Characterizing the sediment bed in terms of resistance to motion: Toward an improved model of saltation thresholds for aeolian transport

Models of aeolian transport thresholds generate a wide range of predictions, and error in threshold modeling leads to uncertainty in predicting aeolian events. This paper proposes a new characterization of the representative grain size for use in prediction of transport thresholds. This characterization is based on the distribution of resistance to motion in the sediment bed. The traditional grain size distribution uses a mean diameter to represent the sediment bed. However, the distribution of inertial forces resisting motion is not linearly proportional to the distribution of grain diameters, so that an arithmetic mean does not adequately represent the distribution of the resisting forces. A simple relation of shear stress to weight force is used to represent the threshold condition. Based on comparison with threshold observations drawn from the literature, the model provides reliable predictions of threshold stress and shear velocity for dry quartz grains over a wide range of grain sizes. Given that the dataset was drawn from studies employing a variety of experimental conditions and techniques, and that these studies spanned a range of nearly eight decades, the model is considered to provide a robust approximation of threshold conditions. (C) 2015 Elsevier B.V. All rights reserved.