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Sensitivity of bed shear stress estimated from vertical velocity profiles: the problem of sampling resolution
Author(s) -
Biron Pascale M.,
Lane Stuart N.,
Roy André G.,
Bradbrook Kate F.,
Richards Keith S.
Publication year - 1998
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/(sici)1096-9837(199802)23:2<133::aid-esp824>3.0.co;2-n
Subject(s) - geology , shear stress , shear velocity , acoustic doppler velocimetry , critical resolved shear stress , shear (geology) , geotechnical engineering , open channel flow , flow (mathematics) , mechanics , laser doppler velocimetry , shear rate , materials science , turbulence , medicine , petrology , blood flow , physics , viscosity , composite material
Bed shear stress in open channel flows is often estimated from the logarithmic vertical velocity profile. However, most measuring devices used in the field do not allow for flow velocity to be measured very close to the bed. The lack of near‐bed measurements is a critical loss of information which may affect bed shear stress estimates. Detailed velocity profiles obtained from a field acoustic Doppler velocimeter over three different bed roughnesses clearly show that the inclusion of near‐bed points is critical for the estimation of bed shear stress in a shallow river environment. Moreover, the results indicate that using the full flow depth instead of the bottom 20 per cent of the profile generates an underestimation of the shear stress when flow is uniform. © 1998 John Wiley & Sons, Ltd.