HR: 0800h
AN: H51I-0883    [Abstracts]
TI: Improved statistical characterization of particle-size distributions in sand-bedded rivers
AU: * Huzurbazar, S
EM: lata@uwyo.edu
AF: Department of Statistics, University of Wyoming, Dept 3332 1000 E. University Avenue, Laramie, WY 82071, United States
AU: Hajek, E
EM: ehajek@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, Dept. 3006 1000 University Ave. University of Wyoming, Laramie, WY 82071, United States
AU: Lynds, R
EM: rmlynds@yahoo.com
AF: Department of Geology and Geophysics, University of Wyoming, Dept. 3006 1000 University Ave. University of Wyoming, Laramie, WY 82071, United States
AU: Heller, P
EM: heller@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, Dept. 3006 1000 University Ave. University of Wyoming, Laramie, WY 82071, United States
AU: Mohrig, D
EM: mohrig@mail.utexas.edu
AF: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, United States
AB: Measured particle-size distributions are commonly reduced to one characteristic value (e.g., median grain diameter) that is used in sediment transport modeling. While convenient, this approach cannot be used to explore the potential influence grain-size distributions may have on sediment transport and deposition. We statistically characterize grain-size distributions in samples of bed-material load, suspended load, and slackwater deposits from the sand-bedded Calamus, North Loup, and Niobrara rivers (Nebraska, USA). Transported sediment samples are best modeled with log-hyperbolic distributions, and slackwater deposits are bi- or multi-modal mixtures. Despite large overlaps in the grain sizes of bed-material-load and suspended-load samples, estimated parameters of fitted log-hyperbolic distributions show consistent differences between these samples across all rivers. Bed-material load samples have higher modes and positive (coarse-grained) asymmetry, whereas suspended load samples have lower modes and weaker asymmetry. In all three rivers, slackwater deposits contain the entire range of grain sizes present in suspended load, but with a significant component of very fine-grained (< 0.02 mm) material that is undetectable in suspended sediment samples. This suggests some degree of fractionated deposition of suspended sediment in areas of near-zero flow velocities. Ultimately, in order to explore the effect of grain-size distributions on sediment transport and river processes, these modeled distributions can be incorporated into a Bayesian hierarchical framework where standard sediment transport equations can be modeled in relation to probability-density particle curves for grain size.
DE: 1862 Sediment transport (4558)
DE: 1894 Instruments and techniques: modeling
DE: 1895 Instruments and techniques: monitoring
DE: 4558 Sediment transport (1862)
DE: 4594 Instruments and techniques
SC: Hydrology [H]
MN: 2007 Fall Meeting