Lowther were awarded the contract by Eden Rivers Trust to construct a natural flood management pond and carry out river restoration works at Bessy Gill near Great Strickland in Cumbria, as part of the Cumbria River Restoration Programme.
Overview
Eden Rivers Trust required a contractor to restore Bessy Gill and create a large NFM pond and wetland habitat area to reduce downstream flood risk on the River Leith. The project objectives were to restore natural processes and associated habitat features, reconnect the river to its natural floodplain, improve habitat resilience and biodiversity, and reduce downstream flood risk. The works were subject to habitat and biodiversity restrictions that imposed a strict two-week programme window, after which any unfinished works would have required postponement until early summer 2020.
Works Undertaken
The works involved blocking a culvert that had been routing water under the M6, A6 and the west coast mainline directly into the River Leith, diverting the flow through newly created wetland woodland. River embankments were removed and the channel reconnected to its natural floodplain. The site was then excavated and reprofiled to create a 16,000m2 online pond area, with approximately 7,000 tonnes of soil excavated and transported to a dedicated tipping area.
Heavy rainfall throughout the autumn period required changes to working method and the deployment of mobile pumps to control water build-up and allow excavators to complete the upper bank reprofiling. A weekend period of excessive rainfall required a brief postponement to allow flood water levels to naturally drain through the downstream connections before finishing works could resume. Works were completed within the programme timescales to the satisfaction of the client and landowner.
Outcomes
Throughout winter 2019 and 2020, the completed pond and upstream improvements created a capacity to retain up to 16,000m3 of water, fulfilling all project objectives and helping to alleviate flood damage downstream. The works also created new wetland habitat, with wildlife, flora and fauna beginning to establish at both the pond and the upstream restoration sites.
