Coastal sensitivity and population exposure to sea level rise: a case study on Santa Catarina Island, Brazil

Climate change intensifies the pressure on the coastal zone, endangering ecosystems, socioeconomic activities and coastal infrastructure, with direct impact on the economy of these areas. Although coastal hazard effects have been widely studied, the lack of information in local scale prevents a more effective urban and natural resources management. In order to assess coastal sensitivity and the population exposure to sea level rise, this study evaluated and adapted an index to represent sectors more likely to suffer from the effects of erosion and flooding along the coast of Santa Catarina Island, Brazil. A methodology centred on segmentation and index-based strategies was adapted to the local conditions, using criteria representing coastal geomorphology and dynamics to assess natural sensitivity, which was combined with census data to represent population exposure. Santa Catarina Island was chosen as a test site for three reasons: (a) the existence of a full set of previous data; (b) its diversity of environments; and (c) an important record of erosion and inundation events in several of its beaches. Results showed that the most sensitive areas are located on the island's eastern shore, reflecting its higher exposure to the incidence on the ocean waves. Although this west-east contrast had been expected as the key sensitivity feature in the island, its integration with population density allowed the recognition of a more complex pattern. Since variable population densities occur in the both sides of Santa Catarina Island, highly sensible but not urbanized segments were detected in the eastern coast (low exposure), as well as densely occupied sectors in not sensible areas of the western coast (high exposure). The adopted strategy (use of a demographic descriptor to obtain exposure from its integration with sensitivity), was not proposed in the original methodologies of sensitivity assessments and improved the representativeness of the spatial model. Obtained results demonstrated the importance of comprehensive coastal management plans, where both physical and demographic aspects should be considered.