Urban heat island (UHI) development and mitigation measures in three Bangladesh cities: Dhaka, Chattogram, and Sylhet
Date
2024
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Publisher
University of Delaware
Abstract
The surge in urban population worldwide has led to a swift expansion of urban areas and noticeable temperature differences between urban centers and their rural surroundings. This phenomenon, known as the Urban Heat Island (UHI) effect, is increasingly recognized as a significant human impact on the environment with both local and global consequences. The rapidly expanding populations in Asian cities, including Bangladesh cities, are anticipated to be highly susceptible to these impacts. Although the UHI effect has been extensively studied in both large and medium-sized cities globally, comparative research on rapidly developing Bangladesh cities remains sparse. The study compares the UHI development in the three largest cities of Bangladesh that includes Dhaka, Chattogram (previously known as Chittagong), and Sylhet, after documenting the changes in land use patterns in the current municipal boundary and proposed future extension areas over the last two decades. The research also integrates uncertainty maps to specify the confidence levels in land use classification results that are not prevalent in prior studies. Additionally, most existing studies have relied solely on satellite data to analyze the land surface temperature (LST) to quantify the surface urban heat island (SUHI), often overlooking the atmospheric urban heat island (AUHI). This study combines in-situ measurements (AUHI) with remotely sensed data (SUHI) to assess the spatiotemporal variability of the city's microclimate. The dew point temperature was computed in conjunction with temperature to enhance the understanding of heat stress conditions. Along with evaluating the temperature and dew points trends over the twenty year period, their statistical significance was computed using the Mann-Kendall test and the t-test performed to determine if the urban and rural time series were distinct. The final step of this study investigated the UHI mitigation measures addressed in each city’s future development plans to reduce urban warming effects by increasing green spaces (such as parks, rooftop gardens, and vertical green walls) and blue spaces (such as rivers, ponds, and lakes). Effective mitigation strategies most appropriate for each city’s urban context were highlighted to help urban planners and policymakers take immediate action to reduce the adverse impacts of UHI and ensure sustainable and livable urban environments.
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Keywords
Atmospheric urban heat island, Bangladesh, Chattogram, Land surface temperature, Surface urban heat island, Sylhet