Semi-distributed modelling of stormwater drains using integrated hydrodynamic EPA-SWM model

Abstract

After becoming a capital city of Chhattisgarh state in 2001, the city Raipur in India has been rapidly growing in terms of population as well as areal expansion. With the process of urbanization and alteration of the natural drainage system, the existing stormwater drainage system became insufficient to drain the area, resulting in a higher risk of flooding. In this study, the effect of urbanization on the runoff generation and peak flow and their impact on the stormwater drainage system have been investigated. Digital land-use data from aerial photograph, satellite images and Differential Global Positioning System (DGPS) survey were used to detect and analyse the shift in land-uses since the evolution of Raipur city. For the same periods, total generated runoff and peak flow as well as flood-prone locations along the drainage network have been simulated. The results showed an increase in build-up area of 99.2, 22.0 and 0.6%, respectively. Agricultural areas increased by 210.8, 157.5 and 0.6%, respectively. Forests and tree covers almost completely disappeared. The higher share of build-up areas led to an increase in total runoff generation and peak flows. The maximum runoff increased by 87.92×106L and maximum peak flows changed from 11.03 to 14.09m3/s. The results show significant increase in runoff and peak discharge in the study area due to human intervention, since Raipur city started altering natural drainage system. Moreover, the model can be used for future flood forecasting in Raipur city, and the results from this study can be utilized to develop flood mitigation measured as best management practices in Raipur.