LID Combined Drainage Infrastructure: Stormwater Management in Indian Cities Using SWMM and BMP Tool

Urbanization is taking place briskly in developing countries such as India due to the increasing population and migration of people to the cities. With the rise in population, the impervious areas in cities are increasing. The increased impervious areas have significantly affected the hydrological characteristics of the watershed in urban areas, resulting in high discharge rates, high volume of runoff, decrease in time of concentration, lower baseflow, and reduced peak time duration. On the other hand, the intensity and frequency of extreme weather events have increased due to the impacts of climate change. All these cause urban flooding issues in cities. Low Impact Development (LID) practices are being implemented to mitigate the adverse effects of urban flooding in various cities worldwide. The present research aims to study the effectiveness of stormwater management where the city infrastructure combines the conventional stormwater network and the LID practices to reduce the impact of flooding in urban areas. The runoff volume for the study area is estimated using the GIS-based Storm Water Management Model (SWMM). The study assesses the flooding in the urban area for storm frequency of 2, 5, and 10 years. The network analysis for rainfall events with these storm frequencies helped to identify 375 junctions prone to a longer duration of flooding. Flooding for a longer duration may cause higher disturbance in the local areas for the social and economic activities and health-related issues post-flooding. Further, the research derives the best suitable locations for LID practices using the United States Environmental Protection Agency’s (USEPA) Best Management Practice (BMP) Siting Tool. The flooding junctions derived from SWMM that overlapped with the BMP siting tool results were selected to propose the LID structures, such as retention ponds, infiltration trenches, and vegetative swales. The LID structures reduced the total runoff volume by 28%, and the total infiltration rate increased by 70%.