Analysing Multi-Risk from Interacting Hazards: From Impact Chains to Risk-Informed Decisions

Abstract

Disasters rarely result from a single hazard acting in isolation. Hazards may occur simultaneously, trigger subsequent events, or alter the conditions under which future events unfold. Their consequences propagate through interconnected infrastructure, services and communities, while exposure and vulnerability change over time. Understanding these interactions requires approaches that connect physical processes with their wider societal impacts. This presentation shares experiences and results from the EU Horizon Europe PARATUS project, drawing on case studies in the Caribbean, the Alps, Bucharest and Istanbul. It explores how forensic analysis of past disasters and stakeholder-developed impact chains can support the identification of multi-hazard scenarios and reveal pathways through which impacts cascade across sectors. It then examines how these insights inform spatial risk assessment and the evaluation of risk reduction options. The presentation introduces complementary project outputs, including FastFlood for rapid flood modelling, RiskChanges for dynamic multi-hazard risk assessment and comparison of alternatives, serious games for exploring systemic risk, and stress-testing guidance for examining system vulnerabilities. Particular attention is given to connecting qualitative understanding of interdependencies with quantitative estimates of damage and losses. The concluding discussion addresses practical challenges: incomplete data, uncertainty in hazard interactions, changing vulnerability, and translating complex assessments into usable decision support. The central message is that analysing multi-risk requires both modelling interacting processes and working with stakeholders to understand how their consequences unfold and where interventions can be most effective.

Bio

Cees van Westen is Professor of Multi-Hazard Risk Dynamics at the Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, the Netherlands. His research focuses on geospatial approaches to natural hazard assessment, changing multi-hazard risk and decision support for disaster risk reduction, with particular expertise in landslides. He has extensive international experience in research, capacity development and national risk assessments across Asia, Latin America, the Caribbean and Europe. He is a principal investigator in the EU Horizon Europe PARATUS project and contributes to the development of practical tools and training for multi-hazard risk assessment.