Ecological Evaluation of Urban Heat Island Effect in Colombo City, Sri Lanka Based on Landsat 8 Satellite Data

The Colombo is the main commercial metropolitan city in Sri Lanka with having highest population and building density, making the city is more ideal place to form Urban Heat Islands. This study was conducted to ecologically evaluate the Urban Heat Island effect in Colombo city using Landsat 8 satellite data. The temperature variation of the city was acquired by Land Surface Temperature, a parameter derived from Landsat 8, band10 (Thermal Infrared band), band4 (Red band) and band5 (Near Infrared) using Radiative Transfer Method. Evaluation of ecological condition was assessed using Urban Thermal Field Variance Index, a quantitative measurement of the urban ecological quality of life with respect to Urban Heat Island effect. The model verification was obtained by theoretical relationships between Surface Temperature, Normalized Difference Built-up Index and Normalized Difference Vegetation Index. Temperature distribution in Colombo city revealed that, majority of the environmentally critical areas were located near the harbor, central business area along the main transport system and coastal belt. According to above index, the city experiences two extremes as areas of optimal micro-climate and areas with heat stresses indicating the requirement of strong Urban Heat Island mitigation measures in future landscape development and urban planning of the city.