Study on the impact of building regulation on street morphology and ensuing microclimate in planned residential area of Dhaka City

Abstract

Cities have a tendency to transform through intensifying its land use in urban areas. Bangladesh is a developing country where the expansion of the capital city Dhaka is resulting in one of the mega cities of the world. Buildings are being built to accommodate the increasing inflow of population within this mega city. Recent studies reveal that the impact of urban heat island in Dhaka city is gradually increasing. Thus proper master plan is required for sustainable development and also to improve microclimate within urban areas. Microclimate within the streets is influenced by its morphological character, geometric pattern, orientation, built density and available green space. In residential areas of Dhaka, street morphology is an outcome of the neighboring built forms, usually controlled by building construction rules. The Metropolitan Building Construction Rules [BCR] introduced in 2006 with the application of Floor Area Ratio [FAR] with amendments in 2008 and further in 2013. FAR rule results increased building height, relatively smaller building footprint and potentially free ground floor resulting in an urban street canyon with uneven canyon walls. Thus the research examines the results of an investigation, how FAR impacts outdoor street microclimate with spatio temporal characteristics of the ambient climatic environment. Different microclimate parameters at pedestrian level were studied. Results from an intensive field survey were studied at locations of different street orientations in a planned residential area of Dhaka city. Computer based simulation results as well as observed field data were compared, statistically analyzed and examined in terms of street orientation, aspect ratio, building mass configuration. Comparisons of the present building regulation with the previous are made. Possible urban design considerations are discussed to enhance urban street microclimate for planned residential areas.