Evaluating the Trend of Urban Heat Island Impacted by Land Use in Dhaka City: Toward Sustainable Urban Planning

Unplanned urbanization and dense population have turned Dhaka city into one of the most uninhabitable cities in the world, especially the old part of Dhaka in the south city corporation is mostly unplanned with very rare open spaces. The extreme temperature during the summer exacerbates sustainable living conditions as tremendous heatwaves are felt with increased exposure compared to nearby rural areas. Urban heat island is an environmental phenomenon referring to high surface temperature in urban areas due to the urbanization effect compared to the neighboring rural areas. In order to understand the temperature reduction strategy within the prevailing setting of Dhaka city and initiate proper planning for future urban expansion, this study investigated the effect of land surface temperature on different land uses of the Dhaka South City Corporation (DSCC). Data on land surface temperature (LST) were extracted from the ETM + satellite image of 2018 and evaluation was performed for the Normalized difference vegetation index (NDVI) for different classes of land utilization. This enabled the assessment of the trend analysis among these two parameters. Analysis revealed that artificial urban land uses such as commercial, industrial and residential, mixed-use areas have comparatively high LST measures negatively correlated with NDVI. In contrast, land use with increasing vegetation like open spaces, agricultural lands and water bodies seems to be positively correlated with NDVI and hase lower LST measures. However, artificial lands with schools, universities and hospitals classified as public use class were found to have the lowest LST measure and high correlation with NDVI than any other built-up features. Regression analysis indicated that LST and normalized difference vegetation index (NDVI) on artificial land uses have a strong inverse relationship. While explaining the LST versus NDVI for different thermal zones, a positive relationship was obtained for comparatively cooler regions. Moreover, vegetation cover was not adequate to attenuate mean land surface temperature for the high thermal zones in the city and revealed that land uses with extensive heat such as industrial areas might need to adopt extra measures apart from building vegetation cover to alleviate the urban heat island influence.