STUDY ON AN EVALUATION METHOD OF INITIATION PROBABILITY OF DEBRIS FLOWS DURING HEAVY RAINFALL

Abstract

 In an extreme climate event named “the Heavy Rain Event of July 2018, ” prolonged and widespread heavy rainfall in western Japan caused several debris flows, which led the sediment to flow into rivers, causing further damage from sediment-flood inundation. For the existing landslide alert information, it is important to establish prediction methods that account for the amount of rainfall on individual mountain slopes and the topographic and geological information. The estimation of the probability of debris flow initiation and quantitative risk assessment have been challenging issues. In order to solve this problem, in this paper, the rainfall data of XRAIN with high spatial resolution and the features of the slope failure sites were examined during heavy rainfall events. This paper also discussed the reliability of rainfall index 𝑅' to the heavy rainfall with strong long-term precipitation in July 2018, which is different from previous disasters due to the heavy rainfall with strong short-term precipitation, such as those in August 2014 and June 1999.