Soil bioengineering treatments for degraded riparian ecosystems

Soil bioengineering is the use of living plant materials to perform some engineering function. Treatments have been developed to solve a variety of riparian problems. Soil bioengineering treatments are modelled on the natural processes that provide solutions to degraded riparian areas (Polster 2009). Plant species that will root readily from dormant stem cuttings are used. Willows (Salix spp.), some poplars (Populus spp.) and red-osier dogwood (Cornus stolonifera) are commonly used in western North America. Live gravel bar staking can be used to stabilize excess sediment in streams and therefore speeds the process of pioneering vegetation establishing on gravel bars and starting the successional processes that eventually lead to productive riparian forests. Live bank protection provides an erosion-resistant face for eroding stream banks. As the plant materials used in the construction of live bank protection grow, the shoots from the new growth serve to slow near shore water velocities thus further reducing erosive forces and providing an opportunity for sediment in the water to be deposited. Live silt fences can be used in small ditches and drainages to slow flow velocities allowing sediment to drop out. As the plant materials used in the live silt fences sprout and grow, a wooded wetland is created that serves to capture sediment and address some pollutants that may be present. Wattle fences can be used to stabilize steep streambank slopes by creating small terraces on the slope. In addition to the growth of the cuttings used to construct the wattle fences, by stopping the constant movement of surface materials on over-steepened slopes, the wattle fences provide an opportunity for pioneering species to establish. Live pole drains can be used to address seepage areas on disturbed slopes, initiating the successional recovery of these unstable areas. Soil bioengineering methods can also be used to manage invasive species by providing successional advancement past the stagnant weedy stage. Creation of an instant canopy of woody species can suppress the growth of problem weeds such as reed canary grass (Phalaris arundinacea) and blackberry (Rubus discolor). Examples are drawn from the experience of the author.Non UBCUnreviewedUnknow