Effect of Changing the Dimension of Initial Debris Mass in the Dynamics of Landslide Generated Tsunami

Abstract

Debris ow is a traveling mass of loose mud, soil, air, water and sand that moves down a slope caused due to gravity. When debris ows, landslides, or any gravitational mass

ows hit closed or partially open water sources such as seas, oceans, fjords, hydraulic reservoirs, mountain lakes, bays and landslide dams, it results in tsunami (impulse water waves) by transforming their impact energy to water body, potentially causing damages of infrastructures and human casualties both near eld and the distant coastlines. The degree of hazard depends on the scale, types, location and process of the landslide. Volume or size of the initial debris mass that fails in the slope, is one of the dominant factors in accelerating the splash strength or intensity, the propagation and amplitudes of the subsequent water waves and potential dam breach or water spill over. Here, we numerically integrate the two-phase mass ow model [61] for quasi three dimensional, high-resolution simulation results with variation of size of the two-phase initial landslide or debris both longitudinally and laterally. In our numerical experimental results, we observe fundamentally di erent solid and uid wave structures in the reservoir, and the dynamics of submarine mass ow for di erent volumes of the release mass by extending or contracting the base area along down-slope and/or cross-slope directions. The simulation results show that tsunami amplitudes and run out extents are rapidly increased when the volume of initial release mass in the form of a triangular wedge is enlarged by increasing the base area through the increment of the length and breadth of the release base. This study can be an instructive tool to develop and implement tsunami hazard mitigation measures to enhance public safety and reduce potential loss.