Dynamic Analysis of Flowlike Landslides at Brienz/Brinzauls, Graubünden, Switzerland

Abstract. Accurate forecasting of the risk posed by catastrophic failure of rock slopes requires estimates of the potential impact area and emplacement velocity. While most previous work in this context has focused on rock avalanche behaviour, recent and well documented case histories are showing that a more diverse range of landslide classes can occur. In the present work, we analyse two rock slope failures that occurred at Brienz/Brinzauls in Switzerland. These events initiated within 500 m of each other on the same slope, but emplaced with velocities that differed by five orders of magnitude. We describe the derivation and implementation of a GPU accelerated numerical model that can simulate emplacement velocities on the order of m/day. We then perform forensic back-analysis of the two case histories. Our results highlight the role of path material in controlling emplacement behaviour, as well as the effect of moderate changes in source material lithology. We argue that these cases can form the foundation of more accurate hazard and risk analyses at similar sites, where a wider range of potential future behaviour than is typical should be considered.