Simulation of Tsaoling landslide, Taiwan, based on Saint Venant equations over general topography

The 1999 Chi-Chi earthquake triggered the catastrophic Tsaoling landslide in Taiwan. The geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0.126 km³ and 0.15 km³ respectively. The debris material ran over a distance of 1.6 km with 500 m descent in elevation. In this paper, we use the continuum model of hydraulic flow, SHALTOP^2D, based on the equations of Bouchut and Westdickenberg to simulate numerically the landslide dynamics. When the mass is moving, the flow is assumed hydrostatic with a basal Coulomb friction. The best fit is obtained using the basal friction angle equal to 6°, the only parameter of the simulation, uniformly applied in the calculation domain. The landslide front reaches the Chinshui river valley, the foothill of the slope, within only about 25 s after initiation and the motion settles in about 113 s. The maximum speed is estimated 75 m/s. The spreading of the deposit agrees well with the field measurement.