Using green techniques to reduce river bank erosion

The River Teith is one of the defining features of the local landscape and town. As part of the Rivers project, Forth Rivers Trust explain the river bank erosion work that is planned for later this year.

Map showing location of brash bank workThe map shows an area of the river undergoing restoration, close to the cycle path and hay meadows. Here, erosion is getting out of control. If this continues, wet meadow habitat will be lost, and there will be a potential impact on the adjacent footpath and cycle route.

We are acting now to use green techniques to slow the erosion, until trees can be established along the bank to protect it into the future.

What is brash banking?

Brash banking uses natural material to mimic mother nature by creating a woody cushion in front of the eroding river bank. Using conifer branches, fence posts and willow, the brash is packed and woven between the posts which are set just out from the bank, about one metre apart. Brash (conifer branches) are then packed tightly between the bank and front woven woody wall to create the cushion. This cushion allows water to still reach the river bank but reduces the flow speed – meaning less erosion.

The brash is a great habitat for wildlife as it starts to collect silt which is being carried by the river and deposited in the slower moving water as it travels through the brash. Live Willow is woven into the brash so that it can start to grow and set roots into the bank. These roots help bind the soil and stop further erosion in the future.

Brash bank in progress at Allan Water

An example of brash banking at Allan Water.

Brash banking eventually decomposes and is used as a temporary (5-10 year) solution to reduce the rate of erosion, but tree planting will also be carried out along the top of the river bank to create a web of roots, stabilising the bank for future years.

Want to get involved?

We will be installing around 49m of brash bank protection along the section impacted by erosion. We hope to start this work in May and will be looking for volunteers to help (restrictions permitting). Follow us on Twitter or Facebook, or join our mailing list, to keep up-to-date about our volunteering opportunities.