Australasian Coasts and Ports Conference, 2025, Adelaide
Coastal erosion and instability along cliff shorelines are a worldwide issue, in particular when land, assets or public are affected by coastal cliff erosion or instability. An understanding of areas susceptible to coastal erosion and instability requires expertise in both coastal processes and cliff instability processes. Previous papers have set out methods of assessing and mapping coastal erosion hazards/susceptibility extents. However, next steps to mitigate these hazards are typically left out. Therefore, this paper sets out practical methods and new developments to assess coastal cliff hazards and includes next steps such as risk to assets or life, and practical adaptation actions are set out in this paper.
Coastal cliff erosion and instability hazards can be assessed on a range of scales, ranging from regional-scale (e.g., State-wide) to site-specific or local-scale. This is typically limited to coastal erosion and instability along the cliff crest or top. Recent developments also consider susceptibility of cliff erosion and instability seaward of the cliff toe, such as talus runout extending onto the beach. This has recently been applied on a regional scale in Victoria, Australia, and aims to inform risk to public safety.
A risk assessment is typically undertaken after completion of the hazard/susceptibility assessment and typically considers relevant assets and other land values. Assets or values can be ranked based on vulnerability or importance, with risk ratings are assigned to each asset/value. In addition to risk to assets/land, the risk to public walking along cliffs is another important consideration, with an approach to assess risk to public safety set out in this paper. The resulting risk ratings are then used to prioritise what asset or section of coast requires adaptation actions to be implemented.
For coastal cliffs a range of typical adaptation actions are considered. This ranges from implementing cliff hazard signs to constructing palisade walls to stabilise the cliff slope. A range of best practice adaptation actions are discussed in this paper.
