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Magnitude–frequency relation for rockfall scars using a Terrestrial Laser Scanner
Abstract
The analysis of the three-dimensional rockfall scar geometry provides clues for the understanding of the failure mechanisms acting on cliffs, of the conditioning factors, and on the frequency of the events. In this paper, a supervised step-by-step methodology is presented for establishing the statistical magnitude–frequency relation of rockfall scar volumes, using a point cloud from Terrestrial Laser Scanner (TLS) data. The methodology includes a procedure for identifying discontinuity surfaces, calculating the areas of those which are exposed, and the height of rockfall scars. In the estimation of the rockfall scar volume a key issue is the consideration of the minimum spacing of the discontinuity sets to differentiate between step-path surfaces and undulated ones. Having obtained the distributions of both the basal area and height of the scar across the slope, the volume of the rockfall scars is calculated stochastically by multiplication of these two parameters by means of a Monte Carlo simulation. Both distributions of the basal area and of the rockfall scar volume are found to be power-law, with the exponent b ranging from 0.9 to 1.2. The relation obtained might be used as a first approach of rockfall magnitude–frequency curves in large cliffs.
... The recent development of remote sensing techniques, particularly lidar (light detection and ranging), has considerably improved our ability to study rockwall dynamics Guerin et al., 2014;van Veen et al., 2017). Terrestrial laser scanning (TLS) makes it possible to carry out topographical surveys of vast areas with good accuracy and very high resolution Santana et al., 2012;Williams et al., 2018). By comparing the point clouds from several surveys, rock instabilities that occurred between the surveys (e.g. ...
... -Many studies have highlight the strong relationship between rockfall frequency and magnitude (e.g. Guerin et al., 2014Guerin et al., , 2020Rosser et al., 2005;Santana et al., 2012;van Veen et al., 2017;Williams et al., 2018). However, studies into the influence of weather variables on rockwall dynamics focus almost exclusively on rockfall frequency. ...
... Rockfall frequency decreased rapidly with magnitude (Fig. 3a). The frequency-magnitude curves generally fit a power law (Guerin et al., 2014(Guerin et al., , 2020Hungr et al., 1999;Rosser et al., 2005;Santana et al., 2012;van Veen et al., 2017;Williams et al., 2018). In this case, it can be defined as ...
Since 1987, more than 13 200 rockfalls have been inventoried by the ministère des Transports du Québec (MTQ) as having impacted the national road Route 132 in northern Gaspésie. This natural hazard represents a nearly permanent danger for road users. Traditional mitigation measures can be ineffective on poorly consolidated, deformed and highly fractured rockwalls such as those found in northern Gaspésie. To address this issue, implementing preventive risk management based on the factors that trigger rock instabilities could be the most effective method. Earthquake, rainfall and freeze–thaw cycles are commonly considered to be the main rockfall-triggering factors. This study aims to better understand the climatic conditions conducive to rockfalls in northern Gaspésie in order to provide knowledge to implement an appropriate risk management strategy. Three rockwalls were scanned with terrestrial laser scanning (TLS) instruments during specific pre-targeted weather conditions. Over a period of 18 months, 17 surveys have allowed us to identify 1287 rockfalls with a magnitude above 0.005 m3 on a scanned surface of 12 056 m2. In addition, meteorological instruments and a 550 cm thermistor string have been installed directly on a vertical rockwall. It appears that some weather conditions influence the occurrence, frequency and magnitude of rockfalls. In winter, rockfall frequency is 12 times higher during a superficial thaw than during a cold period in which temperature remains below 0 ∘C. In summer, rockfall frequency is 22 times higher during a heavy rainfall event than during a mainly dry period. Superficial freeze–thaw cycles (< 50 cm) cause mostly a high frequency of small-magnitude events, while deeper spring thaw (> 100 cm) results in a high frequency of large-magnitude events. The influence of weather conditions on rockfall frequency and magnitude is crucial in order to improve risk management, since large-magnitude events represent higher potential hazards. This study provides a classification of weather conditions based on their ability to trigger rockfalls of different magnitudes. This knowledge could be used to implement a risk management strategy.
... Recently, many applications of rockfall analysis employing 3D point cloud data produced from TLS or photogrammetry have been developed. In terms of rockfall source detection, Santana et al. [14] and Corominas et al. [15] identify rockfall scars and calculate their volumes, using a point cloud by means of identifying discontinuity surfaces and the minimum spacing between them. Other authors used single point clouds to perform rock cliff stability analysis such as Fanti et al. [16] and Mazzanti et al. [17]. ...
... Remote Sens. 2022,14, 4306 ...
... Remote Sens. 2022, 14, 4306 ...
Rock slope monitoring using 3D point cloud data allows the creation of rockfall inventories, provided that an efficient methodology is available to quantify the activity. However, monitoring with high temporal and spatial resolution entails the processing of a great volume of data, which can become a problem for the processing system. The standard methodology for monitoring includes the steps of data capture, point cloud alignment, the measure of differences, clustering differences, and identification of rockfalls. In this article, we propose a new methodology adapted from existing algorithms (multiscale model to model cloud comparison and density-based spatial clustering of applications with noise algorithm) and machine learning techniques to facilitate the identification of rockfalls from compared temporary 3D point clouds, possibly the step with most user interpretation. Point clouds are processed to generate 33 new features related to the rock cliff differences, predominant differences, or orientation for classification with 11 machine learning models, combined with 2 undersampling and 13 oversampling methods. The proposed methodology is divided into two software packages: point cloud monitoring and cluster classification. The prediction model applied in two study cases in the Montserrat conglomeratic massif (Barcelona, Spain) reveal that a reduction of 98% in the initial number of clusters is sufficient to identify the totality of rockfalls in the first case study. The second case study requires a 96% reduction to identify 90% of the rockfalls, suggesting that the homogeneity of the rockfall characteristics is a key factor for the correct prediction of the machine learning models.
... Given that the systematic assessment of the discontinuity penetration into the rocky slope is practically unfeasible, we alternatively propose a statistical method for evaluating the length and width of (un)interrupted sequences of discontinuity planes. The method uses data for the discontinuity properties that have been previously acquired by measurements on a LIDAR point cloud of the area (Santana et al. 2012). ...
... Known rockfall volumes in the area reach up to 300 m 3 (Pica talus slope, 2003). Santana et al. (2012) estimated the statistical frequency of historical rockfall volumes, assuming that the actual relief Fig. 1 (Left) the couloir of the Santa Coloma on the Solà d´Andorra; (right) four principal discontinuity sets that form the detachable blocks from the slope of the slope face has been shaped as a consequence of the release of rock masses. The main hypothesis of their work has been that the rockfall volume distribution corresponds to the missing mass from the existing scars. ...
... Eight discontinuity sets have been identified via field data collection and scanlines, as well as by the processing of a LiDAR obtained point cloud (Santana et al. 2012). Amongst them, the joint sets F3 (dip dir/dip: 157°/56°) and F5 (182°/47°) are basal sliding planes, which intersect with the two lateral cracks F1 (54°/59°) and F7 (141°/89°), as seen in Fig. 1. ...
There is intrinsic difficulty in the investigation of the largest volume of rockfalls that is expected in an area, which lies in the small number of large events, in registrable times. The maximum credible rockfall size has been associated with the properties of the rock mass discontinuities, as they delimit detachable rock blocks, and in particular with the penetration of those discontinuities that comprise rockfall sliding planes. In highly fractured rock masses, the evaluation of the penetration remains an issue. A probabilistic methodology is proposed, to measure the penetration of potential sliding planes into the interior of a rocky slope. The main hypothesis of the method is that the sliding plane persistence is interrupted along its two directions, at the intersection with two lateral discontinuity sets, as the latter displaces the former. Due to the displacement, the sliding planes are formed by quasi-planes that contain a maximum number of spacings of the intersecting joints, hence their size is restricted. The methodology requires as an input the spacing of the intersecting joint sets. Its application to a granodiorite slope confirms that for the study site, there is a maximum volume of rockfalls, excluding the possibility of large stepped failures and rupture of rock bridges. The maximum calculated persistence for the two existing sliding planes in the study site is, respectively, 28.0 m and 48.5 m. The maximum calculated sliding plane surfaces are, accordingly, 282.5 m2 and 289.3 m2. These results are compared against the observed scar dimensions at the study site, which have been retrieved alternatively, by processing a LiDAR point cloud. The results from the two alternative sources are similar, indicating that the methodology can be efficiently used to assess the sliding plane persistence and the expected maximum rockfall magnitude at the study site.
... Often, these technologies provide advantages over traditional methods of data collection on steep and inaccessible slopes, such as the ability to identify rockfall release points, which can be a large source of uncertainty in developing rockfall magnitude-frequency relationships (Corominas et al., 2018). Change detection performed between sequential lidar scans can be used to identify and characterize rockfall source zones and develop magnitude-frequency relationships for a slope (Rosser et al., 2005;Santana et al., 2012;D'Amato et al., 2013;Guerin et al., 2014;van Veen et al., 2017). These inventories can contain a greater level of detail for rockfalls in the smaller volume ranges relative to traditional field inspections performed from the base of the slope (Dussauge-Peisser et al., 2002); however, it is often difficult to determine the trajectory or ending point of each event, which is affected by the slope materials and geometry, and the characteristics of the failed block, including its lithology (Deere and Miller, 1966). ...
... Often, these technologies provide advantages over traditional methods of data collection on steep and inaccessible slopes, such as the ability to identify rockfall release points, which can be a large source of uncertainty in developing rockfall magnitude-frequency relationships (Corominas et al., 2018). Change detection performed between sequential lidar scans can be used to identify and characterize rockfall source zones and develop magnitude-frequency relationships for a slope (Rosser et al., 2005;Santana et al., 2012;D'Amato et al., 2013;Guerin et al., 2014;van Veen et al., 2017). These inventories can contain a greater level of detail for rockfalls in the smaller volume ranges relative to traditional field inspections performed from the base of the slope (Dussauge-Peisser et al., 2002); however, it is often difficult to determine the trajectory or ending point of each event, which is affected by the slope materials and geometry, and the characteristics of the failed block, including its lithology (Deere and Miller, 1966). ...
... As a part of the Canadian Railway Ground Hazards Research Program, remote sensing data, including terrestrial laser scanning (TLS), airborne laser scanning (ALS) and SfM photogrammetry data, have been collected at the site since 2012. Several studies have been completed using this data with details outlined in Hutchinson et al. (2015), Kromer et al. (2015), van Veen et al. (2017) and Rowe et al. (2018). By performing change detection between sequential lidar scans, we have constructed a detailed database of rockfall events in the canyon for the time period between November 2014 and May 2016 (18 months). ...
Remote sensing techniques can be used to gain a more detailed understanding
of hazardous rock slopes along railway corridors that would otherwise be
inaccessible. Multiple datasets can be used to identify changes over time,
creating an inventory of events to produce magnitude–frequency relationships
for rockfalls sourced on the slope. This study presents a method for using
the remotely sensed data to develop inputs to rockfall simulations, including
rockfall source locations and slope material parameters, which can be used to
determine the likelihood of a rockfall impacting the railway tracks given its
source zone location and volume. The results of the simulations can be
related to the rockfall inventory to develop modified magnitude–frequency
curves presenting a more realistic estimate of the hazard. These methods were
developed using the RockyFor3D software and lidar and photogrammetry data
collected over several years at White Canyon, British Columbia, Canada,
where the Canadian National (CN) Rail main line runs along the base of the slope. Rockfalls
sourced closer to the tracks were more likely to be deposited on the track or
in the ditch, and of these, rockfalls between 0.1 and 10 m3 were
the most likely to be deposited. Smaller blocks did not travel far enough to
reach the bottom of the slope and larger blocks were deposited past the
tracks. Applying the results of the simulations to a database of over 2000
rockfall events, a modified magnitude–frequency can be created, allowing the
frequency of rockfalls deposited on the railway tracks or in ditches to be
determined. Suggestions are made for future development of the methods
including refinement of input parameters and extension to other modelling
packages.
... Consequently, the volume distribution of the rockfall scars can be used as a quantitative proxy for the rockfall volume distribution. The scar volume distribution has been determined indirectly using a stochastic simulation based on the distributions of the observed basal areas and the scar heights (Santana et al. 2012). ...
... The dimensions of the rockfall scars can be determined from a point cloud obtained with a terrestrial laser scanner, TLS. In the Solà d'Andorra, this was carried out at the slope of Borrassica-Forat Negre, following the methodology of Santana et al. (2012). Eight joint sets present in the rock mass were first identified (F1 to Table 4). ...
... The scar heights were measured as intersections of the tension cracks F1 and F7. Eventually, the size distribution of the scars was calculated past a Monte Carlo simulation by the multiplication of the scar areas with the scar heights (see details in Santana et al. 2012). ...
There exists a transition between rockfalls, large rock mass failures, and rock avalanches. The magnitude and frequency relations (M/F) of the slope failure are increasingly used to assess the hazard level. The management of the rockfall risk requires the knowledge of the frequency of the events but also defining the worst case scenario, which is the one associated to the maximum expected (credible) rockfall event. The analysis of the volume distribution of the historical rockfall events in the slopes of the Solà d’Andorra during the last 50 years shows that they can be fitted to a power law. We argue that the extrapolation of the F-M relations far beyond the historical data is not appropriate in this case. Neither geomorphological evidences of past events nor the size of the potentially unstable rock masses identified in the slope support the occurrence of the large rockfall/rock avalanche volumes predicted by the power law. We have observed that the stability of the slope at the Solà is controlled by the presence of two sets of unfavorably dipping joints (F3, F5) that act as basal sliding planes of the detachable rock masses. The area of the basal sliding planes outcropping at the rockfall scars was measured with a terrestrial laser scanner. The distribution of the areas of the basal planes may be also fitted to a power law that shows a truncation for values bigger than 50 m² and a maximum exposed surface of 200 m². The analysis of the geological structure of the rock mass at the Solà d’Andorra makes us conclude that the size of the failures is controlled by the fracture pattern and that the maximum size of the failure is constrained. Two sets of steeply dipping faults (F1 and F7) interrupt the other joint sets and prevent the formation of continuous failure surfaces (F3 and F5). We conclude that due to the structural control, large slope failures in Andorra are not randomly distributed thus confirming the findings in other mountain ranges.
... This way, F st (V) describes the cliff activity in terms of the pursued McF. Multiple rockfall hazard studies in the last 25 years [19,[44][45][46][47][48][49][50][51][52][53] have established that the distribution of detached volumes can be adjusted by a power law such as F st (V) = A st ·V −B , in which two parameters describe the rockfall activity of the rock cliff: ...
... To identify the threshold at which this roll-over effect is noticeable in the sample, an empirical method is applied equivalent to the considerations made by other authors [48,77], which are simpler than those presented by [21]. We use a progressive cut on the sample, starting from the minimum volume and increasing the sense to find the point where the potential fitting is stable. ...
Quantitative hazard analysis of rockfalls is a fundamental tool for sustainable risk management, even more so in places where the preservation of natural heritage and people’s safety must find the right balance. The first step consists in determining the magnitude-frequency relationship, which corresponds to the apparently simple question: how big and how often will a rockfall be detached from anywhere in the cliff? However, there is usually only scarce data on past activity from which to derive a quantitative answer. Methods are proposed to optimize the exploitation of multi-source inventories, introducing sampling extent as a main attribute for the analysis. This work explores the maximum possible synergy between data sources as different as traditional inventories of observed events and current remote sensing techniques. Both information sources may converge, providing complementary results in the magnitude-frequency relationship, taking advantage of each strength that overcomes the correspondent weakness. Results allow characterizing rockfall detachment hazardous conditions and reveal many of the underlying conditioning factors, which are analyzed in this paper. High variability of the hazard over time and space has been found, with strong dependencies on influential external factors. Therefore, it will be necessary to give the appropriate reading to the magnitude-frequency scenarios, depending on the application of risk management tools (e.g., hazard zoning, quantitative risk analysis, or actions that bring us closer to its forecast). In this sense, some criteria and proxies for hazard assessment are proposed in the paper.
... Resulting point clouds can be used for rock slope structural analyses (Riquelme et al. 2017;Monsalve et al. 2019), estimation of unstable blocks dimensions (Gigli et al. 2014;Riquelme et al. 2015), or surface roughness estimation (Mills and Fotopoulos 2013;Zhang et al. 2017). Unlike classical methods, such as geological compass measurement, TLS scan observes structural element trace, from which average spatial orientation is later calculated (Santana et al. 2012). TLS allows rockfall event identification with the following volume estimation (Abellan et al. 2009;Santana et al. 2012). ...
... Unlike classical methods, such as geological compass measurement, TLS scan observes structural element trace, from which average spatial orientation is later calculated (Santana et al. 2012). TLS allows rockfall event identification with the following volume estimation (Abellan et al. 2009;Santana et al. 2012). Compared with traditional rockfall volume estimation methods, TLS is faster and collects data with a greater spatial resolution (Gigli et al. 2014). ...
Modern methods to characterise rock masses and monitor rockfalls and rock slope stability are evolving incredibly fast during the last decade. The rapid increase in new techniques, miniaturization, affordability, computational power, or remote sensing data availability allows deployment in more areas in higher amounts with higher frequency and accuracy of acquisition. The current rapid development of monitoring methods is also induced by engineering challenges when new infrastructures are being constructed in more complicated geological conditions, like mountainous areas or deep gorges with steep slopes. This chapter brings an overview of modern methods used for rock mass characterisation and rockfall monitoring and shows the basic needs for complex monitoring systems and data processing. Finally, it describes the main groups of monitoring methods based on cluster analysis and principal trends in research papers related to modern methods in rock mass characterisation and rockfall monitoring.
... Consideration of very small blocks can cause underestimation of the protection designs and barrier capacity. Santana et al. (2012) also mentioned the censoring of small volumes in frequency-volume distribution due to under-sampling or physiographic limitations. Therefore, to eliminate the rollover effect of very small block volumes on distribution fitting, (Fig. 6a). ...
... Mavrouli and Corominas 2017;Ferrero et al. 2016; Ruiz-Carulla et al. 2015;Mavrouli et al. 2015;Hantz 2011;Santana et al. 2012;Dussauge-Peisser et al. 2002). ...
Rock block characteristics are the controlling factors that define the potential rockfall volume, associated hazard and design of preventive practices. The present study defines a methodology to demonstrate the impact of block characteristics on rockfall hazard and its implications on the design of mitigative measures by analysing a recurring rockfall site along a critical highway corridor in NW Himalaya, India. The field data were quantitatively characterised for statistical distributions of size and volume of in situ as well as rockfall blocks. Possible block failures and rockfall initiation zones were predicted using modified kinematic analysis and distinct element method. The size and volume distributions as well as shapes were simulated against these predicted initiation zones to determine the cumulative impact of block characteristics on rockfall hazard by analysing the block kinetics and trajectories. It is found that the block initiation zones majorly govern the relative bounce height, kinetic energy, run-out distance and impact down the slope respective of block sizes and associated mass coupled with slope geometry. However, the effect of block shapes is observed to be minor compared to the blocks greater than a particular size range. Therefore, the design of rockfall protection such as barrier can be more effective when considering the kinetic energies of such block size range assisted by initiation zones. This study proposed that the knowledge of block size frequencies and rockfall initiation zones could provide a rational threshold for which a protection strategy can be designed and optimised to prevent rockfall hazard along the Himalayan highway corridors.
... Surface shapes are represented with more detail according to the scan densities, usually one point each few centimeters. HRDOMs contain fracture surfaces with sufficient detail to capture and reconstruct them digitally, keeping most of their geometrical characteristics (García-Sellés et al., 2011;Santana et al., 2012). ...
... During the process, the applied algorithms calculate the degree of coplanarity and collinearity for each TLS data point in order to obtain its position with respect to a planar surface. The vectorized points belonging to a surface of the same fracture are grouped into individual clusters and converted into planes ( Figure 5; Santana et al., 2012). The planes maintain the geometrical properties (length, height, and area), position (through the central point or centroid), and orientation. ...
Tight fractured sandstones of the Devonian Huamampampa Formation are associated with large gas discoveries in the sub-Andean fold-and-thrust belt of southern Bolivia. A LIDAR-based fracture characterization of the Abra del Condor backlimb anticline, a structural- stratigraphic analog, is used as the basis for a fracture stratigraphy determination. Fracture characterization using LIDAR is integrated with outcrop scanlines and is framed by stratigraphy and structural positions within this thrust-related anticline. SEFL software was used to process LIDAR data, dividing the outcrop by orientations. A workflow to extract modeled fracture planes and their associated orientations, lengths, and heights results in five fracture sets, partially validated by fracture outcrop scanlines. Multiple virtual scan-lines are used to measure fracture intensity, identify fracture stratigraphic units, and define fracture-associated parameters of abundance and size distribution.
Our LIDAR-based fracture characterization indicates a distribution of fracture intensities according to their structural position, decreasing from the hinge to the backlimb. From the five fracture sets identified, one set of orthogonal fractures dominates. Moreover, most of the fractures are contained or bounded within their fracture stratigraphic units and calculated fracture spacing ratio and the fracture space index show a nonexistent relation between fracture spacing and the fracture stratigraphic unit thickness.
... Kinematic and structural analysis using LiDAR data is accomplished by extracting prominent fracture features (Lato et al. 2009;Sturzenegger and Stead 2009;. Furthermore, comparisons of LiDAR data collected over successive time periods allows for the quantification of failed rockfalls, identification of source areas, quantification of rockfall history and the calculation of failure probability Abellán et al. 2011;Santana et al. 2012;. Additionally, monitoring pre-failure deformation of landslides has been conducted with ground-based remote sensing technologies such as TLS , with combined stereo photogrammetry and aerial LiDAR approaches (Dewitte et al. 2008), with satellite interferometric synthetic aperture radar (SAR) (Vallone et al. 2008;Perski et al. 2009), and with ground-based interferometric synthetic aperture radar (GB InSAR) (Tarchi et al. 2003;Gischig et al. 2009;Bozzano et al. 2011). ...
... Terrestrial Laser Scanning (TLS) has become a useful tool for the assessment of rockfall hazard both at larger scales ) and in the lower volume range of 1-1000 m 3 , Lim et al. 2006, Lato et al. 2009Santana et al. 2012;Sturzenegger et al. 2014; ) and has the potential to be used for the prediction of rockfall location , potential volume and kinematics ) and possible timing of failure . ...
Rockfalls threaten communities and infrastructure in mountainous regions worldwide and have been a particularly problematic hazard along the transportation corridors in western Canada. These types of failures are traditionally managed using rockfall hazard management frameworks that are based on a historical analysis of rockfall activity. These frameworks do not fully consider the complexity of the natural rock slopes, nor indicate where and when a potential failure may occur. Terrestrial Laser Scanning (TLS) has been beneficial for monitoring and assessing rock slope hazards and has the potential to identify incipient signs of rock slope failure.
The aim of this thesis is to use TLS to better manage rockfall hazard along transportation corridors by including quantitative measures of precursor activity into hazard analysis strategies and through the development of near-real time automated TLS systems for early warning purposes.
In the first part of the thesis, monitoring at 2-3-month intervals was conducted with TLS at a variety of rock slopes located along the CN Rail line in the Thompson River valley over the four-year duration of this research. Over one hundred rockfalls in the range of 0.1 to 4200 m3, exhibiting precursor activity in the form of pre-failure deformation, smaller precursor rockfalls and tension crack openings were studied and compiled into a database. The approach included: (i) identifying potential rockfall source zones based on incipient signs of failure; (ii) tracking kinematics in three dimensions to better understand the mechanisms of failure; (iii) estimating potential failure volumes based on bounding joint structure; and (iv) transmitting this information to the railway operator for an assessment of risk.
The second part of the thesis focused on monitoring at near continuous levels, which is required to identify the accelerating phase prior to rockfall failure which is necessary to forecast failure time in early warning systems. A complete series of analysis tools was developed to process and analyze TLS data autonomously in near real-time. This included tools to filter outliers, register point clouds, conduct change detection using spatial and temporal neighbourhood averaging and to display time series of deformation. The system was tested for a 6-week period at a rockslide in the French alps.
The contributions in this thesis (i) enhance current rockfall hazard analysis methods by including quantitative measurements of precursor activity, (ii) improve our understanding of the pre-failure stage of rock slope failures and (iii) opened the door for future studies of rock slope failure at a high temporal density using TLS.
... A review of the literature shows that landslide magnitude is mostly used to describe the size in terms of volume for debris flows (e.g., Hungr et al. 1999;Hupp 1984;Innes 1985;Jakob 2005;Stoffel 2010;Zimmermann et al. 1997), rockfalls (e.g. Agliardi et al. 2009;Douglas 1980;Santana et al. 2012;Williams et al. 2018) and slides ). In addition, in the last few decades, there has been a growing interest in the analysis of the relationship between the size (either volume or area) and the associated frequency of landslides (cumulative or not), in a similar way to earthquakes and floods. ...
Significant effort has been devoted during the last few decades to the development of methodologies for landslide hazard and risk assessment. All of this work requires harmonization of the methodologies and terminology to facilitate communication within the landslide community, as well as with stakeholders and researchers from other disciplines. Currently, glossaries, and methodological recommendations exist for preparing landslide hazard and risk studies. Nevertheless, there is still debate on the usage of some terms and their implementation in practice.
In 2016, the IAEG commission C-37 established a working group with the objective of preparing a standard multilingual glossary of landslide hazard and risk terms. The glossary aims for the international harmonization of the terms and definitions with those used in associated disciplines (e.g., seismology, hydrology) while considering landslides specifically. The glossary is based on previously published glossaries, including those prepared by ISSMGE TC32, FedIGS, JTC1, and UNISDR. This article presents comments on the meaning of some of the terms that have required further discussion. The English version of the glossary is also included.
... Ravanel and Deline (2013) implemented an observation system in the Alpine mountains specifically designed to record instances of rock failure. The magnitude-frequency relations of landslides (Brunetti et al., 2009;Dussauge et al., 2002Dussauge et al., , 2003Malamud et al., 2004;Stark and Hovius, 2001) (related to surface area or volume) or rockfalls (Guzzetti et al., 2003;Hantz et al., 2003;Hungr et al., 1999;Larsen et al., 2010;Santana et al., 2012) (related to volume) is found often sufficiently depicted by power-law distribution over a limited range, which means that smaller landslides occur more frequently than larger ones. This distribution can be influenced by various factors, including geological context, triggering events such as rainfall or earthquakes, and local environmental conditions, resulting in a various scaling parameter (b) of fitted power laws between 0.4 and 0.9 for rock slope instability (Corominas et al., 2018). ...
... In the literature, there are two approaches to the assessment of block volume distribution: the first one is based on surveys of rock faces aiming at identifying potentially detachable blocks (Santana et al., 2012;Mavrouli et al., 2015;Mavrouli and Corominas, 2017), and the second one is based on surveys of the fallen blocks (van Veen et al., 2017;DiFrancesco et al., 2021). The distribution obtained based on the results of the geomechanical survey allows one to consider the volume as a continuous random variable. ...
Block size and shape depend on the state of fracturing of the rock mass and, consequently, on the geometrical features of the discontinuity sets (mainly orientation, spacing, and persistence). The development of non-contact surveying techniques applied to rock mass characterization offers significant advantages in terms of data numerosity, precision, and accuracy, allowing for performing a rigorous statistical analysis of the database. This fact is particularly evident when dealing with rockfall phenomena: uncertainties in spacing and orientation data could significantly amplify the uncertainties connected with in situ block size distribution (IBSD), which represents a relation between each possible value of the volume and its probability of not being exceeded. In addition to volume, block shape can be considered as a derived parameter that suffers from uncertainties. Many attempts to model the possible trajectories of blocks considering their actual shape have been proposed, aiming to reproduce the effect on motion. The authors proposed analytical equations for calculating the expected value and variance of volume distributions, based on the geometrically correct equation for block volume in the case of three discontinuity sets. They quantify and discuss the effect of both volume and shape variability through a synthetic case study. Firstly, a fictitious rock mass with three discontinuity sets is assumed as the source of rockfall. The IBSDs obtained considering different spacing datasets are quantitatively compared, and the overall uncertainty effect is assessed, proving the correctness of the proposed equations. Then, block shape distributions are obtained and compared, confirming the variability of shapes within the same IBSD. Finally, a comparison between trajectory simulations on the synthetic slope is reported, aiming to highlight the effects of the propagation of uncertainties to block volume and shape estimation. The benefits of an approach that can quantify the uncertainties are discussed from the perspective of improving the reliability of simulations.
... To inventory events that occur, terrestrial or aerial laser scanning (TLS or ALS) and photogrammetry are frequently used to obtain surface models of the terrain, the position of the deposited block fragments, an estimation of the detachment volume, the fragment trajectories, etc. [7,8]. These techniques are used to quantify detached rock masses on rock slopes over time to estimate the expected magnitude frequency of rockfall [9][10][11][12][13][14], which is required to evaluate risk quantitatively [15,16]. For early warning purposes, ground-based radar interferometry [17], seismic signals [18] and acoustic signals [19] have proven useful in a variety of hazardous scenarios. ...
An automated, fixed-location, continuous time-lapse camera system was developed to analyze the existence of rockfall precursory movements and quantify volume changes after detachments. It was implemented to monitor the basaltic formation on which Castellfollit de la Roca village is built. Due to the geometrical conditions of the area, the camera system consists of three digital cameras managed by a control unit that contains a Raspberry Pi 4 microprocessor. Images taken every day are sent to a server for processing. A workflow has been developed to work with a set of images with an irregular time interval to detect precursor movement. The first step consists of matching the images with a reference master image and filtering the vegetation to improve the process using a mask obtained by a green leaf index (GLI) index. Then, the adjusted images are used for a forward-backward correlation process carried out to detect movements. If movement is detected, a 3D model is built using structure from motion (SfM) to quantify the movements. The system has been working since September 2021. During this period, movements from 0.01 to 0.5 m and several rockfalls of a small volume have been detected.
... Approximately since the beginning of the century, techniques such as Laser Scanning (LiDAR) and digital photogrammetry have made it possible to obtain 3D models of sites of interest (e.g., slopes, open pits, tunnels and dams) with increasing speed, ease and versatility. Improvements in high resolution point cloud acquisition can be followed, for instance, in [1][2][3][4][5][6][7][8][9][10][11]. ...
In the last two decades, both the amount and quality of geoinformation in the geosciences field have improved substantially due to the increasingly more widespread use of techniques such as Laser Scanning (LiDAR), digital photogrammetry, unmanned aerial vehicles, geophysical reconnaissance (seismic, electrical, geomagnetic), and ground-penetrating radar (GPR), among others. Furthermore, the advances in computing, storage and visualization resources allow the acquisition of 3D terrain models (surface and underground) with unprecedented ease and versatility. However, despite these scientific and technical developments, it is still a common practice to simplify the 3D data in 2D static images, losing part of its communicative potential. The objective of this paper is to demonstrate the possibilities of extended reality (XR) for communication and sharing of 3D geoinformation in the field of geosciences. A brief review of the different variants within XR is followed by the presentation of the design and functionalities of headset-type mixed-reality (MR) devices, which allow the 3D models to be investigated collaboratively by several users in the office environment. The specific focus is on the functionalities of Microsoft’s HoloLens 2 untethered holographic head mounted display (HMD), and the ADA Platform App by Clirio, which is used to manage model viewing with the HMD. We demonstrate the capabilities of MR for the visualization and dissemination of complex 3D information in geosciences in data rich and self-directed immersive environment, through selected 3D models (most of them of the Montserrat massif). Finally, we highlight the educational possibilities of MR technology. Today MR has an incipient and reduced use; we hope that it will gain popularity as the barriers of entry become lower.
... En este sentido, el uso de superficies del terreno como nubes de puntos 3D de alta resolución, conteniendo una información más precisa y densa, está cambiando los enfoques clásicos de investigación, monitorización y modelización de los fenómenos naturales a diferentes escalas espaciales y temporales. Esta evolución se puede seguir en la bibliografía geocientífica desde Janeras et al. (2004), Buckley et al. (2008), Jaboyedoff et al. (2012), Santana et al. (2012), Bemis et al. (2014), Riquelme et al. (2015), Williams et al. (2018), Ruiz et al. (2020) hasta Pugsley et al. (2021). ...
La revolución experimentada por el uso creciente de la geoinformación 3D en la ingeniería geológica, gracias a los avances tecnológicos, que progresivamente han facilitado una disponibilidad de técnicas de adquisición de datos y de herramientas para su análisis. Junto a los avances experimentados en la disponibilidad de recursos de computación y almacenamiento en la nube, han impulsado la expansión de numerosas aplicaciones que permiten la difusión de la geoinformación 3D en la web. A pesar de estos avances científico-técnicos, es común ver los datos 3D simplificados en imágenes estáticas 2D, perdiendo parte su potencialidad comunicativa. El objetivo de esta comunicación es presentar el diseño y las funcionalidades de unos visores web 3D de código abierto como una herramienta de sencilla utilización con la que interactuar y visualizar los resultados. Así mismo, estamos ensayando las posibilidades de la realidad mixta como una experiencia plenamente inmersiva para lograr una mejor comunicación de la geoinformación 3D.
... As it is unlikely to witness a real rockfall event, most rockfall inventories concentrate on studying the source point and the spread of the debris over the deposit area, both surveyed well after the occurrence of the event (Abellán et al. 2006;Santana et al. 2012;Ruiz-Carulla et al. 2015, 2016a. ...
Fragmentation is a common feature of rockfall that exerts a strong control on the trajectories of the generated blocks, the impact energies, and the runout. In this paper, we present a set of four real-scale rockfall tests aimed at studying the fragmentation of the rocky blocks, from the global design of the field procedure to the data analysis and the main results. A total of 124 limestone, dacite, or granite blocks ranging between 0.2 and 5 m ³ were dropped from different heights (8.5 to 23.6 m) onto four slopes with different shapes (single or double bench) and slope angles (42º to 71º). The characteristics of the blocks, in particular the size, surface texture and joint condition, were measured before the drops. The trajectories of the blocks and both the initial and the impact velocities were tracked and recorded by means of three high-speed video cameras. A total of 200 block-to-ground impacts have been studied. On average, 40% of the blocks broke upon impact on the slope or on the ground, making it necessary to measure the fragments. The initial and final sizes of the blocks/fragments were measured by hand with tape, though photogrammetric techniques (UAV and terrestrial) were also used for comparison purposes. The information gathered during the field tests provides a deep insight into the fragmentation processes. On the one hand, the high-resolution slow-motion videos help to describe when and how the block breakage takes place and the spatial distribution of the pieces. On the other hand, it is possible to compute the block trajectories, the velocities, and the energy losses using videogrammetry. The results include, for instance, a block average fragmentation of 54% and 14% for the limestone and granitoids, respectively; the systematic inventory of the size fragments, which may be used for fitting the power law distributions; and after each breakage, the total angle of aperture occupied by the fragments has been measured, with values in the range 25º–145º. To figure out the different behavior of the blocks in terms of breakage/no breakage, each block-to-ground impact has been characterized with a set of parameters describing the energy level, the robustness of the substrate, and the configuration of the block contact at the impact point, among others. All these terms are combined in a function F , which is used to adjust the field data. The adjustment has been carried out, first, for the whole 200 events and later for a subset of them. The procedure and the results are described in the paper. Although the discrimination capability of F is moderately satisfactory, it is very sensitive to the test site and setup. It must be highlighted that these field tests are a unique source of data to adjust the parameters of the numerical simulation models in use for rockfall studies and risk mitigation, especially when fragmentation during the propagation is considered.
... The adopted classification is consistent with rockfall volume distributions that have been developed for artificial slope to describe the relative frequency of rockfall events of different sizes and consequences and that is often obtained by fitting historical data to an inverse power law (Santana et al. 2012). Figure 1 shows the conceptual relation between an annual cumulative frequency vs. rockfall volume curve and the annual frequencies used in the proposed classification. ...
Numerous rockfall incidents involving infrastructure damage and loss of life have been reported along roads in mountainous terrain. Previous studies have used quantitative risk assessment approaches to identify the level of rockfall risk. However, appropriate quantitative indicators that are able to describe time-varying risk have not yet been developed. This study aims to develop a rockfall risk mitigation method based on reliability concepts, to classify rockfall data, to model the probability of rockfall occurrence, and to estimate the magnitude of risk reduction through mitigation measures. A synthetic measure of rockfall risk is proposed, which allows to compare directly and quantitatively the rockfall risk for different cut slopes under unmitigated and mitigated conditions. The proposed methodology can estimate the risk reduction obtained using mitigation measures, such as introducing protections barriers, their periodic maintenance, and horizontal coverage ratio. This methodology was applied to 20 years of rockfall data collected by the Korea Expressway Corporation from 1215 artificial cut slopes along the highway network in South Korea. The rockfall frequency was analyzed based on the inventory data, and a rockfall hazard mitigation strategy was demonstrated using the suggested methodology for the case study. It was shown that appropriate mitigation strategies, based on number of protection barriers, interval of periodic maintenance, and horizontal coverage ratio, can be devised to reduce the risk of different artificial slopes below a target failure probability. The approach shown in this study can provide insights into ways of improving overall risk management to prevent losses by rockfall.
... The observed volumefrequency exponent β of 0.80 (Eq. (2); Fig. 6b) is within the typical range (0.4-1.1) for mass movements (Santana et al., 2012). The relatively high β characterizing Orange County erosion features suggests more smaller, shallower erosion events, while the low β characterizing erosion in Humboldt and Del Norte Counties suggests a higher relative proportion of larger, deeper landslides, or event superposition (Table 7). ...
Quantifying coastal cliff erosion is critical for improved predictions of coastal change and for coastal management. However, few studies have been conducted at a scale (>100 km) and resolution (~1 m) sufficient to constrain regional change. Here, we quantified cliff erosion for 866 km of the California coastline using airborne LiDAR data collected in 2009-2011 and 2016. A semi-automated method was used to map cliff faces. Negative (volume loss) and positive (volume gain) change objects were created by grouping adjacent cells using vertical and area change thresholds and surface optical signatures. We assessed the performance of five machine learning algorithms to separate erosion and deposition from other changes within the cliff face, notably vegetation loss and growth, and found that discriminant analysis performed best. After applying the classification method to the entire cliff change dataset, the results were visually inspected for quality control, producing a final dataset comprised of 45,699 erosion and 1728 deposition objects. The net volume loss from 2009-2011 to 2016 was 1.24 × 10⁷ m³, equivalent to an erosion rate of 2.47 m³ yr⁻¹ per meter of coastline, and an average cliff retreat rate of 0.06 m yr⁻¹. Eroded volumes ranged from 6.43 m³ to 7.52 × 10⁵ m³ and fit a power-law frequency distribution (β = 0.80; r² = 0.99). Over this study period, 7% of eroded material was retained on the cliff face. Cliff retreat rates varied spatially with the highest rates in Humboldt County (0.18 m yr⁻¹) and the lowest in Orange County (0.003 m yr⁻¹).
... In the past decade, TLS has become a commonly used method for slope monitoring and rockmass characterization [1,[9][10][11]. As the amount of research in this field has increased, many applications of TLS have been developed including modelling rockfall volumes and fall scarps [1,9,12,13], conducting hazard and risk surveys [1,14,15] and analyzing trends using magnitude-frequency curves [16][17][18][19][20]. Recent studies have used TLS to generate rockfall databases, which can subsequently be used for various types of analyses [18,21,22]. ...
While terrestrial laser scanning and photogrammetry provide high quality point cloud data that can be used for rock slope monitoring, their increased use has overwhelmed current data analysis methodologies. Accordingly, point cloud processing workflows have previously been developed to automate many processes, including point cloud alignment, generation of change maps and clustering. However, for more specialized rock slope analyses (e.g., generating a rockfall database), the creation of more specialized processing routines and algorithms is necessary. More specialized algorithms include the reconstruction of rockfall volumes from clusters and points and automatic classification of those volumes are both processing steps required to automate the generation of a rockfall database. We propose a workflow that can automate all steps of the point cloud processing workflow. In this study, we detail adaptions to commonly used algorithms for rockfall monitoring use cases, such as Multiscale Model to Model Cloud Comparison (M3C2). This workflow details the entire processing pipeline for rockfall database generation using terrestrial laser scanning.
... 2009, Yılmaz vd. 2005, Wang et al. 2012, Santana et al. 2012, Öztürk vd. 2017, Akgül vd. ...
... Figure 7 shows the magnitude-frequency relationship of the series of computed volumes from the identified rockfall sources with different complex shapes, between Fall 2012 and Spring 2013, illustrated in Figure 6B. Figure 7 outlines the influence of the α value on each series of computed volumes from rockfall sources using power-law regression on each magnitude-frequency distribution. The magnitude-frequency representation is used here to To illustrate the output results of the presented procedure, and particularly the computed rockfall volumes, we used the classic rockfall magnitude-frequency representa-tion [22,31,[33][34][35][36][37]. According to [37], volumes from rockfall source areas are assumed to follow a power-law regression: ...
The use of 3D point clouds to improve the understanding of natural phenomena is currently applied in natural hazard investigations, including the quantification of rockfall activity. However, 3D point cloud treatment is typically accomplished using nondedicated (and not optimal) software. To fill this gap, we present an open-source, specific rockfall package in an object-oriented toolbox developed in the MATLAB® environment. The proposed package offers a complete and semiautomatic 3D solution that spans from extraction to identification and volume estimations of rockfall sources using state-of-the-art methods and newly implemented algorithms. To illustrate the capabilities of this package, we acquired a series of high-quality point clouds in a pilot study area referred to as the La Cornalle cliff (West Switzerland), obtained robust volume estimations at different volumetric scales, and derived rockfall magnitude–frequency distributions, which assisted in the assessment of rockfall activity and long-term erosion rates. An outcome of the case study shows the influence of the volume computation on the magnitude–frequency distribution and ensuing erosion process interpretation.
... In some cases, when the structures are easy to recognize, such as joint sets that delineate block shapes well, it may be possible to extrapolate the magnitude frequency of the Fig. 18 a Example of rockfall source detection in the Mont Saint-Eynard cliff, comparing August 2009 and November 2012 terrestrial laser scanner data. b Power law deduced from 344 scars > 0.05 m 3 (modified after Guerin et al. 2014) sources based on the basal sliding surfaces and the heights of the scars (Santana et al. 2012). This permitted a Monte Carlo simulation to deduce a power law for the volumes of the source areas. ...
The estimation of rockfall hazards is usually based only on hazards related to rockfall propagation. The rockfall failure hazard is not currently well defined, and only a few studies have truly addressed this topic. The basics of slope stability assessment are reviewed. Here, we propose a summary of the standard methods used to assess susceptibility to rock mass failure, mainly based on techniques from the mining industry or tunneling. Most of them are qualitative. Many susceptibility scales have been described. Due to computer power and the high-resolution topography in real 3D, topography analysis and standard kinematic tests have been adapted and improved to obtain rockfall susceptibility. Hazard assessments based on the power law are one of the best and only ways to obtain a real assessment of rockfall hazard failure; however, they present some drawbacks that must be solved. The most promising avenues of research for rockfall failure hazards are linked to rock mass strength degradation, which is currently observed using high-resolution 3D monitoring of cyclic deformations with hysteresis. These are the resulting movements caused by groundwater circulations, thermal cycles, earthquakes, rainfall, etc. In conclusion, the rockfall hazard will be improved by better understanding these processes in addition to the chemical weathering effect.
... However, in some areas, only one acquisition of the 3D topography exists. In some cases, when the structures are easy to recognize, such as joint sets that delineate block shapes well, it may be possible to extrapolate the magnitude frequency of the Guerin et al. 2014) sources based on the basal sliding surfaces and the heights of the scars (Santana et al. 2012). This permitted a Monte Carlo simulation to deduce a power law for the volumes of the source areas. ...
We describe in detail seabed features on a deep-sea terrace of the Japan Trench caused by the 2011 Tohoku Earthquake based on visual seafloor observations. Data of this study was acquired using towed camera surveys and a remotely operated vehicle (ROV) dive in water depths between about 1300 and 2300 m and was conducted three, six and twelve months after the 2011. Damaged benthic organisms and disseminated bio-fragments might record the flow directions of the seismically or tsunami induced turbidity current. These records would be preserved into the geological record, if they remain undisturbed and getting buried before being reworked.
... Public Health 2020, 17, 8620 6 of 18 on the movement of sliding mass and its impact on the engineering structures. Table 1 illustrates the parameter setting according to the reference [27,28]; Case A had the smallest block size in the sliding mass (mean block size = 0.54 m 3 ), followed by Case B, and then Case C. We defined mechanical parameters for the sliding mass in the model according to Table 2 [26,29] and concurrently incorporated self-load into the model. After necessary boundary conditions had been determined, iterative calculation was conducted until a balance was reached. ...
The mechanism of natural-hazard-triggered technological (Na-tech) cascading disasters is complex, and the extent to which their damage is aggravated by various secondary events is difficult to quantify. This study selected a large oil depot and constructed a full-scale three-dimensional scene model based on the surrounding geographical environment. The discrete element method (DEM), finite element method (FEM) and finite volume method (FVM) were employed to conduct numerical simulations of the process and consequences of the following Na-tech disasters: heavy-rainfall-induced landslide → blocks impacting an oil transportation pipeline and breaking it → oil leaking, spreading and resulting in a vapor cloud explosion. According to the results, the maximum impact of the 1 m3 of sliding mass formed in the landslide on the pipeline was over 7 MN (meganewton), and the pipeline fractured completely when it was loaded with a contact force of only 1.44 MN. The numerical simulation methods revealed the mechanism of Na-tech cascading disasters in a large oil depot and quantified the consequences of each event in the cascading disasters.
... A common application of TLSs for rock fall monitoring includes the analysis of magnitude-frequency (MF) characterization of fragmental rock falls. Indeed, several authors have observed a scale-invariant pattern in an MF dimension under log-log scaleAbellán et al. 2009;Dewez et al. 2009;Lim et al. 2010;Santana et al. 2012) (Figure 17.6), suggesting that a self-organized criticality Discontinuity mapping on a terrestrial LiDAR point cloud, rendered using greyscale intensity values.(From Sturzenegger, M., and Stead, D., Nat. ...
... Files provided by TLS are high-density point-clouds, which is to say, matrices that comprise the coordinates of each scanned point (referred to the optic axis of the device), relative intensity, and three more columns which correspond to the red-green-blue (RGB) variables that define the color if the internal camera of the device is enabled while scanning. This technology has been proposed or evaluated for different applications, such as geotechnical studies [5][6][7][8], evaluation of coastal geodynamics [9] or geological risks [10], pathological analyses of structures [11], urban management [12], and construction control [13]. Its use has also been proposed for zoological analysis of cavernicolous fauna [14], forestry evaluations [15,16], and agriculture [17]. ...
Three-dimensional surveying with a terrestrial laser scanner (TLS) has implied a revolution in the field of 3D modeling, as this methodology provides detailed point-clouds with simplified processes of capture. In addition to the point-clouds, other outputs can be obtained, such as ortho-images, virtual itineraries, 2D cartography, and meshes, which implies a second avenue of multimedia products, such as 3D Portable Document Format (PDF) files and interactive applications. All these options are interesting for the management and broadcast of cultural heritage. The works that have been developed in this research are aimed at setting a workflow for the TLS surveying works and subsequent data management for the generation of a 3D model of the Caliphal Gate of Ceuta, which is considered as one of the most important medieval findings in Spain in recent years, and its immediate surroundings. This model and the different outputs that have been obtained from it allow for the continuation of the historiographic analysis of the complex, while documenting a partial stage in the development of the works of enhancement. In addition to this, these products are not only useful in terms of conservation studies or enhancement, as they are also suitable for the dissemination of the site. Special attention has been set on the paid suitable software for data management while generating the outputs, and for its application by the final users.
... Rockfall volumes across the four sites range from 0.001 m 3 to 702 m 3 (the largest rockfall is observed at Boulby) and the non-cumulative volumefrequency distribution fits a power law according to Equation 1 and Table 1. The β values of the power law fits are comparable to rockfall volume distributions from a variety of settings, which range from -0.4 to -1.07, as presented in Santana et al. (2012). The mean rockfall volume across all sites is 0.06 m 3 (Table 1). ...
Rock cliffs have been observed to evolve via progressive failure, yet the processes that control progressive failure and how it is spatially manifest are poorly understood. This paper presents the rationale for quantitatively assessing the spatial and temporal patterns of rockfalls as a tool for understanding how rock cliffs evolve via progressive failure. In order to do so, this paper considers the spatial and temporal distribution of rockfalls from high-resolution field monitoring data of hard rock coastal cliffs, and identifies patterns that appear to characterize rockfall evolution. Terrestrial laser scans of coastal cliffs in North Yorkshire (UK) were collected monthly over two years. Results show observations of the rockfalls that are indicative of progressive failure, as the propagation of small rockfalls appears to be the mechanism dominating the rate of material loss from these cliffs. Case studies of rockfall development demonstrate how rockfalls appear in sequence across the cliff face through time, and propagate across both geological and environmental zone boundaries. Combined with temporal patterns in erosion, the spatial patterns realized illustrate that variability in rockfall occurrence exists beyond what can be explained solely by geological and environmental variability. Analysis of the dataset presented may also provide context and information to inform the development of an approach to 3D numerical rock cliff modelling that is capable of simulating rockfall evolution in the manner observed here.
... Such data require methods that are able to retain the 3D character of the data while also being able to measure rockfall volumes that can span over six orders of magnitude, and over spatial extents that can exceed~10 6 m 2 . These settings could include, but are not limited to, a length of coastline (for example, Teixeira, 2006;Rosser et al., 2007;Marques, 2008;Lim et al., 2010;Young et al., 2011;Barlow et al., 2012;Rohmer and Dewez, 2013;Kuhn and Prüfer, 2014;Williams et al., 2018Williams et al., , 2019, cut slopes along a transport corridor (for example, Bunce et al., 1997;Hungr et al., 1999;van Veen et al., 2017), or on montane, alpine or arctic rock walls (for example, Dussauge-Peisser et al., 2002;Malamud et al., 2004;Santana et al., 2012;Messenzehl and Dikau, 2017). Without data obtained at these scales, it remains difficult to assess whether rockfalls are truly scale invariant across all the possible volumes of a given distribution, to put limits on modelled power laws of rockfall magnitude and frequency, and therefore to test whether rockfalls can be considered stochastic phenomena. ...
High‐resolution rockfall inventories captured at a regional scale are scarce. This is partly owing to difficulties in measuring the range of possible rockfall volumes with sufficient accuracy and completeness, and at a scale exceeding the influence of localised controls. This paucity of data restricts our ability to abstract patterns of erosion, identify long‐term changes in behaviour and assess how rockfalls respond to changes in rock mass structural and environmental conditions. We have addressed this by developing a workflow that is tailored to monitoring rockfalls and the resulting cliff retreat continuously (in space), in 3D and over large spatial scales (> 104 m). We tested our approach by analysing rockfall activity along 20.5 km of coastal cliffs in North Yorkshire (UK), in what we understand to be the first multi‐temporal detection of rockfalls at a regional scale. We show that rockfall magnitude‐frequency relationships, which often underpin predictive models of erosion, are highly sensitive to the spatial extent of monitoring. Variations in rockfall shape with volume also imply a systemic shift in the underlying mechanisms of detachment with scale, leading us to question the validity of applying a single probabilistic model to the full range of rockfalls observed here. Finally, our data emphasise the importance of cliff retreat as an episodic process. Going forwards, there will a pressing need to understand and model the erosional response of such coastlines to rising global sea levels as well as projected changes to winds, tides, wave climates, precipitation and storm events. The methodologies and data presented here are fundamental to achieving this, marking a step‐change in our ability to understand the competing effects of different processes in determining the magnitude and frequency of rockfall activity and ultimately meaning that we are better placed to investigate relationships between process and form/erosion at critical, regional scales.
... The assessment of the consequences of a rockfall impact on the building uphill facade required some preliminary data: the definition of the expected block volume, trajectories and kinetic energies at the building location. In particular, the block volume can be deduced referring to specific traditional geomechanical studies of the joints surveyed on the rock faces (Palmstrom 2005) or to topographical techniques such as LIDAR and Laser Scanner (Ferrero et al. 2011;Santana et al. 2012). Otherwise, a frequency law can be used (Ruiz-Carulla et al. 2015;Dussauge et al. 2003), relating the expected design volume with its temporal occurrence, in order to evaluate the physical vulnerability and the consequent risk on the building over a given period of time (De Biagi et al. 2017b;. ...
This paper proposes a quantitative method to assess the physical vulnerability of masonry buildings subjected to rockfalls. The impact of a boulder either results in no damage or in a local damage. Depending on the impact energy and the geometrical disposition of the structural and non-structural elements of the building, the local damage can further propagate across the structure, implying a (partial or global) collapse. Three mechanisms of local failure for the masonry walls are considered: punching, arching and vertical bending. For each of them, the method allows to evaluate the equivalent horizontal force exerted on the wall. The most likely local failure mode is then identified considering a full plastic impact model. For sake of simplicity, the damage propagation is geometrically treated with some further information about the arrangement and the typology of the structural elements. Some practical recommendations for on-site surveying concerning building heritage are also given in the text. Finally, the proposed approach is applied to a real case study in order to test its applicability.
... As recognized in several geological settings, the cumulative frequency of mass wasting areas or volumes is approximated by a power law scaling (Pelletier et al. 1997;Hungr et al. 1999;Santana et al. 2012). Specifically, the empirical distributions of landslide volumes described in the literature obey almost invariably a negative power law that may vary according to landslide types, local morphology and lithological conditions, as well as on the methods of data acquisition and the different approaches to estimate the failures distribution (Brunetti et al. 2009). ...
Landslides and surface erosion are major processes controlling the progressive recession of many rocky cliffs along the Italian coastline. Nevertheless, many coastal settlements were built along cliffed sectors prone to rapid collapses. This represents a serious risk for tourists and living people, as well as for buildings, roads and railway networks. The densely urbanized coastline of the Campi Flegrei active volcanic district is one of the rocky coastal areas of South Italy mostly exposed to the recession. Here, coastal cliffs are made by volcaniclastic deposits and include remnants of ancient volcanic edifices formed in the last 15 ka. Due to petrographic, geotechnical and geostructural properties of volcaniclastic deposits, these cliffs have been affected by rapid recession since their origin. This research focuses on a cliff of the Campi Flegrei coastaline (Torrefumo, Monte di Procida) which, although currently protected from the sea waves by a seawall, is still retreating. We assessed the ongoing recession using a change detection analysis, based on accurate topographic data acquired with two terrestrial laser scanning surveys executed in 2013 and 2016. The quantitative comparison of 3D point clouds datasets allowed detecting 191 cliff failures. We verified that the frequency-magnitude distribution of the detached blocks followed an inverse power law, and most of the involved volumes were between 0.01 and 1 m3. Retreat rates of different cliff sectors varied from 0.001 to 0.025 m/year. Our analysis also allowed us to recognize slope failure mechanisms and distinguish rock falls from grain-by-grain surficial erosion.
... Rockfall data sets derived from direct measurements (e.g., terrestrial laser scans [TLS] and photogrammetry) cover time scales from hours to years and are often used in modeling rock-wall retreat rates based on rockfall frequency-magnitude distributions over decadal to centennial time scales (Dussauge et al., 2003;Rosser et al., 2005;Barlow et al., 2012;Santana et al., 2012). In contrast, indirect measurements based on volumetric calculation of talus deposits have been used to estimate rock-wall retreat rates over millennial time scales (Curry and Morris, 2004;Sass and Krautblatter, 2007;Siewert et al., 2012). ...
This study addresses the temporal variations in rockfall activity in the 5.2 km2 calcareous cliffs of the deglaciated Lauterbrunnen Valley, Switzerland. We did this using 19 campaigns of repeated terrestrial laser scans (TLS) over 5.2 yr, power-law predicted behavior from extrapolation of the TLS-derived frequency-magnitude relationship, and estimates of long-time- scale (~11 k.y.) activity based on the volume of preserved postglacial rockfall talus. Results from the short-time-scale observations indicate no statistically significant difference between TLS observations averaging over 1.5 versus 5.2 yr. Rock-wall retreat rates in both cases are 0.03–0.08 mm/yr. In contrast, the power-law predicted rock-wall retreat rates are 0.14–0.22 mm/yr, and long-term rates from talus volumes are 0.27–0.38 mm/yr. These results suggest (1) short (1.5 yr) TLS inventories of rockfalls provide (within uncertainties) similar frequency-magnitude relationships as longer (5.2 yr) inventories, thereby suggesting short observation periods may be sufficient for hazard characterization from TLS, and (2) higher rock-wall retreat rates over long time scales (Holocene averaged) may reflect debuttressing and stress relaxation effects after glacial retreat, and/or enhanced rockfall activity under periglacial (climatic) conditions.
... Remote sensing techniques, such as terrestrial laser scanning (TLS), have been used to characterize and monitor rockfall hazards Jaboyedoff et al., 2012;2746 D. A. Bonneau et al.: Three-dimensional rockfall shape back analysis: methods and implications Telling et al., 2017). Single epoch TLS scans can be used for structural characterization of discontinuity orientations (Lato et al., 2009), the determination of the size and spatial distribution of potentially unstable rock mass volumes (Sturzenegger et al., 2011), and the back calculation of rockfall volumes based on discontinuity orientations of identified rockfall scars (Santana et al., 2012). Work by Lato et al. (2012), demonstrates how TLS can be integrated into rockfall hazard assessments along road cuts. ...
Rockfall is a complex natural process that can present risks to
the effective operation of infrastructure in mountainous terrain. Remote
sensing tools and techniques are rapidly becoming the state of the practice in
the characterization, monitoring and management of these geohazards. The aim
of this study is to address the methods and implications of how the
dimensions of three-dimensional rockfall objects, derived from sequential
terrestrial laser scans (TLSs), are measured. Previous approaches are
reviewed, and two new methods are introduced in an attempt to standardize
the process. The approaches are applied to a set of synthetic rockfall
objects generated in the open-source software package Blender. Fifty
rockfall events derived from sequential TLS monitoring in the White Canyon,
British Columbia, Canada, are used to demonstrate the application of the
proposed algorithms. This study illustrates that the method used to
calculate the rockfall dimensions has a significant impact on how the shape
of a rockfall object is classified. This has implications for rockfall
modelling as the block shape is known to influence rockfall runout.
... Some directions of recent research have included the use of Light Detection And Ranging (LiDAR) and photogrammetric techniques to derive rockfall frequency-magnitude relationships (Guerin et al., 2013;Lato et al., 2015;Janeras et al., 2017;van Veen et al., 2017;Williams et al., 2018;Matsuoka, 2019;Gilham et al., 2019) and anticipate rockfalls by means of detecting precursor events (Royán et al., 2014;Kromer et al., 2015). Other emerging applications include automatic discontinuity set extraction (Santana et al., 2012;Ge et al., 2018;Zhang et al., 2018;Li et al., 2019) and semi-automated characterization of failure modes (Matasci et al., 2018). These recent advances have the potential to provide actionable information to managers of infrastructure, such as highways, rail networks, and pipelines (Kromer et al., 2018). ...
High-resolution remote monitoring of slopes using terrestrial LiDAR and photogrammetry is a valuable tool for the management of civil and mining geotechnical asset hazards, but accurately classifying regions of interest in the data is sometimes a difficult and time-consuming task. Filtering unwanted areas of a point cloud, such as vegetation and talus, is often a necessary step before rockfall change detection results can be further processed into actionable information. In addition, long-term monitoring through seasonal vegetation changes and snow presents unique challenges to the goal of accurate classification in an automated workflow. This study presents a Random Forest machine learning approach to improve the classification accuracy and efficiency of terrestrial LiDAR monitoring of complex natural slopes. The algorithm classifies points as vegetation, talus, snow, and bedrock using multi-scale neighborhood geometry, slope, change, and intensity features. The classifier was trained on two manually labeled scans from summer and winter, then tested on three other unseen times. We find that F Score generally remains above 0.9 for talus and vegetation, and above 0.95 for bedrock and snow, indicating very high accuracy and an ability to adapt to changing seasonal conditions. In comparing this approach to CANUPO, an existing classification tool, we find our approach to be generally more accurate and flexible, at the expense of increased complexity and computation time. Comparisons with manual masking and a hybrid approach indicate that a machine learning solution is useful primarily in cases of rapidly changing rock slopes or in climates with significant seasonal variability and snow.
... The volume-frequency distribution ( Figure 5) adheres to the power-law scaling more widely observed in natural and geomorphic phenomena (Malamud et al., 2004). Whilst the scale of investigation is at least five-orders of magnitude smaller than commonly considered, the exponent β falls within that previously documented β = 0.4-1.1 for rockfall generally (Santana et al., 2012), and β = 0.71-2.37 for rockfall for the nearby coastal cliffs formed in the same rock types (Rosser et al., 2007;Barlow et al., 2012;Whadcoat, 2017;Williams et al., 2018). Hungr et al. (1999) identified that high β-values are more common for discontinuous as compared to massive rock masses. ...
Shore platforms control wave energy transformation which, in turn, controls energy delivery to the cliff toe and nearshore sediment transport. Insight into shore platform erosion rates has conventionally been constrained at mm‐scales using micro‐erosion metres, and at m‐scales using cartographic data. On apparently slowly eroding coasts, such approaches are fundamentally reliant upon long‐term observation to capture emergent erosion patterns. Where in practise timescales are short, and where change is either below the resolution or saturates the mode of measurement, the collection of data that enables the identification of the actual mechanisms of erosion is hindered. We developed a method to monitor shore platform erosion at millimetre resolution within metre‐scale monitoring plots using Structure‐from‐Motion photogrammetry. We conducted monthly surveys at 15 0.25 m2 sites distributed across the Hartle Loup platform in North Yorkshire, UK, over one year. We derived topographic data at 0.001 m resolution, retaining a vertical precision of change detection of 0.001 m. We captured a mean erosion rate of 0.528 mm yr‐1, but this varied considerably both across the platform and through the year. We characterised the volume and shape of eroded material. The detachment volume‐frequency and shape distributions suggest that erosion happens primarily via removal of shale platelets. We identify that the at‐a‐point erosion rate can be predicted by the distance from the cliff and the tidal level, whereby erosion rates are higher closer to the cliff and at locations of higher tidal duration. The size of individual detachments is controlled by local micro‐topography and rock structure, whereby larger detachments are observed on more rough sections of the platform. Faster erosion rates and larger detachments occur in summer months, rather than in more energetic winter conditions. These results have the potential to form the basis of improved models of how platforms erode over both short‐ and long‐timescales.
... Molti sono stati molti gli autori che hanno studiato e utilizzato queste tecniche in ambito geotecnico e nel contesto di stabilità in roccia. Tra questi si ricorda lo studio di Salvini et al. (2013) e lo studio di Santana et al. (2012). Si specifica innanzi tutto che i passaggi effettuati descritti di seguito sono stati eseguiti allo stesso modo sia per la nuvola ottenuta con fotogrammetria terrestre che per la nuvola ottenuta con i fotogrammi acquisiti dal drone. ...
Il rischio idrogeologico in Italia è diffuso in modo capillare. Diversi sono i fattori naturali che predispongono il nostro territorio a crolli in roccia, frane e alluvioni. La prima causa è senza dubbio la conformazione geologica e geomorfologica, caratterizzata da un'orografia giovane, quale quella alpina, e da rilievi in via di sollevamento. Per questo motivo, le tematiche legate allo studio degli ammassi rocciosi sono da sempre di primaria importanza. I metodi tradizionali di rilievo di una parete in roccia, per l'analisi successiva di rischio crolli, prevedono l'azione di un geologo specializzato direttamente in quota. È chiaro come questa operazione non sia semplice e richieda molte competenze multidisciplinari. Con questa attività si è voluto studiare l'utilizzo di metodi geomatici per rilievi geotecnici, in particolare l'uso della fotogrammetria (aerea e terrestre) e del LiDAR (Light Detection and Ranging). La parete oggetto di studio, che si trova all'interno del parco archeologico di Baratti e Populonia, ricopre molta importanza dal punto di vista storico e culturale, essendo essa un'antica cava di epoca etrusca.
... With permission.)Lim et al. 2010;Santana et al. 2012) ...
... However, they are mostly based on short-term and incomplete data series (Hungr et al., 2008). Several studies indicate that the exponent of the power-law distribution only varies slightly for a certain type of hazard (Santana et al., 2012;Stark and Hovius, 2001;Turcotte and Malamud, 2004). The rate of activity (frequency of an event) may strongly vary between for example, regional or geological settings (Dussauge-Peisser et al., 2002;Straub and Schubert, 2008). ...
Since the late 1960s it became clear that a more sustainable protection of people and property from the negative impacts of natural hazards will require a more balanced use of structural and non-structural measures, such as land-use planning and ecosystem-based solutions for disaster risk reduction, also called Eco-DRR. The most prominent example of Eco-DRR in mountainous regions are forests that protect people, settlements and infrastructures against gravitational natural hazards such as avalanches, landslides and hazards related to mountain torrents. The goal of this paper is to provide an overview on the influence of forests on risks induced by natural hazards and the associated challenges and uncertainties concerning risk analysis. Approaches from natural hazard risk are presented, along with recent results from forest research, thereby offering new ways to integrate forests into risk analysis. We discuss the potential effects of forests on the three important hazard components of the risk concept, namely the onset probability, the propagation probability and the intensity, and propose a set of guiding principles for integrating forests into quantitative risk assessment (QRA) for natural hazards. Our focus thereby lies on snow avalanches, rockfalls, floods, landslides, and debris flows. This review shows that existing methods and models for assessing forest effects on natural hazards suffice for integrating forests into QRA. However, they are mostly limited to the stand- or slope-scale, and further efforts are therefore needed to upscale these approaches to a regional level, and account for uncertainties related to forest effects and natural dynamics. Such a dynamic, rather than a static assessment of risk will finally allow for planning and implementing intelligent combinations of Eco-DRR and technical protection measures.
... Terrestrial laser scanning (TLS) has become a useful tool for the assessment of rockfall hazard both at larger scales ) and in the lower volume range of 1-1000 m 3 Lim et al. 2005;Lato et al. 2009;Abellán et al. 2010;Santana et al. 2012;Guerin et al. 2014;Sturzenegger et al. 2014;van Veen et al. 2017) and has the potential to be used for the prediction of rockfall location (Abellán et al. 2010;Royán et al. 2013), potential volume and kinematics , and possible timing of failure (Royán et al. 2015). Repeat TLS monitoring allows for the identification and analysis of the pre-failure behavior of rock slopes such as pre-failure deformation (Abellán et al. 2009(Abellán et al. , 2010Royán et al. 2013Royán et al. , 2015Kromer et al. 2015bKromer et al. , 2017 and patterns of precursor rockfall (Rosser et al. 2007;Royán et al. 2015;Kromer et al. 2015b;Kromer et al. 2017). ...
Terrestrial laser scanning (TLS) monitoring has been used to estimate the location, volume, and kinematics of a variety of small magnitude rockfalls before failure (1-1000 m 3 range), and in some cases, potential failure time has been assessed through the application of inverse velocity methods. However, our current understanding of rock slope pre-failure behavior for this magnitude range and prediction ability is based on observations of a small number of failure case histories. In this study, a pre-failure deformation database was constructed for rockfall volumes exceeding 0.1 m 3 , observed over a 1252-day study interval at the Goldpan rock slope, British Co-lumbia, Canada, in order to better understand the pre-failure behavior of rock slopes and provide an empirical means of estimating temporal failure ranges. Repeated TLS datasets were acquired at an average scanning interval of 2-3 months. A total of 90 rockfall events were recorded at this site, during this time period, of which 64 (71%) exhibited measurable deformation prior to failure. Classification of rockfalls by volume suggests that a scale dependency may exist, as deformation was detected for a greater proportion of rockfalls > 5 m 3 (92%) than for smaller rockfalls in the range of 0.1-0.5 m 3 (61%). A lower rate of pre-failure deformation detection was also reported for pla-nar sliding failures as compared with wedge or toppling failures, suggesting that deformation was less easily detected for these failure types. This study proposes and implements a framework for rockfall assessment and forecasting that does not require continuous monitoring of deformation.
... Often, these technologies provide advantages over traditional methods of data collection when slopes are steep and inaccessible. Change detection performed between sequential LiDAR scans can be used to identify and characterize rockfall source zones and develop frequency-magnitude relationships for a slope (Rosser et al., 2005;Santana et al., 2012;D'Amato et al., 2013;Guerin et al., 2014;van Veen et al., 2017). These inventories can contain a greater level of detail for rockfalls in the smaller volume ranges relative to traditional field inspections performed from the base of the slope (Dussauge-Peisser et al., 2002); however, it is often difficult to determine the trajectory or ending point of each event, which is affected by the slope materials and geometry, and the characteristics of the failed block, including its lithology (Deere and Miller, 1966). ...
Remote sensing techniques can be used to gain a more detailed understanding of hazardous rock slopes along railway corridors that would otherwise be inaccessible. Multiple datasets can be used to identify changes over time and create an inventory of rockfall events including frequency-magnitude relationships for rockfalls sourced on the slope. This study presents a method for using the remotely sensed data to develop inputs to rockfall simulations, which can be used to determine the likelihood of a rockfall impacting the railway tracks given it’s source zone location and volume. The results of the simulations can be related to the rockfall inventory to develop modified frequency-magnitude curves presenting a more realistic estimate of the hazard. These methods were developed using the RockyFor3D software and LiDAR and photogrammetry data collected over several years at the White Canyon, British Columbia, Canada, where the CN Rail main line runs along the base of the slope. Rockfalls sourced closer to the tracks were more likely to be deposited on the track or in the ditch, and of these, rockfalls between 0.1 and 10 m3 were the most likely to be deposited. Smaller blocks did not travel far enough to reach the bottom of the slope and larger blocks were deposited past the tracks. Applying the results of the simulations to a database of over 2000 rockfall events, a modified frequency-magnitude can be created, allowing the frequency of rock falls deposited on the railway tracks or in ditches to be determined. Suggestions are made for future development of the methods including refinement of input parameters and extension to other modelling packages.
... This interruption may prevent the formation of large failures along the basal sliding surface. The analysis of the scar planes of Santana et al. (2012) has also permitted measuring the spacing of the involved discontinuity sets, as the perpendicular distances between successive planes . Using the same data, the visible length (along the dip) of the scar edges was also calculated, as the maximum edge distance along the dip of a plane (Table 3). ...
Rockfalls are very rapid and damaging slope instability processes that affect mountainous regions, coastal cliffs and slope cuts. This contribution focuses on fragmental rockfalls in which the moving particles, particularly the largest ones, propagate following independent paths with little interaction among them. The prediction of the occurrence and frequency of the rockfalls has benefited by the rapid development of the techniques for the detection and the remote acquisition of the rock mass surface features such as the 3D laser scanner and the digital photogrammetry. These techniques are also used to monitor the deformation experienced by the rock mass before failure. The quantitative analysis of the fragmental rockfalls is a useful approach to assess risk and for the design of both stabilization and protection measures. The analysis of rockfalls must consider not only the frequency and magnitude of the potential events but also the fragmentation of the detached rock mass. The latter is a crucial issue as it affects the number, size and the velocity of the individual rock blocks. Several case studies of the application of the remote acquisition techniques for determining the size and frequency of rockfall events and their fragmentation are presented. The extrapolation of the magnitude-frequency relationships is discussed as well as the role of the geological factors for constraining the size of the largest detachable mass from a cliff. Finally, the performance of a fractal fragmentation model for rockfalls is also discussed.
... Terrestrial Laser Scanning (TLS) can be used to identify rock fall events by comparing sequential scans and these methods can be used to identify rock fall source locations and calculate event volumes. These data can be used to develop the rock fall frequency-magnitude relationship for a slope as demonstrated by Rosser et al. (2005), Santana et al. (2012), D' Amato et al. (2013), and Guerin et al. (2014). Recent advances in processing techniques have allowed us to do this automatically (Tonini and Abellán, 2014), and these methods can be applied to develop a database of events for large slopes where manual identification is not possible due to a high frequency of events. ...
Railways in Western Canada traverse many hazardous slopes, which are the source of frequent rock fall events. An understanding of the rock fall frequency-magnitude relationship can be used in hazard analysis for these railway lines. The White Canyon is an active slope along a 2.2 km section of CN Rail track in British Columbia which is managed by rock protection sheds, ditches and warning fences. Due to the high frequency of activity throughout the slope, maintaining rock fall records with details on locations and volumes can be difficult using methods of track-level inspection or monitoring systems. Over the past five years we have collected Terrestrial Laser Scanning (TLS) data at the White Canyon as a part of the Canadian Railway Ground Hazard Research Program and recently have refined data collection and processing methods such that we have been able to identify thousands of rock falls on the slope in a two-year period, and calculate their volumes, using 3-dimensional change detection and an automated rock fall detection process. These refined methods have allowed us to develop a database containing a high level of detail, especially in the upper slopes. We have used these data to build an understanding of how the time elapsed between site visits for data collection can affect our ability to identify rock falls on the slope. The lessons learned through this process provide insight into the design of future terrestrial monitoring campaigns for this and other slopes.
Important infrastructure such as highways or railways traverse unstable terrain in many mountainous and scenic parts of the world. Rockfalls and landslides result in frequent maintenance needs, system unreliability due to frequent closures and restrictions, and safety hazards. Seismic activity significantly amplifies these negative economic and community impacts by generating large rockfalls and landslides as well as weakening the terrain. This paper interrogates a rich database of repeat terrestrial lidar scans collected during the Canterbury New Zealand Earthquake Sequence to document geomorphic processes as well as quantify rockfall activity rates through time. Changes in the activity rate (spatial distribution) and failure depths (size) were observed based on the Rockfall Activity Index (RAI) morphological classification. Forecasting models can be developed from these relationships that can be utilized by transportation agencies to estimate increased maintenance needs for debris removal to minimize road closures from rockfalls after seismic events.
Power laws fit to rockfall frequency-magnitude distributions are commonly used to summarize rockfall inventories, but uncertainty remains regarding which variables control the shape of the distribution, whether by exerting influence on rockfall activity itself or on our ability to measure rockfall activity. In addition, the current literature lacks concise summaries of background on the frequency-magnitude distribution for rockfalls and power law fitting. To help address these knowledge gaps, we present a new review of rockfall frequency literature designed to collect the basic concepts, methods, and applications of the rockfall frequency-magnitude curve in one place, followed by a meta-analysis of 46 rockfall inventories. We re-fit power laws to each inventory based on the maximum likelihood estimate of the scaling exponent and the cutoff volume and used Analysis of Variance and regression to test for relationships between 11 independent physical and systematic variables and the scaling exponent, applying both single-predictor and 2-predictor models. Notable relationships with the scaling exponent were observed for rockmass condition, geology, and maximum inventory volume. Higher scaling exponent values were associated with higher quality rockmasses, sedimentary rocks, and with smaller maximum rockfall volumes. Climate, data collection frequency, and data collection method also appear to have some influence on the scaling exponent, since higher scaling exponents were associated with temperate climates and inventories with shorter temporal extent and methods that involved few or no revisits to the slope. Relationships between the scaling exponent and slope angle, slope aspect, number of rockfalls in the inventory, record length, and minimum inventory volume are more ambiguous due to the noise inherent in comparing many studies together. In line with previous work, this study reinforces that sampling large volumes is important to obtaining an accurate distribution, and that the spatial scale of the inventory affects the likelihood of obtaining these measurements. We conclude with discussion of the results and recommendations for future work.
Rockfall causes a large number of accidents and fatalities in steep environments. A realistic quantification of rockfall risk is thus crucial for an effective prevention of damages and loss of lives. The estimation of rockfall and block volumes for different return periods thereby remains a major challenge. In this paper, we present a straightforward rockfall frequency model (RFM: Rockfall Frequency Model) and its application at 8 different sites at 7 locations in the Swiss Alps. The RFM assumes that the magnitude-frequency relationships of rockfall events and blocks follow a power law. The parameters of this distribution are estimated based on a simple classification of rock structures and on field inventories. Beside the block volume frequency, which is very sensitive to the consideration of large rockfall events, the frequency of rockfalls with at least one block with a minimum volume, is determined. The block size distributions measured in this study were well captured by power laws. The rockfall and block volumes calculated with the RFM were generally slightly higher than the scenarios of the official hazard assessments. The uncertainty analysis, however, revealed a high variability of the release scenarios with respect to the parameters of the RFM, increasing with the return period. Both, the rockfall volumes and the block volumes, are particularly sensitive to the estimated exponent of the power law distribution of the rockfall events. Nevertheless, the proposed RFM provides an objective and transparent approach to derive magnitude-frequency relationships of rockfall events and individual blocks even if historical inventories are missing or insufficient and is thus a promising alternative to merely expert-based approaches.
Rockfall causes a large number of accidents and fatalities in steep environments. A realistic quantification of rockfall risk is thus crucial for an effective prevention of damages and loss of lives. The estimation of rockfall and block volumes for different return periods thereby remains a major challenge. In this paper, we present a straightforward rockfall frequency model (RFM) and its application at 8 different sites at 7 locations in the Swiss Alps. The RFM assumes that the magnitude-frequency relationships of rockfall events and blocks follow a power law. The parameters of this distribution are estimated based on a simple classification of rock structures and on field inventories. Beside the block volume frequency, which is very sensitive to the consideration of large rockfall events, the frequency of rockfalls with at least one block with a minimum volume, is determined. The block size distributions measured in this study were well captured by power laws. The rockfall and block volumes calculated with the RFM were generally slightly higher than the scenarios of the official hazard assessments. The uncertainty analysis, however, revealed a high variability of the release scenarios with respect to the parameters of the RFM, increasing with the return period. Both, the rockfall volumes and the block volumes, are particularly sensitive to the estimated exponent of the power law distribution of the rockfall events. Nevertheless, the proposed RFM provides an objective and transparent approach to derive magnitude-frequency relationships of rockfall events and individual blocks even if historical inventories are missing or insufficient and is thus a promising alternative to merely expert-based approaches.
Rockfall is one of the most frequent and damaging types of mass movement, and in this chapter, we consider aspects of rockfall hazard and vulnerability that lead to risk. We focus on the current ability to assess rockfall risk, drawing on recent research utilising extensive inventories and datasets on rockfall occurrence and impact. We begin by considering two aspects of rockfall hazard: forecasting rockfall hazard from historical observations and investigating the uncertainties associated with the temporal resolution of rockfall observations. We then consider the exposure and vulnerability of property and people to rockfall hazards, which are key determinants of rockfall risk and loss. To illustrate this, we draw upon two case studies where unique data on rockfall occurrence and impact have been collated, providing insight into the hazard and risk that rockfalls pose. Our first is from coastal rock cliffs in North Yorkshire, United Kingdom, and our second is from rock slopes that experienced shaking in the 2011 Christchurch earthquakes, New Zealand. Many research studies of rockfall arise from a need to manage rockfall risks, providing a wealth of information on assessing and mitigating rockfall hazard, which we signpost throughout to supplement these case studies. The case studies show that (i) the temporal resolution of rockfall surveys tend to dominate our interpretation of rockfall frequency–magnitude distributions and hence hazard, whereas these should be based on survey resolutions and durations of sufficient temporal resolution and duration to capture all plausible event magnitudes and (ii) in general, rockfall risk analyses commonly adopt overly simplistic exposure and vulnerability assumptions, rather than more nuanced event tree approaches that link hazard intensity to determinants of exposure such as time of day, setting and cognitive awareness.
Here we study rocks falling from exposed outcrops of bedrock, which have left tracks on the slope over which they have bounced and/or rolled, in fresh impact craters (1–10 km in diameter) on Mars. The presence of these tracks shows that these rocks have fallen relatively recently because aeolian processes are known to infill topographic lows over time. Mapping of rockfall tracks indicate trends in frequency with orientation, which in turn depend on the latitudinal position of the crater. Craters in the equatorial belt (between 15°N and 15°S) exhibit higher frequencies of rockfall on their north-south oriented slopes compared to their east-west ones. Craters >15° N/S have notably higher frequencies on their equator-facing slopes as opposed to the other orientations. We computed solar radiation on the surface of crater slopes to compare insolation patterns with the spatial distribution of rockfalls, and found statistically significant correlations between maximum diurnal insolation and rockfall frequency. Our results indicate that solar-induced thermal stress plays a more important role under relatively recent climate conditions in rock breakdown and preconditioning slopes for rockfalls than phase transitions of H2O or CO2, at mid- and equatorial-latitudes. Thermal stress should thus be considered as an important factor in promoting mass-wasting process on impact crater walls and other steep slopes on Mars.
Data on large rockslides presented in a book by Olafur Jónsson (1976) are analyzed in terms of their magnitude and frequency in the Postglacial (10 000 a BP). Size has been examined by division into four groups, the modal size is from 1 to 10 × 106 m3. Age of rockslide events was assessed by relative methods by O. Johnsson and is thought to be internally consistent. Five age categories have been used and the modal group (III ≈ 3-5000 a BP) has 34% of rockslides. The period 3-7000 a BP contains 60% of all events; less than 5% have occurred in the last 1000 years. Age-size distributions suggest that the smallest slides are also the youngest; the largest events are the oldest. Problems associated with interpretation of the data are discussed in terms of a probability model but it is concluded that only a very simple interpretation is possible by its use. Climatic controls are not considered to be of prime importance in determining either size or age of slides. The majority of slides are found in lavas (Quaternary or Tertiary) and it is concluded that cleft water pressure (in some cases as a result of waning ice sheets) is the prime cause of slope failure.
This contribution describes a mobile mapping system based on 3D images and its applications for determining geometric rock mass parameters. The contact-free measurement system allows determining the spatial condition of rock mass discontinuities by taking measurements directly from 3D images. Two different imaging sources are used: a calibrated off-the- shelf camera for highly flexible application and a panoramic line-scanner for capturing large areas at high resolution by images up 100 megapixel. Both systems are used freely without requiring the determination of the imaging locations. Stereoscopic image pairs are acquired and processed to a 3D image by special purpose software. Drawbacks of conventional mapping are overcome by the contact-free measuring principle leading to increased working safety, improved data quality and reliability, and reduced acquisition costs.
A recent development in the use of lidar remote sensing techniques is ground-based laser scanning. Laser scanning of rock faces yields the spatial relation between all scanned rock surface points, at a very high resolution, basically a dense "point cloud" in three-dimensional space. The subject of this research is to obtain discontinuity information from the point cloud data set, using an approach that can be automated. The first step in this methodology is to interpolate the point cloud data using 3D Delaunay triangulation in order to create a 3D surface. As a 3D triangulated surface, the scanned rock face is represented by a large number of triangles. The orientation of each triangle can subsequently be computed using basic geometrical rules. Analysis of the kernel density stereo plots of the orientation of all triangles, reveal that specific discontinuity sets can be recognised. Obviously, if this approach can be further developed and fully automated, this would give the site engineer or geologist, in real-time, evidence on the internal structure of any discontinuous rock mass. Particularly in areas where access to rock outcrops is poor, application of this technique will be very promising.
This case study deals with a rock face monitoring in urban areas using a Terrestrial Laser Scanner. The pilot study area is an almost vertical, fifty meter high cliff, on top of which the village of Castellfollit de la Roca is located. Rockfall activity is currently causing a retreat of the rock face, which may endanger the houses located at its edge. TLS datasets consist of high density 3-D point clouds acquired from five stations, nine times in a time span of 22 months (from March 2006 to January 2008). The change detection, i.e. rockfalls, was performed through a sequential comparison of datasets. Two types of mass movement were detected in the monitoring period: (a) detachment of single basaltic columns, with magnitudes below 1.5 m3 and (b) detachment of groups of columns, with magnitudes of 1.5 to 150 m3. Furthermore, the historical record revealed (c) the occurrence of slab failures with magnitudes higher than 150 m3. Displacements of a likely slab failure were measured, suggesting an apparent stationary stage. Even failures are clearly episodic, our results, together with the study of the historical record, enabled us to estimate a mean detachment of material from 46 to 91.5 m3 year-1. The application of TLS considerably improved our understanding of rockfall phenomena in the study area.
The basal sliding surfaces in large rockslides are often composed of several surfaces and possess a complex geometry. The exact morphology and location in three dimensions of the sliding surface remains generally unknown, in spite of extensive field and subsurface investigations, such as those at the Åknes rockslide (western Norway). This knowledge is crucial for volume estimations, failure mechanisms, and numerical slope stability modeling. This paper focuses on the geomorphologic characterization of the basal sliding surface of a postglacial rockslide scar in the vicinity of Åknes. This scar displays a stepped basal sliding surface formed by dip slopes of the gneiss foliation linked together by steeply dipping fractures. A detailed characterization of the rockslide scar by means of high-resolution digital elevation models permits statistical parameters of dip angle, spacing, persistence, and roughness of foliation surfaces and step fractures to be obtained. The characteristics are used for stochastic simulations of stepped basal sliding surfaces at the Åknes rockslide. These findings are compared with previous models based on geophysical investigations. This study discusses the investigation of rockslide scars and rock outcrops for a better understanding of potential rockslides. This work identifies possible basal sliding surface locations, which is a valuable input for volume estimates, design and location of monitoring instrumentation, and numerical slope stability modeling.
The external and internal geometry of four turbidite systems out-cropping around the Buil syncline (Ainsa basin, Spanish Pyrenees) has been reconstructed with reservoir-scale resolution in three dimensions (3-D). The irregular geometry of the syncline and the resolution required for the reconstruction cannot be resolved with cross sections. Therefore, reconstruction has been carried out with a new methodology that applies a 3-D dip-domain geometrical model and 3-D restoration techniques to achieve reservoir-scale resolution in kilometric-scale reconstructions. This methodology is aimed at resolving 3-D geometries in folded areas and regions with variable thickness stratigraphy. The 3-D reconstruction of the Buil syncline reveals the synsedimentary growth of an intrabasinal anticline and the foreland lithospheric flexure associated with tectonic loading north of the Ainsa basin.
Landslides are a significant natural hazard in mountainous regions and are often triggered by external factors, such as earthquakes, rainfall, permafrost melting or retreat of glaciers. A large landslide occurred in the Swiss Alps on 13 July 2006, when portions of an immense rock spur on the eastern flank of the Eiger peak collapsed. Here we use field observations and terrestrial laser scanning data to record and quantify the relative motion along the various blocks of rock that form this spur. The data show that during the year of observation the blocks moved relative to one another by up to tens of metres along fractures that can be related to pre-existing planes of weakness. Rates of motion and deformation were high throughout July 2006, particularly in the northern part of the spur that partially collapsed on 13 July. The rates decreased considerably during the subsequent months, although a slight increase was noted in June and July 2007. These observations are consistent with instability of the spur initiated by subsidence of a single block at the rear, which acted as a wedge and disintegrated over time owing to loss of lateral confinement.
The orientation of a surface can be derived from the X, Y, Z position of three or more points lying on it. Two different methods are presented to obtain average surface orientations from points belonging to the surface. One consists of calculating a best-fit plane through a planar regression of data, which yields an average orientation for sets of more than three points. The second approach consists of analyzing the moment of inertia of the set of points to obtain the orientation of the best-fit plane and a measure of the spatial distribution of points. The quality of the orientation measurement depends strongly on the spatial distribution of points and can be evaluated with the use of eigenvalues.
We describe a 0.5 Mm3 rock avalanche that occurred in 2008 in the western Alps and discuss possible roles of controlling factors in the context of current climate change. The source is located between 2410m and 2653 m a.s.l. on Mont Crammont and is controlled by a densely fractured rock structure. The main part of the collapsed rock mass deposited at the foot of the rock wall. A smaller part travelled much farther, reaching horizontal and vertical travel distances of 3050 m and 1560 m, respectively. The mobility of the rock mass was enhanced by channelization and snow. The rock-avalanche volume was calculated by comparison of pre- and post-event DTMs, and geomechanical characterization of the detachment zone was extracted from LiDAR point cloud processing. Back analysis of the rock-avalanche runout suggests a two stage event.
There was no previous rock avalanche activity from the Mont Crammont ridge during the Holocene. The 2008 rock avalanche may have resulted from permafrost degradation in the steep rock wall, as suggested by seepage water in the scar after the collapse in spite of negative air temperatures, and modelling of rock temperatures that indicate warm permafrost (T > −2 ◦C).
Rock joints exhibit a wide spectrum of shear strength under the low effective normal stress levels operating in most rock engineering problems. This is due to the Strong influence of surface roughness and variable rock strength. Conversely, under the high effective normal stress levels of interest to tectonophysicists the shear strength spectrum of joints and artificial faults is narrow, despite the wide variation in the triaxial compression strength of rocks at fracture. In Part I of this review, empirical non-linear laws of friction and fracture are derived which explain this paradoxical behaviour and which can be used to predict or extrapolate shear strength data over the whole brittle range of behaviour.
This paper presents a short history of the appraisal of laser scanner technologies in geosciences used for imaging relief
by high-resolution digital elevation models (HRDEMs) or 3D models. A general overview of light detection and ranging (LIDAR)
techniques applied to landslides is given, followed by a review of different applications of LIDAR for landslide, rockfall
and debris-flow. These applications are classified as: (1) Detection and characterization of mass movements; (2) Hazard assessment
and susceptibility mapping; (3) Modelling; (4) Monitoring. This review emphasizes how LIDAR-derived HRDEMs can be used to
investigate any type of landslides. It is clear that such HRDEMs are not yet a common tool for landslides investigations,
but this technique has opened new domains of applications that still have to be developed.
KeywordsLandslide–LIDAR–Laser scanner–High-resolution DEM–Topography analysis–Structural analysis
Quantitative Risk Assessment (QRA) has become an indispensable tool for the management of landslide hazard and for planning
risk mitigation measures. In this paper we present the evaluation of the rockfall risk at the Solà d’Andorra slope (Andorra
Principality) before and after the implementation of risk mitigation works, in particular, the construction of protective
fences. To calculate the risk level we have (i) identified the potential rockfall release areas, (ii) obtained the volume
distribution of the falling rocks, (iii) determined the frequency of the rockfall events, and (iv) performed trajectographic
analysis with a 3D numerical model (Eurobloc) that has provided both the expected travel distances and the kinetic energy
of the blocks. The risk level at the developed area located at the foot of the rock cliff has been calculated taking into
account the nature of the exposed elements and their vulnerability. In the Forat Negre basin, the most dangerous basin of
the Solà d’Andorra, the construction of two lines of rockfall protection fences has reduced the annual probability of loss
of life for the most exposed person inside the buildings, from 3.8×10−4 to 9.1×10−7 and the societal risk from 1.5×10−2 of annual probability of loss of life to 1.2×10−5.
3D terrestrial laser scanning is a relatively new, but already revolutionary, surveying technique. The survey yield a digital data set, which is essentially a dense point cloud, where each point is represented by a coordinate in 3D space. The most important advantage of the method is that a very high point density can be achieved, in the order of 5 to 10 mm resolution. In order to analyse the character and shape of the scanned surfaces it is necessary to convert the irregularly distributed point data into 3D surface information using surface reconstruction. The reconstructed surface can subsequently be visualized using a variety of 3D visualization techniques. From the reconstructed 3D surfaces, it is also possible to generate 2D profiles or elevation contour lines for use in regular GIS or CAD packages. A number of applications are described in this paper, which may illustrate the possible benefits of using laser scanning as a technique in engineering geological practice and research: volume analysis and monitoring, detailed and large-scale topographic mapping, tunnelling, rock face surveying, and digital outcrop mapping.
Data on large rockslides presented in a book by Olafur Jónsson (1976) are analyzed in terms of their magnitude and frequency in the Postglacial (10 000 a BP). Size has been examined by division into four groups, the modal size is from 1 to 10 × 106 m³. Age of rockslide events was assessed by relative methods by O. Johnsson and is thought to be internally consistent. Five age categories have been used and the modal group (III ≈ 3–5000 a BP) has 34 % of rockslides. The period 3–7000 a BP contains 60% of all events; less than 5% have occurred in the last 1000 years. Age-size distributions suggest that the smallest slides are also the youngest; the largest events are the oldest. Problems associated with interpretation of the data are discussed in terms of a probability model but it is concluded that only a very simple interpretation is possible by its use. Climatic controls are not considered to be of prime importance in determining either size or age of slides. The majority of slides are found in lavas (Quaternary or Tertiary) and it is concluded that cleft water pressure (in some cases as a result of waning ice sheets) is the prime cause of slope failure.
The point cloud registration principle was discussed. Based on this principle, the error model of point cloud registration was deduced. From the model, the point error could be calculated, which is an index of point cloud registration. In order to evaluate the effect of scanning distance change of terrestrial laser scanner on point cloud registration error, an experiment program was designed to test precisely different distance in range accuracy of terrestrial laser scanner. According to bull's eye extracted and the error model of point cloud registration, point cloud registration precision of different distance was obtained, which led to the best accuracy of point cloud registration. The results show that this point cloud registration error model and the experimental method are excellent.
An investigation has been made by the UK Transport and Road Research Laboratory into the reproducibility of measurement of joint spacing and orientation in rock. Most of the data collected in two of the tunnel drives of the Kielder Aqueduct, which allowed the study to be undertaken in conditions similar to those occurring when logging for tunnel records. Three principal rock types (sandstone, mudstone and limestone) were logged, and for comparison purposes measurements on the same limestone formation were made in a nearby quarry. The article discusses the measurement program and its results.
This paper describes Post-Little ke Age rockfalls that affect the well-known west face of Les Drus (Mont-Blanc massif, France). The abundant iconography of the peak of Les Drus (3754 m a.s.l., 1000 in high) allows photo-comparison and interpretation of the rocky face. These are combined with historical descriptions of the rockfalls and ground-based LiDAR surveys, in order to characterize the rock face instability over the last 150 years. Eight rockfalls of variable magnitude occurred since 1905, totaling 335,000 ± 15,000 m3 of solid rock, involving a retrogressive erosion of the 500-m-high Bonatti Pillar. The magnitude and frequency of the rock falls have significantly increased since 1950, which led to the collapse of the entire pillar in June 2005 (excess volume of 250,000 m3). The contributions of seismicity, paraglacial control, and permafrost degradation to the rockfalls are discussed.
We study the problem of creating a complete model of a physical object. Although this may be possible using intensity images, we here use images which directly provide access to three dimensional information. The first problem that we need to solve is to find the transformation between the different views. Previous approaches either assume this transformation to be known (which is extremely difficult for a complete model), or compute it with feature matching (which is not accurate enough for integration). In this paper, we propose a new approach which works on range data directly, and registers successive views with enough overlapping area to get an accurate transformation between views. This is performed by minimizing a functional which does not require point-to-point matches. We give the details of the registration method and modelling procedure, and illustrate them on real range images of complex objects.
Power spectral analyses of soil moisture variability are carried out
from scales of 100 m to 10 km on the microwave remotely-sensed data from
the Washita experimental watershed during 1992. The power spectrum S(k)
has an approximately power-law dependence on wave number k with exponent
-1.8. This behavior is consistent with the behavior of a stochastic
differential equation for soil moisture at a point. This behavior has
important consequences for the frequency-size distribution of
landslides. We present the cumulative frequency-size distributions of
landslides induced by precipitation in Japan and Bolivia as well as
landslides triggered by the 1994 Northridge, California earthquake.
Large landslides in these regions, despite being triggered by different
mechanisms, have a cumulative frequency-size distribution with a
power-law dependence on area with an exponent ranging from -1.5 to -2.
We use a soil moisture field with the above statistics in conjunction
with a slope stability analysis to model the frequency-size distribution
of landslides. In our model landslides occur when a threshold shear
stress dependent on cohesion, pore pressure, internal friction and slope
angle is exceeded. This implies a threshold dependence on soil moisture
and slope angle since these factors are primarily dependent on soil
moisture. Abstract continued in paper.
Japan Astrometry Satellite Mission for INfrared Exploration JASMINE
project stands at the stage where its basic design will be determined in
a few years Then it is very important to simulate the data stream
generated by astrometric fields at JASMINE in order to support
investigations of error budgets sampling strategy data compression data
analysis scientific performances etc We construct a simulation system
that should include all objects in JASMINE such as observation
techniques models of instruments and bus design orbit data transfer data
analysis etc in order to resolve all issues which can be expected
beforehand and make it easy to cope with some unexpected problems which
might occurre during the mission of JASMINE For position reconstruction
we are required to determine positions of stars and instrument attitudes
simultaneously For doing this overwrapping focal plane images with high
accuracy is needed We use statistical method which is used in Support
Vector Machine for optimizing observation programm For getting high
accuracy observations we also required to detect attitude error from
mission data Principal Component Analysis is effective for this perpose
In this poster presentation we explain topics on the data analysis and
system simulation for JASMINE project