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Title: Sediment transport in hyperconcentrated flows in sand-bed streams of volcanic origin
Authors: Brown, Bobby J.
Keywords: Hyperconcentrated flow
Rheological properties
Sediment concentration
Sediment discharge
Sediment transport
Volcanic ash
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-88-18.
Description: Technical Report
Abstract: This study advances the understanding of sediment transport of bed material discharged in sand bed channels through application of recently developed theoretical concepts related to the effects of high concentration of suspended sediment on rheological properties of the water-sediment mixture. The study demonstrates the utility of developing empirical adjustment coefficients for fine material concentration that can be used in the Colby method for predicting total bed material discharge from gaging and sediment sampling data commonly available to the engineer. The prototype data set used in the study was collected and reported by the US Geological Survey at four gaging and sediment sampling stations along a 27-mile reach of the Cowlitz and Toutle rivers, Washington, during 1 October 1981-30 September 1982. The data set included stream gaging measurements, bed material samples, and depth-integrated suspended sediment measurements. The modified Einstein method was used to estimate the total bed material discharge, and the fluid properties were varied according to recently developed methodologies that take into account the increase in viscosity and density due to suspended sediment concentration. A sensitivity analysis of the effect of viscosity on the estimated bed material discharge by the modified Einstein method and a comparison of the unmeasured sediment discharge to results obtained by other investigators showed that this method provides a reasonably accurate estimate of the total bed material discharge for turbulent hyperconcentrated flows up to total suspended sediment concentrations of approximately 40 percent by weight. A comparison between total bed material discharge calculated by Colby's method and the prototype data set illustrated that Colby's adjustment coefficient for fine sediment concentration was inadequate for the Cowlitz and Toutle rivers. Colby's method consistently underpredicted the bed material discharge. The assumption was made that Colby's adjustment coefficients for median bed material size and temperature were applicable, and a new set of adjustment coefficients for fine sediment concentration has been developed that should be applicable to streams of similar geometry and flow conditions in the Mount St. Helens area and perhaps in the Cascade Mountain Range. The utility of developing a similar set of curves for any stream from data commonly available to the engineer has been demonstrated.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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