Developing Physical Flood Risk in the face of Climate Change: A Case Study for South Korea and South-Eastern China

The impact of climate change and extreme weather events, such as heatwaves and heavy rainfall, poses a severe environmental crisis, affecting both natural and socioeconomic systems, including governments and businesses. Responding to this, the Task Force on Climate-related Financial Disclosures (TCFD) emphasizes the need for organizations to quantitatively announce their physical risks and opportunities under climate change, highlighting proactive management of their risks. With its seasonal concentrated rainfall and topographical influences, East Asia faces escalating vulnerabilities to droughts and floods. Collaborative disaster response efforts at governmental and corporate levels are crucial. This study focused on the data availability in South Korea and China's southeastern region to develop flood risk models to support reporting by the TCFD. For South Korea, a model was developed by using time-series flood traces from 2006 to 2018 as training data, incorporating monthly maximum consecutive 5-day precipitation, topography, soil, and land cover maps into a random forest model. In China, a model was developed by combining monthly maximum consecutive 5-day precipitation and topographic information. Results highlight flood risks, particularly in South Korea's low-lying agricultural areas and southeastern China's lowland and coastal regions. Both countries experience increased flood risk under SSP1-2.6 and SSP5-8.5 scenarios from 2030s to 2050s, corresponding to rising future maximum rainfall. Given the tendency for floods to persist in previously affected areas, disaster preparedness through predictive measures becomes imperative, shifting the focus from post-disaster recovery to proactive disaster prevention. Additionally, guidelines for government and corporate-level utilization of available data and establishing action priorities in the event of a disaster are necessary.