Evolution of landslide-generated edge-wave packet

The physical phenomenon of the evolution of a landslide-generated edge-wave packet moving along a coast was studied experimentally and analytically. Experimental results show that waves generated by a nearshore disturbance propagate along the shoreline in the form of a single edge-wave packet. The edge-wave packet is highly dispersive: it degenerates into different modes and frequency components after its generation, and the wave amplitudes attenuate rapidly during the propagation. The frontal portion of the wave packet appears to consist of both Stokes-mode and higher-mode edge waves; each mode is propagating at the same speed and substantial wave energy is distributed offshore. The rear portion of the wave packet is composed of clean Stokes-mode edge waves; the energy is confined to the nearshore region. Wave amplitude dissipation caused by boundary-layer effect is much smaller than that caused by wave dispersion. Experimental results with a variety of initial disturbances showed that the evolution of the edge-wave packet is independent of the type of initial disturbance; the main features of the wave packet are the same, although the wave amplitudes may be different. The nonlinear effects on the wave speed are observed in the experiments.;An optical device, a Laser-Induced-Image Water-Surface-Profiler (LIIWSP) system, was developed to measure the nearshore wave profiles. Both runup/rundown processes and the contact line effects of the edge-wave packet are captured by the LIIWSP system. The nearshore velocity measured by a two-component laser Doppler anemometer (LDA) system supports the theoretical result that the longshore velocity is in phase with the water-surface profile while the cross-shore velocity appears to form a complex pattern because the cross-shore component is influenced by the existence of the higher-mode edge waves. Both the modified version of an analytical model derived by Carrier (1993) and the asymptotic model based on the method of stationary phase produce satisfactory predictions for the evolution of an edge-wave packet.