Salix advised engineers Halcrow on bioengineering methods to stabilise a regraded slope as part of an inter-tidal river enhancement project. The existing vertical retaining wall provided no habitat value.

Vegetation Establishment 18 Months Later
Re-Graded Bank With Faggots To Accrete Sediment
Slope Detail
River Roding intertidal

Salix advised engineers Halcrow on soft engineering methods to stabilise a regraded slope as part of an inter-tidal river enhancement project. The existing vertical retaining wall provided no habitat value.

A key objective was to establish vegetation and a constant supply of fine sediment, critical to maintaining inter-tidal vegetation on the new slope.

The location of the works is directly adjacent to the main bridge abutments on the A13 and as such the bioengineering design detail was critical. The angle of the bank slope and sediment trapping features are critical design criteria for inter-tidal rivers.

Lines of Brushwood fascine were installed to trap fine sediment. The cut slope was covered with a temporary biodegradable erosion control blanket, C125BN, to prevent soil erosion during the establishment of the inter-tidal plants species. Rock Rolls were installed in an anchor trench around the edge of all the works to ensure that the bioengineering materials were not undercut.

Removal of existing retaining wall on the River Roding at the A13
Removal of existing retaining wall on the River Roding at the A13

Salix undertook the bioengineering works under the Environment Agency’s framework contractor using specialist long reach machinery.

Salix has been a lead consultant working on a guidance manual “Estuary Edges: Ecological Design Guidance” for inter-tidal bioengineering design. Clients are the Environment Agency and the Thames Estuary Partnership.

Products Used

Pre-filled Rock Roll

Rock Rolls are a robust and permanent revetment for use around reservoirs, shorelines, lake edges, streams and river banks. They are cost-effective revetments that are suitable alternatives to rock rip rap and gabions in many scour applications.

Brushwood faggot/fascine

Salix produce a range of brushwood faggots (fascines) for use in rivers, canals and lakes. We use brushwood from sustainable sources and can supply various timber types including Ash, Hazel and Willow.

Details

Client: J Breheny for the Environment Agency
Location: Greater London
Reedbeds & Wetlands, River Restoration, Rivers & Water Courses, Salt Marshes & Intertidal Rivers