Modelling of short-duration rainfall intensity equations for the agean region of turkey

The aim of this study is to develop a rainfall intensity-duration-frequency (IDF) equation for the six rainfall stations in the Agean region of Turkey. The records of the observed maximum annual rainfall values were statistically analyzed for rainfall durations of 5, 10, 15, 30, and 60 min during the period 1938-2000. The maxima have been fitted to the Generalized Extreme Values (GEV), Gumbel, Normal, two-parameter Lognormal, three-parameter Lognormal, Gamma, Pearson III, and Log-Pearson type III distributions, and X goodness-of-fit tests were used to choose the best statistical distribution among them. The parameters of the IDF equations and coefficient of correlation for different return periods (2, 5, 10, 25, 50, 100 and 500 years) are calculated by using a nonlinear estimation method. The IDF equations i(max) (t) = Al(t + C)B for T <= 550 years and i(max)=Al(1+Bt)(c) for T >50 years were chosen, because they possessed the largest correlation coefficients.