Increasing extreme flood risk under future climate change scenarios in South Korea

The endeavor to reduce the multiple risks of climate extremes takes the future of civil society. Many global climate models (GCMs) and regional climate models (RCMs) have been developed to project the future changing climate. To quantitatively evaluate future flood risks, the results of the current hydrological model based on simulated data from the climate model should be analyzed. This paper focuses the connection of technological and policy aspects for the future flood management in South Korea. Accordingly, this study assesses the changes in flood quantiles based on the two representative concentration pathways (RCP4.5 and RCP8.5) scenarios. The HadGEM3-RA regional climate model is used to predict future changes in extreme rainfall events, and the regional quantile delta mapping (RQDM) method is adopted to correct for any inherent bias in the climate models. The climate change scenario is divided into the following four periods: S0 (1976–2005), S1 (2011–2040), S2 (2041–2070), and S3 (2071–2100). A regional frequency analysis (RFA) is applied to estimate the rainfall quantiles as input data in rainfall-runoff model. The flood quantiles are simulated using the HEC-1 (rainfall-runoff) model for historical and future periods, and the variations in the flood quantiles are calculated quantitatively for the five major river basins (Hangang, HAN; Nakdonggang, NAK; Geumgang, GUM; Seomjingang, SJG; Yeongsangang, YSG) in South Korea. As a result, it is found that the highest flood risk can occur in the YSG basin, and the YSG basin should be considered the most urgent and important river basin for climate change adaptation plans compared with other major basins in South Korea.