Development of a Thermal Risk Map Case Study: Kelaniya City of Sri Lanka.

Abstract

The land surface temperature in city areas is increased compared to the adjacent rural areas as a result of industrialization and urbanization. This phenomenon is known as the formation of heat island. In the context of population density, Kelaniya is the second largest Divisional Secretariat (DS) division next to Colombo. Main access to Colombo from Kandy is laid across Kelaniya in which thousands of vehicles travel through. Therefore, Kelaniya is subjected to heat stress. Since this will cause to thermal discomfort, cooling devices are additionally driven by increasing the energy demand. The main Objective of this study is to develop thermal risk map for Kelaniya. Thermal band(s) of the Landsat images were used to derive LST. Derived temperature values were normalized, extracted the areas which are greater than 0.6 as heat islands and combined. According to the status of heat islands in the combined image, a map on the persistence of heat islands was derived. Areas which existed as heat islands in all three years, at least one year or none and other were considered as high, low and moderate thermal risk areas respectively. The areas with high thermal risk were extracted, intersected with GramaNiladhari (GN) divisions of Kelaniya and again classified into three risk classes as high, moderate and low. GN divisions with more than 50%, between 50% to 20% and below 20% of high thermal risk areas from its total area were referred as high, moderate and low thermal risk GN divisions respectively. More than 50% of the areas in Kelaniya still remains as low thermal risk areas. Therefore, actions should be taken to prevent the transformation of low thermal risk areas into other two categories while accelerating the conversion of moderate and high thermal risk areas into low thermal risk category.