Risk management of coastal cliff hazards – A case study from the Surf Coast, Southwest Victoria

Coastal cliffs pose a significant and unpredictable landslide hazard to users of coastal areas. The surf coast region of Southwest Victoria encompasses more than 50 km of coastline from Torquay to Lorne. The region is a world-class surfing destination and attracts hundreds of thousands of visitors each year, from all over the world. The coastline is variable, with low-lying sand dunes juxtaposed with large sea cliffs. From Torquay to Aireys Inlet, cliffs comprise variably cemented Paleogene aged sediments of very low- to low strength sandstone, calcarenite and limestone with soil horizons, transitioning to the Cretaceous rocks of the Otway Basin around Lorne. This combination of unstable cliffs and the popularity of the area for coastal users presents a challenge to manage the geotechnical risk whilst preserving public amenity. This case study looks at how GHD aided the Great Ocean Road and Parks Authority (GORCAPA) in understanding the hazard and risk posed by coastal cliffs and how GORCAPA moved away from traditional reactive management methods to a more proactive approach. Part of this involved identifying “hotspot” areas where resources could be better targeted to monitor and mitigate risks. A key aspect was development of a Trigger Action Response Plan (TARP) and integration with the wider Coastal and Marine Management Plan (CMMP). The TARP allows GORCAPA staff to understand the actions that need to be undertaken following certain events and, tied to the CMMP, aids in a more proactive response to developing cliff risks. The reality of risk management for this area, with multiple hazards meant that only the consequences of the hazard could effectively be reduced. Restricting access to large expanses of popular beaches in the region is not feasible, therefore other strategies were deployed, including education programs in local schools, improved hazard signage and improved communication of hazards with the public via social media streams. The implemented approach has mitigated the likelihood and severity of potential casualties. An effective risk management program is essential to keeping users of the coastline safe and informed about hazards posed by cliffs.