Damage Mitigation Strategies for Flood-Prone Coastal Areas under Climate Change and Sea Level Rise

Climate change and sea level rise intensify compound flooding in coastal cities through combined storm surges and extreme rainfall, but disaster management systems address these hazards separately. This study quantified the compound flood risks for Busan Metropolitan City as a case study. A coupled ADCIRC–SWAN model simulated coastal inundation under storm-surge and sea-level-rise scenarios, integrated with rainfall-induced urban flooding data. IPCC projections (SSP2-4.5: +58.4 cm; SSP5-8.5: +81.8 cm by 2100) were incorporated into 50-year and 100-year return period analyses. Object-based damage calculations were performed to estimate the economic losses across buildings, vehicles, agricultural assets, and human lives. The results showed that the 100-year compound flooding generates KRW 1,488.4 billion (USD ~1.1 billion)—approximately double that of single-hazard coastal (KRW 752.8 billion) or urban flooding (KRW 729.8 billion) alone. The climate scenarios reveal a dramatic escalation: damage increases by 92.4% and 154.9% under SSP2-4.5 and SSP5-8.5, respectively. Gangseo-gu and Dong-gu face the highest risks, with Gangseo-gu potentially incurring KRW 962 billion under SSP5-8.5. Buildings and vehicles constitute more than 95% of losses. Traditional single-hazard approaches substantially underestimate the risks. Integrated frameworks, targeted adaptation, enhanced drainage, and climate-adaptive codes are essential for coastal resilience.