Friction angle measurements on a naturally formed gravel streambed: Implications for critical boundary shear stress
Article first published online: 9 JUL 2010
Copyright 1992 by the American Geophysical Union.
Water Resources Research
Volume 28, Issue 2, pages 411–425, February 1992
How to Cite
1992), Friction angle measurements on a naturally formed gravel streambed: Implications for critical boundary shear stress, Water Resour. Res., 28(2), 411–425, doi:10.1029/91WR02529., , and (
- Issue published online: 9 JUL 2010
- Article first published online: 9 JUL 2010
- Manuscript Accepted: 3 OCT 1991
- Manuscript Received: 8 MAR 1991
We report the first measurements of friction angles for a naturally formed gravel streambed. For a given test grain size placed on a bed surface, friction angles varied from 10° to over 100°; friction angle distributions can be expressed as a function of test grain size, median bed grain size, and bed sorting parameter. Friction angles decrease with increasing grain size relative to the median bed grain size, and are a systematic function of sorting, with lower friction angles associated with poorer sorting. The probability distributions of critical shear stress for different grain sizes on a given bed surface, as calculated from our friction angle data, show a common origin, but otherwise diverge with larger grains having narrower and lower ranges of critical shear stresses. The potential mobility of a grain, as defined by its probability distribution of critical shear stress, may be overestimated for larger grains in this analysis, because our calculations do not take into account the effects of grain burial and altered near-bed flow fields.