Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controlssurface roughness and availability of loose erodible sediment (Zobeck, 1991). Overarchingcontrols on temporal changes in soil erodibility are factors that affect moisture content,aggregation and crusting, and are attributable to climate, land use and land managementpractices. These are described in detail in Section 2.2. The conceptual basis for soilerodibility to wind therefore differs from the third assumption noted by Bryan et al. (1989),with soil properties governing erodibility in practice being highly responsive toenvironmental change.Soil erodibility rankings like the WEGs are static. The position of a soil within a rankingsystem must be flexible to account for dynamic changes in soil properties. Static soilerodibility classifications like the WEGs are therefore indicative of long-term average,maximum or minimum erodibility conditions. They should not be used to infer the erodibilityof a particular soil unless its condition (in terms of crusting and aggregate size distribution)matches that of the same soil group in the WEG classification.Soil erodibility varies at multiple time-scales as a function of its controlling factors (Geeveset al., 2000). While soil texture is an underlying factor controlling soil erodibility (by itsinfluence on grain binding potential) and varies at very long time scales, soil moisture,surface crusting and aggregation may vary at time scales of minutes to years depending onclimate and management conditions. While variations in soil erodibility due to changes in soilsurface conditions were acknowledged in early research (e.g. Chepil, 1953), classificationslike the WEGs do not reflect the presence of an erodibility continuum.2.1.2 Assessing ErodibilityThere are three general approaches that may be used to assess erodibility. The first approachranks soil erodibility by measurement of soil physical properties that control the availabilityof loose erodible material. These properties include the aggregate size distribution and thepercentage of aggregates