Where do Landslides occur?
Landslides occur regularly in a variety of landscapes across every Australian State and Territory. These landscapes are commonly characterised by cliffs, steep slopes of colluvium deposits or gentle slopes of unstable geology and slopes which have been subjected to periods of prolonged or intense rainfall.
In addition, landslide prone areas can include locations which have previous evidence of landslide activity. This evidence can be obvious from a fresh scar in the landscape or difficult to identify if the slide has been covered by vegetation or property development.
Other landslide prone areas commonly include slopes made up of low strength, sensitive, collapsible weathered or disjointed material with internal and external weaknesses. Landscapes which also are more prone to landslides are those where there has been removal of vegetation, constant seepage or erosion of slope material by ocean waves and rivers or creeks.
Examples of areas in Australia which are known to be landslide prone include:
- Coastal cliffs
- the Great Dividing Range along the east coast
- the Strzelecki and Otway Ranges in southern Victoria
- the Mt Lofty Ranges near Adelaide in South Australia
- south-east Queensland
- the Mt Wellington, Tamar Valley and north-west coast of Tasmania
- the New South Wales and Victorian Alpine regions.
Examples of more localised areas include:
- The Illawarra Escarpment near Wollongong in New South Wales
- Sydney's northern beaches and the city's hinterland
- the Lake Macquarie and Newcastle suburban areas
- the coastal hinterland of New South Wales
- regions around Townsville, Cairns and Mt Tambourine in Queensland.
Potential landslide sites reveal themselves in several ways including:
- Saturated ground or seeps in areas which are not typically wet
- new cracks and scarps or unusual bulges in the ground, roads or pavements
- movement of ancillary structures such as decks and patios in relation to a house
- sticking doors and windows
- tilting or cracking of concrete floors and foundations
- broken water lines and other underground utilities
- leaning telephone poles, trees, retaining walls or fences
- offset fence lines
- sunken or displaced road surfaces or kerbs
- a rapid increase in creek water levels, possibly accompanied by greater turbidity.
Interesting fact: Some landslides move extremely fast, while others can move so slowly that they are almost undetectable.
Although landslides are fairly common in Australia, the continent is subject to less landslide activity than other countries. This is because Australia is characterised by old, hard rocks and a relatively flat landscape essentially free from the processes of uplift. It also receives less rainfall than countries with higher landslide risks. See examples of landslide events outside Australia.
Landslide spotters are needed!
Geoscience Australia needs landslide spotters all around Australia to report information on landslides which have been observed, heard about or mentioned in electronic and print media. By providing Geoscience Australia with details of landslide events, the Australian Landslide Database can be kept up to date.
Information can be forwarded by emailing: firstname.lastname@example.org or writing to:
Community Safety Group (Attention: Landslides)
GPO Box 378
Canberra ACT 2601