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Probabilistic modelling of bed-load composition.

By Simon J. Tait, J. Heald, I.K. McEwan, M. Soressen, G. Cunningham, B. Willetts and D. Goring


NoThis paper proposes that the changes which occur in composition of the bed load during the transport of mixed-grain-size sediments are largely controlled by the distributions of critical entrainment shear stress for the various size fractions. This hypothesis is examined for a unimodal sediment mixture by calculating these distributions with a discrete particle model and using them in a probabilistic calculation of bed-load composition. The estimates of bed-load composition compare favorably with observations of fractional transport rates made in a laboratory flume for the same sediment, suggesting that the hypothesis is reasonable. The analysis provides additional insight, in terms of grain mechanics, into the processes that determine bed-load composition. These insights strongly suggest that better prediction methods will result from taking account of the variation of threshold within size fractions, something that most previous studies have neglected

Topics: Forecast model, Probabilistic model, Numerical simulation, Dragging, Shear stress, Bedform, Grain size, Particle transport, Sediments, Hydrology
Year: 2009
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Provided by: Bradford Scholars
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