2020 Fiscal Year Final Research Report
Estimation of flood damage area due to driftwood blocking and debris retention system based on scientific knowledge
| Project/Area Number |
18K13968
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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 25030:Disaster prevention engineering-related
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | 流木集積 / 橋梁閉塞 / 氾濫被害 / 蛇行水路 / 流木捕捉工 |
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| Outline of Final Research Achievements |
Driftwood accumulates at a bridge, which lead to flooding. However, there is almost no detailed information to control the driftwood accumulation and driftwood transport. In this study, three kinds of flume experiments were performed. First, we conducted the accumulation tests to investigate the 3D accumulation at the model bridge. The experimental results revealed the critical condition for driftwood blocking. Second, we measured the floodplain flow by PIV to estimate the flood damage area.
Third, we considered the driftwood capturing structure using a bypass channel located at the outer river bend to remove woody debris. We investigated the trapping probability of driftwood in the bypass channel. To induce the model logs toward the bypass channel, we changed the entrance position of the bypass channel and the porosity of the side wall. The results indicated that the trapping probability is highly influenced by the velocity difference between the main channel and the bypass channel.
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| Free Research Field |
防災水工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究ではまず流木集積実験から橋梁での河道閉塞率を評価した．閉塞率は全面閉塞して最大70%となった．河川氾濫を数値解析する上で流木の閉塞率の実験データはなく100%の閉塞率としているケースが多いため，非常に有用なデータが得られた．PIV計測から越流した迂回流の流量，流速分布を評価し，橋梁の上流側より下流側で流速が大きく氾濫被害が大きくなることがわかった．さらに流木被害を抑制するための対策として河川蛇行部を利用した流木捕捉工の実験を行った．流木を捕捉池部に誘導するのに適した開口部の位置，形状，捕捉池の側壁の形状・透過度を明らかにした．
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