Valutazione (behavioural design-based) multirischio di ambienti costruiti urbani e delle strategie di mitigazione: il caso delle piazze storiche

The urban Built Environment (BE) is prone to several risks. Slow onset disasters (e.g. temperature increase) raise slowly, widely affect daily BE fruition by its users, and can lead to critical conditions for them. Sudden onset disasters (e.g. terrorist acts, earthquakes) quickly affect the BE, causing direct damage to it and its users, and also the necessity to perform evacuation to restore safety levels. Slow and sudden onset disasters can also appear in a coupled manner, and their impact can be mainly noticed in public open spaces, such as squares, and historical scenarios, where relevant users’ exposure and vulnerability are combined with critical BE physical vulnerabilities. Multirisk assessment mitigation should hence rely on a behavioural-design approach, pursued at analysing users’ emergency response through simulation. Quick methodologies are also needed, and they can take advantage of typological BE and risk conditions while tracing rapid intervention criteria to be “tailored” in specific case-studies. This work defines a behavioural-design approach to assess multirisk and verify the impact of mitigation strategies in squares. In the proposed simulation logic, a slow-onset disaster (heatwaves) influences the initial users’ distribution in the square and then a specific sudden-onset disaster (a terrorist act, or an earthquake) is considered. The approach capability demonstration is provided by an application to a relevant typological historic square (hosting a special building) based on the analysis of real-world squares in the Italian context. Several sudden events (in terms of terrorist attacks, and seismic damages) are simulated, and two layouts (pre-mitigation versus mitigated) are also tested. Decision-makers could take advantage of the proposed approach and simulation tool for risk assessment and strategies effectiveness evaluation also in real-world scenarios.