Predicting Wind Erodibility of Locssial Soils in the Pacific Northwest by Particle Sizing

IVind ttiimel tests on silty textured loessial soils throtigbout the Cohimhia Plateau of eastern Wa.shiitg{on slate and northern central Oregon were used ro define soil erndibiltiy for wind erosion predictions. Aggregate and primary particle size distributions were determined hy common techniques and correlated wiih 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 tiseful results for discriminating among the wind tunnel erodibilify of the tested soils. A combination of standard wire-mesh and sonic sieving of dry aggregates from 30 ^ni to 2000 [ini proved most applicable for correlation to soil mass eroded during wind tunnel field trails. Separate correlations were made for sUty soils ihat are readily su.spendible 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.