Historical geo-database for multi-hazard zoning in the Costa Viola area (southern Calabria, Italy)

Historical geodatabases are crucial resources for the analysis and management of susceptibility, hazard, and risk. Regarding landslides, they provide valuable insights into the location, date, type, size, activity, and triggering factors of such events, as well as the resulting damage. Similarly, for floods, affected areas can be identified and damage inventories systematically updated, highlighting the most impacted sectors.

This study, conducted within the framework of the Next Generation EU—Italian NRRP, Mission 4, Component 2, Investment 1.5, call for the creation and strengthening of ‘Innovation Ecosystems’, building ‘Territorial R&D Leaders’ (Directorial Decree n. 2021/3277)—project Tech4You—Technologies for climate change adaptation and quality of life improvement, n. ECS0000009, presents the initial results of the development of a GIS-based historical database for landslide and flood analysis and hazard zonation in the “Costa Viola” area, Calabria region (South Italy).

The study area is located along the southern sector of the Tyrrhenian coast, encompasses the municipalities of Bagnara Calabra and Scilla. This area is recognized as one of the Calabria’s most important tourists destination. However, its specific geological and geomorphological features, combined with a high frequency of intense meteorological events, make it highly susceptible to geo-hydrological risks.

This work presents the most significant findings of a historical investigation into rainfall-induced landslide and floods and their impact on the transportation network over the past 120 years. Historical data were gathered from a wide range of documentary sources sources, including technical reports, historical archives, scientific literature, and newspapers.

In addition, the geodatabase includes geological and topographical, infrastructure maps, a Digital Elevation Model, pre-existing landslide inventory maps, and climatic data. After the implementation of the geodatabase and update of the inventory map, we explored the characteristics of the landslides, analyzing landslide distribution and creating a landslide density map. We also explored landslide frequency for lithology, soil types and several morphological attributes (elevation, slope gradient, slope curvature, etc.), considering both all landslides and classified landslide types. Furthermore, a density map of historically flooded areas during the study period was developed.

The first results indicate that the study area has been repeatedly affected by landslide events, primarily involving debris slides, rockfalls, and debris flows. These slope movements have caused significant damage to roads and railways crossing the study area and often represents a sort of continuum with high-bedload floods, characteristic of the typical ravines shaping the hydrographic network of this Mediterranean region. The research confirms the vulnerability of the area, with 175 damaging events recorded between 1911 and 2024, corresponding to an average frequency of approximately 1.5 damaging event per year. These events show both a tendency to recur in specific areas, as well as a significant rise in frequency over recent decades. This trend is likely influenced by several factors: an increased availability and reliability of information sources, heightened attention to the damaging phenomena, the expansion of elements at risk, and the effects climate change.