Author(s): Takashi Wada; Masaki Marudou; Hiroshi Miwa; Yoshifumi Satofuka
Linked Author(s): Hiroshi Miwa
Keywords: Debris flow; River flood; Combined inundation; Small-scale countermeasures; 1-D and 2-D combined numerical model
Abstract: We investigated countermeasures for flood damage during combined inundation caused by debris flows and floodwaters in densely populated areas adjacent to mountainous areas and river using a numerical simulation. We considered a temporary road-closure facility, temporary levee, and temporary farmland or park reservoir as the small-scale countermeasures without damaging the existing urban functions and landscape. The simulated inundation results under various inflow conditions and existing conditions (without small-scale countermeasures) suggested that the debris flow inflows from mountain streams have a larger impact on flood damage than the inflows from the main and sub-rivers. In addition, the inundation area expanded along roads, affecting the inundation in the central part of target areas, which was far from the inflow points of the debris flows. This is because the digital topography in our numerical simulation considers the location of houses and road networks in the target areas. The simulation results of the topographies installed at the temporary road- closure facility eliminated the flood damage in the central part of target areas, which made it possible to evacuate local residents and tourists at these points. On the other hand, the temporary levee and temporary reservoirs failed to eliminate the flood damage simulated under the no-facility condition. These results suggest that the use of the countermeasures and drainage channels together with the existing road network and new culverts for the rapid discharge of floods and debris flows is effective in eliminating flood damage.
Year: 2024