Analysis of Storm Sewer Discharge Capacity of Urban Watershed using MOUSE Model

Following recent abnormal patterns of climate, strong rainfall exceeding the recurrence interval of the pipeline is causing frequent flooding in urban areas. To reinforce its flood control capacity and deal with climate change, Seoul Metropolitan City has raised the sewer recurrence interval of the Basic Plan for Organizing Sewage to 10 years for branch pipelines and 30 years for trunk pipelines. To review storm sewer capacity following the raising of probable frequency, this study selected the redevelopment area of Godeok3 District, Seoul, as the subject area to collect data on the sewer and watershed status. Then, using the MOUSE model to analyze sewers, the study conducted a numerical simulation. Taking the flood level (18.2m) of Godeok Stream's designed frequency (30 years) as suggested by the Basic Plan for Organizing Five Streams including Banpo Stream as the benchmark, a numerical analysis was conducted using the probable rainfall of Seoul in a 10-year frequency (designed frequency for the sewer) and a 30-year frequency (adjusted frequency). The results showed that pipelines located at the outlet were influenced by downstream backwater to mostly show full-pipe condition. Especially in the 30-year frequency, the scope of full-pipe condition seemed larger. In principle, sewer capacity requires some margin. Even if flooding does not occur on the ground, sections showing full-pipe condition exceeding a certain in-pipe level should be considered for sewer extension or improvement. To secure margin for sewer sections where full-pipe condition occurred, this study suggests extending the sewer.