Sanway-Byfleet Flood Alleviation Scheme

Byfleet has experienced several notable floods in 1968, 2000 and 2003. Recently, in 2013/14 prolonged heavy rainfall resulted in flooding from the River Wey and a total of 74 properties were flooded.

Following the winter 2013/14 flood a high-level meeting was held between the Environment Agency and Surrey County Council.

The Environment Agency agreed to review options to reduce flood risk at several locations in the Byfleet and Weybridge area and identified an economically viable scheme for the Sanway area in Byfleet.

The scheme now aims to better protect up to 236 properties in the Sanway area of Byfleet from river flooding, taking climate change into account.

Sanway-Byfleet area, 1968

Byfleet has a long history of flooding, with a large flood in September 1968 causing significant damage to properties along the River Wey. It was one of the largest floods seen in this area and was estimated as being a 1 in 200 chance of flooding. 

The below image shows a snapshot of the flood in the Sanway-Byfleet area in 1968.

Modelled flood risk May 2022

The maps below show the current likelihood of flooding in the area without a scheme and future flood risk with alleviation measures.

Flood risk without alleviation measures

Flood risk with alleviation measures

Our surveys

We have carried out a range of surveys and investigations to improve our understand of the area and inform our designs. These are summarised in the table below.

Flood walls and embankments

To reduce flooding from the River Wey, we propose to install a combination of flood walls and flood embankments. These protect homes by acting as barriers to flood water.

The flood wall and embankment will range in height depending on whether the land is low lying. The western end of the scheme ties into the M25 embankment next to Broad Ditch and runs east in Common Meadows along the rear boundary of properties in the Fullerton Road and Sanway Road area. It then runs northwards to protect properties in Summer Close before ending on higher ground.

The wall and embankment will not increase flood risk to other areas because the scheme will also involve the creation of new areas of floodplain storage”, which will hold the floodwater that is displaced by the flood wall and embankment.

Our current scheme proposals include:

• Sheet pile flood wall from the M25 to the southern end of Sanway Road.
• Earth flood embankment between the southern end of Sanway Road and Summer Close.
• Three 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 embankment, to ensure flood water cannot bypass them.

The plan below shows the proposed alignment of the flood wall and embankment and the areas where we require compensatory floodplain storage. You can also download a PDF of the plan. 

Sanway-Byfleet Flood Alleviation Scheme proposal

Environmental improvements

While the aim of the scheme is to reduce flooding, we also have an opportunity to deliver some wider benefits to the community and the natural environment in the area.

Environmental improvements may include:

• Increased biodiversity of habitats within Common Meadows and Manor Farm.
• Enhancement of existing grassland areas to more distinctive grassland habitats (i.e. 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 (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 and bridleways within Common Meadows and to the wider network both west of the M25 and northeast into Manor Farm.
• Improvements to M25 underpass - improve daytime lighting, repainting and removal of fencing.

We have identified a range of measures necessary to protect the environment and local communities before and during construction and once the scheme is in place. For example, minimising noise, checking air quality and traffic flow impacts. We are also going to provide habitat improvements and aim to achieve a 20% biodiversity net gain in each of the 3 components: terrestrial habitats, hedgerows, and rivers.

Example photo of riverbank enhancement on the River Wey

Before construction begins, we must make sure that all approvals, such as planning permission, are in place. Provided the scheme is fully approved and funded, the earliest construction could be completed is winter 2025.

What will the scheme look like?

The diagrams below shows the current landscape proposals for the Sanway-Byfleet area.

Sanway-Byfleet Flood Alleviation Scheme landscape plan: October 2023

Proposed landscaping plan for Common Meadows: October 2023

Aerial view of Common Meadows

Artist's impression view of Common Meadows towards Fullterton Road

Artist's impression of entrance to embankment from Muddy Lane

Artist's impression of the flood embankment north of access from Fullerton Road

Example of recently constructed flood embankment at Marlow. Pictures A and B show an embankment, and picture C shows the access path over the embankment.

Floodplain storage area

Artist's impression of Manor Farm floodplain storage area

A floodplain storage area is where the ground levels will be lowered to provide space for floodwater that is displaced by the construction of the flood wall and embankment.

The land will be reseeded to provide enhanced grassland increasing biodiversity.

Embankment design

The sketch above shows how the embankment will be constructed. This includes the flood wall, soil and piling rig. Water held back by the flood embankment will slowly seep through the soil coming out on the dry side of the embankment. To stop this, we will install an impermeable 'cut off' through the embankment into the ground below. Our preferred method to create the 'cut off' will be to mix in the ground the existing soil with cement to create an impermeable wall.

The photos show the typical equipment used for soil mixing. Similar equipment will be used for the flood alleviation measures in this project.

The working hours for construction of the scheme are 08:00 to 18:00 Monday to Friday. We will be working across all areas of the construction site. While there may be times when construction is not visible, we will still be working on that area.

We will do everything we can to reduce disruption like using the most up to date technology, looking at options to reduce vehicle movements ad putting up site boards and fencing to reduce visual and noise effects.

The benefits of the scheme include:

• Better protection from flooding of people and properties in Sanway.
• Improved recreational access to Common Meadows and Manor Farm.
• Biodiversity and habitat improvements.

Based on current information, we anticipate the scheme will cost in the region of £18 million to £20 million. The cost of the scheme includes:

• Detailed design and planning application (including further surveys).
• Construction of the scheme.
• Maintenance of the scheme over the next 100 years.
• Contingency allowance for increases in costs as the scheme develops.

The Environment Agency, Surrey County Council, the Regional Flood and Coastal Committee and the national government are all making considerable contributions to the scheme. 

The following dates are subject to stakeholder agreement, planning permission and funding approvals.

Public engagement

We have been developing the scheme over the last few years and are now in the detailed design stage where we have identified our preferred option.

We ran a public engagement event in autumn 2023, with previous events in May 2022, March 2021 and February 2019.

We have used feedback from these events to inform the development of the flood alleviation scheme.

We have also issued newsletters to keep the local community informed of scheme progress.

• January 2024 newsletter
• September 2023 newsletter
• July 2023 newsletter

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