Omari Gates
Erosion in Australia is a pressing issue, threatening the environment, infrastructure, and the economy. It occurs in various forms, including coastal erosion, water erosion, and wind erosion, and is driven by both natural processes and human activities. Coastal erosion, predominantly caused by waves and currents, endangers iconic Australian beaches, such as Byron Bay and Apollo Bay, with an estimated 11,426 kilometres of coastline at risk. Water erosion, accelerated by agricultural practices and deforestation, leads to the loss of topsoil, reduced crop yields, and damaged infrastructure. Wind erosion, exemplified in Victoria, results from hot, dry winds lifting and carrying topsoil, causing dust storms and agricultural decline. Understanding the complexities of erosion and implementing effective management strategies are crucial for mitigating its impacts on Australia's diverse landscapes.
| Characteristics | Values |
|---|---|
| Type of erosion | Coastal erosion, water erosion, gully erosion, wind erosion, sheet and rill erosion |
| Causes | Waves, currents, storms, flooding, tsunamis, land subsidence, heavy rainfall, agriculture, mining, removal of vegetation, dredging, sand mining, river regulation, natural and human-induced climate change, walking over sand dunes, building of piers and marinas |
| Impact | Loss of topsoil, reduced crop yield, damaged infrastructure, weed dispersal, eutrophication, silting of dams and natural waterways, fence damage, reduced vehicle access, soil salinity, water salinity, increased flooding, destruction of natural habitats, economic hardship |
| Prevention | Engineering, chemical and vegetative measures, surface water earthworks, controlling surface water runoff, intercepting, diverting or slowing runoff, use of herbicides, fencing susceptible areas, increasing vegetation cover, applying gypsum, soil conservation measures, no-till methods, contour banks, filter strips, controlled traffic |
| Location | Victoria, Western Australia, New South Wales, Queensland, South Australia, Perth, Gold Coast, Murray-Darling Basin, Byron Bay, Sydney, Port Beach, Apollo Bay, Phillip Island |
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What You'll Learn
Coastal erosion
Australia's coastal zones are vulnerable to the full range of impacts from climate change and sea-level rise. With over 80% of the population living near the coast, this is likely to cause significant economic and social costs to Australia. Rising sea levels, combined with storm surges, are expected to cause accelerated erosion of many beaches around the Australian coastline.
The Twelve Apostles along the Great Ocean Road are a result of landscape change and coastal erosion over millennia. There were originally 12 limestone structures, and now only 8 remain. These are vulnerable to further erosion from waves. Around the Australian coast, nearly 39,000 buildings are located within 100 metres of 'soft' shorelines and are at risk from accelerated erosion due to sea-level rise and changing climate conditions.
To support Australia's ability to manage the impact of coastal erosion, Geoscience Australia's Community Safety team provides exposure information about buildings, demographics, community infrastructure, and agricultural commodities. They also offer around-the-clock access to data about people, property, and infrastructure potentially exposed to help inform decisions about risk. Geoscience Australia has also developed an online mapping portal that allows for the identification of areas of the Australian coast experiencing erosion. The Digital Earth Australia (DEA) Coastlines product is a free, publicly available dataset that measures annual shorelines and rates of coastal change along the entire Australian coastline from 1988 to the present.
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Water erosion
Certain landscapes are more susceptible to water erosion. Firebreaks, for instance, often act as laneways and follow fence lines, making them prone to causing fence damage and reducing vehicle access. Summer and early autumn storms with erosive rainfalls can result in severe water erosion on bare, loose soil.
To combat water erosion, a combination of engineering, chemical, and vegetative measures can be employed. Surface water earthworks, such as grade banks, can intercept, divert, or slow down runoff, reducing the risk of erosion. Additionally, adopting cropping and cultivation systems that improve soil structure and minimize bare soil exposure is essential. These strategies are more effective when combined with crop stubble retention, retained pasture cover, and managing vehicle and livestock disturbance.
In Victoria and South Australia, soil conservation measures have been successful in reducing water erosion. Between 1990 and 2010, Victoria experienced a decline in soil erosion due to the widespread adoption of soil conservation practices. Similarly, South Australia witnessed improved soil protection between 2003 and 2013, attributed to the increasing use of no-till methods.
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Gully erosion
In Western Australia, gully erosion can be expensive to fix and often requires revegetation to stabilise the area. One example is the formation of gullies from wash downslope along a fenceline and firebreak. This type of erosion can be managed through fencing susceptible areas, diverting water flow, increasing vegetation cover, and applying gypsum to improve soil structure.
The 2001 National Land and Water Resources Audit revealed alarming statistics about erosion in Australia. Almost 40% of the continent is affected by sheet and rill erosion, with 40% of the land facing medium erosion and 11% facing high levels. The Murray-Darling Basin, covering one-seventh of Australia's total land, is experiencing erosion across 40% of its surface area, leading to soil and water salinity issues.
To combat water erosion, various measures can be implemented, including engineering, chemical, and vegetative methods. Surface water earthworks, such as grade banks, can intercept, divert, or slow down runoff, reducing the impact of water erosion. Additionally, the use of cropping and cultivation systems can improve soil structure and minimise bare soil exposure. Implementing surface water drainage systems can also reduce the velocity and volume of water during peak flows, minimising soil loss.
In the case of gully erosion in the Great Barrier Reef catchments, millions of dollars are being invested in gully rehabilitation to reduce the delivery of excess fine sediment to the reef. This rehabilitation aims to prioritise active gullies for treatment and develop effective remediation methodologies.
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Tunnel erosion
Erosion is a natural process that occurs when water impacts the soil surface and displaces soil particles. While it is a natural process, human activities have accelerated it, especially through agriculture. Water erosion is a significant issue in Australia, with almost 40% of the continent affected by sheet and rill erosion. Western Australia, in particular, experiences water erosion in the southwest region, resulting in an estimated annual direct cost of $10 million to dryland farming.
The formation of tunnels in dispersive clays can lead to hazardous conditions. As the tunnels grow in size, they can cause the ground above to become unstable, posing risks to people, livestock, and farm vehicles. Additionally, exposed channels created by tunnel erosion can be dangerous to navigate due to undercutting. The vertical collapse of tunnels can result in sinkholes, which may only indicate a small part of a more extensive subsurface collapse.
To manage areas affected by tunnel erosion, several methods can be employed. Fencing off susceptible areas can help restrict access and reduce the risk to people and livestock. Diverting run-on water flow and increasing upslope vegetation cover can help reduce the amount of water entering the subsoil. Applying gypsum to soils susceptible to dispersion can also improve soil structure and reduce erosion.
It is important to note that while tunnel erosion is less common than other forms of water erosion in Western Australia, it can still have significant impacts on the landscape and pose hazards to people, livestock, and infrastructure. By implementing appropriate management strategies, the risks associated with tunnel erosion can be mitigated.
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Wind erosion
There are three processes of wind erosion: surface creep, saltation, and suspension. Suspension occurs to smaller particles that are less than 0.1 mm in diameter and can travel several meters, while saltation occurs to larger particles between 0.05 mm and 0.5 mm in diameter and can travel several kilometers. Dust storms, such as those that occur in Queensland and New South Wales, are typically suspension events as they can travel the longest distances.
The millennium drought, which began in 2000, and the mega-fires in Australia have highlighted the urgent need to revisit soil erosion dynamics. During the drought, two extreme dust storms hit eastern Australian cities on October 23, 2002, and September 22-24, 2009. The 2009 storm lifted 16 million tonnes of soil from central Australia to New South Wales, with some even reaching New Zealand. These dust storms negatively impacted air quality and human health, increasing public awareness of the environmental and economic impacts of wind erosion.
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Frequently asked questions
Coastal erosion is found all along the Australian coastline. Coastal erosion is driven by the action of waves and currents, and can also be caused by human activities such as the construction of coastal structures, dredging, sand mining, and river regulation.
Many iconic Australian beaches are affected by erosion, including Apollo Bay in Victoria, Port Beach in Perth, and Surfers Paradise on the Gold Coast.
Erosion in Australia has led to the loss of topsoil, reduced crop yields, damaged infrastructure, weed dispersal, eutrophication, and silting of dams and natural waterways. It has also contributed to increased flooding and economic hardship for farmers.
