複断面開水路における樹林の流水抵抗に関する相当粗度係数

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書誌事項

タイトル別名
  • EQUIVALENT MANNING ROUGHNESS COEFFICIENT IN AN OPEN CHANNEL OF COMPOUND CROSS SECTION WITH TREE VEGETATION
  • 機械的擾乱と熱的擾乱が共存した密度成層場での鉛直混合に関する研究 (その2)
  • フクダンメンカイスイロ ニ オケル ジュリン ノ リュウスイ テイコウ ニ カンスル ソウトウソド ケイスウ
  • Vertical Mixing Induced by Combination of Mechanical and Thermal Stirring in Density Stratification System (2)

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抄録

The high water level, HWL. for a design flood is the most important parameter in flood control and management. It is a critical issue how to determine Manning roughness coefficient in a vegetated reach, since channelized rivers tend to be densely vegetated in last decades. Although there are several sophisticated hydrodynamic models to analyze flows in vegetated channels, flow resistance due to vegetation is usually formulated in terms of a drag force coefficient which is not always a convenient parameter in flood control management. The HWL. is usually determined from a one dimensional nonuniform flow analysis in which Manning roughness coefficient is required in describing channel perimeter's roughness such as vegetation. In this study, an equivalent Manning roughness coefficient, nv, for a vegetated reach was theoretically estimated by using a two-dimensional two-layer (2D2L) flow model that was developed by the authors. The model's performance was already confirmed by laboratory and field experiments. A functioal dependency of nv on vegetation properties such as discharge, profiles of vegetation, stem diameter, tree height, etc. was investigated. It was found that nv was kept constant independently of water depth or discharge after the vegetation being submerged.

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