Tsunamis Generated by Fast Granular Landslides: Results of 3D Experiments on Wave Initiation, Propagation and Energy Transfer

Landslides falling into water bodies such as lakes, reservoirs, fjords or oceans, can generate huge waves, which are a type of tsunami. The formed wave could be very devastating particularly close to the impact and in narrow waters: past events showed wave run-up of hundreds of meters which killed thousands of people.

In order to study the physical processes involved and provide tools to assess the related hazard, we constructed a facility to study tsunamis generated by landslides in the laboratory of the Sediment Transport research group of the Technical University of Catalonia, Spain. The set-up consists of a landslide generator releasing granular loose material at a velocity up to 25 km/h into a rectangular water basin.

The experimental results permitted to develop new mathematical formulas linking landslide characteristics with the formed wave geometry. The formulas were successfully applied to a past event occurred in Chehalis Lake, Canada, in 2007. Furthermore, we investigate the mechanism of energy transfer between landslide and wave. We demonstrated that only a small part of the landslide energy is transferred to the wave. This result can be of help for the numerical modelling of the phenomenon.