Author(s): Nozomu Onaka; Yoshihisa Akamatsu; Takanori Kono; Kohei Yamaguchi
Linked Author(s):
Keywords: Heavy rain in July 2018; Complex disaster; Flood; Debris flow; Unmanned aerial vehicle
Abstract: The heavy rain in July 2018 caused debris flow and river flooding in the Higashi River in the Shimata River Basin in the Osogoe district of Iwakuni City, Yamaguchi Prefecture. In this study, we conducted a record of the disaster situation and field survey using the UAV after the disaster in the Osogoe district. In addition, we conducted the ortho-images production, runoff analysis, and inundation analysis. As a result, the causes of the inundation in the Osogoe district were 1) the significant rise in the riverbed due to the flowing of sediments and driftwoods carried by the debris flow and 2) the driftwoods blocking up the river flows at the bridge. In addition, the inundation did not happen without outbreaking the debris flow from the situation of the inundation analysis. The area where the debris flow occurred was included in the landslide prone area. Therefore, the management strategy for the afflicted area like the Osogoe district needs to predict the direct inflow of the debris flow with a lot of sediment and driftwoods to the river segments.
Year: 2020