Predicting fractional bed load transport rates: Application of the Wilcock-Crowe equations to a regulated gravel bed river
Article first published online: 11 JUN 2009
Copyright 2009 by the American Geophysical Union.
Water Resources Research
Volume 45, Issue 6, June 2009
How to Cite
2009), Predicting fractional bed load transport rates: Application of the Wilcock-Crowe equations to a regulated gravel bed river, Water Resour. Res., 45, W06409, doi:10.1029/2008WR007320., , , and (
- Issue published online: 11 JUN 2009
- Article first published online: 11 JUN 2009
- Manuscript Accepted: 2 APR 2009
- Manuscript Revised: 25 MAR 2009
- Manuscript Received: 29 JUL 2008
- bed load;
- sediment transport
 Bed load samples from four locations in the Trinity River of northern California are analyzed to evaluate the performance of the Wilcock-Crowe bed load transport equations for predicting fractional bed load transport rates. Bed surface particles become smaller and the fraction of sand on the bed increases with distance downstream from Lewiston Dam. The dimensionless reference shear stress for the mean bed particle size (τ*rm) is largest near the dam, but varies relatively little between the more downstream locations. The relation between τ*rm and the reference shear stresses for other size fractions is constant across all locations. Total bed load transport rates predicted with the Wilcock-Crowe equations are within a factor of 2 of sampled transport rates for 68% of all samples. The Wilcock-Crowe equations nonetheless consistently under-predict the transport of particles larger than 128 mm, frequently by more than an order of magnitude. Accurate prediction of the transport rates of the largest particles is important for models in which the evolution of the surface grain size distribution determines subsequent bed load transport rates. Values of τ*rm estimated from bed load samples are up to 50% larger than those predicted with the Wilcock-Crowe equations, and sampled bed load transport approximates equal mobility across a wider range of grain sizes than is implied by the equations. Modifications to the Wilcock-Crowe equation for determining τ*rm and the hiding function used to scale τ*rm to other grain size fractions are proposed to achieve the best fit to observed bed load transport in the Trinity River.