Field-derived relationships for flow velocity and resistance in high-gradient streams

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• 作者：Francesco Comiti ; Luca Mao ; Andrew Wilcox ; Ellen E. Wohl ; Mario A. Lenzi
• 关键词：Step-pool ; Flow resistance ; Steep channels ; Salt tracers ; Mountain rivers
• 刊名：Journal of Hydrology
• 出版年：2007
• 期刊代码：68_00221694
• 类别：abs
• 出版时间：30 June 2007
• 卷：340
• 期：1-2
• 页码：48-62
• 文件大小：4641 K

摘要

Summary

We measured velocity and channel geometry in 10 reaches (bed gradient = 0.08–0.21) of a predominantly step-pool channel, the Rio Cordon, Italy, over a range of discharges (3–80%of the bankfull discharge). The resulting data were used to compute flow resistance. At-a-station hydraulic geometry relations indicate that in most reaches, the exponent describing the rate of velocity increases with discharge was between 0.48 and 0.6, which is within the range of published values for pool-riffle channels. The Rio Cordon data are also combined with published hydraulics data from step-pool streams to explore non-dimensional relationships between velocity and flow resistance and factors including unit discharge, channel gradient, and step geometry. Multiple regression analysis of this combined field dataset indicated that dimensionless unit discharge (q^*) is the most important independent variable overall in explaining variations in velocity and flow resistance, followed by channel slope and the ratio of step height to step length. Empirical equations are provided both for dimensionless velocity and flow resistance, but prediction of the former variable appears more reliable.