Historical Geomorphological Research of a Ligurian Coastal Floodplain (Italy) and Its Value for Management of Flood Risk and Environmental Sustainability

The alluvial plain of the Entella River (Eastern Liguria), historically affected by damaging flood events, has been heavily modified over the past 250 years by human activity and natural processes. A qualitative and quantitative analysis of the morphological and land use evolution of the Entella floodplain since the 18th century was carried out using base maps and aerial photos ranging from 1758 to 2016. These diverse sources were Geographical Information System (GIS) georeferenced. Additional information on land-use change was gathered from historical documents and recent research reports. The main transformations to the floodplain include morphological changes, e.g., narrowing, channelization, displacement of the river channel and the advance of the coastal line due to fills and embankments. In addition, there has been very significant urbanization with loss of vegetated and agricultural areas. Our results indicate the primary role of human disturbance on morphological changes and landscape modifications of the coastal floodplain, particularly over the last 200 years. Furthermore, the historical geomorphological and cartographical analysis we adopted to reconstruct the floodplain transformation represents an essential tool in flood risk mitigation and environmental sustainability management, particularly in an urbanized coastal plain historically affected by floods.