Prioritization of risk reduction strategies by multi-criteria decision analysis: the case of the Lomellina area (Northern Italy)

Natural risk management in areas exposed to multiple hazards remains a major challenge, as mitigation planning often relies on single-hazard approaches that fail to capture combined impacts and territorial complexity. In this context, we present a Multi-Criteria Decision Analysis (MCDA) framework design to support effective risk reduction in multi-hazard settings. The framework, developed within the Italian RETURN project (Multi-risk science for resilient communities under a changing climate), integrates impact modelling to derive risk scenarios, technical and expert judgement to assess the economic, environmental and societal sustainability effects of mitigation options, and participatory stakeholder processes to define the weighting of evaluation criteria. The framework is demonstrated through a case study in the Lomellina area, one of the most fragile territories in Northern Italy, characterized by multiple pressures including multi-risk exposure (i.e., floods, earthquakes, drought and technological accidents), depopulation, ageing populations, limited access to essential services, and fragmented governance. The MCDA framework is applied to compare two alternative risk reduction strategies: levee raising and the relocation of the most exposed population to seismically retrofitted buildings. Results highlight the potential of the proposed framework to support transparent and informed prioritization of risk reduction strategies in multi-hazard and fragile contexts.