Author(s): Masaharu Fujita; Kazuki Yamanoi; Shusuke Miyata; Ani Hairani; Djoko Legono
Linked Author(s): Djoko Legono
Keywords: Debris flows; Volcanic areas; Landslides; Rainfall runoff simulation; Sediment disaster information
Abstract: A simulation-based method for predicting the occurrence of debris flows has been proposed for volcanic ash deposition areas. A surface flow on a slope occurs more easily at a rainfall event after a volcanic eruption because crusts on the fresh volcanic ash deposit reduce the infiltration capacity. The surface flow is one of the factors triggering debris flows. If the crusts are broken, the infiltration capacity increases and growth in an underground water level at a rainfall event causes a landslide. This sliding mass possibly develops to a debris flow on the slope if the sediment mass contains much water. Therefore, the surface flow discharge and the water content of the sliding mass are thought to be the essential parameters to evaluate the debris flow occurrences. Considering the rainfall runoff processes, we have developed a method for predicting debris flow occurrences using a rainfall-sediment runoff simulator. The surface flow discharge and the water content (or a sediment concentration) of sliding masses are calculated by the simulator. The debris flow occurrences were simply detected using these two variables and the equilibrium sediment concentration of debris flow. This method was applied to a virtual volcanic basin. The debris flow occurrences in the basin were simulated for two cases with volcanic ash deposit covered by crusts and without volcanic ash deposit. The simulation results have shown several types of debris flow occurrence process.
Year: 2018