Analyzing Trends of Urbanization and Concomitantly Increasing Environmental Cruciality—A Case of the Cultural City, Kolkata

Abstract

The environment in the city of Kolkata has suffered an extensive damage at hands of urban expansion. This study investigates the urban expansion in Kolkata over the last few decades and assesses its impact on environmental criticality using satellite derived parameters. An Environmental Cruciality Indicator (ECI) was developed using the vegetation indices and the land surface temperature (LST). Landsat TM and ETM+ data for the years 1989, 2006, and 2010 have been employed for this study. Land use land cover (LULC) maps were prepared using supervised classification with an accuracy of 86–90 % (0.82–0.87 kappa). Urban expansion amounting up to 109 km² was observed in the city over the past two decades. These changes modified some other environmental variables such as the moisture intensity of the surface, LST, greenness, and the built-up intensity. These changes further impact the quality of environment that was analyzed using the ECI. The indices used were Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Built-up Index (NDBI). Satellite derived ECI shows a degrading trend for environment in larger parts of the city. The magnitude and spatial extent of higher environmental cruciality are coherent with the urbanization (sparse and dense settlement) patterns in and around the city. LULC has been an important factor determining the health of the environment and hence influencing the local climate.