CGRG Bibliography of Canadian Geomorphology
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Author : Eedy, R.; and Giberson, D.J.
Date : 2002.
Title : An evaluation of methods to characterize near-bed flow.
Publication : North American Benthological Society Annual meeting, Pittsburgh, Pennsylvania, 2002.
Issue :
Page(s) :
Abstract
The force of water currents near streambeds (shear velocity) influences bed composition and the distribution of benthos. Unfortunately, the standard method of measuring shear velocity (velocity profiles) is time-consuming, and the accuracy of simpler methods varies among streams. This study was performed to 1) select a method of comparing shear velocity in small patches (0.07 m2) of a medium-sized stream reach (mean annual discharge of 1.9 m3s-1) and to 2) examine the variation of shear velocity within these patches. We compared shear velocity values determined from velocity profiles to values obtained using simpler methods including mean velocity measurement, near-bed velocity measurement, and calculation of shear velocity (incorporating measurements of substrate roughness, channel shape, and mean velocity). Velocity profile shear values were strongly correlated to mean velocity and calculated shear velocity, but had only a weak correlation to near-bed velocity. Shear velocity also varied within patches, with the highest variation occurring in patches that had rough (rocky and uneven) surfaces (ANOVA, p < 0.05). Therefore, the simple measurement of mean velocity can be used to estimate relative shear velocity in patches, but substrate roughness should still be measured to identify patches with high spatial variation in shear velocity.
Bibliography of Canadian Geomorphology