IMPACT OF LULC AND POPULATION DENSITY CHANGE ON SURFACE URBAN HEAT ISLAND IN BHAGALPUR, BIHAR USING REMOTE SENSING AND GIS

Abstract

It is well-known that all the metropolitan cities in India, such as Delhi, Mumbai, Bangalore, Hyderabad, Kolkata, and other heavily urbanized cities, experience considerably higher temperatures than their rural surroundings. This phenomenon is known as urban heat island (UHI). This is generally caused by the modification of natural environment by excessive use of construction materials such as concrete, asphalt, steel, etc., having lower albedo. Since lower albedo materials reflects less and absorb more heat, it significantly increases the surface temperature within the city. The other major cause of urban heat island generation is population density. Due to excessive urbanization, population density increases exponentially, resulting in increased anthropogenic activity within the city, thereby further increasing the land surface temperature. Various researchers have done several studies to analyze the effect of urban heat island (UHI) in highly urbanized cities in India. Still, minimal research has been done on developing cities that are undergoing major land-use land-cover (LULC) change. This research aims to study the effect of the spatial and temporal pattern of LULC and population density on land surface temperature (LST) within a developing city from 1990 to 2020 using satellite data. The study area selected is Bhagalpur city of Bihar. This study analyses the change in spatial pattern of land use land cover and population density that occurred between 1990 and 2020. Multi-temporal data set for the year 1990, 1995, 2000, 2005, 2010, 2015, and 2020 have been used to quantify the LULC and population density change and correlate with the study area's thermal characteristics. Correlation of indices such as NDVI and NDBI with land surface temperature (LST) were also established. The result shows that as built-up area increased more than four times (from 4.79 km2 to 22 km2), and population density has almost doubled (from 83 person/hectare to 151 person/hectare) during the study period. Ward wise growth of population density inside Bhagalpur city has also been analyzed with respect to land surface temperature to study the effect of population density on land surface temperature. The study revealed that the population density is directly linked with the land surface temperature but had some exceptions based on land use pattern. The city core experienced considerably higher temperature than the city outskirts indicating the generation of urban heat island (UHI) effect. Though the temperature difference is around 2° C for year 2020, the trendline shows that it will increase considerably by the next decade if proper mitigation strategies are not implemented.