Daniele Giordan

Engineering Geology for Society and Territory - Volume 1

Dissociation of natural gas hydrate (NGH) in seabed can product amounts of gas. If the soil layer over NGH layer is permeable, gas will escape. Gas escape can on one hand lead to the damage of seabed, on the other hand lead to the decrease of the density of sea water and so threatens the structures nearby. In this paper movement and expansion behavior of gas in water was first studied, then the damage of seabed due to gas escape was studied. Effects of gas pressure, thickness of soil layer were investigated. The expansion angle of gas in the water was obtained. The characteristics of the hole size induced by gas escape with gas pressure and soil thickness were also obtained. These results can be as references of deeper research and practice.

ADVICE: A New Approach for Near-Real-Time Monitoring of Surface Displacements in Landslide Hazard Scenarios

We present a new method for near-real-time monitoring of surface displacements due to landslide phenomena, namely ADVanced dIsplaCement monitoring system for Early warning (ADVICE). The procedure includes: (i) data acquisition and transfer protocols; (ii) data collection, filtering, and validation; (iii) data analysis and restitution through a set of dedicated software; (iv) recognition of displacement/velocity threshold, early warning messages via SMS and/or emails; (v) automatic publication of the results on a dedicated webpage. We show how the system evolved and the results obtained by applying ADVICE over three years into a real early warning scenario relevant to a large earthflow located in southern Italy. ADVICE has speed-up and facilitated the understanding of the landslide phenomenon, the communication of the monitoring results to the partners, and consequently the decision-making process in a critical scenario. Our work might have potential applications not only for landslide monitoring but also in other contexts, as monitoring of other geohazards and of complex infrastructures, as open-pit mines, buildings, dams, etc.

Landslide failure forecast in near-real-time

We present a new method to achieve failure forecast of landslide phenomena by considering near-real-time monitoring data. Starting from the inverse velocity theory, we jointly analyse landslide surface displacements on different time windows, and apply straightforward statistical methods to obtain confidence intervals on the forecasted time of failure. Our results can be relevant to support the management of early warning systems during landslide emergency conditions, also when the predefined displacement and/or velocity thresholds are exceeded. In addition, our statistical approach for the definition of confidence interval and forecast reliability can be applied also to different failure forecast methods. We applied for the first time the herein presented approach in near-real-time during the emergency scenario relevant to the reactivation of the La Saxe rockslide, a large mass wasting menacing the population of Courmayeur, northern Italy, and the important European route E25. Our results show how the application of simplified but robust forecast models can be a convenient method to manage and support early warning systems during critical situations.

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.

Use of unmanned aerial vehicles in monitoring application and management of natural hazards

ABSTRACT The recent development of unmanned aerial vehicles (UAVs) has been increasing the number of technical solutions that can be used to monitor and map the effects of natural hazards. UAVs are generally cheaper and more versatile than traditional remote-sensing techniques, and they can be therefore considered as a good alternative for the acquisition of imagery and other physical parameters before, during and after a natural hazard event. This is an important added value especially for investigations over small areas (few km2). In the special issue ‘The use of Unmanned Aerial Vehicles in monitoring application and management of natural hazards’, we collected a number of case studies, aiming at providing a range of applications of monitoring and management of natural hazards assessed through the use of UAVs.

Landslide 3D Surface Deformation Model Obtained Via RTS Measurements

We present a new procedure that allows retrieving in near-real-time 3D surface deformation models starting from data acquired via Robotized Total Stations (RTS). The RTS measurements are first pre-processed and then implemented on 3D maps that include vector arrows representative of the intensities and of the real directions of motion in a given system of coordinates. The 3D surface deformation models are finally overlain on a DTM and/or on an updated picture of the monitored area. We discuss an example of application to an active large-scale landslide located in the area of Montaguto (southern Italy, ca. 100 km northeast from Naples). In this complex landslide scenario, the use of 3D representations of the surface deformation simplified the understanding of the evolution of the landslide phenomenon and received positive feedbacks from operators of the Italian Civil Protection Department.

UAV: Low-cost remote sensing for high-resolution investigation of landslides

The civilian use of small inexpensive mini- and micro-UAVs has increased dramatically in the past few years. UAVs can be used for natural hazards management. In this context, UAVs can be very useful for surveying and monitoring of active small landslides in urban environments. In this paper, a methodology for the data acquisition and processing that considers the landslide typology is presented and discussed. Two case studies from the northwest part of Italy are also described to illustrate the presented methodology.

The Use of Micro-UAV to Monitor Active Landslide Scenarios

We present a procedure to use micro-UAV (Unmanned Aerial Vehicles) to perform photogrammetry survey and monitoring analysis in landslide scenarios. The employed methodology is mainly composed of two phases: the first one is the UAV mission planning and execution, while the latter is the picture elaboration and alignment. The UAV used during all tests here described has been developed for photographic applications. Thanks to its “V” shape, propellers do not fall within camera field during normal flight operation and the eight motors configuration ensures more reliability in urban areas uses than a classical quadcopter configuration. The processing of the acquired photos relies on both standard photogrammetry procedure as well as innovative methods for photo alignment derived from computer vision algorithms. Examples of application are also provided to show the results and the potential of this methodology in real landslide scenarios.

Rockslide Monitoring Through Multi-temporal LiDAR DEM and TLS Data Analysis

The Mont de La Saxe rockslide (Courmayeur, Aosta Valley, Italy) is presently one of the most hazardous landslides in Northern Italy. Due to increasing activity in the last 5 years, the rockslide has been extensively investigated and monitored. We present topographic monitoring through ALS-LiDAR and TLS (Terrestrial Laser Scanning) surveys. This analysis is performed by visual comparison of LiDAR DEMs (1) in map and (2) profile format, and by the (3) elevation difference between successive DEMs. The efficacy of these three strategies depends on the rockslide kinematic, and the prevalence of either horizontal or vertical movements. In the first case, the visual comparison in map can be effective, while elevation difference is optimal to recognize prevalently vertical movements and areal extent of more active areas as well for a global zonation of the instability.

Relationship between man-made environment and slope stability: the case of 2014 rainfall events in the terraced landscape of the Liguria region (northwestern Italy)

ABSTRACT In the autumn of 2014, a series of rainfall events affected several sectors of the Liguria region, triggering many shallow landslides and causing three casualties and severe structural damages. The most intensely unstable area covered 385 km2, in which more than 1600 landslides have been identified. After these events, an airborne Light Detection and Ranging survey was carried out. The survey yielded a high-resolution digital terrain model (DTM) and aerial images that provided a means of identifying and mapping all the occurred landslides. The distribution analysis of slope instabilities highlighted the link with various human activities. In fact, the majority of the detected landslides occurred in man-modified areas. Geospatial and statistical analyses provided the identification of three main anthropic factors: terraces, their level of maintenance and road network. Moreover, they quantified their role in landslide triggering. These factors were not analysed as separate elements, but as a continuous process, overlapping in time, in man-made influence on landscape. The identification of such factors is a key element for a correct behaviour characterization of this landscape towards extreme flash floods events.