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The onset of sediment transport in vegetated channels predicted by turbulent kinetic energy
Author(s) -
Yang J. Q.,
Chung H.,
Nepf H. M.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071092
Subject(s) - turbulence kinetic energy , turbulence , kinetic energy , sediment transport , sediment , mechanics , geology , range (aeronautics) , physics , channel (broadcasting) , geomorphology , materials science , classical mechanics , composite material , electrical engineering , engineering
This laboratory study advances our understanding of sediment transport in vegetated regions, by describing the impact of stem density on the critical velocity, U crit , at which sediment motion is initiated. Sparse emergent vegetation was modeled with rigid cylinders arranged in staggered arrays of different stem densities. The sediment transport rate, Q s , was measured over a range of current speeds using digital imaging, and the critical velocity was selected as the condition at which the magnitude of Q s crossed the noise threshold. For both grain sizes considered here (0.6–0.85 mm and 1.7–2 mm), U crit decreased with increasing stem density. This dependence can be explained by a threshold condition based on turbulent kinetic energy, k t , suggesting that near‐bed turbulence intensity may be a more important control than bed shear stress on the initiation of sediment motion. The turbulent kinetic energy model unified the bare bed and vegetated channel measurements.