Climate change impacts on large scale avalanche risk in alpine regions

Observations in various regions worldwide document a decline in mean snow depth, spatial extent, and duration of snow cover, indicating a connection to climate change, especially at low elevations. Climate scenarios project further changes, but the exact consequences on future snow cover and avalanche patterns remain unknown. Our work investigates the influence of climate change on the snow cover, specifically focusing on its impact on avalanches and the associated risk to buildings. 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 on a large scale. We applied an algorithm to generate a protection forest layer, potential release areas, and conduct snow analysis for current climatic conditions. The RAMMS::LSHIM algorithm within the RAMMS avalanche model produces avalanche hazard indication maps. They are combined with the CLIMADA risk assessment platform, incorporating exposure and vulnerability data, to create spatially explicit risk maps under different avalanche return period scenarios.To address climate change impacts, we have integrated the CH2018 climate scenario data including various model chains into avalanche hazard mapping, using the SNOWPACK snow cover model. Snow cover simulations cover the years from 1997 to 2100 and deliver three day snow accumulation data and layer temperatures for potential future avalanches. We used this data to run the RAMMS::EXTENDED avalanche model with modified snow and temperature parameters. This enabled us to create hazard indication maps considering climate change.Results indicate a potential decrease in the spatial extent of avalanches, especially at lower altitudes, due to rising snowline, particularly in model chains with reduced snowfall. However, within CH2018, other climate model chains suggest increased snow accumulation, resulting in larger avalanches and increased pressure in high-altitude areas.Applying the CLIMADA risk tool to climate change hazard analysis using an enhanced vulnerability curve and uncertainty analysis results in various risk outcomes. An average approach over all model chains suggests a decrease in risk, particularly in low-altitude side valleys. Single model chains with increased snowfall project higher risks despite a reduced affected area. The study underlines the need to incorporate climate change into practical avalanche hazard assessment and subsequently risk analysis.Overall, this research, for the first time, quantifies the impact of climate change on the potential future spatial distribution of avalanches and associated changes in potential risk. The practical applicability of climate change avalanche hazard assessment was demonstrated, offering insights for stakeholders to assess future risks and consider climate change risk appraisal options.