Wind Erosion in Western Queensland Australia

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Chapter 2 – Land Erodibility ControlsErodibility • Susceptibility of a soil to detachment and transportation by anerosive agent.• A composite expression of soil properties that affect the mechanical,chemical and physical properties of a soil. Is independent oftopography, land use, rainfall intensity and plant cover, but may bechanged by management.Erosion Hazard • Susceptibility of a parcel of land to erosion.• Dependent on a combination of climate, landform, soil, land use andmanagement factors.Erosion Risk • Intrinsic susceptibility of a parcel of land to erosion.• Dependent on climate, landforms and soil factors, but independent ofland management.Erodibility and erosion hazard/risk work opposite to “erosivity”. Erosivity is the potential orcapacity of the wind to mobilize particles on the soil surface (Lal and Elliot, 1994).Susceptibility rankings are based on the premise that a location having a high erodibility ismore susceptible to erosion than a location with low erodibility, and that a highly erosivewind has more energy than a wind with low erosivity. Conceptually, erodibility isindependent of wind erosivity. However, if erodibility is to be measured to develop a rankingsystem, wind erosivity must be considered. This necessity is reflected in even the earlieststudies of wind erodibility. These studies applied wind tunnel experimentation and fieldmonitoring to determine the susceptibility of soils to wind erosion in cultivated fields.Chepil (1953) used constant wind erosivity conditions to determine soil and wind tunnelerodibility factors for the Wind Erosion Equation (WEQ). More recent studies have definederodibility rankings under a range of wind erosivities. Studies in the late 1950s to 1960sprovided a range of approaches for developing erodibility factors (e.g. Chepil and Woodruff,1963; Woodruff and Siddoway, 1965). The factors can be characterised by differences in thespatial scales at which they were derived (Table 2.1).26
Chapter 2 – Land Erodibility ControlsTable 2.1 Summary of selected erodibility factors used in the Wind Erosion Equation (WEQ) model.Erodibility Index Definition Spatial Scale Time Scale Measurement ReferenceSoil Erodibility (I) • Potential annual wind erosion for a given soil under agiven set of field conditionsPlot andFieldMinutes toMonthsWind TunnelDust Traps• Expressed as the average annual soil loss in tons peracre per year for a field that is isolated, unsheltered,bare, smooth, level, loose, non-crusted, and at alocation where the climatic factor (C) for the WEQ is100Knoll Erodibility (Is) • Accounts for the increased wind erosion potential ontopographic features (i.e. short slopes, knolls)• Varies for slopes with gradient > 3% and < 150 m long• An adjustment to I given the increase in wind velocityon the windward slopeWind TunnelErodibility (i)• Index of relative erodibility under wind tunnel withconstant conditions of friction velocity of 0.61 ms-1for five minutes over soil in trays with dimensions 5 ftlong and 8 inches wide• Expressed in tons per acre• Due to fetch and tray length restrictions in wind tunnel,i does not account for abrasion experienced under fieldconditionsField Erodibility (E) • Determined by application of the Wind ErosionEquation to determine potential soil loss in tons peracre per year• Accounts for soil (I) and knoll (Is) erodibility, localwind erosion climatic factor, soil ridge roughness, fieldlength and vegetation cover.FieldMinutes toMonthsFieldChepil and Woodruff(1963)Woodruff and Siddoway(1965)Woodruff and Siddoway(1965)Plot Minutes Wind Tunnel Chepil (1953)Field toRegionAnnual Modelled Woodruff and Siddoway(1965)27
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Beadle, N.C.W., 1945. Dust storms.
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Bryan, R.B., Govers, G., Poesen, J.
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Chepil, W.S., 1965. Transport of so
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Fryrear, D.W., Sutherland, P.L., Da
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Gregory, J.M., 1984. Prediction of
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Hugenholtz, C.H., Wolfe, S.A., 2005
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Littleboy, M., McKeon, G.M., 1997.
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Marshall, J.K., 1973. Drought, land
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Assessment Report of the Intergover
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Penner, J.E., et al. , 2001. Climat
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Rickert, K.G., McKeon, G.M., 1982.
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Wind Erosion in Western Queensland Australia

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