Models of urban morphogenesis to link urban form and function

Résumé En

The understanding of processes driving urban growth is a necessary step before designing and implementing policies for territorial sustainability.At the intermediate scale of metropolitan areas, urban form, in the sense of the spatial distribution of settlements and activities, has a complex relation with urban function. We propose in this presentation to investigate models of urban growth at such a scale, in the conceptual framework of morphogenesis that we define as the emergence of form and function and their strong coupling. We first investigate a simple reaction-diffusion model of urban morphogenesis for population density, capturing the contradictory processes of urban concentration and dispersal. The model is calibrated on real density data for Europe and shown to reproduce most of existing territorial forms. It is also tested on some large areas across the world using the Global Human Settlement Layer database. We then introduce urban functions in an indirect way by coupling this model with road network generation models, since networks shape accessibility landscapes to amenities. Multiple network generation heuristics are compared and shown to be complementary to reproduce existing coupled patterns of urban form and network topology. We finally discuss potential links with urban fractal properties and developments towards more realistic data-driven morphogenesis models which could be applied to the design and test of policies to increase sustainability.