Multi-Hazard Risk Assessment in Historic City Centers at the District and Building Levels: An Open-Source GIS Workflow

Historic city centers are characterized by dense and heterogeneous built environments, making them particularly vulnerable to the compound effects of seismic, flood, and landslide hazards. In this context, information required for vulnerability and risk assessment is often fragmented, limiting the effectiveness of preventive planning and mitigation strategies. This reveals an operational gap in current practice; therefore, this work aims to support decision-oriented, multi-level assessment in historic centers through a replicable approach, even in low-resource contexts. A GIS workflow integrates territorial multi-hazard screening with building-scale overlay mapping of literature-based vulnerability, exposure, and risk classes. Applied to Montalbano Jonico (Italy), the screening analyzed 15 census sections and identified three hotspot areas within the historic center for detailed assessment. Within these critical areas, building-scale mapping yields intervention priorities: 42.8% of building aggregates show High-Very High seismic vulnerability (44.4% in Very High-Maximum Priority risk classes) and 50% show Very High landslide vulnerability (63.2% in Very High-Maximum Priority risk classes), mostly affecting masonry and residential buildings. Overall, the framework provides a practical decision tool to support municipal administrations, technical offices, civil protection agencies, and built heritage management institutions, and is designed for GIS-BIM interoperability.