Survey and inventory of artificial cavities in the historical centre of Genoa (Italy): a contribution to the development of an experimental Underground Master Plan

Mediterranean cities record the multi-layered nature of phases of urban expansion: historical centres, generally settled in ancient times, underwent significant expansion from the Middle Ages and progressively grew over time (Faccini et al., 2020). Since the second half of the 19th century, and later after the Second World War, cities have undergone uncontrolled development and sometimes irrational urban sprawl. The morphological modifications of the natural topography have taken place over time, not only in terms of land surface (excavations, filling, sea embankments, hydrographic network modifications), but also with underground works (urban hypogea of a hydraulic, civil, religious, war, mining and transport nature). The city of Genoa, and in particular its historical centre, shows both significant morphological changes of the original morphology, and on a dense network of underground environments occupying several hectares of subsoil (Bixio et al., 2017, 2019). These artificial cavities can be analysed either in terms of the potential impact of urban development at land surface on underground spaces, and in terms of geomorphological risk associated with the instability of artificial cavities and consequent propagation of deformations at ground level. In addition, climate change is leading to an intensification of meteo-hydrological phenomena whose ground effects may trigger sink-hole phenomena. This study presents, on the basis of archive research and original underground surveys, the results of the artificial cavities inventory in the historic centre of Genoa, characterised by great hydro-geomorphological and urban complexity. The database developed will provide insight into specific urban planning interventions aimed at the conservation and management of Genoa’s artificial cavities, which represent a unique cultural heritage and a resource for their historical and socio-economic importance. The results can represent the starting point of a specific urban planning tool: an underground master plan, as already developed by other European cities, which is fundamental for sustainable and resilient urban planning policies.