Relationships between geo-hydrological processes induced by heavy rainfall and land-use: the case of 25 October 2011 in the Vernazza catchment (Cinque Terre, NW Italy)

On 25 October 2011, heavy rainfall affected an area of ca. 1000 km2 between eastern Liguria and northern Tuscany (northwest Italy). The event caused floods, hundreds of shallow landslides, four casualties and severe structural and economic damage in Monterosso and Vernazza villages. The distribution of geo-hydrological processes triggered by rainfall in relation to land-use was analyzed in the Vernazza catchment. Both, an inventory map of geo-hydrological processes and a land-use map were prepared through air photo-analysis and field surveys; a derivative map combining these two outputs provides insight into the relationships between geo-hydrological processes and land-use. The density of shallow landslides (n/km2) and the frequency of erosional processes (%) are higher in terraced areas compared to other land-use classes. The study highlights the high vulnerability of agricultural terraces which, over the centuries, have been a fundamental tool for the prevention and control of erosional processes and slope instability.