Salix successfully tendered for a project to form a backwater and island in a field adjacent to the Grand Union Canal.
The aim was to restore a wetland area on the banks of the canal for the benefit of wildlife and the fishery. Leaf matter and sediment was removed to create on-line ponds of variable depths fringed with native wetland plants. Particular focus was on creating suitable habitat for Water Voles that have recently declined to only two known sites in the Colne Valley Park.
Fishery improvements included creating adult fish spawning habitat, gently sloping sides with emergent vegetation and shallow non-vegetated fry shelves.
The scheme design ensured no material was taken off site, large logs and branches were used to create sub surface and emergent in-channel features, otter holts and habitat piles for invertebrates.
Rotting vegetation was also used to replicate a natural compost bin highly attractive to grass snakes, sediment was used to create an island and to provide a shallow area on the east bank of the canal. These works delivered a high value marginal area for fish spawnings, fry habitat and wetland plants.
Post construction, an ecological survey was carried out in May 2011 by Alder Ecology. This concluded that the site experienced an increase locally in aquatic life associated invertebrates such as damselflies and dragonflies. Alder’s report showed that the general area had a greater biomass and diversity of invertebrates after the completed works.
The newly created islands featured vertically cut banks containing two holes that could be used for kingfishers for nesting.
Positively, kingfisher passes were observed over the backwater and island during the survey.
Client – Groundwork Thames Trust. Project partners Environment Agency, British Waterways and Blenheim Angling Society – Grand Union Canal off Springwell Lane Harefield
