土砂災害からの避難のための雨量観測網と避難基準の構築に係る研究

Abstract

This year, damage caused by wind and flood damage is on the rise. In particular, in the case of landslides, the realization of early evacuation is a serious and urgent issue. With the aim of achieving this goal, we analyzed the collapse points, topography (slope angle), geology, and rainfall caused by landslides caused by heavy rains in Hiroshima Prefecture in 2018. Regarding topography (slope angle) analysis, it was found that special attention should be paid to landslides when the slope angle is between 30° and 40°. Geological analysis revealed that granitic geology is more likely to cause landslides. In the rainfall analysis, it was found that the analytical rainfall in the same mesh and the AMeDAS values tend to be larger, and that although the yellow zone and red zone are being developed and the capture rate is increasing, the accuracy rate is decreasing, which is one of the reasons why it is difficult for residents to take evacuation actions. Regarding the proposal to install rain gauges in Toyota City, we conducted an analysis using the simultaneous occurrence rate, which is a method for evaluating heavy rainfall, and found that the number of rain gauges in the current Toyota City other than the former Toyota City is small. It was found that in order to secure the same occurrence rate as in the former Toyota City in a place other than the former Toyota City, 58 rainfall points with a distance of approximately 4 km between the rainfall points would be required in the place other than the former Toyota City. Based on this proposal, we found it necessary to conduct multi-point, real-time rainfall observation (it is important to know the dangerous amount of rainfall for landslides at high altitudes). We also thought it necessary to propose a system that can calculate the soil rainfall index and snake using two methods from actual rainfall observation data and predicted rainfall values from the Japan Meteorological Agency, and issue alarm information in real time.