Planning and selection of green roofs in large urban areas. Application to Madrid metropolitan area

Due to the numerous environmental problems facing today's society, and especially urban areas, green roofs are presented as an adequate technique to fight the consequences of pollution, traffic and lack of green areas. These green structures help to reduce the effects of Urban Heat Island, to decrease noise and atmospheric pollution, to protect homes from isolation and cold; they also capture rainwater and improve biodiversity. A new methodology is presented to select the best location of green roofs in large cities. In the first phase, this methodology helps to determine the most suitable neighborhoods, analyzing four main variables of interest in urban environs: pollution, traffic, green areas and population. In order to benefit a greater number of inhabitants, the neighborhoods with the worst air quality, more traffic, less green áreas and higher population density, are selected. In the second phase, we used LIDAR technology to identify available roofs for the installation of the green roofs according to the height and roof typology of the buildings. To select the optimal roofs, connectivity analysis techniques were used. The results show that the most conflictive neighborhoods from the environmental point of view are those located in the city center, so they result the ideal places for the location of green roofs. In general, all neighborhoods except one presented high connectivity values. This methodology helps to improve the connectivity of the green spaces of Madrid, favoring the dispersion of plant and animal species, air quality and promoting sustainable and quality urban development