Modelling rock avalanches and their relation to permafrost degradation in glacial environments

High runout distances characterize landslides falling on glaciers because of (1) low friction offered by ice to sliding and (2) complex rock-ice interactions that take place during mass motion. Block-fall models (two and three-dimensional) were tested on the 1936 Felik landslide (Mt.Rosa Massif). Geotechnical parameters were assessed through a back-analysis aided by field surveys, aerial-photo and historical data analysis. Outcomes are verified for two rock-ice avalanches which ran along the Brenva Glacier (Mt. Blanc Massif) in 1920 and 1997. Empirical models show poor precision (75%). Three-dimensional numerical models are too complex but two-dimensional ones gave results that pointed out that real runouts exceed predicted ones by 30%, possibly due to fluidisation processes. Rock- ice avalanches require attention because they originate in areas likely destined to experience permafrost degradation and glacier retreat.