Radial Urban Forms: Lessons from Land Profile Scaling Analyses & Spatial-Explicit Models

We definitely live in an increasingly urban World for half of humanity now lives in cities. Cities provide wealth but also negatively impact the environment and the health of citizens. Arguably the benefits and costs of cities relate to both their size, in population terms, and their internal structure, in terms of the relative spatial arrangement of built-up and natural land. Much of urban research focusses on very large cities and urban cores. Yet 3 urban human out of 4 live in cities of less than 4 million inhabitants (according to the global GHSL dataset). Similarly, 3 out of 4 in a typical (European) city do not live in its core but beyond (using a 7-8km radius to define core for a city like London or Paris). To address urban sustainability issues and design adaptation policies, these 75% certainly count and, we can argue, also deserve specific attention because of the relative proximity between urban and non-urban (natural) use that smaller cities and suburban (non-core) areas may permit. In this respect, it is key to understand how the internal structure of cities, in particular the form and density of built-up areas and the interwoven green space emerge out of the core up until the fringe. It is also key to understand whether the form of cities, especially density gradients and the share of urbanised/non-urbanised land change with city size. In this talk we draw lessons from 2 research approaches to urban forms: one theoretical that uses spatial micro-economic simulations, and one empirical that uses spatially detailed land use datasets. Our theoretical simulations relate individual behaviour to urban forms while our empirics relate urban forms to city size. Both have in common a radial perspective to cities, i.e. explicitly or implicitly assuming that the accessibility trade-off to a given centre is a key determinant of locations and land uses. In both cases, we look at urbanisation and green space structures and at pollution exposure as an example of impact.