When People Meet Floods: Time‐Varying Population Exposure to Urban Pluvial Flooding in Rome, Italy

ABSTRACT Urban pluvial flooding (UPF) poses a growing threat in highly urbanized areas, where rainfall intensity, topography, and human activities interact, amplifying flood risk. This study develops dynamic population impact maps for the Northern Tiber District of Metropolitan Rome (Italy) by integrating flood hazard, population vulnerability, and time‐varying population exposure into a unified risk framework. Hazard is assessed using a surface‐only, two‐dimensional (2D) rain‐on‐grid hydraulic model under a conservative worst‐case scenario where drainage capacity is exceeded. A coping capacity exceedance curve is used as a proxy for population vulnerability and is combined with a time‐varying occupancy score and the hazard to produce a dynamic scenario‐based risk and estimate the population at risk within flood‐affected buildings. Exposure analysis reveals marked spatiotemporal variability, with residential buildings dominating baseline exposure while event‐driven peaks occur in recreational and sporting facilities. The resulting dynamic risk maps demonstrate that mass gatherings are key drivers of flood risk, as they amplify existing spatial disparities in exposure, resulting in pronounced and localized peaks of high risk in affected areas. These findings emphasize the need for contingency planning and targeted emergency management, particularly during major cultural and sporting events.