Hot spots for simplified risk scenarios of the Trafoi rockslide (South Tyrol)

The Trafoi rockslide is very similar to the Val Pola landslide before it evolved in a catastrophic rock avalanche in 1987. The Trafoi rockslide was recognized and mapped on the basis of geomorphic evidences such as double crests and detachment niches/scarps as well as geologic proxies such as gravitational offset of distinctive bedrock levels and trenching and fracturing of rock masses. In order to assess the activity status of the landslide, not discernible from field evidences only, periodic GPS monitoring on 11 benchmarks was started in 2007 and continued until 2010 with static-rapid measurements repeated 3 to 4 times per year. Results have shown that portions of the rockslide move at some cm/year rate. This highlights the potential for a possible evolution of the mass movement and the necessity of hazard scenarios mapping and run-out modelling. In order to define volume of possible detachments scenarios, digital aerial photo-interpretation were used together with High Resolution DEM and information collected from geomechanical field survey. The Trafoi rockslide is among the test sites of the ongoing European project “Monitor II”, that is proposing the usage of hot spots in the process domain as a practical mean to describe hazard scenarios. Following such approach, simplified hazard and risk scenarios were schematized on the basis of the data collected with monitoring and analysis of ongoing and potential slope instability processes.