During design studies of the hydraulic structures to be built at the large and important basins like Çoruh Basin, knowing the discharges at the various return periods constitutes important stages of the projects. However, number and the data length of the flow observation stations installed at these large basins are not sufficient. In such cases, importance of regional frequency analysis becomes evident. In this study, regional frequency analysis of the Çoruh basin has been carried out by a new method, L-moments method.
First of all, Çoruh basin has been reviewed as a whole. However, by defining the basin being heterogeneous as a whole, it has been divided in four areas. Firstly, at-site and regional L-moments coefficient of these areas are obtained. Afterwards, based on the discordance test conducted for each area, it is noted that all stations are suitable. Homogeneousness of the areas is defined by heterogeneous test. With the goodness-of-fit test, Pearson Type III for Upper and Lower Çoruh Basins, Extreme Value for Yusufeli area and Logistic value distribution for Oltu Creek area are found to be most suitable distributions. By using these distributions for each area, quantiles are calculated as per various return periods and confirmation of these quantiles values are defined by Monte Carlo simulation.
Key Words : Çoruh Basin, Regional Frequency Analysis, L-moment, Heterogeneity Test, Goodness-Of-Fit Test, Quantile