Massimiliano Schwarz

Ecological mitigation of hillslope instability: ten key issues facing researchers and practitioners

BackgroundPlants alter their environment in a number of ways. With correct management, plant communities can positively impact soil degradation processes such as surface erosion and shallow landslides. However, there are major gaps in our understanding of physical and ecological processes on hillslopes, and the application of research to restoration and engineering projects.ScopeTo identify the key issues of concern to researchers and practitioners involved in designing and implementing projects to mitigate hillslope instability, we organized a discussion during the Third International Conference on Soil Bio- and Eco-Engineering: The Use of Vegetation to Improve Slope Stability, Vancouver, Canada, July 2012. The facilitators asked delegates to answer three questions: (i) what do practitioners need from science? (ii) what are some of the key knowledge gaps? (iii) what ideas do you have for future collaborative research projects between practitioners and researchers? From this discussion, ten key issues were identified, considered as the kernel of future studies concerning the impact of vegetation on slope stability and erosion processes. Each issue is described and a discussion at the end of this paper addresses how we can augment the use of ecological engineering techniques for mitigating slope instability.ConclusionsWe show that through fundamental and applied research in related fields (e.g., soil formation and biogeochemistry, hydrology and microbial ecology), reliable data can be obtained for use by practitioners seeking adapted solutions for a given site. Through fieldwork, accessible databases, modelling and collaborative projects, awareness and acceptance of the use of plant material in slope restoration projects should increase significantly, particularly in the civil and geotechnical communities.

Quantifying the Stabilizing Effect of Forests on Shallow Landslide-Prone Slopes

Shallow landslides are natural hazards that can affect human life and infrastructure both directly and indirectly. Such landslides usually involve low-cohesion soil mantles less than a few meters deep. As shown by evidence worldwide, the presence of forests can lead to increased slope stability, due to mechanical and hydrological mechanisms, and therefore significantly reduce the landslide risk in many locations. Therefore, the nationwide project SilvaProtect-CH, which provided data and defined uniform criteria for protection forest delimitation in Switzerland, has also included shallow landslide protection forests. According to the modelling results of SilvaProtect-CH, approximately 27 % of the Swiss protection forests provide a protective function against shallow landslides. To facilitate a quick quantitative evaluation of the slope stabilizing effect of such forests, we developed the tool SlideforNET, which is described in this chapter.