Numerical simulation of aggradation and downstream fining

Yantao Cui, Chris Paola, Gary Parker

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132 Scopus citations


Rivers typically exhibit a tendency for grain size to become finer in the downstream direction. Data for a set of large-scale experiments on the aggradation of heterogeneous gravel have recently become available. These experiments show substantial downstream fining over several tens of meters. Here a decoupled numerical model for bed aggradation and downstream fining is developed in an attempt to test an existing gravel transport model against the experimental data. Generally good agreement is found between the predictions and the observations in the absence of all but trivial adjustments to the gravel transport model. The same transport relation does not perform as well for a corresponding case of uniform sediment. In all of the experiments the Froude number was close to unity, a condition which would suggest that a decoupled model might break down. Coupled and decoupled models for uniform sediment are thus compared for a case with Froude number very close to unity. They are also compared for cases in which the upstream water discharge, sediment feed rate and downstream water surface elevation vary strongly. The surprisingly good agreement between the two models suggests that concerns in the literature about the use of decoupled models may have been overstated.

Original languageEnglish (US)
Pages (from-to)185-204
Number of pages20
JournalJournal of Hydraulic Research
Issue number2
StatePublished - 1996

Bibliographical note

Funding Information:
The support of the National Science Foundation (Grant Nos. CTS 9207882 and EAR 9004756) and the Minnesota Supercomputer Institute is gratefully acknowledged. Some of the numerical work reported here was carried out on a minisupercomputer purchased with fund from the National Science Foundation (Grant No. EAR 94P05807). The authors also acknowledge the help and suggestions of Carlos Toro-Escobar and Jasim Imran.


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