Author(s): James R. Cooper; Lynne E. Frostick
Linked Author(s): Lynne Frostick, James Cooper
Keywords: No Keywords
Abstract: An investigation has been conducted into whether differences in the surface topography of unimodal, gravel deposits and bimodal, gravel-sand deposits can explain observed differences in sediment stability. The results revealed that differences in scaled, bed roughness parameters alone cannot explain these observations, but the geometrical arrangement of the surface suggested contrasting conclusions. As the two deposits became water-worked, the majority of grain structures (imbrications) became aligned in opposing directions, with the bimodal deposit exhibiting an alignment in which the a-axis of these structures was perpendicular to the flow and their b-axis was parallel to the flow. A simple steady state fluid model was used to examine the influence of these differences on sediment stability. It revealed that the enhanced mobility of the bimodal deposit is due to a higher proportion of the fluid force being carried by the finer grain fractions and a lower proportion being imposed on the larger fractions.
Year: 2009