Hazards are the key drivers of uncertainties surrounding riverine flood risks

Abstract Flooding drives considerable risks. Designing strategies to manage these risks is complicated by the often-large uncertainty surrounding flood risk projections. Uncertainty surrounding riverine flood risks can stem, for example, from choices regarding boundary conditions, model structures, and parameters as well as interactions among hazards, exposures, and vulnerabilities. A quantitative understanding of which factors drive uncertainties surrounding flood hazards and risks can inform the design of mission-oriented research. Here we analyze a case study to (i) characterize key uncertainties impacting flood risk projections and (ii) characterize the most important drivers of the uncertainties surrounding riverine flood hazards and risks. We find that the projected flood risk is most sensitive to factors associated with flood hazards: upstream discharge, riverbed elevation, channel roughness, and the digital elevation model resolution. Our framework and results can help to improve flood-hazard and risk projections.