Coastal vulnerability and urban planning: Spatial analysis and institutional challenges for incorporating Climate risk in Olivença, Ilhéus, Brazil

Sea-level rise imposes growing challenges to urban planning in coastal cities, especially in areas of low altitude, strong real estate pressure, and high environmental sensitivity. However, the incorporation of climate risk into land-use planning instruments remains limited in many urban contexts of the Global South, creating gaps between the spatial diagnosis of vulnerability and its translation into preventive urban regulation. This article analyzes the socio-environmental vulnerability of the coastal zone of Olivença, in the municipality of Ilhéus, Bahia, Brazil, and discusses its relationship with current urban planning. The research combines Geographic Information Systems, multicriteria analysis using the Analytic Hierarchy Process method, and normative analysis of local urban parameters to construct an Integrated Socio-environmental Vulnerability Index. The results indicate that 13.67% of the analyzed area presents high and very high vulnerability, concentrating mainly on the urbanized coastal strip, in sectors near mangroves, and in areas where low altitude, urban land use, and population exposure overlap. The overlap between the index and zoning reveals that vulnerable areas coincide with sectors where urban uses and possibilities for densification are still permitted, evidencing a logic of socialized risk. By proposing a typology for incorporating climate risk into urban planning, the study shows that local coastal vulnerability results not only from physical conditions but also from normative choices that can reproduce future climate exposure.