As part of our Green & Active Project, we are very happy to be working with Thames21 on a river monitoring initiative for a stretch of the River Cut. As part of this project, we have been running various tasks at Garth Meadows focussed on activities such as cutting back overgrown plants along the rivers edge, creating access points to the river, improving walkways, and monitoring water conditions.
We are now ready to start the next phase of this project, which will be to add seven large wood flow deflectors and four brash berms into the river, as well as removing a rock weir.
Flow deflectors are essentially large pieces of wood positioned on an angle facing upstream, with one end pushed tightly into the bank. The timber stretches across roughly one third of the river and creates turbulence in the water, especially in mid-stream. This turbulence then scours out the riverbed creating a hollow with a gravel bank downstream. This can help to sort through, or ‘clean’, the gravel which in turn helps to create better conditions for certain river flora and fauna.
Brash berms re-define the line of the bank, and when constructed in a sequence on alternating banks, help to 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 plants to grow.
Weirs can affect rivers in various ways. They degrade the quality of the river habitats because by creating an impounded area upstream, with less natural water flow, which in turn can stop natural processes such as sediment transport. This then disrupts and fragments wildlife habitats and can have an overall negative impact on river ecology and biodiversity. Therefore, removing the rock weir will help to solve all of these issues.
As always, suitable clothing and footwear is required, but depending on each day’s duties, you may also need to locate some waterproofs if river wading is on the cards! You can contact the Thames21 team beforehand to ask about the specifics of each event, or if you’re ready to get involved, you can sign up online. Also, if you’re not already signed up as a volunteer for the Green & Active Project, please complete a Registration Form before attending.