Wind Erosion in Western Queensland Australia

Chapter 6 – Field Assessments and Model Validation6.2 Field Monitoring Approach6.2.1 Land Erodibility Assessment CriteriaA rule-set was established (Table 6.1) to provide criteria for the visual assessment of landsusceptibility to wind erosion, i.e. land erodibility. The criteria were employed to minimiseerror in the subjective nature of visually assessing land erodibility. Criteria used to assess thesusceptibility of the soil surface to wind erosion (soil erodibility) were adapted from theWind Erodibility Groups (Skidmore et al., 1994; Table 2.2). Soils were assigned anerodibility ranking based on their textural properties. Temporal variations in soil erodibilitywere assessed by disturbance levels (due to livestock trampling) and adjusting the rankingaccordingly. For example, a crusted loam soil would be considered non-erodible, whereas thesame soil in a heavily disturbed state would be assigned a high erodibility ranking.Table 6.1 Criteria used for the visual assessment of land susceptibility to wind erosion.Erodibility RankingIndicator High (3) Moderate (2) Low (1) Not Erodible (0)Soil Texture Sandy Loamy Clay -Surface ConditionHeavytramplingdisturbanceModeratetramplingdisturbanceLight tramplingdisturbanceCrustedGrass Cover 0 – 20 % 21 – 30 % 31 – 50 % > 50 %ErodibleNot ErodibleTree Cover 0 – 20 % > 20 %Stone Cover Sparse / None Present Dense (> 70 % cover)Rainfall No rain during survey or prior week Rain during surveyLand TypeDescriptorWoodland, Open Downs/Plains, River Channels, Claypan (playa), Sandplain,Dunes, Gibber (stony mantle)Criteria for assessing the influence of grass cover were adapted from the rule structureapplied by Webb et al. (2006) to model wind erosion hazard in Australia (after Wasson andNanninga, 1986; Leys, 1991a). Tree cover effects on land erodibility were considered by asimple threshold of 20% cover, over which the landscape was assigned a ranking of ‘noterodible’ (Marshall, 1972).159