Erosion & sediment

Erosion

Erosion is a gradual process of deterioration where soil and rock wear away and is moved by natural forces like water and wind.

While erosion is a natural process, some land uses and poor catchment management practices can accelerate this process and throw landscapes and ecosystems out of balance.

All soils can suffer erosion, but some are more vulnerable than others.

The impacts of erosion are widespread and affect:

• Agriculture: Soil erosion removes the most productive soil layer which our food and fibres are grown in. Loss of this top soil results in a decrease in productivity of farmlands and higher production costs. It also affects the ability of the soil to store water and nutrients, increasing runoff and impacting crops growth and survival. When the top layer is gone, erosion can cause the formation of gullies that then make cultivation impossible.
• Waterways (freshwater and marine): The eroded soil particles enter the waterways polluting them and causing damage to habitat and declines in fish and other wildlife. An increase in sediment can also cause changes in hydrology (the way the water flows). The shape of river channels and estuaries change over time which can result in changes in the water flow speed and might decrease flood mitigation and resilience and cause the disappearance of refuge habitat.
• Coastal habitat: Shoreline erosion from sea level rise, storm surges and flooding, made worse by human activity, is shrinking coastal habitat including beaches, dunes and sand cliffs.
• Infrastructure: In South East Queensland, many of our soils are rich in sodium. This makes them more vulnerable to erosion, which can affect the construction of infrastructure, including dams, roads and tracks, urban developments, mining, and other activities.

Sediment

Sediment is made up of particles of soil, rock and other materials that have been worn away and transported by erosion. When sediment enters our waterways, it causes a range of environmental, social and economic impacts:

• Sediment can smother aquatic ecosystems, causing damage to habitat and declines in fish and other wildlife. Particles can block fish gills and cover their eggs. Suspended sediment reduces sunlight penetration, impacting the growth and survival of aquatic plants.
• Sediment carries other harmful pollutants with it, including nutrients, pesticides, heavy metals and synthetic ‘forever chemicals’, which can create toxic conditions for humans and aquatic life.
• Sediment can fill riverine pools, reducing critical refuge habitat for freshwater fish.
• Large accumulations of sediment can cause upstream flooding or divert flows into adjacent streambanks or land, causing further erosion.
• It can bring with it a range of different nutrients, which when introduced into the water ecosystem can alter the state of waterbody which can lead to the potential loss of water wildlife and species.
• The silt particles cause siltation of drinking water storages and watercourses, which needs to be filtered out. This increases the cost and energy of water treatment.
• Sediment can make flooding worse by clogging stormwater drains and pipes.
• Sediment causes creeks and rivers to become muddy, reducing visual amenity and opportunities for recreation.

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