| Project/Area Number |
18K03785
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 17040:Solid earth sciences-related
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| Research Institution | Nagasaki University |
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Principal Investigator |
MUTO Tetsuji 長崎大学, 水産・環境科学総合研究科(環境), 教授 (70212248)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2020: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2018: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Keywords | デルタ / 沖積河川 / 分流チャネル / オート層序学 / 平衡指数 / 平衡河川 / 堆積盆水深 / モデル実験 / 河川 / デルタ分流チャネル / 平衡指数モデル / 海水準 / 水槽実験 / モルフォダイナミクス |
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| Outline of Final Research Achievements |
It has long been believed that the behavior of river deltas is controlled by upstream conditions, such as variations in sediment and water discharges, which reflect the geology and climate of the hinterlands. Recent research suggests that the basin water depth as a downstream condition can also govern the morphodynamics of delta distrbutary channels. Evidence suggests that channels tend to be more stable on deltas that face deeper water basins and more prone to avulse in the opposite case. To explore this rationale, a series of model experimental runs was conducted. The results of the experiment confirm that deeper basin water suppresses delta progradation and causes less sediment to be distributed subaerially, which is accompanied by slower channel bed aggradation and more‐stabilized channels. Such a process can be quantitatively described by the grade index model, which is applicable to natural deltas and might help in the evaluation of the stability of delta distributary channels.
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| Academic Significance and Societal Importance of the Research Achievements |
デルタを造る沖積河川チャネルの動態と変遷がデルタ前縁海底の水深に強く規制されることを実験で実証した初めての研究である。仮説を提供した平衡指数モデル（オート層序理論の一つ）を裏付けるとともに、それとは全く独立に提唱されていた海岸線自動後退理論（1992年）との統合的理解をもたらす成果が、本研究によって得られた。
下流域沖積河川の動態の理解は防災管理の観点からも重要であり、本研究成果はその方面に基礎的知見を提供する。長期的に観ると、深い海に流入する河川と浅い海に流入する河川とでは氾濫や流路変更のリスクが大きく異なるはずである。河川が流入する海域の深さに留意することの重要性に気付かせる成果である。
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