Approximately 30 years ago a ‘by-pass’ was added to the Bourn brook in Cambridgeshire as it was believed it would help the river flow. This has recently proved to be incorrect and instead increases flood risk downstream. The CRT was, awarded a grant for £2,000 from the Rigdeons Family Charity Fund to restore the meander loop to its rightful glory making a new home for wildlife.
Restoring the meander will increase the amount of water in the river channel at times of high flow, and will slow the passage of water downstream, thus increasing the holding capacity of the river channel in an area where the water is beneficial to wildlife habitats, and decrease the quantity of water heading downstream where it would increase damage during flood events in the Cam catchment, potentially including the city of Cambridge. Previously, the current straightened channel offered little refuge for fish and invertebrates at times of high flow, whereas a meander has areas of slack water even at full river capacity, and these areas help aquatic wildlife to survive. The old meander channel still exists, and currently goes through an area of woodland; when the brook floods (which it regularly does), this area will therefore produce an area of wet woodland, a priority habitat under the national Biodiversity Action Plan; wet woodland is home for a variety of declining wildlife species including fungi, amphibians, invertebrates and birds.
For the last 100 years or so it was normal activity for meander loops in brooks and streams to be by-passed so water could run more freely and quicker off the land.. More recently it has been discovered that this quicker running water is actually more likely to cause flooding where the brook meets the larger river network, often causing major problems where the natural floodplain has been built on for our towns and cities. The water can also run too fast for a aquatic wildlife to survive major flood events.
Dr Vince Lea, CRT Monitoring Officer said “I have been wanting to do this work for nearly 10 years, so I’m delighted! Thank you to the Rigdeons Family Charity Fund for their help with this project which will hopefully benefit the local community and increase the wildlife in the brook.”
The grant from the Ridgeons Family Charity Fund was administered by Cambridgeshire Community Foundation, whom everyone at the CRT would also like to thank.
Dr Vince Lea went on to say “Interesting to see the impact of our work on the Environment Agency monitoring station just downstream of the site; you can see a clear dip where the river stops going the short cut and starts to fill the old channel once again. Once it is flowing round the old river course the gauging station shows the level is back up again to the normal height”. See below
So we are excited to report that the old meander is now back in action, and we have dammed off the short-cut created 30 years ago.
Images to follow!