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Flow resistance and hydraulic geometry in contrasting reaches of a bedrock channel

Ferguson, R.I.; Sharma, B.P.; Hardy, R.J; Hodge, R.A.; Warburton, J.

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Authors

B.P. Sharma



Abstract

Assumptions about flow resistance in bedrock channels have to be made for mechanistic modeling of river incision, paleoflood estimation, flood routing, and river engineering. Field data on bedrock flow resistance are very limited and calculations generally use standard alluvial-river assumptions such as a fixed value of Manning's n. To help inform future work we measured how depth, velocity and flow resistance vary with discharge in four short reaches of a small bedrock channel, one with an entirely rock bed and the others with 20%-70% sediment cover, and in the alluvial channel immediately upstream. As discharge and submergence increase in each of the partly or fully alluvial reaches there is a rapid increase in velocity and a strong decline in both n and the Darcy-Weisbach friction factor f. The bare-rock reach follows a similar trend from low to medium discharge but has increasing resistance at higher discharges because of the macro-roughness of its rock walls. Flow resistance at a given discharge differs considerably between reaches and is highest where the partial sediment cover is coarsest and most extensive. Apart from the effect of rough rock walls, the flow resistance trends are qualitatively consistent with logarithmic and variable-power equations and with non-dimensional hydraulic geometry, but quantitative agreement using sediment D84 as the roughness height is imperfect.

Citation

Ferguson, R., Sharma, B., Hardy, R., Hodge, R., & Warburton, J. (2017). Flow resistance and hydraulic geometry in contrasting reaches of a bedrock channel. Water Resources Research, 53(3), 2278-2293. https://doi.org/10.1002/2016wr020233

Journal Article Type Article
Acceptance Date Feb 22, 2017
Online Publication Date Mar 22, 2017
Publication Date Mar 22, 2017
Deposit Date Feb 22, 2017
Publicly Available Date Sep 22, 2017
Journal Water Resources Research
Print ISSN 0043-1397
Electronic ISSN 1944-7973
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 53
Issue 3
Pages 2278-2293
DOI https://doi.org/10.1002/2016wr020233

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Published Journal Article (Advance online version) (1.4 Mb)
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Copyright Statement
Advance online version R. I. Ferguson, B. P. Sharma, R. J. Hardy, R. A. Hodge, J. Warburton, (2017) Flow resistance and hydraulic geometry in contrasting reaches of a bedrock channel, Water resources research, 53(3): 2278-2293, 10.1002/2016WR020233 (DOI). To view the published open abstract, go to https://doi.org/10.1002/2016WR020233


Published Journal Article (Final published version) (2.3 Mb)
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Copyright Statement
Final published version





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