Tsunami intrusion into a river

Abstract:

Tsunami intrusion into a river is strongly affected by the river-mouth bathymetry. Complicated tsunami transitions arise from a variety of features at river mouths and the various waveforms. Idealized incident tsunamis, modeled by solitary waves and undular bores, propagating from a wide basin to a narrow channel are studied experimentally in the laboratory. The planar laser induced florescence technique and acoustic wave-gauges are used to capture the waveform transformation at the river mouth. Waves reflected at the shoreline cause wave energy to diffract towards the channel and increase the wave energy transmitted into the channel. Solitary waves with the largest amplification have the longest wavelength relative to the channel width, as shown in the figure below. Additionally, the duration of inundation is extended at the river mouth, with the formation of trailing waves in the channel. The results indicate that tsunami intrusion into a river will be larger and have increased duration of flooding compared to the surrounding shores, hence enhancing the severity of the hazard.

Measured solitary-wave amplification a/a₀ during the intrusion into the river channel with the breadth b/L: here, a is the maximum wave amplitude; a₀, the incident wave amplitude; b, the channel width; L, the wavelength scale of the solitary wave; h, the water depth.