Spatio-temporal Analysis of Environmental Criticality: Planned Versus Unplanned Urbanization

Abstract

The economic boom in the Indian cities is causing rapid urban growth, mostly in an unplanned fashion. The growth of urban built-up is primarily taking place by replacing vegetation and other low radiative surfaces, increasing the magnitude and spatial extent of heat concentrations. The resulting phenomenal increase in temperature, known as Urban Heat Island (UHI), raises environmental criticality. Satellite remote sensing provides a breakthrough for monitoring the spatiotemporal variations of UHI by estimating Land Surface Temperature (LST) and surface biophysical parameters. The objective of this work is to compare the changing pattern of LST that resulted from urban growth and associated biophysical characteristics in a planned city (Kalyani city) and an unplanned city (Barasat city) in West Bengal, India from 2005 to 2019. Using Landsat data, the study retrieved summer LST along with the prepared vegetation index (NDVI) and built-up index (NDBI) for the years 2005 and 2019. The Environmental Criticality Index (ECI) was calculated for the periods from LST, NDVI, and NDBI datasets. The long-term (1988-2019) LST has been derived using the cloud computation technique to analyze the trend. Over the years, though the average LST of Kalyani is relatively high from Barasat, a rapid increase in LST is noticed for Barasat city. Between 2005 - 2019, the rapid unplanned growth in Barasat city has not only increased the LST but also raised the concern for environmental criticality as compared to Kalyani City. The correlation of LST with NDVI and NDBI suggests that urban heating is significantly controlled by the surface characteristics that need to modify through proper planning for urban sustainability. This study may assist planners, administrators, and researchers in decision-making.