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Origin of Bedforms in a Scale of Valley Width and Their Effect on the Sediment Transport in Mountain Rivers

Research Project

Project/Area Number 13650558
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 水工水理学
Research InstitutionHOKKAIDO UNIVERSITY

Principal Investigator

HASEGAWA Kazuyoshi  Hokkaido Univ. Grad. School of Eng., Prof., 大学院・工学研究科, 教授 (70001328)

Project Period (FY) 2001 – 2002
Project Status Completed (Fiscal Year 2002)
Budget Amount *help
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2001: ¥2,300,000 (Direct Cost: ¥2,300,000)
Keywordsmountain river / bedform / bifurcated channel / concentrated channel / alternation bars / sediment transport / channel blocking / alternating channel change / 河床形態 / 分岐流路 / 不安定堆積土砂 / 交互分級波
Research Abstract

In a mountain river, large scale bedforms to be in a scale of several times of the valley width can be seen, which closely correlate with the channel branching and gathering. Movable bed experiments were conducted by using sediment materials with mixed grain size to find the origin of the bedforms and their effects on the sediment transport in the downstream channels. The results showed :
(1) Double row bars generated in the initial channel under a fully spreading flow in the whole channel width (valley width) closely resembles a natural large scale bedform, then it can be concluded that the large scale bedforms are very double row bars generated by a large flood.
(2) Bifurcated and concentrated channels with large scale bedforms are deeply eroded in the portion of bends by a medium or small flow discharge. This means that large scale bedforms can be sediment resources for medium or small floods.
(3) Node points were ovserved where upstream channels concentrate and bifurcate just downstre … More am. At the points, alternating change of main flow occur from one bifurcated channel to the other one to play an important role for chenge of sediment transport rate in the downstrem channels.
Extracted experimental tests for bifurcated channel flows were carried out by using a Y-shape channel, in order to elucidate the mechanisms of alternating change of main flow. As the result, the followings ware found :
(1) The phenomenon is caused by the effect of an alternating bar in the upstream channel. It does not occur in any case with no bars.
(2) The alternating change of main flow does not arise from the migration of upstream bar, but from the storong deviation of flow toward one side bank in the upstream channel due to bar. While much sediment discharge toward one side channel drives to block the entrance, that induces change of flow course to another channel.
(3) These mechanisms could be formulated by simultaneous 1-D differential equations for bed evolution, which summarized to a dumping oscillation equation. From the equation, oscillation condition was found. Less

Report

(3 results)
  • 2002 Annual Research Report   Final Research Report Summary
  • 2001 Annual Research Report
  • Research Products

    (14 results)

All Other

All Publications (14 results)

  • [Publications] Meguro, H.: "Experimental Reproduction of the Braided Channels and Bedforms in a Mountain River"2nd IAHR Symposium on River, Coastal and Estuarine Morphodynamics. 733-742 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 目黒 嗣樹: "山地河川における分岐流路変動と土砂移動に関する実験的研究"水工学論文集. 46. 755-760 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 目黒 嗣樹: "同幅・同角度の分岐混合砂礫水路における流路変動実験"土木学会北海道支部論文報告集. 58. 406-409 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Meguro, H.: "Experimental Reproduction of the Braided Channels and Bedforms with Three Different Scale Observed in Mountain River"Jour. of Hydroscience and Hydraulic Engineering. Vol.20No.2. 141-153 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 長谷川 和義: "山地河川における分岐部流路交番現象に関する抽出実験とその解析"水工学論文集. 47. 679-684 (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Meguro, H., Hasegawa, K., Otsuka, T.: "Experimental Reproduction of the Braided Channels and Bedforms in a Mountain River"2^<nd> IAHR Symposium on River, Coastal and Estuarine Morphodynamics. 733-742 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Meguro, H., Hasegawa, K., Nakamura, K.: "Experimantal Study on Bifurcated Channel Changes And Sediment Transport in a Mountain River (in Japanese)"Annual Journal of Hydraulic Engineering, JSCE. Vol.46. 755-760 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Meguro, H., Hasegawa, K., Nakamura, K.: "Experimental Reproduction of Braided Channels and Bedforms with Three Different Scales Observed in Mountain Rivers"Jour. Of Hydroscience and Hydraulic Engineering. Vol.20,No.2. 141-153 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Hasegawa, K., Hirose, K., Meguro, H.: "Experiments and Analysis on Alternating Mainstream Change in the Bifurcated Channel in Mountain Rivers (in Japanese)"Annual Journal of Hydraulic Engineering, JSCE. Vol.47. 679-684 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Meguro, H.: "Experimental Reproduction of Braided Channels and Bedforms with Three Different Scale Obserred in Mountain Rivers"Jour. of Hydroscience and Hydraulic Engineering. Vol.20 No.2. 141-153 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] 長谷川和義: "山地河川における分岐部流路交番現象に関する抽出実験とその解析"水工学論文集. 47. 679-684 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] Meguro, H., Hasegawa, K., Otsuka, T.: "Experimental Reproduction of the Braided Channels and Bedforms in a Mountain River"2^<nd> IAHR Symposium on River, Coastal and Estuarine Morphodynamics. 733-742 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] 目黒嗣樹, 長谷川和義, 中村健作: "山地河川における分岐流路変動と土砂移動に関する実験的研究"水工学論文集. 46巻. 755-760 (2002)

    • Related Report
      2001 Annual Research Report
  • [Publications] 目黒嗣樹, 長谷川和義, 高野義智, 中村健作: "同幅・同角度の分岐混合砂礫水路における流路変動実験"土木学会北海道支部論文報告集. 58号. 406-409 (2002)

    • Related Report
      2001 Annual Research Report

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Published: 2001-04-01   Modified: 2016-04-21  

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