Virtual testbed for multi-risk assessment: defining RETURNVILLEs to support the analysis and testing of DRM and CCA solutions in realistic urban contexts

Urban areas may be considered as hotspots for disaster risk. The intrinsic complexity and interdependency of urban systems in a multi-risk framework call for integrated, system-based approaches to understand and model multi-risk processes and to support effective Disaster Risk Management (DRM) and Climate Change Adaptation (CCA) strategies. In this context, Virtual Testbeds (VTBs) have emerged as effective instruments for the development, benchmarking, and testing of quantitative community resilience and multi-risk assessment methodologies. VTBs are explicitly designed to enable controlled experimentation, stress-testing, and exploration of possible present or future risk scenarios through simulation. This paper presents the development of two imaginary, yet realistic urban Virtual Testbeds created within the RETURN project. The proposed VTBs represent typical Italian urban settlements: a coastal RETURNVILLE, RV1, and an inland, intra-mountainous town, inland RETURNVILLE, RV2. Their structural foundation is derived from a hybrid approach that combines urban components from real cities to ensure realism while avoiding sensitivity and data-access constraints. The paper describes the GIS-based exposure datasets forming the operational backend for hazard and risk simulations. Moreover, with the aim to illustrate a possible approach for investigating complex multi-risk scenarios instantiated for the VTB, the conceptual framework for a bottom-up multi-risk assessment methodology, based on risk storylines and impact chains, is presented. The proposed framework may be used for testing of DRM and CCA strategies through what-if scenarios, supporting decision-makers for the assessment of the potential consequence of actions (e.g. reducing the impacts) according to alternative design scenarios towards a holistic, transferable, and policy-relevant urban resilience analysis.