Probabilistic Assessment of Pluvial Flood Risk Across 20 European Cities: A Demonstrator of the Copernicus Disaster Risk Reduction Service for Pluvial Flood Risk in Urban Areas

Pluvial flooding is a major concern in urban environments with limited or temporarily reduced efficiency of surface drainage. Climate change, land use change, and increased exposure in hazard prone areas play a role in increasing pluvial flood risks. We describe a methodology for rapid probabilistic pluvial flood hazard mapping and risk assessments in urban environments developed for the Copernicus Climate Change Service "Pluvial Flood Risk Assessment in Urban Areas" demonstrator project for large computational domains. The methodology is designed to be flexible and robust enough to be adapted to other cities in Europe and elsewhere, and is composed of three main steps: (i) computation of the intensity-frequency relationship to express the depth of extreme hourly rainfall events at the urban scale; (ii) characterization of the pluvial flood hazard by means of raster-based flood modeling, and; (iii) estimation of the direct tangible damages at the building level for residential, commercial, and industrial buildings. Methods are tested for 20 cities across Europe and considering two infiltration rate scenarios. Spatial-explicit results at the urban-scale highlight the neighborhoods and sub-urban areas more adversely affected in terms of direct tangible damage to buildings and assets. Probabilistic risk assessment results indicate that Brussels, Antwerp, and London are the cities with higher expected annual damages per built-up area among the 20 cities considered in this study. These results can be useful for supporting the implementation of the Sendai Framework for DRR 2015-2030, for developing multi-hazard risk assessments, and for supporting the development of national climate change adaptation plans.