance on SUDS, the following documents are recommended as a starting point: • C697 The SUDS Manual, Woods Ballard B; Kellagher R et al, 2007 – available from CIRIA bookshop www.ciria.org.uk • Interim Code of Practice for Sustainable Drainage Systems, National SUDS Working Group, 2004 – available from CIRIA bookshop www.ciria.org.uk or Environment Agency website www.environment-agency.gov.uk • Preliminary rainfall runoff management for developments, DEFRA/Environment Agency R&D Technical Report W5-074/A/TR/1 Revision D, July 2007, - Free download from Environment Agency website www.environment- agency.gov.uk • C625 Model Agreements for Sustainable Water Management Systems, Shaffer et al, 2004, – available from CIRIA bookshop www.ciria.org.uk • C539 Rainwater and greywater use in buildings – best practice guide, Leggett et al, 2001, – available from CIRIA bookshop www.ciria.org.uk • C582 Source control using constructed pervious surface: hydraulic, structural and water quality performance issues, Pratt et al, 2002, – available from CIRIA bookshop www.ciria.org.uk • C635 Designing for exceedance in urban drainage – good practice, Digman et al, 2006, – available from CIRIA bookshop www.ciria.org.uk • Report 156 Infiltration drainage – manual of good practice, Betess R, 1996, – available from CIRIA bookshop www.ciria.org.uk • Harvesting rainwater for domestic uses: an information guide, Environment Agency, 2003, - Free download from Environment Agency website www.environment-agency.gov.uk • Planning Policy Statement 25 (PPS25) Development and flood risk, Department for Communities and Local Government, 2006, - Free download from CLG web site http://www.communities.com • Development and flood risk: A Practice Guide Companion to PPS25, - Department for Communities and Local Government, 2006, - Free download from CLG web site http://www.communities.com

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11.3 Effective Application of SUDS Techniques

A hierarchical approach is recommended for selection of SUDS techniques to dispose of surface runoff. This is illustrated by the SUDS Management Train (see Figure 7).

Figure 7: SUDS Management Train (from the Environment Agency website).

The first stage, ‘Prevention’ stresses the benefit of avoiding runoff in the first place, and also refers to the need to prevent pollution. Prevention of runoff can be achieved by measures such as avoiding paving a surface or using acceptable alternatives such as gravel, which allows rainfall to soak directly into the ground. It may be possible to allow roof water to discharge straight onto a lawn in order to soak into the ground. These methods must consider the surfaces the rain falls onto in order to avoid pollution of the soil and groundwater. This includes ensuring minimal use of herbicides on lawns, secure storage of oils and chemicals to avoid leakage, dog litter policies etc. Green roofs are another useful technique for reducing runoff from roofs and also offer improvement of water quality.

If prevention methods are not sufficient to avoid runoff, the next preferred option is to store and dispose of it on site. This includes measures such as permeable paving, where water is stored below the surface in the storage space provided until it can soak into the ground. Rainwater harvesting is another valuable technique, where rainfall is collected and then used as a substitute for mains water for activities such as watering lawns or flushing toilets. This has the added benefit of reducing demand on public water supply, and reduces costs for the user of the rainwater (if they purchase water using a water meter). Where water cannot be

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directly infiltrated into the ground, it may be conveyed some distance before infiltration or, alternatively discharged into a watercourse. As the runoff is conveyed further, it moves from source control to site control and then regional control.

Infiltration is preferred over disposal to a watercourse or the public sewer system as this more commonly deals with runoff nearer to source and serves to replenish groundwater. This recommendation is reinforced by the requirements of the Building Regulations Part H3. If infiltration is not viable (due to a high water table, local impermeable soils, contamination issues including source protection zones etc), then the next option of preference is for the runoff to be discharged into a nearby watercourse. Only if neither of these options is possible should the water be discharged into the public sewer system.

The protection of groundwater quality is a factor in determining how SUDS are implemented. It should be noted that where soakaways are proposed, their use will only be acceptable to the Environment Agency subject to the following conditions: • Soakaways shall not be constructed through contaminated material. • The depth of any soakaway should normally not exceed 2.0 meters and under no circumstances shall be permitted to intersect the water table. • A minimum of a 1.0 metre unsaturated zone shall be maintained between the base of any soakaway and the maximum seasonal water table for that site. • Soakaways intended to drain highway or parking areas will usually require additional safeguards such as seal-trapped gullies or a suitably sized oil/grit separator. • Soakaways designed to receive clean roof water should be kept separate from those receiving surface water runoff from highway or parking areas. • The use of borehole soakaways will only be acceptable subject to written agreement from the EA.

It is important to note that it is an offence to discharge list 1 substances (petroleum, hydrocarbons etc) to groundwater. Of greatest concern would be if a list 1 substance was to be discharged directly into groundwater. This may affect the suitability of individual SUDS designs. In particular this may restrict the use of infiltration from swales for the drainage of car parks, in some areas where groundwater is likely to occur at shallow depth.

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Large increases in impermeable areas contribute to significant increases in surface runoff volumes and peak flows and could increase flood risk unless adequate SUDS techniques are implemented. This may even apply for developments which are at low risk of flooding themselves, such as sites in Flood Zone 1 without localised flooding, since they may still increase the risk of flooding elsewhere, particularly downstream of discharge.

A critical situation could be that of building a new large development just upstream of an existing development which already suffers from frequent flooding. In this case an effective SUDS technique could be to have large areas of pervious surfaces (pervious paving etc, where natural surfaces are not possible) combined with infiltration and rainfall harvesting techniques. The use of large attenuation areas may not be the appropriate SUDS technique, as whilst these reduce peak flows they do not affect flood volumes.

SUDS techniques will be required for most, if not all, proposed land allocations. Attenuation to below existing (pre-development) discharge rates, whilst allowing for the effects of climate change, should be the norm, in particular at Brownfield sites. The method adopted will depend on the individual circumstances; often a combination of techniques will provide the best solution. Developers should consult with the Environment Agency at an early stage about their SUDS proposals, to ensure that they are adopting the most affective methods for their site.

11.4 Selection of SUDS for a new site development The main variables which affect the choice of a SUDS technique are:

a) catchment permeability;

b) source protection zones;

c) general slope of the ground and ground levels;

d) current land use (Greenfield vs Brownfield sites);

e) location of the development relative to other urban areas;

f) type of land use proposed and layout of the development;

g) presence of contaminated land;

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h) depth to permeable layer beneath a more impermeable layer;

i) normal and maximum height of groundwater table;

j) amount of rainfall expected;

k) willingness of the water company to adopt part of the drainage network.

Tiles As to Fs SUDS Maps have been produced to assist in the selection of SUDS methods for site developments. An indication of soil hydrological properties in Basingstoke and Deane Borough is illustrated as colour coded shading based on the estimate of the Standard Percentage Runoff (SPR) from the Flood Estimation Handbook. With the exception of the soil area highlighted in green (which has a SPR of 49.6%) the soil areas are in principle sufficiently permeable to allow the infiltration of surface runoff. The Groundwater Source Protection Zones are shaded within Zones 1 and 2, with all none-shaded areas being Zone 3. The background to the map is OS mapping tiles which include contour information. Therefore, from these maps information on variables a) to e) in the list above can be gained.

Figure 2: Distribution of Soil Permeability and Source Protection Zones is provided for extra clarity of the soil hydrological properties and source protection zones as it shows these in an overview of the whole borough.

Together with Tiles As to Fs, Table 14 below can be used as an initial guide for identifying possible SUDS techniques that can be applied for a site with a given combination of soil permeability and source protection category. This is meant as an initial guide only and does not remove the need for site based investigation.

SPR (%) Comments

49.6 Source Protection Zone 1

Low permeability soil, so source control SUDS (schemes which deal with rainfall at or extremely near to the point where it falls) which seek to infiltrate water into the ground will have minimal efficiency, although infiltration of small amounts of water may be possible given time. Some infiltration systems may be acceptable for ‘cleaner’ sources such as roof

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water however infiltration is not allowed from less clean sources such as lorry parks, large car parks, industrial sites, garage forecourts, and major roads etc due to the risk of contamination. SUDS such as swales and filter strips may be used for Greenfield runoff as source controls, but where large amounts of water are expected, will require connection to the public sewer system to avoid long-term flooding. Whilst porous/permeable material over filter drains may be used for pavement, due to the risk of contamination to groundwater the water must be conducted through the drain into the public sewer system.

Retention areas tend to be lower down the hierarchy than infiltration schemes as they do not deal with the water as near to the source. However, for low permeability soils they permit more time to enable infiltration, plus they can often be permanently water-filled thus increasing their amenity value. In Zone 1, this is usually only advisable for runoff from Greenfield sites. In heavy rainfall these can attenuate runoff peak flow but will provide minimal reduction of volume so connection to piped systems is advisable for overflow.

Rainwater harvesting and green roofs are beneficial in reducing runoff which can cause flash flooding, and the latter in particular will help improve the water quality of runoff by minimising pollutant wash-off from the roof.

Source Protection Zone 2

As with Zone 1, but it may be possible to discharge most runoff into a watercourse rather than the public sewer system. Water from SUDS systems has improved quality due to treatment by the SUDS system such as filtration or biodegradation, but also because of the attenuating effect on the peak flow so that runoff enters receiving waters more gradually which enhances the dilution, settlement and degradation of any remaining pollution. For runoff from paved areas, a more intensive bio-retention area may be necessary or porous/permeable pavement. A sand layer below will normally absorb the majority of pollutants. Cleaning of the pavements is usually necessary to prevent build-up of debris which would clog the surface; in the case of runoff from grassed areas, swales and filter strips are generally best to avoid clogging by soil. Runoff from more heavily contaminated surfaces such as roads or industrial sites may still require discharge into the public sewer system for full treatment. The Environment Agency do not usually require oil separators for permeable paved car parks.

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Source Protection Zone 3

SUDS which retain water long enough to encourage maximum infiltration are particularly beneficial here. Most SUDS involve some form of treatment which is likely to ensure the water quality is sufficient, particularly if several SUDS are used in series, given that Zone 3 is not near to vulnerable water sources (although it should be checked that there are no local sensitive water bodies which may be affected).

29.2 Source Protection Zone 1

An SPR of 29.2 indicates reasonably permeable soil so infiltration is usually viable, but due to being in a Zone 1 area should be restricted to ‘cleaner’ water such as Greenfield runoff (by ‘Greenfield’ it is assumed that this is not treated with pesticides or herbicides) or roof water. From other areas, the water quality may contaminate the groundwater source so due to the permeability of the soil it is advisable to only use a SUDS technique which is lined underneath to prevent infiltration, and have water conducted away to the public system.

Sites may benefit from rainwater harvesting provision as prolonged rainy seasons cause the water table to rise so that soil cannot accept later rainfall.

Source Protection Zone 2

As with Zone 1 except infiltration of non-Greenfield runoff may be possible provided the nature of the pollutants and the type of treatment that can be incorporated into the SUDS is carefully assessed. Designing retention areas to be permanently water-filled may require the pond to either be lined or receive water by artificial means if rainfall is not enough to keep it replenished. Where swales and filter strips are intended to purely infiltrate water, rather than conduct it, consideration should be given to avoid placing it somewhere where it would suffer compaction (e.g. from people walking over it) as this would reduce its permeability.

Source Protection Zone 3

Permeable soil and not near to a protected source so most infiltration techniques should be

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suitable.

25.3 Very similar soil type to row above so the same comments apply.

14.5 Comments largely apply as in the two rows above, but as this soil is more permeable the infiltration and retention schemes may not require such large areas as infiltration is more efficient.

2.0 Again the highly permeable nature of the soil may allow for smaller infiltration areas.

Table 14: Selection of SUDS techniques.

This table is intended only as an initial guide to the types of SUDS technique which may be appropriate for a given site, but other factors are also important. For example the amount of space available for the development will affect the choice of technique as some, such as swales and ponds, take up more space than others. A couple of important points to bear in mind with respect to infiltration is that the water may affect ground stability and thus pose a risk to nearby buildings, and in periods of prolonged rainfall the soil may become saturated so that the infiltration devices will cease to work. The land use in the site and surrounding area will affect the type of pollution that occurs, and different SUDS techniques are better at dealing with different types of pollution. A further factor to consider is that SUDS techniques often require maintenance in order to remain effective so it is necessary to ensure that a suitable authority agrees to take this on. In addition, the soil properties and source protection zones give only an overview of the borough, and may not be representative of the situation for a particular site at the local scale, for example it may have an atypical geology, or a local water body, not necessarily an aquifer, which requires protection.

Whilst the above chapter gives an overview of different types of SUDS, there are a wide variety of SUDS available, which use different materials, designs or combinations. SUDS methods enable a very flexible approach to drainage with benefits to managing water quantity and quality, and enhancing the environment.

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12 Summary of Principle Recommendations

This report has been produced to comply with Government legislation in PPS25 which requires planning authorities to produce a Strategic Flood Risk Assessment for use in carrying out the Sequential Test in allocating development under the Local Development Framework.

The SFRA is a ‘living’ document and therefore it is recommended that prior to each round of planning the maps be updated, at least in electronic form, with the most recent flooding data from the Environment Agency, Water Companies and the Borough Council’s own records. Currently there is no detailed flood modelling of rivers within Basingstoke and Deane but studies may be carried out in the future.

Allocation of development with respect to flood risk must take climate change into account. Rules C1 to C3 (see Section 6.4.4.) are designed in accordance with current estimations on the effect of climate change but it is recommended that these rules may need to be updated as information on the effects of climate change improves. In particular, if detailed flood modelling studies are carried out, they may include climate change scenarios.

In order to ensure a holistic approach to flood risk management and water resource issues in general it is recommended that integrated working is encouraged with other relevant stakeholders, such as the Environment Agency and Water Companies, and that planning also takes into account guidance from other studies, such as the CFMPs, the Groundwater Flooding Scoping Studies, and the Water Cycle Strategy.

The principles of the Sequential Test are to locate development in the areas of lowest flood risk, thus allocating following the order of preference of Flood Zone 1, then Flood Zone 2, then Flood Zone 3a and finally Flood Zone 3b as a last resort. The vulnerability of the development must also be taken into account to ensure it is compatible with the Flood Zone.

Where development allocations are planned in an area of flood risk, and the vulnerability of the development requires an Exception Test, it is recommended

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that a Level 2 SFRA is carried out as the information necessary for an Exception Test is beyond the scope of this Level 1 SFRA.

A Level 2 SFRA does not negate the need for a FRA and, due to the extensive critical surface water drainage issues within the borough, it is recommended that the PPS25 guidance on requiring an FRA for all developments of 1 hectare or more (within Flood Zones 2 and 3) be extended to include certain developments within an area highlighted as having critical drainage issues. As referred to in paragraph 10.3, depending on the scale of the development, the applicant may be required to demonstrate that flows from their proposed development can be attenuated to green field run off rate by way of the submission of additional information. Further information will be published separately to clarify what scale of development within a critical drainage area would trigger a requirement for a FRA to manage surface water run off and to clarify what scale of development would trigger a requirement to attenuate surface water run off to green field rates within a critical drainage area. An on line tool will be published separately to assist developers .

This approach is recommended to gain a more complete understanding of surface water and drainage related flooding for the Town of Basingstoke, so that any future improvements are part of a wider strategy for addressing these sources of flooding. A Surface Water Management Plan (SWMP) or Integrated Urban Drainage Plan (IUDP) could define the future approach. This is important because of both the existing and future risk.

As much of the Borough of Basingstoke and Deane is underlain by chalk aquifer, which is particularly susceptible to groundwater flooding, it is recommended that Level 2 SFRAs and FRAs should pay particular attention to the risk of groundwater flooding by assessing historical records and also potential occurrence, even where historical incidents have not been recorded, by taking into account the local geology and information from sources such as the groundwater emergence maps (see Section 10.4).

Measures to control and mitigate flood risk should be applied, for example ensuring safe access, design of buildings to include freeboards above the flood level, and use of sustainable drainage systems. Development should aim to reduce flood risk where possible, or at least not increase it within the site or surrounding area.

Strategic Flood Risk Assessment Page 71

Sustaining & Improving the Quality of People’s Lives

It is recommended that sustainable drainage techniques are applied following the principles of the SUDS management train. SUDS should seek to mimic natural systems and it is recommended that they be designed to control runoff as outlined in the Environment Agency document 'Rainfall Runoff Management for Developments - Interim National Procedure' (see Section 11.2 and Appendix E).

Strategic Flood Risk Assessment Page 72

Appendix A

Appendix A Details of the Environment Agency Flood Zone

A.1 Introduction A more detailed understanding of the Environment Agency Flood Zones and their limitations is important, as these are often used (unless more accurate flood outlines are available) for the production of SFRA flood maps and form the basis for appraising flood risk at a development site level.

Historically the Environment Agency and its predecessors have kept formal maps of tidal and fluvial flooding to the standards required by legislation. Originally this mapping simply recorded flood events, but in 2001 PPG25 (the predecessor of PPS25 – see Appendix A) imposed a duty on the Environment Agency to produce maps showing the predicted extent of tidal and fluvial flood zones for all Main Rivers in England and Wales (Main Rivers are large or locally significant watercourses as designated by DEFRA or the Welsh Assembly Government). These flood zones are published on the Environment Agency website at www.environment-agency.gov.uk, and are updated on a quarterly basis as improved modelling and recent events provide data for refining the flood extents.

A.2 Comparison of Environment Agency and PPS25 Flood Zones The Environment Agency flood zones show the estimated extent of flooding corresponding to PPS25 Flood Zone 2 and Flood Zone 3, where Flood Zone 3 is the combined Flood Zone 3a and 3b area (the division of Zone 3 into 3a and 3b was introduced in PPS25). Therefore, for the Environment Agency flood zones:

Flood Zone 2 comprises land assessed as having between a 1% (1 in 100) and 0.1% (1 in 1000) annual probability of river flooding or between a 0.5% (1 in 200) and 0.1% (1 in 1000) annual probability of sea flooding in any year. Flood Zone 3 comprises land assessed as having a 1% (1 in 100) or greater annual probability of river flooding or a 0.5% (1 in 200) or greater annual probability of flooding from the sea in any year. Land outside Flood Zone 2 corresponds to Flood Zone 1 and comprises land assessed as having a less than 0.1% (1 in 1000) annual probability of river or sea flooding in any year.

The flood zones produced by the Environment Agency are based on current environmental conditions, so do not make any allowance for climate change.

Both the Environment Agency and PPS25 flood zones assume that there are no flood defences (formal or informal, see Glossary of Terms) as there remains a risk that these defences can fail through overtopping or structural failure.

A.3 Production of the Environment Agency Flood Zones A.3.1 Environment Agency Tidal Maps Mapped tidal Flood Zones 3 and 2 generally comprise land that is lower than the estimated height of the extreme surge tide in the relevant event. Where detailed studies have been undertaken, tidal Flood Zones 3 and 2 have been modified to take into account wave height, the gradient of the land and the relatively short duration of the high tide. In appropriate circumstances, the build up of tidal water trapped behind tidal defences over several high tides is mapped.

A.3.2 Environment Agency Fluvial Maps Data for fluvial Flood Zones 2 and 3 is derived from a number of sources. Most fluvial flood outlines are derived from the “JFlow” generalised computer modelling, which is a ‘coarse’ modelling approach. Caution must be exercised in interpreting JFlow derived flood outlines due to the large number of assumptions incorporated into the JFlow model. For instance, at some locations the river centreline incorporated into the model was found to be erroneous with the result that the associated floodplains deviate from the natural valleys.

A.3.3 Updates of the Environment Agency Flood Maps from Modelling In many places the results of flood mapping studies have superseded the JFlow model. Generally these studies included high quality hydrological research, surveyed river cross sections, and more precise digital modelling Output from a 2D TuFlow model such as ISIS, TuFlow and HecRas.

A cautionary point however, is that fluvial flooding is dependent on the standard of maintenance of watercourses and structures, and the degree of maintenance allowed for tends to vary from model to model, with the Output from a 1D ISIS model result that flood maps based on modelling do not offer a consistent approach in this respect. As a further consequence, serious blockages occurring during a flood might produce much more flooding than shown on previous modelling for a similar hydrological event.

A.3.4 Updates of the Environment Agency Flood Maps from Historic Events Flood Zone 2, although not Flood Zone 3, may also be updated based upon historic events, for instance the extent of the severe 1947 floods as recorded by the Environment Agency’s predecessors. The extents of recent events are often determined from aerial photographs. Although the annual probability of the historic event is not usually determined, the historic outline is used to update Flood Zone 2 if the historic extent is larger in order to maintain a precautionary approach.

When flood extents are based on historical data, there is often uncertainty about a) whether the flooding has emanated from the river or is the result of other land drainage, b) the precise flood return period and c) whether the flooding was the result of blockage or some other maintenance factor. Occasionally therefore, flood zone modifications based on observed flooding are unreliable.

A.3.5 Other Forms of Flooding in the Environment Agency Flood Maps Although PPG25 and PPS25 advise that the flood zone maps, which are primarily intended as a planning tool rather than a definitive record, should only show tidal and fluvial flooding, in practice they may show other sources of flooding. The historical flood events used for parts of Flood Zone 2 are all either main river flooding or flooding which has been influenced by main river; this latter category may therefore include other types of flooding, which may exacerbate the extent of flooding. In Hampshire for instance, much flooding derived from groundwater sources is included, both in dry valleys and isolated ponds. These groundwater flooding outlines are derived from both JFlow and observations. A.3.6 Non Main River flooding in the Environment Agency Flood Maps “Main rivers” are principal watercourses defined by Section 93 of the Water Resources Act, 1991 and shown on a formal map held by the Environment Agency. The Environment Agency is responsible for producing flood zones for these rivers. In some cases, the flood zones may also include flooding where the source is not main river but has been affected by main river, for example a small drainage channel backing up from the main river.

There is no precise definition of how much non main river flooding is included. If no floodplain is shown for a catchment that is less than 3 square kilometres in area, it should be presumed that the area has not been modelled and/or it has not been recorded (as opposed to assuming that flooding has not occurred or would not occur).

A.4 Flood Defences The flood zones are created based on the “undefended situation”, as a precautionary approach, as there remains a risk that defences can fail through overtopping or structural failure. The Environment Agency flood maps (which can be viewed on their website at www.environment-agency.gov.uk) show all formal flood defences, and indicate “areas benefiting from defences” (ABDs) in a 1 in 100 year (1% annual probability) fluvial flood event or 1 in 200 year (0.5% annual probability) tidal flood event where detailed modelling studies have been carried out or where the standard of protection offered from the defences is known to be more than 1 in 100 year or 1 in 200 year, respectively. ABDs are land where flooding is prevented by defences, although it is assumed that the defences are robust, leak free and maintained, which is not always the case.

A.5 Climate Change Effect on Flood Zones In the absence of better information, the current fluvial Flood Zone 2 can be considered an estimate of the extent of fluvial Flood Zone 3 within 100 years. This principle does not hold for tidal floods, however, as the level of difference between a 1 in 200 year and a 1 in 1000 year return period tide is only about 200 mm, whereas the forecast increase in tide levels over the next 100 years is in excess of 1m.

The Environment Agency flood maps available on their website show only the present day situation. However, where detailed modelling has been carried out, climate change scenarios are usually addressed and these results can be obtained from the Environment Agency in GIS format.

Appendix B

Appendix B: Audit Trail Database

Ref. No Subject & Type of data Medium Date Source Summary Description Used for 1 in 10,000 and 1 in 25,000 OS Hampshire County Hampshire County Production of Figures in reports and planning tool. HSFR/003 maps and layers for Hampshire Dec 2006 GIS files showing geographical features related to Hampshire. Council (CD) Council Superceded Boundary and Districts GIS data - Flood events database, flood zones, historical flood maps, main rivers layer (1 in 10,000). Folders of GIS files, reports and Environment Production of some of the Flood Zones 3a, 3b, 2 and Environment Pdf and Word documents - Flood Reports 00-01 and 02-03. HSFR/007 databases, with copies of 20 Dec 06 Agency Winchester 3+CC - superceded. Flood risk from reservoirs to Agency (CD) Spreadsheets - Environment Agency catalogues of reports, CDs accompanying emails. Office describe in report and Microfiche in the Area Office, and database of Reservoirs under Act. Southern Water Flood Risk Southern Water Records of flooding in the last 10 years for events more frequent HSFR/011 Points with X, Y and Postcode 7 Feb 07 Southern water Show sewage flooding (email) than 20 years (spreadsheets) Thames Water Spreadsheet listing surface water, foul and combined flooding, HSFR/012 Thames Water Spreadsheet 7 Mar 07 Thames Water Show sewage flooding (email) classified by postcode. Environment Hampshire Groundwater Production of some of the Flood Zones 3a, 3b, 2 and HSFR/016 Agency via Feb 07 Halcrow, BP Library GIS files for all flooded villages (used for preparing the reports). Flooding 00-01 layers. 3+CC (where applicable) Halcrow (CD) Environment SFRA questions & Answers. Text Environment Environment Agency Guidelines with questions & answers. It HSFR/018 Agency (memory Oct 06 To ensure compliance with Guidelines file. Agency also includes comments from James about Climate change, etc. stick) Environment Thames CFMP_Summary doc Environment EA document outlining the catchment management plans for HSFR/025 15 Feb 07 Agency Frimley Writing the policy elements of the report. version 8 25Jan07.pdf Agency (CD) the Thames region. Office Environment Environment HSFR/035 2000-01 flood event photos 20 Dec 06 Agency Winchester Jpg photos of flooding in Hampshire during 2000/2001. Photos on cover. Agency (CD) Office Environment Environment Jpg photos of flooding in Hampshire during November 2005, HSFR/037 2005 flood event photos 20 Dec 06 Agency Winchester Photos on cover. Agency (CD) plus some accompanying documents. Office Shapefiles of floodzones 2 and 3 (Mar 07), modelled/historical Environment flooding in Tadburn Lake, Wallington River and River Avon, Updating SFRA flood maps – MapInfo files of EA updated floodmaps and Environment HSFR/040 29 June 07 Agency Winchester and accompanying pdf documents. floodzones 2 and 3 were created and replaced the files documents Agency (CD) Office NB; missing flood areas (River Avon, rivers in Rushmoor, Hart, used in all tiles. Floodzones now superceded. East Hampshire, Basingstoke and Deane) Environment Shapefiles of floodzones 2 and 3 for south-east part of Thames Updating SFRA flood maps – MapInfo files of EA updated floodmaps and Environment HSFR/041 11 July 07 Agency Thames region. floodzones 2 and 3 were created and replaced the files documents Agency (CD) Region NB; missing river in Basingstoke and Deane borough. used in all tiles. Floodzones now superceded. Environment Updating SFRA flood maps – MapInfo files of EA updated floodmaps and Environment Shapefiles of floodzones 2 and 3 for eastern side of South West HSFR/042 11 July 07 Agency Blandford floodzones 2 and 3 were created and replaced the files documents Agency (CD) region (i.e. especially River Avon) Office used in all tiles. Floodzones now superceded. DEFRA-EA Prelim Rainfall Defra/EA technical report regarding control and treatment of HSFR/045 Runoff Management For DEFRA website 6 Sept 07 DEFRA Information on SUDS stormwater runoff. Developments RevC.pdf MapInfo files relating to Basingstoke and Deane or whole GIS Mapinfo files for Basingstoke Water Cycle Study country. HSFR/046 11 Sept 07 Halcrow, BP Library Updating SFRA flood maps and Deane via Halcrow (CD) NB: Artificialgeo, Bedrock, d4_allocations_imf, district_centres_imf, linear_features, linear_features2, major_development_area_2005, Ref. No Subject & Type of data Medium Date Source Summary Description Used for mass_movement, plan_area_boundary_ims, potential2, potential3, superficial, urban_areas could not be opened. Loddon LiDAR data and Environment Environment 3 DVDs containing Loddon LiDAR data (d-ascii, m-ascii and v- HSFR/047 Basingstoke and Deane SFRA Agency (3 DVDs 12 Sept 07 Agency Frimley ascii on separate disks), and 1 CD Updating SFRA flood maps data and 1 CD) Office containing GIS data re flood maps and defences. GIS files of B&D borough-wide (assumed): areas_benefit (tab file is empty), Basingstoke and centrelines, defences (tab file is empty), floodzone_2, EA December 2007 Flood Map Environment HSFR/052 Deane Borough 18 Feb 08 floodzone_3, fsa (tab file is empty), historc flood map, Updating SFRA flood maps and Historic Flood Map Agency Council (CD) UK wide: county boundaries, EA boundaries, LPAS boundaries, national park boundaries, tif map tiles. License HSFR/053 Dorset etc SFRA SUDS final.doc Halcrow (email) 19 Feb 08 Halcrow Chapter on SUDS for Dorset SFRA Reference for SUDS chapter in report. Environment HSFR/054 SUDS A Practical Guide.doc Halcrow (email) 20 Feb 08 A guide for implementing SUDS in the Thames Region. Reference for SUDS chapter in report Agency Shape files of Hampshire fz2 (in 2 parts; north and south) and Updated EA floodzones 2 and 3 Environment Environment HSFR/055 20 Feb 08 fz3. Data licences for Hampshire County, East Hampshire Updating SFRA flood maps (December 2007) Agency (email) Agency District, Rushmoor Borough. Word document outlining the flood risk policy for the River Environment Environment HSFR/058 Kennet.doc 17 Mar 08 Kennet. (–HM confirmed that the Thames CFMP content won’t CFMP chapter of Basingstoke and Deane report Agency (email) Agency change now) Environment Environment Chapters 4 to 7 of Draft CFMP, including the policy documents HSFR/059 Test and Itchen Draft CFMP 25 Mar 08 CFMP chapter of Basingstoke and Deane report Agency (website) Agency relating to the upper Rivers Test and Itchen.

Appendix C

Basingstoke Policy Unit

The Basingstoke policy unit is characterised by a developed floodplain with typically concrete river channels. Our flood risk management approach for this type of catchment is outlined below.

Developed floodplain with little open space and often with concrete river channels

• Options to reduce the probability of flooding are highly constrained in these catchments. There is significant flood risk from a variety of sources and the rivers have been significantly altered.

• We need to change the character of the urban footprint through re-development so that the consequences of flooding are reduced by better layout and a greater resilience to flooding.

• In most areas we need to change the character of the urban area through re-development before we can introduce measures to reduce the probability of flooding that will be sustainable. For example, recreating river corridors so that there is space for the river to flow and flood more naturally.

This approach will deliver our policy for Basingstoke; Continue with existing or alternative actions to manage flood risk at the current level.

Basingstoke – what we want to achieve

¾ No further development of Greenfield sites within the floodplain. Appropriate application of the sequential test under PPS25 should safeguard existing floodplain. ¾ Surface water arising from Greenfield sites outside of the floodplain should, as far as is practicable, be managed in a manner to mimic surface water flows before the proposed development. Where the redevelopment of Brownfield sites can reduce the risk of flooding to known locations, seek to reduce run-off to better represent greenfield conditions. ¾ Multiple benefits are realised from the redevelopment of sites in the river corridor. For instance, layouts to include set back from the river so that ultimately river corridors can be re-established and buildings are resilient to flooding. In Basingstoke this may offer an opportunity to reduce the length of culvert, recognising the need to be able to accommodate periods of low flow in the River Loddon. ¾ To gain a more complete understanding of surface water and drainage related flooding so that any future improvements are part of a wider strategy for addressing these sources of flooding. A Surface Water Management Plan (SWMP) or Integrated Urban Drainage Plan (IUDP) could define the future approach. This is important in this policy unit because of both the existing and future risk. ¾ Continue to reduce the impact of low order flooding in urban areas (up to a 10% to 20% AEP flood – 1in 10 to 1 in 5 year return period) by maintaining conveyance where it both effective and sustainable to do so.

SEA, Key Approaches and Regional Priority

Summary of the Preferred Approach Policy Unit Basingstoke 0.3% of the economic consequences of fluvial flooding in Thames region

0.2% of the social consequences of fluvial flooding in Thames region

0.1% of the floodplain, channel and designated environmental assets in Thames region

• 820 properties at risk from a 1% AEP flood • 1080 properties at risk from a 0.1% AEP flood • Low levels of social deprivation • There is no floodplain BAP habitat in Aylesbury Problem / Risk • 6km of channel • Approximately 0.5km of highly modified channel

Flooding in Basingstoke can result from the overtopping of riverbanks and the channel; the overflow of surface drains; the inundation of sewers, and rapid runoff arising from urban expansion. At the source of the Loddon the watercourse is ephemeral and fed mainly by groundwater and so groundwater flooding can also be an issue. However, there are drains in place for the purposes of draining away groundwater. Blockages and constrictions in and around the channel can also influence the scale and location of flooding. Often these types of flooding happen together, which can make it difficult to determine the cause.

Policy P4 Maintain flood risk at current levels. • Approx £20pa on maintaining channel conveyance to reduce the impact of high frequency, low order events (up to 5% AEP). Existing • Maintenance costs per property at risk in Basingstoke are low compared Approaches and Impacts with Thames region as a whole. • Very few properties have signed-up to the Direct Flood Warning service. • Application of PPS25 In Basingstoke there is very large housing growth planned with the potential to increase the number of properties at risk and increase flood risk locally. There is also redevelopment happening along the river corridor through the town and in areas subject to, and contributing to, surface water flooding. The policy is aimed at achieving the right level of intervention to prevent inappropriate new development (with a focus on location). Secondly, to (a) Justification reduce risk, (b) reduce future asset replacement costs, (c) naturalise the (Balancing watercourse where practicable and (d) reduce surface water run-off through Objectives) redevelopment with a focus on the layout and design of this redevelopment. With this focus, P4 his is achievable and realistic within current resources.

Providing the new development in and around Basingstoke takes account of flood risk as defined in PPS25 there will not be a change in any of the indicators that would impact at a regional scale. A small increase in environmental assets is likely. Redevelopment of the river corridor through Basingstoke to;

Policy unit-wide • Reduce the consequences of flooding Opportunities & Constraints • Opening up culverts where possible and river restoration • Making the river a feature of the town • Reducing long-term maintenance costs Within the policy appraisal tables, P1 assumes regular blocking of culverts through Basingstoke and that 5% of the planned housing growth for Basingstoke occurs in the floodplain (a small % figure, recognising the small floodplain extent in this policy unit). This scenario increases AAD from £200k to £2,800k. A potential reduction in the length of natural channel has been shown for P1 and P2. This is because reduced input to the planning process is likely to result in more inappropriate development in the floodplain. Some development is likely within the river corridor requiring more artificial bank protection being required.

For P3, damages, properties and people at risk reflect the impacts of climate change in this policy unit. The impacts of climate change under this policy will be greater if there is new development in floodplains. Parts of Basingstoke are particularly susceptible to surface water flooding and it is possible that the impacts of climate change may be greater than modelling suggests.

Under P4 widespread strategic application of PPS25 can reduce the consequences of climate change in the long-term because of the level of development and redevelopment in this policy unit. To sustain risk at present day levels against a background of climate change will require more effective management of urban run-off in Basingstoke. Assessment of proposed P5 - More widespread adoption of flood resilience and / or land swapping approach would be required to reduce flood risk below the current baseline in the long- (Against Economic, Social term. and Environmental P6 is not applicable in this policy unit Indicators)

The risk in this policy unit could either decrease or increase – depending how successful we are in implementing policy. Greenfield development in and around Basingstoke could increase the economic and social consequences of flooding (by bringing more people and property into the floodplain and increasing run-off). Redevelopment through the town could have positive or negative impacts on flood risk. To manage the social and economic consequences, approaches that are most effective at reducing the impacts of flooding through spatial planning (application of the Sequential test, a focus on the location, layout and design of the redevelopment along the river corridor through Basingstoke) and maintaining the existing defences are most effective.

Gains against social and economic indicators under the proposed approach rely on redevelopment through the town centre being resilient and having a different site layout. To achieve this will require extra intervention (under P4), but it is unlikely that a very large increase in intervention (as under a P5 policy) will lead to further gains providing the SFRA process is working well, LDF policies take full account of flood risk and the policies are being implemented. A further potential benefit of P4 under the proposed approach is that if implemented it will reduce the long-term legacy cost of maintenance and capital replacement. Dependent upon;

Risks, • reaching agreement at a strategic level on the vision for the Uncertainties & redevelopment of the river corridor Dependencies • the appropriate location of new development

Regional Medium. There are opportunities to reduce the consequences of flooding Priority (0-5yrs) through the on-going cycle of redevelopment. However in a regional context the current flood risk is small. Regional Priority (5 yrs+) Policy key and Selected Policy policy Sustainable Policy (not selected because of constraints) approaches Most likely short-term outcome (where this differs from the selected policy) P1 Do Nothing P2 Flood Warning Emergency maintenance to remove blockages P3 P2 + Maintain conveyance in urban locations PPS25 Sequential test resulting in no greenfield development in floodplains and greenfield rates of run-off being achieved in new development P4 P3 + Strategic application of PPS25 to achieve optimal layout and design of redevelopment in the river corridors through Basingstoke Urban Drainage Planning Incorperating SuDs as part of redevelopment P5 P4 + Removal of restrictions to flow Widespread adoption of resilience approaches P6 Redevelopment that includes naturalising the river channel has the potential to reduce future capital replacement costs for some of the existing structures Resource and artificial sections of channel. Implications

Generally resource neutral in the short-term. Key Actions Effective LDF policy and SFRA for Basingstoke (Developed in Redevelopment commensurate with current and future flood risk Action Plan) Asset maintenance

Policy Unit Commentary

The Basingstoke policy unit is located in the Upper Loddon. We have determined that towards the headwaters of this flood risk area, there are no opportunities for strategic-scale flood risk intervention. Flooding in Basingstoke can result from the overtopping of riverbanks and the channel; the overflow of surface drains; the inundation of sewers, and rapid runoff arising from urban expansion. At the source of the Loddon the watercourse is ephemeral and fed mainly by groundwater and so groundwater flooding can also be an issue. However, there are drains in place for the purposes of draining away groundwater. Blockages and constrictions in and around the channel can also influence the scale and location of flooding. Often these types of flooding happen together, which can make it difficult to determine the cause.

Large areas to the north of Basingstoke have been identified to accommodate additional housing growth and are currently under development. Much of this development is on Greenfield sites, so surface water will be managed to greenfield rates of run-off. Providing, the sequential test is appropriately applied and surface water run-off is managed, these developments should not increase flood risk in Basingstoke. Some of the current development is also on Brownfield land; for example Park Prewett hospital. Redevelopment of these sites offers an opportunity to reduce flood risk. When redevelopment occurs close to areas that are prone to surface water flooding from urban run-off, achieving a net reduction in run-off through the redevelopment should be considered.

We currently manage the risk of fluvial flooding by transferring the water through the town. In places there is natural channel, but the majority of the watercourses here are culverted or have concrete channels with development right up the waters edge. The River Loddon is not a feature of the town. Works are currently being discussed for major improvements to the Loddon including potential of opening up of culverts. The works would be between the Loddon source, North of Morse Road to the shopping centre. From a flood risk management perspective this will have a positive effect as this will reduce the risk of blockages and reduce long-term maintenance costs. However, low flows occur regularly in dry conditions and it may be that river restoration will be needed in association with the opening up of culverts. Our aim should be to open up and naturalise the river wherever possible, as redevelopment opportunities arise. We need to recognise that this will be a long-term approach, driven by competing needs in the urban area, or an interim measure during the transition to a more open river channel. Establishing policies within the Local Development Framework and working in partnership with the Local Planning Authority is an important step in achieving a more sustainable approach to flood risk management and it will take time.

Basingstoke - Policy Delivery

What we want to achieve Initial Action and Mechanism Progress Partners Timescale Establish and agree with the Local Planning Authority a vision for the Planning No further development of Greenfield enhancement of the channel through Basingstoke, linked to Authority, sites within the floodplain. Appropriate redevelopment opportunities within the town as they arise Establish Environment application of the sequential test under this vision through policy, revisions to the SFRA and LDF policies. PPS25 should safeguard existing Agency floodplain. In this instance the SFRA, LDF policies need to focus on:

Surface water arising from Greenfield • Applying the sequential test so that the large-scale new sites outside of the floodplain should, development in and around Basingstoke takes full account of as far as is practicable, be managed in current and future flood risks. a manner to mimic surface water flows • Managing surface water run-off from new development. before the proposed development. Where the redevelopment of • Clarify and promote an EA vision for the redevelopment of the river Brownfield sites can reduce the risk of channel through Basingstoke to inform planners, developers and flooding to known locations, seek to riparian owners. This is likely to focus upon the layout of reduce run-off to better represent redeveloped sites and design of new buildings. greenfield conditions.

Multiple benefits are realised from the redevelopment of sites in the river corridor. For instance, layouts to include set back from the river so that ultimately river corridors can be re- established and buildings are resilient to flooding. In Basingstoke this may offer an opportunity to reduce the length of culvert, recognising the need to be able to accommodate periods of low flow in the River Loddon.

What we want to achieve Initial Action and Mechanism Progress Partners Timescale Continue to reduce the impact of low For now, conveyance will be maintained by keeping the existing Planning order flooding in urban areas (up to a channels clear and free from obstruction (using System Asset Authority, 10% to 20% AEP flood – 1in 10 to 1 in Management Plans and Performance Specifications). In the longer- Environment 5 year return period) by maintaining term, we will be seeking to maintain conveyance within a more conveyance where it both effective and Agency sustainable to do so. sustainable river system (both as a river that requires maintenance and as an asset for wider community benefit). This could include;

- To naturalise the river where practical by removing culverts, trash screens, artificial channel and bank lining where possible. - To align this objective to regeneration and redevelopment plans - To reduce the legacy costs from the replacement of assets

This objective will be closely linked to redevelopment as opportunities arise and the two responses will need to be integrated in planning for the future.

To gain a more complete Our understanding of the flood risk shows that a significant proportion understanding of surface water and is attributed to urban drainage. Investigations could include; drainage related flooding so that any future improvements are part of a wider strategy for addressing these • Investigate those areas most prone to surface water flooding. sources of flooding. A Surface Water • Assessment of the impact of allowable discharge rates from new Management Plan (SWMP) or development in Basingstoke. This could mean zoning catchments Integrated Urban Drainage Plan so that the control of surface water is targeted to best reduce flood (IUDP) could define the future risk considering the sites position and the response of that section approach. This is important in this of river to rainfall. This could lead to much better surface water policy unit because of both the existing control justifying stronger SuDS policies and the targeted use of and future risk. attenuation and long term storage to both improve the current river regime and minimise flood risk. • Identify those parts of the catchment where it would be most effective to reduce runoff from brownfield sites to better represent the greenfield conditions

For the most part there is no quick fix for existing problems. This is because drainage systems and their discharge into modified fluvial systems have tended to evolve in a piecemeal way. These problems are now recognised and in the longer-term the situation can be improved.

Figure 6.3.12a Flood management assets in the Basingstoke policy unit

Figure 6.3.12b Proposed development sites in Basingstoke Kennet Policy Unit

The Kennet policy unit is characterised by natural floodplain, with some urban centres. Our flood risk management approach for this type of catchment is outlined below:

Undeveloped natural floodplain

• The floodplain is our most important asset in managing flood risk.

• Maintaining (and in some places enhancing) the capacity of the natural floodplain to retain water, combined with maintaining conveyance of watercourses in urban areas reduces the risk of flooding and has benefits for the natural environment.

• We want to safeguard the natural floodplain from inappropriate development.

• Managing the consequences of flooding will become increasingly important, particularly by buildings and communities becoming more resilient to flooding and those who are at risk taking effective action at times of flooding.

This approach will deliver our policy for the Kennet: Take action to increase the frequency of flooding to deliver benefits locally or elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation)

Kennet - What we want to achieve

¾ Maintain the capacity and function of the undeveloped natural floodplain to retain water so that it can continue to reduce the impact of low order flood events to people and property.

¾ Seek to enhance the capacity of the undeveloped natural floodplain. Recognising that this will require structural measures, this is more likely to be achievable upstream of sizeable communities at risk from flooding where the social, economic benefits are more clear-cut.

¾ Safeguard the existing undeveloped natural floodplain through the appropriate application of the sequential test within PPS25. There are development pressures to develop Greenfield sites in the floodplain close to existing urban centres (for example in the Theale / Reading area) that need to be resisted.

¾ Align the objective of maintaining or enhancing floodplain capacity with expansion and enhancement of floodplain environments, particularly BAP habitat.

¾ Continue to reduce the impact of low order flooding in urban areas (up to a 10% to 20% AEP flood – 1in 10 to 1 in 5 year return period) by maintaining conveyance where it both effective and sustainable to do so.

¾ Reduce the consequences of flooding through continued action to raise public awareness of flooding, tailoring the advice and approach (e.g. community based) to ensure those ‘at risk’ take appropriate action to respond to flooding.

¾ Maintain, or in some cases re-establish, river corridors so that urban areas can better accommodate flooding (location and layout) and the buildings are more resilient to flooding (design). In the long-term this should be achievable through re-development. It must be recognised that this is a long-term objective (e.g. Newbury).

¾ In Newbury define options to improve conveyance (for example by removing restrictions to flow) to complement wider catchment approaches to maintain or enhance the capacity of the natural floodplain and the objective of re-establishing a river corridor that can better accommodate flooding.

SEA, Key Approaches and Regional Priority

Summary of the Preferred Approach Policy Unit Kennet

The Kennet policy unit is predominantly a chalk catchment. The flood hydrographs are strongly influenced by groundwater; they have relatively low peak flows and are of long duration.

2.0% of the economic consequences of fluvial flooding in Thames region

0.9% of the social consequences of fluvial flooding in Thames region

15% of the floodplain, channel and designated environmental assets in Thames region

• 3340 properties at risk from a 1% AEP flood event

Problem / Risk • 3970 properties at risk from a 0.1% AEP flood event • Low levels of social deprivation • Approximately 7km2 of floodplain BAP habitat (predominantly floodplain grazing marsh with areas of fen, wet woodland and reedbed). • 60km2 of floodplain (91% undeveloped and 9% urban) • 330km of natural channel • 7km of maintained or modified channel.

Within the Kennet catchment are two water-dependent internationally designated sites; Kennet and Lambourne floodplain and Kennet Valley Alderwoods.

People and property at risk of flooding is widely dispersed, with some clusters of property at risk mainly in Newbury, Theale, Marlborough and Hungerford.

Policy P6: Take action to increase the frequency of flooding to deliver benefits locally or elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation). • Approx £340k pa on maintaining channel conveyance to reduce the impact of high frequency, low order events (up to 10% AEP). Between 100 and 200 properties in the Kennet policy unit are at risk from a 20% AEP flood event and between 200 and 400 properties at risk from a 5% Existing AEP flood. Approaches and Impacts • Flood Warning. Approximately 20% of properties at risk are signed up to the Direct Flood Warning service. The majority of properties at risk are in locations where it is possible to provide an adequate flood warning for fluvial flooding. • Application of PPS25 Based on the current drivers for flood risk management, there is unlikely to be a step change in any of the indicators in the near future. Within the Kennet, the biggest potential is to increase the environmental assets of the region. This could be achieved at different locations and scales within the policy unit with small, but positive, impacts on both economic and social indicators under a P6 policy. Justification (Balancing FRM priorities will mean that there are limits in how far we can implement this Objectives) policy in the next 5 years. The approaches described under P4 are the ones most likely to be taken forward in the next five years. The approaches described in both P4 and P5 are complimentary to P6. P4 approaches will be implemented in the short-term, P5 approaches may be implemented in the medium-term (subject to the criteria for future investment) and P6 in the long- term.

Maintaining or enhancing floodplain capacity to store water to provide direct environmental benefit and small, localised economic and social benefits.

Expansion and enhancement of existing floodplain BAP habitat.

Policy unit-wide Very long-term reduction in the consequences of flooding. Opportunities & Constraints There are possible opportunities to reduce the flood risk to parts of Newbury by improving conveyance and local protection. Local defences should not be progressed where areas are likely to be redeveloped in the foreseeable future as this may preclude longer-term, more sustainable options to manage the risk through redevelopment (for example through resilience) and conflict with the objective of re-establishing river corridors. Within the policy appraisal tables, P1 assumes 500 properties flood annually and 5,000 properties are built in the floodplain upstream of Reading. This increases AAD from a baseline of £4,000k to just over £19,000k. Under this policy option (and under P2) a decrease in the length of natural channel and the area of BAP habitat is indicated. This is because with further development in the floodplain it is likely that there would eventually be a requirement for Assessment of unsustainable interventions to manage watercourses where this occurs. proposed approach Within the Kennet catchment are two water-dependent internationally (Against Economic, Social designated sites; Kennet and Lambourne floodplain and Kennet Valley and Alderwoods. Kennet and Lambourn Floodplain SAC consists of four SSSIs Environmental including Thatcham Reedbeds, which is one of the largest inland reedbeds in Indicators) southern England, containing 3.3% of this type of habitat. The SAC is one of the best areas in the UK for Desmoulin’s whorl snail (a British Red Data Book species). The flora of the River Kennet is species-rich and diverse, it has the highest average number of species per site surveyed of any other lowland river in Britain. The principal water level objectives are to maintain the perennial flow of the Kennet with natural flow variations. For the Chiltern Foliat SSSI, an increase in the length of flooding on the water meadows is desired.

Kennet Valley Alderwoods SAC are considered to be one of the best areas in the UK for alder woodland on floodplain, which is now rare throughout Europe. The water level objectives for the site are to maintain the current hydrological conditions resulting from variation in the water levels (from surface flooded to relatively dry) and to maintain the level of flooding during winter.

Policies P1 to P3 could therefore have an adverse impact on these habitats.

P4 can only realistically be achieved in this policy unit (in the short-term) with quite a significant increase in resources (to remove restrictions to flow in most towns and villages) or to make more of the existing properties at risk resilient to flooding. P6 assumes the same level of resource so that this risk reduction can take place alongside environmental improvements.

The potential (at a technical level) to enhance and expand the existing habitat is very high in the Kennet. The existing habitat is significant at a regional scale, there is potential for improvement and this would be compatible with our aim of maintaining or enhancing the capacity of the natural floodplain to store water. The Kennet floodplain is one of the areas with the highest potential for wetland BAP creation across Thames region, due to current soil type, geology and environmental conditions. There is also a fairly high potential for both land use and land management change. The major risk in this policy unit is from potential development within the floodplain upstream of Reading. This development will be resisted. It is not compliant with PPS25 or the objectives within this policy unit. Risks, Uncertainties & P4, P5 and P6 can all complimentary policies (short, medium and long-term Dependencies approaches), P4 is dependent upon reaching a strategic vision with key local authorities on what can be achieved through redevelopment, P5 is largely dependent upon the criteria for future investment and P6 will be dependent upon both and the overall progress in applying Making Space for Water. Regional Low overall. Some can be achieved through an evolution of approach and the Priority (0-5yrs) priority recognises that the rate of change will be moderate. Policy key and Selected Policy policy Sustainable Policy (not selected because of constraints) approaches Most likely short-term outcome (where this differs from the selected policy) P1 Do Nothing P2 Flood Warning and awareness through existing mechanisms Emergency maintenance to remove blockages in urban locations P3 P2 + Maintain conveyance in urban areas & the capacity of the natural floodplain Application of PPS25 P4 P3 + Strategic application of PPS25 to achieve optimal location, layout and design of redevelopment (with a focus in Newbury and the floodplain upstream of Reading) P5 P4 + Resilience and / or small scale flood alleviation options e.g. Newbury P6 P4 or P5 + Maintaining or enhancing the capacity of the natural floodplain Enhancing or expanding BAP habitat Resource The selected policy would require additional resources. With a shift in the use Implications of existing resources, we can start to implement approaches that will eventually contribute to the implementation of the policy. Indicative resources at this stage:

Making Space for Water Planning: £100k

Newbury: £2m

Spatial Planning: £50k

Biodiversity: unknown

Key Actions Spatial Planning (Developed in Making Space for Water Action Plan) Maintenance Flood warning and awareness Planning future improvements

Policy Unit Commentary

The diverse characteristics of the Kennet policy unit shape the opportunities and constraints in developing our approaches to managing the future flood risk. This includes the following key characteristics;

- The majority of the 4,000 properties at risk from flooding in this policy unit are located along the River Kennet; most notably in Newbury, but also in Marlborough, Hungerford, the Theale area and Reading. - Within the Kennet catchment are many water dependent habitats including two internationally designated sites; the Kennet and Lambourn floodplain SAC, and Kennet Valley Alderwoods SAC. - The Kennet catchment is predominantly a chalk catchment. The flood hydrographs are strongly influenced by groundwater; they have relatively low peak flows and are of long duration. - Multitude of local scale issues. For example, the vast majority of structures in the policy unit are privately owned.

Though the majority of the properties at risk are in the middle and lower reaches of the catchment (from Newbury downstream), large-scale strategic interventions to reduce the probability of flooding are not considered feasible. There are three major technical constraints to flood storage for example. Firstly, the long duration of flooding would mean that storage areas would need to be very large, the permeable chalk geology presents constraints on any design and the impacts on water levels and flows at the designated sites would need to be at worst, neutral. There are not, therefore, large-scale strategic solutions to reduce the probability of flooding in the Kennet policy unit and they will not be investigated.

Our overall message that flood defences cannot be built to protect everything is important in the Kennet. A combination of works to improve the conveyance of river channels along with raised flood defences to protect clusters of properties may well be possible in some locations. In Newbury we will investigate potential opportunities to improve conveyance through the town. This includes reducing the impact of existing restrictions to flow and local protection to vulnerable locations. Possible local protection should be considered alongside the lifespan of the vulnerable areas at risk (for example recognising that some industrial or semi-industrial areas may be redeveloped within the next few decades). Areas that are likely to be redeveloped in the foreseeable future should not be protected by flood defences if there is a more sustainable alternative. Redeveloping these locations to be resilient to flooding is likely to be more sustainable as it will reduce the cost of future maintenance, contribute to re-establishing a river corridor and the overall policy within the Kennet policy unit.

Our future approach to managing the flood risk in the Kennet will comprise the following characteristics;

- It will be locally focussed under a general policy. - Our objective of enhancing the capacity of the floodplain applies to all of the non-developed parts of this catchment, but the opportunity to achieve this will be variable and apply mainly at a local scale. Reviews of Water Level Management Plans, System Asset Management Plans and Performance Specifications will be the primary means of delivery and this will need to be integrated to meet this overall objective. - In the Kennet our approach will be aligned to the wider water and environmental objectives through management of the channel and floodplain. This will enhance and expand the existing floodplain habitats and could result in some localised flood risk reduction.

Our approach recognises the environmental assets within the floodplain, which include two internationally designated sites. In general the condition of these sites is satisfactory, but there are opportunities to improve their condition by modifications to channel morphology, expanding habitat to increase resilience and in some cases more regular or longer-duration of floodwater. These kinds of improvements can only realistically be implemented through site specific measures to modify water levels and flow.

Most of the towns and villages where there are properties at risk from flooding are well established. Our overall message that regeneration and redevelopment offer a crucial opportunity to reduce the flood risk is important, but will have a smaller impact here than other parts of the region, reflecting the low level of regeneration. Strategic Flood Risk Assessments in the Kennet need to focus on the application of the sequential test to avoid inappropriate development in the floodplain and ensure that policies do lead to risk reduction where redevelopment does occur. The message that new flood defences are highly unlikely in most places enforces this message. Providing the appropriate Strategic Flood Risk Assessments are carried out and we have policies based on PPS25 within Local Development Frameworks, then a Spatial Planning delivery plan will not be needed across the whole policy unit.

Our message that floodplain management is a sustainable way of managing flood risk is particularly relevant in and around Newbury. However in terms of managing the developed floodplain, most of the properties at risk are well established and competing demands mean that an acceptance of some level of flood risk is deemed sustainable.

For this reason it is crucial that the Strategic Flood Risk Assessment and Local Development Framework’s here adequately addresses the flood risk issues. Establishing clear policies in these documents will ensure that development is appropriate when assessed against the risk of flooding. It will also be the catalyst for a transition to a floodplain that is more accommodating of the Kennet and its tributaries, and increasingly resilient to flood water.

For instance, where the sequential approach is followed and application of the Exception Test demonstrates that regeneration of areas within the floodplain can be sustainable, then opportunities can be taken to combine regeneration and environmental improvements with a wider strategy to manage flood risk. In these areas very close attention should be paid to Chapter Five (Risk Management by Design) of the PPS25 Development and Flood Risk Practice Guide in setting policy, carrying out SFRA’s and planning developments.

With properties at flood risk dispersed widely throughout the policy unit, flood warning is an important approach to managing the risk. Throughout most of the policy unit flooding will only occur after a long period of rainfall and there is generally an adequate time to issue and respond to flood warnings.

Kennet - Policy Delivery

What we want to achieve Action and Mechanism Indicator Partners Timescale Maintain the capacity and function of Develop a potential action plan to implement a flood risk Link to Environment By 2010 the undeveloped natural floodplain to management regime based on Making Space for Water principles. Outcome Agency, retain water so that it can continue to This will need to include a broad assessment of the costs and benefits Measures reduce the impact of low order flood and include a link to Outcome Measures. The plan, initially could, for events to people and property. example, focus on the following:

Seek to enhance the capacity of the 1. Identify areas of floodplain where the capacity to retain water could undeveloped natural floodplain. be enhanced. Cross check this with the current Performance Recognising that this will require Specifications and developing Asset System Plans. structural measures, this is more likely to be achievable upstream of sizeable communities at risk from flooding 2. Identify those areas from (1) that are upstream of property and where the social, economic benefits carry out a broad assessment of the benefits. Build up an iterative are more clear-cut. picture of the such opportunities within the upper Thames to gain some sense of the cumulative local benefits and cumulative Align the objective of maintaining or catchment benefits. Assess the degree of attenuation that could enhancing floodplain capacity with potentially be achieved. expansion and enhancement of floodplain environments, particularly 3. From areas identified in (1), assess the proximity to existing BAP

BAP habitat habitat and the potential to combine the use of floodplain with enhancement or expansion of floodplain BAP habitat (notably fen, marsh swamp and reed bed)

4. From existing work, map those areas where there is potential to reduce rural run-off through land use change or land management change. Assess their potential effectiveness by their proximity to properties at risk from flooding.

What we want to achieve Action and Mechanism Indicator Partners Timescale Continue to reduce the impact of low Define adequate conveyance within developed areas through SAMPS Environmen 2007-2020 order flooding in urban areas (up to a and Performance specs 10% to 20% AEP flood – 1in 10 to 1 in t Agency, 5 year return period) by maintaining Define and implement EA maintenance regime to meet these Landowners conveyance where it both effective and sustainable to do so. objectives

Communicate this to communities (link to community consequence Align the objective of maintaining or management) – perhaps akin to a proactive flood surgery in many enhancing floodplain capacity with expansion and enhancement of communities irrespective of whether flooding has occurred recently floodplain environments, particularly BAP habitat Encourage communities to self regulate and where critical enforce

The level of maintenance that we carry out to river channels and riverbanks is prioritised according to the level of flood risk and the effectiveness of the maintenance in reducing the likelihood of flooding in a particular place. Maintenance is generally effective in reducing the impacts of flooding that would be expected to occur most winters so the objective of our maintenance is to reduce the impact of low order flooding up to a 20% to 10% AEP flood (1 in 5 year to 1 in 10 year return period). In flood events more extreme than this, channel and bank maintenance (including dredging) has no impact and is therefore ineffective in managing the flood risk in these situations.

Reduce the consequences of flooding Identify those places where an adequate flood warning is not currently through continued action to raise provided public awareness of flooding, tailoring the advice and approach (e.g. Investigate whether this situation can be improved and where possible community based) to ensure those ‘at risk’ take appropriate action to respond implement e.g. through detection or forecasting. to flooding. Where this situation cannot be improved, work with the Local Authority to address the question of what is vulnerable, what is the response under what circumstances

Compliment the warning available with an awareness and action plan to ensure consequences of flooding reduced.

What we want to achieve Action and Mechanism Indicator Partners Timescale Safeguard the existing undeveloped Through future revisions of the SFRFA’s and LDF’s or otherwise seek natural floodplain through the to achieve long-term reductions in the consequences of flooding. appropriate application of the Consider whether this requires a change in approach (necessitating a sequential test within PPS25. There short delivery plan) or whether this can be achieved through day to day are development pressures to develop implementation of PPS25. Greenfield sites in the floodplain close to existing urban centres (for example in the Theale / Reading area) that The Strategic Flood Risk Assessment (SFRA) is crucial in delivering need to be resisted. the spatial planning and flood resilience responses in Newbury.

Maintain, or in some cases re- In this instance the SFRA recommendations and LDF policies need to establish, river corridors so that urban focus on: areas can better accommodate flooding (location and layout) and the • Long-term master-planning for Newbury to establish an urban buildings are more resilient to flooding corridor that is more accommodating of flooding and its location in (design). In the long-term this should a floodplain. The outcomes here will be long-term and need to be achievable through re- relate to the action below on improving conveyance. development. It must be recognised • Using the sequential approach and applying the exception test if that this is a long-term objective (e.g. necessary. Newbury). • Establishing a Functional Floodplain (to be discussed and agreed

locally). • All redevelopment to be flood resilient (i.e. raised floor levels). Establish priorities for retro-fitting of vulnerable assets. • Safeguarding natural floodplain from future development through the appropriate application of the sequential test. In Newbury define options to improve Progress investigations to improve conveyance through Newbury. This conveyance (for example by removing includes reducing the impact of existing restrictions to flow and local restrictions to flow) to complement protection to vulnerable locations. Possible local protection should be wider catchment approaches to considered alongside the lifespan of the vulnerable areas at risk (for maintain or enhance the capacity of the natural floodplain and the objective example recognising that some industrial or semi-industrial areas may of re-establishing a river corridor that be redeveloped within the next few decades). Areas that are likely to can better accommodate flooding. be redeveloped in the foreseeable future should not be protected by flood defences if there is a more sustainable alternative. Redeveloping these locations to be resilient to flooding is likely to be more sustainable as it will reduce the cost of future maintenance, contribute to re-establishing a river corridor and the overall policy within the Kennet policy unit.

Figure 6.3.9a Properties at risk from a 0.1% AEP flood event in the Kennet policy unit

Loddon Policy Unit

The Loddon policy unit is characterised by fairly extensive floodplains, and has some small clusters of development in the downstream part of the catchment close to the River Thames. Our flood risk management approach for this type of catchment is outlined below.

Undeveloped natural floodplain

• The floodplain is our most important asset in managing flood risk.

• We want to safeguard the natural floodplain from inappropriate development.

This approach will deliver our policy for the River Loddon catchment: Take action to increase the frequency of flooding to deliver benefits locally or elsewhere with the aim of overall flood risk reduction

Loddon - What we want to achieve

¾ Maintain the capacity and function of the undeveloped natural floodplain to retain water so that it can continue to reduce the impact of low order flood events to people and property.

¾ Align the objective of maintaining or enhancing floodplain capacity with expansion and enhancement of floodplain environments, particularly BAP habitat.

¾ Safeguard the existing undeveloped natural floodplain through the appropriate application of the sequential test within PPS25.

¾ Particularly in the Lower Loddon towns such as Winnersh, Charvil and Lower Early, seek to maintain or restore river corridors so that urban areas can better accommodate flooding (location and layout) and the buildings are more resilient to flooding (design). In the long-term this should be achievable through re-development. It must be recognised that this is a long-term objective.

¾ In the Lower Loddon towns, progress investigations to conclude which approaches would be most suitable to manage existing and future flood risk. This could be to manage the probability of flooding (for example through defences), or the consequences (for example through resilience). Specifically assess the viability of these options in the Lower Loddon. Option selection should be based on what is most effective and sustainable and not short-term factors (for example, the ease of capital funding streams).

Loddon: SEA, Key Approaches and Regional Priority

Summary of the Preferred Approach Policy Unit Loddon

0.6% of the economic consequences of fluvial flooding in Thames region

0.2% of the social consequences of fluvial flooding in Thames region

3.6% of the floodplain, channel and designated environmental assets in Thames region

• 970 properties at risk from a 1% AEP flood event

Problem / Risk • 2100 properties at risk from a 0.1% AEP flood event • Low levels of social deprivation • Approximately 4.1km2 of floodplain BAP habitat (predominantly floodplain grazing marsh with areas of fen, wet woodland and reedbed). • 42km2 of floodplain (91% undeveloped and 9% urban) • 254km of natural channel • 5km of maintained or modified channel or culverts.

Within the Loddon policy unit there are no water-dependant internationally designated sites.

P6: Take action to increase the frequency of flooding to deliver benefits Policy locally or elsewhere (which may constitute an overall flood risk reduction, e.g. for habitat inundation). • Approx £300 k pa on maintaining channel conveyance to reduce the Existing impact of high frequency, low order events (up to 5% AEP). Based on Approaches and detailed flood modelling which covers approximately 50% of the Loddon Impacts policy unit, at least 90 properties are at risk in a 20% AEP flood, whilst there are at least 400 properties at risk from a 5% AEP flood. The proportion of properties at risk from 20% AEP flooding is quite low for such a rural policy unit. Maintenance costs per property at risk are above average for the region as a whole in the Loddon policy unit. The effectiveness of this maintenance in managing the risk to the majority of properties at risk requires evaluation. • Approximately 25% of properties are signed up to the direct flood warning service. • Application of PPS25 The selected policy sets a direction for this policy unit to try and maintain and Justification maximise the key opportunities associated with the extensive natural (Balancing Objectives) floodplain. The priority recognises that in the context of Thames region, the existing flood risk to people and property is moderate. Maintaining or enhancing floodplain capacity to store water to provide direct environmental benefit and small, localised economic and social benefits.

Very long-term reduction in the consequences of flooding, particularly in the Lower Loddon towns.

The current land use within this policy unit does allow the possibility of Policy unit-wide widespread flood storage to reduce flood risk to people and property. Broad Opportunities & scale modelling indicates that reducing peak flows by storing approximately Constraints 10% of a typical 1% AEP flood would reduce damages within the policy unit in the order of 15%.

The impact on downstream policy units would depend very much on the pattern of rainfall. There is the potential to reduce flood damages (Thames Sandford to Cookham and the Lower Thames) in the order of 1% to 2%. However, in some events the peak from the Loddon will have passed before flooding on the Thames occurs. P1 assumes 300 properties flood annually. This scenario increases AAD from £1,200k to £7,800k.

For P3, damages, properties and people at risk reflect the impacts of climate change in this policy unit. Under P4, widespread strategic application of PPS25 can reduce the consequences of climate change in the long-term. If resilience is widely adopted the consequences of flooding could be reduced to below the baseline under this policy. However, its implementation is uncertain. The majority of the Loddon is already natural channel, therefore there are very limited opportunities for further river restoration in this policy unit. Assessment of proposed approach P5 assumes flood defences have been constructed for the Winnersh and (Against Lower Earley area. Economic, Social and Environmental Under P6, Making Space for Water with a focus on maintaining or enhancing Indicators) the capacity of the natural floodplain can be applied in combination with P4 or P5. P5 is largely dependent upon future resource levels whilst P4 is more long-term in its impact, likely to be more sustainable but not meet all expectations. Implementation of P6 will require an evaluation of the impact of maintenance in this policy unit.

P6 offers the greatest potential to create new wetland BAP habitat. The Loddon floodplain is one of the areas with the highest potential for wetland BAP creation across Thames region, due to current soil type, geology and environmental conditions. There is currently over 4km² of wetland BAP habitat in the Loddon, mainly floodplain grazing marsh. It is beneficial to create new habitat close to existing sites therefore the Loddon catchment is ideal for creating new BAP habitat whilst also providing flood risk benefits. There is also some potential for both land use and land management change. Risks, Uncertainties & There are no regionally significant risks in the Loddon policy unit as a whole. Dependencies Regional Low overall. Opportunities e.g. through LDF reviews and Strategic Flood Risk Priority (0-5yrs) Assessments that lead to long-term changes in the character of the urban areas at risk from flooding in the Lower Loddon need to be pursued. Policy key and Selected Policy policy Sustainable Policy (not selected because of constraints) approaches Most likely short-term outcome (where this differs from the selected policy) P1 Do Nothing P2 Flood Warning Emergency maintenance to remove blockages P3 P2 + Maintain conveyance Application of PPS25 P4 P3 + Strategic application of PPS25 to achieve optimal location, layout and design of redevelopment in the Lower Loddon Telemetry and flood warning improvements Flood resilience P5 P4 + Possible flood defences in the Lower Loddon P6 P4 or P5 + maintaining or enhancing the capacity of the natural floodplain BAP creation Resource Gradual shift of resource towards Making Space for Water. £100k of planning Impliations in the next five years.

Key Actions Maintenance (Developed in Spatial Planning with a focus on robust SFRA’s Action Plan) Flood Warning and flood awareness Options to reduce flood risk in the Lower Loddon

Policy Unit Commentary

The floodplains in the Loddon catchment are generally undeveloped grass meadows. Towards the downstream end of the catchment near the confluence with the River Thames, however, the floodplain is developed and several hundred properties at risk from flooding, mainly in Wargrave, Lower Early and Arborfield. Rural tributaries of the River Loddon such as the Lyde and Whitewater originate from chalk springs at the foot of the North Downs. These tributaries are mainly rural in character with some growth areas located towards the headwaters. Flooding tends to occur – particularly in the downstream reaches – after prolonged heavy rainfall. In the upper reaches of the tributaries of the Loddon localised groundwater flooding can occur after prolonged wet seasons

The Loddon catchment contains a wide range of habitats and species, many of which are dependent on water level and flow; for example, fen, reed beds and chalk streams. There are approximately 62ha of fen, marsh swamp and reed bed in the Loddon catchment (3% of this type of habitat in SE England). This is a particularly fragmented and vulnerable water dependent habitat.

There are no major flood defence schemes in the Loddon catchment. Local sluices and small weirs in numerous areas provide localised, but limited water level control. The most concentrated area of flood risk is in the Lower Loddon. The Loddon discharges to the River Thames in an area where there is a wide and flat floodplain; at times of flood, water from the Loddon can back up against the water from the Thames and cause flooding in Wargrave. The flooding mechanisms here are complex and it is not possible to significantly reduce flood risk in the Lower Loddon by simply by improving the conveyance of the river. Immediately upstream in Charvil, Winnersh, Lower Earley and Arborfield flooding is essentially caused by water spilling out of banks when the capacity of the channel is exceeded. However, constrictions close to mills and weirs and the presence of a perched channel do exacerbate flooding at a local scale.

It is possible that there is some form of strategic solution to flooding in the Lower Loddon as there is a large undeveloped floodplain upstream where some form of attenuation could reduce the risk of flooding. In view of the moderate level of flood risk, the topography of the catchment, the complex mechanisms of flooding, environmental designations and potential cost, on balance a strategic scale scheme is unlikely any time in the future. There may also be viable flood defence schemes to protect some properties in the Lower Loddon, but at present, it is uncertain whether they will attract funding.

Our proposed approach to managing the flood risk is based on maintaining the capacity and function of the floodplain to retain water. The floodplains of much of the Loddon provide natural storage of water during times of flood. This reduces the impact of flooding to property locally within this flood risk area and downstream. We are adopting a policy of accommodating more flooding in the undeveloped; this recognises the current value of the Loddon floodplain and how with further intervention its value can be maintained or enhanced. This approach may, for instance, have a role in our adaptation to the possible impacts of climate change. At present our ability to manage the flood risk by further improving the capacity of the floodplain to retain water is uncertain. This entire approach is dependent upon Making Space for Water principles being put into practice. We will need to work alongside new partners, and establish different ways of working. Until then, there will continue to be a role for our current risk management activities.

During the next five years there will be a scrutiny of watercourse maintenance in rural areas and there may be some reduction in the scale of watercourse maintenance in the Loddon. As described, some flood protection is provided by the capacity of the river channels and storage within the natural floodplain. The level of maintenance that we carry out to river channels and riverbanks is prioritised according to the level of flood risk and the effectiveness of the maintenance in reducing the likelihood of flooding in a particular place. Maintenance is generally effective in reducing the impacts of flooding that would be expected to occur most winters so the objective of our maintenance is to reduce the impact of low order flooding up to a 20% to 10% AEP flood (1 in 5 year to 1 in 10 year return period). In flood events more extreme than this, channel and bank maintenance (including dredging) has no impact and is therefore ineffective in managing the flood risk in these situations.

Most of the towns and villages where there are properties at risk from flooding are well established. Regeneration and redevelopment can offer a crucial opportunity to reduce the flood risk. Strategic Flood Risk Assessments in the Loddon catchment need to focus on the application of the sequential test to avoid inappropriate development in the floodplain and ensure that policies do lead to risk reduction where redevelopment does occur. We are seeking to lower flood risk through revised layout of redevelopment schemes (for example, the Winnersh Triangle redevelopment) and implementation of SuDs. The message that new flood defences are uncertain in most places enforces this message. Providing the appropriate Strategic Flood Risk Assessments are carried out and we have policies based on PPS25 within Local Development Frameworks, then a Spatial Planning delivery plan will not be needed across the whole policy unit. A limited amount of further investigation is needed to identify where there are specific opportunities to reduce the risk through redevelopment; for example in Winnersh.

With many properties at flood risk dispersed widely throughout the policy unit, flood warning is an important approach to managing the risk. Throughout most of the policy unit flooding will only occur after a long period of rainfall and there is generally an adequate time to issue and respond to flood warnings. However this needs to be complimented with an awareness and action plan if the consequences of flooding are to be significantly reduced. This may include enhancing the telemetry network and improving forecasting potential and techniques, along with raising general flood risk awareness and increasing the number of people registered to receive direct flood warnings.

Flood proofing existing properties at risk may prove to be a viable option for managing some of the flood risk in the Loddon policy unit. Pending the outcome of Defra pilots into flood proofing, it may be that vulnerable properties could benefit from such approaches. Loddon - Policy Delivery

BAP habitat habitat and the potential to combine the use of floodplain with enhancement or expansion of floodplain BAP habitat (notably fen, marsh swamp and reed bed)

What we want to achieve Action and Mechanism Indicator Partners Timescale Continue to reduce the impact of low Define adequate conveyance within developed areas through Environment 2007-2020 order flooding in urban areas (up to a SAMPS and Performance specs 10% to 20% AEP flood – 1in 10 to 1 in Agency, 5 year return period) by maintaining Define and implement EA maintenance regime to meet these Landowners conveyance where it both effective and sustainable to do so. objectives

Communicate this to communities (link to community Align the objective of maintaining or consequence management) – perhaps akin to a proactive flood enhancing floodplain capacity with expansion and enhancement of surgery in many communities irrespective of whether flooding has floodplain environments, particularly occurred recently BAP habitat Encourage communities to self regulate and where critical enforce

The level of maintenance that we carry out to river channels and riverbanks is prioritised according to the level of flood risk and the effectiveness of the maintenance in reducing the likelihood of flooding in a particular place. Maintenace is generally effective in reducing the impacts of flooding that would be expected to occur most winters so the objective of our maintenance is to reduce the impact of low order flooding up to a 20% to 10% AEP flood (1 in 5 year to 1 in 10 year return period). In flood events more extreme than this, channel and bank maintenance (including dredging) has no impact and is therefore ineffective in managing the flood risk in these situations.

Reduce the consequences of flooding Maintain and improve the flood warning service, further telemetry may through continued action to raise be need on the Whitewater, increase public awareness to get the at public awareness of flooding, tailoring risk public to take appropriate action to respond to flooding. the advice and approach (e.g. community based) to ensure those ‘at risk’ take appropriate action to respond to flooding. What we want to achieve Action and Mechanism Indicator Partners Timescale Safeguard the existing undeveloped Highlight those areas where redevelopment can have the most direct natural floodplain through the and effective impact on flood risk and then engage in very early appropriate application of the dialogue with relevant Local Planning Authorities – for example sequential test within PPS25. redevelopment schemes in the Lower Loddon in the Winnersh Triangle

Particularly in the Lower Loddon towns area). Here, there are opportunities to reduce flood risk through revised such as Winnersh, Charvil and Lower layout of development. Early, seek to maintain or restore river corridors so that urban areas can SFRA’s are the key mechanism for applying the sequential test under better accommodate flooding (location PPS25, particularly in the Lower Loddon. and layout) and the buildings are more resilient to flooding (design). In the There are locations in the Lower Loddon where there is existing long-term this should be achievable development on functional floodplain. The long-term viability of such through re-development. It must be recognised that this is a long-term sites need to be considered in future revisions of SFRA’s. objective. The SFRA for the Lower Loddon is critical for identifying the main flood risk issues and their priority against other planning considerations. In the Lower Loddon towns, progress Revisit previous investigations on the viability of flood defences for the investigations to conclude which Lower Loddon. This may include; approaches would be most suitable to manage existing and future flood risk. This could be to manage the • Assess the impacts of climate change probability of flooding (for example • Assess the benefits and viability of alternatives (e.g. resilience) through defences), or the • Confirm the broad conclusions relating to storage consequences (for example through resilience). Specifically assess the This will most likely require a small-scale focussed strategy, rather than viability of these options in the Lower a large catchment wide strategy. Loddon. Option selection should be based on what is most effective and sustainable and not short-term factors (for example, the ease of capital funding streams).

Figure 6.3.11a Properties at risk from a 0.1% AEP flood event in the Loddon policy unit Figure 6.3.11b Wetland BAP habitat in the Loddon catchment

Appendix D

Maps of Areas Potentially Vulnerable to Groundwater Emergence

The following text has been extracted from the Jacobs 2004 Scoping Report as a first point of reference to accompany the above maps, but for full details please see the original report.

The Groundwater Emergence Maps (GEMs) identify those parts of England where, in exceptionally wet winters, groundwater levels could be expected to be at or close to the ground surface. Where possible these maps have been calibrated on observations made in the winter of 2000-01. Where no flooding was reported, or information was not made available, the maps indicated estimated areas based on anticipated groundwater levels using relevant aquifer properties or river baseflow indexes.

The GEMs do not imply flooding per se, only that groundwater could be sufficiently close to the surface to cause flooding, pending local conditions such as local geology, drainage and developments. The impact of groundwater being at or close to the surface is largely dependent on its frequency of occurrence. Those areas that have groundwater near the surface on an annual basis, would normally have drainage systems adapted to the annual flow range experienced. It is in those areas, normally at the upper reaches of the catchment that experience high groundwater only rarely, where problems of flooding are most likely to be experienced. Typically, drainage paths in these areas will be poorly defined and unable to cope with the flow, and cellars and basements may flood from seepage. Within the zones identified the following impacts are possible:

Emergence of new or rarely experienced springs; Migration of stream sources high into the headwaters; Emergence of water into underground structures; DEFRA Final_rev.doc/May-04 2-12 Emergence of water at the surface; Flooding of properties; Local drainage network overwhelmed by rate of flow; Large areas of standing water; Surcharging sewer network; Failure of electricity supplies; Inundation of roads, restricting vehicle movements and deterioration of the surface cover; and Damage to crops.

The GEMs are composite maps constructed using information from a variety of sources. Inevitably, the quality and applicability of the data varied, for example the available data on groundwater levels typically covered the 1970s rather than 2000-01. Consequently, the confidence that can be placed on the maps will vary from area to area. In order to provide an indication as to the reliability of the maps, they have been ranked from 1 to 3 where 1 represents a high degree of confidence in the mapped area.

There are some locations, mainly consisting of minor aquifers, where groundwater level data are unavailable or, in many cases, groundwater levels are not monitored. To ensure comprehensive coverage of all areas with the potential to cause groundwater flooding the Base Flow Index derived from the Hydrology Of Soil Types (BFIHOST) classification has been applied to the rivers network from the Centre for Ecology and Hydrology (CEH). The Base Flow Index is an indication of the proportion of water in the river that is derived from groundwater and other sources of stored or slowly released water. Simply, the greater the proportion of baseflow, the greater the propensity to flood from this stored water. The GEMs all show BFIHOST classified according to four categories. Those with a base flow in excess of 0.9 (90% flow) being heavily dominated by baseflow and typically being Chalk fed. The next two categories are less dominated by baseflow with proportions of 80% and 70%. All other rivers are shown as blue and indicate those rivers in which baseflow does not play a major part in the flow regime. Those sections of rivers coloured grey are unclassified and arise from a poor fit between the rivers network and the BFIHOST network. As the proportion of baseflow drops, the more flashy the flow regime becomes and it would be expected that surface runoff floods become dominant. Whilst the coloured rivers do indicate the proportion of baseflow on the established rivers, it is the minor rivers upstream that are the most vulnerable. However, displaying the more detailed drainage path network is inappropriate at this scale of mapping.

In addition to the groundwater emergence zones and the river networks, the GEMs show locations of historical flooding in 2000/01 for comparison. In Hampshire there are some outlying observations beyond the defined zones suggesting local influences on groundwater emergence.

Appendix E

RAINFALL RUNOFF MANAGEMENT FOR DEVELOPMENTS – INTERIM NATIONAL PROCEDURE

1. Procedure status. This procedure is an interim method, which is expected to be revised as improved tools are developed. It utilises well recognised existing methods, but revision is anticipated to provide a more consistent approach as and when FEH procedures can be extended to catchments at development scale.

2. Compliance to national guidance. The objective of this procedure is to assist developers and their designers to conform to PPS25.

3. Application of the procedure. This procedure applies to both greenfield and brownfield sites. In the case of brownfield sites, drainage proposals will be measured against the existing performance of the site (although it is preferable for solutions to provide runoff characteristics which are similar to greenfield behaviour). Therefore where greenfield performance is referred to in this document, this should be considered as meaning the existing site conditions for brownfield redevelopment sites. Sites with polluted land will have particular consent requirements and affect the drainage techniques that can be used.

4. Use of infiltration. Part H of the Building Regulations requires that the first choice of surface water disposal should be to discharge to infiltration systems where practicable. Infiltration techniques should therefore be applied wherever they are appropriate.

5. Sewers for Adoption. Drainage calculations and criteria, where appropriate, should comply with the 6th edition of Sewers for Adoption.

6. Need for this procedure. It is recognised that the impact of urban development on greenfield areas increases both the rate of run-off and the volume of run-off in response to rainfall and that the water quality impact on the receiving watercourse is likely to be detrimental.

7. Procedure philosophy. The objectives of this procedure are to: • stormwater runoff discharged from urban developments to replicate or achieve a reduction from the greenfield response of the site over an extended range of storm probabilities (return periods) • manage runoff on site for extreme events.

This requires: • the peak rate of stormwater run-off to be controlled • the volume of run-off to be reduced • the pollution load to receiving waters from stormwater runoff to be minimised • the assessment of overland flows and temporary flood storage across the site.

8. Discharge rate criteria. The Environment Agency will normally require that, for the range of annual flow rate probabilities, up to and including the 1% annual probability (1 in 100 year event) the developed rate of runoff into a watercourse should be no greater than the undeveloped rate of runoff for the same event. Exceptions only apply where it is not practical to achieve this due to either constraints on the size of the hydraulic control unit (see point 17), or excessive storage volumes. The purpose of this is to retain a natural flow regime in the receiving watercourse and not increase peak rates of flow for events of an annual probability greater than 1%. Three annual probabilities merit specific consideration; 100%, 3.33% and 1%. (Note that in many places elsewhere in this Guide return periods are used instead of annual probabilities, as much historic nomenclature and many formulae use return periods).

8.1 The 100% annual probability (1 in 1 year event) is the highest probability event to be specifically considered to ensure that flows to the watercourse are tightly controlled for these more frequent events.

8.2 The 3.33% annual probability (1 in 30 years event) is of importance because of its linkage with the level of service requirement of Sewers for Adoption 6th edition (SfA6). SfA6 requires that surface water sewers should be capable of carrying the 3.33% annual probability event within the system without causing flooding to any part of the site.

8.3 The 1% annual probability (1 in 100 years event) has been selected since it represents the boundary between high and medium risks of fluvial flooding defined by PPS25 and also recognises it is not practicable to fully limit flows for the most extreme events. Also SfA6 recognises that, during extreme wet weather, the capacity of surface water sewers may be inadequate. SfA6 requires that the site layout should be such that internal property flooding does not result, by demonstrating safe above ground flow paths. The return period for this analysis is not specified, but it is recommended that 1% annual probability event (i.e. an event with a return period of 100 years) is used.

8.4 Flood flows. up to the 1% annual probability event should preferably be contained within the site at designated temporary storage locations unless it can be shown to have no material impact in terms of nuisance or damage, or increase river flows during periods of river flooding. Analysis for overland flood flows within the site will need to use short high intensity rainfall events of between 15 minutes and 1 hour duration.

9. The calculation of greenfield runoff rate. The calculation of peak rates of runoff from a greenfield site is related to its size. The values derived should be regarded as indicative due to the limitations of the existing tools. Table 9.1 summarises the techniques to be used.

Table 9.1 Tools to be used for calculation of greenfield run-off criteria Development size Method 0 – 50 ha The Institute of Hydrology Report 124 Flood Estimation for Small Catchments (1994) is to be used to determine peak green field runoff rates.

Where developments are smaller than 50 ha, the analysis for determining the peak greenfield discharge rate should use 50 ha in the formula and linearly interpolate the flow rate value based on the ratio of the development to 50 ha.

FSSR 2 and 14 regional growth curve factors are to be used to calculate the greenfield peak flow rates for 1, 30 and 100 year return periods. 50 ha – 200 ha IH Report 124 will be used to calculate greenfield peak flow rates. Regional growth factors to be applied. Above 200 ha IH Report 124 can be used for catchments that are much larger than 200 ha. However, for schemes of this size it is recommended that the Flood Estimation Handbook (FEH) should be applied. Both the statistical approach and the unit hydrograph approach should be used to calculate peak flow rates. The unit hydrograph method will also provide the volume of greenfield run-off. However, where FEH is not considered appropriate for the calculation of greenfield run-off for the development site, for whatever reasons, IH 124 should be used.

10. Volumetric criteria. The stormwater runoff volume from a site should be limited to the greenfield runoff volume wherever possible. The additional runoff volume caused by urbanisation should be controlled using two criteria.

10.1 Interception. Where possible, infiltration or other techniques are to be used to ensure minimal discharge to receiving waters for rainfall depths up to 5mm.

10.2 Additional runoff due to development. The difference in runoff volume pre and post-development for the 100 year 6 hour event, (the additional runoff generated) should be disposed of by way of infiltration, or if this is not feasible due to soil type, discharged from the site at flow rates below 2l/s/ha.

10.3 Where compliance to 100 year volumetric criterion, as defined in section 10.2, is not provided, the limiting discharge for the 30 and 100 year return periods will be constrained to the mean annual peak rate of runoff for the greenfield site (Referred to as QBAR in IH Report 124).

11. Percentage runoff from greenfield sites. The percentage runoff of the rainfall on a greenfield site can be assumed to be approximately equal to the SPR value of the soil type of the site. The SPR value can be used from either the Flood Studies Report (FSR) or the Flood Estimation Handbook (FEH).

12. Percentage runoff from developments. Calculation of the run-off volume from the developed site for preliminary assessment and design of drainage facilities will assume 100% run-off from paved areas and 0% run-off from pervious areas. Runoff from impermeable surfaces served by effective infiltration systems can be assumed to contribute no runoff for storage volumes assessment.

13. Detailed design of stormwater runoff. All network design for stormwater runoff and proof of compliance in meeting peak flow rate discharge criteria, using computer simulation, should use the standard Wallingford Procedure variable UK runoff model using appropriate parameters.

14. SUDS for water quality. SUDS units should be used to achieve water quality improvements and amenity benefits as well as achieving compliance to these hydraulic criteria. Best practice in achieving water quality protection should be used.

15. Reliability of SUDS. At present certain SUDS units are considered to have some degree of risk of medium term hydraulic failure, due to either maintenance or possible change of status. In these situations, to ensure compliance with pipe capacity criteria, they will be deemed not to be effective when calculating pipe sizes and storage requirements. For pipe sizing the current view of the Water Undertakers should apply (see the National SUDS Framework document). For storage sizing of all structures which are not to be adopted by Water Undertakers, the view of the Environment Agency should normally apply.

16 Climate change factor. Climate change will be taken into account in hydrological regions by increasing the rainfall depth by the recommended allowances in PPS25 for computing storage volumes. No allowance for climate change should be applied to calculated greenfield peak rates of runoff from the site for any hydrological region. It should be recognised that although climate change is acknowledged as taking place, certainty regarding the hydrological changes, particularly of extreme short duration events, is very low.

17. Minimum limit of discharge rate. A practicable minimum limit on the discharge rate from a flow attenuation device is often a compromise between attenuating to a satisfactorily low flow rate while keeping the risk of blockage to an acceptable level. It is suggested that this is 5 litres per second, using an appropriate vortex flow control device or other technically acceptable flow control device. The minimum size of pipe discharging from a flow attenuation device should be 150mm laid at a gradient not flatter than 1 in 150, which meets the requirements of Sewers for Adoption 6th Edition.

18. Catchment Flood Management Plans. CFMPs (Catchment Flood Management Plans), consider the impact of development on flood risk in the catchment based on existing land use plans contained in the local plan published by the Local Planning Authority and projections of development beyond the periods covered by the land use plans. Strategy Plans identified in the CFMPs each cover part of the catchment and may consider the local impact of these developments in more detail. Where these exist for an area proposed for development, their findings must be taken into account in the development proposal.

Further information can be found in the books:

Preliminary rainfall runoff management for developments (R & D Technical Report W5-074/A Revision D (Environment Agency and Kellagher R, 2004 - Free download from the Environment Agency web site www.environment-agency.gov.uk).

CIRIA C697 The SUDS manual (Woods Ballard B; Kellagher R et al, 2007 – available from CIRIA bookshop www.ciria.org)

Interim code of practice for sustainable drainage (National SUDS Working Group, 2004) - Free download from CIRIA web site www.ciria.org or Environment Agency web site www.environment-agency.gov.uk)

Appendix F

MINIMUM DEVELOPMENT CONTROL STANDARDS FOR FLOOD RISK

Basic Information to be submitted NOTES

Indicative Drainage Strategy required for all sites Soakaways BRE365 design is 1 in 10 years. Thus a lower Flood Risk Assessment (incorporating off-site impact) required for all si tes - proportionate to the risk and appropriate to standard than normal. See Ciria C609, p80. the scale, nature and location - taking account of flodding from any source Climate Change Developers should assume a 20% increase in On-site Standard rainfall depth or 30% if lifespan greater than 2085 for computing storage volumes and a 20% increase in peak river flows. Demonstrate compliance with Building Regs H3 - i.e. chec k infiltration feasibility, give perference to soakaways Green field run-off For sites < 1ha the maximum discharge rates Basically Sewers for Adoption standard can be prorated against 0.6l/s, 1.7l/s and 2.3 l/s • 1 in 2 year pipe full (with exceptions) for 1in1, 1in30 and 1in100year events respectively for 1 ha. For all storms up to 1 in • 1 in 30 year no site flooding 100 years +CC but with a minimum of 2 l/s for No property flooding for 1 in 100 yr (+CC) very small sites. For all drainage the same standard as CIRIA C609, p80 Existing Impermeable Areas For sites < 1ha the maximum discharge rates Flows beyond 1 in 30, but up to 1 in 100 years (+CC), should be stored on site (e.g. in car parks, hollows, etc) unless run-off can be prorated against 53l/s, 156.7l/s and from site has no unreasonable adverse im pacts compared with the existing situation. Flow routing design within the site 231.3l/s for 1in1, 1in30 and 1in100year events boundary should follow CIRIA C635 Designing for Exceedance in Urban Drainage respectively for 1ha. For all storms up to 1 in 100 years +CC but with a minimum of 2 l/s for Freeboard above 1 in 100 years (+CC) fluvial flood level should be: 600mm for dwellings, 400mm for office & very small sites. commercial, 300mm for industrial and warehousing, 300mm for entrance to u/ground car parks Discharge Calculations DEFRA/EA "Preliminary rainfall runoff management for developments" gives an Off-Site Impact approach to determine runoff rates and storage volumes. Flow Control Orifices Generally must not be less than 75 mm in No Soakaways where history of groundwater flooding or where flows could re-emerge to flood lower level property diameter (C609, p75). Point of Connection To a watercourse or sewer must be such that it will not create additional flooding due to Green Field Brown Field increased flow rates or volumes. (allowable discharges) (allowable discharges) Water Quality Car park petrol interceptors to be agreed with EA (interceptor is needed for car parks > 800 m2 or To watercourse or to sewer · Equivalent to existing peak flow rates up to 1 in 100 year > 50 car park spacings - See PPG3). • Equivalent Green field rates up to 1 in 100 years storm (+CC). Adoption/Maintenance (+CC) · Volume control as DEFRA/EA Preliminary rainfall runoff Clear-cut provisions for future maintenance. • Volume control as DEFRA/EA Preliminary rainfall management for developments. Major features (e.g. balancing tanks and ponds) runoff management for developments. to be maintained by a corporate body. • Additional downstream works may be required (See SUDS manual).

Combined 5% reduction; comparison to be made at 1 in 1year, 1in 30 years and 1 in 100 years. SURFACE WATER MANAGEMENT – CALCULATION & DRAWING REQUIREMENTS

Purpose: To assist developers in demonstrating that they are complying with latest guidance on managing surface water run-off the following calculations and drawings shall be submitted:

1) General Drainage Information

A summary sheet (1 page max) showing the global variables which have been used in the design of the surface water sewerage system.

For Basingstoke, the following values are typical: M5_60 = 20.0mm, Ratio_R = 0.40, Cv (Summer) = 0.750, Cv (Winter) = 0.840.

Note: The values of Cv may be increased by 20% or 30%, as appropriate, to model the effects of climate change, if there is not other provision in the developer’s software.

Pipe roughness: As per Sewers for Adoption guideline values.

The Following Key Data must be provided: (a) The total impermeable area of the whole development (b) The existing impermeable area and the allowable peak discharge from the site. (See page 1) (c) The total volume of attenuation storage which will be provided both above and below ground.

Provide a drawing showing a schematic of the drainage layout, with all pipes, manholes, ponds, etc clearly numbered or referenced to the model output.

On-Site Standards

2) No Surcharge up to 1 in 2 year return period Provide a summary sheet demonstrating compliance

3) No Flooding up to 1 in 30 year return period Provide a summary sheet demonstrating compliance

Off-Site Standards

4) Maximum Discharge Provide results of peak flow from site, which must be < allowable discharge

5) No Additional Run-off from site up to 1 in 100 years + Climate Change Provide results showing the peak water level in any ponds, or tank (and hence volume). Provide a drawing showing the size and location of all the attenuation storage provided. Where attenuation storage is located above ground, provide details of finished ground levels and demonstrate flood pathways to the storage areas.

Note: There is no need to provide reams of hydraulic calculations. There is a need to demonstrate compliance with the parameters given in Minimum Development Control Standards for Flood Risk, which are based on the provisions of PPS25.

SUDS TREATMENT CONSIDERATIONS

Table 5.6 Number of treatment train components (assuming effective pre-treatment is in place)

Taken from The SUDS Manual CIRIA report C697

Receiving water sensitivity Æ Low Medium High

Runoff catchment È characteristic Roofs only 1 1 1 Residential roads, 2 2 3 Parking areas, commercial zones Refuse collection/ 3 3 4 industrial areas/ loading bays/lorry parks/highways

Other Issues to be Considered

Source protection zones in proximity of the site Geological mapping Sensitive sites mapping as given in the appropriate Water Cycle Strategy

Choosing the right SUDS system The choice of SUDS system will depend on a number of factors such as: • the pollutants present in run-off; • the size of and drainage strategy for the catchment area; • the hydrology of the area and infiltration rate of the soil; • Groundwater Source Protection Zones or contaminated land.

Large-scale ponds and wetlands are generally more appropriate for sites larger than 5ha. Infiltration trenches, swales, filter strips and porous pavements are suitable for both large and small sites. The best drainage solution for a site will often incorporate a mix of mechanisms.

CALCULATION SHEET No: 2 of 5 Rev: 0 Flow comparison of green field and impermable runoff and for develpoment sites of Project: By: AB Date: 11/03/2008 1ha in Swindon, Basingstoke, London, Yeovil. Subject: Check Date: Greenfield Runoff (1) By: References/Results Site Characteristics-

1. Hydrological Region (1-10) ( R ) 5 (select from map below) The UK is divided into 10 Site location R SAAR (mm) hydrological regions reflecting the Swindon 6718.00 different flood frequency growth Basingstoke 6806.00 curves (Appendix 1, Figure 1) London 6 636.00 Yeovil 81060.00 SAAR from FEH info (csv file) Cambridge5 545.00

For each site the assumed AREA = 1ha

By using Windes - Source Control - Rural Runoff QBAR/ADAS is possible to easily calculate the greenfield runoff from the different sites

Rev 1 BPG121_F01(Excel) CALCULATION SHEET No: 4 of 4 Rev: 0 Flow comparison of green field and impermable runoff and for develpoment sites of 1ha Project: By: AB Date: 11/03/2008 in Swindon, Basingstoke, London, Yeovil. Subject: Check Date: Result Comparison By: References/Results

Resutl comparison between the Greenfield and impermable runoff:

Return period

Site LocationMethod 1 year 30 years 100 years

Grennfield Runoff 5.60 15.00 21.20 Swindon Impermeable Runoff 51.60 143.70 207.61 Grennfield Runoff 0.60 1.70 2.30 Basingstoke Impermeable Runoff 52.99 156.68 231.32 Grennfield Runoff 2.10 5.70 8.00 London l/s Impermeable Runoff 57.52 184.09 279.61 Grennfield Runoff 6.60 16.20 20.60 Yeovil Impermeable Runoff 51.82 153.79 227.32 Grennfield Runoff 1.80 5.90 7.40 Cambridge Impermeable Runoff 53.15 163.69 245.20

BPG121_F01(Excel) CALCULATION SHEET No: 3 of 4 Rev: 0 Flow comparison of green field and impermable runoff and for develpoment sites of 1ha in Project: By: AB Date: 11/03/2008 Swindon, Basingstoke, London, Yeovil. Subject: Check Date: Greenfield Runoff (2) + Impermeable runoff By: References/Results Here below is the results list:

Q (1:1year) Q(1:30years) Site Location Q(1:100years) l/s l/s l/s Swindon 5.6 15 21.2 Basingstoke 0.6 1.7 2.3 London 2.1 5.7 8 Yeovil 6.6 16.2 20.6 Cambridge 1.8 5.9 7.4 Greenfield Runoff (l/s)

Impermeable Runoff

Using the modified rational method

Q=2.78CIA

Where C Coefficient of runoff I Averagee age rainfall a a intensity te s ty during du g time t e of o concentration co ce t at o A Contributing Area

See below the average rainfall intensity (mm/hr) for a storm durations of 30minutes as obtained from FEH and Windes Return period

Site Location 1 year 30 years 100 years

Swindon 18.56 51.69 74.68 Basingstoke 19.06 56.36 83.21 London 20.69 66.22 100.58 Yeovil 18.64 55.32 81.77 Cambridge 19.12 58.88 88.2 Average rainfall intensity (mm/hr)

By appling the modified ratinal method formula and assuming:

C 1 (100% runoff) A1 ha I from table above

Return period Site Location 1 year 30 years 100 years Swindon 51.60 143.70 207.61 Basingstoke 52.99 156.68 231.32 London 57.52 184.09 279.61 Yeovil 51.82 153.79 227.32 Cambridge 53.15 163.69 245.20 Impermable runoff (l/s)

Rev 1 BPG121_F01(Excel)

Tables

Table 2: Historical Flooding - Southern Water Source: Southern Water

Date of most Sewer Problem Sewer Type Internal Curtilage Highway or Reference Tile recent incident Post town Locality Street Description Description Flooding Flooding Open Space SOW001 D 20001223 Andover St. Mary Bourne Church Street Hydraulic Foul/Combined Yes Yes SOW002 D 20010101 Andover Stoke Stoke Gate Hydraulic Foul/Combined Yes Yes SOW003 D 19990530 Basingstoke Overton Bridge Street Hydraulic Foul/Combined Yes Yes SOW004 D 19990530 Basingstoke Overton Bridge Street Hydraulic Foul/Combined SOW005 E 19990610 Basingstoke Oakley Hill Road Hydraulic Foul/Combined Yes Yes SOW006 E 19990610 Basingstoke Oakley Sainfoin Lane Hydraulic Foul/Combined Yes SOW007 D 19930401 Basingstoke Overton The Lynch Hydraulic Foul/Combined SOW008 D 20060914 Whitchurch London Street Hydraulic Foul/Combined Yes Yes SOW009 D 19990602 Whitchurch Bell Street Hydraulic Foul/Combined Yes

Note: This table is to be read in conjunction with Tiles A to F

Table 3: Historical Flooding – Thames Water Source: Thames Water

Postcode Tile Total number of properties Total number of properties Total number of properties Total number of properties flooded from overloaded flooded by surface water flooded by foul water from flooded by combined sewer in the last ten years from overloaded sewers in overloaded sewers in the overloaded sewers in the the last ten years last ten years last ten years RG7 3 C 4 0 4 0

Note: This table is to be read in conjunction with Tiles A to F

Table 4: Localised Flooding Areas Source: Basingstoke and Deane Borough Council and Parish Councils, Hampshire County Council

Reference Tile Source Of Flooding Occurrence Source of Outline Date Received B001 A Insufficient maintenance of st rare (1 in 20 years?) Workshop with Hampshire CC 18/01/2007 B002 A Backwater flooding from ditch rare Workshop with Hampshire CC 18/01/2007 B003 A Groundwater frequent Workshop with Hampshire CC 18/01/2007 B004 D Fluvial approx 1 in 20 years Workshop with Hampshire CC 18/01/2007 B005 D fluvial approx 1 in 20 years Workshop with Hampshire CC 18/01/2007 sewer system incapacity/poor condition and infiltration by high D 18/01/2007 B006 groundwater 2 to 4 years Hampshire CC and St Mary Bourne PC B007 E Groundwater approx 1 in 10 years Workshop with Hampshire CC 18/01/2007 B008 B Groundwater Workshop with Hampshire CC 18/01/2007 B009 B, F Runoff across field One off due to arch Workshop with Hampshire CC 18/01/2007 B010 B, F Fluvial and surface water and Workshop with Hampshire CC 18/01/2007 B011 B, C Groundwater (when pumps fail) 2 Workshop with Hampshire CC 18/01/2007 B012 B fluvial overtopping rare Workshop with Hampshire CC 18/01/2007 B013 B fluvial rare Workshop with Hampshire CC 18/01/2007 B014 B foul water (surcharge by surface water) once a year Workshop with Hampshire CC 18/01/2007 B015 B surface water and foul water once Workshop with Hampshire CC 18/01/2007 B016 B incapcaity of stream yearly Workshop with Hampshire CC 18/01/2007 B017 A fluvial often Workshop with Hampshire CC 18/01/2007 B018 B, C fluvial often Workshop with Hampshire CC 18/01/2007 B019 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B020 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B021 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B022 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B023 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B024 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B025 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B026 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B027 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B028 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B029 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B030 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B031 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B032 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B033 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B034 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B035 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B036 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B037 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B038 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B039 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B040 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B041 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B042 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B043 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 Reference Tile Source Of Flooding Occurrence Source of Outline Date Received B044 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B045 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B046 E, E1 Fluvial approx 1 in 20 years Plans provided by Hampshire CC 18/01/2007 B047 A, B Extents provided by Basingstoke BC 24/09/2007 B048 B Ashford Hill generally was blocked by flooding in the June storm. Extents provided by Basingstoke BC 24/09/2007 B049 B Extents provided by Basingstoke BC 24/09/2007 B050 B Frequent Extents provided by Basingstoke BC 24/09/2007 B051 B Surface water drainage Extents provided by Basingstoke BC 24/09/2007 B052 B, C Extents provided by Basingstoke BC 24/09/2007 B053 B, C Extents provided by Basingstoke BC 24/09/2007 B054 B, C Frequent Extents provided by Basingstoke BC 24/09/2007 Runoff from field north of Holly Bush Farm and overflow from blocked B055 B ditches. Extents provided by Basingstoke BC 24/09/2007 B056 B, C Blocked ditches and drains Extents provided by Basingstoke BC 24/09/2007 B057 B, C Extents provided by Basingstoke BC 24/09/2007 B058 B, C Extents provided by Basingstoke BC 24/09/2007 B059 B, C, F Extents provided by Basingstoke BC 24/09/2007 B060 B, C, F Extents provided by Basingstoke BC 24/09/2007 B061 B, C, F Extents provided by Basingstoke BC 24/09/2007 B062 B, C, F Extents provided by Basingstoke BC 24/09/2007 B063 B, C Extents provided by Basingstoke BC 24/09/2007 B064 B, C Extents provided by Basingstoke BC 24/09/2007 B065 B, C Extents provided by Basingstoke BC 24/09/2007 B066 B, C Extents provided by Basingstoke BC 24/09/2007 B067 B, C Extents provided by Basingstoke BC 24/09/2007 B068 B, C Extents provided by Basingstoke BC 24/09/2007 B069 B, C Extents provided by Basingstoke BC 24/09/2007 B070 C, F Extents provided by Basingstoke BC 24/09/2007 B071 C Extents provided by Basingstoke BC 24/09/2007 B072 E Extents provided by Basingstoke BC 24/09/2007 B073 E, F Extents provided by Basingstoke BC 24/09/2007 B074 B, C, F Extents provided by Basingstoke BC 24/09/2007 B075 B, F Extents provided by Basingstoke BC 24/09/2007 B076 B, C, F Extents provided by Basingstoke BC 24/09/2007 B077 B, C, F Extents provided by Basingstoke BC 24/09/2007 B078 B, C, F Extents provided by Basingstoke BC 24/09/2007 B079 B, C, F Extents provided by Basingstoke BC 24/09/2007 B080 F Extents provided by Basingstoke BC 24/09/2007 Axmansford was seriously affected by the July 2007 floods, especially the B081 B Bridge. Baughurst PC and Kingsclere PC 01/07/2008 B082 B Heathrow Copse was seriously affected by the July 2007 floods Baughurst Parish Council 01/07/2008 B083 B Wellington Crescent Hammerhead was seriously aff Baughurst Parish Council 01/07/2008 B084 B Stokes Lane/Inhurst Lane were seriously affected by the July 2007 floods Baughurst Parish Council 01/07/2008 Baughurst Road from Badgers Wood to Shaw Lane was seriously affected B085 B by the July 2007 floods. Baughurst Parish Council 01/07/2008 B086 B Tadley Town Council 01/07/2008 B087 B Surface water drainage Tadley Town Council 01/07/2008 Reference Tile Source Of Flooding Occurrence Source of Outline Date Received B088 B Surface water drainage Tadley Town Council 01/07/2008 B089 B, C Tadley Town Council 01/07/2008 B090 B, C Tadley Town Council 01/07/2008 B091 B, C Sewage overflowing Tadley Town Council 01/07/2008 B092 B Tadley Town Council 01/07/2008 B093 B Tadley Town Council 01/07/2008 B094 B, C Sewage overflowing Tadley Town Council 01/07/2008 B095 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B096 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B097 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B098 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B099 B Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B100 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B101 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 B102 B, C Blocked ditches and drains Monksherborne Parish Council 01/07/2008 River Test always rises, in conditions of flood occurrence, at the disused B103 E pit on the south side of the B3400. Oakley and Deane Parish Council 01/07/2008 Bridleway 90 is a prime source of runoff into the village. The lower part (The Dell) is a torrent after rain. Runoff carries silt to Gailey Brook (= B104 A, B Kingsclere Stream) Kingsclere Parish Council 01/07/2008 B105 B Localised flooding due to blocked ditches Sherborne St John Parish Council 01/07/2008 The B3051 immediately before the 40 limit frequently floods. The B106 B adjacent gardent has a large pond. Ditches in this area do not drain. Frequent Kingsclere Parish Council 01/07/2008 Houses at the bottom of Pyotts Hill flood during heavy rain from the water coming down the hill towards the river and then flowing into the B107 C, F homes before reaching the river. Old Basing and Lychpit Parish Council 01/07/2008 Houses have flooded from water coming off the fields behind them B108 C, F heading for the river. Old Basing and Lychpit Parish Council 01/07/2008 B109 B, C, F Poor drainage Regularly Old Basing and Lychpit Parish Council 01/07/2008 A30 going towards Basingstoke from Hook, just before Conkers Garden B110 C, F Centre Every 2 years Old Basing and Lychpit Parish Council 01/07/2008 B111 C, F Too much concrete/tarmac etc in the area so that water cannot get away. After heavy rain Old Basing and Lychpit Parish Council 01/07/2008 Surface water/sewage break out of polluted stream to the west which B112 A flows north to the Enbourne. Burghclere Ward 01/07/2008 B113 A Burst sewer under road (Harts Lane). Burghclere Ward 01/07/2008 Multiple ruptures of sewer/drain polluting stream & pond downstrem to B114 A the north and on one occasion field to the west. Burghclere Ward 01/07/2008 Sewage/drain rupture under Bishop's Green to Ecchinswell Road which B115 A polluted field to north east. Burghclere Ward 01/07/2008 Surface water flooding which made road impassable in 2007 and has B116 A previously almost done so on many occasions. Burghclere Ward 01/07/2008 sewer system incapacity/poor condition and infiltration by high B117 D groundwater 2-4 years St Marybourne Parish Council 01/07/2008 High groundwater plus backing up from Candover Stream causing B118 E internal and external flooding year 2000 flood Halcrow Flood Reports 00-01 21/01/2008 B119 E, F High groundwater, sometimes causing springs to flow 2000/01 and 2002/03 Halcrow Flood Reports 00-01 and 02-03 21/01/2008 B120 E, F High groundwater, sometimes causing springs to flow 2000/01 and 2002/03 Halcrow Flood Reports 00-01 and 02-03 21/01/2008 B120 D High groundwater levels, surface water flow and overtopping from river. approx 1 in 15 years Halcrow Flood Reports 00-01 21/01/2008 Reference Tile Source Of Flooding Occurrence Source of Outline Date Received B121 D Groundwater emerging Halcrow Flood Reports 00-01 21/01/2008 B122 D High groundwater/springflows overwhelming drainage. approx 1 in 50 years Halcrow Flood Reports 00-01 21/01/2008 B123 D high groundwater levels/surface water flow approx 1 in 15 years Halcrow Flood Reports 00-01 21/01/2008 B124 C Stratfield Saye Parish Council 23/11/2007 B125 C Stratfield Saye Parish Council 23/11/2007 B126 C Stratfield Saye Parish Council 23/11/2007 B127 C Stratfield Saye Parish Council 23/11/2007 B128 C Stratfield Saye Parish Council 23/11/2007 Runoff from fields floods Sheepwash Lane, and summer 2007 one house B129 B flooded, Wooton St Lawrence Parish Council 30/01/2008 Inadequate ditch/culvert maintance and high rainfall causes flooding of Recent high rainfall such as 20 B130 C, F sections of Newnham Road. July 07 Newnham Parish Council 30/01/2008 Inadequate ditch/culvert maintance and high rainfall causes flooding of Recent high rainfall such as 20 B131 C, F sections of Crown Lane. July 07 Newnham Parish Council 30/01/2008 Inadequate ditch/culvert maintance and high rainfall causes flooding of Recent high rainfall such as 20 B132 C, F sections of Old School Road. July 07 Newnham Parish Council 30/01/2008 Inadequate ditch/culvert maintance and high rainfall causes flooding of Recent high rainfall such as 20 B133 C, F sections of Blackstocks Lane. July 07 Newnham Parish Council 30/01/2008 Flooding in the dip on Vyne Road between Swingate Hill and Smitths B134 B, C Green Cottages Sherborne St John PC 30/01/2008 Flooding at entrance to Kiln Road from Elm Road, worsened by drain B135 B, C blockage with leaves and debris. Sherborne St John PC 30/01/2008 Surface water at north end of long field running from Gales Garage to B136 B, C Cranes Road. Sherborne St John PC 30/01/2008 B137 B, C, F Dip at Elm Bottom flooding possibly runoff from field. Sherborne St John PC 30/01/2008 Flooding at Cranes Road opposite the junction with Tyfield, worsened by B138 B, C drains blocked with debris. Sherborne St John PC 30/01/2008 Flooding at West End row of cottages opposite Mongers Yard layby, B139 B, C worsened by drains blocked by debris. Sherborne St John PC 30/01/2008 B140 A Sewerage capacity issues at Heatherwold Straight - Burghclere Burghclere PC 30/01/2008 Overflow from spring - needs connection to drains/access for drain B141 A, B clearance vehicle. Kingsclere PC 30/01/2008 B142 A, B Large pools of water form on the road surface and can linger for days. Kingsclere PC 30/01/2008 B143 A, B Flooding of George Street due to insufficient drainage capacity Kingsclere PC 30/01/2008 Regular flooding at The Hollies, at the Hatch, which is in the floodplain. Holding tanks installed last year prevented flooding last year, but risk B144 C, F remains if outflow channels downriver get blocked. Regularly until 2007 Mapledurwell & Up Nateley PC 30/01/2008 Pond flooded due to blocking of the drain under the road junction, impeding access to church. Allotments also flood if the drain under Frog B145 F Lane gets blocked. 2002 Mapledurwell & Up Nateley PC 30/01/2008 Surface water collects at the junction of Greywell Road with Tunworth B146 F Road. Causes problems for the 3 houses beyond the flood. After heavy rain Mapledurwell & Up Nateley PC 30/01/2008 B147 B, C Surface runoff/inadequate drainage After heavy rainfall Bramley PC 30/01/2008 B148 B, C Surface runoff/inadequate drainage After heavy rainfall Bramley PC 30/01/2008 B149 C Blocked ditches caused road to be flooded to a depth of approx 3 ft July 2007 Bramley PC 30/01/2008 B150 B, F Inadequate drainage, especially if ditch to Hardy Lane is blocked. After heavy rainfall Brookvale Community Association 31/01/2008 B151 B, C, F Flooding of King George V Playing Fields Brookvale Community Association 31/01/2008 B152 B, C, F Eastrop Park lower end car park is regularly flooded by raw sewage After heavy rain. Eastrop Ward 07/02/2008 Reference Tile Source Of Flooding Occurrence Source of Outline Date Received spilling out of sewer covers. Old Canal Place - Rosebanks - is regularly flooded by raw sewage spilling B153 B, C, F out of sewer covers. After heavy rainfall Eastrop Ward 07/02/2008 Poor drainage causes road to flood to a depth of 1 foot (the adjoining B154 B, C, F land can also be affected). Basingstoke & Deane Borough Council 07/02/2008 Insufficient path drainage (soakaways?) resulting in runoff through front B155 B, C, F gardens in Madeira Close. July 2007 Basingstoke & Deane Borough Council 07/02/2008 B156 B, C, F Falkland Road flooded - due to insufficient drainage? July 2007 Basingstoke & Deane Borough Council 07/02/2008 B157 B, C, F Insufficient soakaways leads to large waterlogged area. Basingstoke & Deane Borough Council 07/02/2008 B158 B, C, F Regularly Basingstoke & Deane Borough Council 07/02/2008 B159 B, C, F Bad flooding in Winklebury Way After heavy rain Basingstoke & Deane Borough Council 07/02/2008 B160 B, C, F Basingstoke & Deane Borough Council 07/02/2008 B161 B, F Basingstoke & Deane Borough Council 07/02/2008 B162 B, C, F Chineham PC 11/02/2008 B163 B, C, F Chineham PC 11/02/2008 B164 B, C, F Chineham PC 11/02/2008 B165 B, C Chineham PC 11/02/2008 B166 B, C Chineham PC 11/02/2008 B167 C, F Strings water meadow and neighbouring fields prone to minor flooding. Periods of high rainfall Newnham Parish Council 30/01/2008 B168 Overflow from sewage infrastructure February 2009 Burghclere Ward 20/02/2009

Note: This table is to be read in conjunction with Tiles A to F

Table 5: Areas Where Drainage Network Might Be At Full Capacity Source:

Reference Tile Comments FC01 B FC02 B, C, F FC03 B, C, F FC04 F FC05 F

Note: This table is to be read in conjunction with Tiles A to F

Table 7: Groundwater Flooding Incidents (Thames Region) Source: Environment Agency

ID Date Location Incident Grid Reference Aquifer Depth GW01 01/02/2001 Basingstoke Water under skirting boards SU593612 Bagshot Beds GW02 23/02/2001 Basingstoke Water in Public Subways SU6416552821 Uck-uncon 3-4m BGL Requested data related to GW03 13/03/2001 Basingstoke flooding SU6416552821 Drive ( flooded all winter ) now GW04 12/04/2001 Sherborne St. John subsiding SU6231955388 Ck/WRB spr GW05 18/05/2001 Buckskin Lane Reported Flooding to council SU6045251032 Chalk GW06 18/05/2001 Blackdown Close Reported Flooding to council SU6046751081 Chalk GW07 18/05/2001 Blackdown Close Reported Flooding to council SU6055651209 Chalk GW08 18/05/2001 Blackdown Close Reported Flooding to council SU6059451235 Chalk GW09 18/05/2001 Holyrood Court Reported Flooding to council SU6057551297 Chalk GW10 18/05/2001 Sperrin Close Reported Flooding to council SU6078451425 Chalk GW11 18/05/2001 Grampian Way Reported Flooding to council SU6068651298 Chalk GW12 18/05/2001 Worting Road Reported Flooding to council SU6091951715 Chalk Possibly blocked Cellar filling with water since drains or water pipe GW13 19/09/2001 Hook mid-Aug SU6984252800 London Clay leak. Bracklesham Beds, Water from base of bank before capped by Barton Beds Likely to be natural GW14 06/11/2001 Tadley house for past 9 months SU6057061109 uphill to S. groundwater seepage.

Note: This table is to be read in conjunction with Tiles A to F

Table 12: Flood Defences Source: Environment Agency

Defence Design Grid ID Asset Type Maintainer Asset Comments Asset Description Location Length Height Type Standard Bank Reference Twin concrete box culverts with trash screen has concrete pier head & wingwalls D/S culverted consists of 3x1m concrete Elm Hurst D1 channel local authority Culverted section through Elmhurst estate pipes with brick parapet Estate 78 1 minor 2 both SU6005561549 maintained All concrete conveyance D2 channel local authority Helps to convey flood water through Tadley channel 47.7 1 minor 2 both SU6012861542 Culverted channel 1x precast concrete box culvert 1x 1.2m concrete pipe set in brick head & wing walls L/B wingwall has abank of 4x150mm outfall pipes there is a trash screen over with steel walkway & culverted handrails D/S end consists of D3 channel local authority Conveyance culvert from brookside walk a single box culvert Brookside Walk 432 both SU6037061628 Raise concrete.wall, with masonry block lining. 7x raised defence flapped outfalls into base of Gutteridge Dr. D4 (man-made) local authority Wall act as top-over for flood waters into fsa durin flood events. channel. Tadley. 216.7 1.8 major left SU5945361420 Conc. channel wall with a earth embankment to the rear, HISTORY - Water has tracked raised defence Wall and ebmankment acting to contain water during flood along pathway into housing Gutteridge Rd, D5 (man-made) local authority events. estate area. Tadley. 241.9 2.8 major right SU5945761411 non-flood Raised embankment to form storage pond behind. 5m+ berm at defence ground level to permit flood flows. 0612222EC0101L02P D/S of Little D6 structure private Landuse: CD Embankment Knights Bridge 243.4 4 major 5 left SU5107663456 non-flood Raised embankment to form storage pond behind. 5m+ berm at defence ground level to permit flood flows. 0612222EC0101R02P D/S of Litle D7 structure private Landuse: CD Embankment Knights Bridge 243.4 2 major 5 right SU5109263444 non-flood A34. Enbourne defence RowSU 44355 D8 structure private A34 Road embankment 2m high. Road embankment 63440 152.4 2 minor 5 left SU4434163589 10m U/S from non-flood Wired gabion baskets forming bank protection for road A34 dual defence embankment. Willow have been planted to the front of the cariagewaySU D9 structure private baskets. Bank protection 44348 63476 8 2 minor right SU4429363458 20m U/S from A34 dual non-flood carriageway defence roadSU 44346 D10 structure private Concrete bagwork bank protection. Bank protection 63479 6.1 minor right SU4428363443 non-flood Ball Hill defence Concrete bagwork bank protection with concrete slab FarmSU 63698 D11 structure private foundation. Bank protection 63396 4.5 1 minor right SU4370663381 non-flood End of Knights D12 defence private Concrete bagwork bank protection. Bank protection Lane. 5m D/S 10.7 0.8 minor right SU4237063664 structure from footbridgeSU 42338 63678 non-flood defence Bridge House D13 structure private Bank protection made from sandbags bank protection New Farm 11 1 major 5 right SU4181963781 maintained Timber piling providing erosion protection to the bank. Brookbend D14 channel private 0612222FO0302R02P Landuse: CD Erosion defence Kennels 32.4 0 minor 5 right SU6386860864 non-flood defence D15 structure private wooden stakes as bank protection Bank protection Halls Farm 137.4 0 minor 5 right SU6292560769 non-flood Sheet metal piling protecting u/s end of island from erosion NW of defence from flow exiting the adjustable weir. LUB=CD Photo: view d/s Blacklands D16 structure private r/b Farm 7.7 0 major 5 left SU6790754767 300mm clay pipe culvert running from drainage ditch into main NW of culverted channel. Inadequate for high flow events - HYDRAULIC Blacklands D17 channel private PERFORMANCE? LUB=CD Photo: view d/s l/b Culvert Farm 109.6 0 major 5 right SU6814854685 non-flood defence Bramley D18 structure private Bag block wall between fence bridge and footbridge. Training Area 30.2 2 major 5 left SU6683258106 non-flood defence Upstream of D19 structure local authority Trench sheet walling to protect outside of bend. Bank protection Sherfield Staion 99.2 2 major 5 right SU6775358613 non-flood defence Bramley D20 structure private bag Block between fence 'bridgeand footbridge Training Area 30.2 2 major 5 right SU6683158104 non-flood defence Alongside D21 structure private Bagblock wall suporting bank to house. bank protection bridge cottage 100.8 2 minor 5 left SU6592358444 non-flood defence Basingstoke - D22 structure private Embankment well grown up with trees. Reading Railway 94.4 5 major 5 right SU6585558477 Immediately non-flood Brick wall as scour protection - now partly buried and upstream of defence ineffective. Donwstream end on bridge. Some underpinning Beaurepaire D23 structure private with concentration at downstream end. Driv 34.8 1 minor 5 left SU6363058768 non-flood SSP toe beneath brick wall. Supporting garden and outbuidling. Just upstream defence Upstream 7m or so porcupine block on SSP toe. Wall extended of A340 bridge D24 structure private up above ground level as a parapet. Bank protection pamber Gree 129.5 2 major 5 left SU6125258323 Just non-flood downstream of defence Steel pole spile and geotextile bank protection. Badly cut PA340 bridge. D25 structure private behind. Bank protection Pamboro 94.9 0 minor 5 right SU6127858308 maintained Environment D26 channel Agency Channel Maintenance 1969.2 0 minor 5 left SU6583859513 Bramley Lane maintained Environment to Strawberry D27 channel Agency Channel Maintenance Fields, Bramley 241.5 0 major 5 left SU6582259525 maintained Environment D28 channel Agency Channel Maintenance 1965.6 0 minor 5 right SU6583859509 culverted 700mm brick arch set into brick headwalls u/s and d/s with Mill Lane, D29 channel local authority painted tubular steel handrails. LUB=CD Photo: view d/s l/b Culvert Bramley 16.7 0 minor 5 right SU6734259233 maintained Environment Bramley Lane D30 channel Agency Channel Maintenance to Strawberry 244.4 minor 5 right SU6559259566 Fields, Bramley non-flood defence Rear of no. 7 D31 structure private Reinforced concrete block walling. includes bridge. Longridge Close 7.5 1 major 5 left SU6815858364 non-flood defence Rear of no. 8 D32 structure private Timber spicing with bridge Bank protection Longridge Close 11.3 0 major 5 left SU6817258357 Garden non-flood Fieldways. defence Sherfield. D33 structure private Reinforced blockwork retaining wall No fence or rail on top. Loddon 35.2 1 major 5 left SU6774358424 non-flood defence Rear of no. 9 D34 structure private ~5m timber spilling and 15m stone walling. includes a bridge. Longridge Close 14.7 1 major 5 left SU6819058348 non-flood defence Timber boarding bank protection retained by timber stakes. D35 structure private LUB=AB Photo: view u/s r/b W. of Lyde Mill 17.2 0 major 5 left SU6954654209 non-flood defence Timber boarding bank protection retained by timber stakes. D36 structure private LUB=AB Photo: view d/s l/b W. of Lyde Mill 7.8 0 major 5 right SU6955154207 non-flood defence Timber board bank protection retained by wooden stakes in D37 structure private order to protect natural bank. LUB=AB Photo: view u/s r/b Ladylands 29.8 0 major 5 left SU6732960155 Concrete pipe culvert set into small brick headwall carrying culverted drainage channel underneath Folly Lane. LUB=CD Photo: view D38 channel local authority d/s l/b Folly Lane 19.8 0 minor 5 right SU6662160001 Concrete box culvert (700mm wide) carrying channel under Mill culverted Lane. Headwall consists of concrete bagwork. set into natural north of Pizzie D39 channel local authority bank. LUB=CD Photo: view u/s r/b Green 25.3 0 minor 5 right SU6733060145 Concrete box culvert (700mm wide) with concrete bagwork culverted headwalls set into natural bank. with tubular steel handrailling. N. of Tubbs D40 channel local authority LUB=CD Photo: view d/s l/b Copse 20.9 0 minor 5 right SU6766859945 non-flood defence Timber board bank protection retained by wooden stakes in D41 structure private order to protect natural bank. LUB=AB Photo: view u/s l/b Ladylands 29.4 0 major 5 right SU6732760153 Concrete pipe (300mm dia) culvert running underneath stratfield culverted saye lane carrying drainage ditch underneath the road. LUB=CD Stratfield Saye D42 channel local authority Photo: view d/s l/b Culvert Lane 22.4 0 minor 5 right SU6629660238 culverted north of Hale D43 channel private Halcrow failed to gain access on two occasions Farm 20.5 0 minor 5 right SU6904554963 600mm dia concrete pipe set into natural bank carring channel culverted underneath the A33. Flow moving freely through the culkvert. N. of Floods D44 channel local authority LUB=CD Photo: view d/s r/b Culvert Farm 17.8 0 minor 5 right SU6845458584 Concrete pipe culvert carrying ditch alongside Hartley Lane. A culverted series of prefab concrete pipes of 600mm dia. LUB=AB Photo: S. of Rose D45 channel local authority view d.s r/b Culvert Cottage 85 0 major 5 right SU6857658693 Concrete pipe culvert carrying ditch alongside Hartley Lane. A culverted series of concrete piping joined to create a culvert of approx D46 channel local authority 30m with a diameter of 600mm. LUB=AB Photo: view d/s l/b Culvert W. of Harvey's 28.4 0 major 5 right SU6874658675 Eastrop roundaboutSU6 culverted 410752362, D47 channel local authority Culvert depth 5 -6 metres below surface. Unable to inspect. Culvert Basingstoke. 602 major 5 right SU6411052368 D48 non-flood local authority 4 to 5 metres deep over whole length Culvert Lower Brook 946.4 minor 5 both SU6259852189 defence Street to structure roundaboutSU6 271452202 non-flood GRASS EMBANKMENT (DENOTED BY LINE OF TREES defence IN PHOTO) RAISED ABOVE FLOODPLAIN BE 2 Bell's Water D49 structure private METERS. LUB=CD PHOTO:VIEW D/S EMBANKMENT Copse 499.1 0 minor 5 left SU6298058899 BRICK CULVERT UNDER ROAD. CONCRETE SUPPORT AT ROOF OF CULVERT. TUBULAR STEEL HANDRAILS. COULD BE MAPPED AS A STRUCTURE (BUT PREVIOUS LENGTH GIVEN AS = 20m). WIDTH OF CHANNEL= culverted 2.495m HEIGHT TO SOFFIT=1.1m // LUB=AB BOARS D50 channel private PHOTO:VIEW D/S CULVERT BRIDGE 29 0 minor 5 right SU6304659220 non-flood defence Brick wall adjacent to weir and footbridge. LUB=CD Photo: Upper D51 structure private view u/s r/b Tumbling Bay 26.1 0 major 5 left SU7007461281 non-flood defence 4m deep sheet metal piling with timber toeboarding. Installed in Lower D52 structure private 1988. LUB=CD Photo: view u/s Tumbling Bay 69.5 0 major 5 right SU7051962033 non-flood defence Geotextile bank protection retained by metal poles the length of E. of Turgis D53 structure private the defence. LUB=CD Photo: view d/s r/b Court Farm 48.1 0 major 5 right SU6884460139 non-flood Geotextile bank protection held in place by steel poles. defence Protecting bank from water exiting weir. LUB=CD Photo: view N. of Turgis D54 structure private r/b Court Farm 9 0 major 5 left SU6914360653 non-flood Geotextile bank protection held in place by steel poles. defence Protecting bank from water exiting weir. LUB=CD Photo: view N. of Turgis D55 structure private l/b Court Farm 15 0 major 5 right SU6914760665 non-flood Brick retaining wall. Serious brick and mortar loss. Failure of defence structure will most probably occur in the next high flow event. Turgis Court D56 structure private LUB=AB Photo: view u/s r/b Farm 11.2 0 major 5 right SU6900160080 non-flood defence Timber toe board bank protection retained by timber stakes. Turgis Court D57 structure private LUB=AB Photo: view d/s Farm 38.9 0 major 5 right SU6899760069 non-flood Corrugated iron sheets downstream of bridge and adjacent to defence disused river control structure. Holes rusted through sheets in N. of The D58 structure private places. LUB=CD Photo: view d/s Fishery 17.4 0 major 5 right SU6857059535 non-flood defence Corrugated sheets retained by wooden stakes - the sheets are D59 structure private rusting and the staked are rotting. LUB=AB Photo: view d/s l/b The Fishery 28.2 0 major 5 right SU6851059490 non-flood Brickwork bank protection adjacent to fishery cottages. Appears defence to have been built recently. both mortar and brickwork in good D60 structure private condition. LUB=AB Photo: view d/s l/b The Fishery 20.6 0 major 5 right SU6848559478 non-flood defence Corrugated iron sheets retained by wooden stakes. LUB=CD D61 structure private Photo: view d/s l/b The Fishery 12.5 0 major 5 right SU6844659455 Stone mill culvert beneath visitor center. 2 bridgepipes cross U/S. No debris in trash screen Well maintained. Fair amount of silt build up around entrance and reed growth. GANTRY with culverted TRASH grill on US & DS of Mill Bldn. Stonework throughout. under D62 channel private Volunteer Culvert Under Longbridge Mill Longbridge Mill 28.7 0 major 5 right SU6835558184 Culvert running underneath A33. Diameter of approximatly culverted 1000mm. with concrete bagwork headwalls. LUB=CD Photo: W. of Floods D63 channel local authority view u/s r/b Farm 27.4 0 major 5 right SU6841058560 D64 maintained Environment Channel Maintenance 2550.2 0 minor 5 left SU6522952603 channel Agency non-flood defence Timber sleepers with aluminium channel spiling. As bank Beneath railway D65 structure private protection to ralway stream only. Bank protection bridge 61.2 1 minor 5 left SU6612352949 non-flood defence Embankment carries alloy track #3.0m wide. track to watercress Old watercress D66 structure private farm round it. end of lake. Steep sided. but trees growing in it beds 44.7 2 minor 5 left SU6548152642 maintained Environment D67 channel Agency Channel Maintenance 2545.2 0 minor 5 right SU6597552737 non-flood Wier muribund. Few scraps of timber remain. Owner intends to Garden no. 71. defence remove. Short length of bank protection put in because of scour The Street. Old D68 structure private around wier. no longer feature code 31. Bank protection Basing 29.4 1 minor 5 right SU6653153349 Brick arch culvert ~2m span. Wing walls for 5m downstream locked with gravel. Unable to inspect D/s end due to summer non-flood vegetation. Culvert entrance arch appears clear although slightly defence buried by gravel bed. Brickwork is old but generally sound. GRANGE D69 structure private LUB=AB Culvert - not on main river FARM 62.4 0 major 5 right SU6608252822 Railway non-flood Embankment defence north of Basing D70 structure private Well grown up with trees Railway Embankment House 1005.2 15 major 5 right SU6570452902 non-flood Garden of no. defence 19. Paddock D71 structure private Low brick wall to edge of lawn. Fields 39.7 1 minor 5 right SU6657353450 maintained D72 channel private Channel Maintenance 427 0 minor 5 left SU6615953028 maintained D73 channel private Channel Maintenance 477.4 0 minor 5 right SU6615853025 maintained D74 channel private Channel Maintenance 293.7 0 minor 5 left SU6616453066 maintained D75 channel private Channel Maintenance 277.6 0 minor 5 right SU6616453061 maintained D76 channel private Channel Maintenance 241.6 0 minor 5 left SU6579752627 maintained D77 channel private Channel Maintenance 248.1 0 minor 5 right SU6579552622 maintained D78 channel private Channel Maintenance 388.9 0 minor 5 left SU6523652597 maintained D79 channel private Channel Maintenance 394.2 0 minor 5 right SU6523052592 Concrete steel culvert 1.5m in height and 2m in width. There is a Eastrop steel trash screen at the U/S end. The D/S ends looks like it ParkSU6449552 culverted may have had a sluice at some point in the past. Culvert runs 324, D80 channel local authority under lake. Box shape culvert Basingstoke. 319.4 1.5 major 5 both SU6478852372 maintained Timber post bank protection running alongside the natural bank. Eastrop, D81 channel local authority The wall is 1m in height. There is no raised height. Bank Protection. Basingstoke. 168.1 0 minor 5 left SU6494552414 Basinstoke maintained Environment Interchange D82 channel Agency Channel Maintenance Area 34.1 minor 5 left SU6498452464 Timber bank protection lining natural bank. The wall is made up maintained of many timber vertical posts. The bank protection is approx. Estrop Park, D83 channel local authority 0.7m in height. Bank protection. Basingstoke. 304.9 0 minor 5 left SU6449252324 maintained Environment Basinstoke D84 channel Agency Channel Maintenance Interchange 105.8 minor 5 left SU6507552498 Area Basingstoke maintained Environment Interchange D85 channel Agency Channel Maintenance Area 29 minor 5 right SU6498852464 Precast concrete pipe culvert running under Ringway. The pipe culverted is 1m in diameter. At the U/S end there is a trash screen and A339, D86 channel local authority brickwork wingwalls. Pipe culvert Basingstoke 63.2 0 major 5 right SU6498552465 maintained Timber post bank protection running alongside the natural bank. Eastrop, D87 channel local authority The wall is 1m in height. There is no raised height. Bank protection. Basingstoke. 174 1 minor 5 right SU6494952412 Timber bank protection lining natural bank. The wall is made up maintained of many timber vertical posts. The bank protection is approx. Eastrop Park, D88 channel local authority 0.7m in height. Bank protection. Basingstoke 308.7 0 minor 5 right SU6449152320 A3010, Church culverted CREATED AS PART OF DESK EXERCISE. NEEDS Hill Way East, D89 channel local authority ASSET INSPECTION. Culvert Basingstoke 66.9 major 5 right SU6516952548 A339, Ringway culverted CREATED AS PART OF DESK EXERCISE, ASSET East, D90 channel local authority INSPECTION REQUIRED. Culvert Basingstoke 65.6 minor 5 right SU6501152481 Basinstoke maintained Environment Interchange D91 channel Agency Channel Maintenance Area 106.8 minor 5 right SU6507652494 Park area & below culverted housingSU6245 D92 channel local authority Culvert 452136 330.5 minor 5 both SU6245152140 Rear of culverted gardensSU6287 D93 channel local authority Culvert 052187 189.8 minor 5 both SU6284952187 culverted CONCRETE PIPE IN POURED CONC. HEADWALLS SET THORNEYCR D94 channel local authority IN RAISED ROAD BANKS CULVERT UNDER A340 OFT R-BOUT 57.9 5 both SU6235652111 culverted LOWER D95 channel local authority CAST CONC ,BRICK HEADWALL AT D/S END CULVERT BROOK RD 49.7 minor 5 both SU6311052230 maintained Environment Southend Road, D96 channel Agency Channel Maintenance Basingstoke 207.8 minor 5 left SU6315852237 Lower Brook maintained Environment Street, D97 channel Agency Channel Maintenance Basinstoke 83.5 minor 5 left SU6303252210 maintained Environment George Street, D98 channel Agency Channel Maintenance Basingstoke 96.5 minor 5 left SU6275752160 maintained Environment A340, D99 channel Agency Channel Maintenance Basinstoke 46.1 minor 5 left SU6240652140 maintained Environment B3400, D100 channel Agency Channel Maintenance Basingstoke 363.3 minor 5 left SU6201352064 maintained Environment Southend Road, D101 channel Agency Channel Maintenance Basinstoke 208.5 minor 5 right SU6315852233 Lower Brook maintained Environment Street, D102 channel Agency Channel Maintenance Basinstoke 84.4 5 right SU6303252207 maintained Environment George Street, D103 channel Agency Channel Maintenance Basinstoke 97.8 minor 5 right SU6275952158 maintained Environment A340, D104 channel Agency Channel Maintenance Basingstoke 43.7 minor 5 right SU6240852138 maintained Environment B3400, D105 channel Agency Channel Maintenance Basingstoke 361.9 minor 5 right SU6201552060 non-flood defence Red brick wall bank protection d/s of Hartley Mill. LUB=CD D106 structure private PHOTO:VIEW D/S BANK PROTECTION Hartley Mill 12.6 0 major 5 left SU6965857207 Mill culvert. which includes: brick arch bridge at d/s. allowing access to private residence; gravel surface; some erosion to culverted brickwork. At u/s end is sluice house. which shows more serious Hartley Wespall D107 channel private erosion to brickwork. LUB=CD PHOTO:VIEW U/S CULVERT Mill 21.6 0 minor 5 right SU6966457188 non-flood defence Red brick wall bank protection d/s of Hartley Mill. LUB=CD D108 structure private PHOTO:VIEW D/S BANK PROTECTION Hartley Mill 12.5 0 major 5 right SU6966557209 non-flood Concrete bagwork bank protection d/s of sluice at rear of defence Hartley Mill; mostly submerged in high flow. LUB=CD D109 structure private PHOTO:VIEW U/S BANK PROTECTION Hartley Mill 25.8 0 major 5 left SU6964457158 non-flood defence Upright timber stakes along r/b. d/s of sluice; retians graden D110 structure private area. Timbers are rotten. LUB=CD PHOTO:VIEW D/S BANK PROTECTION Hartley Mill 16 0 major 5 right SU6965557162 non-flood Timber pile bank protection which appear to be have been defence recently installed. Very good condition. LUB=AB Photo: view D111 structure private u/s l/b Lyde Mill 12.2 0 major 5 left SU6957054181 non-flood defence Concrete bagwork bank protection set against natural bank. Water End D112 structure private LUB=AB Photo: view d/s r/b Residential Park 16.8 0 major 5 left SU6942853181 non-flood Rock bank protection against natural bank. u/s from concrete defence bagwork protection. adjacent to mobile caravan. LUB=AB Water End D113 structure private Photo: view d/s r/b Residential Park 19.2 0 major 5 left SU6941553167 non-flood Corrugated iron sheets retained by metal poles. which is rusting. defence and may need replacement in the near future. LUB=AB Photo: W. of Lyde Mill D114 structure private view d/s l/b House 24.6 0 major 5 right SU6957854223 non-flood Timber pile bank protection which appear to be have been defence recently installed. Very good condition. LUB=AB Photo: view D115 structure private u/s r/b Lyde Mill 44.4 0 major 5 right SU6958254184 Brickwork culvert dia approx 1200mm. Brickwork wingwalls are subsiding as they are being undermined by channel flow. culverted Otherwise brickwork and mortar in fair condition. LUB=CD S.E. of Golds D116 channel private Photo: view u/s r/b Farm 81.2 0 minor 5 right SU6961853438 Railwy non-flood Embankment defence north of Water D117 structure private Well grown up with trees Embankment End 1214.5 15 major 5 right SU6895453351 Timber toe board bank protection retained by steel poles. non-flood Missing and misaligned boards. not providing any bank defence protection. Advised that renewal is to take place during the Andwell Mill D118 structure private summer months. LUB=AB Photo: view d/s r/b Trout Farm 49.3 0 major 5 left SU6914452853 Timber toe board bank protection retained by steel poles. non-flood Missing and misaligned boards. not providing any bank defence protection. Advised that renewal is to take place during the Andwell Mill D119 structure private summer months. LUB=AB Photo: view d/s r/b Trout Farm 15.5 0 major 5 left SU6913752792 non-flood Timber toeboard bank protection installed in the last couple of defence years around the outside of the mill pond. LUB=AB Photo: D120 structure private view u/s l/b Andwell Mill 20.1 0 major 5 left SU6912652725 non-flood Brickwork bank protection. Appears to have been recently defence installed. no missing brickwork and mortar is in good conidition. Lyde Boarding D121 structure private LUB=AB Photo: view d/s r/b Kennels 29.3 0 major 5 left SU6766452158 D122 non-flood private Timber toe board bank protection retained by timber stakes. The Hatch 48.9 0 major 5 left SU6759252111 defence Missing and rotting in many places. with natural bank proteuding structure into channel due to bank protection failure. LUB=AB Photo: view d/s l/b Triple arch culverts (1000mm dia) running underneath A30. culverted Brick headwalling u/s and d/s with brick parapets. Tarmac road S. of Caravan D123 channel local authority deck. LUB=AB Photo: view u/s l/b Park 45 0 major 5 right SU6939253139 1000mm dia concrete construction culvert running underneath culverted greywell road. Concrete wingwalling with square inlet on u/s D124 channel local authority r/b wingwall for side ditch. LUB=CD Photo: view d/s l/b Greywell Road 33.2 0 minor 5 right SU6773052275 Timber toe board bank protection retained by steel poles. non-flood Missing and misaligned boards. not providing any bank defence protection. Advised that renewal is to take place during the Andwell Mill D125 structure private summer months. LUB=AB Photo: view d/s r/b Trout Farm 28.6 0 major 5 right SU6914252793 non-flood Brickwork bank protection adjacent to Andwell Mill. In average defence condition. No significant mortar loss and brickwork is intact. D126 structure private LUB=AB Photo: view d/s l/b Andwell Mill 15.5 0 major 5 right SU6914152734 non-flood Timber toeboard bank protection installed in the last couple of defence years around the outside of the mill pond. LUB=AB Photo: D127 structure private view u/s l/b Andwell Mill 70.1 0 major 5 right SU6913552719 Timber toe board bank protection retained by timber stakes. non-flood Missing and rotting in many places. with natural bank proteuding defence into channel due to bank protection failure. LUB=AB Photo: D128 structure private view d/s l/b The Hatch 46.9 0 major 5 right SU6759352109 LENGTH NOT KNOWN DIMENSIONS NOT KNOWN WIDTH BETWEEN ABUTS = 3.12m NUMBER OF SPANS culverted = 1 // RC pipe in concrete headwall. // Close inspection not CULVERT D129 channel private possible because of Watercres beds. 857 M3 71.80Q NO.6 73.2 2 major 5 right SU6889352370 non-flood defence D130 structure private Embankment well grown up M3 motorway 191.3 2 major 5 right SU6873752273 maintained Environment D131 channel Agency Channel Maintenance 1550.7 0 minor 5 left SU6663755302 Tessellating block Wall - Concrete cap & body. Some growth Upstream of maintained through joints and at cap. Joints are cracking and dry - A33 culvert - D132 channel local authority repointing may be required. LUB=AB PHOTO:VIEW D/S Engineered Channel Chineham 226.1 minor 5 left SU6654255454 non-flood Alongside road defence to sewerage D133 structure local authority Concrete bagwork wall Bank Protection treatment wo 159.5 2 major 5 left SU6667655288 raised defence Earth embankment for flood storage area. Embankment D/S U/S from A33, D134 (man-made) local authority limit is at the brick housing for the siphons. FSA Embankment. Chineham. 195 major 25 left SU6658555489 Upstream of Tessellating block Wall - Concrete cap & body. Joints cracked Thornhill Way maintained by vegetation and weathering. Areas of total collapse exposing Bridge - D135 channel local authority natural bank. LUB=AB PHOTO:VIEW D/S Engineered Channel Chineham 759.9 minor 5 left SU6590255747 maintained Environment D136 channel Agency Channel Maintenance 1560.7 0 minor 5 right SU6663455298 non-flood Alongside road defence to sewerage D137 structure local authority Concrete bagwork Bank Protection treatment wo 124.5 2 major 5 right SU6670555298 3m wide by 1m high precast concrete box culvert, with 5m wide brick headwalls. Culvert is 6m wide at U/S extent where the culvert incorporates 2 x 0.8m pipes with bell mouths within A33, Chineham. culverted screens as flood overflows. Banks lined with concrete/stone BOUNDARY D138 channel private U/S. Culvert.249 249 28.6 1 major 5 right SU6661655320 non-flood Just upstream defence Concrete box culvert approx 2.5m x 2m. Short bagwork wing of Basingstoke D139 structure local authority walls up & down stream ends Culvert - not FRM sewerage t 20.5 2 major 5 right SU6717555309 raised defence Earth embankment for flood storage area. Embankment D/S U/S from A33, D140 (man-made) local authority limit is at the brick housing for the siphons. FSA Embankment. Chineham. 182.6 major 25 right SU6661555318 raised defence Thornhill Way, D141 (man-made) local authority Earth embankment for flood storage area. FSA Embankment. Chineham. 95.6 major 25 right SU6652755449 Upstream of Tessellating block Wall - Concrete cap & body. Joints cracked Thornhill Way maintained by vegetation and weathering. Areas of total collapse exposing Bridge, D142 channel local authority natural bank. LUB=AB PHOTO:VIEW D/S Engineered Channel Chineham 755.7 minor 5 right SU6590255742 Brick arch culvert- arch ~4.0m. Not a CONFINED SPACE - Concrete walkway above bank protection on both sides - not non-flood footpath. wire fence prevents public access on d/s side. Channel Underneath defence lining continuous through culvert to far side concrete benching Railway Culvert - not on main Basingstoke - D143 structure private ~1.0m wide river Reading railway 53.5 4 major 5 right SU6556055656 non-flood defence Basingstoke - D144 structure private Embankment well grown up with trees. Embankment Reading railway 398.2 8 major 5 right SU6569155752 Tessellating block Wall - Concrete cap & body. Some growth Upstream of maintained through joints and at cap. Joints are cracking and dry - A33 culvert - D145 channel local authority repointing may be required. LUB=AB PHOTO:VIEW D/S Engineered Channel Chineham 235.5 0.4 major 5 right SU6653655453 non-flood defence Bagwork bank protection. by fishing area. l/b. LUB=CD E of Blacklands D146 structure private PHOTO:VIEW D/S BANK PROTECTION Fm 56 0 major 5 left SU6768154871 non-flood defence Bagwork bank protection. by fishing area. r/b. LUB=CD E of Blacklands D147 structure private PHOTO:VIEW U/S BANK PROTECTION Fm 26.5 0 major 5 right SU6771654842 Outfall with 750 mm diameter set into concrete structure which culverted also carries rectangluar outfall from sewerage plant. LUB=CD E. of Sewerage D148 channel local authority Photo: view u/s r/b Plant 245.3 0 major 5 right SU6804655204 Circular concrete culvert pipe in concrete head- & exit-wall. Debris caught d/s. gate on r/b. timber handrails. NB: has been culverted logged as defence culvert 37; should be structure culvert 35. north east of D149 channel private LUB=CD PHOTO:VIEW D/S CULVERT Deanland Farm 16.6 0 major 5 right SU6956154617 maintained Environment Photo 066. Design standard source: 2000/01 Flooding Report Chilton Manor D150 channel Agency Candover (Halcrow, 2001) Natural bank Farm 1431 50 left SU5942440231 maintained Environment Photo 066. Design standard source: 2000/01 Flooding Report Chilton Manor D151 channel Agency Candover (Halcrow, 2001) Natural Bank Farm 1424 50 right SU5942240241 natural river bank and channel. Channel side protected with d/s raised defence Environment vertical sheets of corrugated metal/Design standard source: corrugated steel bank Hurstbourne D152 (man-made) Agency Engineering Judgement (Mike Mullins). protection Priors 208.2 10 left SU4420846041 manmade channel for Saw Mill. 4-5 years ago Mr Michael added a few breeze blocks to RHS as the water levels were getting Saw Mill House, maintained Environment dangerously high. Design standard source: Engineering 2km u/s D153 channel Agency Judgement (Mike Mullins). lined mill channel Hurstbourne 93.3 10 left SU4332047687 u/s mill river ponds which helps maintain head in times of low u/s Saw Mill maintained Environment flow.Design standard source: Engineering Judgement (Mike House, 2km u/s D154 channel Agency Mullins). mill pond, masonry lined Hurstbourne 113.9 10 left SU4328347772 manmade channel for Saw Mill. 4-5 years ago Mr Michael added Saw Mill House, a few breeze blocks to RHS as the water klevels were getting 2km u/s maintained Environment dangerously high.Design standard source: Engineering Hurstbourne D155 channel Agency Judgement (Mike Mullins). liined mill channel Prior 93.8 10 right SU4331047688 D156 maintained Environment u/s of Mill River Poinds which helps maintain head in times of Mill Pond, masonry lined u/s Saw mill 110.8 10 right SU4327347771 channel Agency low flow.Design standard source: Engineering Judgement (Mike House, 2km u/s Mullins). Hurstbourne brick arched culvert (2/3 circle) 5m wide x 5m high. Upstream railway, 1.75km culverted Environment end of culvert is rectangular shaped (10m length)Design culvert under railway d/s St Mary D157 channel Agency standard source: Engineering Judgement (Mike Mullins). embankment Bourne 148.5 10 left SU4274448956 concrete lined channel approx 4m wide. Walls approx 0.75m 200m u/s of maintained Environment high. BElieved to be constructed in mid 1980.Design standard railway, 1.7km D158 channel Agency source: Engineering Judgement (Mike Mullins). concrete lined section of river d/s St Mary 148.9 major 10 left SU4276248998 maintained Environment river channel approx 7m wide.Design standard source: 1km d/s of St D159 channel Agency Engineering Judgement (Mike Mullins). natural defence Mary Borne 817.2 major 10 left SU4225650184 channel running through resedential area on L bank and lakeside maintained Environment on R bank.Design standard source: Engineering Judgement D160 channel Agency (Mike Mullins). various revetments St Mary Borne 504.4 major 10 left SU4207750563 u/s of Spring maintained Environment Hill, St MAry D161 channel Agency natural channel.Design standard source: Engineering Judgement natural defence Borne 496.5 major 10 left SU4167750811 natural river channel approximately 4m wide. NAtural upstream maintained Environment vegetation, mainly grass along banks.Design standard source: Baptist hill, NW D162 channel Agency Engineering Judgement (Mike Mullins). natural defence St Mary Bourne 1164 major 10 left SU4079251429 channel approx 4m wide, pasture along L bank, tall hedge along gangbridge, maintained Environment R bank seperates channel from road to SStoke.Design standard 0.75km d/s D163 channel Agency source: Engineering Judgement (Mike Mullins). natural defence from Stoke 324.9 10 left SU4054651625 natural river channel, vegetation and trees along both banks. maintained Environment trees overhang channel. Channel width approx 10m.Design 0.4km d/s from D164 channel Agency standard source: Engineering Judgement (Mike Mullins). natural defence Stoke 378.8 10 left SU4031151883 river channel approx 4m wide with dense vegetation along both banks and significant weed growth within the channel. Private maintained Environment dwellings close to channel along both banks. Design standard u/s of Old Post D165 channel Agency source: Engineering Judgement (Mike Mullins). natural defence Office, Stoke 136.5 10 left SU4031151883 river channel approx 4-5m, vegetation along both banks. Some maintained Environment trees along part of defence.Design standard source: Engineering Valley Farm, D166 channel Agency Judgement (Mike Mullins). natural defence Stoke 401 major 10 left SU4006152268 Bury Hill Farm, maintained Environment natural channelDesign standard source: Engineering Judgement 0.5km NW of D167 channel Agency (Mike Mullins). natural defence Stoke 734.7 major 10 left SU3944552472 maintained Environment natural channel, steep sides.Design standard source: Engineering Store Lane, 1km D168 channel Agency Judgement (Mike Mullins). natural defence u/s of Stoke 1382.8 major 10 left SU3852052925 brick arched culvert (2/.3 circle), 5m x 5m high. Upstream end railway, 1.75km culverted Environment of culvert is rectangular shaped (10m length).Design standard culvert under railway d/s St Mary D169 channel Agency source: Engineering Judgement (Mike Mullins). embankment Borne 154.6 10 right SU4279748834 cincrete lined channel approx 4m wide. Walls approx 0.75m 200m u/s of maintained Environment high. Believed to be constructed in mid 1980.Design standard railway, 1.7km D170 channel Agency source: Engineering Judgement (Mike Mullins). concrete lined section of river. d/s St MAry 151.3 major 10 right SU4275248999 maintained Environment river channel approx 7m wide.Design standard source: 1km d/s of St D171 channel Agency Engineering Judgement (Mike Mullins). natural defence Mary Borne 822.5 major 10 right SU4253749511 channel running through residential area on L bank and lakeside maintained Environment on R bank.Design standard source: Engineering Judgement D172 channel Agency (Mike Mullins). natural defence St Mary Borne 512.6 major 10 right SU4225050178 u/s of Spring maintained Environment Hill, St Mary D173 channel Agency natural channel. natural defence Borne 483.1 major 10 right SU4206850560 natural river channel approx 4m wide. Natural vegettion, mainly upstream, maintained Environment grass along banks.Design standard source: Engineering Baptist Hill, D174 channel Agency Judgement (Mike Mullins). natural defence NW St Mary 1170.5 major 10 right SU4167350804 Borne natural river channel, vegetation and trees along both abnks, maintained Environment trees overhang channel. Channel width approx 10m.Design 0.4km d/s from D175 channel Agency standard source: Engineering Judgement (Mike Mullins). natural defence Stoke 373.3 major 10 right SU4054251619 river channel approx 4m wide with dense vegetation along both banks and significant weed growth within the channel. Private maintained Environment dwellings close to channel along both banks.Design standard u/s of Old Post D176 channel Agency source: Engineering Judgement (Mike Mullins). natural defence Office, Stoke 133.5 major 10 right SU4030351880 river channel approx 4-5m, vegetation along both banks. Some maintained Environment trees along part of defence.Design standard source: Engineering Valley Farm, D177 channel Agency Judgement (Mike Mullins). natural defence Stoke 408.4 10 right SU4029552014 Burry Hill maintained Environment natural channel.Design standard source: Engineering Judgement Farm, 0.5km D178 channel Agency (Mike Mullins). natural defence NW of Stoke 726.1 10 right SU4005752262 Strore Lane, maintained Environment natural channel, steep sides.Design standard source: Engineering 1km u/s from D179 channel Agency Judgement (Mike Mullins). natural defence Stoke 1413.6 10 right SU3945352467 revetment non-continuous, overall mainly stone and brickwork. maintained Environment Some short sections of timber and natural channel.Design silkmill, D180 channel Agency standard source: Engineering Judgement (Mike Mullins). masonry revetments Whitchurch 698.6 10 left SU4670348078 revetment non-continuous, overall mainly stone and brickwork. maintained Environment Some short section of timber and natural channel.Design silkmill, D181 channel Agency standard source: Engineering Judgement (Mike Mullins). masonry revetments Whitchurch 772.6 10 right SU4616947862 raised defence Environment concrete revetment halfway, then naturalDesign standard source: manmade defence with parts D182 (man-made) Agency Engineering Judgement (Mike Mullins). natural Whitchurch 74.3 10 left SU4647248107 raised defence Environment timber revetmenr half way, the rest naturalDesign standard manmade defence with parts D183 (man-made) Agency source: Engineering Judgement (Mike Mullins). natural Whitchurch 73.5 10 right SU4646548100 d/s of WInchester maintained channel definitionDesign standard source: Engineering Road Bridge, D184 channel private Judgement (Mike Mullins). stone revetment Whitchurch 490.3 10 right SU4629447895 new masaonary wall at mill carpark. One 0.15m outfall (spring) raised defence Environment plus 5 drainage pipes 0.1m in diameter.Design standard source: D185 (man-made) Agency Engineering Judgement (Mike Mullins). Masonary wall Laverstoke Mill 82.7 10 left SU4917148660 1.2m high concrete wall. Face protected by steel sheets for final u/s mill raised defence Environment 20m.Design standard source: Engineering Judgement (Mike buildings, D186 (man-made) Agency Mullins). concrete wall Laverstoke. 54.9 10 left SU4925348676 70m high wall/building. Concrete rendered base with masonary raised defence Environment mill buildings with overhanging footpath for 6m at u/s end. Laverstoke Mill, D187 (man-made) Agency Design standard source: Engineering Judgement (Mike Mullins). mill buildings offices Laverstoke. 87.7 10 right SU4916548670 concrete vesticle side wall. 5 drainage outfalls also u/s mill raised defence Environment present.Design standard source: Engineering Judgement (Mike buildings, D188 (man-made) Agency Mullins). concrete wall Laverstoke. 54 10 right SU4925148681 raised defence Environment masonry block bank with grassed garden.Design standard Southington D189 (man-made) Agency source: Engineering Judgement (Mike Mullins). masonry lined channel Mill, Lynch 283.3 10 right SU5041549695 concrete vertical wall, masonry in parts, RSJ supported at u/s d/s end of Mill raised defence Environment end.Design standard source: Engineering Judgement (Mike buildings, D190 (man-made) Agency Mullins). concrete wall Laverstoke 81.1 10 left SU4916048696 stream culverted under road and mill (twin 2000x300 and Town Mill, raised defence Environment 1000x300).Design standard source: Engineering Judgement culvert under mill and road Kingsclere Rd, D191 (man-made) Agency (Mike Mullins). bridge OVerton 48.5 10 right SU5152249759

Note: This table is to be read in conjunction with Tiles A to F

Table 12: Watercourse Structures Source: Environment Agency

ID Maintainer Description Comments Location Grid Reference Height Width S1 private Concrete outfall with trash screen Drainage outfall from unknown source SU6082961605 0.5 1.6m concrete outfall pipe outfalls into inspection chamber with twin hinged trash screensAsset has 3x 1.8m high x4m S2 private long concrete flow deflection plates Outfall from unknown source has an equall amount of flow as the main river SU6083261600 1.6 Concrete. floom with trash screen Structure controlls water velocity through channeled floom way, forcing back -up flood S3 local authority us,central throttle plate and grill ds. water into FSA. Tadley. SU5965561514 3 1 Trashscreen us of outfall / valve/weir S4 local authority complex included. Asset controlls flow/catches debris from watercourse. Elmshust Rd., Tadley. SU5991661536 0.8 2 Overfall weir u/s of bridge. Gates removed and replaced with STOPLOGS. S5 private Weir 0612222EC0101R02002P Landuse: CD D/S of Little Knights bridge SU5094663345 0.5 2 Footbridge.8m wide constructed of steel beams with concrete abutments and timber plank decking over. Has tubular steel handrails u/s and d/s. 0612222EN0202R01001P Landuse: S6 private Footbridge CD Note - private SU5422063693 2.5 8 Concrete fixed crest overfall weir 7m width. with 0.7m drop. Has concrete WING walls running 1.5m u/s and 3m d/s. There is no walkway over. The water flows over 2 steps of S7 private Weir adjustable height 0.5m and 0.2m. Has a 0.6m cut out in the centre with drop boards in plac Compton Wood SU5231963858 0.7 7 Low mass concrete wall into grooves to close off centre with STOPLOGS. Not more than 300 above 'normal level'. and below general surrounding ground level. Badly eroded u/s Enbourne RowSU 44410 S8 private Weir with stoplogs LI both banks 63439 SU4441063439 0.3 3 Constructed of 2 No. brick arch culverts with brick headwalls and concrete & tarmac S9 private Road bridge decking over. Has timber handrails u/s and d/s. Gauge board on d/s face. Bramley Road SU6451961051 1.5 7 S10 private Ford over road Concrete and tarmac bed FORD. Gauge board on both banks. Clappers Farm SU6511961653 0 20 Stone fixed crest overfall weir. 2m width. with 0.3m drop. The water flows over 1 step of U/S of Nutkins FarmSU S11 private Fixed crest weir WE 0.3m height. Landuse: CD 52866 59553 SU5286659553 0.3 2 Concrete fixed crest overfall weir. with 0.6m drop. The water flows over 2 steps D/S of Waits FarmSU S12 private of 0.3m height each. Landuse: CD Weir set at 45 deg to L/B 52995 61430 SU5299561430 1 6 Brick/stone fixed crest overfall weir. 4.5m width. with 0.5m drop. The water flows over 1 step of 0.5m height. Middle section has failed. DEBRIS from it may S13 private obstruct flow. Landuse: CD Has no F.D value Upper House Farm SU5321060485 1 4.5 Road bridge. 7m span and 4.5m wide constructed of a brick arch with brick headwalls and concrete & tarmac decking over. Has brick parapets u/s and d/s. Soffit height 1m. S14 private Road bridge RB 0612222WE0102R01001P Landuse: CD Turks Lane SU6537363359 0 2 fixed crest weir within derelict old mill house structure. Diverts the course of the river greatly. Width of 4.5m. both weirs have a drop of about 0.5m. SAFETY? - mill house is a S15 private Fixed crest weirs WE dangerous structure. 0612222WE0102R01006P Landuse: CD Lovegrove's Farm 0 Security Fence for Army S16 private Trash screen. Steel trash screen D/S from footbridge, supported with steel chains. Base, Bramley. SU6488858312 2 S17 private river control structures 3 iron gates in good order. Brick and stone walls and apron Beaurepaire Mill SU6434958433 2.2 River side SSP/tremer sheet timber cap. Downstream SSP stilling pond and block walls. Upstream of Beaurepaire S18 private weirs Acts as 'safety valve' for Mill Pond. Mill Pond SU6427158469 2.2 Brick wing walls left and right banks. Concentration arrow drop and 'wedges.' Wedge Downstream of Beaurepaire S19 private weirs shaped bank blocks. Suggests weir could be raised. House Drive SU6380858849 1.2 Environment Broadford Bridge (head)SU S20 Agency Gauge Board Reference number 24/019. To be inspected annually 69237 61129 SU6923761129 S21 private river control structures River control structure mounted on iron handrailing. with two sluice gates in the centre of Upper Tumbling Baye 0 the channel. with two stoplog gates (with no lifting gear) on either side. LUB=CD Photo: (S.Saye) view d/s r/b Sluice gate structure set on concrete abutments. Timber footbridge over two spans. rack and pinion lifting gear recently greased on l/b (active) missing on r/b. LUB=CD Photo: view S22 private river control structures l/b W. of The Fishery 0 Disused RCS with sluice gates removed with wooden plank over. LUB=CD Photo: view S23 private river control structures d/s l/b The Fishery 0 Environment Long Bridge (head)SU 68267 S24 Agency Gauge Board Reference number 24/020. To be inspected annually 58339 SU6826958340 Main spillway weir. 2 mid-weir brick platforms for footbridge in fair condition. Control channel with vertical sluice gate valve (quite poor with wingwalling eroding and bricks S25 private Weir missing)(1.5m.w.) Another slipway on far right bank 1.5m wide. Brickwork a Longbridge Mill SU6835858189 2 Concrete weir with 2 sluice gates towards R/B (Left one in place). 2 concrete mid channel Environment platforms supporting thin wooden deck of footbridge with steel handrail. Flow over weir is S26 Agency Weir even. Sluice gates are old timber. LUB=CD Photo:View D/S Longbridge Mill SU6836358189 0 Environment Flood Defence structure (Hydrometry S27 Agency Asset 2409) Stilling wells upstream and downstream on weir. Set into banks. Telemetry in Mill. Longbridge Mill, A30. SU6843058264 Environment S28 Agency Level Sensor (Hydrometry Asset 9913) Required for FIM. Pyotts Hill Bridge SU6668853678 Brick box d/s of culvert (approx 2m diameter under junction) Side exit to channel for distributing & weir diversion as flood relief. Contains slots for additional weirs / fish pass. S29 local authority River Control Structure Main s/s outlet 0.6m diameter. Side outlets 1.0m dia. Behind chainlin Alongside A339 junction SU6522952598 1 River control structure which has provision for stop boards. but at time of inspection. none were in place. Brick abutments on either side. which appear in fair condition with no S30 private river control structures significant brick or mortar loss. LUB=CD Photo: view r/b N.E. of Lower Mill 0 Steel trash screen that is set at the U/S end of culvert. Screen prevents small children and S31 local authority Screen large objects from entering culvert. Eastrop ParkSU6449152322 SU6449252322 1 2 Steel trash screen on the U/S end of culvert. The screen prevents debris from clogging up Ringway Culvert, S32 local authority Trash Screen the culvert. Screen is 1.3m in height and 1.3m in width. Basingstoke. SU6494752413 1.3 1.3 CAST CONC. HEADWALL TO CULVERT WITH LOOSELY FITTED TRASH GRID S33 private SCREEN OVER.TIRED CHAIN LINK FENCE ON R/B. LOWER BROOK ST SU6284952187 CONC APRON IN FRONT WITH TARMAC CHANNEL FLOOR APPROACH,LIFTING HINGED TRASH SCREEN,LOCKED.STEEL FENCE S34 local authority Trash Screen ACROSS TOP.ACCESS STEPS DOWN ON L/BANK. A3010 SU6335952273 2 1 x timber sluice gate, with concrete lined channel base set between brick side wall. Gate on S35 private River control structure. steel rack and pinion, with timber frame above. Hartley Mill. 1 River Control Structure - narrowing of tributary stream at confluence. Heavily vegetated on top. Main channel has cut its own way into tributary stream at u/s end (r/b) Rotten timber S36 private river control structures FB crosses top of structure. LUB=CD PHOTO:L/B U/S north of Lance Levy Farm 0 Channel is divided into two sections by a masonry wall. Each section has a timber radial sluice gate operated by chains. R/B: 1.6m wide with old mill wheel in place. L/B: 1m. S37 private River control structure. Masonry side walls - R/B is the mill building. Timber foot bridge U/S end. Lyde Mill. 2.5 Overfall weir with timber stoplogs to control the flow. Concrete deck footbridge over by gate with wooden foot bridge over D/S end - not fixed to brick wingwalls. Masonry side S38 private River control structure. walls. Andwell Mill. 1.5 Steel bell pipe 0.8m diameter to act as a siphon in times of high flow when the FSA reaches D/S extent of FSA, by A30, S39 local authority Siphon. capacity. In brick house with steel screens. D/S end of pipe is inside A30 culvert. Chineham. SU6661755324 2 Environment S40 Agency Level Sensor (Hydrometry Asset 9914) Required for FIM Chineham SU6590455748 Steel bell pipe 0.8m diameter to act as a siphon in times of high flow when the FSA reaches D/S extent of FSA, by A30, S41 local authority Siphon. capacity. In brick house with steel screens. D/S end of pipe is inside A30 culvert. Chineham. SU6661455316 2 3 x steel sluice gates set in steel frame with steel operating mechanism (manual). Timber footbridge over with timber handrails D/S. Brick side walls. Concrete lined channel base S42 private River control structure. with drop of 0.4m at end. Brick bank protection U/S. Beaurepaire Mill. 3 400M U/S TOTFORD S43 private FARM ACCESS Asset owner: Private FARM SU5724738699 THORNEY DOWN COTTAGE. BROWN S44 private D/S HOUSE ACCESS Asset owner: Private CANDOVER SU5757339121 THORNEY DOWN S45 private HOUSE ACCESS Asset owner: Private COTTAGE SU5759839132 B3046. BROWN S46 private ROAD BRIDGE Asset owner: Private CANDOVER SU5761839144 S47 private FOOTBRIDGE Asset owner: Private 41 BROWN CANDOVER SU5767239182 S48 private ACCESS BRIDGE Asset owner: Private 41 BROWN CANDOVER SU5767739186 WAYFARERS COTTAGE. S49 private FOOTBRIDGE Asset owner: Private BROWN CANDOVER SU5770439205 S50 private FOOTBRIDGE Asset owner: Private BROWN CANDOVER SU5771439211 S51 private SPYBUSH LANE CULVERT Asset owner: Private BROWN CANDOVER SU5780839262 OPPOSITE FORMER POST OFFICE. S52 private CULVERT Asset owner: Private BR.CANDOVER SU5789439313 S53 private FIELD ACCESS Asset owner: Private D/S CANDOVER HOUSE SU5803039423 S54 private ACCESS TO CANDOVER HOUSE Asset owner: Private BROWN CANDOVER SU5815839517 OPPOSITE CHURCH S55 private BACK ACCESS TO MOTH FARM Asset owner: Private ACCESS.BR.CANDOVER SU5821739570 MOTH FARM; OPPOSITE CHURCH ACCESS.BR S56 private BRICK CULVERT Asset owner: Private CAN SU5823239582 S57 private MOTH FARM MAIN ACCESS Asset owner: Private BROWN CANDOVER SU5826239606 MOTH FARM. BROWN S58 private FOOTBRIDGE Asset owner: Private CANDOVER SU5828039622 MOTH FARM; BOTTOM OF GARDEN. S59 private ACCESS Asset owner: Private BR.CANDOVER SU5828539627 UNDER ROAD BY GRAVEL CLOSE. S60 local authority SCOUT HUT CULVERT Asset owner: Local Authority BR.CANDOVER SU5854339691 S61 local authority CULVERT Asset owner: Local Authority CHILTON CANDOVER SU5903239924 OPPOSITE CHILTON HOUSE COTTAGE. S62 private FARM ACCESS Asset owner: Private CHILTON SU5913039998 CHILTON MANOR. S63 private FARM ACCESS Asset owner: Private CHILTON CANDOVER SU5917940166 S64 private MANOR FARM ACCESS Asset owner: Private CHILTON CANDOVER SU5927340247 Two Layhay, Preston S65 private Culvert Photo: 074 Candover SU6018441411 Lane off B3046, Preston S66 private Pipes x 2 Photo: 075/076 Candover SU6020841438 Old timbers, Preston S67 private Pipes x 3 photo: 080 Candover SU6056741526 channel outflow approx 1m wide with dropboard sluice between in-situ concrete walls. channel outflow with dropboard sluice Crudely made footbridge on plywood decking, with mesh. Timber board loosely laid on top 0.75km d/s from S68 private and footbridge of concrete wall lining. Head loss across dropboard 0.1m, no handrails. Hurstbourne sluice SU4430645859 sluice approx 4m wide of concrete construction with 3 openings each 1m wide. Part of remains of support for sluice gate on L bank opening but no gates now visible. Concreete 1km d/s of Hurstbourne S69 private sluice and footbridge planks loosley laid on top which form footbridge. Priors` SU4458045769 sluice with 2 openings each approx 1m wide. Complete with steel sluice gates & lifting mechanism in raised position. River channelled betweenbrick wall for approx 7m d/s. 0.75km d/s Hurstbourne S70 private sluice with footbridge Footbridge comprises timber boards, with mesh on RSA section. Prior SU4431045854 single span, 13m long x 2.5m wide of steel truss construction with timber decking. Steel parapet on each side integrated with structure. Hollow square section. Supported on low 200km d/s of roadbridge off S71 private farm access bridge concrete spread footings. Hurstbourne SU4413546185 river channelled over weir between newly constructed brickwork draining wells. Head loss approx 0.75m. Brick wall gauging station on R bank. Pitch tiled roof. Timber footbridge S72 private weir, gauging station and footbridge over weir, handrail on u/s side. Gauging boards immediately upstream of weir 50m d/s of road SU4411146243 brick triple arched road bridge, span 10m x 7m wide. Central arch 1.5m wide. Side arches B3400, Andover Road, S73 private road bridge 1m wide. Brick parpapet approx 1m wide. No handrails. Hurstbourne SU4404346349 adjustable sluice gate fielding a 5m culvert under a farm track, emerging from a brick arch, E of churchm Hurstbourne S74 private adjustable sluice dropping inbank 0.8m over about 7.8m. Prior SU4400046717 single span concrete deck on brick work abutments. Bridge is skewed to road about 45 road to St Mary Bourne, S75 private road bridge degrees. Barbed wire across u/s face. 1km u/s Hurstbourne SU4352447332 100m u/s road bridge, 1km S76 private fishing pier fishing pier extending about 1-1.5m into the river. No handrail. u/s Hurstbourne SU4342647419 saw mill house, 2km u/s S77 private weir submerged breeze block weir. Hurstbourne Prior SU4329747705 saw mill house, 2km u/s S78 private weir submerged rubble and concrete 2 drop weir. Hurstbourne Prior SU4329047734 variety of associated mill structures including adjustable sluice gate. Small hatch and exit saw mill house, 2km u/s S79 private adjustable sluice and other mill structures from turbine. U/s of sluice is weed deflector and screen. Hurstbourne Prior SU4327947757 offtake from main channel with footbridge leading immesiately to 4 stage multi-drop weir. Mill House, 2km u/s S80 private channel outflow with weir and footbridge Handrails both sides. Hurstbourne SU4327447766 S81 private channel outflow with footbridge single span concrete bridge over offtake from main channel. No handrails. saw mill house SU4327347771 u/s saw mill house, 2km u/s S82 private channel inflow, footbridge steel truss bridge over channel into pond. Hurstbourne SU4324247836 u/s of Mill Hosue, 2km u/s S83 private footbridge steel tuss bridge, handrails both sides. Hurstbourne SU4325647868 2 bay 1.2 x 0.8m slightly arched dropboard weir. Handrail on d/s side. U/s of weir is weed d/s of the island, 2.5km u/s S84 private dropboard weir screen, function unknown. Hurstbourne SU4327047984 Spratts Villas, 2.5km u/s of S85 private farmbridge concrete farm access, bridge handrail each side. Hurstbourne SU4324348126 R bank of river is set back. Appears to have been site of cattle drink. Now crossed by timber 100m d/s of Harrow Way, S86 private footbridge footbridge. Length approx 20m. Single handrail. Barbed wire between supports under deck. 2km d/s St Mary SU4303648503 single span road bridge, span 3m. Concrete deck supported on concrete abutments. Timber handrailing on low concrete. Parapet upstands both sides. Abutments partially covered with HArrow Way Road, 2km S87 private road bridge vegetation. d/s St mary Bourne SU4303148665 twin pipe culvert under access road within vitacress grounds. Concrete pipes 0.75m length, watercress beds, 1.6km d/s S88 private farm bridge 15m concrete wing wall each end. Electrical cable connected to upstream headwall. St Mary Bourne SU4280649134 8 plastic pipes 500mm each. Concrete slab on concrete pier and abutment. No hand or watercress beds, 1.5km d/s S89 private farm access bridge guardrailing. Electric cable attached to side of deck. St Mary Borne SU4270949330 concrete sluice, 2 openings each 1.2m wide. Metal sluice gate in closed posistion on L side. Timber footbridge over top with tubular handrail on upstream. A smaller single opening S90 private sluice footbridge sluice with metal gate positioned near R bank until footbridge arc. 1km d/s of St Mary Bourne SU4253849518 2 span arc lane concrete road bridge with central brick piling. 2 steel 100mm pipe on d/s S91 private road bridge face. Training walls u/s & d/s. opp. Portary, St Mary Borne SU4230650141 3.5 concrete arch culvert from lake, controlled by sluice gate at lakeside. Weed screen also at S92 private culvert inflow from lake lake end of culvert. St Mary Borne SU4228850151 S93 private spillway block lined spillway taking excess water from lake to river. Stepping stone crossing. St Mary Borne SU4227950158 triple brick arch road bridge. 5m span and about 7m wide. 2 outer arches smaller than road to Hurstbourne S94 private road bridge central arch. Tarrant, St Mary Borne SU4218950397 4 bay dropboard sluice gates, immediately d/s of gravel covered road bridge. Gauge board S95 private sluice and bridge on L side fence. Spring Hill, St MAry Borne SU4206850560 Environment S96 Agency River level telemetry site (FRM owned) Includes gauge board SU4206050570 on d/s side of Bapotist Hill single span footbridge, 5m span. Main support beams steel RSCS. Tarmac topping to deck. road bridgeBaptist Hill, S97 private footbridge Brickwork abutment. Tubular steel handrailing on both sides. 0.5km NW of St Mary Borne SU4166850807 single span concrete road bridge carrying Baptist Hill over the river. Span 5m, width approx. 6m. Supported on concrete abutment. Timber steel handrailing both sides. Steel mesh weed Baptist Hill, 0.5km NW of St S98 private road bridge screen loosely attached to u/s side of bridge. Mary Borne SU4165550813 single span concrete road bridge. Span 8m, width 6m. Metal handrailings on both sides. Bridge crosses river at approx 40 degrees skewed angle. Wire mesh loosely attached to L Gangbridge Lane, 0.75km S99 private road bridge half of d/s side of bridge. NW St Mary Borne SU4158750847 Middle span 2m, side span approx 1m. Metal bar across main span on u/s side. Curved wing Gangbridge, 0.75km d/s S100 private masonry arched road bridge walls. Precast concrete caping. Height of walls above river approx 3m. Width approx 6m. from Stoke SU4077851434 single span bridge 6m long x 2.5m wide. Steel I beams supporting concrete infill deck. Concrete abutments, steel handrailing both sides. Painted. Entrance gate at R side of bridge S101 private access road bridge leading to Garston. entrance to Garston, Stoke SU4036651741 garden storage bulding of timber construction with steel support beams which span across river onto concrete abutment on R bank. Length of building 9m, width 3.5m. Timber lag S102 private storage building spanning river span river immediately upstream of this building. 30m u/s of Garston, Stoke SU4035851752 single span access bridge to private garage. Span 4.5m, width 2.5m. Steel I beams with concreet infill deck. Brickwork abutments with curved brick wing walls 1m long. Pointed S103 private access bridge to private garden tubular steel handrailing both sides. 150m d/s Stoke SU4033151801 single span arched brickwork roadbridge, inset stone indicates built in 1868, span 3.5m. S104 private arched road bridge parapet walls and angled wing walls in brickwork with rounded stone capping. Old Post Office, Stoke SU4030251887 twin arch concrete road bridge. Central brick piling, no handrails or crash barriers. Looks Burry Hill Farm, 0.5km u/s S105 private road bridge like it used to be brick arch but repaired with concrete. from Stoke SU3993452326 Store Lane, 1km u/s from S106 private road bridge single arch brick road bridge, 1.5m opening with 0.3m clearance, width 7m. Stoke SU3944652455 400m W Stoke Lane, 1km S107 private old footbridge collapsed concrete footbridge. d/s Hurstbourne SU3905352411 brick arched single span bridge linking buildings to grounds on R side of river. Length adj paper mill farm house, S108 private brick arched access bridge approx 8m, width 4m. SE H'bourne Priors SU4483345998 2 adjustable weirs,timber dropboards & lifting mechanism, d/s of weirs channel seperated adjustable weir with dropboards, timber by 3m long concrete wall. Water passes under arched bridge immediately d/s of weirs, 5m u/s arched bridge, SE S109 private footbridge timber footbridge over, 5m long, 2m wide, handrails both sides. H'bourne Priors SU4483846008 drainage channel outflow approx 3m wide at discharge between insitu concrete vertical sided drainage outflow with timber footbridge walls. 2 openings with dropboards create weir. Head loss approx 0.15. Timber footbridge S110 private and weir 3m x 1m with timber handrails both sides, mesh to decking, steel rsa. SE of Hurshbourne Priors SU4487946078 2 gate sluice with lifting/lowering mechanism. Brick lining to sides of channel around sluice. 100m u/s of farm access S111 private sluice with timber footbridge Timber footbridge, no handrail. bridge SU4474845834 footbridge approx 11m long x 1.5m wide. Timber boards (with mesh) supported by 2 no u/s limit of defence 3 at S112 private footbridge steel I beams. Single span steel beams supported on concrete blocks on R bank, no handrail. confluence SU4467845907 triple arched road bridge, length 8.5m, width 3m. Insit concrete construction with brickwork to upper elevations. Tubular handrails each side. Sign on road indicates 'wear bridge' weight Hurstbourne Priors, Paper S113 private arched road bridge limit 7.5 tonnes. Mill bridge. SU4489346203 weed screen, steel frame with wooden deck for half channel width, tubular steel in mid u/s Paper Mill bridge, E of S114 private weed screen channel for 25m to footbridge. Hurshbourne Priors SU4489946278 500m u/s of Testbourne 2 1x12m steel sluice gate in masonry sidewalls. Concrete slab foortbridge, no handrails. Cottages, Hurshbourne S115 private sluice gates Disused on RHB with steel drop boards used to feed watermeadows. Priors SU4495546797 concrete deck and abutments. 2 sluices with drop boards (steel). Masonry bridge. Handrails S116 private farm bridge on both sides. Sheet piled on d/s RHB. Hurstbourne Priors SU4527346955 S117 private disused rail bridge masonry 3 span arched railbridge/ River passes through middle span only. Disused railway. E of Tufton SU4542846929 S118 private footbridge arched concrete footbridge. 3 concrete beams. Handrail on one side only. 40m u/s railbridge SU4548546907 S119 private stone weir lose stone well of varying height due to removal of stones. Tufton Manor Farm, Tufton SU4567846887 steel framed footbridge with wooden deck, mesh cover, no handrail. Weed screen for 7m on S120 private footbridge LHB. 10m u/s Paper Mill bridge SU4485246249 disused sluice gates, masonry side wall but space for dropboards (present on bankside). 3 opp. watercress beds, E of S121 private sluice/footbridge channels. Wooden footbridge with mesh. Hurshbourne Priors SU4468246418 watercress beds, NW of S122 private stone weir loose stone weir. Tufton SU4482446987 masonry sluice, side walls and footbridge with 1m headloss, groves for dropboard. Possible u/s watercress beds, SE of S123 private sluice out take for watercress beds but no visible structures. Hurshbourne Priors SU4493547084 Little Bulls, Hurstbourne S124 private drainage ditch drainage ditch d/s of sluice (5m). Clear drainage board. Priors SU4506047079 S125 private sluice masonry sluice with soace for 2 steel dropboards. Paddle mechanism disused on bank. Little Bulls, NW of Tufton SU4507147080 100m d/s of carrier outtake, S126 private steel weir with wooden boards steel girder used as weir with short space verticals used to prop wooden boards. NW of Tufton SU4520447044 10m d/s carrier out take, S127 private farm bridge steel girders with concrete slab deck. 2 steel handrails. Concrete abutments. NW of Tufton SU4528946975 at carrier out take, NW of S128 private sluice masonry sluice at carrier out take. Small overflow channel, 10m u/s. Tufton SU4529246965 out take for disused water meadows. Re-enters d/s of A34 road bridge (Trentharn beat). 1m u/s of sluice, S129 private drainage ditch outflow with sluice Steel sluice/stop board. Whitchurch SU4609047298 d/s end of subreach, S130 private sluice steel framed sluice with masonary side walls. Timber footbridge, 2 steel handrails. Whitchurch SU4605047216 access road to Fulling Mill, S131 private road bridge steel girders, concrete deck, masonary wing walls, steel rails u/s and d/s. Whitchurch SU4608347281 2 x arched masonry culvert beneath footpath in private conditions of Fulling Mill. Wooden 8m u/s Fulling Mill acces S132 private sluice/footbridge sluice on u/s side. Head loss 1.0m. LHB - sheet, RHB - no sluice gate. bridge. SU4608147291 2m u/s footbridge, S133 private steel sluice gate steel sluice gate linking to carrier. Concrete side walls. Whitchurch SU4609347318 concrete sluice with space for dropboards, although appears disused. 2 footbridges, 1 timber d/s end of reach, NE of S134 private sluice (disused) and footbridge with steel rails, 1 steel with wooden deck. Tufton SU4589547114 dual carriageway road bridge. Also part of structure described under Trentham survey. Main S135 private A34 road bridge river to S flows beneath 2nd span. Concrete wall on RHB at footpath. A34, NE of Tufton SU4594147139 wooden footbridge on single masonary pier. Handrail on u/s side. Mesh covered deck. 10m u/s of A34 bridge, S136 private footbridge and weir Stone weir head loss = 0.2m. Whitchurch SU4597747155 wooden footbridge with 1 timber support. New construction. 1 handrail on d/s side. Gate 30m d/s Fulling Mill, NE of S137 private wooden footbridge on RHB mesh covered deck. Wooden support in water. Tufton SU4602747249 hatches/sluices at Fulling Mill/private house. hatches inside building (inaccessible). Wooden S138 private Fulling Mill footbridge access to house. Fulling Mill, NE of Tufton SU4606647288 10m u/s Fulling Mill, S139 local authority concrete footbridge 16m wide concrete single span footbridge with 2 timber handrails, arched profile. Whitchurch SU4607847311 single handrail mesh covered timber bridge, small clearance makes it likely to be drowned during high water. Worst flooding in the lawns in 30 years has been nothing more than 1 S140 private bridge foot rise in water. the lawns, Whitchurch SU4610247751 S141 private bridge over channel out. rickety bridge over channel out, feeding ornamental diversioning stream. the lawns, Whitchurch SU4614047842 S142 private foot bridge silk mill, Whitchurch SU4622347881 S143 private offtake and sluice gate silk mill, Whitchurch SU4624247886 S144 private footbridge silk mill, Whitchurch SU4626447890 S145 private bridge footbridge, single handrail. silk mill SU4620347887 S146 private mill and cross channel mill comprising weedscreen, sluice gates, water wheels and culvert under mill building. silk mill, Whithchurch SU4622347904 Winchester Road, S147 private road bridge 3 arch (brick) skewed road bridge with piped services on u/s and d/s faces. Whitchurch SU4628147970 just d/s of Test Road, S148 private bridge wooden footbridge, 2 handrails. Whitchurch SU4641748073 S149 private bridge road bridge with pavement on d/s side only. GMS handrail. Test St, Whitchurch SU4645748107 opposite Boxmore Cottages S150 private private road bridge private road bridge - cars and ambulanes only. (39 London St) SU4653848210 precast concrete single span footbridge with concrete platform of GMS handrailing, 0.15 footpath from town mill, S151 private footbridge and outfall diameter outfall u/s R bank. Whitchurch SU4660448218 footbridge traversing low and high level channel. Low level channel is main. Tiny channel in NE of town mill on public S152 private bridge d/s R bank. footpath SU4670348131 S153 private timber footbridge timber footbridge Whitchurch SU4647648059 S154 private timber footbridge timber footbridge, no handrails. Whitchurch SU4646848090 0.75m wide steel hand operated under slot sluice. Flow is out of the river, opening is S155 private channel out with footbridge and sluice. submerged. Whitchurch SU4751747766 S156 private footbridge over channel handrail - less mesh covered timber footbridge over channel in. Bere Mill, E of Whitchurch SU4780548023 Winchester Road, S157 private road bridge 4 brick arches set into main structure. Whitchurch SU4630147896 house on stilts partially oversailing watercourse with shallow submerged weir immediately adj. to Test Road, S158 private house/bridge/weir downstream and timber footbridge immediately upstream. Whitchurch SU4643247982 S159 private weir submerged weir, rectangular area of unknown material. just d/s of Town Mill SU4658448064 S160 private timber footbridge/channel in bridge is 10m wide and 0.5m above the water level. 10m d/s of Mill, Whitchurch SU4662448077 1 HCC maintained bridge, diversion channel through water wheel (LHS), 2 brick arch culverts (RHS). 1 ornate brick bridge, outlet from culverts, weed/eel traps, wooden fishing S161 private Mill of surrounding structures pier extending over 0.5 of the width, inlet channel traversed by bridge. Town Mill SU4664348080 S162 private footbridge bridge is 12m wide and 1m above the water level. just u/s of Mill, Whitchurch SU4665048081 150m u/s of mill, S163 private bridge mesh covered scaffold supported timber footbridge, mid clearance is 0.7m, 10m wide. Whitchurch SU4683848071 submerged timber weir, occuring at a number of different locations along defence 4. water 250m u/s of watercress S164 private weir head is 0.15-0.3 bedds, Whitchurch SU4714947887 275m u/s of watercress S165 private footbridge timber platform. Mesh covered pier supported handrail less bridge. beds, Whitchurch SU4719547885 190m u/s of footbridge, S166 private weir submerged timber weir, waterdrop 0.30m Whitchurch SU4723047694 flumed weir with dropboard provision, brick revetment u/s L. Concrete bay work abutments.Corrugated iron d/s face, bridge is timber on steel beams, no handrails. U/s RHS 230m u/s of weir, S167 private weir with footbridge over. old dropboard sluice (0.75m wide). Whitchurch SU4740647764 300m d/s of Bere Mill, E of S168 private weir submerged timber weir 0.15m drop. Whitchurch SU4763047856 submerged wooden weir with water drop of 0.3m over 1-2m. Wooden pier angled upstream, 200m d/s of Bere Mill, E of S169 private weir/pier 1-2m upstream of weir. Whitchurch SU4778648016 S170 private weir mini submerged weir 8m wide Bere Mill, E of Whitchurch SU4779948078 u/s of Bere mill, E of S171 private bridge/channel footbridge over channel in, footbridge, no handrails. Whitchurch SU4777748260 60m d/s of roadbrodge, S172 private carrier outflow with sluice sluice gate to carrier outfall. Freefolk SU4860548666 S173 private flow deflector with weed screen timber flow defelctor, 7m in length, steel weed screen, 2m in length. 55m d/s of road bridge SU4862948659 S174 private 0.3m diameter outfall clay pipe at footpath level encased in concrete. 25m u/s of weir, Laverstoke SU4928348678 timber revetment seperates stream from S175 private pit. at u/s end timber supports earth banks. D/s timber seperates flood pit. Church Lodge, Laverstoke. SU4972948811 inflow from ditch and sluice bypass nr pheasantry, Laverstoke S176 private above weir outfall fe by sluice bypass and drainage ditch. L side natural. R side weir construction. Park SU4980349357 SW of Northington Farm, S177 private ditch outfall with sluice wooden sluice (1m wide channel). Square masonry outfall. Laverstoke park SU4982049369 S178 private sluice/footbridge hand operated steel undersheet gate, 1-2m wide. 1.5m wide timber footbridge. 12m long Bere Mill, E of Whitchurch SU4782548122 overflow weir. 15m wide masonry road bridge - 3x3m wide arched culverts, approx 15m high at apex, no u/s of Bere Mill, E of S179 private road bridge obvious defects. Whitchurch SU4782748178 entrance to Bere Mill and S180 private ornate brick road bridge antique ornate brick road bridge. 3 span arches. cottages SU4797748442 S181 private wooden footbridge wooden footbridge, chicken wire topping. 490m d/s of Freefolk SU4801748428 S182 private sluice with steel gates sluice with 3 gates. d/s road bridge, Freefolk SU4860848677 bridge on minor road. Masonry arch with brick abutments. Arches 2m wide, bridge 7m by nr St Nicholas church, S183 private masonry road bridge 3m. Freefolk SU4867648671 masonry and concrete roadbridge with asphalt topping and iron railings. Steel girders with u/s of manor house/St S184 local authority road bridge (masonry) extension on u/s end to accommodate footpath. Nicholas church SU4882448704 60m u/s of SoD, S185 private masonry farm bridge not in use, derelict, not to be used, unsafe. Lowerstoke SU4911948666 5 arch masonary road bridge each approx 1.0m span. Low masonary parapet d/s side. Steel d/s end of defence/mill, S186 private road bridge handrails on both sides. Service pipe crossing on d/s side. Laverstoke SU4916848669 river culverted for 14m beneath mill buildings. 2 channels built on steel girder RHB channel controlled by rotating gate. LHB channel by vertical drop gate both inside building. Steel S187 private mill building screen d/s end of LHB channel. Weed screen on u/s RH channel mill building SU4919548672 mill building across river, masonry on steel girders with masonry abutments, 45m long, S188 private mill buildings concrete piers in river at u/s end. mill buildings SU4920848671 steel frame with concrete deck, steel handrails, good condition, service pipe on u/s side and 2m u/s of start of defence 2, S189 private footbridge mill. Laversstoke SU4925148681 steel girder frame, asphalt deck, steel rails u/s and d/s. Service pipe on u/s side. 60m wide S190 private roadbridge on d/s side. 80m on u/s side. u/s of mill buildings SU4928648688 u/s end of defence, S191 private weir and footbridge concrete weir with steel dropboards. Concrete footbridge on piers, steel handrails. Laverstoke. SU4930548688 mill pond inflow Laverstoke S192 private naturalised sstream outfall with screens Park SU4952148726 S193 private masonry bridge with 4 small arches masonry - 4 arch bridge with parapets, length 10m, width 4m, limited flow capacity. Church Lodge, Laverstoke SU4964248768 concrete deck and masonry abutment, steel beams and guard rails, appears to be st marys church ruins, S194 private bridge replacement deck and original abutment (4m wide and 10m long). Laverstoke SU4979149161 nr pheasantry, Laversstoke S195 private weir submerged weir with masonry revetment u/s width is 3m, submerged revetment. Park SU4980949376 nr pheasantry, Laverstoke S196 private wooden footbridge, no handrails wooden slats on wooden beams with mesh cover. Masonry abutments. Park. SU4983349390 4 no 1mx1m steel gates, drop of 100mm in water level. Wooden footbridge adjacent, mesh Northington Farm, SW of S197 private 4 gate sluice/footbridge cover, no handrails, 4m wide channel. Lynch SU5026249412 E of Northington Farm, S198 private ditch inflow with sluice gate. sluice with gate missing. Outfall from carrier over concrete apron, strong flow, 1m wide. Lynch SU5038849680 mill house, 2 culverts, 1 wheel and bypass sluice, 2 steel footbridge, single handrail, drop in S199 private mill building water level = 1.5m. Inaccessible. Southington Mill, Lynch SU5055449755 6m high mill building - new concrete render. 1m above water line. 1m outfall pipe and 1 u/s mill roadbridge, S200 private vertical masonry wall/building concret butress. Multiple outfalls from workhops. Laverstoke SU4916548715 S201 private masonry farm bridge derelict masonry farm bridge. Laverstoke Park SU4912048688 opp. mill car park, S202 private drainage ditch and footbridge drainage ditch with wooden footbridge of single planks, no handrails and appears unsafe. Laverstoke SU4918548735 RSJ supported. Car park and mill buildings. Carrier flows under building for 15m. Takes 90 S203 private culvert beneath mill building degree turn under buildings. Service pipe on u/s side. Sluices in building. Inaccessible. mill building, Laverstoke SU4920448719 steel frame with asphelt deck with concrete abutments.Steel handrails u/s and d/s. 2 service S204 private roadbridge, access to carpark handrailson u/s side. u/s mill building, Laverstock SU4921348715 20m u/d road bridge, S205 private footbridge/covered walkway covered walkway, footbridge of aluminium sheeting on concrete abutment on RHS. Laverstoke SU4922048715 S206 private 20m buildings and culverts corrugated steel building, steel girders on numerous concrete piers. 15m d/s sluice, Laverstoke SU4924948713 outlet from mill pond, 3 channels. Main centre channel is steel sluice gate - inoperable. 2 S207 private tributary and sluice side channels have stop boards, concrete walls. 1.3m head loss. Gate deliberately inoperable. mill pond, Laverstoke SU4927948711 S208 private steel footbridge steel frame, deck and rails, concrete (RHB) and masonry (LHB) abutments. 10m d/sofftake, Laverstoke SU4929148709 steel girders supporting hardcore (car park) over 2 sluices. 2 steel sluice gates on u/s side, outtake at head of carrier, S209 private carrier outlet/sluice pipe crossing on d/s side. Laverstoke. SU4930048705 Southington Lane, E of S210 private ditch naturalised drainage ditch and carrier outflow. Lynch SU5079249696 S211 private outfall outwards with weir outfall to carrier, frontface inaccessible. Overton Golf Course SU5110549811 roadbridge 5m wide x 10m long steel beams, concrete deck, masonry abutments, steel guard S212 private road bridge rails. Southington Mill, Lynch SU5067749710 farm bridge, masonry arch, steel railings, 5m long by 4m wide, used as footbridge. Interior nr Southington Lane, E of S213 private farm bridge arch inaccessible. Lynch SU5094449775 Southington Lane, E of S214 private sluice and remains of wheel water wheel with sluice. Level differenece = 2m. Lynch SU5095449776 masonry arch (3) bridge with concrete footway, on masonry abutments. 4m wide and 2m S215 private road bridge with footbridge added footpath with railing on d/s side. Bridge Street, Overton SU5136649804 channelised outfall from settlement ponds (approx area 4Ha). Natural lined channel outfall from settlement ponds with FB discharges via half pipe (steel) and concrete box outfall. Wooden FB with handrails over S216 private on bridge outfall. Settlements ponds, Overton SU5160450137 wooden footbridge with mesh cover approx 8m long. 300mm wide. No handrails. Wooden S217 private wooden footbridge and debris screen. and concrete supports. Wooden debris trap over half width. behind Town Mill, OVerton SU5161649806 mill house with race (2 culverts, 2 x 1.5 x 0.4 x 1.5) sluice controlled bypass channel (1.0 x Quidhampton Mill, S218 private mill house 0.5). Inaccessible. quidhampton SU5175850253 skewed road bridge over main stream and 2 steel pipes (feeding settlement ponds). 8m long, S219 private road bridge 6m wide. Steel beam concrete deck, masonry abutments. Station Road bridge SU5176950241 5m u/s of pipe line crossing, S220 private trees across stream 3 tree trunks across stream. Width 3m, clearance 100, 2000, 2500mm. Quidhampton SU5199550270 weir on mainstream, outfall outweards R bank. Single structure same size openings. 100mm S221 private weir of outfall outwards freeboard south, 50mm other. Iron sheeting wood as boards. S of Quidhampton Farm SU5203750255 Quidhampton Cottage, S222 private submerged weir submerged weir, partly obscured by weeds. Probably wood, length 5m. Quidhampton SU5230550429 Quidhampton Cottages, S223 private small twin arch road bridge brick arch (x2) bridge country lane. 3m wide, 5m long. Quidhampton SU5235350471 pond outfall with steel dropboard in concrete slots. Concrete supports for dropboards in V u/s of road bridge at S224 private sluices and pond outfall shape in main channel - no boards. Quidhampton Cottages. SU5236350485 footbridge, L side single 200 wide timber with rush (10000 long). R side single 250 wide S225 private footbridge timber with handrail over side 7000 long. Fitted with wire suaves. u/s Quidhampton Cottages SU5249550570 precast concrete slabs on brick abutments with steel handrail one side. 3m long x 1m S Polhampton FArm, S226 private footbridge wide.earth filled approaches as bridge is too short. Polhampton SU5268750312 ground bed ford 8m long x 3m wide. Timber footbridge with moss cover (8m long x 0.5m track crossing on Lower S227 private ford, footbridge and weedscreen wide). Timber fence serving as handrail on 1 side, 2m wide weedscreen. Ashe Farm, Ashe SU5318349950

Note: This table is to be read in conjunction with Tiles A to F

Figures

The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 4 THAMES WATER SEWER RECORDS AND CORRESPONDANCE

GRAR/20-0018/FRA01

RGP Mill Pool House Mill Pool House

GODALMING GU7 1EY

Search address supplied The Hideaway Hideaway Heath End Road Baughurst Tadley RG26 5ND

Your reference 20-0018

Our reference ALS/ALS Standard/2020_4181224

Search date 14 April 2020

Knowledge of features below the surface is essential for every development

The benefits of this knowledge not only include ensuring due diligence and avoiding risk, but also being able to ascertain the feasibility of any development.

Did you know that Thames Water Property Searches can also provide a variety of utility searches including a more comprehensive view of utility providers’ assets (across up to 35-45 different providers), as well as more focused searches relating to specific major

utility companies such as National Grid (gas and electric).

Thames Water Utilities Ltd Property Searches, PO Box 3189, Slough SL1 4WW DX 151280 Slough 13

[email protected] www.thameswater-propertysearches.co.uk

0845 070 9148

Search address supplied: The Hideaway, Hideaway, Heath End Road, Baughurst, Tadley, RG26 5ND

Dear Sir / Madam

An Asset Location Search is recommended when undertaking a site development.It is essential to obtain information on the size and location of clean water and sewerage assets to safeguard against expensive damage and allow cost-effective service design.

The following records were searched in compiling this report: - the map of public sewers & the map of waterworks. Thames Water Utilities Ltd (TWUL) holds all of these.

This searchprovides maps showing the position, size of Thames Water assets close to the proposed development and also manhole cover and invert levels, where available.

Please note that none of the charges made for this report relate to the provision of Ordnance Survey mapping information. The replies contained in this letter are given following inspection of the public service records available to this company. No responsibility can be accepted for any error or omission in the replies.

You should be aware that the information contained on these plans is current only on the day that the plans are issued. The plans should only be used for the duration of the work that is being carried out at the present time. Under no circumstances should this data be copied or transmitted to parties other than those for whom the current work is being carried out.

Thames Water do update these service plans on a regular basis and failure to observe the above conditions could lead to damage arising to new or diverted services at a later date.

If you have any further queries regarding this enquiry please feel free to contact a member of the team on 0845 070 9148, or use the address below:

Thames Water Utilities Ltd Property Searches PO Box 3189 Slough SL1 4WW

Email: [email protected] Web: www.thameswater-propertysearches.co.uk

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4WW, DX 151280 Slough 13 Page 2 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Waste Water Services

Please provide a copy extract from the public sewer map.

Enclosed is a map showing the approximate lines of our sewers. Our plans do not show sewer connections from individual properties or any sewers not owned by Thames Water unless specifically annotated otherwise. Records such as "private" pipework are in some cases available from the Building Control Department of the relevant Local Authority.

Where the Local Authority does not hold such plans it might be advisable to consult the property deeds for the site or contact neighbouring landowners.

This report relates only to sewerage apparatus of Thames Water Utilities Ltd, it does not disclose details of cables and or communications equipment that may be running through or around such apparatus.

The sewer level information contained in this response represents all of the level data available in our existing records. Should you require any further Information, please refer to the relevant section within the 'Further Contacts' page found later in this document.

For your guidance: • The Company is not generally responsible for rivers, watercourses, ponds, culverts or highway drains. If any of these are shown on the copy extract they are shown for information only. • Any private sewers or lateral drains which are indicated on the extract of the public sewer map as being subject to an agreement under Section 104 of the Water Industry Act 1991 are not an ‘as constructed’ record. It is recommended these details be checked with the developer.

Clean Water Services

Please provide a copy extract from the public water main map.

With regard to the fresh water supply, this site falls within the boundary of another water company. For more information, please redirect your enquiry to the following address:

Southern Water Southern House Yeoman Road

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4WW, DX 151280 Slough 13 Page 3 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Worthing West Sussex BN13 3NX

Tel: 01903 264 444 Fax: 01903 691 435

For your guidance: • Assets other than vested water mains may be shown on the plan, for information only. • If an extract of the public water main record is enclosed, this will show known public water mains in the vicinity of the property. It should be possible to estimate the likely length and route of any private water supply pipe connecting the property to the public water network.

Payment for this Search

A charge will be added to your suppliers account.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4WW, DX 151280 Slough 13 Page 4 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Further contacts:

Waste Water queries

Should you require verification of the invert levels of public sewers, by site measurement, you will need to approach the relevant Thames Water Area Network Office for permission to lift the appropriate covers. This permission will usually involve you completing a TWOSA form. For further information please contact our Customer Centre on Tel: 0845 920 0800. Alternatively, a survey can be arranged, for a fee, through our Customer Centre on the above number.

If you have any questions regarding sewer connections, budget estimates, diversions, building over issues or any other questions regarding operational issues please direct them to our service desk. Which can be contacted by writing to:

Developer Services (Waste Water) Thames Water Clearwater Court Vastern Road Reading RG1 8DB

Tel: 0800 009 3921 Email: [email protected]

Clean Water queries

Should you require any advice concerning clean water operational issues or clean water connections, please contact:

Developer Services (Clean Water) Thames Water Clearwater Court Vastern Road Reading RG1 8DB

Tel: 0800 009 3921 Email: [email protected]

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4WW, DX 151280 Slough 13 Page 5 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Asset Location Search Sewer Map - ALS/ALS Standard/2020_4181224 ! 1 4601 =

k n 4650 a 2a b 2 y l l

o H 4502 12 ! % 351E ! ! !351A 9 T h 4501 4 or ne % Bes !351B om !351C B # lac kberr 351D y C 351F ! ou ! 13 351G ! !451B 0 5 4 W eek o en 0 t d 0 a El 1 2

Sub Sta !451A 5

4 1 4503 # = 8 12 4 %

5 P 2 m ine 2 .3 Co 4506 ! 6 tta n s 4504 g y = ! e k o

a l

% 10 a % a h w v a O a l 5 0

% A 2 5 e u n 3501 2 1 d e # i wi B 4505 ! H T

4507 % =! 6

6 O'B 4 P 4404 EE% % INK = GA 22 S T 5 L 225 H 4 AN C 4 E

OU ! R % T ! 4408

4403 ! 0 %

4401 0

5 % 1 1 2 25 R 4405 C Cat 1 =!

be 4409

lls % ! % 0

4402 0

3 B . irch % 4406 0 5 1 C 22 = op 4 5 pic Fair 8 3 e ! 4 1 0 5 0 441F . 4 View 4410 % ! 441C Red O ! 'B E Roof One 4407E 5 22 G2 5 A5 8 = R Oak D 3 E N S 44 % ! The width of the displayed area is 200 m and the centre of the map is located at OS coordinates 458406,162520 The position of the apparatus shown on this plan is given without obligation and warranty, and the accuracy cannot be guaranteed. Service pipes are not shown but their presence should be anticipated. No liability of any kind whatsoever is accepted by Thames Water for any error or omission. The actual position of mains and services must be verified and established on site before any works are undertaken.

Based on the Ordnance Survey Map with the Sanction of the controller of H.M. Stationery Office, License no. 100019345 Crown Copyright Reserved.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 6 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

NB. Levels quoted in metres Ordnance Newlyn Datum. The value -9999.00 indicates that no survey information is available

Manhole Reference Manhole Cover Level Manhole Invert Level 4402 105.64 104.44 451A n/a n/a 451B n/a n/a 4650 105.34 104.86 4501 n/a n/a 4405 105.64 104.04 4409 105.63 104.51 4404 105.75 104.17 4408 105.73 104.65 4505 105.82 104.3 4504 105.9 104.42 4507 105.81 104.75 4503 105.86 104.5 4506 105.91 104.86 5401 105.53 104.19 4407 105.47 103.8 441F n/a n/a 4410 n/a 104.36 4406 105.57 103.91 351E n/a n/a 351F n/a n/a 3502 n/a n/a 351G n/a n/a 351D n/a n/a 351C n/a n/a 351B n/a n/a 351A n/a n/a 3501 n/a n/a 4403 105.97 n/a 4401 105.95 n/a 441C n/a n/a 4502 n/a n/a

The position of the apparatus shown on this plan is given without obligation and warranty, and the accuracy cannot be guaranteed. Service pipes are not shown but their presence should be anticipated. No liability of any kind whatsoever is accepted by Thames Water for any error or omission. The actual position of mains and services must be verified and established on site before any works are undertaken.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 7 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

ALS Sewer Map Key

Public Sewer Types (Operated & Maintained by Thames Water) Sewer Fittings Other Symbols A feature in a sewer that does not affect the flow in the pipe. Example: a vent Symbols used on maps which do not fall under other general categories Foul: A sewer designed to convey waste water from domestic and is a fitting as the function of a vent is to release excess gas. / Public/Private Pumping Station industrial sources to a treatment works. Air Valve Change of characteristic indicator (C.O.C.I.) Surface Water: A sewer designed to convey surface water (e.g. rain Dam Chase water from roofs, yards and car parks) to rivers or watercourses. Invert Level Fitting Summit

M Meter Combined: A sewer designed to convey both waste water and surface water from domestic and industrial sources to a treatment works. Areas Vent Column Lines denoting areas of underground surveys, etc. Trunk Surface Water Trunk Foul Operational Controls Agreement A feature in a sewer that changes or diverts the flow in the sewer. Example: A hydrobrake limits the flow passing downstream. Operational Site Storm Relief Trunk Combined Control Valve Chamber PPVent Pipe Bio-solids (Sludge) Drop Pipe Tunnel Ancillary

Proposed Thames Surface Proposed Thames Water Weir Conduit Bridge Water Sewer Foul Sewer

Gallery Foul Rising Main End Items Other Sewer Types (Not Operated or Maintained by Thames Water) End symbols appear at the start or end of a sewer pipe. Examples: an Undefined End at the start of a sewer indicates that Thames Water has no Foul Sewer Surface Water Sewer Surface Water Rising Combined Rising Main knowledge of the position of the sewer upstream of that symbol, Outfall on a Main surface water sewer indicates that the pipe discharges into a stream or river. Combined Sewer Gulley Proposed Thames Water Sludge Rising Main Rising Main Outfall W Culverted Watercourse Proposed

Vacuum Undefined End Abandoned Sewer Inlet

Notes: 1) All levels associated with the plans are to Ordnance Datum Newlyn. 6) The text appearing alongside a sewer line indicates the internal diameter of 2) All measurements on the plans are metric. the pipe in milimetres. Text next to a manhole indicates the manhole reference number and should not be taken as a measurement. If you are 3) Arrows (on gravity fed sewers) or flecks (on rising mains) indicate direction of unsure about any text or symbology present on the plan, please contact a flow. member of Property Insight on 0845 070 9148. 4) Most private pipes are not shown on our plans, as in the past, this information has not been recorded. 5) ‘na’ or ‘0’ on a manhole level indicates that data is unavailable.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 8 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Terms and Conditions

All sales are made in accordance with Thames Water Utilities Limited (TWUL) standard terms and conditions unless previously agreed in writing.

1. All goods remain in the property of Thames Water Utilities Ltd until full payment is received. 2. Provision of service will be in accordance with all legal requirements and published TWUL policies. 3. All invoices are strictly due for payment 14 days from due date of the invoice. Any other terms must be accepted/agreed in writing prior to provision of goods or service, or will be held to be invalid. 4. Thames Water does not accept post-dated cheques-any cheques received will be processed for payment on date of receipt. 5. In case of dispute TWUL`s terms and conditions shall apply. 6. Penalty interest may be invoked by TWUL in the event of unjustifiable payment delay. Interest charges will be in line with UK Statute Law ‘The Late Payment of Commercial Debts (Interest) Act 1998’. 7. Interest will be charged in line with current Court Interest Charges, if legal action is taken. 8. A charge may be made at the discretion of the company for increased administration costs.

A copy of Thames Water’s standard terms and conditions are available from the Commercial Billing Team ([email protected]).

We publish several Codes of Practice including a guaranteed standards scheme. You can obtain copies of these leaflets by calling us on 0800 316 9800

If you are unhappy with our service you can speak to your original goods or customer service provider. If you are not satisfied with the response, your complaint will be reviewed by the Customer Services Director. You can write to her at: Thames Water Utilities Ltd. PO Box 492, Swindon, SN38 8TU.

If the Goods or Services covered by this invoice falls under the regulation of the 1991 Water Industry Act, and you remain dissatisfied you can refer your complaint to Consumer Council for Water on 0121 345 1000 or write to them at Consumer Council for Water, 1st Floor, Victoria Square House, Victoria Square, Birmingham, B2 4AJ.

Ways to pay your bill

Credit Card BACS Payment Telephone Banking Cheque

Call 0845 070 9148 Account number By calling your bank and Made payable to ‘Thames quoting your invoice 90478703 quoting: Water Utilities Ltd’ number starting CBA or Sort code 60-00-01 Account number Write your Thames Water ADS / OSS A remittance advice must 90478703 account number on the be sent to: Sort code 60-00-01 back. Thames Water Utilities and your invoice number Send to: Ltd., PO Box 3189, Thames Water Utilities Slough SL1 4WW. Ltd., PO Box 3189, or email Slough SL1 4WW ps.billing@thameswater. or by DX to 151280 co.uk Slough 13

Thames Water Utilities Ltd Registered in England & Wales No. 2366661 Registered Office Clearwater Court, Vastern Rd, Reading, Berks, RG1 8DB.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 9 of 9 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 5 HAMPSHIRE CC GUIDANCE FOR DEVELOPERS, DESIGNERS AND PLANNERS.

GRAR/20-0018/FRA01

Surface Water and Sustainable Drainage Guidance for Developers, Designers and Planners

www.hants.gov.uk

Surface Water and SuDS Guidance

The purpose of this guide is to provide information on what Hampshire County Council as the Lead Local Flood Authority require developers, designers and planners to provide to support planning applications for new developments. Further information on our role as the Lead Local Flood Authority can be found at http://www3.hants.gov.uk/flooding.htm

What is Hampshire County Council’s role as the Lead Local Flood Authority within the Planning Process? We are a statutory consultee for major developments1 in relation to surface water drainage  We are not responsible for commenting on other matters and we do not determine the planning applications How are we consulted? We are consulted through the Local Planning Authority directly when an application is submitted for determination that meets the ‘major’ definition. We respond back to the Local Planning Authority, our statutory consultation period is 21 days.  Information should be submitted to the planning authority and should be clear and concise

Do we provide Pre-application advice? Yes, however there is a charge for this advice at pre-application, please see http://www3.hants.gov.uk/flooding/hampshireflooding/drainagesystems.htm and click on ‘Complete our online form’ to access the pre-application pro-forma

1 “Major development” means development involving any one or more of the following: 1) the winning and working of minerals or the use of land for mineral-working deposits 2) waste development 3) residential development: 10 dwellings or more, or residential development with a site area of 0.5 hectares or more where the number of dwellings is not yet known. 4) non-residential development: provision of a building or buildings where the total floorspace to be created is 1000 square metres or more, or where the floor area is not yet known, a site area of 1 hectare or more.

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General Principles of SuDS

Sustainable Drainage Systems (SuDS) are designed to mimic the natural drainage of surface water, typically managing rainfall close to where it falls. Surface water flows are then slowed down and The proposals for surface water drainage discharged at a controlled rate before it enters a watercourse. They can also store water, allow it to should be considered: soak into the ground or enable evaporation from surface. SuDS offer a wide range of benefits, as they can:  Early in the development process where this should consider the constraints to manage flood risk  the type and location of the use of these  maintain and improve water quality systems.  maintain and increase biodiversity  provide amenity and green open spaces Other key considerations are:  maintain groundwater recharge though infiltration  Layout of the proposals  Density SuDS features include; filter strips and swales, filter drains and permeable surfaces, infiltration  Topography devices and basins and ponds.  Ground Conditions  Discharge destinations The proposals should consider the location of discharge as a hierarchy, Planning Practice Guidance  Potential for multiple benefits states:

“Generally, the aim should be to discharge surface run off as high up the following hierarchy of drainage options as reasonably practicable:

1. into the ground (infiltration); 2. to a surface water body; 3. to a surface water sewer, highway drain, or another drainage system; 4. to a combined sewer.”

More information can be found in the links at the end of the document under the ‘Further information’ section.

What information do we request as part of a planning application submission?

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Why does this information need to be Level of detail for specific types of applications provided? Outline Full Existing Flood Risk Information on existing flood risk from This should be reviewed to ensure that surface  Yes  Yes modelled and historical sources water drainage features and SuDS measures are not Desktop assessment Desktop assessment and likely to be affected by existing flood risk. calculations where required SuDS Design Information on the proposed SuDS To show that SuDS have been properly considered  Yes  Yes Strategy within the layout and proposals for the development Information on the potential discharge To show that these have been fully considered  Yes  Yes points and locations including the within the SuDS Design and that the appropriate Full information on the sensitivity of those locations number of treatment stages have been provided Desktop assessment location and number of stages Existing Drainage of Information on the existing drainage To show that the design of the surface water system  Yes  Yes the site regime of the site including where has taken into account the existing low regime and Full information of the appropriate existing drainage locations that surface water is not being directed to a Desktop assessment existing regime including and networks different location without flood risk being affected runoff and discharge information Ground conditions Information on existing ground To be used in the design philosophy as well as for  Yes  Yes and infiltration conditions specific issues that may affect the surface water and Desktop assessment no specific Full hydrogeological SuDS Design tests required assessment including  Contamination that may affect the X No – unless known problem groundwater levels, use of infiltration devices infiltration tests, land  Ground investigation X No – Desktop assessment of contamination issues geology  Groundwater levels X No  Infiltration tests X No – Desktop assessment of infiltration potential Runoff calculations Information on the existing and To show that the proposals are not increasing flood  Yes  Yes proposed runoff rates and volumes risk off site Can be based on estimates of impermeable area and broad Full calculations proposals for surface water and SuDS design Attenuation Information on how surface water To show that appropriate attenuation is being  Yes  Yes flows and volumes will be contained provided and that this is in suitable areas Full calculations and detailed on site Broad estimate of volumes locations of attenuation Exceedance flows Information on what happens if the To show that a failure in the system would not lead  Yes  Yes and runoff in excess proposals exceed the design event to flooding on or off the site and would be contained Calculations to show the of design criteria on the site in a suitable locations Description of where these flows location of ponding or flow if are likely to be located the system overwhelmed

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Other things that you may need to consider

Whilst this is not an exhaustive list you may need to consider the following items when considering the surface water drainage and SuDS proposals on any new development.

Maintenance and securing this long-term

Ongoing maintenance of SuDS features and surface water drainage on any new development is an important consideration. Those proposing development will need to consider how the proposed systems will be maintained in the future and who will be responsible for this in the long term. It is recommended that the applicant has early discussion with the relevant authorities, organisations and groups that they are proposing become responsible for the scheme in the long term.

Local Planning Authorities should be satisfied that suitable ongoing maintenance and management of these systems are adequate and can be secured for the lifetime of the development.

Discharge Consents

The requirement to discharge into the water bodies is administered by the Environment Agency. The applicant should consider and check if their proposals require this permit at an early stage. Information on this can be found at https://www.gov.uk/environmental-permit-check-if-you-need-one/permits

Runoff to a watercourse

Where you are proposing to connect the surface water to a existing watercourse you may require a flood defence consent or a land drainage consent depending on the designation of the watercourse and the proposed works.

Where you are proposing to connect to a ‘main river’ you may require a Flood defence consent from the Environment Agency. If you are not sure whether the watercourse is designated as main river you will need to confirm this with the Environment Agency.

Where you are proposing to connect to an ‘ordinary watercourse’ you may require a Land Drainage Consent from the Lead Local Flood Authority (Hampshire County Council), further information on this can be found at http://www3.hants.gov.uk/flooding/hampshireflooding/watercourses.htm

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Permissions from third parties

You are also likely to require other permissions from third parties whose systems or land you are connecting to. For example you will need permission from private owners for connection into any private sewer systems, water companies for any connection to the public sewers and the Highway Authority for connection into the highway drainage network. It is the responsibility of the developer/applicant to secure the necessary permissions.

 Further information on SuDS

Susdrain – The community for sustainable drainage http://www.susdrain.org/

Non-statutory SuDS standards https://www.gov.uk/government/publications/sustainable-drainage-systems-non-statutory-technical-standards

Practice guidance for the English non-statutory SuDS standards http://www.lasoo.org.uk/non-statutory-technical-standards-for-sustainable-drainage

Rainfall Runoff management for developments http://evidence.environment- agency.gov.uk/FCERM/Libraries/FCERM_Project_Documents/Rainfall_Runoff_Management_for_Developments_-_Revision_E.sflb.ashx

National Planning Policy Framework http://planningguidance.planningportal.gov.uk/

National Planning Practice Guidance http://planningguidance.planningportal.gov.uk/

Flood and Water Management Team General enquiries relating to flooding – [email protected] Pre-application requests -http://www3.hants.gov.uk/flooding/hampshireflooding/drainagesystems.htm Surface water consultations – [email protected]

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The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

APPENDIX 6 RGP DRAINAGE CALCULATIONS

GRAR/20-0018/FRA01 Greenfield runoff rate estimation for sites www.uksuds.com | Greenfield runoff tool Calculated by: Chris Williams Site Details Site name: The Hideaway Latitude: 51.35848° N Site location: Pinks Lane, Baughurst Longitude: 1.16259° W This is an estimation of the greenfield runoff rates that are used to meet normal best practice criteria in line with Environment Agency guidance “Rainfall runoff management Reference: for developments”, SC030219 (2013) , the SuDS Manual C753 (Ciria, 2015) and 2368118365 the non-statutory standards for SuDS (Defra, 2015). This information on greenfield runoff rates may Date: be Apr 16 2020 18:48 the basis for setting consents for the drainage of surface water runoff from sites.

Runoff estimation approach IH124

Site characteristics Notes

Total site area (ha): 0.195 (1) Is QBAR < 2.0 l/s/ha? Methodology When QBAR is < 2.0 l/s/ha then limiting discharge rates are set at QBAR estimation method: Calculate from SPR and SAAR 2.0 l/s/ha. SPR estimation method: Calculate from SOIL type

Soil characteristics Default Edited SOIL type: (2) Are flow rates < 5.0 l/s? 4 4 HOST class: N/A N/A Where flow rates are less than 5.0 l/s consent for discharge is SPR/SPRHOST: 0.47 0.47 usually set at 5.0 l/s if blockage from vegetation and other materials is possible. Lower consent flow rates may be set where Hydrological characteristics the blockage risk is addressed by using appropriate drainage Default Edited elements. SAAR (mm): 727 727 (3) Is SPR/SPRHOST ≤ 0.3? Hydrological region: 6 6 Growth curve factor 1 year: 0.85 0.85 Where groundwater levels are low enough the use of soakaways Growth curve factor 30 years: to avoid discharge offsite would normally be preferred for 2.3 2.3 disposal of surface water runoff. Growth curve factor 100 years: 3.19 3.19 Growth curve factor 200 years: 3.74 3.74

Greenfield runoff rates Default Edited QBAR (l/s): 0.98 0.98 1 in 1 year (l/s): 0.84 0.84 1 in 30 years (l/s): 2.26 2.26 1 in 100 year (l/s): 3.14 3.14 1 in 200 years (l/s): 3.68 3.68 This report was produced using the greenfield runoff tool developed by HR Wallingford and available at www.uksuds.com. The use of this tool is subject to the UK SuDS terms and conditions and licence agreement , which can both be found at www.uksuds.com/terms-and-conditions.htm. The outputs from this tool are estimates of greenfield runoff rates. The use of these results is the responsibility of the users of this tool. No liability will be accepted by HR Wallingford, the Environment Agency, CEH, Hydrosolutions or any other organisation for the use of this data in the design or operational characteristics of any drainage scheme. 4/23/2020 Surface water storage volume estimation - member's only area Surface water storage requirements for sites www.uksuds.com | Storage estimation tool

Calculated by: Chris Williams Site Details Site name: The Hideaway Latitude: 51.35870° N Site location: Baughurst Longitude: 1.16256° W This is an estimation of the storage volume requirements that are needed to meet normal best practice criteria in line with Environment Agency guidance “Rainfall runoff management Reference: for developments”, SC030219 (2013), the SuDS Manual C753 (Ciria, 2015) and 3977240862 the non-statutory standards for SuDS (Defra, 2015). It is not to be used for detailed design Date: of drainage systems. It is recommended that hydraulic modelling software is used to calculate Apr 23 2020 20:38 volume requirements and design details before finalising the design of the drainage scheme.

Site characteristics Methodology

Total site area (ha): 0.119 esti IH124 Significant public open space (ha): 0.053 QBAR estimation method: Calculate from SPR and SAAR Area positively drained (ha): 0.066 SPR estimation method: Calculate from SOIL type Impermeable area (ha): 0.066 Soil characteristics Percentage of drained area that is impermeable (%): 100 Default Edited SOIL type: Impervious area drained via infiltration (ha): 0 4 4 SPR: Return period for infiltration system design (year): 10 0.47 0.47 Impervious area drained to rainwater harvesting (ha): 0 Hydrological characteristics Default Edited Return period for rainwater harvesting system (year): 10 Rainfall 100 yrs 6 hrs: -- 63 Compliance factor for rainwater harvesting system (%): 66 Rainfall 100 yrs 12 hrs: -- 90.86 Net site area for storage volume design (ha): 0.07 FEH / FSR conversion factor: 1.18 1.18 Net impermable area for storage volume design (ha): 0.07 SAAR (mm): 727 727 Pervious area contribution to runoff (%): 30 M5-60 Rainfall Depth (mm): * where rainwater harvesting or infiltration has been used for managing surface water runoff such 20 20 that the effective impermeable area is less than 50% of the 'area positively drained', the 'net site 'r' Ratio M5-60/M5-2 day: area' and the estimates of QBAR and other flow rates will have been reduced accordingly. 0.4 0.4 Hydological region: 6 6 Design criteria Growth curve factor 1 year: 0.85 0.85 Climate change allowance Growth curve factor 10 year: 1.62 1.62 factor: 1.4 Growth curve factor 30 year: Urban creep allowance 2.3 2.3 factor: 1.1 Growth curve factor 100 years: 3.19 3.19 Volume control approach Flow control to max of 2 l/s/ha or Qbar QBAR for total site area (l/s): 0.6 0.6 Interception rainfall depth QBAR for net site area (l/s): 0.33 0.33 (mm): 5

Minimum flow rate (l/s): 5

Site discharge rates Estimated storage volumes Default Edited Default Edited 1 in 1 year (l/s): 5 5 Attenuation storage 1/100 years (m³): 14 14 1 in 30 years (l/s): 5 5 Long term storage 1/100 years (m³): 0 0 1 in 100 year (l/s): 5 5 Total storage 1/100 years (m³): 14 14 This report was produced using the storage estimation tool developed by HRWallingford and available at www.uksuds.com. The use of this tool is subject to the UK SuDS terms and conditions and licence agreement, which can both be found at http://uksuds.com/terms-and-conditions.htm. The outputs from this tool have been used to estimate storage volume requirements. The use of these results is the responsibility of the users of this tool. No liability will be accepted by HR Wallingford, the Environment Agency, CEH, Hydrosolutions or any other organisation for the use of these data in the design or operational characteristics of any drainage scheme.

https://www.uksuds.com/drainage-tools-members/surface-water-storage-tool.html 1/1 The Hideaway, Heath End Road, Baughurst, RG26 5ND April 2020

GRAR/20-0018/FRA01