Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility Reviewwhere SA is the sand content (%), Si is the silt content (%), CL is the clay content (%), OM isthe organic matter content (%), and CaCO 3 is the calcium carbonate content (%). The soilcrust factor (CF) is computed using the equation:CF1= (3.4)1+0.0066( CL) 2 + 0. 021( OM ) 2The model weather factor (WF) combines measures of wind erosivity and a wind erodibilityfactor based on soil water content. The weather data is simulated and draws on an historicalweather database (Fryrear et al., 1998). As for WEQ, the model K’ factor describes the soilridge roughness and COG (Equation 3.2) defines the percentage cover of dead, flat andstanding plant material. Both the K’ and COG factors can be either measured in situ, orderived from a series of empirical relationships (Merrill et al., 1999). Importantly, the factorsin RWEQ reflect current field conditions for particular events, rather than annual averageconditions (as for WEQ).RWEQ can be applied to predict soil loss from multiple individual fields. However, themodel inputs represent single value average conditions for the fields, and so the modelassumes spatial homogeneity in the soil management, surface crusting, and vegetation coverconditions. The implication of this is that the model cannot be applied to accurately simulatesoil loss in rangeland environments where field conditions are highly non-uniform(heterogeneous). The expressions used to compute the soil surface conditions are based onregression equations and data collected on soils in the United States (US). While RWEQ hasbeen applied successfully outside the US (Van Pelt et al., 2004), this application is still relianton experimental data to support model predictions of soil erodibility on soils different tothose in the US (Leys, 1999).3.2.3 Wind Erosion Prediction System (WEPS)The Wind Erosion Prediction System (WEPS) was developed to advance wind erosionprediction through process-based modelling. While WEQ and RWEQ rely on empiricalrelationships and field-measured inputs, WEPS was developed as a process based,continuous, daily time-step wind erosion model that simulates weather, field conditions,74