Wind Erosion in Western Queensland Australia

Chapter 5 – Land Erodibility Model DevelopmentThe approach for model development was to select then integrate empirical functions derivedunder standard measurement conditions (i.e. wind tunnel dimensions, wind speeds, etc.) thatcapture the relationships between wind erosion controls and the physical nature of the landerodibility continuum. That is, the model was designed to assess the range of susceptibility towind erosion that a land area may experience based on variability in soil erodibility andsurface roughness. Land erodibility was considered to exist on a dimensionless scale as theaim of this research was to produce a model to predict susceptibility to wind erosion, and notto quantify erosion rates or soil loss. The exact values of output erodibility predictions couldbe of any value so long as the position of a land area in the ranking is correct relative to otherareas for its given input conditions. AUSLEM ranks land erodibility on a continuous scalefrom 0 (not erodible) to 1 (high erodibility). The integration of factors controlling landerodibility (E r ) is through a multiplicative approach of the form:( tx) E ( gc) E ( w) E ( tc) E ( rk)E = E(5.1)r tx gc w tc rkwhere E gc (gc) and E w (w) define the effects of grass cover and soil water content on landerodibility. E tc (tc) and E rk (rk) account for the effects of large roughness elements (tree cover)and surface armouring over dense stony pavements found in the study area (rock cover).E tx (tx) defines the effects of soil texture on land erodibility. The model was composed usingthe ArcGIS 9.0 (ESRI) model building interface, and is run from the system command lineusing a batch file listing model parameter inputs.The revised AUSLEM framework differs significantly to that of the original model. Whilethe original model also had a 5 x 5 km spatial resolution, the revised model can be run on adaily time-step. This means that the model is now sensitive to daily rainfall events andresulting changes in soil moisture. This improved sensitivity is important for assessinglandscape responses to climate variability and land management conditions, and opens thepathway for integrating a dynamic soil erodibility scheme into the framework. The removalof the soil textural rule-sets from the model, and the addition of empirical grass cover and soilmoisture schemes allow the model to make more realistic assessments of land erodibilitydynamics through the continuum. AUSLEM no longer has any bias toward particular soiltypes. Rather, the model now accounts for the fact that both soil and land erodibility aretemporally dynamic conditions. Two parameters added to the revised model, to account for137