Multi-scale characterization of flood risk components: a case study at the municipal level

Abstract

Floods are complex processes that combine local and global factors, causing recurrent and significant human and material losses worldwide. The presented research consists of a multi-scale flood risk assessment process based on data sources collected at distinct scales, expressing hazard, exposure and physical vulnerability of buildings. Detailed Census-derived parameters are essential in representing exposure and vulnerability, while flood hazard is quantified from geomorphologically validated susceptibility maps combined with historical data that characterize events' magnitude and frequency. The results allow a cross-scale analysis of risk, from the building to the municipality level, by identifying exposed populations, buildings, and physical vulnerability. The Lisbon Metropolitan Area is a highly contrasting territory regarding flood risk: some areas are susceptible to slow-onset floods in extensive floodplains but with low exposure, while densely urbanized areas are susceptible to flash floods in small watersheds. While the building level assessment is valuable for local civil protection and urban planning, municipal-level indices provide a comparable inter-municipal perspective of flood risk.