Distribution‐free methods for estimating flood and streamflow exceedance probabilities by correlation

This paper deals with the problem in which it is necessary to infer the probabilistic characteristics of a streamflow variable y t (e.g., annual peak discharge, or accumulated streamflow during some time interval) given a correlated longer record x t (e.g., annual peak discharge at a gaging site with longer record; rainfall during the same time interval). In particular, it is necessary to estimate probabilities of the form P ( y ≥ y 0 ) for given Y 0 . Conventional methods make assumptions about the joint probability distribution of x t and y t ; the methods developed in this paper require no such assumption, being distribution free. Estimates of P ( y ≥ Y 0 ) are also obtained by Bayesian methods.