Author(s): R. A. Kuhnle; D. G. Wren
Linked Author(s): Roger A. Kuhnle
Keywords: No Keywords
Abstract: Knowledge of the size of sediment in suspension is important information needed for the collection of concentration data using surrogate technologies and to further understand the processes acting in the transport of suspended sediment over dunes. Samples of suspended sediment were collected at four elevations simultaneously over two-dimensional mobile dunes in 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage to be the same as the migration rate of the dunes. The rate of change of concentration of the suspended sediment with distance from the bed for individual grain sizes was found to be related to the part of the dune over which the samples were collected. The suspended sediment concentration over the lowest third of the flow depth was nearly constant with depth over the trough of the bed forms, while over the brink point concentration varied rapidly with depth. There were intermediate rates of change, similar to measurements over a flat bed, over the rest of the dune. Differences in the vertical rates of change in grain size over different parts of a dune were reduced when the sizes were plotted relative to the mean crest elevation of the dunes rather than the local bed elevation. The Rouse equation was found to yield accurate predictions of median grain sizes above the crest level using a reference sample, while median grain size was found to be nearly constant below the level of the crest. Predictions of median suspended sediment size will be valuable to constrain suspended sediment determinations collected using surrogate technologies.
Year: 2009