Cooling effect of roadside urban shade trees an analysis on urban fabric of Dhaka

Abstract

The rapidly growing population and consequent unplanned and uncontrolled urbanization of Dhaka, the capital city of Bangladesh, has resulted in the gradual loss of green spaces in the city. However, the city possesses enriched quality of urban fabric contributing towards varied forms of environmental benefits. Mounting empirical evidence shows that the roadside urban vegetations are effective in mitigating the heat emission and pollution of built environment. The shade trees have impact on the built forms, in terms of radiative cooling, pedestrian thermal comfort, temperature control and reduction of air pollution by absorption of the pollutant. This study focuses specifically on the ‘cooling effect’ of the roadside trees and plants of Dhaka city, analyzes their impact on air temperature under the shaded and unshaded areas on roads including the comparison between two important primary roads with and without mutual shading, and proposes solutions for maximizing the cooling effect. For proposed research query, temperatures under the tree canopies of a shaded road and an unshaded road were measured repeatedly at mid days without precipitation and then an evidence based microclimatic software simulation is used. Finally, multiple regression analysis is done to analyze the contribution of vegetation characteristics to the cooling effect.