A new procedure for an effective management of geo-hydrological risks across the "Sentiero Verde-Azzurro" trail, Cinque Terre National Park, Liguria (North-Western Italy)

In recent years, Cinque Terre National Park, one of the most famous UNESCO sites in Italy, experienced a significant increase in tourist visits. This unique landscape is the result of the rough morphology of a small coastal basin with a very steep slope and a long-term human impact, mainly represented by anthropic terraces. This setting promotes the activation of numerous geo-hydrological instabilities, primarily related to heavy rainfall events that often affect this area. Currently, the main challenge for the administrators of Cinque Terre National Park is the correct maintenance of this environment along with the functional management of the hiking trail to ensure the safety of tourists. The definition of a methodology for effective management is mandatory for the sustainable administration of this unique site. We implement a new codified procedure based on the combined use of the Operative Monography and the Survey Form, focusing on the "Sentiero Verde-Azzurro" trail, for a proper description of the known landslides affecting the trail and the identification of damage and/or landslides activated by critical meteorological events. This guarantees effective geo-hydrological risk management, which is also applicable to other similar sites in a unique environmental and cultural heritage site such as Cinque Terre Park

Shallow landslide susceptibility, Rupinaro catchment, Liguria (northwestern Italy)

The shallow landslides assessment is a hard task in territories featuring composite influence of natural and anthropic factors. In Liguria region (northwestern Italy), the landscape presents widespread human intervention prevalently represented by terraces. The assessment of predisposing factors in such landscape deserve a multidisciplinary approach. We implemented a classification methodology based on the Analytical Hierarchy Process. In GIS environment we overlaid several layers: (i) slope, (ii) land use, (iii) lithology, and (iv) aspect. Slope and aspect have been computed on a filtered (based on TPI) high-resolution DTM with the removal of terraces, in order to obtain the pristine slope pattern. Each spatial data was then reclassified according to the weighting procedures thus producing a landslide susceptibility map. This methodology represents a starting point for the correct assessment of shallow landslides occurrence, capable to generate a map, taking in account of the peculiar features of this extremely man-made territory

Structure from Motion Multisource Application for Landslide Characterization and Monitoring: The Champlas du Col Case Study, Sestriere, North-Western Italy

Structure from Motion (SfM) is a powerful tool to provide 3D point clouds from a sequence of images taken from different remote sensing technologies. The use of this approach for processing images captured from both Remotely Piloted Aerial Vehicles (RPAS), historical aerial photograms, and smartphones, constitutes a valuable solution for the identification and characterization of active landslides. We applied SfM to process all the acquired and available images for the study of the Champlas du Col landslide, a complex slope instability reactivated in spring 2018 in the Piemonte Region (north-western Italy). This last reactivation of the slide, principally due to snow melting at the end of the winter season, interrupted the main road used to reach Sestriere, one of the most famous ski resorts in north-western Italy. We tested how SfM can be applied to process high-resolution multisource datasets by processing: (i) historical aerial photograms collected from five diverse regional flights, (ii) RGB and multi-spectral images acquired by two RPAS, taken in different moments, and (iii) terrestrial sequences of the most representative kinematic elements due to the evolution of the landslide. In addition, we obtained an overall framework of the historical development of the area of interest, and distinguished several generations of landslides. Moreover, an in-depth geomorphological characterization of the Champlas du Col landslide reactivation was done, by testing a cost-effective and rapid methodology based on SfM principles, which is easily repeatable to characterize and investigate active landslides

Operative Monographies: Development of a New Tool for the Effective Management of Landslide Risks

Active landslide risk assessment and management are primarily based on the availability of dedicated studies and monitoring activities. The establishment of decision support for the efficient management of active landslides threatening urban areas is a worthwhile contribution. Nowadays, consistent information about major landslide hazards is obtained through an interdisciplinary approach, consisting of field survey data and long-time monitoring, with the creation of a high populated dataset. Nevertheless, the large number and variety of acquired data can generate some criticalities in their management. Data fragmentation and a missing standard format of the data should represent a serious hitch in landslide hazard management. A good organization in a standard format can be a good operative solution. Based on standardized approaches such as the ICAO (International Civil Aviation Organization), we developed a standard document called operative monography. This document summarizes all available information by organizing monitoring data and identifying possible lacks. We tested this approach in the Aosta Valley Region (NW Italy) on five different slow moving landslides monitored for twenty years. The critical analysis of the available dataset modifies a simple sequence of information in a more complex document, adoptable by local and national authorities for a more effective management of active landslides

An Open-Source Web Platform to Share Multisource, Multisensor Geospatial Data and Measurements of Ground Deformation in Mountain Areas

Nowadays, the increasing demand to collect, manage and share archives of data supporting geo-hydrological processes investigations requires the development of spatial data infrastructure able to store geospatial data and ground deformation measurements, also considering multisource and heterogeneous data. We exploited the GeoNetwork open-source software to simultaneously organize in-situ measurements and radar sensor observations, collected in the framework of the HAMMER project study areas, all located in high mountain regions distributed in the Alpines, Apennines, Pyrenees and Andes mountain chains, mainly focusing on active landslides. Taking advantage of this free and internationally recognized platform based on standard protocols, we present a valuable instrument to manage data and metadata, both in-situ surface measurements, typically acquired at local scale for short periods (e.g., during emergency), and satellite observations, usually exploited for regional scale analysis of surface displacement. Using a dedicated web-interface, all the results derived by instrumental acquisitions and by processing of remote sensing images can be queried, analyzed and downloaded from both expert users and stakeholders. This leads to a useful instrument able to share various information within the scientific community, including the opportunity of reprocessing the raw data for other purposes and in other contexts

Definition of an Operative Methodology for the Management of Rockfalls along with the Road Network

Rockfalls are widespread events in mountain areas worldwide. The management of this process can be done using different approaches. In this paper, we want to analyze the procedure that can be adopted to manage a rockfall event considering the safety of infrastructure and settlements. Focusing on an Alpine region highly affected by rockfalls like the Aosta Valley Region (north-western Italy), we implemented a dedicated procedure for the road network emergency management. This procedure can be activated immediately after a rockfall, and it aims to identify the effect of the collapse, define the danger zone, plan the recovery project and propose temporary solutions for correct residual risk management until the end of the remedial works. In natural hazards, the lack of codified methods can create critical conditions and increase the responsibility of the single operators, who have to effectively manage a critical situation in a limited amount of time without a well-defined procedure. For this reason, the proposed method aims to be a first example of how a correct codification can be used for more sustainable management of this widespread phenomenon

Structural analysis of San Leo (RN, Italy) east and north cliffs using 3D point clouds

The town of San Leo, like many others in the historical region of Montefeltro (Northern Apennines, Italy), was built in medieval period on a calcarenite and sandstone slab, bordered by subvertical and overhanging cliffs up to 100 m high, for defense purposes. The slab and the underlying clayey substratum show widespread landslide phenomena: the first is tectonized and crossed by joints and faults, and it is affected by lateral spreading with associated rock falls, topples and tilting. Moreover, the underlying clayey substratum is involved in plastic movements, like earth flows and slides. The main cause of instability in the area, which brings about these movements, is the high deformability contrast between the plate and the underlying clays. The aim of our research is to set up a numerical model that can well describe the processes and take into account the different factors that influence the evolution of the movements. One of these factors is certainly the structural setting of the slab, characterized by several joints and faults; in order to better identify and detect the main joint sets affecting the study area a structural analysis was performed. Up to date, a series of scans of San Leo cliff taken in 2008 and 2011, with a Riegl Z420i were analyzed. Initially, we chose a test area, located in the east side of the cliff, in which analyses were performed using two different softwares: COLTOP 3D and Polyworks. We repeated the analysis using COLTOP for all the east wall and for a part of the north wall, including an area affected by a rock fall in 2006. In the test area we identified five sets with different dips and dip directions. The analysis of the east and north walls permitted to identify eight sets (seven plus the bedding) of discontinuities. We compared these results with previous ones from surveys taken by others authors in some areas and with some preliminary data from a traditional geological survey of the whole area. With traditional methods only a limited number of measurements can be collected, and in small areas, that often are not representative of the entire rock mass. In this case, some of the discontinuities are located only in specific parts of the rock mass, thus resulting difficult to be detected with a classical survey. Moreover, certain sets are identifiable only in the uppermost or lowermost part of the cliff, and change their orientation along the surface. For this reason, the integration of classical and innovative surveying techniques can be really useful. TLS survey and structural software analysis can help to understand which sets are really determinant for the structural description of the slab at the slope scale and therefore for the stability of the cliffs. We are planning to complete the TLS survey all around the cliff, to obtain a full 3D model of the rock slab, to be used for numerical modelling. All the obtained results are validated with a site-survey, which is in progress at the moment

Taking Advantage of the ESA G-POD Service to Study Ground Deformation Processes in High Mountain Areas: A Valle d’Aosta Case Study, Northern Italy

This paper presents a methodology taking advantage of the GPOD-SBAS service to study the surface deformation information over high mountain regions. Indeed, the application of the advanced DInSAR over the arduous regions represents a demanding task. We implemented an iterative selection procedure of the most suitable SAR images, aimed to preserve the largest number of SAR scenes, and the fine-tuning of several advanced configuration parameters. This method is aimed at minimizing the temporal decorrelation effects, principally due to snow cover, and maximizing the number of coherent targets and their spatial distribution. The methodology is applied to the Valle d’Aosta (VDA) region, Northern Italy, an alpine area characterized by high altitudes, complex morphology, and susceptibility to different mass wasting phenomena. The approach using GPOD-SBAS allows for the obtainment of mean deformation velocity maps and displacement time series relative to the time period from 1992 to 2000, relative to ESR-1/2, and from 2002 to 2010 for ASAR-Envisat. Our results demonstrate how the DInSAR application can obtain reliable information of ground displacement over time in these regions, and may represent a suitable instrument for natural hazards assessment.ISSN:2072-429