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Critical discharge for entrainment of poorly sorted gravel
Author(s) -
Ferguson R. I.
Publication year - 1994
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290190208
Subject(s) - entrainment (biomusicology) , critical resolved shear stress , mechanics , geology , grain size , shear stress , geotechnical engineering , shear (geology) , critical distance , air entrainment , discharge , environmental science , geomorphology , shear rate , physics , petrology , thermodynamics , rheology , drainage basin , sound (geography) , sound power , rhythm , acoustics , cartography , geography
Entrainment criteria for gravel‐sized particles on river beds are usually defined in terms of shear stress, but some workers have proposed that critical‐discharge relationships are more reliable and more convenient. The critical shear stress in poorly sorted gravels is known from recent work to depend much more on relative than absolute grain size. It is shown that this effect can be included in a semi‐theoretical equation for the critical unit discharge to move individual grain sizes in a poorly sorted bed. Comparisons with published data on critical discharges in a variety of rivers show that both the sensitivity of critical discharge to grain size, and the absolute levels of critical discharge, are predicted quite well. However, any prediction of critical discharge is sensitive to the assumptions made, first about flow resistance and secondly about the critical stress to move average‐sized particles.