The aim of this paper is to evaluate a precise intensity–duration–frequency (IDF) relation for a small catchment area which is situated at the north part of Graz in Austria. In order to determine the probability of occurrence of any rainfall event, the frequency distribution, which can fit past characteristics on the magnitude and the probability of occurrence of such rainfalls, should be known. In this paper, in order to find the best–fit probability distribution model, some parameter estimation techniques such as L–moments and maximum likelihood models were used and for goodness of fit test, three methods were used as chi–square, Kolmogorov–Smirnov and the root mean square error (RMSE). In this paper, a comparison between four commonly used rainfall frequency distributions were carried out such as generalised extreme value (GEV), Gumbel, log–Pearson type 3 (LP3) and three–parameter log–normal (LN3). Finally, using the best–fit probability distribution, the IDF for this catchment area using a simple graphical method was determined.
Keywords: probability distribution, L–moments, maximum likelihood method, Sherman equation, intensity–duration–frequency, IDF, Austria, rainfall events, rainfall frequency distribution