Assessing the spatiotemporal impact of users’ exposure and vulnerability to flood risk in urban built environments

Flood risk in an urban built environment depends on the combination of the hazard, the vulnerability of the built environment itself and its infrastructure (referred to as physical vulnerability), and the exposure and vulnerability of the people residing, working or visiting it (i.e., their human condition). However, factors affecting those people vary over space and time depending on the uses of the built environment. This research offers a methodology for combined spatiotemporal flood risk assessment, providing hourly variations in risks due to hazard, physical vulnerability, users’ exposure, and vulnerability. A mesoscale approach is adopted by collecting and managing data for each open space in the urban layout (e.g., street, square) and the facing buildings. In particular, users’ exposure and vulnerability are investigated for indoor and outdoor uses and their temporalities, providing hourly distributions of users’ density, age, familiarity with the built environment, and direct exposure to the floodwaters. Then, the Analytical Hierarchy process is used to combine risk factors. Finally, the application to a case study application (an urban district in Guimarães, Portugal) demonstrates how users’ factors alter the risk over the day within the same mesoscale element and considers different elements which share the same hazard and physical vulnerability.