Integrated Effectiveness Analysis of Structural and Non-Structural Flood-Mitigation Measures in Jung-gu, Ulsan Metropolitan City

The effects of combined structural and nonstructural measures in reducing urban flood damage in the Taehwa District, Jung-gu, Ulsan Metropolitan City, South Korea, were analyzed using the storm water management model (SWMM). Sixteen scenarios combining structural measures, such as drainage pump stations and high-altitude drainage tunnels, with nonstructural measures, including low impact development (LID) facilities (planter box, bioretention, permeable pavement, vegetative swale, infiltration channel, infiltration chamber) and detention facilities, were simulated using rainfall data from Typhoon Chaba in 2016. Analysis results revealed that scenarios incorporating structural measures significantly reduced inundation area and water levels, with some combinations reducing the flooded area by more than 50％. In contrast, the flood-reduction effects of LID measures alone were minimal, demonstrating virtually no impact during the extreme rainfall event. LID facilities contributed to improving water circulation by absorbing the initial rainfall into the subsurface. This study concluded that structural measures, such as drainage pump stations and high-altitude drainage tunnels, are essential for large-scale flood response, while the concurrent implementation of non-structural measures, such as LID facilities and detention basins, can provide additional flood reduction and water circulation improvement effects.