Conference Papers

Authors: Jalpa Gandhi, Rajan Rawal
Abstract:

Urbanization has direct impact on the spatial structure of the city, which in turn results in the dramatic change of the overall immediate environment. High-rise, high density built areas provides multiple surfaces

for the reflection of direct and indirect solar radiation as well as absorption & storage of the anthropogenic heat. It is often seen that this heat gets re-radiated & trapped due to neighborhood buildings causing changes in surface & ambient air temperature. To mitigate such effect various approaches were studied and experimented in the past. Out of which impact of vegetation is considered to be one of the most potent measure to mitigate negative impact of urban form on high surface and air temperature. This is proved through number of research studies and on-site measurements. This study is an approach to understand the role of urban environment on urban area micro-climate with reference to vegetation in the city of Gandhinagar, India. An urban area of Central Business District is configured according to the rules of ground coverage, floor space index (FSI) and site setback as mentioned and laid out in building byelaws of city. For the purpose of this study a three dimensional numerical computer model ENVI-met V3.4, that analyzes micro scale thermal interaction with urban environment is used. Input of environmental data is extracted from Ahmedabad IWEC weather file. Simulations are done for typical summer day. Parametric variations are made to get prediction of surface and air temperature in different built and un-built conditions. Different scenarios are designed besides the model condition where studies are done on basis of different surface materials, changing density of vegetation & changing the type of vegetation. The results are evaluated on the basis of ambient air temperature & Surface temperature. Findings show that on an average 2°C drop in ambient air temperature is achieved in urban area of Gandhinagar’s microclimate with the addition of trees. Vegetation is seen more valuable during harsh afternoon hours, due to its shading and evapo-transpiration properties. This suggests that shading streets with trees is advisable, which results in achieving reduction of minimum 0.5°C & maximum 1.5°C average air temperature across the year. The cooling effect of trees is also seen in the surrounding areas. Strategic plantation of trees and selection of surface material is found as very important aspects to lower adverse effect of urbanization.

Keyword:
Presented at: 5th International Conference on Energy Research and Development. Kuwait.2012

+