Current Risk

At present Hallett Cove generally experiences landslides on a daily basis generally, in the form a rock falls or debris flow which is mild and generally not hazardous to the general public.⁶ There is however, the occasional moderate-severe landslide experienced in Hallett Cove region with implications that affect the general public and pose a significant safety risk in the immediate vicinity of a landslide.⁹ Throughout the coastal region where there are coastal cliffs, the rockfall can be quite dangerous if people are present during the time of the landslide.² High risk areas are generally signed as shown in figure 8 below. During significant weather events (i.e. times of drought, heavy rain, strong winds, etc.) the risk factor for landslides is significantly increased.⁹

Figure 8: Unstable cliff Hallett Cove (Source: Travis Hart, 2016)

What to look out for:

Non-vegetated areas are more susceptible to ground instability as the roots of vegetation act to hold the ground together.⁶

High angles of repose or steep slopes are a defining feature for a landslide and generally, the steeper the slope the greater the significance of ground movement and hence, the danger of a landslide is increased significantly.⁶

Extreme weather. Great caution must be taken in areas at risk of landslides as certain features of weather events can initiate ground movement.³

Heavy and/or prolonged rainfall is a significant factor that influences landslides and their severity. It is suggested that during these periods extreme caution be taken when in sloped areas, or areas near the coastal region and cliffs as frequent rockfall does occur and can be very dangerous.⁹

Loose surfaces are most at risk of movement (i.e. a rocky hill, sandy slopes, etc.). If you notice defects in the earth (e.g. cracks or holes in the ground), steer clear of these as these can be associated with high landslide risk areas.³

Current landslide Evidence

The most recent landslides that have occurred within Hallett Cove predominantly consist of mild – moderate rockfall and land flows, as seen below.

Figure 9: Evidence of rockfall Hallett Cove (Source: Travis Hart, 2016)

Figure 10: Evidence of rockfall 2 Hallett Cove (Source: Travis Hart, 2016)

Figure 11: Evidence of rockfall 3 Hallett Cove (Source: Travis Hart, 2016)

Figure 9, 10 and 11 show recent rock falls that have accumulated along the coastal cliffs in Hallett Cove. Some boulders are quite large and could inflict injury upon someone if they were hit by one although, this is quite unlikely as these areas are generally far away from high traffic areas. There are many places like these unstable cliffs side throughout the entire Hallett Cove coastal region.

Figure 12: Rockfall mediation effort (Source: Travis Hart,2016)

Figure 12 shows two steel rods inserted into the cliff side in an attempt to hold a mass of dirt and rock from falling. The use of steel rods is not an effective tecnique to prevent rockfall as the rock and dirt small enough weathers away with rain, and what remains is then supported by rusted and old steel rods. These rods work as a temporary solution although, they may give false confidence to someone venturing up the cliff side, and possibly give way under the extra weight of a person standing onto of them.

Figure 13: Recent rockfall Hallett Cove (Source: Travis Hart, 2016)

Figure 13 is a photograph of recently active rockfall that has occurred right next to a high traffic area in Hallett Cove. The stairs on the left were cordened off for 1-2 months at the time of the rockfall to prevent injury to people visiting the beach although, this does not stop everyone and injury from rockfall is very possible and can be deadly in some cases.

The physical nature of Hallett Cove (i.e. the moderate slopes, coastal cliffs, rocky foreshore and generally loose surface soils) increase the risk of landslides and the damage that would result from an occurance one. For safety reasons, associated signs and warnings should not be ignored and caution should be taken in higher risk areas as landslides occur regurly in the Hallett Cove area.⁹