The safety issue of underground basement homes has once again emerged as a policy concern due to record-breaking heavy rains and flooding in the Central Region of Korea, including Seoul, on Aug. 8-9, 2022. As of Dec. 31, 2021, estimated number of basement homes in Seoul was 202,741, accounting for about 5% of all households.

If too much rain occurs in a short period of time, flood prevention facilities such as sewage and pump stations have will limitations in preventing flooding. This is the reason why flooding damage occurs repeatedly. For example, the maximum rainfall per hour of the Aug. 8-9, 2022 heavy rain was 141.5 mm, far exceeding the Seoul Metropolitan Government's standard for flood prevention performance of drainage facility systems at 95 mm per hour. This suggests that small-scale and distributed measures such as flood barrier facilities, building maintenance and emergency responses are additionally needed to cope with residual risks because not all rainfall can be prevented by large-scale drainage facilities of the public.

The most fundamental way to prevent flood risk of underground basement homes is to eliminate the construction and use of basement homes. However, it is impossible in a short period of time. In addition, it might have greater side effects. While basement homes with poor environments are vulnerable to disasters, they are products of the overwhelming market reality where low-income households have no choice but to find such low-quality but affordable residential opportunities due to high housing costs in Seoul. Therefore, a careful and incremental approach is needed to expand affordable housing opportunities while addressing flood risk.
The purpose of this study was to identify the current status, distribution and flood risk characteristics of underground basement homes scattered in Seoul and to derive policy directions of resolving flood risk by type according to physical characteristics such as flood risk, building aging and infrastructure (road) conditions. In particular, this study focuses on flood risk issues due to physical characteristics (building and infrastructure conditions) rather than residents (tenants).