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,

Document Type: Proceeding Paper

Part of: Water for Resource Development


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: Numerical models | Bed materials | Armor units | Chemical degradation | Shear stress | Water flow | Sediment | Streamflow

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