Impact of Urbanization on Urban Heat Island Intensity in Major Districts of Bangladesh Using Remote Sensing and Geo-Spatial Tools

Md Naimur Rahman,Subodh Chandra Pal,Md Rakib Hasan Rony,Abu Reza Md Towfiqul Islam,Edris Alam,Md Saiful Islam,Farhana Akter Jannat

doi:10.3390/cli10010003

Abstract

Urbanization is closely associated with land use land cover (LULC) changes that correspond to land surface temperature (LST) variation and urban heat island (UHI) intensity. Major districts of Bangladesh have a large population base and commonly lack the resources to manage fast urbanization effects, so any rise in urban temperature influences the population both directly and indirectly. However, little is known about the impact of rapid urbanization on UHI intensity variations during the winter dry period in the major districts of Bangladesh. To this end, we aim to quantify spatiotemporal associations of UHI intensity during the winter period between 2000 and 2019 using remote-sensing and geo-spatial tools. Landsat-8 and Landsat-5 imageries of these major districts during the dry winter period from 2000 to 2020 were used for this purpose, with overall precision varying from 81% to 93%. The results of LULC classification and LST estimation showed the existence of multiple UHIs in all major districts, which showed upward trends, except for the Rajshahi and Rangpur districts. A substantial increase in urban expansion was observed in Barisal > 32%, Mymensingh > 18%, Dhaka > 17%, Chattogram > 14%, and Rangpur > 13%, while a significant decrease in built-up areas was noticed in Sylhet < −1.45% and Rajshahi < −3.72%. We found that large districts have greater UHIs than small districts. High UHI intensities were observed in Mymensingh > 10 °C, Chattogram > 9 °C, and Barisal > 8 °C compared to other districts due to dense population and unplanned urbanization. We identified higher LST (hotspots) zones in all districts to be increased with the urban expansion and bare land. The suburbanized strategy should prioritize the restraint of the high intensity of UHIs. A heterogeneous increase in UHI intensity over all seven districts was found, which might have potential implications for regional climate change. Our study findings will enable policymakers to reduce UHI and the climate change effect in the concerned districts.

Highlights

Urbanization, for instance, in the form of roads, industries, buildings, etc., contributes significantly to changing climatic measures by warming the atmosphere and generating carbon emissions associated with increased surface temperature, referred to as an urban heat island (UHI) [1]
Several previous investigations indicated the voluminous propagation of heat due to building form, land use pattern and industrialization, which results in an increase in land surface temperature (LST) in urban and suburban areas [5,6,7,8,9]
Spatiotemporal land use land cover (LULC) variations in seven districts were categorized in four definitions for 20 years, including the three assessed years of 2000, 2010, and 2020 (Figure 4)

Summary

Introduction

Urbanization, for instance, in the form of roads, industries, buildings, etc., contributes significantly to changing climatic measures by warming the atmosphere and generating carbon emissions associated with increased surface temperature, referred to as an urban heat island (UHI) [1]. It involves population migration, socioeconomic changes, physical diversion, and multiple differentiations in land surface observation [2]. Dynamic temperature increase is observed in structurally compact developed areas, which causes the enhancement of UHI in urban areas compared with rural areas [4]. UHIs have recently become a topic of interest among many research scholars

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Results

Conclusion