Determining Fluvial Flow Conditions from Preserved Bed Set Geometry

Robert C. Mahon and Brandon Mcelroy
University of Wyoming Department of Geology and Geophysics, Laramie, WY

The downstream movement of bedforms in flowing water can be described as the combination of two components: bed form translation and bed form deformation. Previous work hypothesizes that deformation (change in shape) of bed topography is primarily a function of the suspended portion of bed material load. However, a complete experimental determination of the physical conditions resulting in bed deformation remains to be presented. This study will focus on the hypothesis that the ability of flow to suspend sediment, best characterized by the Rouse parameter, provides a primary control on the sediment bypass fraction at the bed form scale and therefore on rates and fluxes of bed deformation. A set of laboratory flume experiments will be conducted with migrating dunes on a natural sand bed to test this hypothesis. A series of experimental runs will be undertaken to measure bed deformation rates over a range of Rouse number values, {0.5≤P≤4}. Furthermore, bed set stratigraphy resulting from the migration of deforming bed forms will also be measured and a relationship between deformation rates, flow parameters and the curvature of bed set bounding surfaces will be modeled. These results have the potential for the development of new techniques by which indirect measurements of bed material load can be calculated in natural sand-bed rivers, as well as a model framework from which sediment hydrodynamics can be calculated from the curvature of preserved bed set bounding surfaces (shown to be the result of bed deformation) in the stratigraphic record.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013