Policy paper

Sanway-Byfleet flood alleviation scheme

Updated 3 April 2023

Applies to England

See our new information page with the latest updates.

Background

Byfleet and Weybridge have experienced notable floods in 1968, 2000 and 2003. In 2013/14 prolonged heavy rainfall resulted in flooding from the River Wey. A total of 74 properties were flooded.

Following the most recent winter 2013/14 flood, the Environment Agency reviewed options to reduce flood risk in the Byfleet and Weybridge area.

The options considered

The Environment Agency has looked at a number of options, including:

• a permanent wall in the waterfront gardens of properties at Wey Road
• road raising and permanent defences protecting properties at Wey Meadows
• a combination of permanent flood walls, gates and embankments to protect properties in Byfleet at Brooklands Road, Viscount Gardens, Weymede and Weyside Close, Plough Bridge Farm and Parvis Road
• a combination of a permanent flood wall and embankment to protect the residential area around Sanway Road, Byfleet
• individual property-level protection (such as flood barriers on houses) in Byfleet and Weybridge
• upstream storage at seven locations in Weybridge and Byfleet

The appraisal identified an economically viable scheme for the Sanway-Byfleet area. We will investigate separately the scheme options for other areas of Byfleet and Weybridge.

Read the Byfleet and Weybridge Flood Alleviation Scheme page for more information.

Sanway-Byfleet Flood Alleviation Scheme

The proposed flood defence for the Sanway area includes a combination of flood walls and flood embankments (permanent defences). The proposed defence ranges from 0.15m to 2m in height so where the land is low lying the defence will be higher. The western end of the defence will tie into the M25 embankment next to Broad Ditch. This will run east in Common Meadow along the rear boundary of properties in Fullerton Road and the Sanway area. The defence will then run northwards to protect properties in Summer Close before ending on higher ground.

This essential scheme aims to better protect from flooding from the River Wey up to 236 properties in the Sanway area of Byfleet taking into account climate change. This scheme is designed to provide a standard of protection of 1 in 100 chance of flooding in any given year. This takes into account the effects of climate change. This means that in any one year there will be a 1% chance that the Sanway area will experience flooding.

Our current flood defence proposals include:

• sheet pile flood wall from the M25 to the southern end of Sanway Road
• earth embankment flood defence between the southern end of Sanway Road and Summer Close
• 3 compensatory floodplain storage areas
• a normally dry overflow channel west of the M25 between the Broad Ditch and the River Wey
• improvements to surface water drainage pipes that run underneath the flood defences - to ensure flood water cannot bypass the defences through these pipes - opportunities to reduce surface water flood risk will be developed in the next stage of the project

Figure 1: Sanway area likely flood defence route

This map shows the likely flood defence route and the areas that need compensatory floodplain storage.

There are areas to the north of Manor Farm where the ground is lowered by up to 0.8m and 1.6m. There is another area south of the River Wey and Common Meadows where the ground is lowered by up to 2.3m. These areas are compensatory floodplain storage areas.

The height of flood defences running along Manor Farm and Common Meadows can go up to 2.4m, depending on how low the ground is. There is a dry overflow channel in the area to the west of the M25 and between Thames Water sewage treatment works.

Over the past few years the Environment Agency has been working with partners to develop this scheme.

Partners include:

• Woking Borough Council
• Surrey County Council
• Surrey Wildlife Trust
• National Highways
• Thames Water
• Byfleet Flood Forum
• the local community

We have carried out computer modelling and are designing the scheme to reduce flooding to properties in the Sanway area. Flood defences that protect people, homes and businesses act as barriers to flood water. Therefore, we need to create areas nearby for the displaced flood water to go without increasing flood risk elsewhere. These areas are known as compensatory flood storage areas and are included in the scheme.

We have run community engagement events in March 2021 and May 2022. At the May 2022 engagement event, over 70 residents attended the drop-in and took the time to provide us with very valuable feedback. Residents asked questions and provided feedback on several key areas. There were queries raised on the flood defence proposals and on the environmental enhancements. These enhancements will provide significant extra benefits for residents and wildlife.

We have considered all the responses made and are taking these into account in the further development of the scheme.

There remains overwhelming support for the scheme. All the households which expressed a preference in their written feedback said they strongly agreed or agreed with the proposals.

We now have approval of the preferred option for the scheme and are moving to the next stage which is detailed design and planning permission.

Environmental benefits

We held a workshop on potential environmental benefits that the new flood scheme could create. Fifty people attended, including:

• Councillor Amanda Boote
• local residents
• landowners
• environmental experts
• local council officers
• the Environment Agency

Attendees discussed the River Wey floodplain from Broad Ditch to the west of the M25, downstream to Byfleet Road Bridge. Attendees came up with ideas that included:

• a new footpath through this area
• a mosaic of wetland habitats on Common Meadows with opportunities for landscaping
• improving fish passage in the River Wey
• lowering water levels at Byfleet Mill
• the suggestion to try and bring the water vole back to Surrey (where it is currently extinct)

We have developed these suggestions and other ideas in discussion with landowners and the community. However, all proposals are dependent on funding.

Environmental enhancement and improvements are now proposed to include:

• increased diversity of habitats within Common Meadows and Manor Farm
• enhancement of existing grassland areas to more distinctive grassland habitats (for example, lowland meadow)
• creation of wetland features and ditches linked to the River Wey and increased marginal planting along the riverbanks
• providing a net increase in length of hedgerows within Manor Farm - this is currently under discussion with Surrey Wildlife Trust
• creation of pockets of wet woodland (woods that occur on ground that is often or seasonally wet)
• enhanced provision and connectivity of footpaths within Common Meadows and to the wider footpath network both west of the M25 and northeast into Manor Farm
• improvements to M25 underpass – improve daytime lighting, repainting and removal of fencing

At the May 2022 engagement event, feedback on the environmental enhancements included:

• impacts on security, privacy and potential disruption due to the use of the new footpaths
• reducing impacts on existing wildlife and trees

It also included comments on planting, footpath types, community involvement and keeping a wild look to the area. Residents were keen to see signage provided. We have considered these responses and are taking them into account in the further development of the scheme.

Timescales

We now have approval for the options appraisal stage of the project. This is where a range of options have been evaluated using engineering, economic and environmental criteria. We have approval for a single preferred option we engaged on in May 2022 to be delivered.

You can see our proposals in more detail online. Visit our new information page to find out more and have your say.

Based on comments and feedback we receive, we will amend our plans where feasible.

Now that the preferred design option is approved, we are starting the next stage of the project which is the detailed design and planning permission. Once all approvals are in place including full business case approval then construction can start.

Provided the scheme is fully approved and funded, the earliest construction could be completed is winter 2025/26.

Funding

The scheme requires partnership funding. We have agreed this funding in principle. Now we have outline business case approval, we are proceeding to the next stage which is detailed design and construction.

The flood alleviation scheme will use a mixture of funding from:

• central government
• Thames Regional Flood and Coastal Committee
• county and local councils

The cost of the scheme will depend on the detailed design process. Based on current information, we anticipate the scheme will cost in the region of £20 million.

Get involved

Our most recent public engagement events were held in March 2021 and May 2022. The Resident magazine has also published articles to keep people updated. We are planning to run further public engagement events during 2023. We use these events to gain useful local knowledge and understand the priorities of the local communities. We will take your feedback into account by changing our plans where feasible before we submit our planning application.

We have set up a new information page to give more frequent scheme updates. Please do continue to give us your feedback. We are keen to hear your views at any time and not just during publicised engagement events.

Contact

For further information, or to provide feedback please contact THM.Schemes@environment-agency.gov.uk.