Geotechnical stability for Water Vole Heaven

Project Overview

Unity Yorkshire is one of the largest mixed use and regeneration projects in the UK situated on the eastern section of Jct 5 on the M18 providing commercial, residential, retail and leisure services and opportunities. Covering an area circa 250 ha.

Salix were approached by consultants FPCR to provide design advice for creating a series of new drains with the emphasis placed on habitat creation for water voles. Back in 2021 a small population of water voles was discovered in the network of the existing drains on site. The construction of new infrastructure required the rerouting of these drains.

The entire population of water voles were caught by trained ecologists and were transported to a specialist facility in Devon.

Whilst this new habitat developed, the water voles were paired and bred in captivity and released back into the new habitat, now capable of supporting a larger population.

An additional task was to ensure steep sides to the drainage channels (45 degrees) due to footprint uptake and the fact that water voles prefer steep slopes to burrow into with dense marginal vegetation such as Sedges for food source and cover from predators.

Project Solution

We recommended Salix Terra-Lock, an anchoring system for slope stability and erosion control combining Gripple ground anchors, with a biodegradable coir netting (CocoBn) over wildflower seeded slope surface. Rock netting used for tensile strength support for the anchor head and to bind the anchors together to act as one system.

Stability calculations were provided by Gripple to ensure correct anchor type for soil conditions. This was a direct alternative to using geogrids that would require major earthworks and expense.

Our pre-established coir rolls and coir pallets packed with mature native wetland species for instant habitat creation and soil erosion control were placed at water level. Either on shallow berms for the coir pallets or in deeper water brushwood fascines were used below to support the coir rolls and allow them to be placed two thirds into the water.

Within two years the site has well established planting and a thriving water vole population. A huge increase in Biodiversity as well as an excellent carbon sink provided by the wetlands. Some of the slopes have not vegetated as well as normally expected within the two year timeframe, but this was due to the driest summer on record in 2025. Overtime this will improve but ironically the marginal plants are romping ahead in warm water, which is the most vital habitat for the humble water vole.