Relationship between flood hazards and geomorphology applied to land planning in the upper Aveto Valley (Liguria, Italy)

In the framework of an analysis of geomorphological hazards for environmental protection and land planning, a multidisciplinary survey programme has been conducted, promoted by Genoa Province, in order to assess the flooding risk in the fluvial plain of the Aveto stream. The studied catchment basin extends over an area of 172 km2 in the eastern Ligurian sector of the Apennines, close to the border with the Emilia-Romagna region. A detailed geomorphological analysis was carried out by means of field observations in the flood plain and aerial photograph interpretation of the entire basin, particularly focusing on those slope sectors affected by processes due to gravity and running water potentially involving the stream. This included comparison of aerial photographs taken during the last few decades, and comparison with historical maps dating as far back as the 18th century. Comparison of the collected data has allowed for the zoning of the fluvial plain into three areas, characterized by different levels of geomorphological hazard due to floods: high - present day river bed and contiguous fluvial terraces, subject to ordinary floods; medium – alluvial plain occasionally subject to floods and slope areas affected by active geomorphological processes potentially involving the stream; low - terraces, alluvial deposits, and fluvial plains subject to catastrophic floods and slope areas contiguous to the river bed without active geomorphological processes involving the stream. Finally, the comparison between maps of flood hazard, historical flooding areas, and hydraulic zones showed satisfactory results with the overlapping of zoning based on different criteria, confirming the reliability of flood risk assessment based on geomorphological data.