Wind erosion

Wind erosion is the process by which soil particles are detached from the land surface and transported by the wind. The cost of wind erosion is high, with environmental, health and economic impacts.

This page contains information on wind erosion processes, effects of drought and climate change, effects of land management practices, cost of wind erosion. Information on wind erosion monitoring can be found on the DustWatch page.

Wind erosion process

Wind erosion occurs when the forces exerted by the wind overcome the gravitational and cohesive forces of soil particles on the surface of the ground. The wind transports these particles in three ways, depending on their size. 

• Particles greater than 0.5 mm diameter are generally too heavy to be lifted by the wind, so they are rolled along the surface by wind drag or moved by bombardment by other moving particles. This mode of wind transport is called creep.
• Particles in the range 0.1-0.5 mm diameter are lifted by the wind, then fall back to the ground, so they move in a hopping or bouncing fashion. These particles cause abrasion of the soil surface and as they hit other particles they break into smaller particles, a process called attrition. This bouncing mode of wind transport is called saltation and is the main process forming the suspension fraction of soil particles in the air.
• Once small particles less than 0.1 mm in diameter have been ejected into the air by saltation they remain suspended as dust and are carried away from the erosion site by the wind. This mode of wind transport is called suspension. The majority of particles > 0.02 mm will settle back to the ground within 100 km of the erosion site but finer particles can be carried long distances, even as far as New Zealand.

Schematic diagram of the modes of transport of soil pariticles during wind erosion		Saltation of grains across a claypan

Effects of drought and climate change

Wind erosion is a natural process that commonly occurs in deserts and on coastal sand dunes and beaches. In times of drought it may also occur in agricultural regions where vegetation cover is reduced. However, levels of wind erosion can be increased by climate change and by some land management activities.

Suspended soil particles, or dust, being lifted from a paddock		Sydney dust storm, Central railway station, 1pm  23 September 2009

If the climate becomes drier or windier, then wind erosion will be likely to increase.

• With less rain there will be less vegetation and less soil moisture to bind the soil and promote biological activity which glues soil particles together into larger heavier aggregates.
• If wind speeds increase, more force will be exerted on the ground surface causing more wind erosion. If wind speed doubles, the erosion rate will increase eight times.

Climate change forecasts suggest that wind erosion will become worse over the next 30 years due to increased drought and more climate variability.

• On-site effects of wind erosion will be large losses of soil and nutrients.
• Occurrence of large dust storms will increase with major impacts on soils and the community.
• Off-site effects of wind erosion will include poorer air quality, increased respiratory health risks and temperature and rainfall changes due to the atmospheric pollution.

Effects of land management practices

Land management activities like land clearing, grazing and cropping can have a large effect on wind erosion. In general, land management practices that retain vegetation cover, such as trees, crop residue or pasture and involve minimal soil disturbance, tend to lower the potential for wind erosion.

General guidelines for protecting against wind erosion:

• Wind breaks provide down-wind erosion protection for about 10 times their height.
• About 50% ground cover (such as crop residue) is required in paddocks for wind erosion control.
• Small shrubs, like saltbush and bluebush, can control wind erosion in rangelands, provided they are evenly spaced at about three times their height.

Relationship between ground cover and wind erosion. Arrow marks the level required to control erosion		Adequate crop residue (shown left) prevents wind erosion that can occur when there is inadequate crop residue (shown right)		Cultivation of this pasture paddock has made it susceptible to wind erosion

Cost of wind erosion

The cost of wind erosion to the economy and to the environment is large: it impacts on the site from which soil is removed, the air in which it is transported and the sites at which it is deposited.

• Plant nutrients and organic matter are usually concentrated near the soil surface, making it more fertile than the soil beneath.  Wind erosion acts on the soil surface, so the more fertile soil layers are removed. Consequently, wind erosion is damaging to the soil itself, to the general environment and to agricultural productivity.
• Dust is the most visual aspect of wind erosion and dust also causes serious health issues. The 1999 CSIRO Costing Dust report (available from http://www.clw.csiro.au/publications/consultancy) estimated the health costs of dust to South Australia were up to $50m.
• Deposited wind eroded material can bury pasture and crops, choke creeks, overtop fences and deposit salt.

The cost of wind erosion includes:

• environmental degradation
• threat to rare and endangered plants and animals
• loss of production
• loss of property value
• loss of soil nutrients
• loss of grazing and cropping area
• sandblasting of crops
• contamination of wool with sand
• loss of aesthetic value
• reduction in air quality
• human health issues

Dust storms 22 and 23 September 2009

Dust storms occurred regularly in western NSW and around Lake Eyre in South Australia over August and September 2009. Dust was from drought-affected areas in Western NSW and the eastern Lake Eyre Basin. It is not from the Riverina as reported.

During the Sydney dust storm about 75,000 tonnes of dust per hour off was lost off the NSW coast north of Sydney
(source: DustWatch community-based monitoring project).