The River Cleddau in South West Wales is an important spawning tributary for migratory fish. The Cleddau is a mobile gravel bed river of moderate to high energy and in the demonstration area has a history of instability and planform adjustment.

Traditionally, blockstone revetments would be used in higher energy rivers to control bank erosion. However, blockstone removes any scope for marginal grasses and trees to establish, thus lowering the ecological value of the river and also reflects the flow of the water, which causes additional instability downstream.

As part of a three-year project, entitled ?Fishing Wales? the Environment Agency Wales were keen to demonstrate that softer bioengineering methods could be used to control the extensive erosion, whilst maintaining geomorphological processes, and enhancing the physical habitat of the river. The aim of the demonstration was to show that bioengineering techniques can be used as an alternative to blockstone in mobile gravel bed rivers to control erosion whilst restoring physical habitat to degraded channels and thus helping to guarantee the sustainability of fish stocks in Wales.

Salix undertook a detailed geomorphological survey which was in turn used to inform the detailed design plan. Several bioengineering techniques were employed based on the local reach scale erosion process, water depth and stream power. In areas with low stream power these included bank grading and toe protection using live willow bundles (faggots/fascines), whilst in areas with greater erosive energy whole upturned tree roots with 2 metres of trunk still attached were installed to act as physical revetments and also deflect flow away from eroding banks. All the trees used were grey willow (Salix cinerea) and as such have started to grow providing excellent habitat and cover. In addition the entire reach was fenced in order to keep livestock off the banks.

The project has been very successful and demonstrates the use of sustainable river management techniques.