| Project/Area Number |
15380098
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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 |
林学・森林工学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
YAMADA Takashi Hokkaido Univ., Grad.School of Agri., Asso, Prof., 大学院・農学研究科, 助教授 (20333635)
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| Co-Investigator(Kenkyū-buntansha) |
IRASAWA Michiya IWATE Univ., Grad.School of Agri., Asso, Prof., 農学部, 助教授 (40343024)
YANAI Seiji Hokkaido Institute of Technology School of Eng., Prof., 工学部, 教授 (20337009)
KIKUCHI Shunichi Hokkaido Univ., Grad.School of Agri., Assi, Prof., 大学院・農学研究科, 助手 (10250490)
AKIYAMA Kazuya Public Works Research Institute., Senior Researcher, 土砂管理研究グループ, 主任研究員 (50355898)
佐藤 弘和 北海道立林業試験場, 森林環境部, 研究職員
田中 秀基 独立行政法人土木研究所, 土砂管理研究グループ, 主任研究員 (00391623)
山越 隆雄 独立行政法人土木研究所, 土砂管理研究グループ, 研究員 (10355860)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2003: ¥3,600,000 (Direct Cost: ¥3,600,000)
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| Keywords | land-use development in watershed / actual situation of fine sediment discharge / mechanism of fine sediment yield / biosphere / hydrological observation / hydraulic model test / physical measures development / methodology of biosphere conservation in watershed |
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| Research Abstract |
Concentration of solids and organic fine solids in the stream water were measured in a forested catchments where selective-cutting had been carried out. Total fine sediment and organic fine solids concentrations from selective cutting catchments were significantly higher after cutting as compared with those before cutting. The processes underlying land and riparian degradation by quantifying soil erosion and gully growth in slopes adjacent to cropland were examined. The concentration of suspended sediments was consistently higher in cultivated catchments where gully expansion causes 2-3 times more landslides than occur in forested catchments.
On the basis of these soil erosion and fine sediment discharge situation, erosion velocity equation for cohesive soil was proposed by the newly developed surface shear test equipment and hydraulic model tests.
Relation between soil surface cohesion of over-saturated layer and water contents at 5 mm depth revealed that as water content increased, soil surface cohesion fell exponentially. Meanwhile, erosion velocity decreased when cohesion increased, however it was increased sharply as the friction velocity increased.
Sediment discharge prediction method were newly developed on the base of this equation and physical methods of restriction and control of fine sediment discharge for biosphere conservation in watershed were proposed.
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