Predicting wind erodibility of loessial soils in the pacific northwest by particle sizing

Wind tunnel tests on silty textured loessial soils throughout the Columbia Plateau of eastern Washington state and northern central Oregon were used to define soil erodibiltiy for wind erosion predictions. Aggregate and primary particle size distributions were determined by common techniques and correlated with the wind tunnel erosion values. Dry aerodynamic particle sizing by a laser method was not useful due to disaggregation caused by the method, although it verified the upper size of sieving cuts. Neither wet dispersed nor aerodynamic techniques provided useful results for discriminating among the wind tunnel erodibility of the tested soils. A combination of standard wire-mesh and sonic sieving of dry aggregates from 30 μm to 2000 μm proved most applicable for correlation to soil mass eroded during wind tunnel field trails. Separate correlations were made for silty soils that are readily suspendible and sandy soils that are largely moved by saltation. Application of these correlations to wind erosion predictions will rely on developing additional relationships with the natural wind erodibility for these same soil classes.