Simulation of Flow in Open & Closed Conduits by EPA-SWMM Model (Case Study: Babolsar Urban Watershed)

Because of urban rapid growth of Iran, some problems such as propagation of environmental pollutions, urban inundation and flood hazards due to lack of appropriate drainage systems and irregularity of conduits & streams are the major difficulties in urban watersheds. Because of hydrological & hydraulic processes complexities in urban area, using of computer models would be effective. In this study, EPA-SWMM model applied for quantitative simulation of flash flood in some parts of Babolsar urban watershed.12 hour's simulation was done for 2 hours design storm with 2, 5 and 10 years return periods. Quantities simulation results shows that among the 259 junctions in the drainage network of study area, 32, 57 and 60 junctions for 2, 5 and 10 years return periods were inundated respectively. Peak discharges for 10 junctions of study area drainage network, estimated by rational method compared with simulated ones shows good linear correlation. Field investigations, Elevation maps of conduits and conducted simulation implies that the main reasons of inundation are small cross section area of conduits and also low bed slope & invert slope in some places. Conformity of flooded junction's simulation results due to rainfall with historical events in study area verifies the model simulations.