Paolo Allasia

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 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.

A Low-Cost Optical Remote Sensing Application for Glacier Deformation Monitoring in an Alpine Environment

In this work, we present the results of a low-cost optical monitoring station designed for monitoring the kinematics of glaciers in an Alpine environment. We developed a complete hardware/software data acquisition and processing chain that automatically acquires, stores and co-registers images. The system was installed in September 2013 to monitor the evolution of the Planpincieux glacier, within the open-air laboratory of the Grandes Jorasses, Mont Blanc massif (NW Italy), and collected data with an hourly frequency. The acquisition equipment consists of a high-resolution DSLR camera operating in the visible band. The data are processed with a Pixel Offset algorithm based on normalized cross-correlation, to estimate the deformation of the observed glacier. We propose a method for the pixel-to-metric conversion and present the results of the projection on the mean slope of the glacier. The method performances are compared with measurements obtained by GB-SAR, and exhibit good agreement. The system provides good support for the analysis of the glacier evolution and allows the creation of daily displacement maps.

Assessment of the behavior of an active earth-slide by means of calibration between numerical analysis and field monitoring

The assessment of hazards associated with active landslides and the related risk management takes advantage nowadays of using the integration of information arising from field monitoring data, including both displacement data, at ground surface and at depth, and pore pressure measurements well distributed throughout the landslide area, along with the results of numerical models. This paper provides an example of the application of this methodological approach to a case study represented by an active sector of the large Montaguto earthslide, located in the Italian Southern Apennines, which has shown in recent years a continuous slow movement, despite the draining interventions executed in 2011 and the general stability of the other portions of the earthslide. The near real-time topographic monitoring network installed in 2010 shows the presence of different kinematic sectors within the same landslide body, characterised by different velocities and evolution trends. After the proper emergency phase occurred in 2010, a specific area has still shown in 2011 and 2012 clear signs of activity, with acceleration stages generally recorded in the Spring. In order to explore the factors that presumably control the activity of this landslide sector, a two-dimensional finite element model has been developed by using PLAXIS-2D code. Based on the available geological information, pore water pressure measurements and soil geotechnical properties, the numerical results indicate the role of geometry of the landslide mass in sector E as a factor promoting the instability of this specific area. The numerical results are in good agreement with the displacement field measured throughout the landslide channel and confirm that numerical modelling can represent a reliable support for the interpretation of the landslide failure mechanism and the corresponding evolution, when calibrated against the in situ landslide behaviour reconstructed through a monitoring system.

The Use of Airborne LiDAR Data in Basin-Fan System Monitoring: An Example from Southern Calabria (Italy)

To analyse morphologic and volumetric changes within an active basin-fan system of about 0.250 km2 in Calabria (South Italy), we compare two high-resolution DTMs (50 cm) derived from aerial LiDAR surveys conducted in October 2012 and May 2013. The comparison allowed us to: (i) evaluate the magnitude of erosion-transport-sedimentation processes (ii) identify the extent of an active landslide within the feeder sub-basin, and (iii) confirm the fan, feeder channel and feeder basin dynamics obtained from previous works based on geological and geomorphological field surveys. The results demonstrate that the LiDAR techniques can be a useful tool for the monitoring of geomorphological changes in areas affected by severe erosion and depositional processes.

The Differential Slow Moving Dynamic of a Complex Landslide: Multi-sensor Monitoring

Monitoring is essential to understand the mechanics of landslides, and predict their behavior in time and space. In this work we discuss the performance of multi-sensor monitoring techniques applied to measure the kinematics and the landslide hydrology of Portalet landslide complex, which is located in the SW-facing slopes of Petrasos peak at the border between Spain and France. In the summer 2004, the excavation of a parking lot at the foot of the slides triggered a secondary failure in the lower part of the slope, accelerating the dynamic of the landslide complex. The deployed hydro-meteorological network has been useful to understand that the greatest infiltration in the moving mass is produced in spring due to the combination of snow melt and seasonal rainfall. Landslide surface kinematics measured with differential GPS (D-GPS) were useful to measure the slower (<10 cm/year) and faster (20–30 cm/year) dynamic of the landslide complex. Advanced DInSAR was useful to monitor the slower ground displacements from long datasets of SAR images, providing a wider spatial coverage and measurement point density than the D-GPS. In addition, the NL-InSAR processing strategy was applied to monitor the faster motion using short datasets of TerraSAR-X images excluding the snow cover period. The installed horizontal extensometers were useful to study the extension of the head scarp and its relationship with landslide hydrology, which is affected by the retrogressive effect of the landslide due to the loss of lateral confining pressure. Finally, an inclinometric robot system (AIS) was the only technique capable of detecting 5–6 time faster motion after the snow melt, since it provides daily measurements with high accuracy even during the snow cover period. These data, even if expensive to gather, are necessary to improve the hydro-mechanical modeling of large slow landslides, such as those already proposed for Portalet landslide complex.

Monitoring Alpine glacier surface deformations with GB-SAR

ABSTRACT We present methods and results from interferometric data processing of a long-lasting survey campaign monitoring the Planpincieux glacier, located on the Italian side of the Mont Blanc, using a ground-based synthetic aperture radar (GB-SAR). Monitoring a European Alpine glacier during the winter, when the meteorological conditions are highly variable, presents some difficulties in radar data interpretation. The main issues to tackle in interferometric processing are unwrapping errors and high amplitude dispersion (DA), mainly due to the high velocity and dielectric heterogeneity of the backscattering surface. To improve the reliability of the results, a coherence-driven pixel-selection criterion for identifying the glacier area and a simple approach to reduce possible unwrapping errors in interferograms with low coherence are here proposed. The development of a new 2D polynomial regression model, as a function of elevation, for atmospheric phase screen (APS) estimation is also discussed. A comparison with the results obtained with a vision-based approach gave showed good agreement.

Infrastructure in Geohazard Contexts: The Importance of Automatic and Near-Real-Time Monitoring

The analysis and interpretation of ground deformation plays an important role in monitoring activities aimed at ensuring the safety of people and/or infrastructure in geohazard scenarios such as earthquakes, volcanic activity and landslides. Nowadays, a wide spectrum of instruments and methods is available, ranging from in-situ to remote sensing approaches. However, the research described here was primarily to develop automatic, and increasingly accurate, monitoring instruments, while acknowledging that the available tools for an efficient exploitation, understanding and interpretation of the measurements made still lack efficiency.