Analysis of the Impact of Rainfall in Mountainous Areas of Jeju Island on Stream Flood Discharge

Jeju Island frequently suffers significant damage from streams and inland flooding during extreme rainfall events. However, disaster-prevention performance targets, often set using ASOS data from low-lying coastal areas, fail to adequately reflect regional characteristics. To address this issue, this study categorized Jeju Island into coastal, mid-mountain, and mountainous zones based on elevation and conducted a comparative analysis of probable rainfall amounts for streams across these regions. Additionally, the impact of rainfall was examined by comparing flood volumes between adjacent streams originating from different source locations. The analysis revealed that rainfall amounts exceeded disaster prevention performance targets by 24.4% to 64.0%, with rainfall in mountainous areas having the greatest impact on flood volumes in downstream regions. These findings underscore the importance of developing rational solutions through economic and other evaluations when implementing disaster prevention projects and setting disaster response performance targets.