Equations for the near-surface mass flux density profile of wind-blown sediments

The erosion of sediment by wind and the resulting mass flux density profile is thought to be described by a mathematical function that bears information on the mechanisms responsible for the movement of individual particles by the wind, and such functions have been studied extensively. In this study several functions are evaluated that have been proposed to describe the variation in mass flux density with height of wind-blown sediment, with the flux containing a mixture of particles in suspension and saltation, based on detailed field data at four land types in the Minqin area of north-western China, where severe wind erosion occurs. High-resolution mass flux density measurements at 50 heights, collected at 20 mm intervals to a height of 1 m above the surface, were obtained using vertically segmented samplers. Three kinds of functions fit the measured flux density profiles reasonably well, but a three-parameter modified exponential function is preferred because it contains fewer coefficients to be defined and provides a reasonably good fit to the measured mass flux density profiles. This and previous conclusions suggest that the decay with height of mass flux density of sediments dominated by saltation particles as in the present study tends to follow a modified exponential function law, but a modified power function law replaces the modified exponential function law when the height extends to a level high enough to be dominated by suspension particles. Copyright (C) 2011 John Wiley & Sons, Ltd.