Susceptibility to wind erosion

Wind erosion is the movement of soil particles by wind. It occurs when the lift forces of the wind exceed the gravity and cohesion of the soil grains at the surface.

Susceptibility of land to wind erosion is determined by taking into account the inherent features of the soil, the climate and position in landscape. The erodibility of the topsoil is a major factor, but structure, texture, stoniness and organic matter are all significant. Land use and management may have a major influence on the degree of deterioration, particularly if dry soils are exposed when erosive winds are likely to occur. Wind erosion is likely to reduce the organic matter and nutrients available in the topsoil, while the reduction in topsoil depth also leads to reduced water infiltration causing increased runoff and a fall in productivity.

The loose sandy topsoils on granitic parent materials are highly susceptible, while the open plains with fine sandy loam topsoils, and the lower slopes of the drier granitic areas have moderate susceptibilities.

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The land characteristics and management factors involved in wind erosion are described in Table 8.

Table 8 Land characteristics and management factors involved in wind erosion

Processes	Land features affecting processes	Factors affected by land characteristics	Management factors that modify land characteristics
Wind erosion occurs when the force due to wind is sufficient to overcome the cohesion and weight of the soil particles and to allow their movement	Vegetation structure, percent surface cover (including litter) leaf area, rooting depth and perenniality	Exposure of surface soil Depth of zero velocity layer Transpiration and hence soil moisture content and particle cohesion	All aspects of the vegetation are affected by selection of species and control of biomass by practices such as grazing, trampling, harvesting, burning, cultivating, clearing, trafficking, fertilising
Processes involved are:	Climate rainfall/evapotranspiration regime wind strength wind direction	Soil moisture content and hence particle cohesion Detachment and transport Site exposure
detachment by abrasion and suction	Geology perviousness of rock or unconsolidated sediments	Soil moisture content and hence particle cohesion
transport by creep, saltation and suspension	Topography microrelief slope degree and position in landscape	Topography microrelief slope degree and position in landscape	Retention or construction of wind- breaks, cloddy cultivation and ridging affect microrelief
deposition by entrapment and reduced wind velocity	Soil percent stone cover size/weight of surface articles/aggregates aggregate stability (influenced by factors such as presence ofcarbonates, iron oxides and organic matter, clay mineralogy and biological activity) profile permeability, depth and water-holding capacity size/weight of surface	Surface wind strength Detachment and transport Detachment Soil moisture content and hence particle cohesion and weight or particles/aggregates	Soil disturbances such as trampling cultivating affect aggregate stability Any practices affecting biomass alter the organic matter content of the topsoil

Source: Aldrick, et. al. (1988)

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