Geomorphological landscape research and flood risk management in heavily modified Thyrrenian catchment

Since the nineteenth century, most urban catchments in Europe have been subject to significant landscape variations. These modifications have been caused by population change and the transition through rural, industrial and post-industrial economies. Land use and rainfall regime changes, together with land use variations, are frequently associated with flood hazard increase. This paper examines geomorphological landscape changes from the nineteenth century to the present day in the Bisagno Valley, Genoa metropolitan area. The Valley is internationally known for its recurring floods: the last events with fatalities occurred in 2011 and 2014. The extent of landscape change and the history of floods were examined by combining scientific data and information from historical maps, written accounts, topographical drawings and photographs. Historical-geographical and geomorphological analyses were used to reconstruct the runoff for three different periods since 1850. Our results demonstrate that geomorphological landscape variations, including modifications of the river bed, and the abandonment of the countryside and terraces are not sustainable and have progressively allowed an increase in flooding, making it necessary to implement sustainable management policies. In particular, specific spatial urban planning and management measures are necessary in order to mitigate flood hazard and vulnerability