Wind Erosion in Western Queensland Australia

Chapter 5 – Land Erodibility Model DevelopmentA pattern was found in the years in which model output trends went against those of dusteventfrequencies. For example, an increase in dust events was linked to a decrease in landerodibility. This occurred at three and then four stations in 1981 and 1982, at three stations inboth 1986 and 1987, and at five stations in 1990. The poor synchronisation of trends in theseyears was found to occur across each of the spatial scales from 25 to 150 km, and resulted inthe weak correlations at Quilpie, Thargomindah and Birdsville (Table 5.2). Thesynchronisation of trajectories in other years was found to be consistently good, except atLongreach where the trends did not match in any years.5.6 Discussion5.6.1 Model PerformanceCross-correlation results (Table 5.2) show that AUSLEM performs well at half of the stationsused for validation. The correlations between model output and dust-event frequencies werefound to vary with scale at all of the stations except Longreach, at which there was no matchbetween modelled land erodibility and dust-event frequencies. The differences in correlationswith scale indicate that either: 1) the dust source areas responsible for the observed dustevents are located within different areas and at different distances from the stations; 2) thatAUSLEM performs best at a particular scale depending on the land type characteristicsaround a station, or; 3) a combination of these factors is responsible.Figure 5.5a indicates that model output predictions can display similar temporal trends acrossspatial scales. Consistent model performance across scales (i.e. Urandangie) indicates thatgrass cover and soil moisture conditions may be uniform around the station, and/or that thedust source areas were widespread. Variations in the trajectories at particular scales areindicative of changes in land erodibility at a certain distance from a station. An increase inmean output values at larger scales, for example, suggests an increase in land erodibilityfurther away from a station. By comparison, lower land erodibility values such as aroundWindorah can be attributed to high vegetation cover on the Coopers’ Creek channels close tothe town. The strengthening of correlations between model output and dust-event frequenciesat Charleville and Quilpie can be explained by local tree clearing (Charleville) and the152