Wind Erosion
Introduction
The dust that you normally see in the air after the soil has been trampled is the finer particles of the soil which normally contains most of the nutrients in the soil and this leads to a decline of soil fertility and may even affect a person's health as fine dust particles can pass through nose hair and end up in the lungs. The optimal level of land cover with vegetation is 50% and anything below this level is at risk of various erosion, including wind erosion.
Wind erosion is the removal of soil by wind and Australia is especially susceptible to this factor because of its naturally dry climate due to the geological stability resulting in very old soil, which is mineral deficient and fragile especially in Australia's extreme climate. This is made worse due to the fact that there is a lack of vegetation in most areas of Australia which significantly reduces the ability for soil to be held down during storms thus allowing more soil to be removed by the wind and this leads to land degradation and further degrading of the soil's ability to be resistant to the wind and to support vegetation that would aid the soil. The diagram on the right further illustrates the vast amount of area that is highly affected by wind erosion in Australia.
There are three processes of wind erosion: surface creep, saltation and suspension (see diagram below). These three processes describe different distances that airborne dust particles could cover with suspension being the longest and creeping being the shortest. Suspension normally occurs to smaller particles that are less than 0.1 mm in diameter and can only travel several meters, saltation occurs to particles between 0.05 mm-0.5 mm in diameter and can travels several kilometers while suspension occurs to particles between 0.5 mm and 2 mm and can travel thousands of kilometres. Dust storms such as ones that occur in Queensland - New South Wales (more in case study) are normally suspension as it can travel the longest distances. This is also how topsoil dirt from NSW can travel to Tasmania (more than 1380 km).
Wind erosion is the removal of soil by wind and Australia is especially susceptible to this factor because of its naturally dry climate due to the geological stability resulting in very old soil, which is mineral deficient and fragile especially in Australia's extreme climate. This is made worse due to the fact that there is a lack of vegetation in most areas of Australia which significantly reduces the ability for soil to be held down during storms thus allowing more soil to be removed by the wind and this leads to land degradation and further degrading of the soil's ability to be resistant to the wind and to support vegetation that would aid the soil. The diagram on the right further illustrates the vast amount of area that is highly affected by wind erosion in Australia.
There are three processes of wind erosion: surface creep, saltation and suspension (see diagram below). These three processes describe different distances that airborne dust particles could cover with suspension being the longest and creeping being the shortest. Suspension normally occurs to smaller particles that are less than 0.1 mm in diameter and can only travel several meters, saltation occurs to particles between 0.05 mm-0.5 mm in diameter and can travels several kilometers while suspension occurs to particles between 0.5 mm and 2 mm and can travel thousands of kilometres. Dust storms such as ones that occur in Queensland - New South Wales (more in case study) are normally suspension as it can travel the longest distances. This is also how topsoil dirt from NSW can travel to Tasmania (more than 1380 km).
Causes
Effects
There are many harmful affects resulting from excess wind erosion. Some telling factors are:
• bare soil • a rippled soil surface • exposed roots • exposure of subsoil at the surface • reduced plant growth • dust clouds (the image on the right shows a dust cloud) Wind erosion has the following impacts: • Soil fertility is reduced because of the loss of the plant nutrients (fine soil particles and organic matter) which reside in the topsoil. This reduces the soils ability to support productive pastures and sustain biodiversity. • Erosion at the base of bushes and plants can result in the plant being isolated and ground cover being thinned out. This then results in the roots of the plant being exposed, increasing the chance of it being eroded during heavy rain • The erosion of the light-textured topsoil can expose clay subsoils. These are normally found in smooth and bare areas, called clay-pans which can cover hundreds to thousands of hectares. They are difficult to regenerate due to the lack of topsoil and their often saline nature. The exposure of clay subsoils do not allow water to bypass this layer of soil thus more problems will occur relating to water erosion. • The build up of soil particles may bury fences and roads and other infrastructure. Rebuilding or excavating infrastructure may come at large costs to both councils and the private sector. • Sand grains transported by strong winds can damage vegetation in their path by sandblasting. The sand grains can also cause damage to infrastructure mostly through paint damage. The loss of vegetation will make wind erosion more often and stronger. The cost of both the maintenance of infrastructure and vegetation is quite expensive. • Air pollution caused by fine particles in suspension can affect people's health and cause other problems such as dust clouds, which decreases view range significantly and be a hazard to the health of other animals. |
|
Effective Solutions
Several treatments can minimise the wind erosion. Prevention is both more effective and more cost effective than cure, however not many farmers or grazers do this as it would reduce the net income. The problem is then left to the government or left, to be made worse. This is a major problem. However the more successful solutions and preventive measures are
|
|
Case Study
A major incident happened during a major drought considered the worst in 100 years on 22-24th of September 2009 in Australia when 16 million tonnes of soil was lifted from the middle of Australia to New South Wales and the remainder of the dust even reached New Zealand due to an intense low pressure system towards the west of Australia. Most of the soil was dumped in Darling Harbour and the Tasman Sea. This event shows that in just 2 days, 19 millions tonnes of soil can be lost due to wind erosion. Most of this soil was topsoil from vegetation lacking plains, as it was exposed to elements such as the wind. The dust storms was a health hazard, both directly and indirectly. The view range was diminished to extraordinary lows as the bottom right image shows, the Harbour Bridge only just being visible to the photographer.