Author(s)

TAKEYASU SUZUKI, TAKUMI ITO, SATOSHI GOTO

Abstract

For flooding, visual information of rising water levels can signal the timing of residents’ evacuation. For impending sediment disasters, however, the state of the groundwater level or soil moisture content in a slope’s soil layer cannot be visually confirmed. Therefore, the authors developed a sediment disaster alert system, in part using a color-coded chart that signals evacuation urgency – an “evacuation switch”. The system uses a slope’s real-time rainfall observation as input data and performs real-time stability analysis based on rainwater runoff and infiltration simulations. In Nishikatsura Town, Yamanashi Prefecture, Japan, a slope designated as a mountain stream from which debris flow is likely to occur was selected as the target. The simulation model was constructed based on results of soil exploration and soil testing. The website for a sediment disaster alert system was developed by combining the rainfall observation system and the simulation. To provide the evacuation switch for residents, this website expresses risk of sediment disasters not by a safety factor but by a chart showing the current groundwater level with respect to the groundwater level at which the slope becomes unstable and collapses.

Keywords

sediment disaster, real-time rainfall observation, simulation, sediment disaster alert system, switch for evacuation