| Project/Area Number |
18K18917
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| Research Category |
Grant-in-Aid for Challenging Research (Exploratory)
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| Allocation Type | Multi-year Fund |
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| Review Section |
Medium-sized Section 25:Social systems engineering, safety engineering, disaster prevention engineering, and related fields
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Hotta Norifumi 東京大学, 大学院農学生命科学研究科(農学部), 准教授 (00323478)
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| Co-Investigator(Kenkyū-buntansha) |
山口 弘誠 京都大学, 防災研究所, 准教授 (90551383)
今泉 文寿 静岡大学, 農学部, 教授 (80378918)
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| Project Period (FY) |
2018-06-29 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000)
Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2019: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2018: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
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| Keywords | フラッシュフラッド / UAV(無人航空機) / 地形測量 / 熱赤外画像 / 雨量観測 / 気象観測 / 危険雨量 / 地形条件 / 降雨モニタリング / 無人航空機 |
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| Outline of Final Research Achievements |
To predict a debris flow that reaches downstream, we monitored debris-flow surges flowing into the fan apex and carried out multi-temporal and high-definition topographic surveys in the debris-flow fan within the Ichino-Sawa torrent. Avulsion and channelization processes in debris-flow fans lead to the discharge of stored sediment involved with the rainfall-runoff process as flash floods via substantial changes in fan topography. Before avulsion, channel plugging by backfilling deposition in the channel increases elevation at the fan apex. Consequently, slopes around the fan apex exceeded the equilibrium slope for unsaturated debris flows, with which a debris flow can reach far downstream. The increased slopes around the fan apex, in addition to the stages in the avulsion and channelization cycle, are responsible for triggering “high-risk” debris flows. The intensive topographic surveys would allow us to identify the risk throughout monitoring the fan morphology.
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| Academic Significance and Societal Importance of the Research Achievements |
従来のフラッシュフラッド研究の多くが局所豪雨の評価・予測の枠組み内で実施されてきた．それに対して，降雨－流出時に生じる河床材料の侵食が急激な流出ピークの形成に寄与することでフラッシュフラッドの危険性を高めることを，土石流の流下プロセスと地形形成の相互作用を解明したうえで示した点が本研究の学術的な意義である．近年の技術革新によって安価・簡便に実施可能になった高頻度・高精細な地形測量によって，フラッシュフラッドの発生予測精度を向上させることが可能であることを示した点に社会的な意義がある．
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