Experiments on the impact of snow avalanches into water

The number of anthropized reservoirs threatened by snow avalanches is steadily increasing and impulse waves caused by avalanche impact are becoming a considerable risk for such basins. The dynamics of the impact of a snow avalanche into a water body is studied through laboratory experiments, where a granular material, with solid density slightly lower than that of the water, is used to simulate the buoyant behaviour of the snow. The proposed experimental model shares many similarities with those used to investigate the impact of landslides into water bodies (e.g., see Fritz et al. 2003a, Fritz et al. 2003b), but it also clarifies the differences between the impact of an avalanche and that of a landslide: while a landslide typically reaches the bottom of the water body, because of its high constant density, in the present experiments a floating motion of the impacted mass has been observed. The wave generation and its propagation are acquired by high-frequency cameras placed along the flume. Some preliminary results on wave amplitude/height decay and on wave celerity state the strongly non-linear behaviour of the generated wave. Further, their comparison with the corresponding predictive relations proposed for the case of landslides (Heller and Hager 2010) highlights a different wave decay and celerity evolution in the proximity of the impact.