Land-Use/Land-Cover Changes and Their Impact on Surface Urban Heat Islands: Case Study of Kandy City, Sri Lanka

Abstract

An urban heat island (UHI) is a phenomenon that shows a higher temperature in urban areas compared to surrounding rural areas due to the impact of impervious surface (IS) density, and other anthropogenic activities including changes of land use/land cover (LULC). The purpose of this research is to examine the spatiotemporal land-use/land-cover changes and their impact on the surface UHI (SUHI) in Kandy City, Sri Lanka, using Landsat data and geospatial techniques. LULC classification was made by using a pixel-oriented supervised classification method, and LULC changes were computed by using a cross-cover comparison. The SUHI effect was discussed mainly through the variation of land-surface temperature (LST) over persistent IS and newly added IS. The study showed the dynamics of each LULC and its role in the SUHI. The results showed that IS areas expanded from 529 to 1514 ha (2.3% to 6.7% of the total land area) between 1996 and 2006, and to 5833 ha (23.9% of the total land area) in 2017, with an annual growth rate of 11.1% per year from 1996 to 2006 and 12.2% per year from 2006 to 2017. A gradually declining trend was observed in forest areas. Persistent IS reported the highest mean LST areas compared to newly added IS. The mean LST difference between persistent IS and newly added IS was 1.43 °C over the study period. This is because areas of persistent IS are typically surrounded by IS even in their neighborhoods, whereas areas of newly added IS occur at the edges of the city and are, therefore, cooled by the surrounding nonurban surfaces. This calls for appropriate green-oriented landscape-management methods to mitigate the impact of the SUHI in Kandy City. The findings of the study showed that LULC changes and their effect on the SUHI from 1996 to 2017 made a significant contribution to long records of change dynamics.