PROJECT

Chamber Mead Wetlands

We have completed a series of wetlands to help conserve the Hogsmill River – a much-loved chalk stream. This includes cleaning 250 million litres of water through natural systems to combat pollution.

This project is part of a wider partnership between the Rivers Trust and The Coca-Cola Foundation to help clean some of Britain’s most polluted rivers, reduce flood risk, and to create new wetland habitats in both rural and urban locations across the country, replenishing 1.6 billion litres of water.

Wetlands are a haven for wildlife such as heron. Image by 16081684 from Pixabay

Delivery completed

2024

Project update Spring 2024

The main bulk of the construction work was completed in February 2024. The newly created wetlands swiftly attracted wildlife and provided a benefit to the Hogsmill River downstream.

We would like to thank everyone who came to the wetlands launch day in April, plus the volunteers, including from groups and schools, who added approximately 10,000 plants to the edge of the water in spring. It was great to celebrate the wetlands with the community and to give people the chance to get involved with adding the vegetation that will be key to helping them become a haven for wildlife.

The project doesn’t stop here and SERT will be monitoring the wetlands to assess their performance. We will also be working with Epsom and Ewell Borough Council to rectify any small tweaks which may be needed over time.

Big, new sites like these always take time to bed in after completion. We will continue to see development over the coming months and years. We continue to appreciate your support and patience.

The weather has meant the ground has been very wet and boggy until early spring. With the weather improving, a contractor will come and smooth the ground outside the stock fencing. This will be seeded with a wildflower mix.

The green plastic barrier fencing will remain in place to allow the grass to establish, so that the area can be enjoyed without it becoming muddy. Once established, this area will then be accessible to the public.

Contractors will be out in early May to finish the bridge, sloping the footpaths up to it so there is no step, which can be hazardous. Once complete, the bridge will be accessible to all.

Geese can be a nuisance when wetland plants are first put in, so fencing has been placed to try to protect all of the plants while they take root.

We hope residents can take enjoyment from the site and from seeing how it progresses while nature takes hold more and more!

Flow along the Hogsmill upstream of the wetlands is particularly strong at the moment, following the long period of wet weather, meaning the stepping stones have been under water. We expect the water level to drop as we approach summer, but will keep checking them regularly.

Volunteers adding plants to the wetlands

Project overview

Now the wetlands construction has been completed:

Water will flow along the Green Lanes Stream, but instead of running straight into the Hogsmill River it is being diverted through a sediment trap and two wetlands. At the other end, the wetland is connected into the Hogsmill River, downstream of the stepping stones
As they develop, the wetlands will add variety of habitat and amenity benefit to the Hogsmill Local Nature Reserve, as well as improve water quality for a 200 metre section of rare chalk stream
A footbridge over the newly created channel will offer continued access around the Chamber Mead area for members of the public. The footbridge is close to the stepping stones
In April and May 2024, the wetlands were planted with a range of diverse plant species, informed by a wetland specialist. The banks of the wetlands will be fenced off to protect the wetlands and to give plants time to establish. The wider open space will remain accessible to the public
Information boards about the project have been be added to the area
Some vegetation removal was necessary to allow the works to go ahead. A number of trees will also be planted as part of the project. These include disease-resistant Elms, which will benefit a local population of White-Letter Hairstreak butterflies.

An aerial view of Chamber Mead wetlands

Why the Hogsmill?

The Hogsmill River is a cherished chalk stream in south London. Flowing through the Hogsmill Local Nature Reserve in Ewell, the river is very popular with families and dog walkers.

Chalk streams such as the Hogsmill are globally rare habitats, of which there are estimated to be only 210 worldwide. These special rivers give rise to a unique set of species that depend on the clean, chalk-purified water and are very sensitive to pollution.

Sadly, the Hogsmill has poor water quality – suffering pollution from a range of sources.

A poo-luted river

The Green Lanes Stream tributary joined the Hogsmill a few hundred metres downstream from its source. This tributary brought a cocktail of pollution, receiving road runoff from Epsom town centre and nearby industrial areas.

During heavy rainfall the river can also impacted by discharges of untreated sewage and stormwater from the Epsom Storm Tanks.

This pollution is not only a threat to the chalk stream but also poses a public health risk to children who play in the river and to dogs and their owners.

Polluted water from the Green Lanes Stream entering the Hogsmill chalkstream © South East Rivers Trust

Wonderful wetlands

Wetlands are a nature-based solution to improving water quality. Water that drains through wetlands is gradually filtered by plants and captured in the soil, intercepting and treating pollution.

The Chamber Mead Wetland has been created to do exactly that. It intercepts the Green Lanes Stream, filtera and cleana the water through a series of wetlands before rejoining the Hogsmill with cleaner, safer water.

Wetlands provide multiple benefits. They sequester carbon, provide flood storage, mitigate the impacts of droughts by storing water in the landscape, and boost biodiversity.

Image by Meatle from Pixabay

A partnership project

Chamber Mead Wetlands is a collaborative project led by the South East Rivers Trust. Our partners include the Hogsmill Catchment Partnership, the Environment Agency, and Epsom and Ewell Borough Council.

The partners completed a feasibility study investigating how water quality from the Green Lanes Stream could be improved at the same time as improving open space within the Local Nature Reserve for people and wildlife.

The favoured option involved diverting the Green Lanes Stream through Chamber Mead meadow. The new channel follows a winding path, passing through a constructed sediment trap and wetlands, before entering back into the Hogsmill river approximately 200 metres further downstream.

The construction of the wetland is expected to cost £1 million. We are proud to have a good mix of funding for this project, including private funding from Coca Cola, Thames Water and charitable grants, as well as public funding from the Environment Agency, Natural England and Surrey County Council. We worked with Five Rivers to construct the wetlands.

What changes will be brought?

As the site develops, the project will bring multiple benefits to the Hogsmill’s health and ecology, through varied habitat and increased biodiversity, benefiting public health and boosting local amenity value.

The project will result in:

Improved water quality
Reduced risk to health from contaminants and sewage based pathogens
An extra 200m of un-impacted chalk stream habitat
Up to 2,000m² of wetland habitat created
Enhanced aesthetic value and reduced visible pollution
Outdoor educational opportunities for local schools
Improved community amenity with the new wetlands forming an attractive addition to the Hogsmill Local Nature Reserve.

Image by 16081684 from Pixabay