Some remarks on the truncation used in partial flood series models

In the partial duration series approach to the problem of flood analysis, the truncation level above which streamflow is regarded as flood flow plays a key role. In the absence of a systematic and well defined method for selecting such a level in practice, it is desirable to know how different choices effect the obtained results. We base our mathematical investigation on some commonly used partial flood series models to show that once the time‐dependent Poisson process, used in modeling flood frequency is found applicable with a certain truncation level, then it should remain so with any higher truncation level. We also point out that this same property holds true for the exponential distribution widely used in the study of flood magnitude. At the end of our investigation we give a number of remarks on some problems involved in the practical application of partial duration series models.