2017 年 70 巻 4 号 p. 31-42
An extremely heavy rainfall was observed in the northern part of Kyushu, Japan in July 2017. For example, the highest daily rainfall was 803 mm on July 5, 2017 at Kurokawa, Asakura-City of Fukuoka Prefecture. The heavy rainfall caused many slope failures, debris-flows, sediment-flows and floods, which killed 37 people at the current stage. Phenomena such as surface slope failures and sediment-flows were concentrated around the eastern part of Asakura-City. They flowed down as floods and damaged many residential areas. The bedrock where the phenomena occurred was not only weathered granite but also weathered schist included in Sangun metamorphic rocks. It is a very important feature that enormous driftwood has discharged by sediment-flows, floods and so on. Some large failures also occurred out of Asakura-City. In Hita-City of Oita Prefecture, a large failure with a width of ca. 200 m, a length of ca. 350 m and a depth of ca. 15 m occurred and blockaded Ono-river. Because this disaster caused serious damage to surrounding areas, the comprehensive countermeasures such as construction of sabo-facilities and setting warning-evacuation system must be needed.
