The effect of certain restrictions imposed on the interarrival times of flood events on the Poisson distribution used for modeling flood counts

In the application of partial duration series models of flood analysis it is occasionally observed that successive exceedances are correlated. To reduce this correlation, some investigators tend to impose certain restrictions on the interarrival times of flood events in order that these events will not occur close together in bunches. We show analytically how such restrictions interfere with the underlying hypotheses of the Poisson process commonly used to model flood counts, and we caution against imposing restrictions that may render this simple and appealing model inapplicable.