Development of blue-green infrastructure to mitigate high building energy demand due to the urban heat island: A case of Varanasi city

Abstract

The urban heat island (UHI) effect leads to an increase in the ambient temperature of urban areas, significantly impacting the built environment. As a direct result of increased heat, the cooling load of buildings increases, leading to higher energy demand. One of the key strategies to reduce this impact of UHI is the creation of the urban blue-green infrastructure (UBGI) networks, which act as nature-based solutions. This study presents a methodological framework to delineate a strategically located UBGI network for Varanasi city and estimates the potential reduction in building cooling energy demand. The study uses geographical information system and remote sensing to spatially locate the UBGI network and a quantified cooling factor to calculate the potential reduction in cooling demand. The urban area is divided into sub-watersheds, depicting primary drainage channels. UBGI elements are delineated based on urban morphology and available land of the respective sub-watershed. The green areas delineated in this way represent an optimal land-suitability scenario where blue and green areas sustain each other. As a result, these delineated UBGI networks show a reduction in building cooling energy demand of 2.1%-20.3%. The study, thus, validates the importance of UBGI in mitigating the negative impacts of UHI and contributed to the creation of more climate-resilient and sustainable cities.