Coastal vulnerability to wave impacts using a multi-criteria index: Santa Catarina (Brazil)

The damage of coastal infrastructure due to wave action has stimulated the need for vulnerability assessments for integrated coastal management. Vulnerability is described as the ability of people living in an area to anticipate, cope with, resist and recover from the impact produced by a coastal hazard. This study aims to develop a multi-criteria index to assess coastal vulnerability to waves. Therefore, we analyze the Santa Catarina State (southern Brazil) coastline vulnerability to the incident wave climate. The applied coastal vulnerability index (CVI) was obtained by integrating the adaptive capacity index (ACI), composed of socioeconomic and locational variables, and the susceptibility index (SI), composed of physical variables. The resulting coastal dynamics from nearshore wave processes were analyzed through numerical models and integrated with other variables in a geographic information system (GIS). The relevance of the variables to the index was obtained by the analytic hierarchy process (AHP). The variables and indices were hierarchized into five vulnerability classes and represented in the administrative sectors defined by the local State Coastal Management Plan. Based on the AHP results, the physical variables were considered more relevant than the socioeconomic and locational variables. In general, the southern portion of the state presented higher susceptibility degrees, a lower income per capita and a lower number of second residences than the northern portion. At the same time, the northern portion presented higher percentages of developed areas, which are predominantly situated along susceptible and vulnerable segments. The numerical modeling of wave propagation has a large impact on the vulnerability as a function of the higher weights assigned to the related variables by experts and the high variability of the significant wave height along the state's coastline. Our results emphasize the importance of the inclusion of physical variables, such as waves, when defining coastal management measures in coastal zones.