Hydrological drivers of surface runoff during high intensity rainfall experiments in Alpine ski regions

• 20 + years of data from 74 experiments reveal ski slope impacts on alpine hydrology. • Surface runoff is higher for ski slopes, indicating altered hydrological behaviour. • Random forest analysis shows surface runoff depends on multiple variables. • Key surface runoff drivers include land use, geology, soil, and topography. • Sustainable soil and land-use management can reduce ski slope runoff. This study investigates the surface runoff behaviour in 12 ski regions in the Eastern Alps based on data from 74 rainfall simulation experiments. The dataset includes information on hydrological responses, water storage, and infiltration. By applying a random forest regression model, surface runoff coefficients were linked to site-specific hydrological variables, providing insights into drivers of surface runoff. Results indicate higher surface runoff coefficients on ski slopes (0.57) compared to reference areas (0.07) within ski resorts that were not modified for skiing activities. Moreover, our findings suggest that geological variables are the strongest predictors of surface runoff on ski slopes. On ski slopes the surface runoff response is also influenced by a combination of hydrological variables, including mechanical disturbances from slope preparation and land use practices. For the reference areas, soil and land use variables play a more pronounced role. These findings underscore the importance of sustainable soil management and restoration strategies to mitigate the impacts of ski slope construction on runoff regimes and to maintain hydrological stability in Alpine regions.