Rockfall Susceptibility Maps in Styria considering the protective effect of forest

The study presents a GIS-based approach aiming at the identification of rockfall propagation areas considering the protective effects of forests in the Province of Styria, Austria. An empirical approach was selected to identify potential rockfall source zones. Based on a Digital Terrain Model derived from LiDAR data, threshold slope values for potential release areas were attributed to geotechnical units. The run-out distances were estimated by velocity calculation based on a one parameter friction model. The method was applied for the first time in such large study area. Friction coefficients were attributed to forestal units based on the detailed characterisation of relevant forest parameters derived from laserscanning data. Finally, two scenarios based on different friction coefficients were modelled: one considering the current forest cover and one assuming no forest cover. The results demonstrate the strong protective effect of the forest cover. Furthermore, an indicative hazard map was generated by classifying the transition frequencies and kinetic energies of blocks.