Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility Reviewwhere S is a function of the fraction of residue or aggregate cover, biomass cover, and theheight of the plant canopy, residue, aggregates and other random soil roughness elements.TEAM uses a factor to adjust for field length effects on wind erosion. The field length factorwas developed by Gregory (1984) and built upon a relationship established by Chepil (1957)for field length effects on soil movement. The length factor accommodates abrasionprocesses in the calculation of the sediment transport rate from eroding fields, and issupplemented by an empirical abrasion factor that considers the field length, wind shearvelocity, and detachment rates of aggregated/crusted and loose soils. Two factors are used toaccount for the erodibility of soils in the solid (crusted) and loose conditions (Wilson, 1994).The erodibility of a crusted soil surface is computed by:bsE = fs( )(3.12)where E is the solid state erodibility (kgJ -1 ), ρ bs is the soil bulk density (kgm -3 ), τ s is the soilshear strength (Nm -2 ), and f(Θ) is a function of soil shear angle (dimensionless). For a loosesoil state the erodibility is computed by:El= N(3.13)bs2fu*twhere E l is the erodibility of a loose soil (kgJ -1 ), N is a calibration coefficient, ρ f is the airfluid density (1.23 kgm -3 ), and u *t is the threshold friction velocity (ms -1 ). The detachmentratio used to compute the field length factor is effectively a ratio of the solid and loose statesoil erodibilities.Testing TEAM wind erosion simulations against measurements of threshold friction velocityand sediment transport rates indicates that model performance is comparable with that of theWEPS and RWEQ models (Gregory and Darwish, 2001; Gregory et al., 2004). The modelwas found to perform well in comparison to measured erosion rates in bare and vegetatedsettings in both agricultural and industrial environments.79