With the assistance of a dedicated team of local volunteers, Bristol Avon Rivers Trust (BART) has been working to restore the river habitat along Patchway Brook, a tributary of the Bristol Frome which flows through the Three Brooks Nature Reserve in North Bristol.
This urban stream has been significantly altered over time, primarily functioning as a conduit for rapid water flow. Consequently, it has become disconnected, concealed, and depleted of vital habitat that supports resident fish and aquatic life.
The unnaturally widened and straightened channel lacked depth and varied habitats across its cross-section, offering minimal shelter for small fish species and invertebrates. Flow conditions were slow and uniform, with the riverbed covered in silt, smothering the riverbed gravel. Additionally, sections of the brook were excessively shaded, blocking sunlight from reaching the water and impeding the growth of aquatic plants (macrophytes), reducing habitat diversity and the available niches essential for aquatic life to flourish.
Between January 2024 and March 2024, 16 brushwood berms were added to a 1km reach of Patchway Brook, a tributary of the Bristol Frome. Brushwood berms are woody structures built in the river to encourage natural processes and increase flow and habitat diversity for river wildlife.
To build the berms, a team of volunteers assisted BART, many from the local Three Brooks Conservation group. The team were briefed how to position the brushwood for the berms including learning how to undertake the work safely and using correct techniques. Small branches were collected and tightly packed behind the main deflector arm. The woody deflectors were positioned in the channel in suitable locations to encourage natural processes to begin creating new good quality habitat. The structures were secured to the riverbed and banks to create a series of pinch points to diversify flow conditions and in channel habitat throughout the stretch of river.
During periods of increased flow in the brook, the brushwood berms will become submerged, potentially staying underwater for extended durations, possibly even months. As water rushes over and through these berms, they will trap fine sediment, gradually accumulating to extend the riverbank at a lower level. Over time, these berms will become self-sustaining, enhancing the river’s cross-sectional diversity by forming deeper pools in areas with the swiftest flow and clearing silt from the riverbed, which is essential for creating habitats for fish. Moreover, the berms will create marginal habitats, a feature often missing in many of our rivers. As they trap silt and grow vegetation, these berms will provide valuable new habitats for a variety of wildlife, including mammals, birds, and insects.
A big thank you to South Gloucestershire Council for granting permission to BART to carry out the works throughout the council’s land and to the Three Brooks Nature Conservation Group for their support and assistance.
