Comparison between different Intensities of Rainfall to identify overflow points in a combined sewer system using Storm Water Management Model

Abstract

<abstract> <p>Increasing urbanization related to land pressure and the soil arising from it are aggravating factors of flood risk in urban areas, including storm water runoff. Therefore, urban sanitation networks face an excess of water that exceeds their absorption capacity. This article deals with the effect of impermeability in densely populated urban areas and the function of a combined sewer system under higher rainfall intensities using the Storm Water Management Model (SWMM). The objective is to simulate a possible increase in rainfall intensities for reducing overflow points in the combined sewage system at the study area, which was the city of Ahmed Rachdi, Mila in Algeria. The excessive rainfall intensities were modeled using the SWMM software program to estimate maximum water volumes inside the combined sewage system of the study area. To evaluate the model's performance, a comparison process was used between the values of the flow rates of the pipelines of the sewerage system combined with the design flow rates in the current state and the flow rates of a single modeling of future events available during the study interval. The comparison results showed a good and convergent performance for these models. The results of the flooding volumes using different values of rainfall intensities and different return periods, which were 2, 5, 10 and 25 years, in the modeling of the combined sewage system are 3626, 6888, 8636 and 12676m<sup>3</sup>, respectively. The suggested scenario included increasing diameters of some pipes in the combined sewage system pipelines. The results using this scenario showed reductions in the total percentage of overflow points from the integrated sewage system of 52.42%, 40.63%, 31.83% and 20.51% using the rainfall intensities for the return periods of 2, 5, 10 and 25 years, respectively. The present study can provide technical support for using software in the planning, controlling and tests of the sewer systems, which contribute to solving the sewer systems' problems.</p> </abstract>