Intense rainfall related to a stationary front on July 3-4, 2020 triggered many landslides and floods in the southern part of Kumamoto Prefecture, Kyushu, southwestern Japan. The July 4, 2020 landslides were concentrated mainly in Ashikita and Tsunagi towns along the Yatsushiro Sea, resulting in severe damage to houses and twelve fatalities. The landslides occurred mainly in areas underlain by Jurassic accretionary complexes of the Chichibu Belt, with some of them occurring on steep upper slopes along valleys mobilized into debris flows, which traveled along stream channels and flooded the lower reaches. Most of the landslides occurred in thick weathered soil layers overlying bedrock; the slides were generally less than 20 m thick. The photograph shows a landslide that occurred on a 30° forested slope at Miyanoura (Ashikita town). The height and width of the landslide were 70 m and 40 m, respectively. A thick reddish soil layer can be seen at the head scarp, and a fault fracture zone is observed at the lower part of the landslide. Although the landslide produced large amounts of sediments and woody debris, there were no houses in the transported and depositional zone.
(Photograph & Explanation: Yasuo MIYABUCHI; July 12, 2020)
