The wind erosion process detaches soil particles from the land surface and transports them by wind. It occurs when forces exerted by wind overcome the gravitational and cohesive forces of soil particles on the surface of the ground.
Modes of transport of soil particles
Wind transports soil particles in different ways, depending on their size: creep, saltation, abrasion and attrition, and suspension.
The modes of transport of soil pariticles during wind erosion
Particles greater than 0.5mm in diameter are usually too heavy to be lifted by wind. Creep is when wind rolls these particles or they are moved along the surface by bombardment by other moving particles.
Saltation is the main process that suspends soil particles in the air - particles between 0.1 and 0.5mm in diameter are lifted by wind then fall back to the ground, so they hop or bounce across the surface.
Abrasion and attrition
Suspended particles cause abrasion of the soil surface when they fall back to the ground. They can also hit other particles and break into smaller particles, a process called attrition.
Small particles less than 0.1mm in diameter that have been ejected into the air by saltation 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 greater than 0.02mm will settle back to the ground within 100 kilometres of the erosion site, but finer particles can be carried long distances, as far as New Zealand.
Effects of drought on wind erosion
Wind erosion is a natural process that commonly occurs in deserts and on coastal sand dunes and beaches. During drought, it can also occur in agricultural regions where vegetation cover is reduced.
If the climate becomes drier or windier, then wind erosion is likely to increase. Climate change forecasts suggest that wind erosion will increase over the next 30 years due to more droughts and more variable climate. This will cause:
less rain, which will support less vegetation
lower soil moisture, which will decrease the ability of soil particles to bind together into larger heavier aggregates
increased wind speeds, which will result in more force exerted on the ground surface and more wind erosion (if the wind speed doubles, the erosion rate will increase eight times)
large losses of soil and nutrients
more large dust storms, which will impact soils and the community
poorer air quality, increased respiratory health risks, and temperature and rainfall changes due to atmospheric pollution (all off-site effects).
Protecting land from wind erosion
Land management activities such as land clearing, grazing and cropping can affect 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.
Adequate crop residue (shown left) prevents wind erosion that can occur when there is inadequate crop residue (shown right). Click images to enlarge.
Wind erosion can be protected against using:
- wind breaks, which protect against down-wind erosion for about ten times their height.
- about 50 per cent ground cover (such as crop residue), which provides control in paddocks
Relationship between ground cover and wind erosion. Arrow marks the level required to control erosion.
- small shrubs (like saltbush and bluebush), which can control wind erosion in rangelands, provided they are evenly spaced at about three times their height.
Cost of wind erosion
The cost of wind erosion to the economy, human health and the environment is high. The economic cost of dust storms has been discussed in the 2013 article 'Dust storms – what do they really cost?'. The dust storm of 23 September 2009 was estimated to cost the NSW economy nearly $300 million.
The cost of wind erosion includes the following:
- Impacts on human health: dust in the air can impact air quality and cause asthma and other health problems.
- Loss of agricultural production: wind erosion acts on the soil surface, so the more fertile top soil layers (where plant nutrients and organic matter are concentrated) are removed. This can affect grazing and cropping areas. Deposited wind eroded material can bury or sandblast pasture and crops, contaminate wool, overtop fences and deposit salt.
- Degradation of the environment: material eroded by the wind can choke creeks and deposit salt which can threaten rare and endangered plants and animals.
- Loss of property and aesthetic value.
- Loss of economic production associated with extra cleaning, disruption to commercial activities and transport.
Cost of 2009 dust storms
In August and September 2009, dust storms occurred regularly in western NSW and around Lake Eyre in South Australia. Dust was from drought-affected areas in western NSW and the eastern Lake Eyre Basin, and not from the Riverina as was reported at the time.
During the Sydney dust storm on 22 and 23 September 2009, about 75,000 tonnes of dust per hour off was lost off the NSW coast north of Sydney, with a total soil loss of 2.54 million tones for the singe dust storm.
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Page last updated: 18 February 2014