The silent danger below
24 September 2003
A potential danger may be lurking beneath the surface of backyards across the fast-growing northern suburbs of Perth. Geoscience Australia scientists are currently working with local authorities to raise awareness of this stealthy hazard which has implications for planning and development in the growing city.
Limestone cliffs form some of Australia's most spectacular coastline scenery. But the same cliffs can also be hazardous, as illustrated by the tragic Gracetown cliff collapse in 1996. And the danger is not isolated to coastal areas.
"People are often aware that limestone cliffs can be dangerous, but no one realizes that limestone in inland areas can also cause problems", Perth-based Geoscience Australia scientist Lisa Buckleton said.
When surface or ground water dissolves limestone, it forms distinctive features known as karst landscapes. These areas are characterized by sinkholes and caves which are potentially unstable. Karst landscapes occur around the western, southern and eastern margins of Australia.
"Knowing where these karst areas are is important in making land use decisions regarding roads, buildings and other structures. It can mean avoiding costly repairs and reducing the risk of injury", Ms Buckleton said.
A 'karst belt' lies five kilometres from the Perth coast and extends for approximately 25 kilometres in a north-west to south-east direction. The Wanneroo city area lies within this belt, and local government land planning procedures need to ensure that properties in the region are not put at risk from karst hazards.
Geoscience Australia scientists entered into dialogue last year with Phil Calley, Manager of Operations of the City of Wanneroo, about the potential risk from karst hazards, such as cave collapse.
The result of this is an information brochure produced by Geoscience Australia about karst hazards. Lex Bastian from the Western Australian Speleological Group also provided assistance during the research for the brochure.
The brochure has been distributed to national emergency managers. It will also be distributed to schools in the City of Wanneroo with the aim of increasing awareness of this potential danger.
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