Estimation of Landslides Due to the Combined Disaster of Earthquake and Heavy Rainfall Using Multi-Temporal Lidar Data

A series of earthquakes hit Kumamoto Prefecture, Japan, in April 2016. Numerous landslides occurred in the surroundings of the Aso volcano and in the areas within 10-km from the Futagawa fault. Two months after the earthquake, the stagnation of the rainy season front brought heavy rainfall to the Kyushu Island. The rainfall caused additional landslides and the expansion of the earthquake-induced landslides. In this study, three temporal Lidar data taken before the 2016 Kumamoto earthquake, after the earthquake and after the heavy rainfall, were used to estimate the earthquake-induced and rainfall-induced landslides in the outer ring of the Mt. Aso. The height difference between two temporal digital surface models (DSMs) and that of digital terrain models (DTMs) were calculated. They were combined to extract the collapse zones and sediments of landslides. The results were verified by comparing with the reports of visual interpretation of aerial optical images.