Last week, Luke and I were lucky enough to spend three days on the Beverley Brook in Wimbledon Common.
Like many rivers, the Beverley Brook has been modified over time to fit into our more developed urban landscape. Within Wimbledon Common, the river has been over straightened and reinforced with wooden toe boarding. As a result the flow of the river has become very uniform and lack the diversity needed for water biodiversity.
To address this we started a project to install Large Woody Material (LWM) into the river channel. LWM replicates a natural occurrence of trees and branches falling into rivers which then provides habitat for fish and invertebrates. The use of LWM in the right places can transform a still, slow-moving river into a highly diverse river channel with a variety of habitats for all life stages of fish and invertebrates.
Over the three days we had a number of volunteer helpers to help us move the timber logs, position them within the channel and fix them in place with hazel stakes and wire.
Luke and Lawrence led the event, explaining how the positioning of the logs effected the flow of the river and could influence bank erosion. For example, if we placed a log facing downstream, this forced the flow of water into the bank creating a natural meander bend. Natural gravel deposits held in the bank will scour out and become available in-stream for fish and invertebrates.
So working as a team, over three days we worked out where the logs would be of most benefit and got to work securing them in place.
It was hard work. Moving the large logs took four people and was still a struggle. However once they were in the river, they became a lot lighter. Once positioned, each log had to be secured with four hazel posts which were forced into the ground using a post knocker – another exhausting piece of equipment.
Once surrounded by hazel stakes, the logs were secured further with wire to be sure they were going nowhere in a flood.
In total we installed 17 LWM structures along a stretch of 200 m, approximately. Here are some photos to show you how the still slow-moving channel has now been transformed!
Many thanks to all the volunteers for coming: Charles, Dave, Denisa, John, Keith, Kristina, Lawrence, Mark, Mike, Paul, Phil, Rob, Sue and Wally.