Assessment of Storm Drainage System of Fatullah Union Within DND Project Using SWMM Model

Abstract

The study deals with the assessment of storm drainage system of Fatullah union of Narayanganj district. Now a days in Narayanganj, Fatullah is one of the rapidly expanding business and commercial area. One of the International stadiums of the country is also located in Fatullah. Unfortunately, storm flooding and over topping drainage system problems are occurring at the rainy season in Fatullah Union. In order to generate short duration rainfall data for daily rainfall two different procedures have been applied. These are Hershfield method and an empirical formula deduced by Indian Meteorological Department (IMD). Gumbel Extreme Value (GEV) method used for frequency distribution. Daily Rainfall data were used to develop Intensity-Duration-Frequency curve. Rainfall runoff model named Storm Water Management Model (SWMM5) has been used for the analysis of drainage system under the study. The catchment area covering 1092 ha dividing into 8 sub catchments. All the sub catchments are connected with 8 Junctions which convey runoff through 8 links to 3 outlets. There are six natural channels used as the main canal for conveying runoff water. The surveyed cross-sections of the natural canals of this study area are used in this study. Model calibration and validation were done with the recorded depth at outlet-1 near main discharge canal of Shimrail pumping station. The performance of SWMM5 were evaluated in terms of Coefficient of Determination (R2), The Nash-Sutcliffe coefficient (NSE) and Relative Error (RE). The results from Performance assessment show that R2 = 0.980, NSE= 0.909 and RE= 6% which are within the acceptable limit. Simulation result shows almost all the modeled drainage systems are flooded at J1, J2, J4 and J8 for 2 hr, 6 hr, 12 hr rainfall events for 2 years, 10 years, 25 years, 50 years, 75 years, and 100 years return period. For instance, 12hr-25 years rainfall event 40% of drainage canal and for 12 hr-50 years rainfall event 50% of drainage canal of the study area were flooded. Moreover, for 12hr-25 years rainfall event the total average flow at outlets 6 m3/s and total volume to outfall 259.14 x 103 m3 were occurred from all 8 sub catchments. Carrying capacity of all the canal have been assessed. It is suggested that the capacity of existing canals need to be increased. In addition, regular maintenance and rehabilitation of the canals is a mandatory for smooth flow to reduce any drainage congestion within the study area.