Projecting Depth-Duration-Frequency Curves for Future Climate: a Case Study in the Mediterranean Area

Depth-Duration-Frequency (DDF) curves are an essential tool in hydrological planning and risk management. However, the assumption of stationarity that is traditionally embedded in their derivation, is increasingly questioned by the impacts of climate change. This study focuses on adapting and projecting DDF curves for Sicily (Italy), which is experiencing an intensification of rainfall extremes, particularly for shorter durations. The proposed framework adapts the most up-to-date regional frequency analysis for the island by using an adaptation factor that incorporates the thermodynamic relationship between extreme precipitation and temperature, as well as future climate projections for temperature from an ensemble of regional climate models under the worst-case scenario. By the end of the century, the design rainfall estimates may require to be increased up to 50%, especially for hourly durations, to account for climate change effects. The results also highlight a strong spatial variability in the precipitation quantiles, with higher values observed in specific areas such as the north-eastern part of the island, which is characterized by small catchments and particularly prone to flash floods. Finally, this study provides a simple but still physical-based approach to updating DDF curves, that can be useful for engineers and practitioners, enhancing international efforts to mitigate climate change impacts through improved hydrological planning.