Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility ControlsThe wind erodibility index (Table 2.2) is a measure of the mass of sediment eroded from soilcontaining more than 60% dry aggregates (diameter >0.84 mm) relative to the soil containingother portions of aggregates under the same conditions. A similar classification wasdeveloped by Leys (1991b) for Australian soils in western New South Wales. The WEGs arefaithful to the definition of erodibility given by Houghton and Charman (1986).Two additional erodibility ranking systems have been proposed that are of interest here: the‘Lorikey’ and the Land Erodibility Index (LEI). These provide contrasting approaches forassessing and ranking the susceptibility of soil and land areas to wind erosion.Lorimer (1985) developed the ‘Lorikey’ to provide a method for assessing the susceptibilityof soils and land to wind erosion. The key extended early soil erodibility ranking systems(Marshall, 1973; Kimberlain et al., 1977) and the WEGs. These systems were combined withfactors quantifying wind strength, site exposure (topography) and the frequency of erodiblewinds, as well as soil surface condition, organic matter and texture. The Lorikey does nothave a measurable unit like the WEGs or the soil or field erodibility factors (Table 2.1). Likethe field erodibility index (K), the Lorikey allows for the assessment of land susceptibility towind erosion. However, the Lorikey does not include vegetation effects on wind erosion.Application of the Lorikey is therefore restricted to bare (cultivated) agricultural regions.McTainsh et al. (1999) developed a Land Erodibility Index (LEI). The LEI provides anindication of the relative susceptibility of land types (e.g. downs, dunes and playa) to winderosion, as well as temporal changes to these in response to climate variability. The LEI iscalculated as the dust flux (sediment flux at 0.5 to 2 m) divided by the cube of the mean windspeed above 6 ms -1 for the sampling period (monthly or annual). Unlike the soil erodibilityfactor, WEGs and the Lorikey, the LEI represents an historic account of wind erosionprocesses and is responsive to changes in soil surface condition, moisture, vegetation coverand windiness.2.1.1 Temporal Changes in Soil ErodibilitySoil erodibility is not constant but varies through time. Factors controlling soil erodibilityinclude texture, soil moisture and binding agents (both mineral and organic). Temporalvariations in soil erodibility are influenced by soil aggregation and crusting which affect the29