A novel dynamic disaster risk assessment of Urban Built Environments: an application to flood and earthquake

Disaster risk assessment in Urban Built Environments (UBEs) must consider the joint impacts of possible hazard conditions and dynamics in UBE use, and thus the spatiotemporal variations in the number (exposure) and typology (individual vulnerability) of the hosted population. The integration of such concepts could be boosted by multiscale approaches representing the complex interactions among the UBE subsystems, supporting scenario creation. Building-level data should be aggregated at the scale of urban public open spaces (e.g. streets, urban squares), due to their relevance for user UBE use in normal and emergency conditions. This work adopts this open-space-centred approach and defines a novel methodology for dynamic single-risk assessment in UBEs, combining physical vulnerability, hazard, user exposure and vulnerability. The methodology is applied to flood and earthquake risks, as relevant disasters for UBEs, and allows to mark relevant “hot-spots” in UBE, in these two relevant disasters, and considering different spatiotemporal dynamics in user factors. Validated methods for building-scale analysis of risk factors are adapted to calculate risk assessment indexes at the open space level, including alternative scenarios of hazard (in terms of flood/earthquake severity) and typical occupancy schedules in UBE use. The application to a relevant UBE demonstrates the approach capabilities in detecting open spaces which represent recurrent and scenario-sensitive “hot-spots” to floods and earthquakes, and remarks how consistent risk-level differences exist due to the use dynamics. The proposed method can support decision-makers in intervention prioritisation, focusing on common “hot-spots”, and tailoring risk-mitigation and management strategies, depending on the specific scenario.