| Project/Area Number |
20K14840
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 22040:Hydroengineering-related
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
Azhikodan Gubash 東京都立大学, 都市環境科学研究科, 助教 (50821740)
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Project Status |
Completed (Fiscal Year 2023)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2023: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2022: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2021: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Keywords | Chikugo River estuary / Sediment transport / Erosion / Human activities / Climate disasters / Morphological change / Long-term scale / Seasonal scale / Morphological changes / long-term / tidal forcing / flood disaster / erosion / sediment transport / deposition / morphodynamics / bed elevation / sediment supply / topographic change / peak flood / Morphology / Topographic survey / Salinity intrusion / Climate change |
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| Outline of Research at the Start |
Periodic measurement of the bottom topography and temporal variation of salinity, turbidity, and river discharge will be conducted in the upstream of the Chikugo River estuary. Further, comparative assessment of the measured estuarine morphology with past 15-year data will be carried out to analyse the effect of factors such as changes in salinity intrusion and river discharge patterns on estuarine morphology over time. Lastly, the reproduction of present estuarine morphology and future prediction of morphological evolution in the channel under a changing climatic scenario will be carried out.
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| Outline of Final Research Achievements |
The estuarine channel experienced deposition by the tidal sediment transport during the dry season. The channel volume rapidly increased due to the erosion of these mud deposits by the strong flood in the flood season. The bed elevation rises again during the post-flood season by the tides and continues until the next flood. Hence, the estuarine morphology showed a deposition trend during the dry season and an erosion trend during the flood season on a seasonal scale. On a long-term scale, the study period (P) was divided into 3: the period of 1) human activities (1953-1998), 2) no human activities and no disasters (1998-2003) and 3) climate disasters (2003-2022). During P1, the riverbed was lowered due to extensive human activities (dredging, sand mining, etc). During P2, the bed elevation increased by 0.5-1m by the tidal influence (absence of strong flood events). During P3, the bed elevation decreased as extreme flood disasters eroded the sediment deposited upstream of the estuary.
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| Academic Significance and Societal Importance of the Research Achievements |
The study describes the long-term and seasonal changes in estuarine morphology, considering the effects of human activities, tidal forcing, and climate disasters; which can help to plan and manage the water environment suitably and minimize the impact of climate change on biodiversity and wildlife.
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