Calibration of a density-based model of urban morphogenesis

Juste Raimbault,Elsa Arcaute

doi:10.1371/journal.pone.0203516

Abstract

We study a stochastic model of urban growth generating spatial distributions of population densities at an intermediate mesoscopic scale. The model is based on the antagonist interplay between the two opposite abstract processes of aggregation (preferential attachment) and diffusion (urban sprawl). Introducing indicators to quantify urban form, the model is first statistically validated and intensively explored to understand its complex behavior across the parameter space. We then compute real morphological indicators on local areas of size 50km covering all European Union, and show that the model can reproduce most of these existing urban morphologies. It implies that the morphological dimension of urban growth processes at this scale are sufficiently captured by the two abstract processes of aggregation and diffusion.

Highlights

The study of urban growth, and more its quantification, is more than ever a crucial issue in a context where most of the world population live in cities which expansion has significant environmental impacts [1] and that have to ensure an increased sustainability and resilience to climate change
The understanding of drivers for urban growth can lead to better integrated policies. This remains a question far from being solved in the diverse related disciplines: urban systems are complex socio-technical systems that can be studied from a large variety of viewpoints. [2] advocates in that sense for the construction of a dedicated science defined by its objects of study more than the methods used, what would allow easier coupling of approaches and urban growth models taking into account heterogeneous processes
Our contribution is significant on several points: (i) we compute local morphological characteristics on a large spatial extent; (ii) we give significant insights into model behavior through extensive exploration of the parameter space; (iii) we show through calibration that the model is able to reproduce most of existing urban forms across Europe, and that these abstract processes are sufficient to explain urban form

Summary

Introduction

The study of urban growth, and more its quantification, is more than ever a crucial issue in a context where most of the world population live in cities which expansion has significant environmental impacts [1] and that have to ensure an increased sustainability and resilience to climate change. The understanding of drivers for urban growth can lead to better integrated policies. This remains a question far from being solved in the diverse related disciplines: urban systems are complex socio-technical systems that can be studied from a large variety of viewpoints. [3] shows that in first approximation, the Gibrat’s model postulating random growth rates that do not depend on city size, produces the well-know Zipf’s law. This rank-size law is a typical stylized fact witnessing hierarchy in systems of cities.

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Discussion

Conclusion