A GIS–MCDM–Based Framework for Flood Risk Scenario in Central Lisbon

Historical cities are particularly vulnerable to natural hazards due to their structural characteristics as well as their social and cultural value. This is especially true for flood hazards, which are expected to become more severe in the future. The current study assesses the flood losses of 315 URM buildings in Lisbon’s downtown under different pluvial flood return periods (i.e. 2–5-10–20-50–100-500-year). Through a collaboration with the Municipality of Lisbon, a database of the assets exposed to risk was developed, by combining indirect resources, such as literature review, remote sensing, historical documentation, and census data, with an external building survey. The hydrologic-hydraulic model was accurately developed in HEC-RAS software to assess the bi-dimensional flood propagation and estimate the water depth hazard on each building. A site-specific typological stage-damage curve was derived for the simulated scenarios by assessing the vulnerability index for each building using AHP and TOPSIS methodologies. The findings indicate that 1) multi-criteria methods for evaluating the vulnerability index can be successfully applied in various contexts; 2) the stage-damage curve derived represents the first attempt to develop damage functions for pluvial flood in Portugal; and 3) estimated flood losses could aid with the risk-reduction and prevention strategies.