The next indoor meeting of the Chesham Environmental Group is on Thursday 23 August 2012 at 7.30pm at the Chesham Town Hall. If you have any items for the agenda, please contact the Chairman Phil Folly direct – email follypostman@aol.com or visit email www.cheshamenvironmentalgroup.org.uk.
The Sunday working party on 19 August 2012 at 10am will be attended by the Chesham Town Mayor Cllr Colette Littley. They will be positioning river flow deflectors in the River Chess below Cannon’s Mill and tidying up the area. Flow deflectors are the Environmental Group’s main project. They are used to push the flow of water into the middle of the river to scour and clean the bed. They provide a refuge during high flows and also create a spawning habitat for fish. They can be made of different things.
Kathryn Graves of the Chesham Town Council told me, ‘Quite a few are made of woody debris, which helps to give a fairly natural appearance. You can see a good example here. Vertical stakes are used to hold the debris in place. A deflector is used to pinch the flow, creating a turbulent flume and back eddies. This will scoop out a pool in the stream bed and heavier gravels get thrown up downstream to make a riffle. Back eddies deposit silt on the shoulders below the deflector and the slow glide does the same along the edges above. These shoulders colonise with plants. A uniform, straight and dredged channel is made dynamic and self healing.’
Editor Merrin Molesworth.