UFlow 1.0: A Computer Model for Projections of Urban Sprawl

Abstract. Cities concentrate most of the world’s population and are the stage of difficult problems around logistics, economy, or quality of life, to enumerate just a few. As an object of research on itself, a urban agglomeration is difficult to characterize; it is both an ensemble of various disconnected heterogeneous elements, and the product of numerous actions and effects between those elements. Studies of the structure and the functioning of cities date back to one century ago, with an increased interest in the last decades on the phenomenon of expansion and all of its impacts.

Models of city growth face the complex nature of this system and are approximative. Different representations seek to balance characteristics as data availability, level of detail of internal processes, or precision. The uflow model approaches the problem with the metaphor of an abstract field, which evolves over time and signals the conversion from empty to urban cells. The procedure for calibration adjusts parameters according to the history of the region under study, and is able to capture local conditions. The implementation takes advantage of parallel hardware, and the simulation can be performed in reverse mode, a feature that can be useful to verify the adaptation of the tool to a given scenario, or to compute approximations of the past state of a region.

Tests confirmed the expected behaviour of the algorithms, and good agreement with actual data. The flexibility of the concept of intensity of urbanization is open to the integration of different data sources into the model, and the possibility of simulating their evolution over time.