River Roding Bank Protection Works
Client: Environment Agency, Breheny Contractors
Salix advised 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. 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 are 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, NAG 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
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 for inter-tidal bioengineering design, for the Environment Agency and the Thames Estuary Partnership.
Materials used: NAG C125BN, Rock Roll, Brushwood Faggots, Wetland Plants
The vertical river wall was removed and a
natural sloping bank created
The re-graded bank with lines of
Brushwood Fascines designed to accrete find sediment and
sustain reed growth
The completed detail showing the
Brushwood
Fascine terraces designed to locally reduce
slope angle and encourage fine sediment
deposition
Vegetation establishment after 18 months.
Vegetation establishment has been through natural
colonisation sustained by fine sediment deposition
Common Reed (Phragmites australis)
establishment between high and low tides
The completed project. Note the terrace wall at the toe of the bank created when the original retaining wall was cut down
