Feasibility of Implementing “Sponge City” Concepts in Gangnam, Seoul, to Mitigate Flood Risk

Urban pluvial flooding, intensified by the climate crisis, poses escalating challenges for cities worldwide. In 2022, Gangnam District in Seoul, South Korea—a high-density, economically critical area—suffered catastrophic flooding, particularly between Gangnam Station and Seocho 2-dong. Contributing factors included low-lying topography, outdated drainage systems, and insufficient green infrastructure. To address these vulnerabilities, reliance on traditional grey infrastructure must shift toward integrated nature-based solutions, such as those advocated by the Sponge City model pioneered in China. This study analyzes the Gangnam and Seocho-Gu districts to identify the most influential variables driving flood risk and to strengthen predictive modeling for future events. A public survey of Seoul residents further informs local perceptions and priorities for urban flood mitigation.

This is the final presentation for the URSP program, which is the feasibility of implementing a sponge city concept in Gangnam, Seoul to mitigate flood risk. I’m Dayeon Shin, majoring in global affairs and this research is supported by professor Dakota McCarty from the department of environmental science and policy. Before I go through my research results, I want to give the background of this research briefly. In 2022, Gangnam district, which is a highly and economically developed area, experienced massive urban floods. The primary reasons pointed out lack of green spaces, outdated drainage infrastructure, and low-lying geographical features. To resolve this problem, the Sponge City concept can apply to mitigate urban flooding by expanding the green spaces. The sponge city is based on the nature based system to mitigate runoff water in highly developed cities and it is initiated from China.
I used the quantitative research method, which is public survey and data analysis, SHAP value identifying the most influential variables causing urban floods and collecting Seoul residents’ opinions.
So, in the results for the SHAP value, how the geographical elements affect the urban floods, so we can predict the urban flood based on the high influential elements rank. First is building_count, which is the most influential element with the high number of buildings affected by urban floods in the research areas. The second is the distance of road and river, which indicates that the more far from the road and river, it has less vulnerability in urban flood due to the aging or insufficient drainage systems, which means traditional draining focused on the fast draining. The downstream and NDBI which indicates the grey infrastructure were the following influential elements.
Next is the result for public acceptance from the survey. Over 50% of people do not believe Seoul’s current flood management strategies are effective, and do not trust local government authorities to effectively manage flood risks and people think that the Gangnam district office’s role is the most crucial. Additionally, through the survey, insufficient drainage systems, lack of green spaces, and inefficient urban planning were selected as top 3 challenges in the current flood management policy. Furthermore, the poor coordination among government agencies would be the main barrier.
In conclusion, making balance between green and grey infrastructure is a crucial solution and based on the former environmental policy development of Seoul, enforcement will be needed in making certain spaces for green in the building and parklet or using Chicago green alley as a green infrastructure can be applied as solutions to prevent it. No enforcement in constructing green spaces, no gangnam residents future safety.
These are my references, it was an honor to have this opportunity and thanks to huge support by Prof. McCarty, I hope this research contributes to the future flood prevention in Gangnam, Seoul.