New Perspective on Rainfall Frequency Curves

Depth-duration-frequency (DDF) or intensity-duration-frequency (IDF) curves are developed using a single series of maximum rainfall data for the desired duration from a single station. If these curves are developed using the series for all durations from the same station, in theory they should never intersect. However, during the development of sets of IDF curves for different durations and return periods to develop a rainfall frequency atlas for a region in Venezuela, South America, it was found that these curves often intersected. A technique to generate these curves that would prevent their intersection is proposed. This new method entails the collective examination of all series of extreme rainfall depths, and therefore, guarantees consistent results. This method is able to detect series with insufficient or doubtful measurements through the value of the exponent of an equation that relates rainfall depth and duration, and through the statistics of their series. This method also allows the generation of new DDF and/or IDF curves for a virtual rainfall gauge strategically located in areas under study.