Gareth Pedley, a conservation officer for the Wild Trout Trust, visited us on Saturday to run a brash banking workshop on the Killandean burn. It was a great learning experience for the RiverLife team and for our volunteers, who came from both the Avon and Almond catchments to learn about this method of green bank protection.
Bank erosion is a necessary and natural river process. It provides the river with sediment and gravels which are vital in the formation of habitat, for small fish and invertebrates, and spawning grounds for trout and salmon. Undercut banks, formed as a result of bank erosion, also provide great cover for fish while bare banks provide nesting grounds for sand martins. However, some factors, such as a lack of riparian vegetation and grazing up to the river edge, can result in excessive erosion which can call for some form of human intervention. Furthermore, if bank erosion threatens to damage infrastructure or buildings then it may be necessary to intervene and this was the case on the Killandean where a well used footpath may have been damaged if the bank continued to erode.
Brash banking is a method of green bank protection which diffuses flow and collects sediment, building the bank back up, before it is recolonised by vegetation. This is done by filling the eroded bank with brash and pinning it down using stakes, long branches and wire. As well as rebuilding the bank, a benefit of using brash rather than a hard barrier, such as stone, is that the scruffy edge of the brash provides habitat for small fish and invertebrates.
If vegetation does not immediately recolonise the new bank then we may return next year to thin the overhanging trees and plant some willow cuttings.
A big thanks to our volunteers for a hard days work and to Gareth for showing us how it is done. We look forward to seeing how this bank develops and to doing more green bank protection projects in the future.