Wind Erosion in Western Queensland Australia

Chapter 8 – Conclusions2. Spatial scaling issues were found to adversely affect both model performance and effortsto validate the model output using field assessments of land erodibility. This issue wasfound to be particularly relevant to the performance of AUSLEM in the Mulga Lands, tothe east of the study area. In this bioregion the distribution of tree cover is a dominantcontrol on land erodibility. Neither the model input data nor model frameworkaccommodated sub-grid scale variations in vegetation cover. This meant that modelpredictions of land erodibility were largely driven by the model tree cover threshold (of20%) and accuracy of the 30 x 30 m resolution foliage projective cover (FPC) data inrepresenting the distribution and cover of woody vegetation. Field observations suggestthat AUSLEM was unable to detect local variations in land erodibility in this bioregion.This became a significant problem when comparing field assessments of land erodibilityto AUSLEM output for model validation. Because neither the model nor the fieldassessments specifically accounted for vegetation distribution effects on erodibility, agood measure of model performance could not be obtained in the Mulga Lands. Furtherresearch is required to incorporate vegetation distribution effects into the model.3. The lack of quantitative estimates of land susceptibility to wind erosion affected efforts tovalidate AUSLEM. Model validation was therefore dependent on a comparison of timeseriestrends in model output with observational records of dust events. While thecomparison demonstrated that the model works well in the western portion of the studyregion, it did so because the dust event records at the meteorological stations in that areawere representative of local dust entrainment. The records at the western stationstherefore provided a good indicator of temporal changes in land erodibility around thestations. Poor agreement between the model output and dust event records at the easternstations was attributed to the fact that the dust events there did not provide a goodindicator of local conditions. Thus, model performance to the east of the study area couldnot reasonably be assessed using that methodology. While an approach was developed tocollect field assessments of land erodibility across the study area, application of the datain validating AUSLEM was affected by the availability of data that could be used as inputto the model at an appropriate spatial resolution for comparison with the fieldassessments. It was also affected by the fact that the field observations were made on acategorical basis and then compared to a continuous and non-linear range of model outputvalues. This research limitation can be addressed by: refining the field assessmentmethodology so that visual observations are recorded on a continuous scale; and making199