Paolo Mazzanti

SCIDDICA-SS3: a new version of cellular automata model for simulating fast moving landslides

Cellular Automata (CA) are discrete and parallel computational models useful for simulating dynamic systems that evolve on the basis on local interactions. Some natural events, such as some types of landslides, fall into this type of phenomena and lend themselves well to be simulated with this approach. This paper describes the latest version of the SCIDDICA CA family models, specifically developed to simulate debris-flows type landslides. The latest model of the family, named SCIDDICA-SS3, inherits all the features of its predecessor, SCIDDICA-SS2, with the addition of a particular strategy to manage momentum. The introduction of the latter permits a better approximation of inertial effects that characterize some rapid debris flows. First simulations attempts of real landslides with SCIDDICA-SS3 have produced quite satisfactory results, comparable with the previous model.

First insights on the potential of Sentinel-1 for landslides detection

ABSTRACT This paper illustrates the potential of Sentinel-1 for landslide detection, mapping and characterization with the aim of updating inventory maps and monitoring landslide activity. The study area is located in Molise, one of the smallest regions of Italy, where landslide processes are frequent. The results achieved by integrating Differential Synthetic Aperture Radar Interferometry (DInSAR) deformation maps and time series, and Geographical Information System (GIS) multilayer analysis (optical, geological, geomorphological, etc.) are shown. The adopted methodology is described followed by an analysis of future perspectives. Sixty-two landslides have been detected, thus allowing the updating of pre-existing landslide inventory maps. The results of our ongoing research show that Sentinel-1 might represent a significant improvement in terms of exploitation of SAR data for landslide mapping and monitoring due to both the shorter revisit time (up to 6 days in the close future) and the wavelength used, which determine an higher coherence compared to other SAR sensors.

Modelling Combined Subaerial-Subaqueous Flow-Like Landslides by Cellular Automata

Macroscopic Cellular Automata characterize a methodological approach for modelling large scale (extended for kilometres) complex acentric phenomena, e.g. surface flows as lava flows, debris flows etc.. This paper concerns the extension of such a method in order to simulate combined subaerial-subaqueous flow-like landslides. The occurrence of heterogeneous interacting processes requires a more physical description of the energy balance and an explicit velocity management. The model SCIDDICA-SS2 proposes some empirical solutions, such as the computation at each step and inside each cell, of departing flows which are characterized by their mass centre position and velocity. An application to combined subaerial-subaqueous landslide is exhibited together with simulation results of the 1997 Albano lake (Rome, Italy) debris flow.

Basin Scale Assessment of Landslides Geomorphological Setting by Advanced InSAR Analysis

An extensive investigation of more than 90 landslides affecting a small river basin in Central Italy was performed by combining field surveys and remote sensing techniques. We thus defined the geomorphological setting of slope instability processes. Basic information, such as landslides mapping and landslides type definition, have been acquired thanks to geomorphological field investigations and multi-temporal aerial photos interpretation, while satellite SAR archive data (acquired by ERS and Envisat from 1992 to 2010) have been analyzed by means of A-DInSAR (Advanced Differential Interferometric Synthetic Aperture Radar) techniques to evaluate landslides past displacements patterns. Multi-temporal assessment of landslides state of activity has been performed basing on geomorphological evidence criteria and past ground displacement measurements obtained by A-DInSAR. This step has been performed by means of an activity matrix derived from information achieved thanks to double orbital geometry. Thanks to this approach we also achieved more detailed knowledge about the landslides kinematics in time and space.

Development and calibration of a preliminary cellular automata model for snow avalanches

Numerical modelling is a major challenge in the prevention of risks related to the occurrence of catastrophic phenomena. A Cellular Automata methodology was developed for modelling large scale (extended for kilometres) dangerous surface flows of different nature such as lava flows, pyroclastic flows, debris flows, rock avalanches, etc. This paper presents VALANCA, a first version of a Cellular Automata model, developed for the simulations of dense snow avalanches. VALANCA is largely based on SCIDDICA-SS2, the most advanced model of the SCIDDICA family developed for flow-like landslides. VALANCA adopts several of its innovations: outflows characterized by their mass centre position and explicit velocity. First simulations of real past snow avalanches occurred in Switzerland in 2006 show a satisfying agreement, concerning avalanche path, snow cover erosion depth and deposit thickness and areal distribution.

Forecasting methods for landslides interacting with infrastructures

Few years ago, during the start-up works for the realization of a tunnel entrance, a shallow translational landslide occurred. Following this event detailed engineering-geological surveys of the slope were performed and an integrated monitoring system, including also a Terrestrial SAR Interferometer (TInSAR), was built. Based on the time series of displacement semi-empirical approach was applied to the anchored bulkheads. Simultaneously an engineering-geology model was devised for a stress–strain numerical analysis which was performed by the finite difference code FLAC 6.0.

A New Approach Based on Terrestrial Remote-sensing Techniques for Rock Fall Hazard Assessment

Remote-sensing techniques are changing the way of investigating the Earth and its surface processing. Among these, rock fall from vertical cliffs are very frequent and difficult to be investigated because they frequently occur from inaccessible places. At this regard, terrestrial remote-sensing techniques represent a great opportunity for investigating inaccessible cliffs from a remote position. In this paper, a new approach for the investigation of rock cliff and the prioritization of rock fall hazard based on data collected by remote-sensing techniques has been developed and applied to a real coastal cliff located in the southern part of Italy. By the herein presented approach, data derived from a survey performed by the combination of terrestrial laser scanner, ground-based SAR interferometry and infrared thermography are used in order to identify both predisposing factors (mapping of discontinuities) and state of activity indicators of rock instabilities. Hence, a prioritizations map of the cliff in terms of stability interventions is achieved that can be easily used by local authorities in charge of land management.

The Dynamics of Subaqueous Rock Avalanches: The Role of Dynamic Fragmentation

Rock and debris-avalanches are catastrophic failures occurring both on land and in the subaqueous environment. The apparent friction coefficient of subaqueous rock avalanches is significantly greater than that of debris flows of the same volume. We argue that this is the consequence of the presence of large fragments in a travelling rock avalanche, which affects both the drag coefficient and the capability of hydroplaning. We suggest that the presence of water damps the fragmentation of the subaqueous rock avalanches, as indicated by the presence of much larger blocks in the deposits of subaqueous rock avalanches compared to the subaerial ones. We present simple estimates to evaluate the disintegration rates during the flow in the two different environments and we found that this is strongly reduced in water mainly due to: (1) reduction of inter-granular impact energy; (2) smoother topography in subaqueous landscape; (3) lower velocities reached due to the water resistance.

Peculiar Morphologies of Subaqueous Landslide Deposits and Their Relationship to Flow Dynamics

The morphology of subaqueous landslide deposits is seldom analyzed quantitatively or at least semi-quantitatively with regard to the dynamics of the flow. However, the peculiar morphology of the deposits can reveal information on the mechanics of propagation of the mass movement and on the mechanism of emplacement. Horseshoe-shaped deposits and oriented blocks are two peculiar morphologies of subaqueous landslide which have been identified in this paper. Both morphologies have been described in a qualitative way by considering the shape of the deposit and the geomorphological features of the areas of emplacement. Furthermore, these morphologies have been analyzed in a quantitative way by means of mathematical and numerical approaches. The close relationship between these morphologies and the landslide mechanism of propagation and emplacement has been thus preliminary demonstrated by accounting for the interaction between moving mass and the ambient fluid.

Imaging Multi-Age Construction Settlement Behaviour by Advanced SAR Interferometry

This paper focuses on the application of Advanced Satellite Synthetic Aperture Radar Interferometry (A-DInSAR) to subsidence-related issues, with particular reference to ground settlements due to external loads. Beyond the stratigraphic setting and the geotechnical properties of the subsoil, other relevant boundary conditions strongly influence the reliability of remotely sensed data for quantitative analyses and risk mitigation purposes. Because most of the Persistent Scatterer Interferometry (PSI) measurement points (Persistent Scatterers, PSs) lie on structures and infrastructures, the foundation type and the age of a construction are key factors for a proper interpretation of the time series of ground displacements. To exemplify a methodological approach to evaluate these issues, this paper refers to an analysis carried out in the coastal/deltaic plain west of Rome (Rome and Fiumicino municipalities) affected by subsidence and related damages to structures. This region is characterized by a complex geological setting (alternation of recent deposits with low and high compressibilities) and has been subjected to different urbanisation phases starting in the late 1800s, with a strong acceleration in the last few decades. The results of A-DInSAR analyses conducted from 1992 to 2015 have been interpreted in light of high-resolution geological/geotechnical models, the age of the construction, and the types of foundations of the buildings on which the PSs are located. Collection, interpretation, and processing of geo-thematic data were fundamental to obtain high-resolution models; change detection analyses of the land cover allowed us to classify structures/infrastructures in terms of the construction period. Additional information was collected to define the types of foundations, i.e., shallow versus deep foundations. As a result, we found that only by filtering and partitioning the A-DInSAR datasets on the basis of the above-mentioned boundary conditions can the related time series be considered a proxy of the consolidation process governing the subsidence related to external loads as confirmed by a comparison with results from a physically based back analysis based on Terzaghi’s theory. Therefore, if properly managed, the A-DInSAR data represents a powerful tool for capturing the evolutionary stage of the process for a single building and has potential for forecasting the behaviour of the terrain–foundation–structure combination.