Probabilistic modelling for avalanche hazard and risk assessment

Abstract. The number of requirements for hazard and risk assessment of mass movements like avalanches has increased over time. We are presenting a feasibility study of applying the approach of probabilistic hazard and risk assessment, which was originally developed for seismic hazards and risks, to avalanches. This modelling approach is based on the idea of simulating a large range of possible events and associate probabilities or rates to these events. The aim of such a probabilistic modelling approach is to provide more nuanced modelling results as a basis for consistent hazard and risk management. It allows to derive continuous intensity frequency curves for any location in the affected area. Furthermore, continuous loss frequency curves can be derived by combining the simulated event intensities with affected objects and their vulnerabilities. The probabilistic modelling approach is enabling several products and applications, which are not possible with the current Swiss approach of hazard and risk assessment for avalanches. This first attempt of the probabilistic modelling approach to avalanches provides plausible results, which are in line with existing hazard assessments. Furthermore, it provides more differentiated results by enabling hazard maps for any given return period, and it enables the generation of maps depicting the probabilities of being affected by avalanches of a certain avalanche intensity. These types of products are not possible with the current Swiss hazard assessment approach.