Built-Up Encroachment and the Urban Field: A Comparison of Forty European Cities

We define the urban field as the spatial organisation of urban densities according to decreasing gradients from centre to periphery. This urban field can be estimated from the encroachment of built-up areas. The CORINE Land Cover database enables the measurement of the gradient values for the spatial distribution of built-up areas in European cities. Instead of the exponential or power functions, which usually provide the best fit for the distributions of population densities, we find that two linear functions strongly differentiating a central and a peripheral gradient provide the best fit for built-up surfaces. The comparison between the 1990 and 2000 CORINE images demonstrates a convergence in the trend of urban spread between Northern and Southern European cities. However, it is still difficult from the data to decide which of the models of urban field is winning: will the steeper central gradient become diluted into the less dense periphery, or are the closer fringes of the central parts becoming integrated into the ordered pattern of the urban central agglomerations?