A derived flood frequency distribution for correlated rainfall intensity and duration

A derived hood frequency distribution (DFFD) combines a stochastic rainfall model with a deterministic rainfall-runoff model to obtain a physically ba sed probability distribution of flood discharges. Previous DFFD studies hav e either assumed that rainfall intensity and duration an independent or neg atively correlated. This study is more general than previous studies becaus e it accommodates both positive and negative correlations between rainfall intensity and duration. Rainfall-runoff processes are modeled using a phi-i ndex infiltration model and a geomorphoclimatic instantaneous unit hydrogra ph. Applications to four Indian watersheds and one US watershed demonstrate s that (1) the correlation of rainfall intensity and duration has an import ant impact on the DFFD and (2) the DFFD provides a potentially useful alter native for estimating hood flow quantiles at ungaged sites. (C) 2000 Elsevi er Science B.V. All rights reserved.