Extracting the Intensity - Duration - Frequency Curves with Daily Precipitation Data Using Fractal Theory

The intensity – duration – frequency (IDF) curves play most important role in the hydraulic design of structures. The traditional method to construct IDF curves has a long estimation process and also has high number of parameters which this property reduces the reliability of IDF curves. In the traditional method، rainfall in different durations should be available until the extraction of IDF curves are be possible. Whereas in many regions only 24-hour precipitation statistics are available which with this data the extraction of IDF curves using common methods are not possible. In this paper، fractal theory has been used to remove these problems and IDF curves are made with maximum annual daily rainfall data. The applied method in comparison with conventional method is less computational steps and its number of parameters is much lower that this property increases the reliability of IDF curves. Fractal and traditional methods were used to extract the IDF curves at Tangheie Panj rainfall station and the results shown that a fractal method with daily precipitation data clearly able to extract the IDF curves.