Quantitative fluvial and coastal flood risk assessments for European coastal cities considering various climate scenarios and ecosystem-based approaches for hazard mitigation

Coastal cities, due to their geographic location, are particularly exposed to hydro-meteorological and climate-related natural hazards. The EU-funded Horizon 2020 project SCORE (Smart Control of the Climate Resilience in European Coastal Cities), within its various activities, aims to provide a better understanding of how to mitigate and manage the effects of extreme events, particularly floods, in European coastal cities. Achieving this objective requires adequate knowledge about the probabilities and potential consequences of flood events based on a probabilistic risk assessment framework encompassing models of flood hazard for different climate scenarios, exposed elements, and vulnerability.

In this context, the present work describes the methodology and presents the results of quantitative risk assessments developed for fluvial and coastal flooding for three of SCORE’s coastal city living labs (CCLLs): Massa (Italy), Oarsoaldea (Spain) and Vilanova i la Geltrú (Spain). The risk assessments cover four types of exposed elements, i.e., population, buildings, roads, and railways, and a number of flood scenarios, both in terms of different climate conditions and considering the absence or presence of ecosystem-based approaches (EBAs) for the mitigation of fluvial flood hazard. This allows understanding both the impact that climate change is expected to have on flood risk in these CCLLs, and the influence that specific EBAs can have in reducing fluvial flood risk from a baseline to an improved infrastructural condition (i.e., residual risk).

The results of the assessments provide invaluable information to support flood risk management activities, such as gridded maps of losses for each hazard scenario and type of exposed element, maps of estimated average annual losses (AAL), and aggregate loss metrics at urban scale. In addition, they serve as input for subsequent tasks of the SCORE project, such as the development of cost-benefit analyses of specific EBA solutions and the development of financial resilience strategies for the flood risk management of the three CCLLs.