Slowing the flow

Slowing the flow

Dorset Wildlife Trust

Volunteers have been helping with work being carried out by contractors and Dorset Wildlife Trust staff on the River Hooke in the Kingcombe National Nature Reserve to install 14 woody leaky debris dams.

The main function of the dams which lie across the channel of the Hooke as well as its smaller tributaries is to slow the flow of water when river levels are high after extreme rainfall. Over time, the dams will accumulate additional natural material that comes downstream such as leaves and twigs but will remain leaky so that the water can flow through. Such structures then become a haven for invertebrates but their main function is to slow the flow of the river in spate events and force the water to go outside the main channel to create lots of smaller new channels.

This work on the River Hooke will help both wildlife and people in a number of ways. Renaturalising the river and allowing it to become a multi-thread channel with lots of different niche habitats will support a wider range of aquatic invertebrates and fish.  Water spilling out of the main channel also helps connect the river with its floodplain - making the adjacent grassland wetter for longer which is again beneficial for wildlife. In terms of benefits for people, if enough of these types of structures are created within a river, along with other Natural Flood Management measures in the wider catchment, peak flows can be reduced, thereby reducing the risk of flooding in villages and towns downstream.

After the leaky dams had been installed, there was a flood event at the end of March 2022 in which water was pushed out sideways from the River Hooke cutting new channels and creating new habitat for wildlife.

Our thanks go to the contractors, Casterbridge Fisheries and the Environment Agency for funding the work.

Find out more about natural flood management