Processes of Soil Erosion. by Wind

Abstract

In the past, wind erosion has orten been modeled as a series of lumped factors. with each factor embodying a number of individual erosion processes. During the last decade considerable progress has been made in formulating process equations that represent the individual sources and sinks for eroding soil. The objective. of this report is to provide an overview of some of the wind erosion processes on agricultural lands. By considering two soil states (crusted and aggregated) along with the erosion processes. one can define the temporal soil properties of dry soils that comrol soil erodibility. These temporal properties include the dry stabilities. mass fractions and size distributions of mobile and immobile soil components, as well as surface roughness. The threshold friction velocities of bare soils also depend upon surface roughness and cover of immobile clods and crusts. The transport capacity of the suspension-size soil is several times larger than the limited transport capacity for the saltation and creep-size component of horizontal soil discharge. Thus. on large fields suspension discharge ollen exceeds saltation/creep discharge. Sources of saltation/creep discharge include emrainment of loose aggregates and abrasion of immobile clods and crust. Sinks for saltation/creep discharge include trapping by surface roughness. interception by standing biomass and breakage to suspension-size. Similarly, sources for suspension discharge include emrainment of loose aggregates. abrasion of clods and crust, and breakage of saltation/creep aggregates. Sinks for suspension include interception by standing biomass and deposition on downwind immobile surfaces. Wind tunnels have been used to directly measure the parameters lor the individual wind erosion processes. Moreover. the individual processes can be assembled into physically-based wind erosion models that are applicable to a wide range of surface conditions.