On one of the brighter September days, the Surrey Wildlife Trust Nature-based Solutions team donned their waders and joined Wetlands Officer Josh Bowes to create a berm along the Chertsey Bourne. The team were excited to get stuck into this aspect of the project, which has now been running for a number of years. The initiative has resulted in improvements for wildlife and greater habitat diversity within the stream.

For a few members of the team, it was their first experience of undertaking a river restoration project, and was a great opportunity to understand more about river processes and the important role rivers play in a healthy ecosystem. Upon arrival we were treated to a tour of the previously completed restoration works, and saw examples of berms, deflectors and gravels, and impact they can have. This project is now in its second phase, with a third phase currently in development.

A brash berm, in this case, is essentially a bend (meander) in the river which is made from woody off cuttings. The berm has many purposes, including encouraging water to flow at different rates, introducing diversity to the stream, helping to trap silt and sediment - reducing the flow of materials – and providing an additional habitat for marginal plants. It’s also a haven for smaller fish, helping to avoid predation, and as vegetation grows on the berm, further habitats will be established.

Once we had our waders and life vests on, it was time to enter the water! In case of emergency, it’s important for someone to stay on the riverbank at all times with a throw rope at the ready. We marked out the size of the berm using pre-cut stakes to make sure the berm was big enough to make an impact on the stream, but also an achievable task to be completed in one day.

After getting the size of the berm right, the team went about coppicing some of the smaller Alders, Aspen and Ash along the bank. This was for 2 reasons – to let more light into the stream to allow vegetation to grow on the new berm, but also to provide materials for weaving through the posts.

Once we had the coppiced material, we went about weaving the posts together. We weaved through them and then pushed the branch to the bottom of the stream, repeating the action until the branches reached the surface of the water. We then went about filling the inside of the berm using brash, holding the brash underwater as we piled more on top to ensure it would all be filled.

To make the most of the existing trees on the bankside, the team decided to include a hinged tree in the berm - this uses techniques from hedge laying, and the team were able to use their skills developed during their hedge laying training to do this. One of the trees was partially cut and then laid at the front of the berm, remaining alive. This will allow the ash to continue to grow into the berm – ash trees are great for coppicing and tend to grow well afterwards, and the tangle of branches from the tree provides an ideal habitat for juvenile fish.

Once the berm was filled, we used the larger trunks from the coppicing – which we weren’t able to weave – to lay across the top of the berm and hold all the brash in place. We then used rope to tie the material down to the posts and stop it from washing away, securing it in place with staples before bashing the posts in place to ensure the structure was secure.

At the end of the day, the team could already see the impact the berm was having on the stream and felt that the hard work had all been worth it.