Modeling landslide-generated water waves with long-wave equations.

Hong-Yueh Lo, Philip Liu

Thursday 2 july 2015

11:30 - 11:50h at Antarctica (level 0)

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

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

Landslides are known to be capable of generating extreme water waves that could damage ships and coastal communities. The fact that the landslide can be either subaerial or submarine initially, the landslide material can be different, and the water waves may break near-source necessarily complicates the problem, and a comprehensive three-dimensional numerical model is necessary to more fully resolve the physics. However, if only long-wavelengthed water waves generated by the landslide are considered, the long-wave approximation can be employed to simplify the problem by eliminating the need to resolve the vertical dimension. The justification for this approach is the belief that only long waves are capable of traveling a long distance without significant energy dissipation, and that the near-source wave breaking and highly three-dimensional flow have only minor effects on the outward-propagating wave. We developed a long-wave model suitable for studying landslide-generated waves. Long-wave equations of different degrees of accuracy can be used in the numerical model. Within the context of long-wave theory, the landslide information is passed on to the water waves as a temporarily varying bathymetry. Both subaerial and submarine landslides can be resolved in the model. In the present study, we sought to investigate the landslide-wave mechanics from a more analytical perspective, by considering a one-dimensional problem with a solid landslide moving at a constant speed, in either constant water depth or on an incline. We successfully identified the effects of landslide velocity and dimension on the generated waves. Additionally, by comparing results computed from different long-wave equations, we were able to examine the relative importance of wave nonlinearity and frequency dispersion. Work in progress includes extension to two dimensions as well as an investigation on the effects of landslide shapes and material in the long-wave model.