The concepts of density and urban morphology are today at the centre of debates on
architecture and urban planning. The concept of density provides a solution to the issue of
urban sprawl and, consequently, offers a way of rethinking sustainable urban and rural
development. The densification of urban centres makes it possible to reduce a vulnerability
related to the excessive use of suburban areas. However, densification is not a “turnkey”
solution. Numerous criteria relating to its use are poorly understood. As numerous contemporary
experiences have demonstrated, urban densification exposes space systems to new, unknown
forms of vulnerability.
First, we will define the concept of vulnerability, specifically that of urban vulnerability, as well as
related concepts, such as those of risk, hazard and challenges. Secondly, we will pinpoint forms
of vulnerability inherent in the over-densification paradigm: this will involve determining the
specific hazards, challenges and risks of this space system. Thirdly, we will demonstrate how
the concept of compactness makes it possible to review at the different urban levels the
densification processes of territories and urban areas. Finally, we will propose a tool for the
optimisation of compact urban morphologies for use in countering the related hazards and risks.