Driving forces of sea level rise risk for parish level risk management

Abstract

This study assesses SLR risk in mainland Portugal by analysing variables representing hazard, exposure, and social vulnerability at the parish level. It calculates baseline (2011) and future (2040, 2070, and 2100) SLR risk index for the SSP1, SSP2, and SSP5 scenarios to provide empirical evidence for medium and long-term territorial planning and risk management. The SLR risk index was calculated as the geometric mean of three dimensions: hazard, exposure, and social vulnerability. Hazard was assessed based on the extent of floodable areas, considering medium- and long-term SLR scenarios, meteorological sea level rise, and wave spread. Exposure was evaluated for 2011, including residential buildings and estimated population, using a dasymmetric analysis. Social vulnerability was assessed in 2011, based on criticality and support capacity, using principal component analysis. Future risk was simulated by combining projected climate scenarios with baseline socioeconomic data. Finally, a hierarchical cluster analysis was performed to identify distinct risk profiles. Projections indicate a non-uniform intensification of coastal hazards. Under the high-emission SSP5 scenario, the median hazard index increases by approximately 40% between 2011 and 2100. The hazard spatial heterogeneity is driven by local geomorphological system dynamics, biophysical variations, and uneven distribution of protection measures rather than uniform inundation. Asset exposure worsens consistently under SSP5 as expanding flood zones intersect existing populated areas and coastal infrastructure. The sharpest increase in affected buildings is concentrated within the 2040-2070 window, although with spatial polarisation. Many units with negligible exposure will coexist alongside highly vulnerable, high-density coastal fronts. The socio-vulnerability analysis reveals a spatial pattern in which low-vulnerable social groups typically concentrate in high-risk zones, highlighting the critical need for highly contextualised approaches when designing local public policy. Therefore, this comprehensive assessment provides critical baseline data showing that effective coastal management requires highly contextualized, proactive, local-level adaptation planning.