Policy paper

River Wey: weirs refurbishment and fish pass scheme

Updated 6 May 2021

The River Wey can be navigated by boat, on natural and man-made sections, along the ‘Wey and Godalming Navigations’. These navigations were constructed under Acts of Parliament in 1651 and 1760. By 1935 Surrey County Council had made improvements along the River Wey, to reduce flood risk and maintain navigation.

This was achieved by installing a series of new weirs and bypass channels and channel improvements under the River Wey Improvement Scheme.

Complementary weir and fish pass works for flood control and fish passage

Today the navigations are owned and operated by the National Trust. The Environment Agency has some responsibility for maintaining the navigation.

They have inherited ownership of 18 weir and associated structures from Farnham to the Thames at Weybridge. This River Wey weirs refurbishment and fish pass scheme was set up to focus on 7 of these weir sites.

These sites needed urgent refurbishment and replacement. After completion, this project will reduce flood risk to 388 residential and 236 non-residential properties.

Fish passage improvements

Despite their benefits, weirs present a major barrier to fish trying to move upstream. This is a big problem for species such as salmon and trout which migrate between the sea and gravel dominated headwaters of our rivers. It is also an issue for resident species.

These need to move freely in the river in order to feed, breed and adapt to pressures such as pollution, flooding and climate change.

In order to address this and improve the ecological health of the river, this project is installing fish passes on or adjacent to 5 of the weirs.

At one site, a new 170m long channel is being created around the weir. The channel will allow fish to bypass the weir but it will also attract other wildlife. On other sites where there isn’t as much space, more technical solutions are being built into the existing weir structure. These will help break up the flow and allow fish to move up and over the weirs.

These fish passes are contributing to a much larger partnership initiative, known as the Wey Fish Pass and Wetland Delivery (FWD). The first phase of this with the weirs scheme will open up over 100km of river to fish. This is between the Thames at Weybridge and the Wey at Tilford. This will help to deliver Water Framework Directive (WFD) objectives. The WFD is a European Directive which aims to improve our rivers for both people and wildlife.

How the scheme works

The scheme is designed to continue maintaining navigation water levels whilst improving reliability.

It complements other Environment Agency schemes such as the River Wey flood alleviation and the Fish Pass and Wetland Delivery (FWD) schemes.

This scheme is a partnership project working and liaising with:

• landowners and occupiers
• the National Trust
• Surrey County Council
• Guildford Borough Council
• Woking Borough Council
• Elmbridge and Runnymede Borough Councils
• Wisley Golf and Weybridge Boat Clubs

Building on our sympathetic refurbishment of 6 weirs in previous years, we are now constructing 3 complementary fish passes in 2021 to 2022. This follows re-programming and preparation in the winter to finalise designs, permissions, and environmental/safety plans.

Figure 1 – The completed weir and walkways at Newark Weir

For the Hamm Oils Fish Pass, adaptive structures will be retrofitted to an existing bypass channel with 2 weirs in Weybridge, Surrey. This channel joins the River Thames at the lower weir (below left). It is the most important link improve fish passage between the Wey and the Thames.

The lower weir will be repaired in the same profile to support a Larinier fish pass unit. This approach will safeguard the protected London Plane tree alongside, which is over 300 years old and a London landmark. The Larinier unit will be similar to the Abbey Fish Pass (below right), completed last year. This now blends smoothly with the weir pool.

Figures 2 – Lower weir at Hamm Oils and an example of a Larinier unit at Abbey Weir

The Walsham Fish Pass shown with the channel route shown below is a naturalised/hybrid brush channel. The construction on this busy public site began last year. The channel will be 170m long and replicate a natural stream. It will be planted with a variety of plants and the bed will be lined with gravel to provide valuable habitat where fish can lay their eggs.

An outlet section with fish brushes and walls will slow the water down so that fish can migrate. The base structures have now been completed. Work will finish in 2021 by constructing the channel and carrying out landscaping.

Figure 3 – Walsham fish pass channel route

Figure 4 – Millmoor Stream Weir

For the Millmoor Fish Pass (above) in Old Woking we aim to retrofit a double width Larinier eel pass into this 1930s pool pass. This will improve passage.

This project:

• has completed replacement of all but one of the six historic 1930s River Wey Improvement Scheme flood weirs
• includes 4 to 5 fish passes along the River Wey in Surrey
• helps protect 388 homes from flooding
• opens up 47km of the river to the Thames for fish and eels for the first time in centuries.

The wider aim is to open up 100km and create habitat through co-delivery with the River Wey FWD Project on other partnership sites. The project team includes:

• the Environment Agency Operations Asset Performance Team and Fisheries, Biodiversity and Geomorphology Team
• TVO Mackley - contractor
• Jackson Hyder, Fishtek and Doctor Hassinger - Site Supervisor and Designers
• Arcadis UK - Contract Project Manager and Cost Management
• the National Trust - own the navigations and are a key partner

Where and when will the work happen?

Weir/structure	Location	Date of completion
Hamm Oils Weir	Weybridge	Completed in 2018 to 2020
Walsham Weir	Pyrford	Completed in 2018 to 2020
Newark Weir	near Ripley	Completed in 2018 to 2020
Bowers Weir	Burpham	Completed in 2018 to 2020
Broadmead Weir	Old Woking	Completed in 2018 to 2020
Abbey fish pass (near Abbey Weir)	near Ripley	Completed in 2018 to 2020
Walsham fish pass	Pyrford	Structures completed in 2018. To be finished in 2021.
Millmoor Weir Stream fish pass	Old Woking	July to September 2021
Millmead Weir and fish pass		Fish pass design to be confirmed in 2021. Construction possible from April 2022.

The most suitable time for construction in the river is between 1 April and the 31 October. This includes the summer when river levels are at their lowest, and daylight hours longest.

Funding

The cost of the scheme will be close to £13 million. This includes the design and construction of the weirs and the associated weir structures and fish passes with a risk budget. The Environment Agency is largely funding the scheme using Capital Grant. Partnership working and funding is possible for the Millmead fish pass delivery.

What happens next - Coronavirus

TVO (Mackley) are the construction contractor. Following risk assessments and control measures, we are continuing with the next phase of construction from April 2021. Jackson Hyder and Arcadis are managing the design and construction contract. All licenses, consents and planning approvals have been obtained in 2020 to 2021.

Contact

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