Flood simulation using EPA SWMM 5.1 on small catchment urban drainage system

Water Resource Engineering, Civil Engineering Department, Andalas University, 25163 Padang, Indonesia

^* Corresponding author: junaidi@eng.unand.ac.id

Abstract

The area around Sungai Sapih District Hospital of Padang is often flooded. The existing drainage system inadequate to accommodate the increasing of drainage loads due to the changing land use in the area. In order to evaluate the drainage system in the study area, EPA SWMM version 5.1 was used to develop the simulation model. This model was able to calculate the quantity and quality of surface runoff from each catchment area, flow discharge, flow depth, and water quality in each pipeline and drainage channel during the simulation period. The data used in this research are maps of land use, rain data, and drainage channel dimensions. Hourly time series rain data was used and as this was not directly unavailable at the train station at the study site, it was calculated by constructing a rain estimation hyetograph from the 5-year Intensity-Duration-Frequency (IDF) curve using the Alternating Block Method (ABM). After all EPA SWMM 5.1 parameters were specified and inputted, simulation with four simulation scenarios was performed based on the present and the future possible land use and the change of dimension and shape of the drainage channel. The first scenario produced 18 flooding occurrences, the second; 20, the third and fourth; 14. Of note were the 14 flooding points in the third and fourth scenario despite the shape and dimension of the drain used being in accordance with the detail of drainage planning of Sungai Sapih area according to the city master plan for 2010-2030. This shows that the drainage planning design (DED) for Sungai Sapih District Public Hospital is insufficient to contain the drainage load of the area, either now or in the future.