Propagation of rating curve uncertainty in design flood estimation

Statistical flood frequency analysis is commonly performed based on a set of annual maximumdischarge values which are derived from stage measurements via a stage-discharge rating curve model.Such design flood estimation techniques often ignore the uncertainty in the underlying rating curve model.Using data from eight gauging stations in Norway, we investigate the effect of curve and sample uncertain-ty on design flood estimation by combining results from a Bayesian multisegment rating curve model and aBayesian flood frequency analysis. We find that sample uncertainty is the main contributor to the designflood estimation uncertainty. However, under extrapolation of the rating curve, the uncertainty bounds forboth the rating curve model and the flood frequency analysis are highly skewed and ignoring these featuresmay underestimate the potential risk of flooding. We expect this effect to be even more pronounced in aridand semiarid climates with a higher variability in floods.