Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility ControlsSoil erodibility is the susceptibility of a soil to mobilisation by wind. It is controlled by theavailability of loose erodible material (< 0.84 mm) on the soil surface as determined byaggregation (aggregate size distribution and aggregate stability), surface crusting and soilmoisture content. Factors controlling soil erodibility are soil texture (particle sizedistribution), moisture content, chemistry, organic/biological content, climate variability andland management. The physical characteristics of the soil erodibility continuum are describedin detail in Chapter 4.Land erodibility is the susceptibility of a land area to erosion by wind. Land erodibility is afunction of soil erodibility with the added effects of non-erodible surface roughness elements(rocks, vegetation, landforms). The effect of non-erodible elements like vegetation is througha partitioning of wind shear between roughness elements and the soil substrate resulting in anincrease in roughness length and potential decrease in wind erosivity at the soil surface.Physically, the effect of non-erodible elements on wind erosivity can be described by anincrease in the threshold friction velocity. Factors controlling land erodibility include thoseaffecting soil erodibility, land type characteristics (vegetation and geomorphology), climateand management. Where non-erodible roughness elements are absent, land erodibility iscontrolled by soil erodibility.The factors controlling soil and land erodibility operate at a range of spatial and temporalscales. This means that soil and land erodibility are spatio-temporally dynamic. Figure 2.10illustrates the spatial and temporal scales over which controls on land susceptibility to winderosion operate. While early classifications ranked soil erodibility using temporally staticscaling systems, modern studies must consider the physical manifestation of erodibility as itexists within a continuum (Leys et al., 1996; Geeves et al., 2000).Overarching controls on the susceptibility of land to wind erosion are climate, followed bysoil and vegetation properties and land management. A perquisite for wind erosion is anabsence of moisture. With this dryness comes low vegetation cover and a reduced capacityfor inter-particle cohesion. Factors controlling this lack of moisture include precipitationquantities and frequency, solar radiation, potential evaporation and wind speeds. Land useand land management affect wind erosion largely by controlling vegetation type and cover,and the soil surface properties.63