Flood risk assessment of cultural heritage across countries and spatial scales

Floods are a threatening natural hazard for cultural heritage, making flood risk assessments fundamental to develop effective mitigation strategies. The increased accessibility of global and regional flood hazard maps raises the question of whether these maps can accurately assess the flood risk to assets like cultural heritage, represented as discrete points in georeferenced databases with attributes varying by country. This study aims to investigate the feasibility of using large-scale hazard maps to assess flood risk to cultural heritage, evaluating how different spatial resolutions influence the risk assessment, while also developing a standardized methodology for estimating flood risk that can be effectively applied across different countries. To achieve these objectives, the current study conducts a comparative flood risk assessment for cultural heritage in Portugal and in the Po River Basin in Italy. Cultural heritage and hazard maps were integrated in a GIS environment to produce exposure and hazard maps, assessing vulnerability with a vulnerability index and flood risk using a semi-quantitative index-based method. The findings reveal that: (1) global hazard maps have strong limitations to accurately assess risk; (2) continental hazard maps have a better agreement with Floods Directive maps but are sensitive to the area considered; (3) the comparison of risk rankings from various hazard sources shows a low degree of agreement, with notable discrepancies in Po River Basin. This study could support decision-makers in prioritizing cultural heritage that require further investigation and highlights the importance of considering their spatial distribution when producing high-resolution hazard maps.