Climate change impacts on large scale avalanche risk in mountainous regions

The effect of climate change on snow avalanches is widely unknown. 
Various studies indicate that a rise of temperature  and extreme precipitation events will influence the release and the flow regime of snow avalanches. To compare the consequences of these potential changes on snow avalanche hazard and risk with the current situation, we have developed a framework to model avalanche risk at a regional scale. In a first step, we combined an algorithm to delineate potential release areas using a high-resolution terrain model and a forest layer and modeled three hazard scenarios for the current climate situation in a region in central Switzerland. The runout modelling was carried out with the RAMMS::LSHIM Large Scale Hazard Indication Mapping algorithm implemented in the recently released high parameterised version RAMMS::Extended.

For modelling climate change effects on snowfall intensity and snow pack temperature, we used down-scaled data from the Swiss climate change scenarios CH2018 as input for the snow- and surface model "SNOWPACK''. The results of six different model chains within the RCP8.5 emission scenario and a hundred year (from year 2000 to 2100) long data set provided the input to simulate the course of over 600 future winters. For these hypothetical  future winters, we applied extreme value statistics to determine the future changes of the three-day maxima of snowfall. This maxima were used to derive the potential future avalanche fracture depth. We used the output of SNOWPACK for various snow layers to take the effect of changing snow temperatures on the flow regime into account. Furthermore, we considered the rise of the zero degree line to restrict potential future avalanche release zones.

The so-derived changing avalanche hazard disposition maps were used as input for the probabilistic, Python-based risk assessment platform CLIMADA to quantitatively assess the risk to buildings. The resulting maps depict the impacts of climate change on snow avalanche risk by highlighting areas where adaptation measures might be needed and thereby provide a basis for risk appraisal options and risk management strategies considering climate change.