Economic assessment of flood damage in South Korea: An object-based comparative study of national and local rivers

Flooding poses an increasing global threat to human settlements, infrastructure, and agricultural areas, particularly under the combined pressures of urbanization and climate change. Accurate estimation of flood-induced economic losses is essential for effective disaster risk reduction and policy planning. This study quantifies the direct flood damage costs across South Korea's five major river basins (Han, Nakdong, Geum, Yeongsan, and Seomjin) by distinguishing between national and local rivers. This differentiation improves the accuracy of flood-induced economic loss assessments. The study introduces an object-based analysis approach that integrates high-resolution spatial and socioeconomic datasets to enhance the precision of regional damage estimation. By minimizing aggregation errors and aligning flood exposure with administrative and land-use boundaries, this method offers clear advantages over conventional grid-based approaches. Our findings reveal significant spatial variations in flood damage costs across river types and land-use categories. Flooding in national rivers predominantly impacts high-density residential and industrial zones, resulting in higher economic losses. Conversely, flooding in local rivers disproportionately affects agricultural areas. While economic losses per unit area may be lower in these regions, widespread inundation significantly disrupts rural economies. The Han and Nakdong River basins record the highest flood damage costs owing to the concentration of high-value assets near major waterways. Meanwhile, the Geum River basin records the most substantial agricultural flood damage. The results underscore the importance of refining flood risk assessment methodologies, considering regional land use. Asset-level damage estimation significantly enhances risk management and lays the foundation for future flood vulnerability assessments and mitigation strategies.