Towards National Ecosystem Accounting for Flood Regulation: A SEEA-EA Pilot Implementation Supporting Land-Use Policy in South Korea

Climate-driven increases in flood frequency and severity highlight the need to integrate ecosystem services into land-use policy, yet practical methods for including flood regulation in national ecosystem accounts remain limited. This study developed a pilot flood-regulation account under the System of Environmental-Economic Accounting–Ecosystem Accounting (SEEA-EA) for 22 sub-watersheds of the Nakdong River Basin, South Korea, using only national datasets for 2007 and 2022. Ecosystem condition was measured with a curve number (CN)-based rainfall retention ratio. Service flows were estimated by linking Service Providing Areas (SPAs) and Service Demand Areas (SDAs) under 200- and 500-year flood scenarios, and the monetary account separated Expected Annual Damage (EAD), a risk indicator, from avoided damage, the value of the service. Basin-wide condition hardly changed (−0.05%), but the SDA–SPA gap in mean CN widened from 4.76 to 5.48, revealing deterioration in flood-exposed demand areas. EAD remained stable, whereas avoided damage declined by 12.3%, and two sub-watersheds with large providing areas supplied about 65% of the service value. Priority sub-watersheds emerged only where condition, exposure, and value indicators converged. These results support separate reporting of SPA and SDA condition, exposure tables by asset class, and flood maps for more frequent events in Korea’s national ecosystem accounts.