Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controlswhere SLR is the soil loss ratio, F c is the percent soil cover by non-erodible elements, and αand β are regression coefficients describing the intercept and exponent respectively. Findlateret al. (1990) identified a limitation in Fryrear’s SLR, noting that as surface cover approaches0, the SLR approaches a value of 1.8. They developed a variant on the SLR with a maximumof 1, and presented a revised model of the form SLR = exp (-βFc) . The model performed well ina comparison using data from Fryrear (1985) and portable field wind tunnel experimentation.Leys (1991a) found a similar exponential relationship between cover and erosion rates(Figure 2.7), but reported further limitations with the SLR. The limitations are that: the modelnever falls to 0 no matter how high surface cover is, and secondly, the model gives the sameSLR for all wind velocities. Leys (1991a) then presented an approach relating soil flux (Q) tosurface cover using recurrence intervals for wind velocities to determine the probability ofwind erosion.Figure 2.7 Graph illustrating the effect of wheat stubble cover on sand discharge (after Leys, 1991a).Armbrust and Bilbro (1997) developed an approach to account for stem area, leaf area, andcanopy cover of growing crops on the SLR, transport capacity and u *t . They used a singleparameter expression for the SLR, with surface cover being replaced by a plant area index(PAI - a composite of stem and leaf area indices). As the SLR is a function of wind velocity, amodel was derived to determine the reduction in transport capacity (R) due to surface coverand as a function of wind speed:56