Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility Review0.8 Z 0 10 f ( )effZ0, z0s= 1ln / ln 0.35(3.27) z0s z0s where z 0 is the aerodynamic roughness length of the overall surface (cm), and z 0s is theaerodynamic roughness length of the erodible part of the surface (cm). The followingexpression is then used for the computation of u *t :u* t( D Z , z )u( D )* t pp, 0 0s= (3.28)feff( Z0,z0s)where u *t is a function of particle or aggregate size, total surface roughness length (includingvegetation), and soil surface roughness length. Soil moisture effects on u *t were notaccounted for in early versions of the model, but were included by Laurent et al. (2006) basedon the work of Fécan et al. (1999). Further, the model does not consider the effects of surfacecrusting and does not consider temporal variations in soil aggregation. All soils are thereforeconsidered loose and erodible if u * > u *t with field measurements of soil aggregation beingused to define soil particle size distributions for non-sandy soils. As values of u *t are assignedto particle size groups, the contributions of size groups to modelled dust emissions areproportional to the surface area covered by the groups.Qualitative validation of the DPM was presented by verification of the model functionsduring model development (Marticorena and Bergametti, 1995). The drag partitioningscheme was validated by comparison with stress partition measurements for roughnesslengths presented by Marshall (1971). Further tests of the model were conducted byapplication in Africa, the Middle-East and China (Marticorena et al., 1997; Alfaro andGomes, 2001; Lasserre et al., 2005). For these applications region specific soil texturaldatabases were used to determine dust source erodibilities, and roughness elements wereconsidered static and assigned from vegetation cover maps. Simulated dust emissions fromthe DPM have been compared with satellite imagery of dust events using the Infra-redDifference Dust Index (Brooks and Legrand, 2000), field records of dust entrainment, anddust observations averaged across regions (Marticorena et al., 1997).88