River Mole – Leatherhead

Background Information

The River Mole at Leatherhead, Surrey between Thorncroft Bridge and Common Meadows is one of the most publically accessible stretches of the River, with a mixture of open spaces, industrial and economic uses.

The river here is slow-flowing in places, overwide and has deeply incised banks. These areas provide little habitat variation for invertebrates and fish. Due to the nature of the public space, some areas of the bank had become heavily eroded due to dog walkers trying to access the water.

Scope of the Project

The area is an important, accessible open space, valued for both wildlife and recreation: walking, fishing and bird watching. Being a public space, it was of utmost importance to minimise disturbance to the surrounding area and its users.

The project aimed to improve aquatic habitat diversity for wildlife, fish and invertebrates, improve the flow variations within the watercourse and create access points to the water’s edge where massive soil erosion had already occurred.

Working in partnership with Surrey Wildlife Trust, the River Mole Catchment Partnership and the Environment Agency several problem areas were identified.

The works involved the creation of two public access points/dog dips to the water’s edge, the installation of a planted wetland berm, the installation of two log deflectors, a brushwood berm and the erection of 150mm of post and rail fencing and gates.

Our Solution

To prevent further bank erosion at popular access points to the water’s edge, two sets of timber steps were installed to encourage access for dogs and members of the public.

A vegetated wetland berm constructed from Hazel Faggots was installed adjacent to the right-hand bank on Bluebird island, where the river was slow flowing and deep to narrow the over wide river channel and introduce habitat.

A tracked excavator was used to re-profile the bank behind the newly installed berm, and locally sourced native aquatic plants were planted to kick start the establishment.

Further in-channel habitat was created in the form of a brushwood berm approximately 10m in length, on the inside of the bend on the right bank, upstream of Thorncroft Bridge. Two downstream pointing flow deflectors were also installed on the right bank to reduce the erosional pressures on the sheet piles on the left-hand bank.

Approximately 150m of post and rail fencing was erected parallel to the river, aiding the establishment of an un-grazed buffer zone that will create habitat and help stabilise the eroding banks. The fence was a post-and-rail type, to keep livestock out but allow the free flow of floodwaters. A five bar gate was installed for access to the buffer zone for the local angling club and essential bankside maintenance.