Evaluation of short term rainfall analysis methods (Case Study: Shahrekord station)

Determination of maximum rivers flow resulted from surface runoff in watersheds without adequate hydrometric records is based on rainfall-runoff models. The short duration rainfalls are one of the basic elements to apply these models. The access to quantitative and intrinsic worth storm data is restricted around the word and in Iran too. There are several empirical and statistical methods to estimate short duration rainfalls based on more common rainfall records such as daily and monthly precipitations. In this study the recorded rainfall hyetographs on Shahrekord station within Chaharmahal va Bakhtiari province were used to evaluate the suggested regional equations and SCS recommended curves containing ratios of short duration rainfall and 24 hours of maximum rainfall. The results showed that short rainfalls should be over estimated by both SCS curves and regional empirical equations. Although as the ratios method is easier to use, the SCS curves can be modified for each region by available storm data and used as an acceptable method.  Results also showed that in order to apply  Ghahraman-Abkhazar relationship for Shahrekord region, this relationship should be multipled by a correction coefficient of 0.7136. Finally a new logarithmic relationship was developed for estimating of the IDF for Shahrekord station.