Unravelling driving conditions of rock and ice avalanches and resulting cascading processes in High Mountain Asia

Abstract Amplified climate warming and the tectonically active landscape in High Mountain Asia (HMA) have led to the occurrence of 60 well-documented large rock and/or ice avalanches (RIAs), resulting in at least 1366 fatalities and extensive negative impacts on ecosystems, water resources, infrastructure, and social stability. In this study, we analyzed historical RIAs in HMA using detailed topographic, climatic, glacier, permafrost, and geotechnical data, along with medium- and high-resolution satellite imagery, to identify 23 potential driving factors. Seismic activity, permafrost thaw, lithology, and changes in precipitation were identified as important driving factors for RIAs, while stream flow, stream order, glacier area, glacier slope, glacier length, height differences, and real length were identified as important driving factors for their cascading processes. Our analysis revealed that RIAs have mostly (86%) occurred on steep slopes (> 30°) at altitudes above 3000 m asl, with a prevalence of slopes facing northeast. Almost half of the RIAs produce cascading processes, which on average travel further and lead to a tenfold increase in fatalities compared to single events. Cascading processes are more likely to occur from smaller (glacier area < 3 km 2 ), steeper-sloped (glacier slope > 30°) hanging glaciers. Debris volume, water volume, and topography are three main drivers of cascading processes. Medium-sized source volumes (10 6 m 3 ~ 10 8 m 3 ) are most susceptible to transform into cascading processes. Statistical analysis indicates that the probability of a RIA transforming into a cascading process significantly increases when the event occurs near high-flow river systems, amplifying potential disasters. These findings offer baseline information on RIA hazards and their cascading processes in HMA, facilitating improved hazard modelling and risk assessment.