All cities have a relationship, more or less explicit, with water. Water resources, and rivers in particular, have always played a crucial role in the development of society and the process of human settlement, as essential sources of resources and important communication routes.
The relationship between urban and river systems has changed several times throughout history, going through phases of profound rupture and alternating processes of recovery. The number of projects constantly involving watercourses in metropolitan areas shows how the theme is still at the centre of urban discourse and how the river still plays an active role in cities.
Urban expansion, often within areas that historically belonged to the river system, and the alteration of climatic conditions, are showing a change in the balance of river ecosystems and their relationship with built-up areas. This highlights the growing fragility of urban settlements built near watercourses, and the need, or opportunity, to rethink this relationship, in terms of protecting the watercourse, the built-up area from the risks of flooding, but also of rediscovering the urban values of the riverside as a civic and human infrastructure.
The thesis explores the theme of the project between large metropolitan areas and the river, first in the European context, and then focuses on the Latin Arc of the Mediterranean, a macro-region with cultural, historical, socio-economic and geo-climatic characteristics that define a clear identity different from the European continental context.
The big coastal metropolitan cities of the Latin Arc, analysed in their relationship with the hydrographic system, are identified as Cities versus Rivers. This is recognised as a specific category of cities which, due to their morphological, geographical and historical characteristics, have developed a complex and often conflicting relationship with the watercourses that cross their dense urbanised area. Due to these morphological and identity characteristics, Cities versus Rivers differ from River-Cities, which have been widely studied in the literature and already recognised as a specific category of study.
The thesis argues, first of all, that the recognition of the coastal metropolitan areas of the Latin Arc as Cities versus Rivers, and therefore as a specific group, makes it possible to lay the foundations for the development of a common strategic-operational approach.
The thesis also argues that riverine, marginal and peripheral areas, incorporated into metropolitan development, have the opportunity to reinvent themselves as new polarities, focusing not only on the essential renaturation and restoration of the river system, but also on the urban values of the riverfront.
Traditional urban water management through grey infrastructure has proven to be unable to adapt to continuous climate changes. On a European scale, the use of green and blue infrastructures is being consolidated, involving the use of natural systems to improve ecosystem services and increase resilience and adaptation. In many cases the hybrid combination of traditional grey infrastructure with green and blue infrastructure can provide solutions to hydrogeological risk that integrate ecological values with the definition of a high quality of public space.
The thesis therefore identifies resilient and hybrid strategies, which use mitigation and adaptation criteria to respond to defence, social reactivation and renaturalization issues, as the approach with which to address the theme of the relationship between city and river; the Cities versus River of the Latin Arc are then identified as the specific field of exploration.
The research explores, in a first phase, the application of the above mentioned strategies in the European scenario of the last thirty years and it identifies, through inductive method, Key Actions and Constants (general characters). In a second phase, it proceeds with the study of Cities versus River in the Latin Arc. From the analysis of these cases, specific approaches of the cities and common criteria for the design of urban-river spaces in the Cities versus River (specific characters) are extrapolated
