Projected flood hazards and risks are often highly uncertain. Uncertainty surrounding flood hazards can stem, for example, from choices regarding boundary conditions, model structures, and parameters. Dynamic interactions among hazard, exposure, and vulnerability can modulate the uncertainty surrounding flood risks. A quantitative understanding of which factors drive uncertainties surrounding flood hazards and risks can inform the design of mission-oriented research. We apply a global sensitivity analysis to characterize the most important drivers of the uncertainties surrounding flood-hazards and risks. We discuss the impacts of shifting from a hazard to a risk perspective on the design of research strategies.