Developing plausible scenario-based multi-risk storylines for coastal urban areas

This study explores the possibility of adopting a scenario based approach, which relies on the physical modelling of plausible hazardous events, to develop realistic site specific multi-risk storylines for urban contexts of different typologies (Marciano, Peresan, Pirni, Pittore, Tocchi, Zaccaria, 2024. IJDRR, 104972). Properly defining the hazard scenario and the urban context of interest, in fact, is essential for the development of risk storylines, as it enables the identification of relevant exposure features and local vulnerabilities affecting the urban system.

Physical modelling of earthquakes and cascading hazards (e.g. earthquake induced tsunamis or landslides), as well as sequential hazards (e.g. a storm surge followed by a tsunami) provides the basis for defining plausible (yet unobserved) multi-hazard and risk scenarios. For the definition of possible impacts, high-resolution exposure models are also needed at the local scale, especially for hazards which exhibit high spatial variability. In this study a methodology is considered, which allows developing high-resolution exposure models for population and residential buildings, based on different publicly available data sets (Badreldin, Scaini, Hassan, Peresan, 2025. IJDRR, 121, 105403).

The socio-economic characteristics and possible social vulnerabilities are also important factors that may influence impacts and the effectiveness of response and mitigation strategies. The experimental testing of the multi-risk storyline methodology was carried out for two selected urban areas along the Northern Adriatic coasts (i.e. Trieste and Lignano Sabbiadoro), considering both rather frequent (storm surge) and rare (tsunami) events. The proposed approach can be easily replicated in other urban areas with similar features, e.g. those located along the coasts of Western Adriatic (Peresan and Hassan, 2024. MEGR, 6(2), 87–110). The first phase of this experiment aimed to identify the potential impacts of the proposed scenarios on the different components of the urban ecosystem, while the second phase explored the possible interventions and mitigation strategies, in order to highlight relevant complexities and interactions. Through a participatory process, the multi-risk storylines engaged institutional actors, technical experts, and local communities, transforming data, experiences, and perceptions into dynamic and shared risk scenarios. The resulting narratives do not intend to merely describe past events, but rather to anticipate plausible future scenarios and viable response, recovery and mitigation actions, contributing towards integrated multi-risk management strategies.

The study demonstrated that the developed multi-risk storylines, based on plausible multi-hazard scenarios, provide a systematic method for exploring how the complex interplay between hazards and urban systems may impact a society, and can be applied to support and rationalise decision making and inform preparedness for multi-risks management and mitigation.

Acknowledgements: This research is a contribution to the RETURN Extended Partnership (European Union Next-Generation EU—National Recovery and Resilience Plan—NRRP, Mission 4, Component 2, Investment 1.3—D.D. 1243 2/8/2022, PE0000005).