Estimation of the bed shear stress in vegetated and bare channels with smooth beds

Judy Q. Yang, Francois Kerger, Heidi M. Nepf

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

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≥4.3m-1), the thickness of the linear-stress layer is set by the stem diameter, leading to a simple estimate for bed shear stress. Key Points: A model to estimate bed shear stress in vegetated channels Viscous stress is linear near the bed in bare and vegetated channels Predicting velocity in the overlap region of the Law of the Wall

Original languageEnglish (US)
Pages (from-to)3647-3663
Number of pages17
JournalWater Resources Research
Volume51
Issue number5
DOIs
StatePublished - May 1 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015. American Geophysical Union. All Rights Reserved.

Keywords

  • Law of the Wall
  • bed shear stress
  • buffer layer
  • linear viscous stress
  • open channel
  • vegetated channel

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