Comparing the urban form of South European cities using fractal dimensions

This paper compares built-up patterns and the urban form of South European cities using fractal dimensions. Fractal dimensions (D) are estimated in two different ways: (a) using binary images with information only on the built-up and non-built-up areas and (b) using grayscale images that represent the different built-up densities. The Urban Atlas and the Imperviousness-Soil Sealing Degree datasets are used to compute fractal dimensions for the 14 cities in Spain, Portugal, Italy, Greece and the Mediterranean France with a population exceeding one million. The results indicate that differences in urban form are reflected in the fractal dimensions. Fractal dimensions are higher in cities characterized by a relatively continuous and homogeneous sprawl than in cities with elongated urban form or discontinuous development in periurban areas. In Spanish cities urban development is fragmented with clustered and contrasted patterns and this leads to lower fractal dimensions. In Italian and Portuguese cities, development follows relatively homogeneous patterns and D values are significantly higher. Other key findings of the research indicate that: (a) grayscale fractal dimensions are lower than the corresponding binary ones, nonetheless the relative ranking of the cities according to D remains about the same regardless of the method used and (b) fractal dimensions are highly correlated to the average built-up density.