Australian nationwide assessment of social vulnerability in two decades through its linkage to the built environment

Evaluating social vulnerability and identifying at-risk populations are foundational to hazard risk mitigation and sustainable human settlement, yet these tasks entail distinct challenges that vary across urban-rural contexts and temporal scales. Despite Australia's escalating exposure to natural disasters, longitudinal, nationwide metrics of social vulnerability remain absent, with prior research constrained to localized or temporally fragmented analyses. Grounded in Cutter's social vulnerability framework, this study develops fine-grained, longitudinal indices of social vulnerability for urban and rural Australia across five census cycles (2001–2021). Spatial inequities, temporal trends, and associations between social vulnerability and 30 built environment indicators were analyzed using interpretable machine learning techniques. Key findings reveal that while the geographic distribution of the most vulnerable areas has remained stable over time, socioeconomic inequities of such areas have diminished whereas spatial clustering intensified. Resilient regions are characterized by enhanced access to public amenities, housing diversity, and commercial density—factors that collectively attenuate vulnerability. Furthermore, upgraded built environments attract socioeconomically advantaged populations, amplifying aggregated resilience. To our knowledge, this represents the first comprehensive, longitudinal, and spatially explicit national assessment of social vulnerability in Australia over two decades. The results elucidate critical trends in vulnerability and their interplay with built environment dynamics, offering actionable insights for place-based hazard mitigation, urban-rural sustainability, and infrastructure resilience. By bridging data gaps, this work addresses Australia's pressing need for evidence-driven policy and spatially targeted interventions to counter intensifying natural hazards and prioritize the resilience of human settlement.