Helping restore fish and endangered eel populations on the River Blackwater

Langford Weir Fish Pass

Eels have been disappearing from our rivers in recent years, and the European Eel is one of the most endangered freshwater fish species in the UK. To help restore local wildlife and support national efforts to increase eel populations, Essex & Suffolk Water asked our team to design a new fish and eel pass alongside Langford Weir on the River Blackwater.

Our team surveyed the site and created the design for the construction of an 18-metre (59-foot) long pass to provide a safe route around the weir, allowing species to move freely upstream and downstream. We designed the pass to suit the river’s layout and the species most likely to use it. It includes two channels—one fitted with textured tiles to help eels and elver (young eels) climb upstream, and another with two flights of Larinier baffles and a central resting pool to allow fish to swim upstream. The structure is fed by gravity and carefully designed to keep water flowing at the right velocities for different species. A waterproof camera has been installed at the intake to the fish pass to monitor the number and diversity of fish using the pass.

The weir is in a conservation area, so we took careful steps to protect the local area and surrounding riverbanks. Our design called for the use of low carbon concrete and reuse of materials wherever possible to further reduce carbon emissions and waste. We collaborated closely with the Environment Agency throughout the construction to manage flood risk, water quality, and habitat protection.

The new pass will support healthier fish and eel populations, reconnect river corridors, and help boost biodiversity along the River Blackwater for years to come.