Understanding flood risk in urban environments: spatial analysis of building vulnerability and hazard areas in the Lisbon metropolitan area

Abstract

Climate change has brought about new risks while exacerbating existing ones, with floods now accounting for about 45% of global disasters. This trend indicates that the exposure to floods and resulting damages will continue to rise. This paper aims to contribute to the global efforts to enhance flood resilience in urban areas by introducing a physical vulnerability index for buildings in flood-prone urban areas and exploring its connection with flood hazard, as defined by the European Union Directive 2007/60/EC. An index-based methodology is proposed to assess the physical vulnerability of buildings to flooding, utilising the Portuguese Census and Georeferenced Buildings Database, collected on a nationwide scale. The physical vulnerability of buildings is evaluated in the context of the Lisbon metropolitan area (LMA) in Portugal, and the results are compared across different scales, contrasting flood hazard information for the entire LMA with the areas identified under the Flood Directive as having significant potential flood risk. Using cluster analysis, spatial patterns of flood risk are identified, highlighting areas where high flood depth and flood velocity overlap the high vulnerability of buildings. Lastly, potential adaptation paths are discussed, considering the diverse nature of the flood hazard and the lessons learnt from other flood events.