Non-stationarity assessment of intensity-duration-frequency (IDF) curves of standard duration rainfall in the Eastern Black Sea Region, Türkiye

Intensity-Duration-Frequency (IDF) curves used in the design of hydraulic structures are traditionally based on stationary frequency analyses with fixed parameters. However, temporal changes in extreme rainfall caused by climate change have made the validity of the stationary approach questionable. Recent studies have focused on updating IDFs under non-stationary conditions to understand the time-varying behaviour of extreme rainfall better. In this context, this study, which aims to examine the hydrological impacts of climate change in the Eastern Black Sea region, estimated IDF curves by performing non-stationary frequency analysis for six stations. Both stationary and non-stationary models of the generalized extreme value (GEV) distribution were used to determine extreme rainfall intensities, and the results of both models were compared in terms of the effects of non stationarity on infrastructure design. It was concluded that the stationarity assumption is still valid in stations such as Akçaabat, Giresun, and Ordu. At the same time, the effects of non-stationarity are evident in Bayburt, Gümüşhane, and Hopa stations.