Alberico Sonnessa

Landslide hazard, monitoring and conservation strategy for the safeguard of Vardzia Byzantine monastery complex, Georgia

This paper reports preliminary results of a feasibility project developed in cooperation with National Agency for Cultural Heritage Preservation of Georgia, and aimed at envisaging the stability conditions of the Vardzia monastery slope (rupestrian city cave in the south-western Georgia). The aim is the implementation of a low-impact monitoring system together with long-term mitigation/conservation policies. A field analysis was conducted to reconstruct geometry of the rocky cliff, characteristics of discontinuities, main failure modes, and volume of potential unstable blocks and geomechanical parameters. Instability processes are the combination of causative factors such as the following: lithology, frequency and orientation of discontinuities, slope orientation, physical and mechanical characteristics of slope-forming materials, and morphological and hydrological boundary conditions. The combined adoption of different survey techniques (e.g., 3D laser scanner, ground-based radar interferometry) could be the best solution in the interdisciplinary field of cultural heritage preservation policies. The collected data will be the basis for future activities to be completed in collaboration with local authorities for a complete hazard and risk characterization for the monastery site and the development of an early warning system to allow safe exploitation for touristic activities and for historical site preservation.

Integrated Subaerial‐Submarine Morphological Evolution of the Sciara del Fuoco after the 2002 Landslide

In December 2002, an effusive eruption at Stromboli triggered a complex instability phenomenon, which affected both the subaerial and submarine portion of the Sciara del Fuoco slope, causing destructive landslide(s) and tsunami waves. Among the monitoring activities coordinated by the Italian Civil Defence Department, systematic photogrammetric and bathymetric surveys were carried out. Digital photogrammetry technique and multibeam soundings were used to obtain high-resolution digital elevation model of land and sea-floor surface of the NW flank of Stromboli (Sciara del Fuoco depression). Merging the subaerial and submarine data, and comparing multitemporal digital models, we first estimated the mass volumes involved in the failures of the subaerial and shallow submarine slope to be about 24 x 10 6 m 3 , and then, we monitored the continuous and relevant morphological changes induced by erosional―depositional processes during the various syneruptive and posteruptive stages. Filling processes of the scar by lava flow and debris and the morphological evolution of the slope in the 2 years after the event were described.

Terrestrial laser scanning survey in support of unstable slopes analysis: the case of Vulcano Island (Italy)

The capability to measure at distance dense cloud of 3D point has improved the relevance of geomatic techniques to support risk assessment analysis related to slope instability. This work focuses on quantitative analyses carried out to evaluate the effects of potential failures in the Vulcano Island (Italy). Terrestrial laser scanning was adopted to reconstruct the geometry of investigated slopes that is required for the implementation of numerical modeling adopted to simulate runout areas. Structural and morphological elements, which influenced past instabilities or may be linked to new events, were identified on surface models based on ground surveying. Terrestrial laser scanning was adopted to generate detailed 3D models of subvertical slopes allowing to characterize the distribution and orientation of the rock discontinuities that affect instability mechanism caused by critical geometry. Methods for obtaining and analyzing 3D topographic data and to implement simulation analyses contributing to hazard and risk assessment are discussed for two case studies (Forgia Vecchia slope and Lentia rock walls).

Landslide hazard assessment, monitoring and conservation of Vardzia monastery complex

Cultural heritage represents the legacy of human being to the planet earth. It is the evidence of 1,000 years of past generation evolution, to adapt our living condition to environment. Cultural heritage can be intangible (e.g. tradition, custom) and tangible, the latter including various physical objects, from historic landscapes and human transformed landscapes to sacred sites, archaeological sites, monumental sculpture, monumental painting, architecture and town planning. The above sites and remains are clearly not in equilibrium with environment. They are continuously impacted and weathered by several internal and external factors, both natural and human, with rapid and slow onset. Natural hazards are a clear example of such factors as well as long term weathering decay of rocks, until the effect of climate change, without disregarding the role of men, especially in war areas. In this context, an essential role on conservation and management of cultural properties has been identified by engineering geology and earth science in general. This approach was not very evident in the past, and now more attention to the integration of different sciences is demanded. Indeed, it is possible to affirm that the protection of the cultural heritage represents an interdisciplinary process (and not multi-disciplinary) at the border-line among art, history, science, policies for management and exploitation. In recent decades, many significant sites of cultural heritage have suffered damage, occasionally irreversible, from natural processes. This paper is presenting some case studies developed by United Nations Educational, Scientific and Cultural Organization (UNESCO) to protect and maintain important cultural heritage sites and historic urban landscapes, mainly in Country of the world recently involved in military conflicts or requiring international assistance and cooperation due to the dimension of the disaster or the relevance of threatened monument.The rock-cut city of Vardzia is a cave monastery site in south-western Georgia, excavated from the slopes of the Erusheti mountain on the left bank of the Mtkvari River. The main period of construction was the second half of the twelfth century. The caves stretch along the cliff for some eight hundred meters and up to fifty meters within the rocky wall. The monastery consists of more than six hundred hidden rooms spread over thirteen floors, which made possible to protect the monastery from the Mongol domination. The site was largely abandoned after the Ottoman takeover in the sixteenth century. The site is by the time affected by frequent slope instability processes along the entire volcanic tuff facade of the slope. Due to this phenomena the National Agency for Cultural Heritage Preservation of Georgia (NACHPG) has promoted, with the support of ISPRA, a landslide hazard assessment for the entire area through rock mechanics characterization, geotechnical engineering survey, geostructural and kinematic analysis, slope stability model, 3D laser scanner acquisitions and elaborations, and a real time monitoring system (GB_Radar interferometry) for the identification of deformation path of the most hazardous areas. A field analysis was conducted to reconstruct geometry of the rocky cliff, characteristics of discontinuities, main failure modes and volume of potential unstable blocks and geomechanical parameters.

Satellite Techniques: New Perspectives for the Monitoring of Dams

Dam deformation detection, analysis, and monitoring represent a growing issue for a large part of commercial companies and research groups at national and international levels. Although dam failures are usually sudden, in the majority of cases it is possible to predict when structural damage conditions might become serious.

Laser Scanning Analysis and Landslide Risk Assessment on Transportation Network: The Lugnano in Teverina (Umbria Region, Italy), Landslide Case Study

The present paper reports a multi-disciplinary team work, involving professionals, research institutes and public administration, for defining and applying low-impact techniques for risk assessment and mitigation of landslide areas. A study area located at Lugnano in Teverina (Umbria Region, Italy) and interested by landslides triggered by heavy rainfall and affecting important railway and road networks, was considered. A geological field survey has been carried out (including in situ and laboratory tests) in order to define strength parameters to be used in the stability analysis, for the detection of the most active area (residual risk) and implementation of preliminary design. In order to identify landslide surface and estimate the involved volumes, 3D laser scanner acquisition has been performed at different times. The obtained results stress the importance of performing different analysis in the light of reducing the impact of landslides on critical infrastructures by promoting low-environmental and sustainable solutions.

Stability Conditions and Evaluation of the Runout of a Potential Landslide at the Northern Flank of La Fossa Active Volcano, Italy

This paper focuses on the quantitative investigations carried out to evaluate stability conditions of the northern flank of the La Fossa cone (Vulcano Island) and the consequent runout of the debris avalanche that would be generated by a possible failure. The contribution describes first the geological setting and the typical instability phenomena of the area. Then it illustrates how the global morphology of the flank was reconstructed by combining aerial photogrammetry and high resolution 3D surveying techniques such as terrestrial laser scanner. The resulting digital elevation model (DEM) permitted us to extract and measure structural and morphological elements that drive and influence past and potential instabilities. These elements were used to constrain limit equilibrium analyses (LE) that were used to estimate the volume of soil mass susceptible of failure. Strength parameters at large scale were obtained from laboratory tests, described in previous studies, and back analyses of a past failure whose geometry was reconstructed from the DEM. Finally, results of runout analyses of the debris avalanche are presented and discussed. Analyses were conducted by using DAN-W and DAN-3D codes which allowed an estimate of the maximum runout distance and extension of the accumulation zone with respect to the inhabited area.

Monitoring urban area by means of long term DInSAR time series

The work is focused on the exploitation of the results of a DInSAR analysis applied to ERS-ENVISAT and CSM data. The derived data are adopted to implement a multilevel analysis approach to investigate built-up areas at wide and local scales. The adopted analysis is aimed at performing: a territorial analysis to evaluate the distribution of large-scale deformation processes; an aggregated analysis applied at settlement scale to identify critical areas by providing building classification maps; a single structure damage assessment, using semi-quantitative and quantitative models to evaluate the stability of a structure and the potential damage scenarios.

Quantifying the effects of ground settlement on buildings by the exploitation of long term DINSAR time series: The case of Roma

Differential Synthetic Aperture Radar Interferometry (DInSAR) is a well-established remote sensing methodology aimed at the analysis and monitoring of displacements due to the ground settlement or to the deformations of the structures. Among the DInSAR techniques, the Small BAseline Subset (SBAS) approach, working at different scales of investigations, permits to detect and control the deformation processes that may involve structures and infrastructures in urban areas. This work is focused on the exploitation of the results obtained by applying Small Baseline Subset (SBAS) technique of high resolution DInSAR analysis applied to ENVISAT and COSMO-SkyMed data. The DInSAR products (average velocity maps and time series of displacements) are adopted to implement and test a processing architecture to investigate the stability of built-up areas at regional and local scales.

Advanced DInSAR analysis for building damage assessment in large urban areas: an application to the city of Roma, Italy

Remote sensing data play an important role for the environmental monitoring because they allow to provide systematic information on very large areas and for a long period of time. Such information must be analyzed, validated and incorporated into proper modeling tools in order to become useful for performing risk assessment analysis. These approaches has been already applied in the field of natural hazard evaluation (i.e. for monitoring seismic, volcanic areas and landslides). However, not enough attention has been devoted to the development of validated methods for implementing quantitative analysis on civil structures. This work is dedicated to the comprehensive utilization of ERS / ENVISAT data store ESA SAR used to detect deformation trends and perform back-analysis of the investigated structures useful to calibrate the damage assessment models. After this preliminary analysis, SAR data of the new satellite mission (ie Cosmo SkyMed) were adopted to monitor the evolution of existent surface deformation processes and to detect new occurrence. The specific objective was to set up a data processing and data analysis chain tailored on a service that sustains the safe maintenance of the built-up environment, including critical construction such as public (schools, hospital, etc), strategic (dam, highways, etc) and also the cultural heritage sites. The analysis of the test area, in the southeastern sector of Roma, has provided three different levels and sub-levels of products from metropolitan area scale (territorial analysis), settlement scale (aggregated analysis) to single structure scale (damage degree associated to the structure).