Numerical Simulation of the Bed Armoring Process

by Hong-Yuan Lee, Univ of Iowa, Iowa Inst of Hydraulic, Research, Iowa City, IA, USA,
A. Jacob Odgaard, Univ of Iowa, Iowa Inst of Hydraulic, Research, Iowa City, IA, USA,

Abstract: The stability of a river channel depends to a great extent on sediment characteristics. If the amount of sediment coming into a given reach for some reason becomes less than the river's sediment-transport capacity, channel degradation occurs. If the initial shear stress on the bed is such that the coarser fractions of the bed material do not move, the bed-surface material becomes progressively coarser. Ultimately, an armor coat may form that stops further degradation. A mathematical model is developed to correlate the temporal change of the composition of the bed-surface layer with changes in the rate of bed-load transport. The model is based on: Bayazit's scheme for the exchange of grain size between a surface and a subsurface layer of bed sediment; Einstein's bed-load function with modified hiding factor curve; and Karim's mixing-layer concept. The simulation gives good agreement with the flume data taken by Little and Mayer.

Subject Headings: Bed materials | Chemical degradation | Armor units | Mathematical models | River bank stabilization | Sediment transport | Shear stress

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