Kumamoto and Kogoshima prefectures are located in the southern Kyushu district of western Japan. In July 2020, a warm, humid air front triggered the delayed rains of the rainy season, resulting in torrential rains in many parts of Japan, especially in Kyushu. In particular, heavy downpours occurred in the southern Kyushu district on July 4th, causing severe damage to much of the infrastructure. Details could not be analyzed as usual because some branch office of local government were also damaged by floods. The spatial distribution of precipitation in the Kuma River basin, in the southern part of Kumamoto, was characterized by the uniformity of 400–500 mm on July 3rd and 4th. Finally, emergency warnings of torrential rain were issued for the southern Kumamoto and the northern Kagoshima Prefectures by Japan Meteorological Agency (JMA) at 4:50 a.m., July 4th, 2020. Then, the active rain front gradually shifted towards northern Kyushu. Again, torrential rain fell on northern Kyushu in the afternoon due to a stagnant rainy season front, and the JMA issued an emergency warning for a localized torrential downpour for parts of Fukuoka, Saga and Nagasaki prefectures at 4:30 pm. Gradually, the damage status involving geodisasters such as several types of slope failures, road subsidence, damage of the river levee was reported by local governments in each area where there had been emergency warnings.

Based on the brief report of the pre-investigation team from the Kyushu branch of the Japan Geotechnical Society (JGS) in the first week after the disaster on July 4th, the geo-research teams investigated the following: 1) landslides; 2) damaged roads; 3) damaged river levees, and 4) any geotechnical infrastructures which were partially damaged and may be even more severely damaged by the next torrential rain. This reconnaissance report introduces the geological features in Kyushu, the analysis of precipitation distribution and geotechnical damages on the slope failures, road failures and river embankments based on reports obtained from July 4th to August 31st, 2020.

熊本县和鹿儿岛县位于日本西部的九州南部地区。2020年7月，温暖潮湿的空气前沿引发了雨季降雨的延迟，导致日本许多地区，特别是九州的暴雨。特别是7月4日，南部九州地区发生了倾盆大雨，对大部分基础设施造成了严重破坏。无法像往常一样分析细节，因为当地政府的一些分支机构也受到洪水的破坏。熊本南部的熊马河流域降水的空间分布以7月3日和4日的400-500毫米均匀度为特征。最后，日本气象厅（JMA）在凌晨4:50向熊本南部和鹿儿岛北部地区发出了暴雨的紧急警告，2020年7月4日。随后，活跃的降雨阵线逐渐转移到了九州北部。再次，由于雨季停滞，下午在九州北部出现了暴雨，JMA在下午4:30发出了针对福冈，佐贺和长崎县部分地区局部暴雨的紧急警告。逐渐地，在每个地方都有紧急警报的地方政府报告了涉及地质灾害的破坏状况，例如几种类型的边坡破坏，道路沉降，河堤的破坏。佐贺县和长崎县在下午4:30。逐渐地，在每个地方都有紧急警报的地方政府报告了涉及地质灾害的破坏状况，例如几种类型的边坡破坏，道路沉降，河堤的破坏。佐贺县和长崎县在下午4:30。逐渐地，在每个地方都有紧急警报的地方政府报告了涉及地质灾害的破坏状况，例如几种类型的边坡破坏，道路沉降，河堤的破坏。

根据日本岩土学会（JGS）九州分社在7月4日灾难发生后的第一周的调查报告摘要，地质研究小组进行了以下调查：2）道路损坏；3）损坏的河堤，以及4）任何土力工程基础设施，部分被破坏，而下一场暴雨可能会造成更严重的破坏。这份侦察报告介绍了九州的地质特征，基于2020年7月4日至8月31日获得的报告，分析了坡度破坏，道路破坏和河堤的降水分布和岩土破坏。