Characterizing the fabric of the urban environment: a case study of metropolitan Chicago, Illinois

Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and pavements) and urban vegetation (trees, grass, shrubs) on the meteorology and air quality of a city, and to design effective implementation programs. In this report, we discuss the result of a semi-automatic Monte-Carlo statistical approach used to develop data on surface-type distribution and city-fabric makeup (percentage of various surface-types) using aerial color orthophotography. The digital aerial photographs for metropolitan Chicago covered a total of about 36 km² (14 mi²). At 0.3m resolution, there were approximately 3.9 x 10⁸ pixels of data.

Four major land-use types were examined: commercial, industrial, residential, and transportation/communication. On average, for the areas studied, at ground level vegetation covers about 29% of the area (ranging 4-80%); roofs cover about 25% (ranging 8-41%), and paved surfaces about 33% (ranging 12-59%). For the most part, trees shade streets, parking lots, grass, and side-walks. In commercial areas, paved surfaces cover 50-60% of the area. In residential areas, on average, paved surfaces cover about 27% of the area.

Land-use/land-cover (LULC) data from the United States Geological Survey was used to extrapolate these results from neighborhood scales to metropolitan Chicago. In an area of roughly 2500 km², defining most of metropolitan Chicago, over 53 percent is residential. The total roof area is about 680 km², and the total paved surfaces (roads, parking areas, sidewalks) are about 880 km². The total vegetated area is about 680 km².