Analysis of urban flooding trend and risk based on rainfall patterns

This study aims to analyze the impact of rainfall pattern changes on urban flooding and drainage system performance and propose appropriate urban flood analysis methods based on the duration and pattern of design rainfall. Inundation simulations were conducted for the northern urban area of Gwangju Stream using PCSWMM. The Huff quartile method was applied to generate design rainfall scenarios with durations of 1~24 hours and return periods of 5~500 years for each quartile. The flood analysis results indicated that for short-duration rainfall events of 3 hours or less, total flooded areas increased as peak rainfall was delayed. For longer-duration events of 6 hours or more, the first-quartile rainfall produced the largest flooded areas. Additionally, the analysis of drainage system performance showed that Number of Surcharged Pipes (NSP) and Length of Surcharged Pipes (LSP) exhibited temporal changes depending on the timing of peak rainfall but had a low correlation with the total flooded area. The hazard risk analysis revealed that, during short-duration rainfall, flood risk areas tended to increase as peak rainfall was delayed, with areas of Low and Significant risk levels showing increased. This study highlights the influence of rainfall patterns on urban flood analysis and proposes appropriate durations and patterns for design rainfall based on the analysis objectives.