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 most recent 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 to produce an Initial Assessment to confirm whether there are any potential viable options to address flood risk. The appraisal identified an economically viable scheme for the Sanway area in Byfleet.

The scheme now aims to better protect from flooding up to 236 properties in the Sanway area of Byfleet taking into account climate change which is larger than the number we have shared previously.

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. 

Sanway-Byfleet during the 1968 flood

Modelled flood risk May 2022

The below map shows the current likelihood of flooding in the area. This shows the impact of a 1 in 100 chance of flooding in any given year, taking into account the effects of climate change. This means that in any one year there will be a 1% chance that the area will experience flooding. You can also download a PDF of the plan. The below map shows the current possibility of flooding for the area. You can also download a PDF of the plan.

We have been developing the scheme over the last few years and are now in the options appraisal stage where we identify our preferred option.

We ran our first public engagement event in February 2019 and the second in March 2021.

For the February 2019 engagement event, we were able to meet face-to-face and held 2 local drop-ins to share our initial proposals for reducing flooding across a larger area of Surrey, which included Byfleet and Weybridge. You can download a copy of the boards used at the events here. 

The March 2021 event included a website and virtual public meetings held on Zoom. At that time, we shared our proposals for the Sanway-Byfleet area in particular. You can download a copy of the slides used at the events.

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

The plan below shows our previous flood defence proposals from March 2021 in the Sanway-Byfleet area. You can also download a PDF of the plan.

Previous flood defence proposals from March 2021

 

Since March 2021 we have:

General

• Refined and developed our flood defence route – including specific engagement with Fullerton Road residents to determine the preferred type and location of the flood defence (wall vs embankment).
• Identifying the preferred locations for the required compensatory floodplain storage areas (which will hold the flood water that is displaced by the flood defence to prevent flood risk increasing elsewhere) – since previous engagement these have changed with an additional location to accommodate the revised flood defence route.
• Introduction of a normally dry overflow channel west of the M25 between the Broad Ditch and the River Wey – this is required to ensure flood risk does not increase to properties upstream of the scheme. 
• Refined and developed environmental and recreational improvements at Common Meadows – this has been combined with the flood defence proposals to produce our landscape proposals. 
• Continued engagement with landowners affected by scheme – Woking Borough Council, Surrey Wildlife Trust, RHS Wisley, National Highways (formerly Highways England) and Thames Water.
• We are proposing a new footpath to connect Common Meadows and Manor Farm. This offers a significant benefit to the area as these two areas are currently separated. 
• We are looking at sustainable opportunities to manage surface water flooding in the Sanway-Byfleet area as part of this scheme.

Broadoak Weir and Fish Pass

• We have been investigating options for the installation of a fish pass at Broadoak Weir which would open up 10km of the River Wey to fish.
• The work does not provide any flood risk benefits but would provide environmental enhancements which could be funded from other sources.
• The Sanway-Byfleet Flood Alleviation Scheme could be an efficient way of delivering the work.
• Additional work may be needed to establish costs and benefits but this may take time.
• If necessary, the fish pass work can be separated from the Sanway-Byfleet Flood Alleviation Scheme so that it does not delay the main scheme.

Broad Ditch 

• There are some improvements to Broad Ditch that are likely to be delivered as part of the flood alleviation scheme. These are a bridge, footpath and improvements to the M25 underpass. These works form part of the environmental improvement proposals of the flood alleviation scheme.
• The Environment Agency has limited funding for maintenance, and we therefore prioritise our maintenance work on rivers to reduce flood risk for people, homes and businesses. Removing fallen trees and other debris does not always meet the criteria for clearance work unless this causes a blockage in a high flood risk area.
• For these reasons, most of the work required on Broad Ditch is likely to be delivered separately from the Sanway-Byfleet Flood Alleviation Scheme so that the scheme is not delayed.

Byfleet Mill Weir and Fish Pass

• Byfleet Mill Weir is nearing the end of useful life and needs refurbishment or replacement.
• Byfleet Mill Weir is also a barrier to fish being able to migrate upstream. We would like to install a fish pass to open up 22km of the River Wey to fish.
• We have assessed a range of options for what we could do at Byfleet Mill Weir including replacing the gates with fixed weirs at various levels and refurbishing the gates. 
• We listened to the feedback you gave us during and after the March 2021 engagement events that many of you were not supportive of lowering water levels.
• In terms of flood risk, the costs of the options are greater than the benefits. This work will therefore by undertaken separately from the Sanway-Byfleet Flood Alleviation Scheme so that it does not delay the main scheme.
• You also said that you were keen to ensure that the main flood alleviation scheme was not delayed should the works to Byfleet Mill Weir be delayed. Separating the schemes also takes this feedback into account.
• The work at Byfleet Mill Weir would therefore be better developed and delivered separately from the Sanway-Byfleet Flood Alleviation Scheme.

 

 

 

 

 

 

To reduce flooding from the River Wey, we propose to install a combination of flood walls and flood embankments (known as a flood defence). Embankments and flood walls protect homes by acting as barriers to flood water up to the standard of protection provided.

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

The flood defence will not increase flood risk to other areas because the scheme will also involve the creation of new areas of “compensatory floodplain storage”, which will hold the flood water that is displaced by the flood defence.

The defence is designed to provide a standard of protection of 1 in 100 chance of flooding in any given year, taking into account the effects of climate change. This means that in any one year there will be a 1% chance that the 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.
• 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 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.

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

 

We aim to mitigate the adverse impact of the proposed scheme on the environment, for both:

• • Construction stage – vegetation clearance, disturbance to local community, air quality and noise impacts.
  • Operational stage – permanent changes to landscape, including some of habitat.

As well as mitigating the adverse impact of the proposed scheme, we are required to provide improvements that achieve a minimum of 10% biodiversity net gain in each of the three components (terrestrial habitats, hedgerows, and rivers) to achieve planning permission.

We will aim to deliver more than 10% biodiversity net gain, where it is cost-effective to do so.

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.

In January 2020, we held a workshop focused on potential environmental benefits the scheme could create. 50 people attended, including local residents, the Byfleet Flood Forum, landowners, environmental experts, the Environment Agency, local councillors, and local council officers.

Following this, we have been working on various options for creating community and environmental opportunities. 

Environmental enhancement and improvements are proposed to include:

• • Increased diversity 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 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. 

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.

The diagram below shows the current landscape proposals for the Sanway-Byfleet area. The diagram has been annotated with numbers which correspond to location of the views shown below. You can also download a PDF of the plan. 

 

The economic 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 

The cost of the scheme includes:

• Cost for detailed design and planning application (including further surveys)
• Cost to construct the scheme
• Cost to maintain the scheme into the future over the next 100 years
• Contingency allowance for increases in costs as the scheme develops 

Based on current information, we anticipate the scheme will cost in the region of £15 million to £20 million.

Sanway-Byfleet Flood Alleviation Scheme funding 

We have agreed funding in principle. Once we have Outline Business Case approval, we can progress this flood alleviation scheme to the next stage which will be detailed design and planning permission.

Woking Borough Council and Surrey County Council are proposing substantial contributions for both the flood alleviation and environmental enhancements for the scheme.

• Confirmation of preferred option for Outline Business Case
• Preparation of Outline Business Case 
• Outline Business Case approval (Decision to start detailed design / planning application)
• Start of detailed design
• Public engagement before planning application
• Submit planning application
• Planning application approval
• Other consents granted
• Full Business Case approval (Decision to award construction contract)
• Start construction / environmental enhancements
• Finish construction / environmental enhancements

 

Target Dates

The following dates subject to stakeholder agreement, planning permission, funding approvals and construction risks:

How to take part

• You can contact us at any time by:
• email at THM.schemes@environment-agency.gov.uk
• telephone at 03708 506 506
• post at Sanway-Byfleet FAS, Kings Meadow House, Kings Meadow Road, Reading, RG1 8DQ