The rock-cut city of Vardzia is an example of the extraordinary rupestrian cultural heritage of Georgia. The site, Byzantine in age, was carved in the steep tuff slopes of the Erusheti mountains, and due to its peculiar geological characteristics, it is particularly vulnerable to weathering and degradation, as well as frequent instability phenomena. These problems determine serious constraints on the future conservation of the site, as well as the safety of the visitors. This paper focuses on the implementation of a site-specific methodology, based on the integration of advanced remote sensing techniques, such as InfraRed Thermography (IRT) and Unmanned Aerial Vehicle (UAV)-based Digital Photogrammetry (DP), with traditional field surveys and laboratory analyses, with the aim of mapping the potential criticality of the rupestrian complex on a slope scale. The adopted methodology proved to be a useful tool for the detection of areas of weathering and degradation on the tuff cliffs, such as moisture and seepage sectors related to the ephemeral drainage network of the slope. These insights provided valuable support for the design and implementation of sustainable mitigation works, to be profitably used in the management plan of the site of Vardzia, and can be used for the protection and conservation of rupestrian cultural heritage sites characterized by similar geological contexts.

A deterministic distributed model has been developed for large-scale debris-flow hazard analysis in the basin of River Vezza (Tuscany Region – Italy). This area (51.6 km 2 ) was affected by over 250 landslides. These were classified as debris/earth flow mainly involving the metamorphic geological formations outcropping in the area, triggered by the pluviometric event of 19 June 1996. In the last decades landslide hazard and risk analysis have been favoured by the development of GIS techniques permitting the generalisation, synthesis and modelling of stability conditions on a large scale investigation (>1:10 000). In this work, the main results derived by the application of a geotechnical model coupled with a hydrological model for the assessment of debris flows hazard analysis, are reported. This analysis has been developed starting by the following steps: landslide inventory map derived by aerial photo interpretation, direct field survey, generation of a database and digital maps, elaboration of a DTM and derived themes (i.e. slope angle map), definition of a superficial soil thickness map, geotechnical soil characterisation through implementation of a backanalysis on test slopes, laboratory test analysis, inference of the influence of precipitation, for distinct return times, on ponding time and pore pressure generation, implementation of a slope stability model (infinite slope model) and generalisation of the safety factor for estimated rainfall events with different return times. Such an approach has allowed the identification of potential source areas of debris flow triggering. This is used to detected precipitation events with estimated return time of 10, 50, 75 and 100 years. The model shows a dramatic decrease of safety conditions for the simulation when is related to a 75 years return time rainfall event. It corresponds to an estimated cumulated daily intensity of 280–330 mm. This value can be considered the hydrological triggering threshold for the whole Vezza basin.

An inventory-based method for the assessment of landslide susceptibility is presented in this article. The method has been tested in the Virginio River Basin, a tributary of the Arno River whose confluence is located about 20 km downstream from Florence (Italy). The scope of this study includes setting up a procedure for landslide hazard zoning to be applied by those urban planners typically working on small areas at large scale. The proposed method deals with traditional and well-known landslide hazard analyses, based on geomorphological tools, and its most original contribution is represented by the attempt to carry out and apply a technique for landslide hazard assessment that takes into account two different scales of analysis. The basis of a detailed landslide inventory and the first phase of this research was an in-depth geomorphological investigation at basin scale (1:25,000–1:10,000). This was aimed at indicating the most important factors influencing the landslide processes within the area, which also turned out to be the most generally accepted factors: a) slope gradient in which the landslide originated, b) lithology, and c) land cover. Once those factors were defined as thematic vector data, they were expressed using GIS overlay mapping, allowing the identification, for the entire Virginio River basin, of first-order homogeneous domains (Unique Condition Units, UCUs) that contain, for each landslide type, unique combinations (domains) of the selected hillslope stability factors. The domains are the basic Terrain Units for the subsequent landslide susceptibility assessment and mapping, which was carried out at slope scale (1:10,000–1:2,000). Landslide factors not identified in the first phase of analysis, but considered to have played an important role in contributing to the activation of the mass movements, so-called second-order landslide preparatory factors, have been taken into account in the second phase of the analysis. Once mapped and spatially referenced, these factors were overlain by vector-based GIS techniques to define second-order UCUs which, in turn, constituted the basis of a landslide susceptibility function. Essentially, this is a logic function based on the presence/absence of preparatory factors and slope instability indicators within previously selected Unique Condition Terrain Units. The final mapping of the areas characterized by different landslide susceptibility levels was performed by vector- and raster-based GIS techniques on the basis of the number and rank of the preparatory factors. The final landslide susceptibility classes, defined by a logical and easily replicable procedure, are considered to be useful in the decision-making procedures associated with territorial planning.