Debris-flow generated tsunamis and their dependence on debris-flow dynamics

Debris-flow generated tsunamis can be extremely dangerous for lakeside settlements and infrastructure. Debris-flow composition strongly affects debris-flow thickness and velocity, and therefore also the generated tsunami. This interaction is, however, poorly understood. We investigate the effects of debris-flow volume, composition (gravel, sand, clay, water) and subaerial outflow slope on wave celerity and amplitude in a small-scale physical model consisting of an inclined outflow channel which transits into a three-dimensional water reservoir. We find that upon debouching, a debris flow pushes the water forward until wave celerity exceeds subaqueous debris-flow velocity (i.e. Froude number