Natural hazards, human factors, and "ghost towns": a multi-level approach

The abandonment of inhabited places is a phenomenon that concerns many countries worldwide and Italy particularly where a large number of deserted settlements are hosted. Many are the factors driving and conditioning the abandonment of a site, such as natural extreme events (e.g. earthquakes, landslides, and floods) and/or human (not) actions. Once the site is abandoned, the built-up area experiences a progressive physical decay so posing problems about the policies to be adopted to manage andmaintain the buildings (or their ruins). That being stated, the article proposes an integrated methodological approach to analyse both the natural/human factors causing the abandonment of settlements and conservation state of deserted places over time. To test themethodology,we considered the old town of Craco (Basilicata, Southern Italy) as a case study. That “ghost town”, whose fascinating urban and natural landscapes have been the set of numerous international films, was gradually transferred to other two places since the 1960s due to the landslides that have affected the site over the centuries. Three were the explicit key aims of the research. The first was to scrutinise the activations/ reactivations of the landslides jointly with their effects on the built environment so to critical go over the actions put into the field by the institutions to mitigate the hydrogeological risk. The second was to examine whether and how the landslide occurrences conditioned the urban growth of the Craco over time. The third was to investigate in relation to the vegetation growth in the Craco downtown over the last 15 years or so, to infer clues on future decay trends and conservation strategies of the built environment. The purposes were reached considering a geological-geomorphological, historical, and remote-sensing approach. In detail, the first goal was met (re)considering a cross-correlated analysis, in diachronic key, of edited/unedited archive sources with geological/geomorphological perspectives. The second was followed up performing the analysis of the Craco urban growth over the centuries and correlating it with the history of landslide occurrences. The third target was pursued by means of NDVI (Normalized Difference Vegetation Index) time series obtained from Landsat TM and Sentinel 2 data along with HSV (Hue, Saturation, Value) colour system techniques applied to multi-date Google Earth photos. From the perspective angle, the results of this research can contribute to setup proper resilience strategies for sites subject to hydrogeological hazard similar to that affects Craco, thus helping to identify conservation plans as well as enhancement policies of “ghost towns”.