Impulsive waves generated by snow avalanches falling into lakes

Gianluca Zitti, Christophe Ancey, Matteo Postacchini, Maurizio Brocchini

Thursday 2 july 2015

11:50 - 12:10h at Antarctica (level 0)

Themes: IAHR/COPRI Symposium on Long Waves and Relevant Extremes

Parallel session: 11D. COPRI Symposium: Long waves and relevant extremes

In recent years, the number of water reservoirs in high-altitude areas has increased. They are often used to provide water for various activities related with recreational (i.e. skiing) and production activities. Many of such reservoirs are threatened by snow avalanches. To investigate the phenomenon, an experimental study was carried out at the Ecole Polytechnique Fédérale de Lausanne using a prismatic 3m-long flume. A mass of buoyant particles, initially at rest, was released into a water flume down a 30°-sloping ramp. Its impact with the water surface was analyzed in detail. During the tests, the impacting mass, the water depth in the flume and the ramp length were changed. Both the dynamics of the granular mass at the impact zone and the wave generation induced by the impact were acquired using a high-frequency camera and accurately analyzed. An analysis of the wave propagation along the flume, also captured by two lower-speed cameras, was made by mean of numerical analyses based on a depth-averaged Boussinesq-type model. A theoretical analysis has also been undertaken to assess how the sub-aerial mass dynamics influences energy dissipation, and to identify the key variables of the problem, i.e. the velocity at impact, the shape of the water volume displaced during the impact, the depth of the center of the submerged mass and the percentage of submerged mass.