Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controls[ C /( C + T )]( Q Q )R = /(2.28)envenvcvcbwhere C env is an emission coefficient for a vegetated surface, and is a function of plant stalkdiameter (mm), stalk height (m), and silhouette area (SAI) of stalks and stems per unit groundarea. T is an interception coefficient calculated as the ratio of SAI to plant height, Q cv is thesaltation discharge transport capacity of the vegetated surface, and Q cb is the measured soilloss from vegetated trays (determined by wind tunnel experimentation). While the modelaccounts for changes in SLR with wind speed, the input parameters to the model are noteasily measured, so the model does not work well outside the limits of the experimental datafrom which it was derived. Ash and Wasson (1983) and Wasson and Nanninga (1986)demonstrated that wind erosion could occur over surfaces with as much as 45% surfacecover. Their results showed how the relationship between vegetation cover and wind erosionvaries with wind speed (Figure 2.8). Similar results have been obtained by Hagen (1996),Hagen and Armbrust (1996), and Lancaster and Baas (1998).Figure 2.8 Graph illustrating the effect of Spinifex (Triodia spp.) grass cover on sand discharge for arange of wind velocities (after Wasson and Nanninga, 1986).Standing vegetation affects wind erosion by reducing u * close to the soil surface (Hagen,1996). This occurs as a portion of the total shear stress exerted by the wind becomes absorbedby standing non-erodible elements such as trees, shrubs and grasses. Wind energy is roughly57