Susceptibility Zonation of earthquake induced landslide-dams at the catchment of Tongkou river, China

Significant hazards may occur due to large landslide-dams formed by earthquake induced landslides. Those landslide-dams present serious threats to both life and property from possible upstream flooding when the impounded lake water level rises, and possible dam failure and downstream flooding with rapid release of impounded water. In order to prevent those secondary disasters, we made an assumption that the landslide-dams are only formed when a large amount of landslide deposits directly rush into a river with moderate or high-velocities. Then a practical prediction method is presented to extract the dangerous slopes which are thought as the sources of earthquake induced landslide-dams. The prediction procedure consists of the following steps: (1) identification of all the slopes using spatial statistics; (2) the extraction of potential slopes according to our assumption using three spatial relation filters; (3) stability analysis to determine landslide prone slopes and volume estimation of potential landslide deposits using Limit Equilibrium Analysis. (4) susceptibility mapping by ranking the exact slopes. This method has been used to extract slopes those are potential to collapse and form landslide-dams in the catchment of Tongkou river after the 2008 Wenchuan earthquake, China. Results show that the proposed method is effective and efficient.