Author(s): Toshiyuki Moriyama; Muneo Hirano
Linked Author(s):
Keywords: XRAIN; Precipitation radar; Cumulative rainfall; Debris flow; Collapsed area
Abstract: To quantify the relationship between rainfall intensity and landslide area, the 3-hour cumulative rainfall, Riso, during a heavy rainfall event in July 2017 in northern Kyushu using the XRAIN radar system was calculated. The XRAIN radar system is operated by the Ministry of Land, Infrastructure and Transport, Japan, and has X-Band MP and C-Band MP radars. In this study, data from the XRAIN system were downscaled from a resolution of 250 to 100 m grid cell and used to investigate the magnitude of landslides for a catchment area in northern Kyushu of about 430 km². The Riso is closely related to the occurrence of debris flow in the Minamata District, Japan where a big debris flow occurred in 2003. The maximum Riso was estimated to be 122 mm in the Minamata area (2004, Moriyama et al.). In this study, the maximum Riso, i.e., Risomax, is estimated using the observed rainfall rate from 7:00 on 5th July to 23:59 on 6th July for a single grid cell of the river basin. Finally, in each catchment area, the maximum value of Risomax, i.e., max-Risomax, is selected to obtain the basin maximum Risomax. It was shown that the landslide area due to heavy rainfall is closely related with max-Risomax.
Year: 2018