Applicability Analysis of Trunk Drainage Sewer System for Reduction of Inundation in Urban Dense Areas

Urban development naturally aggravates flood damage, causing severe damage yearly. Preparation for flood damage is a part of urban planning, but it is not easy to establish clear mitigation measures in densely populated urban areas. This study analyzed the applicability of trunk drainage sewers as an alternative to installing abatement facilities, a typical structural measure for reducing flood damage in dense urban areas. The study areas included three areas in South Korea where flood damage had previously occurred, and the input parameters of the flood analysis model were calibrated based on the measured runoff, followed by testing with inundation traces. The results of three watersheds were qualitatively evaluated using the Lee Sallee Shape Index (LSSI) method. The applicability of the trunk drainage sewer system in the Gunja and Dowon watersheds were “Excellent” and “Good” in the Dorim watershed. The analysis results for each trunk drainage sewer condition indicated that the peak flow reduction was the greatest at 40% and 60% dimensionless upstream area ratio (DUAR) for 1000–5000 m3 and 10,000 m3, respectively. High hydrological applicability under the same rainfall conditions was demonstrated consequent to analyzing the applicability of the installation of a typical reduction facility and trunk drainage sewer.