Weirs on our watercourses – a barrier to wildlife
SUNRISE Project Manager Richard Guy explains why weirs pose a problem for wildlife and disrupt the natural processes of a river.
The SUNRISE project is centred on connecting and improving natural habitats. Sometimes connection is achieved simply by removing a barrier, and when the habitat in question is a river, the most common barriers are weirs.
Weirs have been installed for many different reasons for hundreds of years, and come in a wide range of shapes, sizes and scale of impact. At the simplest level, a weir often creates a barrier which some species cannot pass, especially in reference to moving upstream.
The SUNRISE project will, by the time work concludes in Dec 2021, have removed, modified or bypassed six weirs or similar barriers on the River Trent or its tributary streams. This opens up long stretches of river or stream to species searching for appropriate habitats in upstream areas.
Weirs don’t just create a barrier, they also modify how the river flows, creating deeper, slower flowing sections behind them. By impounding water like this it restricts natural processes like sediment sorting and transport, and natural bank erosion, all of which are important in the healthy and natural formation of rivers. Removing weirs provides opportunities for these natural processes to start working in the river, creating more natural habitats.