Flood frequency analysis of the Rasina River in Serbia

In this paper we performed flood frequency analysis by using L-moments and annual maximum series data from two hydrological stations on the Rasina River (Brus and Bivolje), for the 1961−2020 period. Homogeneity testing confirmed that the basin can be considered hydrologically homogeneous ( V i = 0.38 < 1). Five probability distributions – Normal, Log-Normal, Gumbel, Pearson Type III, and Log-Pearson Type III – were tested to identify the best-fit model. An L-moment ratio diagram and Z -statistics indicate that all distributions satisfy the test criteria, with Log-Pearson Type III showing the best overall fit for the region ( Z = 0.09). Goodness-of-fit tests (Kolmogorov-Smirnov, Cramér-von Mises, and χ 2 ) confirmed Log-Pearson Type III as the best fit at the Brus station and Pearson Type III at the Bivolje station. Theoretical flood quantiles were calculated for various return periods (T-year floods). Mann–Kendall trend analysis indicated a significant decreasing discharge trend at Bivolje (−1.28 m 3 /s per year).