The Cockshut is a 3km long chalk stream that flows from springs at the foot of the South Downs in Kingston, eventually joining the River Ouse before flowing out to sea. Overtime the stream has been straightened, deepened, widened and disconnected from the surrounding landscape. The channel had become steep-sided, slow flowing and shallow.
With only 220 existing worldwide, chalk streams provide an ecologically rare home for a whole host of wildlife, and a high proportion of these have been adversely affected by human activities. These globally scarce environments provide a habitat for species like water vole, brown trout, southern damselfly, and the endangered white-clawed crayfish. The site was classified as a SSSI (Site of Special Scientific Interest) in 1988.
The project looks to restore the natural course of the Cockshut, enhancing the flow and reconnecting the stream to the surrounding wetlands. The works are set to enhance biodiversity, help with flood management and restore the stream to flow unpolluted with its native plants and wildlife protected.
Lewes District Council worked in partnership with the Ouse and Adur Rivers Trust (OART), Railway Land Wildlife Trust (RLWT) and South Downs National Park Authority (SDNPA) to deliver the project as part of a drive for climate adaption and nature recovery.
Ebsford were appointed to carry out the construction works and developed a unique methodology that minimised impact to the works area due to multiple sensitivities on site including the discovery of invasive species Parrots feather and the protection of Southern Water assets.
Kicking off on World Environment Day in June, we began works to realign the stream into a new channel which would flow through a 6.8-hectare wetland habitat. The first phase saw the creation of a new sinuous channel, removing the parrots feather to reduce the risk of spread. Wetland areas were created around the new channel to provide natural water quality improvement and pond scrapes around the floodplain to seasonally hold water, enabling aquatic species to survive. A 700m embankment was then created before backfilling the old channel and connecting existing ditches. An excavator and large dump-trucks were used throughout the project to excavate the material, stockpile and segregate it to either the embankments or adjacent to the old channel to use as infill.
In July we welcomed school children, landowners, local councilors, and project funders to the site to see progress, ask questions and find out what goes into a project of this scale, from feasibility through to construction and everything in-between. Highlighting the schemes amazing benefits to habitat and biodiversity and sharing knowledge with those who will inspire future projects.
The final element of the project consisted of hydroseeding, a planting process that uses a slurry of seed and mulch, and installing two bridges to enabling better access. By August 2023 the previously canalised, stagnant channel next to a low-quality agricultural field was transformed into a diverse and thriving wetland habitat, providing flood alleviation in extreme weather conditions.
