Vegetation as a remedial measure against erosion and shallow landslides in steep soil slopes

The Swedish Civil Contingencies Agency, the Swedish Geotechnical Institute, the Swedish Road Administration and the Swedish University of Agriculture have together been involved a project named “Vegetation as a mean for slope stabilisation”. The aim of the project was to introduce soil-bioengineering methods in Sweden through demonstration projects and to obtain experiences regarding the function and effect of plants on slope stability within Swedish conditions.

In three selected areas, the plant- and soil conditions were studied, with tests commencing in the spring of 2004 and in the beginning of 2005, respectively. The project ended in 2007 in a report containing recommendations, based on the experiences from the project, for the continued use of soil bioengineering methods.

In the test site Bispgården, a new road was built in 2004 through a gully area. The soil consists of highly erodible silt and sand material. Hedge- and brushlayers with grass seeding were selected to protect the soil from erosion in one slope. Equipment for measurements of pore pressure and precipitation were installed in the summer of 2004. Studies of the plant conditions were conducted several times during the first two years of the project.

In the test site Bydalen, a reconstruction of a country road was conducted in 2005, as the road was plagued with annually recurring erosion along it’s existing silty-till slopes. These slopes were to be restabilised during reconstruction. All together nine existing slopes were stabilised in early 2005 by different soil bioengineering methods proposed by the project group. The group analysed the function of the plants together with automated recordings of precipitation.

In the test site Näsåker, steep slopes of a country road were repaired in 2005-2008, due to continuing erosion and landslides in the silty soil slopes along the existing road. The slopes were stabilised with soil bioengineering and soil nailing.

Different soil bioengineering methods have been used in some new production sites, following this demonstration project. The methods may also be implemented in future projects.

The results from the demonstration in project sites, will be described in this presentation.