Implementation of the EPA-SWMM Model for urban areas with complex geomorphologic characteristics for flash flood analysis

Urban development typically causes alterations in the hydrological cycle evidenced in increased runoff and reduced time peaks. With excessive urbanization, the retaining and buffering developed by the soil and vegetation is lost. Consequently, the increase in runoff generated by impermeable surfaces causes dangerous floods. The Aburrá River watershed is a highly urbanized area located in the Colombian Andes, characterized by complex mountainous terrain and extreme hydrometeorological events. The geomorphological features of the watersheds draining into Medellín River, the spatiotemporal structure of rainfall, soil type and use and the antecedent moisture condition trigger flash flood occurrence that in some cases collapse the drainage system of the city. As a contribution to the knowledge of this type of complex basins, the Area Metropolitana del Valle de Aburrá through his science and technology project (SIATA) implemented EPA-SWMM model for 6 critical basins (high slope and urban coverage) with drainage areas between 3 and 25 km2. In Aburrá valley an effort has been made for real-time monitoring; meteorological radar, rain gauges, water level sensors in both natural channels and nodes of the drainage network. This data has been used for the calibration of the EPA-SWMM. The input model file is generated defining surface properties, slope, roughness, soil class, and topology of the drainage network such as connectivity of nodes and pipes and discharges in the natural network. This research shows the applications in the study basins for some critical events in a resolution of five minutes. The calibrated parameters are Manning coefficient for impervious and previous areas and the depression storage. The calibrated model was able to predict the observed outputs with reasonable accuracy. This study provides support for planning, analysis and control strategies for minimizing sewer overflows.