Wind Erosion in Western Queensland Australia
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Wind Erosion in Western Queensland Australia

Modelling Land Susceptibility to Wind Erosion in Western ... - Ninti One Modelling Land Susceptibility to Wind Erosion in Western ... - Ninti One

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Chapter 1 - IntroductionDowns. Wind erosion is infrequently observed outside this zone due to higher annual rainfalland vegetation cover, so that area is not considered in this study.There is a seasonal pattern in wind speeds across the study area. The highest wind speeds areassociated with southerly to south-easterly air flow (BoM, 2008). This flow is largely drivenby the movement of a baric ridge across central Australia during the winter months and anticyclonicflow around the high pressure system. Dust entrainment is associated with thepassage of cold fronts and trough lines across the study area (McGowan et al., 2000). Thefrontal systems originate in the Southern Ocean to the south-southwest of the Australiancontinent and travel north over the study area through the cols that develop betweensubsequent eastward tracking anticyclones. This synoptic setup generates strong pre-frontalnortherly winds through central Australia. Behind the fronts and/or trough lines, anticyclonicridging may generate moderate to strong south to south-easterly winds over the study areawhich are also responsible for dust entrainment (Sturman and Tapper, 2001).Rainfall seasonality varies from north to south across the study area (Figure 1.8). Thenorthern regions are influenced by the Australian Summer Monsoon, thunderstorm activityand the incursion of rainfall depressions from the east coast during the summer months. Thesouthern regions of the study area have a less pronounced summer rainfall peak and asecondary peak during winter. However, winter is generally the driest time of the year acrossthe study area.At inter-annual time scales rainfall variability across the study area is associated with the ElNiño/Southern Oscillation (ENSO) (Whetton, 1997). Pittock (1975) reported a positivecorrelation (r 2 = 0.4) between rainfall and the Southern Oscillation Index (SOI), an indicatorof the intensity of positive (La Niña) and negative (El Niño) ENSO phases, and rainfall ineastern Australia. The correlation between rainfall and the SOI varies seasonally, and isinfluenced by phase interactions of ENSO (3-7 year cycle) with the Pacific (inter-) DecadalOscillation (PDO, a 15-30 year cycle) (Crimp and Day, 2003). Consequently, episodes ofpasture degradation and recovery in the study area are linked to variations in Australianrainfall driven by ENSO-PDO interactions (McKeon et al., 2004).Land use in the study area is dominated by pastoral activity with sheep and cattle grazing ofrangelands. Sheep grazing is dominant to the east the Mitchell Grass Downs and Mulga22

Chapter 1 - IntroductionLands. Cattle are typically grazed in the drier western Mulga Lands, Channel Country,Mitchell Grass Downs and Simpson-Strzelecki Desert bioregions. Property sizes increasefrom east to west across the study area, consistent with increasing aridity and decreasingstocking rates.1.7 Thesis StructureThe thesis contains six chapters which address the research objectives. These include tworeview chapters followed by four chapters presenting research into model development,validation and application. This is followed by a synthesis of the research outcomes. Figure1.9 is a flow chart outlining the structure of the thesis and links the thesis chapters to theresearch objectives.Figure 1.9 Flow chart of the thesis structure, linking the thesis chapters to the research objectives.23

Chapter 1 - IntroductionLands. Cattle are typically grazed <strong>in</strong> the drier western Mulga Lands, Channel Country,Mitchell Grass Downs and Simpson-Strzelecki Desert bioregions. Property sizes <strong>in</strong>creasefrom east to west across the study area, consistent with <strong>in</strong>creas<strong>in</strong>g aridity and decreas<strong>in</strong>gstock<strong>in</strong>g rates.1.7 Thesis StructureThe thesis conta<strong>in</strong>s six chapters which address the research objectives. These <strong>in</strong>clude tworeview chapters followed by four chapters present<strong>in</strong>g research <strong>in</strong>to model development,validation and application. This is followed by a synthesis of the research outcomes. Figure1.9 is a flow chart outl<strong>in</strong><strong>in</strong>g the structure of the thesis and l<strong>in</strong>ks the thesis chapters to theresearch objectives.Figure 1.9 Flow chart of the thesis structure, l<strong>in</strong>k<strong>in</strong>g the thesis chapters to the research objectives.23

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