Thames21 has begun restoring part of the river Cray, a chalk stream, at Foots Cray Meadows near Sidcup, south London. We aim to restore 800m of the river between now and March 2021 by adding large wood into the channel.
Chalk streams are a rare habitat globally; only approximately 200 exist worldwide. Eighty-five per cent of these are in southern England. The river Cray is a healthy urban chalk stream along part of its stretches, but it suffers the same pressures as any other urban river: plastic and other pollution, artificial modification and water abstraction for human use.
The stretch of river Cray we will restore at Foots Cray Meadows sits within a well-used public park. It has become over-wide, over-shaded by trees and its riverbanks have been eroded (poached) by walkers and dogs. Our river restoration work will encourage natural processes and a healthier river: more ‘wiggly’, with different depths and water speeds, and with more plants at the river’s edge providing better habitats for invertebrates, fish, birds and other wildlife.
The works involve felling some of the smaller trees growing on the riverbank and adding these to the river. This will narrow the channel and encourage features such as pools (deeper, slow-flowing areas) and riffles (faster, shallow areas) to develop. We will also add flow deflectors, which push the water in different directions to encourage these features, and fill in existing features with woody brash to trap silt and leaves and provide opportunities for plants to grow. We will encourage more riverside plants to grow by removing some of the overgrown shrubs, allowing more light to reach the riverbank.
We have also trained citizen scientists to carry out Modular River Surveys (MoRPh surveys), a tool to record physical river habitat features which indicate how healthy the river is. The results of these surveys will help us to better understand the impacts of the river restoration work.
Read more about the benefits of adding large wood to rivers in our latest blog.