Street Network Resilience Put to the Test: The Dramatic Crash of Genoa and Bologna Bridges

Valerio Cutini,Camilla Pezzica

doi:10.3390/su12114706

Abstract

Various hazards and endemic threats are increasingly looming over cities, leading planners to rely on a rich toolbox of flexible and inclusive planning instruments and methods, capable of dealing with unpredicted events or sudden urban contingencies, when seeking sustainable urban futures. While sustainability-oriented innovative planning approaches are gaining momentum, ways to embed connected concepts in operational planning and design decision support systems have yet to be fully developed and validated. This paper tackles this issue by proposing and testing, in a real-life scenario, a method for the computational analysis of street network resilience, based on Space Syntax theory. The method is suitable to quantify the capacity of urban grids to absorb sudden disturbances and adapt to change, and to offer support for mitigation decisions and their communication to the public. It presents a set of configurational resilience indices, whose reliability is qualitatively assessed considering the ex-ante and ex-post urban configurations generated by two exceptional and dramatic bridge crashes. These events occurred almost simultaneously in two Italian cities with peculiarly similar characteristics. The results confirm the value of the proposal and highlight urban form, and particularly its grid, as a key driver in building urban resilience, together with the self-organisation capacity of local communities.

Highlights

Most of the world population already lives in cities [1], whose stability is threatened by numerous natural or man-made hazards, ranging from earthquakes to flooding, from wars and terrorist attacks to pandemics and disastrous accidents
The research analyses the street network of the municipalities of Genoa and Bologna. These cities are both hubs of primary importance within the Italian transportation network, and in each of them the motorway is a key component of the road network structure
On August 14, only 200 kilometres away from the first disaster, the Polcevera bridge, which served the motorway passing through the metropolitan area of Genoa, collapsed due to causes that are yet to be fully clarified

Summary

Introduction

Most of the world population already lives in cities [1], whose stability is threatened by numerous natural or man-made hazards, ranging from earthquakes to flooding, from wars and terrorist attacks to pandemics and disastrous accidents. The combined effects of rapid urbanisation trends, climate change and the diffusion of political uncertainty make such occurrences increasingly frequent and alarming, with important implications for planning, and the need to provide rapid and sustainable responses. The 11th Sustainable Development Goal puts both sustainability and urban resilience at the centre of the international strategic urban agenda [2]. Some related concepts have been transferred to multilateral risk management and urban disaster mitigation policies such as [3], urban resilience principles are yet to be fully operationalised [4]. Urban resilience-thinking [6] and novel sustainable urban planning approaches based on urban systems’ performance, such as Performance-Based Planning (PBP) [7] and Adaptive Planning and Management (APM) [8], require the support of a rich toolkit of such planning instruments that is fully operational

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Results

Discussion

Conclusion