Spatial Analysis of the Landslide Characteristics Caused by Heavy Rainfall in the Northern Kyushu District in July, 2017 Using Topography, Geology, and Rainfall Levels

Abstract

The heavy rain in Northern Kyushu District on July 5, 2017 caused a sediment disaster, resulting in the loss of many lives and damage to buildings. In this study, the primary causes (topography and geology) and trigger factors (rainfall) for the sediment disaster were spatially analyzed to examine factors contributing to slope failure. As a result, it was found that the number of slope failures was highest in metamorphic rock areas and the occurrence density of the landslides was highest in plutonic rock areas. In addition, the slope angle of the slope-failure source point was sizable in volcanic rock areas and many landslides occurred in the valley-formed areas. A rainfall analysis showed that the Akatani, Shirakitani, Sozu, Kita, Naragaya, Myoken, Katsura river basins and Ono, Ohi, Sata, Inaibaru river basins are different rainfall distributions, which significantly affected the slope-failure occurrence density.