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Wind Erosion Prediction System: Erosion Submodel
Lawrence J. Hagen
Abstract
An overview of the tasks of the erosion submodel of the Wind Erosion Prediction System
(WEPS) is presented with emphasis on the prediction equations for the saltation/creep and
suspension components. These tasks begin with calculation of surface threshold velocities
and end with periodic updates in surface conditions caused by the soil loss and deposition
that occur during erosion. Wind erosion equations for a uniform surface during
quasi-steady conditions were derived, based on the principle of conservation of mass. In
the first equation, the major processes involved in saltation/creep creation and transport
were simulated. These processes included direct emission of loose material, entrainment of
material abraded from exposed clods and crust, breakage of saltation/creep aggregates to
suspension-size, trapping of saltation/creep when transport capacity is exceeded on
microrelief, and interception by plant stalks. In the second equation, the major processes
involved in creation and transport of the suspension component of wind erosion were
simulated. These processes included emission of loose material, abrasion from exposed
clods and crusts, and breakage of the saltation/creep to form suspension-size aggregates.
A downward flux to the surface of coarse fractions of the suspension component also was
simulated in portions of the simulation region, where saltating aggregates were not
present. |
