Quantifying urban growth: confronting planned and actual street network growth in Porto, Portugal

The growth of cities has always been a matter of interest in academic research. In order to better understand the built environment, researchers have resorted to decomposing the several layers, which constitute the history of cities and, hence, their growth. Processes of city growth can be observed through the analysis of a given period of time and it is this analysis that enables the critical description of the evolution of a city. The relevance of this topic is built upon the belief that by critically describing the evolution of a city, one may shed light on the consequences of that evolution and critically assess the future. In this research, this critical assessment intends to lean towards street network growth. The research focuses on the review of top-down urban planning approaches such as the implementation of Master Plans. This study proposes to assess the relevance of planned urban growth regarding the urban street network as a counterpoint to its actual growth. Both scenarios are expected to deliver different outcomes concerning the accessibility of the city. Accessibility becomes a central point of discussion as extensive research argues for its major role on the social and economic performance of a city. An approach within the realm of Urban Morphology is proposed. In more detail, the city of Porto, in Portugal, is used as a case study where an analysis of two Master Plans from 1947/54 and 1960/62 is performed. This analysis is then compared to the actual growth of the city, which, besides incorporating part of the planned additions to the street network, also shows evidence of growth that was not contemplated. This approach suggests an innovative way of assessing the performance of top-down urban interventions by quantifying growth in each stage of the city and in the Master Plans making it possible to measure the impact of each one. This comparison is the framework through which planned growth is assessed in a critical manner. The difference of results between planned and actual growth gives a comprehensive perspective of how Master Plans can affect the urban system and backs the discussion about how global and local structures endure those changes. In terms of results, the Master Plans are expected to impact both global and local structures of the city’s street network, but to what extent? The hypothesis is that although Master Plans may focus on the global structure of the city and unplanned additions, as an effective part of actual growth, have a more local impact, both scales have a symbiotic relationship where one is always affected by the other.