SEDIMENT DISASTERS AND ASSESSMENT OF THEIR OCCURRENCE PROBABILITY TO RAINFALL AFTER THE 2016 KUMAMOTO EARTHQUAKES

Abstract

 Sediment Disaster Rainfall Index was calculated for sediment-related disasters caused by rainfall after the 2016 Kumamoto Earthquakes and it was confirmed that its values at actual disaster locations were below the threshold defined without considering the effect of earthquake. The threshold value considering the effect of earthquake was then examined to see how the lowering of it affects the number of disaster occurrence locations. By analyzing relationship between the calculated index value and the number of disaster locations, optimal reduced threshold value was studied. The results show that 70–80% reduction of the threshold would be suitable to consider the decrease in soil strength due to the earthquake.