Natural Flood Management
Leaky dams are a Natural Flood Management (NFM) technique using woody materials to create a leaky barrier within a channel. They can occur naturally as a result of trees falling into a watercourse, created by animals such as beavers or man-made.
Benefits
The leaky dams hold water behind them only allowing a small amount to flow through. They reduce maximum flood peaks by increasing the amount of time it takes for rainwater to flow downstream.
Silt and debris is trapped behind the barrier reducing sediment input to the watercourse. Silt contains nutrients such as Nitrate and Phosphate which can be harmful to aquatic life.
Woody dams provide a variety of habitats including pools and protection for fish and invertebrates and birds can use them for basking, perching and as nesting sites.
Case Studies
Fazakerley Brook
The Fazakerley Brook Leaky Dams were built by Mersey Rivers Trust staff, volunteers and the Friends of Bluebell Woods in March 2023. Woody material was sourced from within Bluebell Woods, some of which had already fallen into the brook. It is hoped that the dams will help to slow the flow into the River Alt to help reduce flood risk downstream and improve water quality in the brook.
This project was funded by the Environment Agency.
