Project overview
We’ve created a series of wetlands at Chamber Mead to help restore the Hogsmill river, a rare and much-loved chalk stream in Surrey.
Using natural processes, these wetlands are already helping to treat 250 million litres of water, improving water quality before it reaches the river.
Part of a wider national partnership, this work also contributes to restoring rivers, reducing flood risk and creating new wetland habitats — helping replenish 1.6 billion litres of water.
Project impact
Completed in February 2024, the wetlands quickly began supporting wildlife and improving the river.
- Around 10,000 plants were added by volunteers, schools and local groups
- Wildlife began returning within weeks
- In July 2025, around 50 water voles were reintroduced as part of a national species recovery programme supported by Natural England
We continue to monitor the site and work with partners to ensure it performs effectively as it develops.
What this project delivers
As the wetlands mature, they will:
- Improve water quality
- Reduce health risks from pollution and sewage
- Create up to 2,000m² of wetland habitat
- Enhance 200 metres of chalk stream habitat
- Boost biodiversity and climate resilience
- Provide outdoor learning and community space
An aerial view of the Chamber Mead wetlands © DEFRA
How it works
Water from the Green Lanes Stream is diverted through a sediment trap and wetlands instead of flowing directly into the Hogsmill.
As it passes through:
- Pollution is filtered by plants and soils
- Sediment is captured
- Cleaner water returns to the river downstream
The site also includes a new footbridge, planting, and interpretation boards to support access and learning.
Why the Hogsmill matters
The Hogsmill is one of only around 210 chalk streams worldwide, supporting unique wildlife that depends on clean water.
However, pollution from road runoff, urban areas and storm overflows has impacted its health — affecting both wildlife and people using the river.
A nature-based solution
Wetlands offer a powerful, natural way to improve water quality.
They:
- Filter pollutants
- Store water and reduce flood risk
- Support wildlife
- Help rivers adapt to climate change
At Chamber Mead, the wetlands intercept polluted water before it reaches the Hogsmill — helping restore a cleaner, healthier river.
Wild flowers growing alongside the Chamber Mead wetland © South East Rivers Trust
Working in partnership
This project is led by the South East Rivers Trust, working with the Environment Agency, Epsom and Ewell Borough Council and the Hogsmill Catchment Partnership.
Delivered by Five Rivers, the £1.1 million project is funded by a mix of public and private partners, including Coca-Cola, Thames Water, ZSL, Garfield Weston Foundation, Natural England and Surrey County Council.
Help rivers and wildlife thrive
Support projects like the Chamber Mead wetlands that improve water quality, create habitats for wildlife and restore healthier rivers for local communities.
