Author(s): Pierre Y. Julien; S. Kawai; Deborah J. Anthony
Linked Author(s): Deborah Anthony, Pierre Y. Julien
Keywords: No Keywords
Abstract: Meandering channels typically deposit sediments near their inner bank to form point bars. Laboratory experiments with narrow sharp bends show that under identical flow conditions the configuration of point bars depends on particle size. A three-dimensional particle stability analysis determines the average orientation angle of moving bedload particles, which varies with particle diameter. The resulting sorting mechanism in meander bends has been tested with an extensive field data set of near-bed sediment transport by size fraction collected on Fall River, Colorado. Calculated results coincide with experimental observations. Field measurements of moving bedload particles in sharp meander bends show that very fine sand (ds=0.125 mm) move up the point bar while 16 mm gravel move toward the thalweg. The measured deviation angle between these two fractions reaches 20°near the bend apex as predicted analytically. Point bars are considerably smaller for coarse-sand deposits than fine sands. There is comparatively no sorting observed near stream crossings.
Year: 1997