A new investigationon on the performance of rainfall IDF models

Rainfall intensity at different durations and frequencies (IDF curves) are widely needed in nearly all water projects, e.g., culverts, urban drainage, etc. However, IDF curves are reported at discrete durations and frequencies. To avoid subjective decisions, however, IDF models have been developed and are used universally. In this article, the performance of five commonly used IDF models is analyzed for three synoptic stations in Iran. The results show that there is an overall acceptable performance for all models, as far as the prediction of rainfall intensity from duration and frequency is concerned. However, from a probabilistic point of view, the non-negativity of a cumulative distribution function is not satisfied. Therefore, the non-negativity concept was added as a constraint. Consequently for this case, the performance of the models decreased considerably. It seems that all IDF models currently in use are not efficient, yet more efficient models must be developed to take into account all characteristics of the phenomena.