Urbanization of Colombo City and Its Impact on Land Surface Temperature from 2001-2019

The Urban Heat Island (UHI) is a metropolis whose temperature is several degrees higher than the surrounding rural areas. In connection with the UHI phenomenon, the earth’s surface temperature (LST) was estimated using Landsat satellite imagery covering the city of Colombo. The results showed that the UHI effect spread to the north, east, and southeast of Colombo City between 2001 and 2019. Analyzing the correlation between the LST, normalized vegetation difference index (NDVI) and normalized difference index (NDBI), it is found that there is an inverse correlation between NDVI and LST; however, it is reported that NDBI is associated with the four LST periods of 2001, 2009, 2016 and 2019 which indicates that vegetation can weaken UHI, while built-up land can enhance the UHI. The result of albedo analysis shows that low albedo has a greater impact on the formation of UHI. According to this environmental assessment using the Urban Thermal Difference Index (UTFVI), 27% of the region suffers the worst thermal stress. Therefore, in future urban planning, mitigation measures should be taken to improve the quality of the life of the people and the environment in the city of Colombo.