Physical Modelling of Granular Landslide-Generated Tsunamis with Large Relative Mass

Abstract:

Understanding gravity driven landslides and the properties of the resulting landslide-generated

waves is of increasing importance with the continued development in mountainous coastal areas

that have a high landslide risk. Previous studies have focused on landslides with small relative

mass and large relative thickness acting as a solid block, however very large and extremely rapid

landslides typically behave like a flow of granular material. In the present study, we observe

the properties of landslides and landslide-generated waves in a 2m wide laboratory landslide

flume. The test landslide consists of 3 mm spherical ceramic beads that are released down an

8 m long slope inclined at an angle of 30°. Using high-speed digital cameras and capacitance

wave gauges, we measure the wave generation and propagation along the 36 m wave flume and

run-up on an angled ramp for a range of landslide volumes and water depths. Using particle

image velocimetry, we analyze the landslide properties at impact (velocity, thickness, shear) and

correlate the these with the wave properties (height, celerity, spectra) in the generation region.

In particular we investigate the influence of large landslide mass relative to the water depth on

the wave behaviour. Characterizing the behaviour and interaction of massive and rapid granular

landslide flows into water is crucial for the accurately assessing the risk to the design of coastal

infrastructure including hydroelectric operations.