An assessment of hydrological impacts due to changes in the urban sprawl in Bhopal city and its peripheral urban- rural fringe

Abstract

Bhopal district has been developing at a very fast pace with most of the developmental activities being concentrated in the Bhopal city and along its periphery mostly comprising of the urban-rural fringe areas. This has resulted in considerable changes in the land use in the city and its fringes, with substantial areas being converted to semi-pervious and impervious zones owing to the fast pace of urbanization. These drastic changes in the land use pattern, has to a large extent changed the hydrology and drainage aspects of the city. Owing to the changes in the land use and pressures of increasing population, the runoff and drainage aspects have also been altered to some extent. Nowadays it is very common to find large stretches of roads being submerged during small rainfall events, thereby causing hardships to the local population. An effort has therefore been made to identify the land use changes in the city and its surroundings and its possible impacts on the hydrology of the study area. The land use classification has been carried out for 1992, 2000 and 2014 using LANDSAT data with a resolution of 30 m. The changes in the land use/land cover categories were derived for three different time periods by spatial intersection of land use maps pertaining to 1992 & 2000, 2000 & 2014 and 1992 & 2014 using ERDAS Imagine 2011 and ArcInfo/ArcMap 10 software. The area under settlements has increased by 10.66% during the period between 1992 and 2014, whereas the area under wastelands decreased by 18.29% during the same period. However, the forested area initially decreased from 45.64 sq. km (1992) to 40.24 sq. km (2000) but subsequently increased to 48.62 sq. km in 2014. The Soil Conservation Service-Curve Number (SCS-CN) method has been used to compute the surface runoff. The change in the runoff pattern has not been substantial in commensuration to these changes in the land use pattern as the runoff generation mechanism is also dominantly dependent on the rainfall pattern and its distribution and the antecedent moisture condition apart from the curve number.