A framework to quantify the impacts of multi-hazard interactions

Hazards do not always occur in isolation. They often interact in space and time, triggering, compounding, or amplifying each other, resulting in complex, cascading impacts. Recent decades have seen a rise in the frequency, intensity, and complexity of such events. Understanding how one hazard can trigger or increase the likelihood of another is essential for realistic risk assessment <br/>and effective decision-making. Recognising this, the Sendai Framework for Disaster Risk Reduction have called for integrated, multi-hazard approaches to risk assessment and management. However, despite advances in multi-hazard risk analysis, existing methods still fall short in quantifying the dynamic and interconnected nature of multi-hazards. Traditional approaches have typically focused on single hazards or considered multiple hazards independently, neglecting the ways in which hazards can interact over space and time. This can lead to underestimation of risk.<br/><br/>To address these, the study introduces a structured, five-step framework designed to quantify and visualize multi-hazard interactions. The framework begins with the identification of relevant hazards and their potential interrelations, such as triggering, cascading, conditioning and independent. Spatially, the hazards can be overlapping, source and spread or not overlapping and temporal interrelations include simultaneous, consecutive and events after a long time. In the third step, hazard modelling approaches are applied to reflect these interactions. Step four incorporates evolving exposure and vulnerability, accounting for dynamic changes. This emphasizes that disaster impacts are not static, and assets can become vulnerable as events occur. The final step is the impact assessment that accounts for interrelations.<br/><br/>The final step is impact assessment that accounts for interrelations. The study also presents a novel visual method that organizes multi-hazard events along a temporal axis and categorical sections for triggers, hazards, and impacts. This framework and visualisation help stakeholders grasp the sequence and interdependence of events, supporting both retrospective analysis and forward-looking perspectives. To demonstrate the framework’s applicability, three real-world case studies are analyzed: the 2023 Kahramanmaraş earthquakes in <br/>Turkey, the 2021 La Soufrière volcanic eruption in Saint Vincent and a case study of Dominica. The results highlight how multi-hazard interactions can have non-linear, compounding effects and alter exposure and vulnerability conditions. By systematically capturing these patterns, the framework not only reconstructs past event sequences but also aids in anticipating future scenarios under evolving conditions.