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Size‐selective entrainment of bed load in gravel bed streams

Size‐selective entrainment of bed load in gravel bed streams Entrainment of mixed size gravel bed material was studied in nine reaches of three high‐power streams in Scotland and Norway. Paired measurements of at‐a‐point shear stress (estimated from velocity profiles) and bed load transport (by hand‐held sampler) were made. They extended to very high values (400 N m−2, 3.5 kg m−1 s−1). Analyses of maximum bed load diameter, mean bed load diameter, transport rates of individual size fractions, and tracer pebble movements all show some dependence of threshold shear stress for entrainment on absolute particle size, despite strong relative size effects. Precise equal mobility of all sizes was approached in the data set with the highest shear stresses and transport rates. Size‐selective transport in the streams studied is also indicated by clear downstream and downbar reductions in surface sediment size over distances too short for abrasion to be significant. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Water Resources Research Wiley

Size‐selective entrainment of bed load in gravel bed streams

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References (22)

Publisher
Wiley
Copyright
Copyright © 1989 by the American Geophysical Union.
ISSN
0043-1397
eISSN
1944-7973
DOI
10.1029/WR025i004p00627
Publisher site
See Article on Publisher Site

Abstract

Entrainment of mixed size gravel bed material was studied in nine reaches of three high‐power streams in Scotland and Norway. Paired measurements of at‐a‐point shear stress (estimated from velocity profiles) and bed load transport (by hand‐held sampler) were made. They extended to very high values (400 N m−2, 3.5 kg m−1 s−1). Analyses of maximum bed load diameter, mean bed load diameter, transport rates of individual size fractions, and tracer pebble movements all show some dependence of threshold shear stress for entrainment on absolute particle size, despite strong relative size effects. Precise equal mobility of all sizes was approached in the data set with the highest shear stresses and transport rates. Size‐selective transport in the streams studied is also indicated by clear downstream and downbar reductions in surface sediment size over distances too short for abrasion to be significant.

Journal

Water Resources Research – Wiley

Published: Apr 1, 1989

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