Modelling of Urban Storm Water Runoff Using SWMM

Abstract

Water logging is one of the major nuisances faced in Dhaka. Moderate to severe rainfall intensity, during the monsoon season, causes severe inundation in the prime locations of the city. The primary causes of water logging are inadequate drainage sections, conventional drainage systems with low capacity and gravity, natural siltation, lack of inlets and outlets, indefinite drainage outlets, improper maintenance of existing drainage systems, and over and above disposal of solid waste into drains and drainage paths. Water logging is also sometimes caused by the topography of the city area. The residents of Dhaka City are burdened by the water logging, which has negative social, physical, economic, and environmental consequences. Urbanization is one of the reasons of increasing impervious area, disturbing the natural catchment and creating a demand for efficient drainage system. Mirpur 10, Begum Rokeya Sarani is one of the areas where flooding in quite inevitable during the rainy season. In this study, the storm water modelling of the mentioned area was conducted involving EPA SWMM and ArcGIS software to access the surface runoff and flooding using IDF curve for different return periods. The rainfall data of Dhaka city from 2010 to 2019 was collected from Bangladesh Meteorological Department (BMD) and the hydraulic data was collected from DWASA. Moreover, node flooding of the existing hydraulic structure, due to severe rainfall events, was also analyzed. To see how far Low Impact development practices could reduce urban flooding, one of them (Rain barrel) was tested on the catchment area, and the node flooding volumes were compared with or without Low Impact Development techniques. The results of the modeling show that there is a significant risk of node flooding, particularly in the event of extreme rainfall. However, after the LIDs were implemented, the flood peak value, surface runoff and flooding were significantly reduced.