A model for predicting aeolian sand drift and dust entrainment on scales from paddock to region

This paper describes a Wind Erosion Assessment Model (WEAM) for the estimation of sand drift and dust entrainment in agricultural areas. Both the sand drift and dust entrainment parts of the model are physically based, utilising a combination of established and recent theoretical and experimental results. Key components of the model include the Owen equation for the saltation flux; the observed and theoretically predicted proportionality between saltation flux and dust entrainment by saltation bombardment; theoretical and experimental results on the amelioration of wind erosion by nonerodible roughness; and new experimental results on the suppression of erosion by surface moisture. The size distribution of the particles on the soil surface (in their natural state) is used as a primary parameter. The model is restricted to a description of the mobilisation of sand and dust in erosion source areas, and specifically excludes treatment of 2 groups of related processes: dust transport away from source areas and its ultimate deposition; and evolution of surface properties, by the wind erosion process itself, by other weathering processes, or by management intervention. The results of the model are compared with data from a portable wind erosion tunnel, and with direct wind erosion measurements at paddock scale. By offering a synthesis of available physical knowledge of sand drift and dust entrainment, the model also indicates key areas of uncertainty.