Investigation of green roofs effects on reducing of the urban heat islands formation (The case of a municipal district of Tehran City, Iran)

Abstract

Urban heat islands (UHI) are of the most common urban phenomena according to which some urban regions, especially downtowns, are hotter than the surrounding by some degrees. Urban development and its relationship with UHIs are important topics that should be first understood and then controlled by devising relevant plans for the trend of urban development. Municipal District 6 (MD-6) is an oldest and the most populous areas of Tehran city in Tehran province-Iran, which also has a high building density. In order to reduce the calculation error, this area is divided into 23 sections. And modeling in each section is done by comparing closely related sections separately. The results of this study can be generalized to all same parts of the world. Initially, earth surface temperature is estimated using Landsat 8 satellite data. Then, the vegetation area of each section is calculated using Normalized Difference Vegetation Index (NDVI). And in the next step, by establishing a relationship between the obtained data, the rate of reduction of UHI is determined by adding a certain area of vegetation. Also, a map was prepared that showing the buildings on UHI, thus measuring the area of roofs with the ability to add vegetation. Finally, the modeling is based on this information. Results show with the addition of vegetation to the roofs of buildings, an average of% 38.58 of the area and 0.68°C of the intensity of the UHI was reduced in this area. Modeling gave different results for other sections depending on their location and the area of buildings inside heat islands that can be used for green roof development. When the material of urban surface changes and water and humidity penetration increases due to the replacement of these surfaces with plants, more time will be required for the increase in ambient temperature by plants versus impermeable surfaces like asphalt and concrete. Therefore temperature rise in plants needs more time than in impermeable surfaces.