Author
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Hagen, Lawrence |
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Submitted to: Annals of Arid Zone
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/30/2001 Publication Date: 6/30/2001 Citation: Hagen, L.J. Processes of soil erosion by wind. Annals of Arid Zone. 2002. v. 40(3). p. 235-254. Interpretive Summary: In the past, wind erosion has been predicted using empirical factors that lumped together a number of individual erosion processes. But some of these factors could not be directly measured in wind tunnels. During the last decade considerable progress has been made in understanding erosion processes and developing mathematical descriptions of these processes. This report provides a summary of that progress. Working with individual erosion processes provides several advantages. First, the individual erosion processes can be defined in ways that allow them to be directly measured in wind tunnels. For example, for the process of abrasion of the soil surface by saltating (hopping) particles, we now have both a mathematical description and a defined measurement technique. Second, the eroding particles that are hopping and rolling along the surface can be measured and modeled separately from the suspended particles. Partitioning of these subsets of eroding particles greatly enhances our ability to determine the offsite impacts of erosion. Finally, the individual processes can be assembled into wind erosion models that are applicable to a wide range of surface conditions. Technical Abstract: In the past, wind erosion has often 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 tow soil states (crusted and aggregated) along with the erosion processes, one can define the temporal soil properties of dry soils that control 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 discharge include trapping by surface roughness, interception by standing biomass and breakage to suspension-size. Similarly, sources for suspension discharge include entrainment of loose 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 for 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. |
