Wind Erosion in Western Queensland Australia

Chapter 7 – Land Erodibility Dynamics 1980-2006Results show a weak correlation between land erodibility and annual rainfall across the studyarea (Table 7.1). Importantly, land erodibility is responsive to multi-year (>2 years) rainfalldeficiencies (drought) and periods of above average rainfall. Similar responses have beenreported in dust source areas in the African Sahel and North America (e.g. Brooks andLegrand, 2000; Prospero and Lamb, 2003; Reheis, 2006). Significant increases in the areas ofland susceptible to wind erosion occur in drought years (Figures 7.5 and 7.6). The landscaperesponse to drought varied between bioregions and is dependent on antecedent rainfall andvegetation conditions, which generates the lag responses in land erodibility change (alsoPeters and Eve, 1995). The modelled increases in land erodibility with drought are consistentwith reports of increased wind erosion activity over the study area, e.g. McTainsh et al.(1989), and a global dependence of temporal variations in wind erosion on episodic droughts(Middleton, 1985; Goudie and Middleton, 1992; Gao et al., 2003).The spatial extent of drought in western Queensland is dependent on the rainfall relationshipwith ENSO (Crimp and Day, 2003). Temporal patterns in areas affected by drought are not,however, consistent and may vary considerably from year-to-year (McKeon et al., 2004). Thepoor correlation between modelled land erodibility and the SOI (Table 7.1) is a result of thisphenomenon. The El Niño/Southern Oscillation, represented in this study by the SOI, is afluctuation in the intensity and position of the Walker circulation (Troup, 1965). Sustainednegative SOI phases (El Niño) are associated with extended periods of warm sea-surfacetemperatures (SST) in the equatorial eastern Pacific Ocean, a weakening of the Walkercirculation and reduced convection over the Australian continent. Positive SOI phases (LaNiña) are associated with a strengthening of the Walker circulation and easterly trade windsand may result in enhanced convection and rainfall over parts of eastern Australia (Sturmanand Tapper, 2001). The association of peaks in land erodibility over the study area during ElNiño driven drought events suggests that despite the poor correlation ENSO plays animportant role in modulating land erodibility dynamics in western Queensland.The interaction of ENSO with the PDO adds complexity to understanding rainfall anddrought variability in western Queensland. Power et al. (1999) reported on the inter-decadalmodulation of ENSO and its effects on rainfall in Australia. Their results showed that warm(positive) and cool (negative) phases of the PDO may enhance or suppress positive andnegative SOI phases and the probability of eastern Australia receiving above or belowaverage rainfall. McKeon et al. (2004) reported that less than 10% of years (1890-1991) with184