Risk Assessment for Rocky Cliffs: Application to the Coastal Area of Lagoa, Southern Portugal

Abstract Coastal areas are highly vulnerable to extreme events, particularly in rocky coastal environments where cliff collapse poses a significant risk to human occupation. This study presents a simplified method for assessing coastal risk at the top of rocky cliffs, integrating hazard and exposure into a single risk index. The methodology is based on the Coastal Risk Assessment Framework and incorporates hazard (inland extent of cliff mass movements) and exposure (land use) indices to calculate a Coastal Index (Ci). This approach was applied to the coastline of the municipality of Lagoa (Algarve, southern Portugal), which is characterised by indented rocky cliffs, pocket beaches, and subject to high touristic pressure. Risk maps were developed to determine the spatial variability, revealing a predominantly low to moderate risk along the coastline. However, 22% of the study area was identified as having high to very high coastal risk, particularly in areas with urban or touristic development close to the cliff edge. The method provides a straightforward tool for coastal management, enabling the identification of risk hotspots and the optimization of resource allocation for risk reduction.