| Project/Area Number |
21H01434
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 22040:Hydroengineering-related
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
武藤 裕則 徳島大学, 大学院社会産業理工学研究部(理工学域), 教授 (40263157)
角 哲也 京都大学, 防災研究所, 教授 (40311732)
小柴 孝太 京都大学, 防災研究所, 助教 (80883157)
竹門 康弘 京都大学, 防災研究所, 准教授 (50222104)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥17,550,000 (Direct Cost: ¥13,500,000、Indirect Cost: ¥4,050,000)
Fiscal Year 2023: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Fiscal Year 2022: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2021: ¥8,580,000 (Direct Cost: ¥6,600,000、Indirect Cost: ¥1,980,000)
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| Keywords | 土砂還元 / 流砂連続性 / 画像解析 / 側岸侵食過程 / 生態機能評価 / Numerical simulation / TELEMAC2D / Model calibration / Suspended sediment / Buech River / flood pulses / Sediment pulses / Replenishment Scenarios / Sediment Replenishment / Imaged- based-technique / LSPIV and STIV / Basegrain / Naka River / Sediment erosion rate / Flushing flow / SR assessment method |
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| Outline of Research at the Start |
ダムで遮断された流砂連続性の回復手段として、ダム下流への土砂還元（置き土）が実施されている。ここでは、粒径集団ごとの土砂収支に加えて、流量－流砂レジームを自然に近い形でいかに再現するかが大きな課題となる。本研究では、土砂還元手法の高度化に向けて、洪水波形中の土砂供給のデザイン手法や下流で新たに形成される砂州の生態機能をいかに評価するか、などの課題に取り組む。具体的には、徳島県那賀川（長安口ダム）における置土の侵食過程をモニタリングカメラによる現地観測により記録し分析するとともに、TELEMAC3Dをベースとした置土侵食と砂州形成の数値解析を、同様な試みを実施しているフランス電力と共同で行う。
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| Outline of Annual Research Achievements |
Installation of additional monitoring systems of two IP Cameras, one on the bridge and one on the left bank of the river, for real-time sediment erosion patterns at the sediment replenishment site and surface flow velocities near the SR site. Additionally, install one turbidity meter to measure suspended sediment concentration. In total, four times field surveys at Naka River for measuring Grain Size Distribution (GSD) along four gravel bars, a drone for the sediment replenishment site, and morphological changes. Field visit and data collection of Buech River in France. Develop a comprehensive assessment method for sediment replenishment in the Naka and Buch Rivers, considering the erosion efficiency of replenished sediment and downstream eco-hydro-geomorphological impacts. We established a two-dimensional model to simulate the hydro-morphological changes with the implementation of SR in the Naka River based on TELEMAC-2D coupled with Gaia. The model was then calibrated and validated for previous flood events and the 2022 flood event. Then, based on the calibrated model, we utilized it to simulate several scenarios to investigate the optimization strategies of SR by considering replenishment erosion and downstream responses. There are rare significant floods that occurred recently in the Nagayasuguchi dam, indicating that an increase in flushing magnitude is difficult to implement under dam management.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
A Ph.D. study has been completed based on this project. We conducted field surveys in the Buech River in France and collected data on river cross-section, grain size distribution, and ecological indicators. Furthermore, we calibrated and validated the TELEMAC2D model and started the sensitivity analysis for optimal parameter selection. We compared Naka and Buech Rivers based on the developed comprehensive assessment approach. We have published this work and presented it at various conferences and meetings. We investigated the impacts of the flushing flow and the sediment volumes. We designed three scenarios for double flood pulses and additional sediment replenishment arrangements.
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| Strategy for Future Research Activity |
Based on the well-developed 2D model, we will optimize the sediment replenishment works in the Naka River. We will propose a guideline for sediment replenishment implementation. The downstream morpho-ecology requires optimal flushing flow, volume, and sediment supply from the SR site to maintain its positive functionality. We will check the feasibility of implementing the double stockpiles at Kohama.
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