2005 Fiscal Year Final Research Report Summary
A Method for Restoring the River Environment by Restoring Meanders
| Project/Area Number |
15360271
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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 | Civil Engineering Research Institute of Hokkaido (CERI) |
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Principal Investigator |
WATANABE Yasuharu CERI, River Engineering Div., Director, 環境水工部・河川研究室, 室長 (00344424)
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| Co-Investigator(Kenkyū-buntansha) |
YAMASHITA Shoji CERI, Water Environmental Engineering Div., Director, 環境水工部・環境研究室, 室長 (20414162)
HASEGAWA Kazuyoshi Hokkaido University, Graduate School of Engineer, Prof., 大学院・工学研究科, 教授 (70001328)
NAKAMURA Futoshi Hokkaido University, Graduate School of Aguriculture, Prof., 大学院・農学研究科, 教授 (90172436)
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| Project Period (FY) |
2003 – 2005
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| Keywords | River environment / Meandering Restoration / Shibetsu River / River channel variation / Bent channel / 2 Way channel / Model of river channel variation / Restoration |
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| Research Abstract |
Research was performed from 2003 to 2005 toward developing a method of reconnecting a cut-off meander on the Shibetsu River. Previous surveys at the test site showed that two-channel restoration in which the meander channel is reconnected while the straightened channel is maintained has promise with respect to flood control and environmental restoration. The findings are summarized here.
1)In movable-bed hydraulic model tests to reproduce bank erosion at river channels where mid-scale sand waves occur, the most suitable bed materials were those low in specific gravity and viscosity.
2)From field surveys, a method for studying the optimum channel centerline at the divergence and confluence of the two channels was developed based on the shapes of the restored channel and the straightened channel. When channel bifurcation is conducted, riverbed degradation at the confluence cannot be ignored.
3)At riverbank locations of sharply redirected flow, cherry salmon were observed in higher population densities and more diverse age breakdowns when fallen trees were placed than when no fallen trees were placed. Such placing is expected to be effective in fostering a favorable habitat for fishes.
4)By surveying the pollutant budget of the oxbow lake (the cut-off meander) and by constructing a model for estimating the water quality, the applicability of the model was confirmed. By developing a model for estimating the ground water level in wetlands, the effect of changes in river water level on changes in ground water level near the rivers were clarified.
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