Multidimensional spatial index of long-term vulnerability to urban flooding: methodological design, application in Girona, and development of a virtual city simulator

Floods are among the most frequent and costly natural hazards, and their urban impact is ex-pected to intensify in the coming decades due to accelerated urbanization, land-use change, climate variability, and the progressive aging of infrastructures. In this context, flood risk man-agement cannot be limited to hazard-centered metrics or short-term emergency responses; it requires the incorporation of long-term vulnerability as a central element. This is understood as a sustained and evolving condition that reflects not only current exposure and susceptibility, but also the capacity of urban systems to adapt, recover, and transform when facing repeated or intensifying events over extended horizons. Integrating this perspective is key to aligning with international frameworks such as the Sendai Framework and the Sustainable Development Goals, which call for systemic resilience in the face of climate change. This thesis contributes to this agenda through the development of a spatially explicit Multidimen-sional Urban Flood Vulnerability Index (MUFVI), designed to identify vulnerability patterns. Struc-tured across four dimensions (social, economic, environmental, and physical) and three compo-nents (exposure, susceptibility, resilience), the MUFVI offers not only a static snapshot but also a framework adaptable to scenario analysis, sensitivity testing, and the progressive evaluation of interventions, while preserving spatial consistency in normalization, aggregation, and classifica-tion of results. The empirical application in Girona demonstrates how social and environmental factors accumulate over time to shape long-term spatial patterns of vulnerability, while the spatial overlay with hazard layers and combined sewer overflow (CSO) points allows the identification of zones where repeated stresses are likely to erode resilience. The Virtual City Simulator (VCS) reinforces this temporal and spatial perspective. Conceived as a synthetic Mediterranean city structured into eight typologies, the VCS allows the exploration of future trajectories by modifying values, weights, and assumptions of the indicators at the typol-ogy/spatial unit level, and by comparing baseline scenarios with resilience interventions. In doing so, it reveals not only present vulnerabilities but also their mappable evolution under plausible long-term scenarios. The thesis thus addresses a critical gap by linking spatial diagnostics with instruments that anticipate how vulnerability profiles may transform over decades, providing ev-idence to design adaptive and spatially targeted sets of actions in Mediterranean cities and in other contexts characterized by data limitations.