Urban Heat Island Effects in Kathmandu Valley: A Case of Patan

Abstract

Urban Heat Island (UHI) is a phenomenon where urban areas are warmer than surrounding rural counterparts. Every settlement, big or small, suffer from UHI. Researches show that when the natural environment is replaced with low albedo artificial surfaces, they radically alter the aero dynamics, radiative, thermal and moisture properties causing urban regions to be warmer than the surrounding natural areas. As the earth faces global warming, these cities which are already warm due to UHI become more vulnerable to extreme heat. Extreme heat has numerous bad effects on human health, comfort and productivity. It is also responsible for change in micro climate and precipitation. Due the unwanted effects of UHI many of the large cities are working to reduce UHI effect. Kathmandu valley is one of the fastest growing cities in South Asia. The urban area and settlement in the valley floor has expanded from 3% to 23% in four decades (1967-2010). With the valley facing severe air pollution and densification combined with replacement of natural ground surface by urban surfaces, the valley is susceptible to greater effects of UHI. Although studies regarding UHI Effects have been done for the valley, these researches are limited to Landsat Imagery. Since Kathmandu is a valley, there is natural temperature difference induced by different altitude. Therefore, a study has been conducted at micro-level in a city of Patan. To understand UHI effect at micro-level, the temperature has been recorded in four different places representing urban areas with unique combination of green and built areas. The results have been analyzed and depending on the results, the research has focused the questionnaire to understand the effects of increased heat on the people of Patan. By comparing the existing policies with measures taken by different cities, it is found that a better thorough study of the cities in the valley is crucial to understand and exploit natural resources efficiently to control warming of the cities in the valley.