Terraced Landscapes on Portofino Promontory (Italy): Identification, Geo-Hydrological Hazard and Management

Abstract

Stone wall terraces are a largely investigated topic in research for both their landscape and cultural/historical value. Terraces are anthropogenic landforms that interact with natural processes and need permanent maintenance to preserve their functionality. In the Mediterranean region, ground effects related to intense rain events often involve terraced slopes that, in some situations, are directly sourced areas of debris/mud flow. Starting from the 1950s, the changing socio-economic conditions caused the abandonment of large portions of rural areas. Nowadays, at the catchment scale, it is frequently difficult recognizing stone wall terraces because of their abandonment and the uncontrolled re-vegetation. This research faces the issue of identifying terraces in the Monte di Portofino promontory, which is internationally famous for its high-value natural and landscape involving broad anthropogenic modifications dating back to the Middle Ages. A remote sensing application, with LIDAR data and orthophotography, identified terraces on the Portofino promontory, enabling investigating even barely accessible areas and increasing knowledge on the territory. The aim of this paper is first of all to point out the presence of such anthropogenic morphologies in the promontory of Monte di Portofino and then to asses and highlight the related hazard. In fact, terraces can be a source of debris/hyper-concentrated flow with highly damaging power, as occurred in the recent years in neighboring areas during particularly intense hydrological events. Then, terraced area mapping, including in use and in abandonment information, is crucial to perform a spatial relationship analysis that includes hazard-exposed elements and to evaluate the possible connectivity factor of buildings, infrastructures, tourism facilities and Cultural Heritage within the hydrographical network.