Wind Erosion in Western Queensland Australia

Chapter 1 - Introductionevents yr -1 ), and down to coastal South Australia. This high-frequency region extends eastinto the Mallee-Riverina and Wimmera regions of western NSW, an area recording ~6.3 duststorm events yr -1 . The third region is located between Onslow and Carnarvon (8.1-5.6 eventsyr -1 ) on the Western Australian (WA) coast. Elevated dust-storm frequencies have beenobserved in southern WA (Carter, 1986); however, this region has received significantly lessattention than wind eroding regions in eastern Australia. The areas of high dust storm activityare located over red siliceous sand dunes and red earthy sands, texture-contrast soils, massivecalcareous earths, and cracking clay soils (Middleton, 1984; McTainsh and Leys, 1993).These soils are typically loose and mobile with poor aggregation, or in the case of thecracking clays, have a tendency to self-mulch and disaggregate.McTainsh and Pitblado (1987) examined the frequency of different types of dust eventsacross Australia. These included (following World Meteorological Organisation SYNOPCodes) dust storms (09), blowing dust (07), dust hazes (06) and dust whirls (08). While dustevents in general have been observed throughout much of Australia, dust-event frequenciesshow a trend of increasing with increasing aridity toward the centre of the continent. This isconsistent with global trends in dust source areas in Africa, the Middle East, China and NorthAmerica (Goudie and Midlleton, 2006). Blowing dust events occur less frequently and over asmaller area than dust storms, but in the same general source regions (McTainsh andPitblado, 1987). The spatial extent of dust hazes and whirls is further restricted within themajor regions frequently recording dust storms (Figure 1.1).Climatic indices to model spatial patterns in dust-storm frequencies across Australia weredeveloped by Burgess et al. (1989), McTainsh et al. (1990) and McTainsh et al. (1998). Themodels use soil moisture-erodibility (Em) relationships defined by Chepil (1965), winderosivity (Ew), and temporal variations between soil moisture, wind erosivity and winderosion (Et). The E-indices are based on Thornthwaite’s (1931) precipitation-evaporation (P-E) ratio that defines aridity on a broad scale. The Em index is able to explain 34% of thevariance in dust-storm frequencies across Australia (Burgess et al., 1989). Excess winderosion, defined where observed dust-storm frequencies are greater than those indicated bythe models, occurs around Carnarvon (WA), Alice Springs (NT) and in a belt running eastfrom Ceduna (SA) to Mildura (NSW) and up to Charleville in southwest Queensland.McTainsh et al. (1990) improved the performance of the Em-index by including a factor toaccount for mean annual wind run (Ew). They found the Ew index explains 66% of the6