There has been some talk in the Australian media about land subsidence and sinkholes suddenly occurring overseas.
In June 2012 the Australian Water Commission published a CSG water management position paper which stated:
Potential risks to sustainable water management
• Extracting large volumes of low-quality water will impact on connected surface and groundwater systems, some of which may already be fully or over allocated, including the Great Artesian Basin and Murray-Darling Basin.
• Impacts on other water users and the environment may occur due to the dramatic depressurisation of the coal seam, including: - changes in pressures of adjacent aquifers with consequential changes in water availability - reductions in surface water flows in connected systems - land subsidence over large areas, affecting surface water systems, ecosystems, irrigation and grazing lands.
• Extracting large volumes of low-quality water will impact on connected surface and groundwater systems, some of which may already be fully or over allocated, including the Great Artesian Basin and Murray-Darling Basin.
• Impacts on other water users and the environment may occur due to the dramatic depressurisation of the coal seam, including: - changes in pressures of adjacent aquifers with consequential changes in water availability - reductions in surface water flows in connected systems - land subsidence over large areas, affecting surface water systems, ecosystems, irrigation and grazing lands.
Now this clearly identifies risk, but doesn’t give any idea of what land subsidence might look like for NSW property owners and residents unlucky enough to experience it.
Sinkholes range in size from square meters to square hectares in size.
They usually form when there is either a collapse of an underground cave, or mining/excessive groundwater flow creates unstable soil/bedrock conditions, or mining results in water pressure levels changes in a natural aquifer which cannot sustain the weight of rock and soil above it.
This 2011 sink hole in Gosford NSW was caused by a leaking underground sewer:
In 2012 this sinkhole appeared in a Sydney suburb:
Another small sinkhole which opened up at Ocean Shores NSW in 2013:
Yet another sinkhole in Newcastle NSW on a residential property which
sits atop old mine workings:
sits atop old mine workings:
One of the fourteen homes in one suburb damaged due to mine
subsidence in the Newcastle area last year:
subsidence in the Newcastle area last year:
House collapse due to mine subsidence in Newcastle NSW in 1953:
This is a very old natural sink hole in the mining town of Mt. Gambier
SA caused by cave collapse:
SA caused by cave collapse:
1925 to 1977 markers showing land subsidence due to over extraction
of groundwater in San Joaquin Valley, California USA
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