Hydrologic impact on change in land use/land cover in an urbanizing catchment of Mumbai: a case study

Abstract

In this paper, an integrated model has been applied to study the hydrologic impact of changing land use in Poisar watershed of Mumbai, India. In this study, overland flow has been modelled using 1-D mass balance approach, the infiltration using Green-Ampt equations and the channel flow using 1-D diffusion wave equation. The land use/land cover maps from the satellite imageries for 1972, 1992 and 2009 indicated that the impervious area increased by 116% between 1972 and 2009. The hydrologic impact studies for few rainfall events showed increase in peak discharge between 7 and 30%, decrease in time to peak discharge between 0 and 4% and increase in surface runoff between 14 and 48%, between 1972 and 2009. The hydrologic impact for rainfall with return periods of 25, 50 and 100 years indicated that the peak discharge increased between 6 and 9%; time to peak discharge reduced between 0 and 2% while the surface runoff increased between 11 and 16%. The results indicate that the hydrologic impact of urbanization on this catchment is more visible for low and medium rainfall events than for high and extreme events for the catchment.