Estimating the upper tail of flood frequency distributions

Procedures for estimating recurrence intervals of extreme floods are developed. Estimation procedures proposed in this paper differ from standard procedures in that only the largest 10–20% of flood peaks are explicitly used to estimate flood quantiles. Quantile estimation procedures are developed for both annual peak and seasonal flood frequency distributions. The underlying model of flood peaks is a marked point process , where represents time of occurrence of the jth flood during year i and the mark represents magnitude of the flood peak. Results from extreme value theory are used to parameterize the upper tail of flood peak distributions. Quantile estimation procedures are applied to the 92‐year record of flood peaks from the Potomac River. Results suggest that Potomac flood peaks are bounded above. The estimated upper bound is only 20% larger than the flood of record.