- 1st June 2021
- Posted by: Dom Senior
- Category: Projects
Location: Gayle Beck Client: Ribble Rivers Trust
The Ribble Rivers Trust (RRT) identified that the Gayle Beck in the Yorkshire Dales had insufficient fish habitats and was unable to support the sustainable migration of fish. As such, the Gayle Beck was failing the Water Framework Directive for having poor Ecology. The RRT commissioned JBA Consulting to investigate potential river restoration options to improve fish habitat and passage.
We undertook hydraulic modelling to assess the impact of adding woody debris features into Gayle Beck. Woody debris has been successfully used on a number of river restoration schemes across the UK, as they have been proven to increase habitat diversity in rivers. The installation of woody debris within a river provides a wide range of enhancements, from slowing down the flow of water, encouraging gravel deposition, trapping organic matter and providing shade. These offer excellent benefits for fish by providing migration routes, additional habitats and spawning locations, and a wider range of food sources. Different combinations of woody debris were represented in the hydraulic model to assess the impact that this would have on the flow regime and sediment movement patterns across a 300m reach of the Gayle Beck.
The addition of woody debris in the channel creates a greater diversity in flow velocities, generating areas of high and low velocity. This will lead to areas of sediment erosion where the channel is constricted, and sediment deposition directly downstream where the channel widens and flow velocities reduce.
The model results indicate that fish will benefit from the following:
- A greater range of flows facilitates improved fish migration
- bed scour generates pool features in the channel, creating a valuable fish habitat
- Sediment deposition generates bar features and riffles, a valuable fish habitat