In order to respond quickly for recovery after a disaster and to account how damage is severe, a method for estimating the socio-economic impacts of sediment disasters would be useful by assessing the magnitude of disaster damage. However, no common method for assessing magnitude of sediment disasters due to their inherent features was developed. We identified the problems involved in constructing an index of the magnitude of sediment disasters based on the inherent features. Then, we established a method of estimating the socio-economic impacts of sediment disasters by using the magnitude of sediment movement (“Sediment Movement Magnitude (SMM)”, Uchida et al., 2005) and level of damage to local society (“Damage Level (DL)”, Kojima et al., 2009). We applied SMM and DL to sediment disasters in Japan, Korea and other Asian countries, and confirmed that the method is valid. We also proposed a simpler index, Sediment Disaster Scale (SDS, Category I to V) based on SMM and DL and an SDS phrase for each SDS category to make SDS easier to understand.
A deep-seated rapid (catastrophic) landslide is a phenomenon that may cause serious damage due to the large amount of sediment movement, such as the formation of a landslide dam and debris flows. In Japan, a method for estimating deep-seated rapid (catastrophic) landslide susceptibilities for many small catchments (ca. 1 km2) over relatively large areas (ca. hundreds of km2) was proposed in 2008. In the present study, we applied the Japanese method to the northern part of Jember, East Java, Indonesia, where a debris flow disaster occurred due to the collapse of a landslide dam formed by a deep-seated rapid (catastrophic) landslide in 2004. Although there were several limitations related to data availability, we successfully assessed susceptibility to deep-seated rapid landslides.