Background
Areas of Winchester experienced severe flooding in 2014, prompting a review of the city’s flood defence plans. Hampshire County Council has developed a Flood Alleviation Scheme to manage the flow of river water in order to protect Winchester city centre, and local homes and businesses from high water levels.
The River Itchen is a classic chalk river and is a Special Area of Conservation (SAC), supporting high densities of protected aquatic species including white-clawed crayfish, southern damselfly, bullhead, Atlantic salmon, brook lamprey and otters.
Scope of services
RSK Biocensus was commissioned to provide specialist aquatic ecology support in relation to the Winchester Flood Alleviation Scheme, including:
- Walkover assessments to identify aquatic constraints and to describe the ecological baseline, following the Environment Agency’s River Habitat Survey technique and the Hendry and Cragg-Hine salmonid assessment criteria.
- Input to an Environmental Statement.
- Close liaison with the client, engineers and the Statutory Nature Conservation Bodies.
During the construction works, a series of fish rescues
were undertaken using electric fishing, with a particular focus on lamprey, a qualifying feature of the SAC.
We also identified and agreed receptor sites with Natural England, produced an Environmental Management Plan covering the mitigation process and implemented offsite mitigation to offset net loss of aquatic habitat.
Impact
Our responsive, local aquatic team provided essential support to the client, allowing them to adhere to their planned works program for flood alleviation. Our work will help protect the rare brook lamprey, whilst allowing flood defence measures to protect the city of Winchester.