Finnegan, N. J.; Nereson, A. L.
Earthflows commonly form in steep river canyons and are argued to initiate from rapid incision that destabilizes hill slope toes. At the same time, earthflows are known to exhibit a temporal pattern of movement that is correlated with seasonal precipitation and associated changes in effective stress. In this contribution, we use infinite slope analysis to illuminate the relative roles of topographic slope and climate (via its control on pore fluid pressure) in influencing earthflow motion at Oak Ridge earthflow, near San Jose, CA. To this end, we synthesize two years of shallow (2.7 m depth) pore fluid pressure data and continuous GPS-derived velocities with an 80-year record of historical deformation derived from tracking of trees and rocks on orthophotos along much of the 1.4 km length and 400 m relief of the earthflow. Multiple lines of evidence suggest that motion of Oak Ridge earthflow occurs as frictional sliding along a discrete failure surface, as argued for other earthflows. Spatial patterns of sliding velocity along the earthflow show the same sensitivity to topographic slope for five discrete periods of historical sliding, accelerating by roughly an order of magnitude along a 20 degree increase in earthflow gradient. In contrast, during the 2016-2017 winter, velocity increased much more rapidly for an equivalent increase in driving stress due to pore-fluid pressure rise at our GPS antenna. During this time period, Oak Ridge earthflow moved approximately 30 cm and we observed a relatively simple, non-linear relationship between GPS-derived sliding velocity and shallow pore fluid pressure. Rapid sliding in 2016-2017 (> 0.6 cm/day) occurred exclusively during the week following a large winter storm event that raised pore pressures to seasonal highs within only 1-2 days of the storm peak. These observations suggests that a mechanism, such as dilatant strengthening, acts to stabilize velocities for a given value of pore fluid pressure in the landslide mass
Mackey, B. H.; Roering, J. J.; McKean, J. A.
Abundant glacier-like earthflow features are recognized as a primary erosional process in the highly erodable Franciscan Melange of the Eel River Basin, CA. Despite their prominence in this "melting ice-cream" topography, many questions regarding their effects on the long term sediment flux from this rapidly eroding basin remain unresolved. For example, does an earthflow's basal shear zone propagate vertically downwards with vertical river incision? What controls the upslope and lateral extent of individual earthflows? How does the erosive power of a river influence the rate of earthflow movement, or conversely do earthflow toe deposits regulate the rate of river incision? Here we present preliminary findings derived from study of 200km2 of lidar data (1m resolution) covering hillslopes adjacent to 30km of the Eel River. Lidar allows detailed analysis of the interaction between earthflows and the drainage network, and we document how inferred changes in local base level are propagated throughout adjacent hillslopes via earthflow movement. The most active earthflows (determined by field surveying and analysis of aerial photos rectified using lidar- generated digital topography) coincide with locally steep sections of channel, while downstream of the most active flows we frequently observe less-active or dormant earthflows. This observation supports the idea that the locations of the most active earthflows coincide with headward propagating knickpoints in the channel. The rate of earthflow movement appears to slow when an earthflow exhausts the upslope area of easily mobilized sediment. Earthflow toes can protrude directly into the channel, causing the channel to narrow and steepen, and even undercut the opposite bank. Large resistant boulders (>2m diameter) transported by the earthflow accumulate in the streambed and appear to both act as a check on further channel incision and earthflow movement. In contrast, areas adjacent to active earthflows exhibit smooth
Berti, Matteo; Simoni, Alessandro
Large, deep-seated earthflows are common in mountainous areas where clay soils or fine-grained weak rocks are dominant. Distinctive features of these landslides are the relatively slow movements and the complex style of activity, in which mass flow is accompanied by basal sliding along localized shear zones. Earthflows are subjected to periodic reactivations separated by long intervals of dormancy. Although the dynamics of earthflows is widely documented in the literature, field data on the reactivation process are almost absent because of the difficulty of catching the critical acceleration phase. We document the reactivation of a large, dormant earthflow that occurred in February 2014 in the Northern Apennines of Italy. The Montecchi earthflow is located about 50 km to the south of Bologna, on the left side of the Silla Valley. Slopes are mainly constituted by chaotic sedimentary melanges belonging to the Palombini Shale (lower Cretaceous-Cenomanian). The earthflow first reactivated in November 1994, after an apparently unexceptional precipitation of 95 mm over a week. Surface velocities reached the value of few meters per day during the failure, then the landslide slowed down. One month after the reactivation, the velocity reduced to 1.2 mm/day and five months later it was further decreased to 0.1-0.2 mm/day. In the following years, the landslide became dormant with residual movements in the order of few mm/month. A monitoring system was installed in July 2004 to investigate the slope response to rainfalls and the displacement rates of the landslide during the dormant phase. The monitoring system has been operational for more than 10 years by adapting the number, type, and location of monitoring sensors to the evolving landslide. The monitoring system was operational when, on the 10th of February 2014, the landslide reactivated again. At the time of the failure two monitored sections were operational in the source area (upper section) and in the central part
Booth, Adam M.; Roering, Josh J.
In mountainous terrain, deep-seated landslides transport large volumes of material on hillslopes, exerting a dominant control on erosion rates and landscape form. Here, we develop a mathematical landscape evolution model to explore interactions between deep-seated earthflows, soil creep, and gully processes at the drainage basin scale over geomorphically relevant (>103 year) timescales. In the model, sediment flux or incision laws for these three geomorphic processes combine to determine the morphology of actively uplifting and eroding steady state topographic profiles. We apply the model to three sites, one in the Gabilan Mesa, California, with no earthflow activity, and two along the Eel River, California, with different lithologies and varying levels of historic earthflow activity. Representative topographic profiles from these sites are consistent with model predictions in which the magnitude of a dimensionless earthflow number, based on a non-Newtonian flow rheology, reflects the magnitude of recent earthflow activity on the different hillslopes. The model accurately predicts the behavior of earthflow collection and transport zones observed in the field and estimates long-term average sediment fluxes that are due to earthflows, in agreement with historical rates at our field sites. Finally, our model predicts that steady state hillslope relief in earthflow-prone terrain increases nonlinearly with the tectonic uplift rate, suggesting that the mean hillslope angle may record uplift rate in earthflow-prone landscapes even at high uplift rates, where threshold slope processes normally limit further topographic development.
B. H. Mackey; J. J. Roering; J. A. McKean
Although earthflows are the dominant erosion mechanism in many mountainous landscapes, estimates of long-term earthflow-driven sediment flux remain elusive because landslide displacement data are typically limited to contemporary time periods. Combining high-resolution topography from airborne LiDAR (light detection and ranging), total station surveying, orthorectified...
Guerriero, L.; Coe, Jeffrey A.; Revellio, P.; Grelle, G.; Pinto, F.; Guadagno, F.
We investigated relations between slip-surface geometry and deformational structures and hydrologic features at the Montaguto earth flow in southern Italy between 1954 and 2010. We used 25 boreholes, 15 static cone-penetration tests, and 22 shallow-seismic profiles to define the geometry of basal- and lateral-slip surfaces; and 9 multitemporal maps to quantify the spatial and temporal distribution of normal faults, thrust faults, back-tilted surfaces, strike-slip faults, flank ridges, folds, ponds, and springs. We infer that the slip surface is a repeating series of steeply sloping surfaces (risers) and gently sloping surfaces (treads). Stretching of earth-flow material created normal faults at risers, and shortening of earth-flow material created thrust faults, back-tilted surfaces, and ponds at treads. Individual pairs of risers and treads formed quasi-discrete kinematic zones within the earth flow that operated in unison to transmit pulses of sediment along the length of the flow. The locations of strike-slip faults, flank ridges, and folds were not controlled by basal-slip surface topography but were instead dependent on earth-flow volume and lateral changes in the direction of the earth-flow travel path. The earth-flow travel path was strongly influenced by inactive earth-flow deposits and pre-earth-flow drainages whose positions were determined by tectonic structures. The implications of our results that may be applicable to other earth flows are that structures with strikes normal to the direction of earth-flow motion (e.g., normal faults and thrust faults) can be used as a guide to the geometry of basal-slip surfaces, but that depths to the slip surface (i.e., the thickness of an earth flow) will vary as sediment pulses are transmitted through a flow.
Booth, A. M.; Roering, J. J.
Landscape evolution models can be informative tools for understanding how sediment transport processes, regulated by tectonic and climatic forcing, interact to control fundamental landscape characteristics such as relief, channel network organization, and hillslope form. Many studies have proposed simple mathematical geomorphic transport laws for modeling hillslope and fluvial processes, and these models are capable of generating synthetic landscapes similar to many of those observed in nature. However, deep-seated mass movements dominate the topographic development of many tectonically active landscapes, yet few compelling transport laws exist for accurately describing these processes at the drainage basin scale. Specifically, several detailed field and theoretical studies describe the mechanics of deep-seated earthflows, such as those found throughout the northern California coast ranges, but these studies are often restricted to a single earthflow site. Here, we generalize earthflow behavior to larger spatial and geomorphically significant temporal scales using a mathematical model to determine how interactions between earthflow, weathering, hillslope, and fluvial processes control sediment flux and topographic form. The model couples the evolution of the land surface with the evolution of a weathered zone driven by fluctuations in the groundwater table. The lower boundary of this weathered zone sets the potential failure plane for earthflows, which occur once the shear stress on this plane exceeds a threshold value. Earthflows deform downslope with a non-Newtonian viscous rheology while gullying, modeled with a stream power equation, and soil creep, modeled with a diffusion equation, continuously act on the land surface. To compare the intensities of these different processes, we define a characteristic timescale for each modeled process, and demonstrate how the ratios of these timescales control the steady-state topographic characteristics of the simulated
Prokešová, R.; Kardoš, M.; Tábořík, Petr; Medveďová, A.; Stacke, V.; Chudý, F.
Roč. 224, NOV 1 (2014), s. 86-101 ISSN 0169-555X R&D Projects: GA MŠk LM2010008 Institutional support: RVO:67985891 Keywords : earthflow * surface displacement * strain modelling * DEM differencing * kinematic behaviour Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.577, year: 2013
Prokešová, Roberta; Kardoš, Miroslav; Tábořík, Petr; Medveďová, Alžbeta; Stacke, Václav; Chudý, František
Large earthflow-type landslides are destructive mass movement phenomena with highly unpredictable behaviour. Knowledge of earthflow kinematics is essential for understanding the mechanisms that control its movements. The present paper characterises the kinematic behaviour of a large earthflow near the village of Ľubietová in Central Slovakia over a period of 35 years following its most recent reactivation in 1977. For this purpose, multi-temporal spatial data acquired by point-based in-situ monitoring and optical remote sensing methods have been used. Quantitative data analyses including strain modelling and DEM differencing techniques have enabled us to: (i) calculate the annual landslide movement rates; (ii) detect the trend of surface displacements; (iii) characterise spatial variability of movement rates; (iv) measure changes in the surface topography on a decadal scale; and (v) define areas with distinct kinematic behaviour. The results also integrate the qualitative characteristics of surface topography, in particular the distribution of surface structures as defined by a high-resolution DEM, and the landslide subsurface structure, as revealed by 2D resistivity imaging. Then, the ground surface kinematics of the landslide is evaluated with respect to the specific conditions encountered in the study area including slope morphology, landslide subsurface structure, and local geological and hydrometeorological conditions. Finally, the broader implications of the presented research are discussed with particular focus on the role that strain-related structures play in landslide kinematic behaviour.
DeLong, Stephen B.; Prentice, Carol S.; Hilley, George E.; Ebert, Yael
Remote mapping and measurement of surface processes at high spatial resolution is among the frontiers in Earth surface process research. Remote measurements that allow meter-scale mapping of landforms and quantification of landscape change can revolutionize the study of landscape evolution on human timescales. At Mill Gulch in northern California, USA, an active earthflow was surveyed in 2003 and 2007 by airborne laser swath mapping (ALSM), enabling meter-scale quantification of landscape change. We calculate four-year volumetric flux from the earthflow and compare it to long-term catchment average erosion rates from cosmogenic radionuclide inventories from adjacent watersheds. We also present detailed maps of changing features on the earthflow, from which we can derive velocity estimates and infer dominant process. These measurements rely on proper digital elevation model (DEM) generation and a simple surface-matching technique to align the multitemporal data in a manner that eliminates systematic error in either dataset. The mean surface elevation of the earthflow and an opposite slope that was directly influenced by the earthflow decreased 14 ± 1 mm/yr from 2003 to 2007. By making the conservative assumption that these features were the dominant contributor of sediment flux from the entire Mill Gulch drainage basin during this time interval, we calculate a minimum catchment-averaged erosion rate of 0·30 ± 0·02 mm/yr. Analysis of beryllium-10 (10Be) concentrations in fluvial sand from nearby Russian Gulch and the South Fork Gualala River provide catchment averaged erosion rates of 0·21 ± 0·04 and 0·23 ± 0·03 mm/yr respectively. From translated landscape features, we can infer surface velocities ranging from 0·5 m/yr in the wide upper ‘source’ portion of the flow to 5 m/yr in the narrow middle ‘transport’ portion of the flow. This study re-affirms the importance of mass wasting processes in the sediment budgets of
Lollino, Piernicola; Giordan, Daniele; Allasia, Paolo; Pastor, Manuel
An intense reactivation of a large earthflow (about 6 million m3 of soil debris) took place in Montaguto (Southern Apennines, Italy) between 2005 and 2006 as a consequence of the retrogression of a sliding process in the source area at the top of the slope. The earthflow run-out was approximately 2-2.5 km long, with the landslide mass thickness approximately ranging between 5 m and 30 m. Relevant damages were produced at the toe of the slope, since important infrastructures hereby located were covered by large volumes of landslide detritum. In the transition area, that is just downslope the source area, the landslide soil mass was channelized and transformed into a viscous soil flowing down through a natural depression channel, with an average displacement rate estimated to range between 3 and 7 m/day. In this work an application of the Smoothed Particle Hydrodynamics method has been carried out in order to simulate both the main features of the earthflow propagation, that is the direction and the thickness of the flowing mass, as well as to investigate some factors of the soil mechanical behavior that might have controlled the earthflow mobility. In particular, two different assumptions concerning the soil rheology, i.e. Bingham visco-plasticity and frictional-consolidating soil, the first complying more with the assumption of a flow-like behavior and the latter with a soil-like behavior of the landslide mass, have been made for comparison purposes. Based on the experiences gained from previous authors concerning the in-situ features of similar earthflow soil masses, these landslides are thought to behave more as a viscous fluid during the very first stages of propagation due to phase transition processes and, later on, to recover a soil-like behavior, therefore characterized by sliding mechanism, due to soil consolidation processes. Field evidences of consolidation processes have indeed been observed in situ in recent years based on pore water pressure monitoring
Conoscenti, Christian; Ciaccio, Marilena; Caraballo-Arias, Nathalie Almaru; Gómez-Gutiérrez, Álvaro; Rotigliano, Edoardo; Agnesi, Valerio
In this paper, terrain susceptibility to earth-flow occurrence was evaluated by using geographic information systems (GIS) and two statistical methods: Logistic regression (LR) and multivariate adaptive regression splines (MARS). LR has been already demonstrated to provide reliable predictions of earth-flow occurrence, whereas MARS, as far as we know, has never been used to generate earth-flow susceptibility models. The experiment was carried out in a basin of western Sicily (Italy), which extends for 51 km2 and is severely affected by earth-flows. In total, we mapped 1376 earth-flows, covering an area of 4.59 km2. To explore the effect of pre-failure topography on earth-flow spatial distribution, we performed a reconstruction of topography before the landslide occurrence. This was achieved by preparing a digital terrain model (DTM) where altitude of areas hosting landslides was interpolated from the adjacent undisturbed land surface by using the algorithm topo-to-raster. This DTM was exploited to extract 15 morphological and hydrological variables that, in addition to outcropping lithology, were employed as explanatory variables of earth-flow spatial distribution. The predictive skill of the earth-flow susceptibility models and the robustness of the procedure were tested by preparing five datasets, each including a different subset of landslides and stable areas. The accuracy of the predictive models was evaluated by drawing receiver operating characteristic (ROC) curves and by calculating the area under the ROC curve (AUC). The results demonstrate that the overall accuracy of LR and MARS earth-flow susceptibility models is from excellent to outstanding. However, AUC values of the validation datasets attest to a higher predictive power of MARS-models (AUC between 0.881 and 0.912) with respect to LR-models (AUC between 0.823 and 0.870). The adopted procedure proved to be resistant to overfitting and stable when changes of the learning and validation samples are
Basher, Les; Betts, Harley; Lynn, Ian; Marden, Mike; McNeill, Stephen; Page, Mike; Rosser, Brenda
In geomorphically active landscapes such as New Zealand, quantitative data on the relationship between erosion and soil carbon (C) are needed to establish the effect of erosion on past soil C stocks and future stock changes. The soil C model currently used in New Zealand for soil C stock reporting does not account for erosion. This study developed an approach to characterise the effect of erosion suitable for soil C stock reporting and provides an initial assessment of the magnitude of the effect of erosion. A series of case studies were used to establish the local effect of landslide, earthflow, and gully erosion on soil C stocks and to compare field measurements of soil C stocks with model estimates. Multitemporal erosion mapping from orthophotographs was used to characterise erosion history, identify soil sampling plot locations, and allow soil C stocks to be calculated accounting for erosion. All eroded plots had lower soil C stocks than uneroded (by mass movement and gully erosion) plots sampled at the same sites. Landsliding reduces soil C stocks at plot and landscape scale, largely as a result of individual large storms. After about 70 years, soil C stocks were still well below the value measured for uneroded plots (by 40% for scars and 20-30% for debris tails) indicating that the effect of erosion is very persistent. Earthflows have a small effect on estimates of baseline (1990) soil C stocks and reduce soil C stocks at landscape scale. Gullies have local influence on soil C stocks but because they cover a small proportion of the landscape have little influence at landscape scale. At many of the sites, the soil C model overestimates landscape-scale soil C stocks.
National Oceanic and Atmospheric Administration, Department of Commerce — The slopes above streams and rivers are subjected to a variety of processes that cause them to recede and retreat from the river or stream channel. These processes,...
Full Text Available On 10 March 2010, because of the heavy rainfall in the preceding days, the Montaguto landslide (Southern Italy reactivated, affecting both state road 90 Delle Puglie and the Rome–Bari railway. A similar event occurred on May 2005 and on September 2009. As a result, the National Civil Protection Department (DPC started an accurate monitoring and analysis program. A monitoring project using the GB-InSAR (ground-based interferometric synthetic aperture radar system was emplaced to investigate the landslide kinematics, plan urgent safety measures for risk mitigation and design long-term stabilization work.Here, we present the GB-InSAR monitoring system results and its applications in the observational method (OM approach. GB-InSAR is an established instrument for long-term campaigns aimed at early warning and monitoring during construction works. Our paper further develops these aspects in that it highlights how the OM based on the GB-InSAR technique can produce savings in terms of cost and time in engineering projects without compromising safety. This study focuses on the key role played by the monitoring activities during the design and planning activities, with special reference to the emergency phase.
Ferrigno, Federica; Gigli, Giovanni; Fanti, Riccardo; Intrieri, Emanuele; Casagli, Nicola
On 10 March 2010, because of the heavy rainfall in the preceding days, the Montaguto landslide (Southern Italy) reactivated, affecting both state road 90 Delle Puglie and the Rome-Bari railway. A similar event occurred on May 2005 and on September 2009. As a result, the National Civil Protection Department (DPC) started an accurate monitoring and analysis program. A monitoring project using the GB-InSAR (ground-based interferometric synthetic aperture radar) system was emplaced to investigate the landslide kinematics, plan urgent safety measures for risk mitigation and design long-term stabilization work.Here, we present the GB-InSAR monitoring system results and its applications in the observational method (OM) approach. GB-InSAR is an established instrument for long-term campaigns aimed at early warning and monitoring during construction works. Our paper further develops these aspects in that it highlights how the OM based on the GB-InSAR technique can produce savings in terms of cost and time in engineering projects without compromising safety. This study focuses on the key role played by the monitoring activities during the design and planning activities, with special reference to the emergency phase.
Guerriero, L.; Revellino, R; Grelle, G.; Diodato, N; Guadagno, F.M.; Coe, Jeffrey A.
This paper summarizes the methods, results, and interpretation of analyses carried out between 2006 and 2015 at the Montaguto earth flow in southern Italy. We conducted a multi-temporal analysis of earth-flow activity to reconstruct the morphological and structural evolution of the flow. Data from field mapping were combined with a geometric reconstruction of the basal slip surface in order to investigate relations between basal-slip surface geometry and deformation styles of earth-flow material. Moreover, we reconstructed the long-term pattern of earth-flow movement using both historical observations and modeled hydrologic and climatic data. Hydrologic and climatic data were used to develop a Landslide Hydrological Climatological (LHC) indicator model.
Cerovski-Darriau, C.; Roering, J. J.; Bilderback, E. L.
Base level change can cause differential incision in fluvial networks, driving a transient hillslope response as slopes attempt to adjust to a new base level. Following a shift to a warmer, wetter climate after the Last Glacial Maximum (LGM) (~17.5 ka), the Waipaoa River (NZ) rapidly incised ~120 m leaving perched relict hillslopes that are still adjusting to that base level fall. While previous studies of the Waipaoa basin have only focused on sediment contribution from channel incision or a few individual large earthflows, here we analyze an entire catchment that experiences widespread adjustment due to earthflow activity. In the Mangataikapua catchment—a tributary of the Waipaoa River principally comprised of weak mélange—we see wholesale relaxation of hillslopes due to pervasive post-LGM earthflows. Less than 6% of the mélange area retains relict terrain unaltered by earthflows, exemplifying the importance of including hillslope sediment contribution. Incision has propagated ~9 km upstream along the mainstem of the Mangataikapua (~86% of the channel length) and has created 80 m of relief at the junction with the Waipaoa. Continued adjustment along Mangataikapua tributaries and slopes is evident from knickpoints in the channels and changes in gradient, curvature, and degree of earthflow-altered terrain on the hillslopes. By identifying the location of this transition in channels and on the hillslopes, we can estimate the amount of post-LGM hillslope relaxation. We analyzed 10 major sub-catchments (drainage areas >35,000 m2) in the mélange on the southeastern side of the catchment. We used slope-area plots, in conjunction with normalized steepness index values (ksn) generated with the Stream Profiler (www.geomorphtools.org), to determine the degree to which the tributary channels have adjusted to incision along the mainstem. Preliminary results show an "upper zone" of relict channel morphology with an average curvature value of θ=-0.3 (±0.1 s.d.) and a
Clapuyt, François; Vanacker, Veerle; Schlunegger, Fritz; Van Oost, Kristof
Accurately assessing geo-hazards and quantifying landslide risks in mountainous environments are gaining importance in the context of the ongoing global warming. For an in-depth understanding of slope failure mechanisms, accurate monitoring of the mass movement topography at high spatial and temporal resolutions remains essential. The choice of the acquisition framework for high-resolution topographic reconstructions will mainly result from the trade-off between the spatial resolution needed and the extent of the study area. Recent advances in the development of unmanned aerial vehicle (UAV)-based image acquisition combined with the structure-from-motion (SfM) algorithm for three-dimensional (3-D) reconstruction make the UAV-SfM framework a competitive alternative to other high-resolution topographic techniques. In this study, we aim at gaining in-depth knowledge of the Schimbrig earthflow located in the foothills of the Central Swiss Alps by monitoring ground surface displacements at very high spatial and temporal resolution using the efficiency of the UAV-SfM framework. We produced distinct topographic datasets for three acquisition dates between 2013 and 2015 in order to conduct a comprehensive 3-D analysis of the landslide. Therefore, we computed (1) the sediment budget of the hillslope, and (2) the horizontal and (3) the three-dimensional surface displacements. The multitemporal UAV-SfM based topographic reconstructions allowed us to quantify rates of sediment redistribution and surface movements. Our data show that the Schimbrig earthflow is very active, with mean annual horizontal displacement ranging between 6 and 9 m. Combination and careful interpretation of high-resolution topographic analyses reveal the internal mechanisms of the earthflow and its complex rotational structure. In addition to variation in horizontal surface movements through time, we interestingly showed that the configuration of nested rotational units changes through time. Although
Full Text Available Accurately assessing geo-hazards and quantifying landslide risks in mountainous environments are gaining importance in the context of the ongoing global warming. For an in-depth understanding of slope failure mechanisms, accurate monitoring of the mass movement topography at high spatial and temporal resolutions remains essential. The choice of the acquisition framework for high-resolution topographic reconstructions will mainly result from the trade-off between the spatial resolution needed and the extent of the study area. Recent advances in the development of unmanned aerial vehicle (UAV-based image acquisition combined with the structure-from-motion (SfM algorithm for three-dimensional (3-D reconstruction make the UAV-SfM framework a competitive alternative to other high-resolution topographic techniques. In this study, we aim at gaining in-depth knowledge of the Schimbrig earthflow located in the foothills of the Central Swiss Alps by monitoring ground surface displacements at very high spatial and temporal resolution using the efficiency of the UAV-SfM framework. We produced distinct topographic datasets for three acquisition dates between 2013 and 2015 in order to conduct a comprehensive 3-D analysis of the landslide. Therefore, we computed (1 the sediment budget of the hillslope, and (2 the horizontal and (3 the three-dimensional surface displacements. The multitemporal UAV-SfM based topographic reconstructions allowed us to quantify rates of sediment redistribution and surface movements. Our data show that the Schimbrig earthflow is very active, with mean annual horizontal displacement ranging between 6 and 9 m. Combination and careful interpretation of high-resolution topographic analyses reveal the internal mechanisms of the earthflow and its complex rotational structure. In addition to variation in horizontal surface movements through time, we interestingly showed that the configuration of nested rotational units changes through
Bayer, Benedikt; Simoni, Alessandro; Mulas, Marco; Corsini, Alessandro; Schmidt, David
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
Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel
Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.
Full Text Available Surface features are produced as a result of internal deformation of active landslides, and are continuously created and destroyed by the movement. Observation of their presence and distribution, and surveying of their evolution may provide insights for the zonation of the mass movement in sectors characterized by different behaviour. The present study analyses and describes some example of surface features observed on an active mass movement, the Slumgullion earthflow, in the San Juan Mountains of southwestern Colorado. The Slumgullion earthflow is one of the most famous and spectacular landslides in the world; it consists of a younger, active part which moves on and over an older, much larger, inactive part. Total length of the earthflow is 6.8 km, with an estimated volume of 170 × 10 6 m 3 . Its nearly constant rate of movement (ranging from about 2 m per year at the head, to a maximum of 6–7 m per year at its narrow and central part, to values between 1.3 and 2 m per year at the active toe, and the geological properties of moving material, are well suited for the observation of the development and evolution of surface features. In the last 11 years, repeated surveying at the Slumgullion site has been performed through recognition of surface features, measurements of their main characteristics, and detailed mapping. In this study, two sectors of the Slumgullion earthflow are analysed through comparison of the features observed in this time span, and evaluation of the changes occurred: they are the active toe and an area located at the left flank of the landslide. Choice of the sectors was dictated in the first case, by particular activity of movement and the nearby presence of elements at risk (highway located only 250 m downhill from the toe; and in the second case, by the presence of many surface features, mostly consisting of several generations of flank ridges. The active toe of the landslide is characterized by continuous movement
Clapuyt, François; Vanacker, Veerle; Schlunegger, Fritz; Van Oost, Kristof
During the last years, exploratory research has shown that UAV-based image acquisition is suitable for environmental remote sensing and monitoring. Image acquisition with cameras mounted on an UAV can be performed at very-high spatial resolution and high temporal frequency in the most dynamic environments. Combined with Structure-from-Motion algorithm, the UAV-SfM framework is capable of providing digital surface models (DSM) which are highly accurate when compared to other very-high resolution topographic datasets and highly reproducible for repeated measurements over the same study area. In this study, we aim at assessing (1) differential movement of the Earth's surface and (2) the sediment budget of a complex earthflow located in the Central Swiss Alps based on three topographic datasets acquired over a period of 2 years. For three time steps, we acquired aerial photographs with a standard reflex camera mounted on a low-cost and lightweight UAV. Image datasets were then processed with the Structure-from-Motion algorithm in order to reconstruct a 3D dense point cloud representing the topography. Georeferencing of outputs has been achieved based on the ground control point (GCP) extraction method, previously surveyed on the field with a RTK GPS. Finally, digital elevation model of differences (DOD) has been computed to assess the topographic changes between the three acquisition dates while surface displacements have been quantified by using image correlation techniques. Our results show that the digital elevation model of topographic differences is able to capture surface deformation at cm-scale resolution. The mean annual displacement of the earthflow is about 3.6 m while the forefront of the landslide has advanced by ca. 30 meters over a period of 18 months. The 4D analysis permits to identify the direction and velocity of Earth movement. Stable topographic ridges condition the direction of the flow with highest downslope movement on steep slopes, and diffuse
Anderson, S. P.; Rengers, F. K.; Foster, M. A.; Winchell, E. W.; Anderson, R. S.
Precipitation characteristics influence whether hillslope materials move in rain-splash driven hops, shallow landslides, or in deep-seated failures. While one might expect a particular style of slope failure to dominate in a region, we report on multiple distinctive mass movements on a single ridge, each associated with different weather events. This suggests that understanding climate regulation of denudation rates and hillslope morphology requires quantifying both triggering hydro-climates, and the corresponding hillslope response to the full spectrum of events. We explore these connections on Dakota Ridge, a hogback at the eastern margin of the Colorado Front Range. The dipslope of Dakota Ridge has generated slumps, debris flows, and an earthflow over the last 4 years; Pleistocene-era deep-seated landslides are also evident. We document mass-movements along a 1 km long segment of Dakota Ridge. Weeklong precipitation and flooding in September 2013 produced slumps, each of which displaced 50-100 m3 of mobile regolith several meters downslope, and some of which triggered shallow, relatively non-erosive debris flows. By contrast, a similar precipitation total over the month of May 2015 mobilized an earthflow. The 10 m wide earthflow displaced mobile regolith downslope as much as 10 m over its 150 m length. These recent landslides are dwarfed by a 400 m wide deep-seated landslide that controls slope morphology from ridge crest to toe. Exposure ages (10Be) suggest a late-Pleistocene age for this feature. Although the September 2013 storm produced record-setting rainfall totals at daily, monthly and annual timescales (e.g., annual exceedance probability of <1/1000 for daily totals), the failures from that event, while numerous, were the smallest of all the landslides in the study area. These observations raise the question: what hydro-climatic conditions produce deep-seated, bedrock involved slope failures? Recent storms suggest that within mobile regolith, individual
Guerriero, Luigi; Revellino, Paola; Coe, Jeffrey A.; Focareta, Mariano; Grelle, Gerardo; Albanese, Vincenzo; Corazza, Angelo; Guadagno, Francesco M.
Historical movement of the Montaguto earth flow in southern Italy has periodically destroyed residences and farmland, and damaged the Italian National Road SS90 and the Benevento-Foggia National Railway. This paper provides maps from an investigation into the evolution of the Montaguto earth flow from 1954 to 2010. We used aerial photos, topographic maps, LiDAR data, satellite images, and field observations to produce multi-temporal maps. The maps show the spatial and temporal distribution of back-tilted surfaces, flank ridges, and normal, thrust, and strike-slip faults. Springs, creeks, and ponds are also shown on the maps. The maps provide a basis for interpreting how basal and lateral boundary geometries influence earth-flow behavior and surface-water hydrology.
Petley, D.; Murphy, W.; Bulmer, M. H.; Keefer, D.
There is growing evidence that there is a significant element of cross-slope movement in many large landslide systems. These movements may result in changing states of stress between landslide blocks that can establish complex displacement patterns. Such motions, which are not considered in traditional two-dimensional limit-equilibrium analyses, are important in the investigation of a variety of landslide types, such as those triggered by earthquakes. In addition, these movements may introduce considerable errors into the interpretation of strain patterns as derived from InSAR studies. Finally, even traditional interpretation techniques may lead to the amount of total displacement being underestimated. These observations suggest that a three dimensional form of analysis may be more appropriate for large landslide complexes. The significance of such cross-slope movements are being investigated using a detailed investigation of the Lishan landslide complex in Central Taiwan. This landslide system, which was reactivated in 1990 related to the construction of a hotel. The total recorded movements have been approximately 1.5 m over an area of sliding that is estimated to be 450 m wide and 200 m long. Extensive damage has been caused to roads and buildings within the town. Remediation work has resulted largely in the stabilization of the landslide complex. Detailed geomorphological mapping has revealed that the landslide complex is composed of two main components. The first, immediately upslope of the hotel construction site, is a relatively shallow earthflow. The second, which has formed a large headscarp upslope from the main road in the centre of the town, is a deeper translational slide. Both appear to have been reactivations of previous failures. While the displacement patterns of the earthflow indicate a relatively simple downslope movement, the vectors derived from kinematic analysis of surface features have indicated that the movement of the deeper
Full Text Available Mapping of landslides, quickly providing information about the extent of the affected area and type and grade of damage, is crucial to enable fast crisis response, i.e., to support rescue and humanitarian operations. Most synthetic aperture radar (SAR data-based landslide detection approaches reported in the literature use change detection techniques, requiring very high resolution (VHR SAR imagery acquired shortly before the landslide event, which is commonly not available. Modern VHR SAR missions, e.g., Radarsat-2, TerraSAR-X, or COSMO-SkyMed, do not systematically cover the entire world, due to limitations in onboard disk space and downlink transmission rates. Here, we present a fast and transferable procedure for mapping of landslides, based on change detection between pre-event optical imagery and the polarimetric entropy derived from post-event VHR polarimetric SAR data. Pre-event information is derived from high resolution optical imagery of Landsat-8 or Sentinel-2, which are freely available and systematically acquired over the entire Earth’s landmass. The landslide mapping is refined by slope information from a digital elevation model generated from bi-static TanDEM-X imagery. The methodology was successfully applied to two landslide events of different characteristics: A rotational slide near Charleston, West Virginia, USA and a mining waste earthflow near Bolshaya Talda, Russia.
Chitu, Zenaida; Bogaard, Thom; Busuioc, Aristita; Burcea, Sorin; Adler, Mary-Jeanne; Sandric, Ionut
Like in many parts of the world, in Romania, landslides represent recurrent phenomena that produce numerous damages to infrastructure every few years. Various studies on landslide occurrence in the Curvature Subcarpathians reveal that rainfall represents the most important triggering factor for landslides. Depending on rainfall characteristics and environmental factors different types of landslides were recorded in the Ialomita Subcarpathians: slumps, earthflows and complex landslides. This area, located in the western part of Curvature Subcarpathians, is characterized by a very complex geology whose main features are represented by the nappes system, the post tectonic covers, the diapirism phenomena and vertical faults. This work aims to investigate hydrological pre-conditions and rainfall characteristics which triggered slope failures in 2014 in the Ialomita Subcarpathians, Romania. Hydrological pre-conditions were investigated by means of water balance analysis and low flow techniques, while spatial and temporal patterns of rainfalls were estimated using radar data and six rain gauges. Additionally, six soil moisture stations that are fitted with volumetric soil moisture sensors and temperature soil sensors were used to estimate the antecedent soil moisture conditions.
Bandurin, M. A.; Volosukhin, V. A.; Vanzha, V. V.; Mikheev, A. V.; Volosukhin, Y. V.
At present theoretical substations for fundamental methods of forecasting possible natural disasters and for quantitative evaluating remaining live technical state of landfall dams in the mountain regions with higher danger are lacking. In this article, the task was set to carry out finite-element simulation of possible natural disasters with changes in the climate as well as in modern seismic conditions of operation in the mountain regions of the Greater Caucasus with higher danger. The research is aimed at the development of methods and principles for monitoring safety of possible natural disasters, evaluating remaining live technical state of landfall dams having one or another damage and for determination of dam failure riskiness, as well. When developing mathematical models of mudflow descents by inflows tributaries into the main bed, an intensive danger threshold was determined, taking into consideration geomorphological characteristics of earthflow courses, physico-chemical and mechanical state of mudflow mass and the dynamics of their state change. Consequences of mudflow descents into river basins were simulated with assessment of threats and risks for projects with different infrastructures located in the river floodplain.
Linneman, S. R.
Community - Scientist partnerships take many forms. In the northwest corner of Washington state a large, active, serpentinitic earthflow has, for decades, shed >25,000 m^3/yr of asbestos-rich sediment into a small agricultural stream system. While the landslide, which moves 3 m/yr, and its unusual sediment have much attracted scientific interest, the situation also presents a great opportunity for community - scientist partnerships. The Swift Creek Landslide Observatory (SCLO) (http://landslide.geol.wwu.edu) is a partnership between scientists and technical staff at Western Washington University + local landowners + the state Department of Ecology + Whatcom County Public Works + a local video security firm. SCLO maintains two remote webcams from which current images are posted to the SCLO website hourly. Users can also view archived images from the cameras, create image-compare visualizations, and create time-lapse movies from the eight-year image archive. SCLO is used by local emergency managers and residents to evaluate the threat of debris flows and floods. It is also used by educators to dramatically illustrate hillslope evolution at a variety of time scales.
Dymond, John R.; Herzig, Alexander; Basher, Les; Betts, Harley D.; Marden, Mike; Phillips, Chris J.; Ausseil, Anne-Gaelle E.; Palmer, David J.; Clark, Maree; Roygard, Jon
Much hill country in New Zealand has been converted from indigenous forest to pastoral agriculture, resulting in increased soil erosion. Following a severe storm that hit the Manawatu-Wanaganui region in 2004 and caused 62,000 landslides, the Horizons Regional Council have implemented the Sustainable Land Use Initiative (SLUI), a programme of widespread soil conservation. We have developed a New Zealand version (SedNetNZ) of the Australian SedNet model to evaluate the impact of the SLUI programme in the 5850 km2 Manawatu catchment. SedNetNZ spatially distributes budgets of fine sediment in the landscape. It incorporates landslide, gully, earthflow erosion, surficial erosion, bank erosion, and flood-plain deposition, the important forms of soil erosion in New Zealand. Modelled suspended sediment loads compared well with measured suspended sediment loads with an R2 value of 0.85 after log transformation. A sensitivity analysis gave the uncertainty of estimated suspended sediment loads to be approximately plus or minus 50% (at the 95% confidence level). It is expected that by 2040, suspended sediment loads in targeted water management zones will decrease by about 40%. The expected decrease for the whole catchment is 34%. The expected reduction is due to maturity of tree planting on land at risk to soil erosion. The 34% reduction represents an annual rate of return of 20% on 20 million NZ of investment on soil conservation works through avoided damage to property and infrastructure and avoided clean-up costs.
Larose, E. F.; Mainsant, G.; Carriere, S.; Chambon, G.; Michoud, C.; Jongmans, D.; Jaboyedoff, M.
Clay-rich pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity, which could be detected by monitoring shear wave velocity variations, The ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010, and then again from fall 2011 on. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results are confirmed by analogous small-scale experiments in the laboratory. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.
Roering, Joshua J.; Mackey, Benjamin H.; Handwerger, Alexander L.; Booth, Adam M.; Schmidt, David A.; Bennett, Georgina L.; Cerovski-Darriau, Corina
In mountainous settings, increases in rock uplift are often followed by a commensurate uptick in denudation as rivers incise and steepen hillslopes, making them increasingly prone to landsliding as slope angles approach a limiting value. For decades, the threshold slope model has been invoked to account for landslide-driven increases in sediment flux that limit topographic relief, but the manner by which slope failures organize themselves spatially and temporally in order for erosion to keep pace with rock uplift has not been well documented. Here, we review past work and present new findings from remote sensing, cosmogenic radionuclides, suspended sediment records, and airborne lidar data, to decipher patterns of landslide activity and geomorphic processes related to rapid uplift along the northward-migrating Mendocino Triple Junction in Northern California. From historical air photos and airborne lidar, we estimated the velocity and sediment flux associated with active, slow-moving landslides (or earthflows) in the mélange- and argillite-dominated Eel River watershed using the downslope displacement of surface markers such as trees and shrubs. Although active landslides that directly convey sediment into the channel network account for only 7% of the landscape surface, their sediment flux amounts to more than 50% of the suspended load recorded at downstream sediment gaging stations. These active slides tend to exhibit seasonal variations in velocity as satellite-based interferometry has demonstrated that rapid acceleration commences within 1 to 2 months of the onset of autumn rainfall events before slower deceleration ensues in the spring and summer months. Curiously, this seasonal velocity pattern does not appear to vary with landslide size, suggesting that complex hydrologic-mechanical feedbacks (rather than 1-D pore pressure diffusion) may govern slide dynamics. A new analysis of 14 yrs of discharge and sediment concentration data for the Eel River indicates
Minardo, Aldo; Picarelli, Luciano; Zeni, Giovanni; Catalano, Ester; Coscetta, Agnese; Zhang, Lei; DiMaio, Caterina; Vassallo, Roberto; Coviello, Roberto; Macchia, Giuseppe Nicola Paolo; Zeni, Luigi
Optical fiber distributed sensors have recently gained great attention in structural and environmental monitoring due to specific advantages because they share all the classical advantages common to all optical fiber sensors such as immunity to electromagnetic interferences, high sensitivity, small size and possibility to be embedded into the structures, multiplexing and remote interrogation capabilities , but also offer the unique feature of allowing the exploitation of a telecommunication grade optical fiber cable as the sensing element to measure deformation and temperature profiles over long distances, without any added devices. In particular, distributed optical fiber sensors based on stimulated Brillouin scattering through the so-called Brillouin Optical Time Domain Analysis (BOTDA), allow to measure strain and temperature profiles up to tens of kilometers with a strain accuracy of ±10µɛ and a temperature accuracy of ±1°C. These sensors have already been employed in static and dynamic monitoring of a variety of structures resulting able to identify and localize many kind of failures [2,3,4]. This paper deals with the application of BOTDA to the monitoring of the deformations of a railway tunnel (200 m long) constructed in the accumulation of Varco d'Izzo earthflow, Potenza city, in the Southern Italian Apennine. The earthflow, which occurs in the tectonized clay shale formation called Varicoloured Clays, although very slow, causes continuous damage to buildings and infrastructures built upon or across it. The railway tunnel itself had to be re-constructed in 1992. Since then, the Italian National Railway monitored the structure by means of localized fissure-meters. Recently, thanks to a collaboration with the rail Infrastructure Manager (RFI), monitoring of various zones of the landslide including the tunnel is based on advanced systems, among which the optical fiber distributed sensors. First results show how the sensing optical fiber cable is able
Lyons, N. J.; Gasparini, N. M.; Crosby, B. T.; Wehrs, K.; Willenbring, J. K.
Sediment supply and transport dynamics convey, transform, and destroy climatic and tectonic signals in channels and depositional landforms. The South Fork Eel River (SFER) in the northern California Coast Ranges, USA exhibits characteristics suggestive of transient landscape adjustment: strath terraces, knickpoints, and headwater terrain eroding more slowly than downstream areas. A tectonically-induced uplift wave is commonly invoked as the driver of transience in this region. The wave is attributed to the northward migration of the Mendocino Triple Junction (MTJ). Nested basin-mean erosion rates calculated from 10Be detrital quartz sand increase down the mainstem of the SFER, roughly coinciding with the direction of MTJ migration. This erosion trend is attributed to the proportion of adjusted and unadjusted landscape portions upstream of the locations where the nested 10Be samples were collected. Adjusted and unadjusted landscape portions are separated by a broad knickzone that contains 28% of relief along the mainstem. Knickzone propagation and considerable stream incision is suggested by projection of the upper SFER above the knickzone through the highest flight of strath terraces. Field observations and outcomes of numerical simulations using the Landlab modeling framework are incompatible with uplift modeled as a wave. Alternative uplift and variable sediment flux scenarios more reliably predict the pattern of terraces, knickpoints, and accelerated erosion. In the natural landscape, landforms and erosion rates follow the patterns expected for transient erosion along the mainstem, although a local base level lowering signal is not resolvable in many tributaries. Topographic relief, presence of knickpoints, and rock properties differ in the SFER tributaries. The tributaries draining mélange are over-steepened by boulders detached from hillslopes by earthflows. Here, we propose a framework in which rock properties and sediment size are a key control upon
Carrara, Paul E.
This report presents a preliminary map of landslide deposits in the Mesa Verde National Park area (see map sheet) at a compilation scale of 1:50,000. Landslide is a general term for landforms produced by a wide variety of gravity-driven mass movements, including various types of flows, slides, topples and falls, and combinations thereof produced by the slow to rapid downslope transport of surficial materials or bedrock. The map depicts more than 200 landslides ranging in size from small (0.01 square miles) earthflows and rock slumps to large (greater than 0.50 square miles) translational slides and complex landslides (Varnes, 1978). This map has been prepared to provide a regional overview of the distribution of landslide deposits in the Mesa Verde area, and as such constitutes an inventory of landslides in the area. The map is suitable for regional planning to identify broad areas where landslide deposits and processes are concentrated. It should not be used as a substitute for detailed site investigations. Specific areas thought to be subject to landslide hazards should be carefully studied before development. Many of the landslides depicted on this map are probably stable as they date to the Pleistocene (approximately 1.8-0.011 Ma) and hence formed under a different climate regime. However, the recognition of these landslides is important because natural and human-induced factors can alter stability. Reduction of lateral support (by excavations or roadcuts), removal of vegetation (by fire or development), or an increase in pore pressure (by heavy rains) may result in the reactivation of landslides or parts of landslides.
António de Brum Ferreira
Full Text Available GEODYNAMICS AND NATURAL HAZARDS IN THE AZORES ISLANDS. The central islands of the Azores archipelago exhibit significant volcanic and seismic activity. The most important tectonic structure responsible for this activity seems to be the leaky transform Terceira Rift, a branch of the Azores triple junction separating the Eurasia and Africa plates. In historical time (since the XV century, the most frequent volcanic eruptions were of the hawaiian and strombolian types, but the level of explosivity has occasionally reached subplinian magnitude, as it happened in the Fogo (1563 and Furnas (1630 volcanoes (hydromagmatic eruptions in the calderas. As in other volcanic regions of the world, effusive volcanism is not particularly dangerous in the Azores islands; explosive activity, however, can be catastrophic (ignimbrites formed in some islands over the last millennia. Still, throughout historical time, earthquakes have been the most dangerous natural phenomena in the Azores, sometimes bringing about tragic consequences: in 1757, an earthquake struck the São Jorge island, killing one thousand people (20% of the total population. But the most catastrophic seismic event of all occurred in the island of São Miguel in 1522: an earthquake triggered an earthflow that submerged the capital (Vila Franca do Campo and killed nearly all of its inhabitants (several thousands. Whether or not they are triggered by earthquakes, mass movements are most common along the coast of the islands: huge falls and rotational slides are attested for by the so-called fajãs, detrital platforms on the foot of cliffs that are several hundred meters high; in death-defying fashion, some of these platforms are actually inhabitated.
Vellico, Michela; Sterzai, Paolo; Pietrapertosa, Carla; Mora, Paolo; Berti, Matteo; Corsini, Alessandro; Ronchetti, Francesco; Giannini, Luciano; Vaselli, Orlando
Landslide monitoring is a very actual topic. Landslides are a widespread phenomenon over the European territory and these phenomena have been responsible of huge economic losses. The aim of the WISELAND research project (Integrated Airborne and Wireless Sensor Network systems for Landslide Monitoring), funded by the Italian Government, is to test new monitoring techniques capable to rapidly and successfully characterize large landslides in fine soils. Two active earthflows in the Northern Italian Appenines have been chosen as test sites and investigated: Silla (Bologna Province) and Valoria (Modena Province). The project implies the use of remote sensing methodologies, with particular focus on the joint use of airborne Lidar, hyperspectral and thermal systems. These innovative techniques give promising results, since they allow to detect the principal landslide components and to evaluate the spatial distribution of parameters relevant to landslide dynamics such as surface water content and roughness. In this paper we put the attention on the response of the terrain related to the use of a hyperspectral system and its integration with the complementary information obtained using a thermal sensor. The potentiality of a hyperspectral dataset acquired in the VNIR (Visible Near Infrared field) and of the spectral response of the terrain could be high since they give important information both on the soil and on the vegetation status. Several significant indexes can be calculated, such as NDVI, obtained considering a band in the Red field and a band in the Infrared field; it gives information on the vegetation health and indirectly on the water content of soils. This is a key point that bridges hyperspectral and thermal datasets. Thermal infrared data are closely related to soil moisture, one of the most important parameter affecting surface stability in soil slopes. Effective stresses and shear strength in unsaturated soils are directly related to water content, and
Chesnutt, J. M.; Wegmann, K. W.; Cole, R. D.; Byrne, P. K.
The Grand Mesa in Colorado is one of the largest and highest flat-topped mountains on Earth, and as such provides a compelling analog for Mars' Sacra Mensa. Both basalt-capped landforms are morphologically similar, enabling a landscape evolution comparison between the two that considers key differences in locale, composition, and environmental conditions. Sacra Mensa is nearly 50 times the area of Grand Mesa and towers 3 km above the surrounding area. The 1,300 km2 Grand Mesa rises 2 km above Grand Valley, and is bracketed by the Colorado and Gunnison Rivers in much the same way as Sacra Mensa is bounded by braided channels of Kasei Valles. The sustained incision by the Gunnison and Colorado was a key erosive force in the creation of the Grand Mesa, whereas punctuated but voluminous Hesperian glacio-fluvial floods are thought to have carved the Sacra Mensa. The Grand Mesa is undergoing extensive mass wasting, ranging from deadly landslides like the 2014 West Salt Creek rock avalanche to hundreds of slower-moving retrogressive slump blocks calving off the Miocene basalt cap. The genesis and modification of both landforms includes volcanic and fluvial activity, albeit in an inverted sequence. The Grand Mesa basalt cap has preserved the landform during the incision around its sides, whereas Sacra Mensa was likely carved by floods, with those flood channels later modified by lava flows. Recent (2015-2017) LiDAR surveys revealed massive and possible ancient landslides in many stream valleys and extensive earthflows on all sides of the Grand Mesa. In the case of the Grand Mesa, the large landslides are mainly occurring in one stratigraphic unit. In comparison, the western half of Sacra Mensa contains substantial slumping accompanied by landslides and debris flows, whereas the eastern half has relatively few such phenomena. Here, we report on the first Mesa-Mensa landscape evolution analog study. The surficial and bedrock mapping and 14C dating of key features of the
Carrara, Paul E.
Mesa Verde National Park in southwestern Colorado was established in 1906 to preserve and protect the artifacts and dwelling sites, including the famous cliff dwellings, of the Ancestral Puebloan people who lived in the area from about A.D. 550 to A.D. 1300. In 1978, the United Nations designated the park as a World Heritage Site. The geology of the park played a key role in the lives of these ancient people. For example, the numerous (approximately 600) cliff dwellings are closely associated with the Cliff House Sandstone of Late Cretaceous age, which weathers to form deep alcoves. In addition, the ancient people farmed the thick, red loess (wind-blown dust) deposits on the mesa tops, which because of its particle size distribution has good moisture retention properties. The soil in this loess cover and the seasonal rains allowed these people to grow their crops (corn, beans, and squash) on the broad mesa tops. Today, geology is still an important concern in the Mesa Verde area because the landscape is susceptible to various forms of mass movement (landslides, debris flows, rockfalls), swelling soils, and flash floods that affect the park's archeological sites and its infrastructure (roads, septic systems, utilities, and building sites). The map, which encompasses an area of about 100 mi2 (260 km2), includes all of Mesa Verde National Park, a small part of the Ute Mountain Indian Reservation that borders the park on its southern and western sides, and some Bureau of Land Management and privately owned land to the north and east. Surficial deposits depicted on the map include: artificial fills, alluvium of small ephemeral streams, alluvium deposited by the Mancos River, residual gravel on high mesas, a combination of alluvial and colluvial deposits, fan deposits, colluvial deposits derived from the Menefee Formation, colluvial deposits derived from the Mancos Shale, rockfall deposits, debris flow deposits, earthflow deposits, translational and rotational landslide
Scott, Robert B.; Lidke, David J.; Grunwald, Daniel J.
This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range. Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit. Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the
Guardiani, Carlotta; Amabile, Anna Sara; Jochum, Birgit; Ottowitz, David; Supper, Robert
One of the main precursors for landslide activation/reactivation is intense and prolonged precipitation, with consequent pore water pressure rise due to infiltration of rainfall that seeps into the ground. Monitoring hydrological parameters such as precipitation, water content and pore pressure, in combination with displacement analysis for early warning purposes, is necessary to understand the triggering processes. Since the reduction over time of electrical resistivity corresponds to an increase of water content, electrical resistivity monitoring can help to interpret the modifications of slope saturation conditions after heavy rainfalls. In this study, we present the results of the ERT monitoring data from two landslide areas, Laakirchen (47.961692N, 13.809897E) and Rosano (44.662453N, 9.104703E). During March 2010, a shallow rotational landslide was triggered by snow melting and intense rainfall in Laakirchen, in the vicinity of a newly constructed house. Laakirchen landslide was monitored by geophysical/geotechnical measurements from September 2011 to June 2013. In December 2004, Rosano landslide reactivation affected rural buildings: slope deformations caused mainly damages to properties, infrastructures and lifelines. Rosano landslide has been defined as a composite landslide, with a general dynamic behavior that can be regarded as a slow earthflow. The installation of the monitoring system took place in July 2012 and the data acquisition lasted until April 2015. These sites are part of the geoelectrical monitoring network set up by the Geological Survey of Austria for testing the self-developed GEOMON4D geoelectrical system, in combination with complementary geotechnical monitoring sensors (rain gauge, automatic inclinometer, water pressure and water content sensors) to support the interpretation of the electrical response of the near surface (R. Supper et al., 2014). The measurements were funded by the TEMPEL project (Austrian Science Fund, TRP 175-N21
Fornaciai, Alessandro; Favalli, Massimiliano; Gigli, Giovanni; Nannipieri, Luca; Mucchi, Lorenzo; Intieri, Emanuele; Agostini, Andrea; Pizziolo, Marco; Bertolini, Giovanni; Trippi, Federico; Casagli, Nicola; Schina, Rosa; Carnevale, Ennio
Tha Lavina di Roncovetro landslide is located in the Enza Valley (Reggio Emilia, Italy). It extends from the top of Mount Staffola down to the Tassobbio River. Since the clay fraction is dominant, it follows that the landslide can be considered as a fluid-viscous mudflow, which can reach a down flow maximum rate of 10 m/day. The landslide started between the middle and the end of the XIX century and since then it has had a rapid evolution mainly characterized by the rapid retrogression of the crown to the extent that now reaches the top of Mount Staffola. In the last 20 years, about 100,000 m3 of bedrock descended from the main scarp into the landslide body. The total volume of the landslide is inferred to be of ~ 3×106 m3. In the frame of EU Wireless Sensor Network for Ground Instability Monitoring - Wi-GIM project (LIFE12 ENV/IT/001033), the Roncovetro landslide is periodically monitored by traditional monitoring systems and Unmanned Aerial Vehicle (UAV) survey. In addition, an airborne LIDAR survey and a photographic acquisition from a small aircraft were carried out on April 2014 and October 2014, respectively. The traditional monitoring system consists of a terrestrial laser scanning (TLS) survey and a robotized total station (RTS). TLS acquisitions have focused on the upper and more active sector of the earthflow and were carried out since May 2014. By comparing TLS data taken at different times, the general deformational field of the landslide can be reconstructed and the displacements affecting the retaining structures built on the landslide crown quantified. The time resolution of both TLS and RTS acquisition is about 6 per year. . Three high-resolution photogrammetric surveys performed using an UAV were carried out on November 2014, July 2015 and January 2016. Starting from the acquired photos and applying photogrammetry and Structure From Motion (SFM) algorithms integrated in the Photoscan Agisoft software, the high-resolution 3D models of the
Bertrand, C.; Marc, V.; Malet, J.-P.
and mineralogical analyses or from the literature (kinetics constants). The simulations showed that pH, sulphate and calcium concentrations in groundwater could be reproduced from reasonable assumptions. However, the observed high concentrations in magnesium and sodium were not correctly simulated by the model. Furthermore, a particular anomaly in the Na+ concentration was observed in the most active part of the landslide. Lastly, isotopic investigation showed that groundwater 3H content in this sector was significantly lower than groundwater content in the other parts of the landslide and lower than the mean rainwater content. This result showed that the mean groundwater age in the active part was probably higher than elsewhere in the landslide. All these arguments led us to conclude that groundwater was locally recharged with saline waters from areas outside the watershed, coming up through the bedrock using major discontinuities. This assumption is in agreement with the geological context. de Montety, V., V. Marc, C. Emblanch, J.-P. Malet, C. Bertrand, O. Maquaire, and T. A. Bogaard, 2007, Identifying the origin of groundwater and flow processes in complex landslides affecting black marls: insights from a hydrochemical survey.: Earth Surface Processes and Landforms, v. 32, p. 32-48. Malet, J.-P. and Maquaire, O., 2003. Black marl earthflows mobility and long-term seasonal dynamic in southeastern France. In: Picarelli, L. (Ed). Proceedings of the International Conference on Fast Slope Movements: Prediction and Prevention for Risk Mitigation. Patron Editore, Bologna: 333-340. Maquaire, O., Malet, J.-P., Remaître, A., Locat, J., Klotz, S. and Guillon, J., 2003. Instability conditions of marly hillslopes: towards landsliding or gullying? The case of the Barcelonnette Bassin, South East France. Engineering Geology, 70(1-2): 109-130. Parkhurst, D.L. and Appelo, C.A.J., 1999, User's guide to PHREEQC (version 2)--A computer program for speciation, batch-reaction, one
Valasia Peppa, Maria; Mills, Jon Philip; Moore, Philip; Miller, Pauline; Chambers, Jon
Landslides are recognised as dynamic and significantly hazardous phenomena. Time-series observations can improve the understanding of a landslide's complex behaviour and aid assessment of its geometry and kinematics. Conventional quantification of landslide motion involves the installation of survey markers into the ground at discrete locations and periodic observations over time. However, such surveying is labour intensive, provides limited spatial resolution, is occasionally hazardous for steep terrain, or even impossible for inaccessible mountainous areas. The emergence of mini unmanned aerial vehicles (UAVs) equipped with off-the-shelf compact cameras, alongside the structure-from-motion (SfM) photogrammetric pipeline and modern pixel-based matching approaches, has expedited the automatic generation of high resolution digital elevation models (DEMs). Moreover, cross-correlation functions applied to finely co-registered consecutive orthomosaics and/or DEMs have been widely used to determine the displacement of moving features in an automated way, resulting in high spatial resolution motion vectors. This research focuses on estimating the 3D displacement field of an active slow moving earth-slide earth-flow landslide located in Lias mudrocks of North Yorkshire, UK, with the ultimate aim of assessing landslide deformation patterns. The landslide extends approximately 290 m E-W and 230 m N-S, with an average slope of 12˚ and 50 m elevation difference from N-S. Cross-correlation functions were applied to an eighteen-month duration, UAV-derived, time-series of morphological attributes in order to determine motion vectors for subsequent landslide analysis. A self-calibrating bundle adjustment was firstly incorporated into the SfM pipeline and utilised to process imagery acquired using a Panasonic Lumix DMC-LX5 compact camera from a mini fixed-wing Quest 300 UAV, with 2 m wingspan and maximum 5 kg payload. Data from six field campaigns were used to generate a DEM time