Culverted watercourses as an anthropogenic constraint of flood risk in the historical centre of Genoa (Italy)

In recent years, artificial cavities have raised interest among the scientific community, both due to their relevance in terms of cultural and landscape heritage and because they are linked to potential hazards to surface structures. Underground voids in cities have been often established over time with a specific purpose or have resulted from the layering of different urban evolution phases, which in Mediterranean cities are often thousand years old, the case of culverts being particularly frequent. Generally, culverts have been associated with the need to expand urban areas due to space constraints. Underground voids have been established and modified (or even under-dimensioned) over time and their state of efficiency and preservation is hardly verified, leading to very hazardous conditions. This research presents the waterways in the historical centre of Genoa, the coverage of which, now almost complete, began in the Middle Ages. While the historical channelization of the streams of the old city can be considered as a structure of cultural value, it should be pointed out that the subsequent modifications and state of preservation of such artifacts have led to localized hazardous conditions and thus risk to buildings and infrastructure, some of which have been recognized as UNESCO World Heritage Sites (“Strade Nuove and Palazzi dei Rolli”). Therefore, there is need to acquire detailed surveys of the entire channelized and culverted hydrographical network in order to assess its hydraulic efficiency, hydrogeomorphic features, and structural suitability, and to activate a monitoring network. Such measurements are crucial for effective management of hydrogeomorphic risk in urban areas, also in light of Global Climate Change.