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AGU: Water Resources Research

 

Keywords

  • bed shear stress
  • channel morphology
  • flow convergence
  • hydrodynamics
  • numerical modeling
  • pool-riffle
  • river modeling
  • velocity reversal

Index Terms

  • Hydrology: Geomorphology: fluvial
  • Hydrology: Modeling
  • Hydrology: River channels
  • Hydrology: Sediment transport
Abstract
Cited By (5)
 

Abstract

Flow convergence routing hypothesis for pool-riffle maintenance in alluvial rivers

Michael L. MacWilliams Jr.

Environmental Fluid Mechanics Laboratory, Department of Civil and Environmental Engineering, Stanford University, Stanford, California, USA

Joseph M. Wheaton

River Basin Dynamics and Hydrology Research Group, University of Wales, Aberystwyth, UK

Department of Land, Air, and Water Resources, University of California, Davis, California, USA

Gregory B. Pasternack

Department of Land, Air, and Water Resources, University of California, Davis, California, USA

Robert L. Street

Environmental Fluid Mechanics Laboratory, Department of Civil and Environmental Engineering, Stanford University, Stanford, California, USA

Peter K. Kitanidis

Environmental Fluid Mechanics Laboratory, Department of Civil and Environmental Engineering, Stanford University, Stanford, California, USA

The velocity reversal hypothesis is commonly cited as a mechanism for the maintenance of pool-riffle morphology. Although this hypothesis is based on the magnitude of mean flow parameters, recent studies have suggested that mean parameters are not sufficient to explain the dominant processes in many pool-riffle sequences. In this study, two- and three-dimensional models are applied to simulate flow in the pool-riffle sequence on Dry Creek, California, where the velocity reversal hypothesis was first proposed. These simulations provide an opportunity to evaluate the hydrodynamics underlying the observed reversals in near-bed and section-averaged velocity and are used to investigate the influence of secondary currents, the advection of momentum, and cross-stream flow variability. The simulation results support the occurrence of a reversal in mean velocity and mean shear stress with increasing discharge. However, the results indicate that the effects of flow convergence due to an upstream constriction and the routing of flow through the system are more significant in influencing pool-riffle morphology than the occurrence of a mean velocity reversal. The hypothesis of flow convergence routing is introduced as a more meaningful explanation of the mechanisms acting to maintain pool-riffle morphology.

Received 29 June 2005; accepted 19 June 2006; published 31 October 2006.

Citation: MacWilliams, M. L., Jr., J. M. Wheaton, G. B. Pasternack, R. L. Street, and P. K. Kitanidis (2006), Flow convergence routing hypothesis for pool-riffle maintenance in alluvial rivers, Water Resour. Res., 42, W10427, doi:10.1029/2005WR004391.

Cited By

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