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MARCO MULAS

Ricercatore t.d. art. 24 c. 3 lett. B
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche


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Pubblicazioni

2023 - Contamination exposure assessment of a well field through Null-Space Monte Carlo method [Articolo su rivista]
Critelli, Vincenzo; Ronchetti, Francesco; Mulas, Marco; Corsini, Alessandro; Brozzo, Giampiero
abstract


2023 - Detecting Recent Dynamics in Large-Scale Landslides via the Digital Image Correlation of Airborne Optic and LiDAR Datasets: Test Sites in South Tyrol (Italy) [Articolo su rivista]
Tondo, M; Mulas, M; Ciccarese, G; Marcato, G; Bossi, G; Tonidandel, D; Mair, V; Corsini, A
abstract

Large-scale slow-moving deep-seated landslides are complex and potentially highly damaging phenomena. The detection of their dynamics in terms of displacement rate distribution is therefore a key point to achieve a better understanding of their behavior and support risk management. Due to their large dimensions, ranging from 1.5 to almost 4 km(2), in situ monitoring is generally integrated using satellite and airborne remote sensing techniques. In the framework of the EFRE-FESR SoLoMon project, three test-sites located in the Autonomous Province of Bolzano (Italy) were selected for testing the possibility of retrieving significant slope displacement data from the analysis of multi-temporal airborne optic and light detection and ranging (LiDAR) surveys with digital image correlation (DIC) algorithms such as normalized cross-correlation (NCC) and phase correlation (PC). The test-sites were selected for a number of reasons: they are relevant in terms of hazard and risk; they are representative of different type of slope movements (earth-slides, deep seated gravitational slope Deformation and rockslides), and different rates of displacement (from few cm/years to some m/years); and they have been mapped and monitored with ground-based systems for many years (DIC results can be validated both qualitatively and quantitatively). Specifically, NCC and PC algorithms were applied to high-resolution (5 to 25 cm/px) airborne optic and LiDAR-derived datasets (such as hillshade and slope maps computed from digital terrain models) acquired during the 2019-2021 period. Qualitative and quantitative validation was performed based on periodic GNSS surveys as well as on manual homologous point tracking. The displacement maps highlight that both DIC algorithms succeed in identifying and quantifying slope movements of multi-pixel magnitude in non-densely vegetated areas, while they struggle to quantify displacement patterns in areas characterized by movements of sub-pixel magnitude, especially if densely vegetated. Nonetheless, in all three landslides, they proved to be able to differentiate stable and active parts at the slope scale, thus representing a useful integration of punctual ground-based monitoring systems.


2022 - Multidisciplinary non-invasive investigations to develop a hydrogeological conceptual model supporting slope kinematics at Fontana Cornia landslide, Northern Apennines, Italy [Articolo su rivista]
Aguzzoli, Alessandro; Arosio, Diego; Mulas, Marco; Ciccarese, Giuseppe; Bayer, Benedikt; Winkler, Gerfried; Ronchetti, Francesco
abstract

A multidisciplinary approach focusing on the integration of diverse and non-invasive investigations is presented to define the hydrogeological conceptual model of the complex Fontana Cornia landslide in the Northern Apennines, Italy. The results of seismic refraction tomography and electrical resistivity tomography investigations indicate that the landslide has a curvilinear sliding surface dividing the shallow calcarenite debris layer from the deeper pelitic bedrock. The surface presents undulations in which water can be stored and supports the application of the fill and spill hypothesis that is seldom used in landslide studies. The joint interpretation of the geophysical outcomes and of the hydrogeological and hydro-chemical analyses of a spring located on the slope allows the definition of the landslide hydrogeological conceptual model. Four specific hydrologic stages with different groundwater flows though the landslide body were identified. The developed hydrogeological model may explain the displacements of the landslide that were detected with In-SAR monitoring. The isotopes analyses, the displacement monitoring, and the hydrogeological measurements confirm that periods with significant precipitations and snowmelt can cause an increase in landslide saturation that in turn triggers larger displacements. Conversely, the landslide slowly moves at a steady rate during periods with limited recharge water.


2021 - Combining spatial modelling and regionalization of rainfall thresholds for debris flows hazard mapping in the Emilia-Romagna Apennines (Italy) [Articolo su rivista]
Ciccarese, G.; Mulas, M.; Corsini, A.
abstract

Landslides hazard assessment requires the combination of spatial and temporal probabilities. In this work, we combine spatial modelling and regionalization of debris rainfall thresholds for assessing both these probabilities and map debris flows initiation hazard over 15 × 103 km2 of the Emilia-Romagna Apennines (Italy). In this area, debris flows are spatially and temporally less frequent than earth slides and earth flows. However, more than a hundred debris flows occurred in October 2014 and September 2015 during two large rainstorms clusters in Parma in Piacenza provinces; some tens of debris flows are reported to have occurred in the past and few others have occurred recently. Since landslides inventory maps used for land use planning only consider some large debris flows accumulation fans, and substantially no information is given on the slopes along which these phenomena might occur, this study aims to fill this gap by creating a hazard map using the evidences collected after the recent abovementioned multi-occurrence events. Different spatial statistical models (Frequency Ratio [FR], Weight of Evidence [WOE] and Logistic Regression [LR]), set up with various combinations of geo-environmental causal factors, have been trained using 60% of debris flow initiation points mapped after the 2014 and 2015 events. The predictive performances of the models have been compared by success rate curves using the remaining 40% of initiation points of the 2014 and 2015 events. The model with the best predictive capability (area under the curve > 0.96) has been further validated using the spatial distribution of other debris flows occurred in the period 1972–2016, and its outputs have been classified into spatial probability classes. Furthermore, the annual exceedance probability of recently published debris flows 3 h cumulated rainfall triggering thresholds has been calculated for in 185 rain gauges and regionalized by spatial interpolation. Finally, spatial and temporal probability maps ranked in a 0–1 range have been combined into a regional debris flows initiation hazard map that, on the basis of the return periods, is associated to different yearly probability values. The resulting hazard map classifies 0.87% of the area as high hazard, 2.83% as medium hazard, 0.5% as low hazard and the remaining 95.81% as null hazard. The spatial distribution of hazardous zones is quantitatively and qualitatively consistent with the spatial distribution of past debris flows. Furthermore, it is coherent with geomorphological common sense and it has proven sufficiently accurate in discriminating as hazardous the debris flows initiation zones of phenomena occurred after it was produced. On such a basis, despite its limitations, we consider the debris flows hazard map produced sufficiently reliable to integrate existing inventory maps in land-use regulation and emergency planning.


2021 - MICROPILES TRIPODS SHIELDS (MTS) AS UNCONVENTIONAL BREAKERS FOR THE CONTROL OF MODERATELY RAPID EARTHFLOWS (SASSI NERI LANDSLIDE, NORTHERN APENNINES) [Articolo su rivista]
Corsini, Alessandro; Giovanna, Baiguera; Francesco, Capuano; Ciccarese, Giuseppe; Diena, Michela; Mulas, Marco; Ronchetti, Francesco; Rossi, Gianluca; Truffelli, Giovanni
abstract

The paper deals with the idea, design and implementation of unconventional one-of-a-kind Micropiles Tripods Shields (MTS) intended to break and decelerate moderately rapid earthflows surges in the track zone of the Sassi Neri landslide (Nure Valley, Northern Apennines, Province of Piacenza, Italy). The MTS are inspired to floating anchors and “chevaux de fries” used in wartime. The basic elements are tripods of 193 mm diameter steel micropiles laid out at triangle, driven into the stable bedrock and emerging some meters aboveground. Each tripod consists of a vertical upslope central pile and two lateral oblique piles, linked by two transversal beams and connection plates aboveground. Multiple tripods are spaced along transversal rows to form Micropiles Tripods Shields (MTS) to advancing earthflows. The design of MTS has been based on field investigations such as boreholes and geophysics, that indicated a limited thickness of landslide deposits in the track zone where MTS have been installed. The forces resulting from active earthflows fronts have been estimated both with geotechnical and hydraulic computations. The analysis of vertical and transversal forces as well as bending moments acting on a single tripod versus the characteristic resistances was carried out using a bi-dimensional scheme with finite-elements software Plaxis, that indicated that the stress levels were compatible with the structural resistance of the tripods. The construction of MTS took place in 2018, involving working site preparation with partial lime-treatment of the surficial layers, underground micropiles drilling and installation, aboveground micropiles welding, tripods completion with connection beams and plates. Some tripods have been instrumented with load cells for monitoring earth pressures against micropiles, electric transducers for groundwater monitoring next to the piles, tiltmeters for tripods rotations and a total station for slope and tripods movements monitoring. Results show that the acceleration of slope movements corresponds to a generalized increase of pore water pressure at all the monitored tripods and to temporary slight tilting of the tripods which has so far being fully recovered when the landside slowed down and pressure decreased. This pioneering application indicates that once the characteristics of the earthflows are carefully considered, the depth to the bedrock in the installation zone is limited, and the logistical conditions in the field during construction are adequate, the MTS can be taken into consideration as a possible unconventional solution to break down and control moderately rapid earthflows.


2020 - Correction to: Sinusoidal wave fit indexing of irreversible displacements for crackmeters monitoring of rockfall areas: test at Pietra di Bismantova (Northern Apennines, Italy) (Landslides, (2020), 17, 1, (231-240), 10.1007/s10346-019-01248-x) [Articolo su rivista]
Mulas, M.; Marnas, M.; Ciccarese, G.; Corsini, A.
abstract

The published version of this article, unfortunately, contained error. The corresponding author found out that in the published version, Figure 1c lacks the level regarding the crack meters position and labeling that was asked to edit during the proofreading.


2020 - Debris flows rainfall thresholds in the Apennines of Emilia-Romagna (Italy) derived by the analysis of recent severe rainstorms events and regional meteorological data [Articolo su rivista]
Ciccarese, G.; Mulas, M.; Alberoni, P. P.; Truffelli, G.; Corsini, A.
abstract

Recent severe rainstorms events in October 2014 and September 2015 triggered more than a hundred debris-flows in the western part of the Apennines of Emilia-Romagna (Italy). In this work, we tested a novel method to define debris flows rainfall thresholds for the 2014 and 2015 rainstorms (which have been used as reference events) and to extend these results across the Apennines of Emilia-Romagna, making use of long-term rainfall data of the regional raingauges network. Results are compared, for validation, to rainfall rates recoded during other past rainstorm-debris flows events (which have been used as validation events). At first, the method involves a spatial discriminant analysis between the spatial distribution of debris flows and the high frequency weather-radar rainfall data for the 2014 and 2015 reference events. The analysis defines rainfall cutoff values over rainfall durations from 30′ to 6 h, related to verification indices in the ROC curves, which are used as debris flows rainfall thresholds. Exceedance ratios are calculated between the computed rainfall thresholds and the rainfall rates at 10 years return periods at corresponding rainfall durations computed for raingauges located in the areas affected by the 2014 and 2015 events. The ratios are then used as multipliers of the rainfall rates at 10 years return periods over rainfall durations from 30′ to 6 h calculated for all other raingauges in the regional study area. To spatialize thresholds calculation to the regional scale, the computed thresholds are interpolated across the Apennines of Emilia-Romagna. The research resulted in the assessment of two-levels debris flows rainfall thresholds curves which seem to be adequate to discriminate rainfall rates recorded during past debris flows events used for validation. Discussion evidences advantages and limits of our approach, compares results to existing debris flows thresholds and highlights their possible use in a multi-stage warning procedure at regional scale.


2020 - Displacements of an Active Moderately Rapid Landslide—A Dataset Retrieved by Continuous GNSS Arrays [Articolo su rivista]
Mulas, Marco; Ciccarese, Giuseppe; Truffelli, Giovanni; Corsini, Alessandro
abstract


2020 - Integration of Digital Image Correlation of Sentinel-2 Data and Continuous GNSS for Long-Term Slope Movements Monitoring in Moderately Rapid Landslides [Articolo su rivista]
Mulas, Marco; Ciccarese, Giuseppe; Truffelli, Giovanni; Corsini, Alessandro
abstract


2020 - Sinusoidal wave fit indexing of irreversible displacements for crackmeters monitoring of rockfall areas: test at Pietra di Bismantova (Northern Apennines, Italy) [Articolo su rivista]
Mulas, M.; Marnas, M.; Ciccarese, G.; Corsini, A.
abstract

Temperature changes affect crackmeters monitoring on a daily and a seasonal basis. This is due to rock mass thermal dilatancy and to instrumental matters. The consequent widening closing cycles can mask small irreversible displacements that might be precursors of rock failures. Recently, Weber et al. (Cryosphere 11:567–583, 2017) have proposed a linear fit method between temperature and fracture opening in order to compute the irreversibility index as a metrics to rank irreversible displacements. However, such an approach requires temperature sensors coupled to crackmeters. In order to overcome these limits, we propose an alternative method for deriving a normalised Z-score irreversibility index. It is based on sinusoidal wave fit of cracks opening time series only; thus, it does not require temperature monitoring. The methodology has been tested using data recorded by a wireless sensor network installed at La Pietra di Bismantova rock slab composed of 14 crackmeters and thermometers monitoring potentially unstable rock masses. A comparison of results obtained using the method of Weber et al. (Cryosphere 11:567–583, 2017) and the sinusoidal approach shows that the latter is much less sensitive to the duration of the moving window used to derive the irreversibility index, making it a much more flexible tool for indexing irreversible displacements over short time periods. Moreover, as rapid high–magnitude temperature changes can also be the causal factor of irreversible displacements, their statistical relation with peaks of the Z-score irreversibility index has been investigated. Results have shown that, depending on which crack is examined, correlations between irreversibility peaks and antecedent extreme temperature variations are more or less relevant. In conclusion, we believe that the Z-score sinusoidal wave fit irreversibility index (ZSFI) can represent a useful metrics for indexing irreversible displacements in unstable blocks using crackmeters’ datasets affected by temperature cycles at the daily and seasonal scale. [Figure not available: see fulltext.].


2018 - Deformation responses of slow moving landslides to seasonal rainfall in the Northern Apennines, measured by InSAR [Articolo su rivista]
Bayer, Benedikt; Simoni, Alessandro; Mulas, Marco; Corsini, Alessandro; Schmidt, David
abstract

Slow moving landslides are widespread geomorphological features in the Northern Apennines of Italy where they represent one of the main landscape forming processes. The lithology of the Northern Apennines fold and thrust belt is characterized by alternations of sandstone, siltstone and clayshales, also known as flysch, and clay shales with a chaotic block in matrix fabric, which are often interpreted as tectonic or sedimentary mélanges. While flysch rocks with a high pelitic fraction host earthslides that occasionally evolve into flow like movements, earthflows are the dominant landslide type in chaotic clay shales. In the present work, we document the kinematic response to rainfall of landslides in these different lithologies using radar interferometry. The study area includes three river catchments in the Northern Apennines. Here, the Mediterranean climate is characterized by two wet seasons during autumn and spring respectively, separated by dry summers and winters with moderate precipitation. We use SAR imagery from the X-band satellite COSMO SkyMed and from the C-band satellite Sentinel 1 to retrieve spatial displacement measurements between 2009 and 2016 for 25 landslides in our area of interest. We also document detailed temporal and spatial deformation signals for eight representative landslides, although the InSAR derived deformation signal is only well constrained by our dataset during the years 2013 and 2015. In spring 2013, long enduring rainfalls struck the study area and numerous landslide reactivations were documented by the regional authorities. During 2013, we measured higher displacement rates on the landslides in pelitic flysch formations compared to the earthflows in the clay shales. Slower mean velocities were measured on most landslides during 2015. We analyse the temporal deformation signal of our eight representative landslides and compare the temporal response to precipitation. We show that earthslides in pelitic flysch formations accelerate faster than earthflows in chaotic clay shales and reach higher velocities, while the kinematic behaviour of the earthflows can be described as rather steady with only minor accelerations. Although we have no detailed pore pressure measurements for the period of interest, the observed behaviour can be explained in our view by the morphological and hydrological characteristics of the different landslide types. On the one hand landslide material and bedrock in the pelitic flysch rocks are more resistant, which is why slope angles are higher in this lithology. On the other hand, landslides in the pelitic flysch formations have often deeper slip surfaces and landslide material is more permeable. This is why long persistent rainfall is necessary to saturate the landslide material and induce pore pressures that are high enough to trigger displacement.


2018 - Slope dynamics and streambed uplift during the Pergalla landslide reactivation in March 2016 and discussion of concurrent causes (Northern Apennines, Italy) [Articolo su rivista]
Mulas, Marco; Ciccarese, Giuseppe; Ronchetti, Francesco; Truffelli, Giovanni; Corsini, Alessandro
abstract

On March 28, 2016, the toe zone of the apparently dormant Pergalla earthslide-earthflow (Northern Apennines, Italy) had a paroxysmal reactivation. In the course of 2 days, displacements up to almost 8 m severely damaged several houses and roads. At the bottom of the slope, the emersion of rotational sliding surfaces determined the uplift of almost 3 m of the Nure river streambed that was consequently partially dammed. The paper describes the landslide event on the basis of field surveys and analysis of post-event aerial photos, as well as data from geophysical surveys and pre- to post-failure displacement monitoring. It also discusses the possible concurrent causes of the event, including antecedent rainfall, the migration of active streambed channels of Nure river toward the landslide toe in the previous year, and the existence of long-term pre-failure slow movements. It is concluded that these factors, together with the presence of sliding surfaces extending beneath the valley floor, should be primarily considered if a preventive assessment of river damming potential due to streambed uplift should be made for other similar landslides in the Apennines.


2017 - Development of multi-purposes procedures and service tools for GNSS data processing finalized to monitor a deep-seated earthslide in the Dolomites (Italy) [Abstract in Atti di Convegno]
Crespi, Mattia; Fratarcangeli, Francesca; Mazzoni, Augusto; Nascetti, Andrea; Monsorno, Roberto; Schloegel, Romy; Corsini, Alessandro; Mulas, Marco; Mair, Volkmar
abstract

The Corvara landslide is an active, large-scale, deep-seated and slow moving earthslide of about 30 Mm3 located in the Dolomites (Italy). It is frequently damaging a national road and, occasionally, isolated buildings and recre- ational ski facilities. In this work we present the analysis performed on data acquired thank to the installation of 3 DualFrequency GPS in permanent acquisition installed in the accumulation, track and source zone of the active portion of the landslide. In particular two years (2014 and 2015) of data were processed with several approaches and goals: daily time series were produced through Precise Point Positioning and Differential Positioning using both scientific packages and automatic on line tool based on open source libraries, specifically developed in order to provide a prototypal service. The achievable results based on single frequency (L1) data processing were also investigated in order to pave the way to the deployment of lowcost GPS receiver for this kind of application. Moreover, daily and sub-daily phenomena were analyzed. Different strategies were investigated in order to de- scribe the kinematics on the basis of 0.2 Hz data collected by the 3 permanent receivers. For particular events also the variometric approach, through the recent advances of VADASE, was applied, to detect significant movements. Finally, tropospheric parameters were estimated over the whole period in order to give a contribution to the SAR interferometry techniques. Also for this specific purpose and application, the possibilities of single frequency use were assessed.


2017 - Landslide Zoning Using the Principal Component Analysis on Monitoring Data: The Sauna Earth Slide—Earth Flow (Parma, Italy) [Relazione in Atti di Convegno]
Mulas, Marco; Bonacini, Francesco; Petitta, Marcello; Ronchetti, Francesco; Truffelli, Giovanni; Diena, Michela; Corsini, Alessandro
abstract

In this contribute, we present the morphodynamic zoning of the Sauna complex earth slide—earth flow (Corniglio municipality, Northern Apennines) obtained by integrating results of field surveys and of Principal Component Analysis (PCA) of continuous displacement monitoring data. Since January 2014, the area is surveyed by an Automated Total Station (ATS) monitoring 30 prisms with duty cycles of 2 h. An evacuation plan has been adopted by the local authorities, which is based on pre-defined movement thresholds. However, during more than 2 years of monitoring, the results have evidenced that in different zones of the slope, differentiate displacement rates and timings of response to precipitations take place. Therefore, in order to fine tune evacuation plans, movement thresholds should be more appropriately tailored on the basis of morphodynamic zones rather than being left spatially generic. The final result is a morphodynamic zonation of the slope that represents a useful document to identify areas in which differentiated movement thresholds can be assessed for alert and alarm.


2017 - Multi-Temporal X-Band Radar Interferometry Using Corner Reflectors: Application and Validation at the Corvara Landslide (Dolomites, Italy) [Articolo su rivista]
Schlögel, Romy; Thiebes, Benni; Mulas, Marco; Cuozzo, Giovanni; Notarnicola, Claudia; Schneiderbauer, Stefan; Crespi, Mattia; Mazzoni, Augusto; Mair, Volkmar; Corsini, Alessandro
abstract

From the wide range of methods available to landslide researchers and practitioners for monitoring ground displacements, remote sensing techniques have increased in popularity. Radar interferometry methods with their ability to record movements in the order of millimeters have been more frequently applied in recent years. Multi-temporal interferometry can assist in monitoring landslides on the regional and slope scale and thereby assist in assessing related hazards and risks. Our study focuses on the Corvara landslides in the Italian Alps, a complex earthflow with spatially varying displacement patterns. We used radar imagery provided by the COSMO-SkyMed constellation and carried out a validation of the derived time-series data with differential GPS data. Movement rates were assessed using the Permanent Scatterers based Multi-Temporal Interferometry applied to 16 artificial Corner Reflectors installed on the source, track and accumulation zones of the landslide. The overall movement trends were well covered by Permanent Scatterers based Multi-Temporal Interferometry, however, fast acceleration phases and movements along the satellite track could not be assessed with adequate accuracy due to intrinsic limitations of the technique. Overall, despite the intrinsic limitations, Multi-Temporal Interferometry proved to be a promising method to monitor landslides characterized by a linear and relatively slow movement rates.


2017 - Use of ROC curves for early warning of landslide displacement rates in response to precipitation (Piagneto landslide, Northern Apennines, Italy) [Articolo su rivista]
Corsini, Alessandro; Mulas, Marco
abstract

Active landslides are generally characterized by variations in displacement rate in response to cumulated precipitation. Velocities that are only exceeded in a limited number of days during the year might be considered as critical events, since they might determine, or prelude to, a significant evolution of the landslide. The purpose of this paper is to present a novel approach based on the use of receiver operating characteristic (ROC) curves for assessing cumulated precipitation thresholds that can provide early warning for the occurrence of critical events such as the exceedance of rare displacement rates. The approach has been developed and tested in the Piagneto landslide, an active complex rock slide—debris slide in the Northern Apennines of Italy, for which a 5-year continuous surveying monitoring dataset is available. On the basis of the first 4 years of monitoring data (training dataset), threshold curves relating cumulative precipitation (mm) to precipitation moving windows (days) have been generated by using different benchmarks that, in literature, are used to estimate the maximum predictive performance of ROC curves. These threshold curves have been successfully validated using the last 1 year of monitoring data (validation dataset). They have then been used to simulate how they might help defining different early warning levels in due advance. The proposed methodology can be replicated in any landslide for which a monitoring dataset that includes recurrent acceleration events in response to precipitation is available.


2016 - Assessment of the 2006 to 2015 Corvara landslide evolution using a UAV-derived DSM and orthophoto [Relazione in Atti di Convegno]
Thiebes, B; Tomelleri, E; Mejia Aguilar, A; Rabanser, M; Schlögel, R; Mulas, Marco; Corsini, Alessandro
abstract

We present a UAV-based photogrammetry study on Corvara landslide, a large and active earthflow in the Italian Dolomites. During a one-day field survey, an area of approximately 13 ha was cov- ered and a very high resolution orthophoto and a point cloud consisting of more than 200 million points were created. From this data, a Digital Surface Model (DSM) with a pixel size of 1.5 cm was prepared. The comparison to the existing 2006 LiDAR DSM highlights landslide enlargements, displacement rates and material depletion and accumulation exceeding 11 m. Although some uncertainties regarding the exact magnitude of topographical changes remain, the methodology has been evaluated as a useful addi- tion to the ongoing monitoring activities on the Corvara landslide by GPS and DInSAR due to the unprecedented level of detail.


2016 - Impulsive ground movements in the mud volcanoes area of "le Sarse" di Puianello (Northern Apennines, Modena, Italy): Field evidence and multi-approach monitoring [Articolo su rivista]
Mulas, Marco; Bayer, Benedikt; Bertolini, Giovanni; Bonacini, Francesco; Leuratti, Enrico; Pizziolo, Marco; Simoni, Alessandro; Corsini, Alessandro
abstract

In this contribution we present the work carried out to determine the nature of the impulsive vertical ground movements occurred in February 2015 in the mud-volcanoes area "Le Sarse" (Northern Apennines, Modena province, Italy). A multi-technique based work has been started including field surveys, SAR Multi-Interferometric processing and high-precision periodical D-GPS monitoring. Field evidence indicates that movements occurred in February 2015, in the order of 25 cm in few minutes, can be ascribed to a vertical collapse of part of the caldera area rather than to a landslide activity. The affected area is bordered by concentric normal faults that were originated during February 2015. According to SAR interferometry, the collapsed area was already undergoing movements in the order of 2 cm/year at least from 2012. The D-GPS monitoring indicates that movement rates have nowadays still taking place at rates higher than those of the pre-event. In conclusion, it can be assumed that movements in the area are most likely related to the mechanisms controlling the activity and evolution of the mud volcano itself. However, the reconstruction of the structural characteristics of this caldera system and the identification of the specific causes for the February 2015 event still need to be further investigated.


2016 - Monitoring landslide kinematics by multi-temporal radar interferometry - the Corvara landslide case study [Abstract in Atti di Convegno]
Thiebes, Benni; Cuozzo, Giovanni; Callegari, Mattia; Schlögel, Romy; Mulas, Marco; Corsini, Alessandro; Mair, Volkmar
abstract


2016 - Quantitative monitoring of surface movements on active landslides by multi-temporal, high-resolution X-Band SAR amplitude information: Preliminary results [Relazione in Atti di Convegno]
Mulas, Marco; Corsini, Alessandro; Cuozzo, G; Callegari, Mattia; Thiebes, Benjamin; Mair, V.
abstract

Multi-temporal image cross-correlation is a method for tracking moving features and can there-fore be used for quantitative assessments of surface displacements. Accuracies of up to 1/8th of the original image geometric resolution can be achieved. We present the results of an analysis car- ried out on Corvara landslide located in the Italian Dolomites. Image offset-tracking was applied to CosmoSky-Med amplitude images acquired between October 2013 and August 2015. The presence of a validation dataset consisting of periodical GPS surveys carried out on 16 benchmarks represents an ideal opportunity to test the applicability of SAR-based image cross-correlation for landslide moni- toring. Despite the relative low accuracy of the results amplitude-based offset-tracking proved to be beneficial due to the ability of this method to capture large displacements. In particular the results evidence its complementarity with respect to multi-temporal interferometry that is confined to slow displacements along E-W directions.


2016 - Toward a centralized data management center for integrated landslide monitoring in Emilia Romagna Region (Italy) [Relazione in Atti di Convegno]
Corsini, Alessandro; Bonacini, Francesco; Ciccarese, Giuseppe; Mulas, Marco; Ronchetti, Francesco; Nanni, Stefania; Truffelli, Giovani; Caputo, Giuseppe; Pizziolo, Marco; Primerano, Sabrina; Monni, Antonio
abstract

In Emilia Romagna Region, slope monitoring systems have become more widely used for hazard and risk management. However, they are generally non-interoperable. Moreover dispersion of monitoring data in several local databases have made data sharing among the involved institutional actors quite laborious and often untimely. A centralized database and a web-based portal that integrate infor- mation derived by different types of slope monitoring systems has been developed. The paper illustrates the specific features of the developed “SensorNet” and provides examples of its use for visualizing and analyzing in an integrated manner data from different monitoring systems. In perspective it could serve as an every-day operational tool for a timely reporting of landslide monitoring data for surveillance and warning purposes.


2015 - A portable continuous GPS array used as rapid deployment monitoring system during landslide emergencies in Emilia Romagna [Articolo su rivista]
Corsini, A.; Bonacini, F.; Mulas, M.; Ronchetti, F.; Monni, A.; Pignone, S.; Primerano, S.; Bertolini, G.; Caputo, G.; Truffelli, G.; Benini, A.; Berti, M.
abstract

The possibility to rapidly deploy a continuous monitoring system in and around an active landslide during an emergency is crucial in order to gather information for hazard and risk scenarios updates. This paper deals with the use of an optimized portable and self-powered array of continuous GPS receivers that has been used for rapid deployment in several landslides during 2013 and 2014 emergency events in Emilia Romagna. In order to optimize the array of GPS receivers, so to make it a sort of plug-and-play system that can be operative in a few hours only and provide data in near-real time,, several technical and logistic issues had to be pre-evaluated and solved in the configuration of the system. These issues are illustrated in the short note together with some of the results obtained in the monitored sites.


2015 - Acceleration of large active earthflows triggered by massive snow accumulation events : evidences from monitoring the Corvara landslide in early 2014 ( Dolomites , Italy ) [Abstract in Atti di Convegno]
Corsini, Alessandro; Mulas, Marco; Marcato, Gianluca; Chinellato, Giulia; Mair, Volkmar
abstract

In the Dolomites of Italy, snowfall during winter 2013/2014 was exceptionally abundant. Major snowfall events occurred from late December 2013 to mid-March 2014. Snow accumulation in Badia Valley peaked in early February: from 2 to 4 meters with a positive gradient respect to altimetry and accordingly to wind accumulation zones. Below 2000 m asl, due to the mild temperatures recorded before the onset of snowfall, the relatively dry snow cover was mostly deposited on top of unfrozen soils. The Corvara landslide is a large active earthflow located close to Corvara in Badia, at an elevation from 2000 to 1600 m. It’s displacement rate before, during and after the exceptional snowfall period was monitored at high temporal frequency. Surface displacement was measured bi-weekly by differential GPS in several benchmarks in the source, track and accumulation zone. Deep displacement was monitored semi-continuously by two in-place inclinometers at 48 m depth in the accumulation zone, across the main deep-seated sliding surface. Results show an acceleration of movements, both at surface and at depth, soon after the massive snow accumulation event of 31st January to 2nd February 2014, which suddenly increased snow thickness from 1 to more than 2 metres. Short time lags between the onset of the acceleration of movements in the source, the track and the accumulation zones were also recorded. The landslide then maintained a relatively constant velocity during the high snow cover period extended to earlyApril and underwent a progressive deceleration during the snowmelt period that lasted until mid-June. The fact that the acceleration of the Corvara earthflow was triggered by a massive and rapid snow accumulation event, provides a quite different perspective from the generally adopted one that considers the destabilizing effect of snow only in relation to the increase of groundwater level during rapid snowmelt. A full explanation of the processes associated to the dynamics observed in Corvara is undoubtedly still an open issue. However, it can be tentatively speculated that in the some sectors of the source and track zone, where sliding surfaces are relatively shallow -around 15 m deep -, the weight of the copiously fallen snow induced a distributed undrained loading in the already fully saturated and confined landslide mass. Or, alternatively, that snow accumulation over the unfrozen soil induced groundwater levels above the ground. To explain how acceleration of movements occurred as deep as 48 m in the accumulation zone, it might be argued that the mass and/or the pore pressure transfer from the track to the accumulation zone - evidenced by the time lag of velocity peaks- can have played a role in indirectly transferring to the accumulation zone the acceleration induced by massive snowfall in the track zone. To provide more robust answers, further monitoring data collection and analysis is needed. Thus, while waiting for other massive snowfall events, three continuous GPS receivers and a water pressure transducer in the soil havebeen added to the monitoring network during 2014.


2015 - Cross-correlation and time-lag analysis of high frequency monitoring data of the Vallcebre landslide (Eastern Pyrenees, Spain) to reveal cause-effect relationships between variables governing slope instability [Abstract in Atti di Convegno]
Mulas, Marco; Moya, Jose; Corsini, Alessandro; Corominas, Jordi
abstract

The Vallcebre landslide is a slow moving large landslide located 140 km north of Barcelona in the Eastern Pyrenees. Monitoring data of the Vallcebre landslide represent a singular case of multi parameter high-frequency monitoring system set up in 1996 and still ongoing. Data of movements and groundwater levels are measured and recorded with a frequency of 20 minutes in 6 boreholes distributed in the landslide, each one equipped with a wire extensometer and a piezometer, while rainfall is recorded by a specific gauge at the site. Data from 3 boreholes recorded during three full years of measurements (from 1999 to 2001) have been analyzed by means of a cross-correlation function in order to determine the reciprocal interdependency and the relative time lag between rainfall, groundwater and movement rate maxima and, ultimately, to evidence cause-effect processes occurring along the slope. It should be pinpointed that, in this specific case, rainfall is also a proxy for the discharge level of the stream eroding the toe of the landslide, that is believed to be one of the main instability factors. The cross-correlation function is a quite simple signal processing tool for measuring similarities of waveforms as function of an applied time-lag. Specifically, it was applied to study: i) the relations between rainfall and movement rate, so to highlight the relative time lag for rainfall to produce an effect in different points of the landslide; ii) the inter-dependencies between different movement rates in the three boreholes in order to determine the pattern of mobilization of the landslide (from up to down slope and vice-versa); iii) the response of groundwater with respect to rainfall, which reflects the local permeability; iv) the evolution of groundwater levels in the three monitoring points. Altogether, results confirm and constrain in time the retrogressive trend of movements in the landslide (in agreement with a 2D numerical model previously developed by Ferrari et. al. 2011) and the driving role of stream undercutting the toe of the landslide, as the acceleration of movements at the lower borehole has the shortest time lag with respect to rainfall, disregard the fact that groundwater level raise earlier in the upper piezometers. Finally, the in-depth analysis of time-lags between movement rates along the slope, allowed highlighting compression and tensile phases in different zones along the longitudinal cross section of the landslide.


2015 - Integration of X-band SAR interferometry , continuous and periodic D-GPS and in-place inclinometers to characterize and monitor a deep-seated earthslide in the Dolomites ( Italy ) [Abstract in Atti di Convegno]
Mulas, Marco; Corsini, Alessandro; Soldati, Mauro; Marcato, Gianluca; Pasuto, Alessandro; Crespi, Mattia; Mazzoni, Augusto; Benedetti, Elisa; Branzanti, Mara; Manunta, Michele; Ojha, Chandrakanta; Chinellato, Giulia; Cuozzo, Giovanni; Costa, Armin; Monsorno, Roberto; Thiebes, Benni; Piantelli, Elena; Magnani, Massimo; Meroni, Marco; Mair, Volkmar
abstract

The Corvara landslide is an active, large-scale, deep-seated and slow moving earthslide of about 30 Mm3 located in the Dolomites (Italy). It is frequently damaging a national road and, occasionally, isolated buildings and recreational ski facilities. Since the mid ‘90s it has been mapped, dated and monitored thanks to field surveys, boreholes, radiocarbon dating, inclinometers, piezometers and periodic D-GPS measurements, carried out by the Geology and the Forestry Planning offices of the Autonomous Province of Bolzano, the Municipality of Corvara in Badia, the University of Modena and Reggio Emilia, the IRPI-CNR of Padua. In 2013, a new phase of characterization and monitoring has started which also involves the EURAC’s Institute for Applied Remote Sensing, the geodesy group of University La Sapienza, the CNR-IREA of Naples and the Leica Geosystems office in Italy. This new phase of characterization and monitoring is meant to investigate the opportunities of innovative SAR interferometry, D-GPS and in-place inclinometers techniques to provide for a high frequency monitoring of the study site in support to the analysis of the investigation of forcing factors leading unsteady, nonuniform landslide motion through different seasons of the year. Monitoring results are also expected to provide a validation of innovative interferometric techniques so to fully evaluate their conformity to be used as a long-term monitoring system in land-use planning and risk management procedures. The monitoring infrastructure now integrates: 16 Corner Reflector for satellite X-Band SAR interferometric products, 13 benchmarks for D-GPS periodic surveys, three on-site GPS receivers for continuous positioning and remote ftp data pushing, two in-place inclinometers and a pressure transducer to record pore-pressure variations. The coupling of SAR-based products with GPS records is achieved using especially designed Corner Reflectors having an appendix dedicated to hold Dual-Frequency GPS antennas. COSMO-SkyMed X-Band SAR acquisitions started on October 2013 and are ongoing with a temporal resolution of 16 days using STRIPMAP (HIMAGE) measuring mode. Discontinuous D-GPS Fast-Static surveys are scheduled with a triple frequency: annual for 24 points outside recent activation areas, monthly for 13 points in the active zone and a bi-weekly for 6 points located in the most active zone. Displacement high-frequency data are acquired thank to the installation of 3 Dual-Frequency GPS in permanent acquisition that have been located in the accumulation, track and source zone of the active portion of the landslide. High frequency data are also obtained by the two inclinometers operating in continuous acquisition located across the main slide surface at 48 m depth into a 90 m borehole drilled in the accumulation zone. A piezometer installed in the source zone and the meteorological station of Piz La Ila (3 km far away) of the Autonomous Province of Bolzano complete the system.


2015 - Long-Term Continuous Monitoring of a Deep-Seated Compound Rock Slide in the Northern Apennines (Italy) [Relazione in Atti di Convegno]
Corsini, Alessandro; Bonacini, F.; Mulas, Marco; Petitta, M.; Ronchetti, Francesco; Truffelli, G.
abstract

An automated total station monitored a compound rock slide near the Cerreto Pass (northern Apennines, Italy) for more than three and a half years. The rock slide, which threatens national road SS63, has an estimated volume of more than 3 million m3 and is composed by the overlap of highly fractured limestone on an impermeable and weak clay shale layer. Specifically, a network of more than 30 prisms has been measured every 2 h from October 2009 to May 2013. This dataset provides substantial evidence of displacement rates up to 15 cm/year and gives information about the control of rainfall on slope movements. On the yearly scale the seasonal variation of rainfall regime determines the baseline displacement rate of the rockslide while moving to shorter time spans has been possible to individuate effects of rain episodes calculated on daily and weekly sampling. Results highlight the added value of continuous monitoring for assessing rock slide dynamics and improving hazard assessment.


2015 - Long-term monitoring of a deep-seated, slow-moving landslide by mean of C-band and X-band advanced interferometric products: the Corvara in Badia case study (Dolomites, Italy) [Articolo su rivista]
Mulas, Marco; Petitta, M.; Corsini, Alessandro; Schneiderbauer, S.; Mair, F. V.; Iasio, C.
abstract

The availability of data from various Synthetic Aperture Radar (SAR) operating in X-Band and C-Band acquired in the last decades enables to monitor slopes affected by landslides. The ASI-founded project ‘LAWINA’ (2010 – 2012) aimed at the improvement of SAR – based monitoring techniques as well as at the integration of SAR data with data stemming from other sensors. Test case area of LAWINA has been a slow-moving landslide located up-stream of Corvara in Badia village in the Dolomites, Italy. Within the scope of the project different time-series obtained through 35 Envisat2, 40 Radarsat-1 and 46 Cosmo-SkyMed covering this test area have been processed in order to explore the potentials to analyse historical and near real time landslide dynamics. The SAR data are characterized by various geometric and temporal resolutions having been acquired by 3 sensors operating at different bands in different periods between 2003 and 2011. TeleRilevamento Europa (TRE) exploited these data in order to retrive displacement time- series applying its proprietary SqueeSAR algorithm. After re-projecting Envisat-2 and Radarsat datasets according to the CSK Line Of Sight a comparison of displacements recorded by each sensor has been possible. For this purpose, we have selected areas characterized by the presence of Persistent Scatterers or Diffused Scatterers from at least two datasets. This multi-sensor approach allowed determining the slope displacement tracking during 8 years. Even though the different time series are not formally integrated each other, the result is accurate enough to allow the evaluation of the landslide’s behaviour and trend over several years


2015 - Prediction of landslide velocity at given cumulated rainfall values based on analysis of continuous monitoring data using ROC curves : application to the Piagneto landslide ( Northern Apennine , Italy ) [Abstract in Atti di Convegno]
Corsini, Alessandro; Mulas, Marco; Petitta, Marcello; Bonacini, Francesco; Ronchetti, Francesco
abstract

A novel approach to predict landslide velocity at given cumulated rainfall values based on the analysis of continuous displacement and rainfall monitoring data by using ROC curves has been developed and tested in the Piagneto landslide (northern Apennines, Italy). It is an active rock slide for which a velocity dataset covering the period October 2009 to December 2014 is available thanks to a total station that has been monitoring tens of prisms at duty cycles of 2 hours. Over the same time frame, an hourly rainfall dataset is available from rain gauges located just a few km away from the landslide. The ROC curve (Receiver Operating Characteristic) is a well-known and widely used method to assess the efficiency of a binary classifier. In this case, it is used to assess the efficiency of different values of cumulated rainfall to determine a given value of velocity in the landslide. Operatively, the daily velocity distributions of selected monitoring prisms is plotted in order to assess upper values at given levels of occurrence probability, i.e. velocity values at the upper 1st,2nd, 3rd quartile and 2 sigma. These velocity values are then classified with respect to daily rainfall cumulated over different time windows (from 1 to 120 days), that are considered singularly or in combination one another. The area under the ROC curves, as well as the max distance from the random line, is used as indicator of performance in order to assess the cumulated rainfall (in terms of amount and duration) showing the higher performance in predicting a defined landslide velocity level. The values obtained with the retrospective analysis of monitoring data, can then be used for prediction of expected velocity levels. This has been verified by using the conventional approach of dividing the dataset in a training and a validation subsets. Results underline the added value of the analysis of long time-series of continuous landslide monitoring data by mean of operational research tools, such as in this case the ROC curves, for extracting information useful for improving the comprehension and the prediction of slope dynamics that, in specific cases, can be of great support to risk management.


2014 - Remote and terrestrial ground monitoring techniques integration for hazard assessment in mountain areas [Abstract in Atti di Convegno]
Chinellato, G; Kenner, R; Iasio, Christian; Mair, V; Mosna, D; Mulas, Marco; Phillips, M; Strada, C; Zischg, A.
abstract

In high mountain regions the choice of appropriate sites for infrastructure such as roads, railways, cable cars or hydropower dams is often very limited. In parallel, the increasing demand for supply infrastructure in the Alps induces a continuous transformation of the territory. The new role played by the precautionary monitoring in the risk governance becomes fundamental and may overcome the modeling of future events, which represented so far the predominant approach to these sort of issues. Furthermore the consequence of considering methodologies alternative to those more exclusive allow to reduce costs and increasing the frequency of measurements, updating continuously the cognitive framework of existing hazard condition in most susceptible territories. The scale factor of the observed area and the multiple purpose of such regional ordinary surveys make it convenient to adopt Radar Satellite-based systems, but they need to be integrated with terrestrial systems for validation and eventual early warning purposes. Significant progress over the past decade in Remote Sensing (RS), Proximal Sensing and integration-based sensor networks systems now provide technologies, that allow to implement monitoring systems for ordinary surveys of extensive areas or regions, which are affected by active natural processes and slope instability. The Interreg project SloMove aims to provide solutions for such challenges and focuses on using remote sensing monitoring techniques for the monitoring of mass movements in two test sites, in South Tyrol (Italy) and in Grisons Canton (Switzerland). The topics faced in this project concern mass movements and slope deformation monitoring techniques, focusing mainly on the integration of multi-temporal interferometry, new generation of terrestrial technologies for differ- ential digital terrain model elaboration provided by laser scanner (TLS), and GNSS-based topographic surveys, which are used not only for validation purpose, but also for adding value and information to the whole monitoring survey. The test sites are currently observed by an original integrated methodology specifically developed within the aim of the project. The integrated monitoring design includes reference targets for the different monitoring systems placed together on the same point or rigid foundation, to facilitate the comparison of the data and, in the operational use, to be able to switch consistently from one to the other system. The principal goal of the project is to define a shared procedure to select scalable technologies, best practices and institutional action plans more adequate to deal with different sort of hazard related to ground displacement, in densely populated mountain areas containing recreational and critical infrastructures.


2013 - Retrieving high resolution deformation patterns of slow moving landslides by COSMO-SkyMed SAR data: a sustainable long term monitoring system using artificial reflectors [Abstract in Atti di Convegno]
Iasio, Christian; Mulas, Marco; Corsini, Alessandro
abstract

Retrieving high resolution deformation patterns of slow moving landslides by COSMO-SkyMed SAR data: a sustainable long term monitoring system using artificial reflectors


2012 - A new approach for slope instability characterization: spatio-temporal analysis of SAR based time series applied to the corvara in Badia landslide test-case (Dolomites, Italy) [Relazione in Atti di Convegno]
Mulas, Marco; Petitta, Marcello; Branzanti, Mara; Benedetti, Elisa; Corsini, Alessandro; Iasio, Christian
abstract

The aim of this study is to discern and estimate the influence of different forcing factors acting on instability phases of a slow alpine earthslide-earthflow. To reach this scope, the deformation signals of displacement rates measured by Persistent Scatterers Interferometry (PSI) have been decomposed and analyzed taking in mind the dynamics of the different sectors included in the mass movement already known by previous studies.


2012 - Cosmo Skymed High Frequency - High Resolution Monitoring Of An Alpine Slow Landslide, Corvara In Badia, Northern Italy [Relazione in Atti di Convegno]
Iasio, C.; Novali, F.; Corsini, Alessandro; Mulas, Marco; Branzanti, M.; Benedetti, E.; Giannico, C.; Tamburini, A.; Mair, V.
abstract

Located in the Alta Badia Valley, a famous tourist area in the Dolomites of northern Italy, the active Corvara earthslideearthflow causes damages to critical road infrastructures, as well as ski and other recreational facilities and power lines. The high spatial resolution and the short frequency of revisit time of COSMO-SkyMed system (CSK®), open new opportunities for SAR-based monitoring systems dedicated to natural risks management. The ASI AO funded project “LAWINA” takes advantage from these distinctive features together with non-conventional reflectors, in order to monitor and assess the hazard of such a phenomenon by means of PSI techniques. The particular working context and the complete processing workflow for this specific application, offer opportunity to highlight strengths and weak points of classical approach to PSI and to provides suggestions for an effective use of experimented corners.


2012 - Spatio-temporal analysis of SAR based time series for slope instability characterization : the Corvara in Badia landslide ( Dolomites , Italy ) [Abstract in Atti di Convegno]
Mulas, Marco; Petitta, Marcello; Branzanti, Mara; Benedetti, Elisa; Corsini, Alessandro; Iasio, Christian
abstract

The aim of this study is to estimate the influence of different forcing factors acting on instability phases of a slow alpine earthslide-earthflow, by means of the characteristics of decomposed deformations signals derived by displacement rates measured in its different sectors. In this work we analyze a slow landslide located ESE from Corvara in Badia, a famous tourist area in the Dolomites (NE Italy). Road, infrastructure, ski and other recreational facilities, isolated buildings close to the town of Corvara and finally an artificial reservoir for snow production are threatened and occasionally damaged by this mass movement. It flows from 2000m s.l. to 1500m s.l. where a paleo-landslide deposit is partially covered and re-activated. In the last 10 years the Province of Bolzano carried out discontinuous GPS surveys between 5 and 1 times per year to define the landslide’s level of hazard. The landslide volume is resulted to be 30Mm3, xtending downslope for approx. 3km, with displacement rates between few centimeters and slightly less than 10m per year. To analyze this area we used data from active radar sensors (SAR – Synthetic perture Radar). The SAR-based dataset consists in high resolution X-band SAR data from the Cosmo SkyMed (CSK) mission acquired every 8 days from August 2010 to September 2011. Part of the 38 CSK scenes contain the back-scattering signal from 17 artificial reflectors (AR) installed along the AOI and partially on existing GPS benchmarks for data validation and integration. The ARs back scattering signal has been elaborated in order to track their displacement from August 2010 to September 2011, in the lower zone of the landslide, as well as from March 2011 to September 2011 in the higher part, excluding the period when the snow was covering the surface. The signals have been analyzed with Fourier and wavelet methods to identify the different frequencies and nature of the components. T and Mann-Kendall tests have been used to assess the presence of trends. Fits with exponential functions of the de-trended and de-seasonalized signal have been performed to identify the presence of dissipating deformations. We observed that the signal of velocity and acceleration is characterized by the coexistence of different factors: first, periodic signals associated to seasonal and gravitational kinematic behavior; second, decay effects due to instability events. Moreover, using different points is possible to observe the signal propagation both in time and space. This analysis allow us to determine the spatio-temporal scale of different forcing events and their effect on the total landslide area. Finally, this study represent a new approach for identify the spatio-temporal nature of different factors in the evolution of the landslide for setting-up a system of conscious prediction of aintenance tasks of he exposed structures. The use of the SAR data demonstrated to be an innovative tool for high temporal resolution surveys with a big amount of points that in comparison with GPS surveys results to be conomically convenient in wide AOI.


2011 - Morphodinamic mapping of landslide affected slopes: the case of the Groapa Vantului (Romania) [Abstract in Atti di Convegno]
Mulas, Marco; Fubelli, Giandomenico; Sandric, Ionut; Balteanu, D; Micu, Mihai; Ignat, Petru
abstract

Morphodinamic mapping of landslide affected slopes: the case of the Groapa Vantului (Romania)