What is biotechnical erosion control and stream bank stabilization?
Biotechnical erosion control and stream bank stabilization projects use live native vegetation, or a combination of vegetative and structural materials (a ‘hybrid’ solution), to protect stream banks and reduce the input of fine sediment to the watercourse in three ways: (1) the physical presence of the vegetation cover adds roughness to the bank, reducing near-bank flow velocities and decreasing erosion by fluvial entrainment; (2) the structural strength of the vegetation root wad acts to bind the bank materials together to safeguard against bank failure; and (3) the water uptake of the plant during growth acts to drain the bank and reduce the occurrence of bank saturation, reducing vulnerability to failure. Successful biotechnical methods become more effective as the vegetation grows and establishes a permanent vegetative cover which can shade the stream and provide habitat for birds and other species. Installation of boulders and rootwads or other structures can provide bank protection and additional habitat complexity while the vegetation establishes. Disadvantages may include continued channelization of the stream, discouraging its natural tendency to meander along the floodplain. Where feasible, explore options such as widening the riparian corridor through conservation easements or through recreating floodplains terraces.
Biotechnical methods are an alternative to conventional erosion control methods (e.g., riprap, gabions) and aim to provide effective streambank stabilization while minimizing damage and disruption to instream and terrestrial habitats. They are also considered generally more cost-effective than conventional methods, especially when long-term maintenance and repair are factored in because they are designed to be strong initially and grow stronger as the vegetation becomes established. Biotechnical methods are considered especially appropriate for environmentally sensitive areas such as parks, woodlands, riparian areas, and scenic corridors where aesthetics, wildlife habitat, or native planting may be critical.