BART has installed a series of ‘leaky dams’ that will help contribute towards slowing the flow of the small tributary of the Winford Brook during medium to high flow events. By imitating natural tree fall across the channel, the leaky dams will hold back water, allowing the stream to fill its channel capacity and in places, reconnect the adjacent floodplain.
The structures have been designed to allow base-flow to pass beneath the structures so that connectivity of water, sediment and aquatic biota can is not impacted during average to low flow conditions. In effect, the leaky dams will only function during higher flow conditions.
Acting as human beavers, BART’s operatives harvested local timber from the densely vegetated banks of the stream and strategically secured the timber limbs across the channel in locations where there are opportunities to reconnect the floodplain and create backwaters. The structures were constructed in a way that allows some water to ‘leak’ through the dams so that the stream does not become impounded. Harvested timber was stacked in as natural a way as possible to blend in with the surrounding environment. The leaky dams were secured in place using chestnut posts which were hammered into the bed. Steel wire was used to secure the timber to the chestnut posts, but BART minimised the use of wire by utilising natural anchors on the banks to hold them in place.
BART installed a total of four leaky dams throughout this reach as the first phase of an Environment Agency funded project. The next phase will involve the creation of an in field bund to temporarily store surface water and flood waters from the stream at the bottom of a steep sided field. As well as temporarily storing water, the bund will also reduce the quantity of sediment that is currently washed away from the field and into the watercourse – thus improving water quality of the stream.
BART plan to raise funds to deliver several other schemes that have been identified through BART’s catchment wide survey work including landowner engagement that was funded by Bristol Water throughout the Winford Brook catchment.
The accumulative affect of multiple small-scale interventions such as this scheme, could benefit the health of the Winford Brook and deliver multiple benefits to both people and the environment.
If you wish to find out more about this project, please get in touch with Project Manager, Simon Hunter at simon@bristolavonriverstrust.org.
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