Eat, Sleep, Restore, Repeat

Our volunteers were incredibly busy back in February 2020, carrying out River Restoration on the Beverley Brook and Wandle.

At the start of 2020, a new group of volunteer River Restorers came together to learn about natural river processes and how heavily modified waterbodies (such as the Beverley Brook) have been altered over time. These changes stop the natural processes which would usually shape a healthy river ecosystem, leaving us with a degraded river that has few, good habitats for wildlife.

Early in 2019, we carried out a large-scale restoration project along 1.3 km of the Beverley Brook through Wimbledon Common. Our River Restorer volunteers came on board to help us extend the work upstream – this time using people power alone!

We worked together to plan and design the work, ready to deliver as a team in mid-February.

Survey to show us the issues

Before the practical work, we also carried out surveys of the stretch to enable us to measure the change we make over time. We used a methodology called MORPh and our results are now shared online.

The survey results highlighted the problems this stretch of the river faces:

  1. Heavily over-shaded so that very little in-channel or bank-side vegetation was able to establish.
  2. Toe boarding constrained the river along both banks, preventing the natural processes of erosion and deposition.
  3. The channel was uniform and artificially straight leaving the river devoid of habitat and flow diversity.

Narrowing the channel

During two days in the river, our attention was focused on narrowing the channel by constructing an enormous brash berm.

To speed up the process of bedding in and becoming a natural extension of the bank, we decided to start work in an area where some trees had already been cleared to allow light in, which should help plants to thrive.

Beverley Brook River Restoration in Wimbledon Common © South East Rivers Trust

Brash berms slow the flow

Brash berms re-define the line of the bank, and when constructed in a sequence on alternating banks, help create a narrower, more natural, meandering channel.

The densely packed brash slows the flow of water through the berm, causing any sediment carried along by the water to drop out of suspension within the berm. With time, the berm will fill with silt and create a fantastic substrate for riparian plants to grow.

We transplanted some hardy sedge plants from elsewhere that will hopefully take root and speed up the naturalisation process.

Volunteers created brash berms © South East Rivers Trust

Removing toe boarding

Our berm altered the flow of water down the previously straight channel.

To allow the river to move naturally, we also removed many metres of toe boarding from both banks.

The finished work extends the restored section of the Beverley Brook through Wimbledon Common by another 50 metres.

Thank you not only to the volunteers but to Wimbledon and Putney Commons Conservators for their support of the project.

River Restoration, Beverley Brook

Morden Hall Park River Restorers

While preparing the Wimbledon Common River Restorers volunteer project, we were running workshops and surveys to carry out a similar project on the Wandle in Morden Hall Park.

Morden Hall Park is now owned by the National Trust but was once a deer park for a country estate. With the Wandle splitting into many meandering channels, the park remained as a green oasis throughout the river’s industrial heyday.

The River Restorers project within Morden Hall Park focused on part of the river that was artificially straight and very over-wide for the amount of water flowing along it. Due to these modifications to the channel, the stream power was insufficient to move small particles of sediment along the river and keep the gravel riverbed clean. This means the classic chalk stream gravels we’d expect to see were choked with silt and fine sand, making a poor habitat for invertebrates and spawning fish.

The Wimbledon Common river channel needed narrowing © South East Rivers Trust

Narrowing the channel

Our plan for restoration focused on narrowing the channel by creating brash berms and adding in pieces of large woody material to create a variety of riverbed features including deeper pools and shallow gravel riffles.

Across three days, we:

  • Created a very large brash berm to narrow the over-wide channel to two-thirds of its original width.

    Volunteers knocked in dozens of posts and removed some remaining toe-boarding.

  • Packed the berm with brash, to slow the flow of water – helping it to trap silt.
  • Installed a chunky wood deflector, finished the berm and transplanted clumps of sedge to kick start the vegetation process.
Volunteering

Thames Water funding

Thank you to Thames Water who funded both of these volunteer-led restoration projects through their Community Investment Fund.

Thames Water copyright

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