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Several examples in western Europe have shown that, at least for deep-seated rotational slides, reactivation of formerly slipped masses is a more frequent phenomenon than the occurrence of new landslides, therefore representing a higher hazard. We selected a study area comprised of 13 landslides located in the Flemish Ardennes (West Belgium) and pr...
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... study area belongs to the so-called Flemish Ardennes, a region extending over ∼430 km 2 in western Belgium and affected by 135 big deep-seated past landslides ( Fig. 1) (Ost et al., 2003, Van Den Eeckhaut et al., 2005). In the absence of any dating, Van Den Eeckhaut et al. (2005) assume that, because no recent written document describing the initiation of one of these large landslides has been found, they are at least 100 years old. Moreover, the study of similar ancient landslides located in eastern ...
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... Recurrence may be local, involving only a limited part of the slope, or it may be total, involving the entire ancient landslide body (Ronchetti et al. 2010). This uncertain and unstable condition indicates an increased risk of recurrence (Dewitte et al. 2006). Some large ancient landslides can even reoccur because of different triggering factors. ...
Recurrence of large-scale ancient landslides often manifests as catastrophic events, so it is important to assess their stability by monitoring the deformation process. In this study, the Da’ao ancient landslide along the Jinsha River in China was investigated and analyzed. Field investigation showed that the landslide body is being experienced deforming with many new failures. Three sliding events can be identified according to different main scarps. The Permanent Scatterer Synthetic Aperture Radar Interferometry (PS-InSAR) data further revealed that the most obvious deforming area is in the middle and toe part of the sliding body with the largest cumulative displacement of 55 mm during 2017 to 2021. Additionally, the relatively stable zone and the accelerating deforming zone are divided by displacement rate. This indicates that the Da’ao landslide is becoming unstable. At the same time, the Particle Flow Code (PFC) simulation verified that the risk of landslide recurrence is likely when subjected to strong earthquakes or heavy rainfall, and the resulting sidings could dam the Jinsha River. In addition, the analysis results suggested that the displacement rates were approximately 5 mm/year and 13.3 mm/year before and after the Ms 5.2 earthquake, respectively, which occurred on 04/21/2019. The deformation changed with seasonal variation during 2017–2021 and lagged behind precipitation, while the earthquake can increase the amount and rate of displacement. The results presented here can help us to understand how landslides recur over time and their deformation and failure mechanisms, which is useful for disaster prevention and mitigation.
... The horizontal displacement monitoring data of each inclinometer in April 2013 and April 2014 were used as the initial and final values, respectively, to plot the cumulative displacement-depth curve of each borehole in the same profile, and the cumulative displacement-depth curve plot of profile 1-1 (Fig. 20) [37]. Despite the observation of a stable deformation slope rate and a uniform anti-sliding pile force after the initial ZAL treatment, the grade-II landslide continuously crept and created new shear-out surfaces under rainfall. ...
... The literature suggests that the use of landslide release locations as input training samples is a common practice in the field (e.g., Clerici et al., 2006;Poli and Sterlacchini, 2007;Bednarik et al., 2010;Dewitte et al., 2006Dewitte et al., , 2010Petschko et al., 2014;Heckmann et al., 2014;Havenith et al., 2015;Steger et al., 2017;Capitani et al., 2018;Dou et al., 2021, among others). Even though such a procedure may produce very useful results in a specific context, challenges may arise as soon as non-modelers and decision makers interpret the resulting maps that are entitled to represent "landslide susceptibility". ...
... Dendrogeomorphic methods are very often applied on complex landslides with more or less heterogeneous morphology. It is well known that such landslides behave in the form of reactivation of only spatially limited zones (Dewitte et al., 2006). This behaviour is often visible even from the results of tree-ring-based reconstruction of past landslide activity using event-response maps, e.g., Fantucci and Sorriso-Valvo (1999), Š ilhán et al. (2013), and Stefanini (2004. ...
The result of tree-ring-based reconstruction of past landslide events is often the development of a single total chronology. This approach can be very effective for small homogeneous landslides. However, compiling chronological data from heterogeneous (often independent) zones of large complex landslide areas into one chronology can induce over- or underestimation of some events, resulting in lowered reliability of the reconstruction. The solution for elimination of this effect can lie in the diversification of complex landslide areas into homogeneous zones with separate analyses. The aim of this study was to quantify the effect of this separation on detected slope movement events and to define parameters whose investigation could distinguish events (sliding) from noise (creeping).
For this purpose, 412 tree-ring series from 206 disturbed common spruce (Picea abies (L.) Karst.) occupying complex landslide areas were dendrogeomorphically analysed. The landslide area was divided into five homogeneous zones using geomorphic mapping, LiDAR-based DEM and geophysical sounding (ERT). Five events (verified in individual zones) were detected in the total chronology. Two extra events in the total chronology (28.6%) were considered noise. Moreover, two zonal events were detected but not recorded in the total chronology. This indicates that the noise in the total chronology of the complex landslide area could reach more than a quarter of dated events. Next, true slide events and noise (caused by creep) were differentiated in the structure of growth disturbances (reaction wood vs. abrupt growth suppression) and their proportion in event reconstruction, spatial patterns of trees containing slope movement signals, and the character of triggers. Thus, for better filtering of noise from signals in tree-ring-based chronologies of landslides, not only observations of dendrogeomorphic index values but also the morphology of landslides and characteristics of dated processes must be considered.
... Edelman [21] reported such cities to face more immediate problems than those in the developed world and have fewer resources to deal with them. Open Access Library Journal It is not for nothing that Dewitte et al. [22] consider it to be one of the factors of susceptibility to ground movement in the sense that it can act on reactivation by influencing the physical properties of the slope. The different orientation of the slopes leads to different exposure to solar radiation and atmospheric precipitation. ...
... Hazard assessments have focused on documenting spatial distribution and causal factors of landslides as well as to localize prone slope instability sites (Dai et al. 2002;Fell et al. 2008). Landslide hazard mapping has been enhanced by analysis and data processing of causative factors as thematic layers on GIS platforms and using remote sensing data, depicting a final zonation with different levels of susceptibility or hazard (Carrara et al. 1999;Jibson et al. 2000;Dewitte et al. 2006;Legorreta Paulín et al. 2010;Muñiz-Jauregui and Hernández-Madrigal 2012;Shahabi and Hashim 2015;Murillo-García et al. 2019;Salinas-Jasso et al. 2019b). Some attempts have been made to predict a likely reactivation of ancient landslides (Dewitte et al. 2006;Van Den Eeckhaut et al. 2007;Massey et al. 2013;Villaseñor-Reyes et al. 2018), which may involve high levels of economic loss and catastrophic consequences by the uncertainty related with their origin and behavior (Mansour et al. 2011;Palmer 2017). ...
... Landslide hazard mapping has been enhanced by analysis and data processing of causative factors as thematic layers on GIS platforms and using remote sensing data, depicting a final zonation with different levels of susceptibility or hazard (Carrara et al. 1999;Jibson et al. 2000;Dewitte et al. 2006;Legorreta Paulín et al. 2010;Muñiz-Jauregui and Hernández-Madrigal 2012;Shahabi and Hashim 2015;Murillo-García et al. 2019;Salinas-Jasso et al. 2019b). Some attempts have been made to predict a likely reactivation of ancient landslides (Dewitte et al. 2006;Van Den Eeckhaut et al. 2007;Massey et al. 2013;Villaseñor-Reyes et al. 2018), which may involve high levels of economic loss and catastrophic consequences by the uncertainty related with their origin and behavior (Mansour et al. 2011;Palmer 2017). The analysis of unexpected movement reactivations in old mass bodies still being complicated, especially when instability patterns and displacement rates are unknown and emergency plans are not prepared to deal with the problem. ...
We have evaluated slope stability conditions considering different triggering conditions for the Olinalá landslide, a paleo-landslide located in the northern front of the Sierra Madre Oriental, northeastern Mexico. Models included assessment of the influence of both aseismic (suggesting different groundwater levels) and a strong earthquake shaking scenario.
Results suggest the Olinalá landslide is relatively stable even considering a fully-saturated hydrological stage through the slope (e.g., after the impact of major hurricanes), a typical situation in the study area. Considering these circumstances, there is no evidence of a reactivation of the landslide after the impact of hurricanes in the region. Conversely, hazardous scenarios result after evaluate a combined influence of moderate seismicity and extreme hydrometeorological conditions. This study suggests that some geomorphological features observed in northeastern Mexico are unfeasible without considering the effect of earthquakes. Our approach could model the behavior of pseudostable old landslides through the region, in the face of future reactivations and risk situations.
The paper can be downloaded in https://rdcu.be/b3QQ0
... logistic regression, linear regression) use binary dependent variables corresponding to the presence (1) or absence (0) of a landslide. Very few studies distinguish active, dormant, and reactivated landslides to derive landslide susceptibility (Chung and Glade, 2004;Cascini, 2008;Marjanović et al., 2011), or present prediction maps of landslide reactivation hazard (Chung and Glade, 2004;Dewitte et al., 2006). In J. Du, et al. ...
The Himalayan range is one of the most tectonically active mountain ranges on Earth. The Jilong Valley is a deeply-dissected canyon in the Chinese Himalayas in Tibet, and in this valley, landslide hazard and risk have increased significantly in response to active crustal movements, intense rainfall and ever-increasing human interference. Landslide susceptibility assessment in the valley is fundamental for risk mitigation and to inform land use and planning but remains a challenge owing to the inaccessible high altitude and incomplete landslide inventory. In addition, because of sustained glacial erosion, weathering, and denudation, there is considerable uncertainty in the use of remote sensing interpretation of landslides in high-altitude terrain. In this paper, therefore, a systematic approach for landslide susceptibility assessment is proposed, combining the interpretations from remotely sensed dataset and both heuristic and statistical susceptibility models to overcome the problem of the limited spatial coverage of landslide data and uncertainty in landslide interpretation. The main steps include: 1) landslide field investigation and interpretation and the compilation of a preliminary landslide inventory, including certain and probable landslides, 2) knowledge-driven identification of landslide-prone areas based on the heuristic model, 3) classification and quantification of the uncertainty of probable landslides through heuristic landslide-prone areas mapping and the production of a revised landslide inventory, and 4) data-driven susceptibility assessment using a statistical model. In the statistical model, the landslide samples have multivalent dependent variables between 0 and 1. Therefore, a multinomial statistical classifier and multiclass Receiver Operation Characteristic curves are needed for model calibration and validation. The statistical susceptibility mapping showed good performance in the study area, with an average AUC of 0.867, which is a significant improvement over the heuristic model. The methodology presented can be used for landslide susceptibility mapping in data-scarce environments, not only in the Himalayan region but also in other mountainous areas where there is a lack of data on past landslide occurrences.
... Instead, the 330 data was split according to 10 sub-regions of the study area (Rwanda, Burundi, and 8 administrative zones in the DRC). This technique allowed to assess the transferability of the models to new regions (Dewitte et al., 2006;Brenning, 2012;Petschko et al., 2014b;Steger et al., 2016). Note that within the CV and SCV, the hyperparameters for the SVM model were tuned for each cross-335 validation training set. ...
Predicting landslide occurrence is of key importance for understanding the geomorphological development of mountain environments as well as to assess the potential risk posed by landsliding to human societies in such environments. Global landslide susceptibility models use a generic model formulation to predict landslide susceptibility anywhere on the planet from openly available data. Regional models, on the contrary, use local information on landslide occurrence to constrain model parameters and may also benefit from better spatial information with respect to controlling factors. This study aims to investigate the added value of the construction of regional landslide susceptibility models (versus global and continental models) in the western branch of the East African Rift, a data-scarce landslide-prone tropical environment. First, a comprehensive landslide database containing 6446 instances was compiled for the study area using Google Earth imagery. Second, three regional data-driven landslide susceptibility models were developed. Third, the efforts to construct these regional models were quantified by analysing how their quality is impacted by (1) the use of more accurate, regional peak ground acceleration and geology data, and (2) an increasing inventory size. Fourth, regional and global/continental models were compared in terms of predictive power and geomorphological plausibility. We observe that global/continental landslide susceptibility models are capable of identifying landslide-prone areas, but lack prediction power and geomorphological plausibility when compared to our regional models. Importantly, this difference in quality is not driven by the use of more accurate and detailed geology and peak ground acceleration data, but rather by the use of a detailed regional landslide inventory to calibrate the models. We also show that the model quality only increases marginally beyond a certain inventory size. We conclude that the regional landslide susceptibility assessment does provide an added value compared to existing global models in terms of geomorphological plausibility and model performance, whereby the largest gain is to be found in the construction of a regional landslide inventory, rather than the investment in more detailed covariates or the application of more complex modelling techniques. The latter suggests that the role of controlling variables depends, to some extent, on the regional context: making adequate susceptibility predictions proves difficult when local conditions are not accounted for by means of a regional inventory.
... As stated above, large deep-seated landslides in the Flemish Ardennes occurred in an undefined epoch far before present time and due to specific environmental conditions. In contrast, observation of their current activity strongly suggests that the most probable mass movement hazard in these regions is actually not the occurrence of new such landslides but reactivation of the pre-existing ones (Dewitte and Demoulin 2005;Dewitte et al. 2006Dewitte et al. , 2008Dewitte et al. , 2009Dewitte et al. , 2010. Located on the Leupegem hill, Flemish Ardennes, next to the town of Oudenaarde (Landslide 1, Fig. 20.4), the Hekkebrugstraat landslide (HL) is a representative example of these deep-seated rotational earth slides. ...
Most landslides in Belgium, and especially the largest features, do not occur in the Ardenne, where the relief energy and the climate conditions seem most favourable. They appear in regions located mainly north of them where the lithology consists primarily of unconsolidated material. They develop on slopes that are relatively smooth, and their magnitude is pretty large with regard to that context. An inventory of more than 300 pre-Holocene to recent landslides has been mapped. Twenty-seven percent of all inventoried landslides are shallow complex landslides that show signs of recent activity. The remaining landslides are deep-seated features and rotational earth slides dominate (n > 200). For such landslides, the average area is 3.9 ha, but affected areas vary from 0.2 to 40.4 ha. The exact age of the deep-seated landslides is unknown, but it is certain that during the last century no such landslides were initiated. Both climatic and seismic conditions during the Quaternary may have triggered landslides. The produced landslide inventory is a historical inventory containing landslides of different ages and triggering events. Currently, only new shallow landslides or reactivations within existing deep-seated landslides occur. The focus on the Hekkebrugstraat landslide in the Flemish Ardennes allows us to understand the recent dynamics of a large reactivated landslide. It shows the complexity of the interactions between natural and human-induced processes. The focus on the Pays the Herve allows for a deeper understanding of landslide mechanisms and the cause of their origin in natural environmental conditions. These two examples are among the best-studied landslides and their analysis allows us to highlight the main processes at play and to better unravel their interactions.
... Their characteristics are crescentic-shaped headscarps, gentle multi-terraces, and steeply sloping toes that stretch into rivers (Wang et al. 2003;He 2005;Dong et al. 2014). Topographically, the 1500 m long and 4000 m wide DAL shows similar characteristics as these ancient landslides, being steep at the upper part and the foot, and having gentle step-like terraces in the middle part (Figs. 2 and 3) (Jones 1993;Dewitte et al. 2006;Panek et al. 2009;Jiao et al. 2013). ...
... Reactivity mechanism of the DRL As for most large-scale ancient landslides, the deposit usually deforms with gravitational creep (Cui et al. 2007). When it comes to the reactivity of ancient landslides, a large number of cases indicate that the new-forming sliding planes tend to occur along preexisting rupture surfaces, which are normally interfaces between rock and soil (Dai et al. 2000;Dewitte et al. 2006). Significantly, the formation mechanism of the rupture surface is sensitive to environmental changes and human disturbance (Jones 1993;Dai et al. 2000). ...
The Dongla Bridge, Muli County, China, is a key access road between counties in Sichuan Province and the only traffic facility for an important 500-kV electricity substation which provides power to nearby counties. In June 2011, during the bridge construction, an unknown landslide, subsequently named the Dongla Ancient Landslide (DAL), was encountered. Local reactivation of a portion of the DAL, termed the Dongla Reactivated Landslide (DRL), was indicated by evident ground deformation at the Dongla Bridge. In spite of this, transportation of some heavy electrical equipment to the substation was scheduled on 9 May 2013. So, to guarantee the stability and security of the bridge became a primary emergency task. Detailed field investigations of the landslide occurrence, monitoring and emergency mitigation construction were carried out in the period between 2011 and 2014. This resulted in a temporary stabilization of the revived landslide and ensured the timely transportation of the heavy electrical equipment. It is thought that the revival mechanism of the DRL is creep, translational sliding, and was mainly triggered by artificial slope-cutting, but also influenced by precipitation, river erosion, and man-made activities in the form of small-scale mining operations. Following complete failure of the DRL, the probability of landslide-dam and dam breach is proved to be small by risk analyses. This paper can provide an insight into the problems associated with the interaction between the human structures and landslide instabilities.
