Name: Big Chalk
Price range: $

Lead organisation

Chilterns Chalk Streams Project

Partner organisations

Chilterns Heritage and Archaeology Partnership
Hambleden Parish Council
Private landowners

Project description

The Hamble Brook project has transformed part of one of the Chilterns’ winterbourne chalk streams, reinstating natural form, function, and connectivity to a river system untouched for more than 140 years. Over 18 months, the Chilterns Chalk Stream Project (CCSP) brought together the Environment Agency, National Trust, R.J. Bull Ltd, and local landowners to deliver work on more than 16% of the river’s length. This landmark effort stands as one of the largest winterbourne restoration projects ever undertaken in England, setting a new standard for what collaboration can achieve.

The work has re-naturalised 1,100m of chalk stream and 200m of connecting channels, reshaped online and offline ponds, removed two former weirs, and created two backwater sites. The project also delivered 2,500m² of new wetland, planted 60 native trees, and improved riparian connectivity along its length. Citizen Scientists are collecting Riverfly and Modular River (MoRPh) survey data, a long-term monitoring regime for the riparian landscape is being established and, with the support of Nottingham Trent University we are exploring how best to undertake dry-bed sampling.

Initially enabled by Heritage Lottery Green Recovery Challenge Fund support, the project leveraged £3 for every £1 of grant funding, demonstrating the power of partnership working. These efforts have already paved the way for feasibility studies on a larger downstream section of Hamble Brook, promising an even greater impact in the future.

The Hamble Brook restoration has been a journey of vision, planning, and hands-on delivery:

Mid 2020: First conversations with the landowner sparked the idea for restoration.
January 2021: An advisory report outlined the potential for transforming the chalk stream and its corridor.
April 2021: An application was submitted to the Heritage Lottery Green Recovery Challenge Fund to secure funding.
Mid 2022: The tender process began to select the design and build contractor.
March 2023: All necessary permissions were secured, clearing the way for work to begin.
March–May 2023: Channel restoration works were carried out, re-naturalising the stream and improving connectivity.
October–Decembber 2023: Wetland creation and native tree planting brought the surrounding habitats to life, completing the transformation.

This phased approach combined careful planning, collaboration, and on-the-ground action, delivering a landmark chalk stream restoration that will be monitored and celebrated for years to come.

Project location

Hamble Brook winds through the southern part of the Chilterns National Landscape between Henley-on-Thames and Marlow. The project focused on a rural stretch between Pheasants Hill and Skirmett, a classic chalk stream corridor wholly contained within the Big Chalk programme area.

Contribution to Big Chalk

By restoring the stream’s natural form, the Hamble Brook project has recreated a diverse habitat mosaic capable of supporting a wider range of species, including winterbourne specialists such as the scarce purple dun mayfly and the winterbourne stonefly. Clean gravels, deeper pools, and wetlands will provide refuge and breeding sites for birds and aquatic life, while a balanced sun-and-shade regime supports temperature control and species migration.

Coupled with a grazing and management plan, these works ensure the chalk-stream character is not only restored today but resilient for the future, even through dry periods. A comprehensive monitoring regime—expanding beyond MoRPh and Riverfly surveys—will track how channel, wetland, and grassland species respond over time, offering vital data to inform further landscape-scale nature recovery across the Big Chalk area.

Hamble Brook stands as a landmark example of what partnership, ambition, and science-led restoration can achieve—bringing a chalk stream back to life for people, wildlife, and the wider landscape.

A serene countryside scene featuring a narrow, shallow stream bordered by green grass and patches of dry, yellowish reeds. The stream reflects the surrounding trees and sky. In the background, there are rolling hills with scattered trees and a wooden fence running parallel to the stream. The sky is overcast, giving the image a calm and peaceful atmosphere.

A serene landscape featuring a small, clear stream flowing through a lush green meadow. The stream is surrounded by tall grasses and various plants, with trees in the background under a bright blue sky. The scene is peaceful and natural, showcasing the beauty of the countryside.

A clear, shallow stream flows through a grassy field with trees on the right side. The trees have white blossoms and green leaves. The sky is bright blue with no clouds. In the background, there are more trees and a small hill.

An aerial view of a lush green landscape featuring a winding stream with multiple branches. The stream flows through dense vegetation and grassy areas, surrounded by trees and patches of open land. The water appears calm, reflecting the greenery around it.

Do you have a project that could strengthen the future of southern England’s iconic chalk and limestone landscapes?

The Big Chalk programme brings together a dynamic suite of partner-led projects, each unique in its focus, area, and partnerships but sharing a commitment to our collective vision.

If your project contributes to the Big Chalk mission, we invite you to register it as a Big Chalk Project. Registered projects gain access to networking, shared learning, and best practice—alongside the Big Chalk brand, boosting your profile and connecting you to a powerful, growing network of partners.

Together, these projects form a united effort to secure the future of southern England’s chalk and limestone landscapes, making a lasting impact for nature and communities.