Flow resistance equations for gravel-and boulder-bed streams
Alternative general forms are considered for equations to predict mean velocity over the full range of relative submergence experienced in gravel- and boulder-bed streams. A partial unification is suggested for some previous semiempirical models and physical concepts. Two new equations are proposed: a nondimensional hydraulic geometry equation with different parameters for deep and shallow flows, and a variable-power resistance equation that is asymptotic to roughness-layer formulations for shallow flows and to the Manning-Strickler approximation of the logarithmic friction law for deep flows. Predictions by existing and new equations using D 84 as roughness scale are compared to a compilation of measured velocities in natural streams at relative submergences from 0.1 to over 30. The variable-power equation performs as well as the best existing approach, which is a logarithmic law with roughness multiplier. For predicting how a known or assumed discharge is partitioned between depth and velocity, a nondimensional hydraulic geometry approach outperforms equations using relative submergence. Factor-of-two prediction errors occur with all approaches because of sensitivity to operational definitions of depth, velocity, and slope, the inadequacy of using a single grain-size length scale, and the complexity of flow physics in steep shallow streams.
Ferguson, R. (2007). Flow resistance equations for gravel-and boulder-bed streams. Water Resources Research, 43(5), Article W05427. https://doi.org/10.1029/2006wr005422
|Journal Article Type||Article|
|Publication Date||May 22, 2007|
|Deposit Date||Oct 6, 2008|
|Publicly Available Date||Mar 24, 2010|
|Journal||Water Resources Research|
|Peer Reviewed||Peer Reviewed|
Published Journal Article
Ferguson, R. I, (2007), 'Flow resistance equations for gravel-and boulder-bed streams', Water resources research, 43, 5, W05427, 10.1029/2006WR005422 (DOI). To view the published open abstract, go to https://doi.org and enter the DOI.
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