SOIL BIOENGINEERING FOR UPLAND SLOPE STABILIZATION
Soil bioengineering is the use of plant material, living or dead, to alleviate environmental problems such as shallow, rapid landslides and eroding slopes and stream banks. In bioengineering systems, plants are an important structural component. This approach to slope stabilization requires a true partnership among many disciplines, including soil scientists, hydrologists, botanists, engineering geologists, maintenance personnel, civil engineers, and landscape architects. Soil bioengineering most often mimics nature by using locally available materials and a minimum of heavy equipment, and it can offer roadside managers an inexpensive way to resolve local environmental problems. These techniques can also be used in combination with traditional engineering techniques such as rock or concrete structures.
Transportation systems provide access and allow utilization of land and resources. Development priorities usually emphasize access, safety, and economics. Environmental concerns involve operational and maintenance problems such as surface erosion, plugged drainage structures, and mass failures. Transportation systems provide tremendous opportunities and, if properly located on the landscape with well designed drainage features, can remain stable for years with negligible effects to adjoining areas. However, roads are often linked to increased rates of erosion and the accumulation of adverse environmental effects on both aquatic and terrestrial resources. This has become even more apparent during major winter storm events in recent years. This is not new information to road managers. Road maintenance personnel, for example, face a huge task in maintaining roads under their jurisdiction. Major winter storms that have resulted in significant increases in road landslides and impacts to adjoining resources have compounded the road manager’s challenge. The Washington State Department of Transportation (WSDOT) has been using soil bioengineering methods since the 1980s.
The objectives for this study were as follows:
• Provide viable alternatives, called soil bioengineering or “living” approaches, for slope and shallow, rapid landslide stabilization along different roadside environments
• Educate Engineering in site selection and evaluation, and soil bioengineering techniques, including construction, monitoring, and maintenance
• Provide soil bioengineering decision making skills. This report documents the project process and its outcomes.