Regionalization of Updated IDF Curves for Romania and the Consequences of Climate Change on Sub-Daily Rainfall

IDF curves are widely used to develop the design storm and usually remain in use for long periods of time. However, continuous data collection and the addition of new monitoring stations require updates to the existing curves. In Romania, current prac-tice is still based on curves established in 1973. Climate change significantly alters the frequency and mostly the intensity of extreme rainfall events, justifying the need to update the IDF curves. In addition to using recent observations, updating these curves is essential to support the adaptation of infrastructure to changing climatic conditions. This study analyzed the IDF curves from 68 meteorological stations using data records from the last 30 years. Different approaches were analyzed to obtain a new regionalization, including clus-tering, geographic proximity, or hourly precipitation isolines for a frequency of 1:10. Using rasterized regional rainfall data obtained based on the 1973 and 2025 IDF curves, percentage precipitation differences were calculated. The results indicate that the value of short-term precipitation (5’, 10’, 30’) increased in most of Romania, while long-term events (3 h, 6 h, 12 h or 24 h) largely recorded a decrease in precipitation value in many areas. The increase in short-term torrential rainfall highlights the need for active prevention and management of urban flash floods.