Panagiotis Asaridis

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.

Effective risk management in multi-hazard contexts represents a key focus of the Italian RETURN project (Multi-risk science for resilient communities under a changing climate). Within this framework, a Multi-Criteria Decision Analysis (MCDA) approach has been developed to support the prioritization of risk reduction strategies. The proposed framework integrates three complementary dimensions of the problem at stake: (i) the optimization of risk reduction in complex multi-hazard settings, accounting for all relevant dimensions of risk (i.e., impacts on individual well-being, the built environment, public services, the natural environment, communities, business activities, and the financial system); (ii) the assessment of the economic, social, and environmental sustainability of proposed actions under current and future climate change conditions; and (iii) the systematic integration of stakeholders’ values, preferences, and objectives into the decision-making process. To achieve these goals, the framework combines multiple methodologies, including multi-hazard impact modelling for the definition of ex-ante and ex-post risk scenarios, expert-based assessments to evaluate long-term sustainability, and participatory processes to ensure effective stakeholder engagement. The MCDA framework provides a valuable decision-support tool for informed, transparent, and inclusive decision-making, aligned with efforts to enhance community resilience and sustainability, and is particularly relevant for policymakers, practitioners, and civil protection agencies.

Flood-related damage has increased dramatically in recent decades with direct and indirect economic impacts accounting for a large share of gross national products. Therefore, there is an urgent need to acquire more quantitative knowledge about flood damage to mitigate economic losses and reduce exposure to flood risk.Firms are especially affected in case of flood. Still, flood direct damage assessment to businesses is hindered by the paucity of available data to characterize the enterprises, the lack of high-quality damage data to derive new models or validate existing ones, and the high variability of activity types which hampers generalization. On the indirect damage side, the existing literature predominantly focus on estimating damage at the macro scale, leaving a gap in understanding the specific impact on individual firms.This study contributes at improving knowledge about types and extent of damage of flood events on economic activities through the analysis of empirical data, focusing on direct and indirect damage at the micro-scale, with specific reference to the Italian context. The investigated data derive from observed direct damage records collected after six flood events in Italy. The information on the surface of the building, the typology of the affected firms (i.e., NACE category) as well as on local water depth levels and the classification in damage components (building, equipment, and stock) permitted to develop an econometric model to forecast the direct damage and to analyze the mechanisms of flood damage across the economic sectors. The original dataset was then enriched with information included in the financial statement of flooded activities that has been used to investigate indirect damage.Despite characterized by significant uncertainty, obtained results supply first tools for the prediction of flood direct damage and for the quantification of indirect damages to firms for the Italian context, in the support of more effective risk mitigation actions. In fact, the model identifies the more vulnerable elements within the business sectors orienting modelers and decision-makers choices.

The study aims to provide the Lombardy Region, the primary stakeholder in the project, with a procedure for evaluating and classifying structural flood risk mitigation measures. The primary objective is to assist the regional authority in identifying priority interventions for public funding. A step-by-step procedure has been developed to assess and rank all projects submitted to the Region, selecting priority projects based on technical considerations—evaluating feasibility, effectiveness, and sustainability of the proposed measures—and the preferences of policymakers. The assessment procedure's conceptual structure was tested using case studies, including both feasibility studies and executive projects, to determine the level of technical insights required at each planning phase of public works. The methodology relies on Multiple Criteria Analysis (MCA) techniques, enabling the simultaneous consideration of various, non-directly comparable criteria in a complex decision-making context. These criteria encompass technical features of proposed works, potential territorial constraints, and interferences in the intervention area (feasibility); the effectiveness of measures in reducing flood risk and associated costs; and the environmental and social co-benefits and disbenefits of each intervention (sustainability). Specific indicators, either ad hoc defined for the study or referenced from current regulations and guidelines at national and regional levels, are employed to evaluate the criteria. Stakeholder participation, particularly from the Region, River District Authorities, and Municipalities, is crucial throughout the process, especially in the final phase of aggregating (weighting) all criteria. This aggregation produces an overall performance score for each option, enabling the derivation of a regional ranking of flood risk mitigation strategies. The collaboration between academia and public institutions is highlighted as essential for enhancing the efficiency of disaster risk reduction policies.

Within the context of the Italian RETURN (Multi-risk science for resilient communities under a changing climate) project, the objective of WP 7.2 is the definition of national guidelines for the evaluation of the effectiveness of alternatives of intervention in natural risks management, by considering in detail Multi Criteria Analysis (MCA) tools. The focus is on (i) multi-hazard contexts, for which state-of-the-art and knowledge is limited, (ii) the different phases of the risk management chain, and (iii) the variety of structural and non-structural measures that can be adopted. The present contribution describes results reached so far in this direction. First, First, we propose a flowchart that illustrates the process leading to the ranking of alternative strategies through MCA. The objective of the flowchart is to highlight the operative steps required for its implementation, including: (i) the identification of intervention alternatives and their characterization in terms of spatial and temporal scale of effectiveness, potential risk reduction, and secondary impacts on interested communities, (ii) recognition of stakeholder’s objectives and their respective dimensions, (iii) definition of attributes and indicators according to which alternatives are evaluated, (iv) selection of the most appropriate MCA tool and definition of related parameters, and (v) performance of sensitivity analysis. The development of the flowchart emphasized that establishing guidelines for applying MCA to multi-hazard risk management requires two ongoing fundamental steps (i) an in-depth, generalized investigation of the types of elements exposed to the different natural hazards as well as the identification of potential direct and indirect impacts on them in case of an event; (ii) the definition of an abacus of alternatives which identifies the most promising measures that can be implemented in a given context, and characterizes them in terms of potential risk reduction or increase (with respect to different hazards), and temporal and spatial scale of effectiveness.

Power grids can be significantly affected by floods that can cause power outages with widespread impact on social and economic activities. In this work, we propose a “What-if” scenario analysis by modelling and simulation, which makes use of a hydraulic model to simulate hazard scenarios, fragility curves to describe the process of failure of the power grid components, and a power flow model to assess power outages. A synthetic case study is worked out with reference to the IEEE 14 bus system benchmark serving different categories of electricity customers. The proposed modelling and simulation-based analysis can be used to identify the most critical components to protect for the security of power supply.

Flood damage assessment is a critical aspect in anydecision-making process on flood risk management. For this reason, reliabletools for flood damage estimation are required for all the categories ofexposed elements. Despite infrastructures can suffer high economic losses incase of flood, compared to other exposed sectors, their flood damagemodelling is still a challenging task. This is due, on the one hand, to thestructural and dynamic complexity of infrastructure networks, and, on theother hand, to the lack of knowledge and data to investigate damagemechanisms and to calibrate and validate damage models. Grounding on theinvestigation of the state-of-the-art, this paper presents aconceptualization of flood damage to power grids and reviews themethodologies in the field for an in-depth understanding of the existingmodelling approaches, challenges, and limitations. The conceptual modelhighlights: (i) the different kinds of damage (i.e., direct, indirect, andsystemic) the network can suffer, (ii) the hazard, exposure, andvulnerability parameters on which they depend, (iii) the spatial andtemporal scales required for their assessment, (iv) the interconnectionsamong power grids and economic activities, and (v) the different recipientsof economic losses. The development of the model stresses the importance ofdividing the damage assessment into two steps: the estimation of damage inphysical units and the consequent economic losses in monetary terms. Thevariety of damage mechanisms and cascading effects shaping the final damagefigure arises, asking for an interdisciplinary and multi-scale evaluationapproach. The ultimate objective of the conceptual model is to be anoperative tool in support of more comprehensive and reliable flood damageassessments to power grids.

Natural hazards are a leading driver of power outages worldwide. Although flooding has lower impact compared to other natural hazards, it may still have a significant impact on power grids functionality in terms of frequency, magnitude, and duration of power outage. Maintaining the security of power supply under emergency conditions triggered by natural hazards, such as floods, is a challenging task because of the inherent structural and dynamic complexity of the system. In such a context, this paper presents a new model for the estimation of direct, indirect, and systemic flood damage to power grids. The key objective of the model is to be an operational tool able to: (i) consider the magnitude, probability of occurrence, and spatiotemporal variability of flood hazard, (ii) identify the vulnerable components of power grids and evaluate their probability of failure in case of flood, (iii) analyze the cascading effects of individual or multiple failure states on the power transmission and distribution networks, (iv) and assess the impacts of power outages on the power-dependent economic activities and infrastructures. To achieve this goal, the model combines deterministic flood hazard scenarios, a spatially distributed power flow model, fragility curves of power grid components for different voltage levels, and a social model, describing the various users connected to the power grid. For quantitative illustration purposes, a synthetic model has been developed by referring to the IEEE 14 bus system benchmark, to which a spatial dimension has been allocated. Furthermore, to account for differentiated social impacts, the power flow model has been linked to a synthetic social model including several communities (hubs) with different social and economic characteristics.The development of the synthetic model constitutes a preliminary step in understanding and quantifying the impacts that sustained power interruptions caused by floods can have on the customers of power grids. Next research efforts will be devoted, on the one hand, to the adoption of a probabilistic approach, by substituting deterministic hazard scenarios with spatial dependent, probabilistic ones; on the other hand, to the sensitivity analysis of the different modeling phases to identify the components of the model on which the final damage scenario depends mostly. The final aim is to provide a modeling and simulation tool for risk analysis, so as to enable stakeholders, authorities, and policy makers to formulate effective strategies to guarantee public security and ensure financial well-being.