Stemming from the latest webinar organised by the IHS Alumni Network, this article delves deeper into the Isobenefit Urbanism approach, from concept to practical applications and potential challenges. The three speakers were Luca D'Acci (Polytechnic of Turin), Tommaso Gabrieli (Bartlett School of Planning, UCL) and Frank van Oort (Erasmus School of Economics, Department of Applied Economics).
What is isobenefit urbanism?
Isobenefit Urbanism is a relatively new urban development approach spearheaded by our first webinar speaker Luca's S. D'Acci, formerly IHS staff, now an Associate professor at the University of Turin. The model has gotten increasing coverage online, notably featured on platforms like the World Economic Forum and Politecnico di Torino.
As explained by Luca D'Acci, Isobenefit Urbanism envisions a more liveable urban environment created by a morphogenetic code. The algorithm helps build interconnected urban areas where both amenities and nature are located within walking distance. The term itself communicates the concept: iso means equal, while benefit refers to the advantage of quick access to centralities (schools, shops, services) and nature. Isobenefit Urbanism materializes as an algorithm capable of generating various forms of urban areas according to key parameters.
Key rules for a liveable city
The first rule of the isobenefit code states that within a 15-minute walk, each building should reach the ordinary daily points and a centrality, as well as a larger natural area. Secondly, the buildings should be close to each other for at least one square km – to avoid urban sprawl - and the centralities should be interconnected via underground tube/sky train to free up the ground. Lastly, natural areas should interconnected, and each of them should have a surface of min one square km
From an economic perspective, this strategy offers potential for economies of scale and urban growth benefits while reducing negative impacts like traffic congestion, pollution, climate change, and compromised mental and physical health.
Generating future city models
The second speaker, Tommaso Gabrieli (Associate professor at the Bartlett School of Planning, UCL), started by introducing the "Future Urban Growth Lab" project. The research team employs the Isobenefit Urbanism approach to envision various city growth scenarios. Since 2020, they have successfully transitioned from a theoretical framework to actual software output and they are actively collaborating with local authorities and urban planners on implementing this approach. The aim is to gradually refine the software and create a tool that urban planners and other stakeholders interested in future growth scenarios can use.
A distinctive feature of the isobenefit approach is its simplicity, which allows for diverse applications and adaptations. The system involves three cell types: built environments, green spaces, and centralities/amenities. By adjusting parameters, numerous outcomes can be modelled with software demonstrations. Potential developments are flexible: without big constraints (e.g. a new development in a vacant green area), a plethora of isobenefit scenarios arise. More specific parameters imposed by existing urban areas may limit the range of generated scenarios.
The simulations are generated with a QGIS plugin – a tool that is based on the Isobenefit Urbanism concept by Luca D'Acci and the original Python code created by Michele Voto. Learn more about the QGIS plugin here.
The impact of polycentricity on the economy
Can smaller interconnected cities function economically as one larger city? This is the question answered by Frank van Oort (Prof.Dr. Urban and Regional Economics at the Erasmus School of Economics, Department of Applied Economics), the third speaker of the webinar. The economic advantages of urban areas are well-recognized: easy access to skilled employees and services, resource sharing, and the potential for higher wages and employment. However, urban density also brings about challenges like congestion, pollution, and elevated costs.
The polycentric structure is an appealing solution with positive effects on regional productivity. When all connected cities are relatively small and similar-sized, polycentricity brings an advantage. Nevertheless, if one city (like London) is significantly larger than the rest, it will cast an agglomeration shadow on the smaller cities in the vicinity.
Research conducted in European cities reveals that city size strongly correlates with regional productivity. Larger size is generally beneficial from an economic standpoint. While polycentricity alone isn't necessarily advantageous from an economic perspective, it does play a role in interaction with size. If all cities in an area are small and well-connected, they can create a collective effect of a larger agglomeration. However, if one city is significantly larger, the impact of polycentricity diminishes.
The challenges of different contexts
During the Q&A session, participants brought up various questions regarding the applicability of the isobenefit approach.
Potential climate-related challenges arise in harsh environments like deserts. Building in such settings requires significant resources to create liveable conditions. This challenge also extends to delta cities worldwide, which are prone to future flooding. Scenarios for expansion in delta cities included connecting cities over water or building inland using the algorithm.
While the polycentric model is a useful tool for planning formal growth, it might be less suited in the context of informal growth in the Global South. Nonetheless, the simplicity and generality of the code allow for adaptation to diverse contexts. In informal settlements, the preferences and needs of residents can be mapped by making up different rules for the algorithm, in order to establish directions for future interventions.
Lastly, improvements in the sustainability of the model could be achieved by considering the green footprint of the future urban development.
All in all, Isobenefit Urbanism proposes a simple, adaptable approach to urban growth, and its adjustable parameters can extend its use to various contexts. At the same time, limitations imposed by existing urban areas or very harsh environmental conditions, need to be considered.