A lot of our projects recently have been large scale – removing weirs, installing fish easement solutions and reprofiling large sections of river. But now it was time for the real professionals to step in…
For one week in March, Toby and I were in chest waders in the Hogsmill in Ewell. Over 5 days, we were joined by volunteers from the Lower Mole Project and other local volunteers from the Hogsmill Pollution Patrol and the Wandle – all trying river restoration first hand.
The River Hogsmill is a chalk stream in south London where we’ve been working to increase habitat connectivity over the last few years. Toby has been busy removing weirs where possible, or installing rock ramps to make them passable to fish.
In Ewell, Toby removed 3 small weirs to open up fish passage throughout this 1.6 km stretch. What was missing was fish habitat.
So what did we do?
The Hogsmill through the Open Space is artificially straightened and canalised with wooden toeboarding. There is little habitat variation in channel with slow moving water and a silty bed.
On the first day, a team of volunteers got stuck in pulling out the large railway sleepers serving as toe boarding. Over the next four days, a total of 48 sleepers were removed – the first step in naturalising the bank for 1km through the park.
Meanwhile, carefully-selected trees were felled to increase light reaching the river. With this material, we started to create brash berms to narrow the channel and increase flow.
A holding log was placed at the downstream end of the berm and secured in place with posts and wires. Then brash from the surrounding areas was added to build up a berm.
This was all secured in place with chestnut posts and wire across the brash after some technical “squishing”…
Over the next four days, the volunteers created a further 8 berms. You can see from the photos that the river began to respond instantly. Flows were increased where the channel was narrowed and scoured pools started to form.
On the last day we moved our attention further downstream to the site of a weir removal in 2014. Here a small weir and concrete abutment walls were reduced, but due to the close proximity of the path had to leave a semi-engineered bank.
To enhance this, pre-planted coir rolls were fixed along the bank to soften this edge and create a more natural marginal habitat.
To install these though was no simple task. They were secured in place with chestnut stakes and wire thread round the posts and through the mesh of the bank line. Believe me, that was a skill in itself…
Here are some photos of what we all achieved..
Big thanks to everyone who came along!! We’d also like to thank Epsom & Ewell Borough Council and the Lower Mole Project.