Recent and historical maps as a tool to identify the flood prone zones and the riskiest urbanized areas along the Mediterranean floodplains (Italy)

This research deals with the use of historical cartography as a key tool for identifying flood risk areas for flash floods and consequently also for assessing the increase in the vulnerability of urban areas in the Mediterranean area. In recent years, there has been an increase in flash floods caused by intense and short-term rainfall: this may be related to climate change. But it is undoubtedly also due to inadequate territorial planning that has made it possible to construct buildings and infrastructures in hazardous areas very close to the riverbeds. There has been an analysis of the current, recent and historical cartographic maps of the Italian urban areas of Genoa, Savona and Chiavari in Liguria, Cagliari and Olbia in Sardinia, Carrara, Grosseto and Livorno in Tuscany. A preliminary research has been then extended also to the cities of Nice in Provence-Alpes-Côte d'Azur (France) and Valencia (Spain). These are all cities built over time on floodplains that have experienced catastrophic flooding in recent decades. Map comparisons from the nineteenth century to the present day have allowed us to reconstruct the morphological evolution of these urban areas. The hydrographic network in all the cases has undergone modifications, deviations and through the construction of walls and levees there has also been a progressive reduction in the width of the riverbed often connected to putting watercourses in culverts. Other widespread changes concerned the construction of settlements and infrastructures in depressed and swampy areas in recent years, and the modification of the coastline due to landfill and transport. The serious events that have occurred in recent years have highlighted how the effects of flooding have been amplified by human interventions and structures built in the floodplains.