Estimating IDF based on daily precipitation using temporal scale model

The intensity –duration –frequency (IDF) curves play most important role in watershed management, flood control and hydraulic design of structures. Conventional method for calculating the IDF curves needs hourly rainfall data in different durations which is not extensively available in many regions. Instead 24-hour precipitation statistics were measured in most rain-gauge stations. In this study, scaling properties of extreme rainfall are examined to derive scaling IDF curves over different durations. This new method in comparison with traditional method is less computational steps and has lower parameters numbers which causes increasing in reliability of IDF curves. Scaling method was used to extract the IDF curves in Ahwaz rain-gauge station and results proved the efficiency and robustness of the scaling method. The accuracy of scale model method for Determining precipitation intensity, with Duration 30 to 180 minuts in Ahwaz station, is quite acceptable and maximum error is about 11.5%.