The hazards associated with the geomorphological evolution of coastal cliffs have been widely studied, and various hazard mitigation measures have been incorporated into coastal management plans. However, despite the global significance of beach tourism, most studies overlook the exposure of beach users on cliff-bound beaches, which result in unknown risk levels. This study presents a novel coastal index-based methodology to quantify risk over time and space for beach users, based on the combination of hazard and exposure indices. The Algarve coast was selected as a test site due to its high visitor statistics, embayed cliff-bound beaches, and records of incidents from cliff mass movements that impacted the safety of beach users. The coastal risk index was applied to selected beaches in the central Algarve by geospatially mapping the hazard, exposure, and risk components, and their temporal variations. The hazard index varied seasonally across hazard zones based on the monthly frequency of mass movements. Two approaches were explored for the exposure index, considering (1) temporal variation, and (2) both temporal and spatial variation in beach occupancy. The first identifies seasonal risk level changes, while the second provides detailed spatio-temporal risk patterns, identifying high-risk locations within beaches. These risk hotspots are influenced by seasonality and the location of beach amenities where beachgoers often congregate. The proposed methodology effectively quantifies risk variability through time and space, and is applicable to any cliff-bound beach, provided that necessary datasets can be obtained. Implementing this assessment approach can assist coastal managers in planning appropriate adaptation measures to reduce risk by minimizing human exposure on beaches bounded by rocky cliffs.
Dimabayao et al. (Thu,) studied this question.