The population increase evident in many cities across the world has resulted in an increase in temperature and is known as the Urban Heat Island (UHI) effect. Although the UHI effect is a widely studied phenomenon across both large and medium–sized cities of the world, very few studies have been undertaken on Dhaka, the capital of Bangladesh. The research focus of this project led by Curtin University was specifically on UHI intensity and magnitude, at various spatial and temporal scales, and in both urban and rural areas, to determine any possible influencing factors. The innovative nature of this study lies in the use of both remotely sensed data and in–situ measurements together to quantify the spatiotemporal variability of the microclimate of Dhaka. The project also evaluated the efficacy of green spaces (parks, rooftop gardens, vertical green walls) and blue spaces (ponds and lakes) in mitigating the effects of urban warming.
This project addressed the following SDGs: SDG 11 - Sustainable cities & communities and SDG 13 - Climate action. This information, in association with a provided cost/benefit analysis, could prove useful in determining the value of using these techniques in areas of rapid urbanization. The following research questions were posed for this study:
How is land use change and population (both growth and shift) associated with urban warming of the Dhaka megacity, and what are the factors influencing the UHI, particularly SUHI?
How, and to what extent, has past and current urban morphology, material surface type, land use and green/blue spaces affected Dhaka’s microclimate?
What are the costs and benefits of introducing potential heat mitigating measures (such as greenspaces, green walls and green roofs) into the urban environment?
What specific policies are required for the city to adapt to a changing climate?
Two spatial scales were undertaken at the mesoscale and the microscale. The data collection techniques used in the microclimate study included the use of fixed station and traverse surveys, as well as the thermographic analysis of both biotic and abiotic elements. A greenspace database was developed using high–resolution imagery with subsequent field verification. A general assessment of green roof retrofitting revealed that assumptions made on the degree of overshadowing by tall buildings substantially impacts the number of buildings available for retrofitting. Based on this study and on an extensive literature review, a range of mitigation measures were suggested including the generation of urban (local) climate maps. A review of public policies and key informant interviews demonstrated that existing policies should be revised to meet the current and future needs of Dhaka and other large cities.
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