Wind Erosion in Western Queensland Australia

Chapter 6 – Field Assessments and Model ValidationThreshold criteria were applied for assessments of soil moisture and stone cover effects. Landerodibility was assigned a value of 0 (not erodible) where rain was actively falling, or hadfallen in the week prior to survey. For all other areas surface soil moisture content wasconsidered negligible and land erodibility a function of soil and vegetation conditions. Stonecover effects were considered by an on-off criteria: where stone cover was dense (> 70 %) aranking of ‘not erodible’ was applied (Gillette et al., 1980). The final land erodibility rankingwas based on an average of the component observation ranks on a four-class scale: high;moderate; low; and not erodible.6.2.2 Sampling MethodologyThe sampling strategy used was adapted from Hassett et al. (2000) and involved applying theabove criteria to record visual assessments of land erodibility. Assessments were made from amoving vehicle that was driven through the study area. Computerised Information GatheringSystem (CIGS) software (Boyce Industries, Brisbane, Australia) was used for data recording.CIGS provides an interface that links observations recorded via computer function keys tolatitude and longitude coordinates from a global positioning system (GPS). The software wasrun from a laptop, while a GPS mounted on the vehicle dashboard provided positionalinformation that was read directly into the CIGS logging interface.Definition files compiled using a text editor were used to assign a unique observation anddata entry space to the laptop function keys. Function keys were used to record assessmentsby the criteria in Table 6.1, and additional comments (i.e. actively blowing dust). The CIGSinterface allows for raster and vector format data to be displayed as a moving backgroundwith the observer position and logged data points displayed as an overlay. Soil texture data(Australian Natural Resources Atlas, 2007) was used as a background to facilitate evaluationsof soil erodibility.Visual observations were restricted to areas ~100 x 100 m in size. This window was selectedto ensure that assessments were made over a regulated area, and would not be significantlyinfluenced by changes in topography or vegetation density. Vehicle speed for data recordingaveraged 80 – 100 kmh -1 . Assessments were made approximately every 60 seconds and morefrequently when close to boundaries between land types. Each entry was assigned a date/time160