Landslide induced debris-flow at a dump site

A debris flow triggered by a landslide at a small dump site in San-Jy Taiwan, during Typhoon Babs on October 26,1998, was explored in this study. The width of the gully was widened by the debris flow from the original 2 m to 20 m, and the channel bed was incised 3 m. The total volume of the debris flow is estimated to be 19,600 m(3). The runout distance of the debris flow is 780 m along a slope of about 10.2 degrees. The occurrence of the debris flow was near the end of the storm according to the hydrological data. The particle size, soil porosity, and the super elevation at the bend were analyzed. The flow velocity is estimated to be 11 m/s, and a building was severely damaged causing two casualties. In order to mitigate possible disasters at other dump sites, the hydrogeological parameters of the gully and the dump site specification related to the landslide were evaluated in this paper.