Re-estimation of Design Rainfall Under SSP5-8.5 and Implications for Flood Design Standards

Recent extreme rainfall events have revealed the limitations of current disaster prevention design standards, which do not adequately reflect the nonstationarity and frequency of extreme events under climate change. This study applied the SSP5-8.5 climate change scenario to quantitatively assess medium- to long-term rainfall variations and conducted an empirical analysis of the Bubhwa Stream watershed. It included the estimation and validation of design rainfall, intensity-duration-frequency (IDF) curves, and temporal rainfall distributions. The results show that future rainfall will be characterized by a significant increase in both the frequency and intensity of short-duration extreme storms. The design rainfall values based on the climate scenario are approximately 15% higher than those derived from historical observations. These findings highlight the necessity of incorporating nonstationary frequency analyses and temporal disaggregation techniques into flood design practices. By systematizing the design rainfall estimation procedure and providing empirical verification based on various climate scenarios, this study establishes a technical foundation for improving disaster prevention guidelines. The results underscore the academic and practical need to transition from static design standards to dynamic and adaptive design criteria in an era of climate change.