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This report contains a brief overview of landslides in Hallett Cove; which is situated 18 km South-West of Adelaide. The entire suburb rests on the side of O’Halloran Hill; and a gentle – moderate slope is experience throughout most of the suburb. Situated along the coast, it has steep cliffs and consists of a rocky foreshore. Landslides have occurred throughout Hallett Cove predominantly as rockfall along the steep coastal cliffs although, significant landslides have occurred in the past and may occur in the future.

Figure 1: Unstable Cliff (Source: Travis Hart, 2016)

Landslides are defined as the downward and outward movement of a mass (i.e. a mass of rock, sand, soil, debris or other ‘earth’ types), down a slope, due to the force of gravity.⁷ A landslide is composed of at least one of the following principle forms: falling, sliding or flowing landslides.¹¹ This informative report will investigate all three forms of landslides in the Hallett Cove area.

The cause of a landslide is generally due to effect of one or more earth processes (i.e. an earthquake, heavy rainfall, drought, etc.); although, human interaction is becoming an increasingly significant contributor to landslide occurrence.⁴ In the Hallett Cove area, the slanted terrain along with the steep coastal cliffs, allows for the frequent occurrence of landslides. Observed frequency of landslide events that are mild, occur on a daily basis and generally do not affect the general public although, more significant landslides have occurred in the past.⁹