From risk assessment to mitigation and emergency planning for multiple natural hazards in urban built environments: a mesoscale, user-dynamics based framework

The mitigation of impacts due to natural hazards (such as floods and earthquakes) on Urban Built Environments (UBEs) should take into account disaster risk assessment tasks as the fundamental steps to build on reliable, comprehensive and effective emergency scenarios. Assessment should hence integrate hazard conditions and urban-use dynamics, as these together determine the spatio-temporal variability of user exposure and vulnerability. To address these interactions, a multiscale approach is essential, enabling the representation of complex relationships among UBE subsystems and supporting the construction of alternative risk scenarios. In this perspective, building-scale information is aggregated at the level of urban public open spaces (e.g., streets and squares), which act as key elements in everyday activities and as critical assets during emergencies. This study proposes a novel framework using dynamic single-risk assessment in UBEs to provide insights into possible mitigation and emergency planning strategies. It integrates the main components influencing risk (hazard, physical vulnerability, user exposure, and user vulnerability), and is applied to floods and earthquakes as relevant disasters in UBEs. Leveraging the microscale level, data are then aggregated into open-space-level risk indices, allowing the identification of scenario-sensitive hotspots under different spatio-temporal user configurations. The application to the historical UBE of Senigallia (Italy) highlights how variations in urban use significantly influence risk distribution and severity, confirming the relevance of integrating behavioural dynamics within urban-scale assessments. The results provide an operational basis for advancing risk mitigation and emergency planning. The identification of recurrent and scenario-specific hotspots supports the prioritisation of interventions, the optimisation of resource allocation, and the development of targeted, context-specific strategies. In this sense, the proposed framework acts as a bridge between risk diagnosis and risk management, providing decision-makers with actionable evidence to customise mitigation measures and emergency response plans according to specific natural hazard scenarios and user dynamics.