2003 Fiscal Year Final Research Report Summary
A stud on the mechanism of the formation of multiple and braded bar channels
| Project/Area Number |
13450198
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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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| Research Field |
水工水理学
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| Research Institution | Hokkaido University |
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Principal Investigator |
SHIMIZU Yasuyuki Hokkaido University, Grad.School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (20261331)
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| Co-Investigator(Kenkyū-buntansha) |
WATANABE Yasuharu Hokkaido Civil Engineering Research Institute, Head of River Laboratory, 河川研究室, 室長(研究職) (00344424)
HASEGAWA Kazuyoshi Hokkaido University, Grad.School of Engineering, Professor, 大学院・工学研究科, 教授 (70001328)
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| Project Period (FY) |
2001 – 2003
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| Keywords | Braided Bars / Multiple Low Bars / River Bed Deformation / Meandering Channel / Numerical Model / Experiment / 植生 / 分岐 |
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| Research Abstract |
Mechanism of the generation and formation of multiple bars and braided stream were studied by experimentally, numerically and theoretically.
Shimizu performed a series of physical experiment using a flume with moveable bed. At first, water discharge is supplied and natural bar pool bed topography is generated. Then grass seeds were strewed on the bar formed and grown up for a few weeks. The water supply was continued and the effect of vegetation to bed and bank erosion was investigated. A numerical model is successfully developed to reproduce the bar formation and bank erosion observed in the experiments. The numerical model is applied to study the flow and bed deformation observed during a flood of the Appetsu River of the August in 2003.
Hasegawa performed an experiment to simulate the flow and sediment diversion and conversion in braided stream. The importance of the alternating bar characteristics was found by the experiment and a theory to explain this effect is proposed. This results was applied to the channel diversion of the Shibetsu River, and the sediment transport and the bar formation were explained.
Watanabe performed an experiment focused on the effect of unsteady flow to the bar generation. The flow discharge hydrograph was determined to produce the transformation of bars from alternate bars to multiple bars. It was found that the historical effect is very important in for the transformation of bars in the moveable bed channels.
Consequently, the framework of the generation of multiple bars and braided bars were investigated systematically and a theory and a numerical model were proposed to reproduce the actual channel formation in the alluvial rivers.
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