Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility ReviewWEELS has a process-based system that simulates wind erosion when u * exceeds u *t . Fourmodules are combined to compute u *t . The modules account for soil moisture, soil erodibility,soil roughness, and land use effects on the static threshold. Soil erodibility is calculated as afunction of soil properties including soil grain size distribution and soil type. Landmanagement conditions such as cultivation methods, crop type, crop rotations and land usescenarios are then used to adjust the soil erodibility, soil roughness and land use factors(Böhner et al., 2003).WEELS computes soil erodibility then independently accounts for soil moisture andvegetation cover factors by integrating these into the wind erosivity component of the model.Soil erodibility is quantified using a dimensionless factor K which expresses the intrinsicsusceptibility of a dry, freshly cultivated sandy soil to erosion. Values for K are computed asa function of the mean weighted diameter of the texture (by particle size distribution), organicmatter content and the proportion of aggregates > 0.63 mm:( MWD) 0.04( DA)log K = 1.24 4.21%(3.18)where MWD is the soil particle mean weighted diameter (mm), and %DA is the weightpercentage of aggregates > 0.63 mm (%) calculated as:(%Silt % Clay) + % DA = 2.42+ 8.6[ log( % OM )]+ 44.5 (3.19) % Sand where %DA is the aggregate portion > 0.63 mm (%), %OM is the weight percent soil organicmatter, and %Silt, %Clay, %Sand are the soil silt, clay and sand fractions (%). BothEquations 3.18 and 3.19 are regression equations derived from field experimentation inGermany (Böhner et al., 2003). Field measurements of %DA can also be used as input to themodel. Soil erodibility increases as K increases; however, K is considered static in WEELSand does not vary in response to changes in climate and management conditions. Vegetationeffects on u *t are considered by a logarithmic adjustment to u *t . The WEELS soil moisturemodule relies on a simple soil water budget that operates for sandy soils, so modelapplication is currently limited to sandy soils.82