Sediment hazard prediction with high spatial resolution by characterization of the slope failure events triggered by 2018 torrential rainfall in western Japan

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K01154
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 04010:Geography-related
• Research Institution: The University of Tokyo
• Principal Investigator: Sugai Toshihiko 東京大学, 大学院新領域創成科学研究科, 教授 (90251321)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: slope failure / debris flow / disaster / photogramｍetry / river long-profile / weathering crust / climate change / heavy rain fall

Outline of Final Research Achievements

We conducted a field survey of the 2018 western Japan heavy rain disaster site, elucidated the slope failure sediment movement, compared the topography before and after the disaster, and considered the effects of topography and geological conditions before 2018 on the sediment movement. In addition, we clarified the timing and recurrence of the sediment migration in the past by radiocarbon dating of sediments in the sedimentation area. After that, we tried the segment division of the riverbed longitudinal section and examined the estimation basis of the moving sedimentation section of the sediment. We also considered the movement of sediment and water due to the heavy rains in northern Kyushu in 2017 and the typhoon in eastern Japan in 2019.

Free Research Field

地形学

Academic Significance and Societal Importance of the Research Achievements

崩壊箇所の地形地質的条件や、頻度規模分布特性を明かにするとともに、土砂移動時に生じた露頭や砂防工事露頭の調査により、過去のイベント発生時期や間隔を解明した点は、重要である。平成29年（2017年）に一部改正された土砂災害防止法の更なる改訂が必要であること、表層崩壊連動土石流によるインフラ被害は壊滅的かつ局所的であり、土地利用規制の科学的根拠を明確化し、空間的精度と強制力を高めることが長期課題であることを示した。