Observation and Numerical Simulation of Debris Flow Induced by Deep-Seated Rapid Landslide

Abstract

Deep-seated landslide sometimes lead to large-scale debris flow and triggered serious damages. To predict hazard area and magnitude of damage due to deep-seated rapid-moving landslide, several numerical simulation methods have been proposed. However, since adequate information about flow depth and velocity of debris flow was generally lacking, the applicability of these simulation methods for describing flow velocity and depth has not been fully examined. We focused a debris flow triggered by deep-seated rapid-moving landslide occurred on July 28th in 2015 at Fukaminato River in Kagoshima prefecture, Japan. We interpreted temporal variation of velocity and flow depth of debris flow at around 1 km downstream from the landslide using video camera images. We applied numerical simulation which describe the phase-shift for of fine sediment in debris flow. As a result, if we considered effects of phase-shift of fine particles on mobility of debris flow, simulated result of the front velocity and depth of the debris flow agreed well with observed data.