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Estimation of the bed shear stress in vegetated and bare channels with smooth beds
Author(s) -
Yang Judy Q.,
Kerger Francois,
Nepf Heidi M.
Publication year - 2015
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2014wr016042
Subject(s) - shear stress , law of the wall , geology , channel (broadcasting) , geotechnical engineering , turbulence , laminar sublayer , sediment transport , stress (linguistics) , shear (geology) , mechanics , sediment , geomorphology , flow separation , reynolds number , engineering , petrology , linguistics , philosophy , physics , electrical engineering
The shear stress at the bed of a channel influences important benthic processes such as sediment transport. Several methods exist to estimate the bed shear stress in bare channels without vegetation, but most of these are not appropriate for vegetated channels due to the impact of vegetation on the velocity profile and turbulence production. This study proposes a new model to estimate the bed shear stress in both vegetated and bare channels with smooth beds. The model, which is supported by measurements, indicates that for both bare and vegetated channels with smooth beds, within a viscous sublayer at the bed, the viscous stress decreases linearly with increasing distance from the bed, resulting in a parabolic velocity profile at the bed. For bare channels, the model describes the velocity profile in the overlap region of the Law of the Wall. For emergent canopies of sufficient density (frontal area per unit canopy volume a ≥ 4.3 m − 1), the thickness of the linear‐stress layer is set by the stem diameter, leading to a simple estimate for bed shear stress.