The role of water

The greater the rainfall, the less wind erosion. This is due to an increase in soil moisture which in turn promotes vegetation growth – two factors that decrease a soils susceptibility to wind erosion. Soil moisture increases the binding capacity of soil particles and encourages the growth of microorganisms which produce protective soil crusts.

Continental wind erosion frequency can be related to the ENSO cycle following highs and lows of rainfall patterning. Through geological history, high periods of dust activity correlate with the arid phases.

On a smaller scale, new research suggests that a little rain may in fact increase wind erosion rates. The disruption of soil particles from raindrop impact, without their redistribution (sealing effect) as with larger amounts of water, results in a soil with more loose particles. The loose particles may later be picked up by the wind.

Another role that water plays in wind erosion is sediment supply. Water erosion in the internally draining river systems of central Australia carries vast quantities of sediment downstream. The shallow floodplains of central Australia receive a supply of very fine sediments which, when dry, are often picked up by the wind and redistributed back across the continent.

 The role of plants

Plants protect the soil against wind. Vegetation slows the wind velocity close to the soil surface, increasing the boundary layer and increasing the difference between the surface velocities and the threshold velocity.

An important measurement is vegetation resistance to wind- a dense bush will produce a turbulent flow behind the bush, whilst a porous bush will allow wind through but slow its velocity. In the Mesquite (small prickly bush) country of southwest USA, the mesquite bushes are dense and regularly spaced. Despite the overall high vegetation cover, wind erosion occurs from the accelerated wind velocities between the bushes. Long rows of bare patches of earth will form between the bushes, making these areas unsuitable for new bushes to grow. This process has wind directions directing the vegetation patterning.

Monitoring vegetation can be done in the field (using quadrat or transect surveying methods) or by remote sensing (using satellite imagery). Remote sensing of vegetation cover is frequently used for a large number of natural resource management issues. Attempts have been made to relate these measures to frequency of dust events, but desert vegetation (where a lot of wind erosion occurs) is difficult to monitor due to the colours of desert plant species.