Uncertainty assessment of regionalized flood frequency estimates

A simplified approach is presented to uncertainty assessment of regionalize d flood frequency estimation by the generalized extreme value distribution. First, an approximate formulation of the variance of quantile estimators i s introduced to evaluate the confidence limits of the estimated growth curv e of regionalized flood flows. Then this result is combined with the varian ce of index flood estimators to obtain an uncertainty model for evaluating the variance of flood estimators by the index flood method. This approach i s finally used to introduce an efficiency index to discriminate between sin gle-site analysis and the index flood method. Examples of application to no rthwestern Italy are reported and discussed.