Virtual testbed for multi-risk assessment: application to the Inland RETURNVILLE

Urban areas are characterized by high level of exposure in terms of population, assets, and highly interconnected systems, which can lead to multiple cascading effects under single and multi-hazards scenarios. Effective disaster risk management requires integrated approaches and models that account for hazard interactions as well as cascading effects within urban systems, but real-world application is often limited by data availability and coordination challenges. Within the framework of the extended partnership RETURN, two Virtual Testbeds (VTBs) have been developed to represent realistic Italian urban contexts, enabling the integration of hazard scenarios, exposure data, and vulnerability models within a reproducible digital environment. VTBs provide controlled digital environments that can support the systematic exploration of interactions among hazards, infrastructure, and social systems. This study presents an application for the Inland RETURNVILLE, the VTB representing an inland urban settlement exposed to earthquake and volcanic hazards, with the aim of illustrating multi-risk interactions modelling both at the building level - where ashfall increases seismic vulnerability - and the system level - where post-earthquake building collapses disrupt the urban road network. Results show that interactions between hazards may notably increase vulnerability of buildings, substantially amplifying building damage and economic losses. Additionally, cascading effects within the urban system, such as disruption to road network, further affect mobility and accessibility, particularly in dense historic urban areas. The study highlights the importance of considering both multi-hazard interactions and systemic cascading effects, and demonstrates how VTBs provide a flexible, transparent platform for testing mitigation strategies and supporting urban resilience planning.