In this brief communication, we describe a case study about monitoring a soft-rock coastal cliff using webcams and a strain sensor, located in the Apulia region (southeastern Italy). In this urban ...and touristic area, coastal recession is extremely rapid and rockfalls are very frequent. Using low-cost and open-source hardware and software, we are monitoring the area, trying to correlate both meteorological information with measures obtained from the crack meter and webcams, aiming to recognize potential precursor signals that could be triggered by instability phenomena.
The studied rock collapse structure is located on the Liburnian coast (Rijeka Bay, channel zone of the NE Adriatic). The relief of the southern part of this coast, with a length of 6.5 km, is a large ...escarpment with very steep to vertical slopes reaching heights of 100 m above sea level, as a result of tectonic movements along the Kvarner fault zone. These events probably led to a sudden relaxation of the highly fractured rock mass. The progressive expansion occurred at locations where previously favourably oriented faults and fissures had formed a polygonal rock collapse resembling a rock-slide which is the focus of this study. Another aim of this study is to reconstruct and explain the complex morphological evolution of the studied landslide, from the pre-failure deformations, through the failure itself, to post-failure displacements, as well as possible future instabilities. Recent techniques to survey the instability, location and to analyse the evolution of the rupture surface and its dimensions were combined (Unmanned Aerial Vehicle, Side Scan Sonar and Remotely Operated Vehicles). The estimated total volume of displaced rock mass is 950,000 m3. The lower part of the instability phenomenon was submerged during the Holocene sea level rise. Since then, a large part of the displaced rock mass has been in a stable position, with sporadic rock falls. However, given unfavourable orientation and discontinuity characteristics, as well as unfavourable environmental influences, possible instabilities might also be expected in the future.
Slope instabilities adjacent to transportation corridors require timely and precise assessment to determine the risk to road users, particularly when weather changes trigger these instabilities. In ...southern Alberta, Canada, near the town of Drumheller, a 500-m-long, 60-m-high slope adjacent to Highway 837 has a history of slope instabilities that includes rockfalls, frozen soil falls, and debris flows. The slope failures have blocked the road which increases user and maintenance costs. Due to unsafe conditions and the steepness of the slope (1H:1V inclination), it was only possible to undertake visual assessments of the slope conditions from the road. Advances in unmanned aerial vehicle (UAV) technology have resulted in a quick and safe tool for collecting detailed photographic records of the slope conditions. The combination of UAV data and photogrammetry methods allows engineers to remotely, safely, and quickly perform a precise assessment of the slope instabilities. The paper demonstrates the use of UAV-derived data to evaluate the following: critical instability areas in practice; the magnitude of instability events; the relationship between the drainage network and slope instabilities, and models for rockfall trajectory analyses. The paper also provides a methodology that can be implemented on other slope instabilities to support the decision-making process to define mitigation actions that are practical and minimize associated risks.
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.
On 18 November 2017, a magnitude Ms. 6.9 (Mw 6.4) earthquake struck Nyingchi, Tibet Autonomous Region, China, which is located in the famous Grand Canyon region of the Yarlung Zangbo River in the ...eastern Himalayas, Tibet. The Nyingchi event was a thrusting event, with a focal depth of 12 km at 29.87° N and 95.02° E. According to emergency investigations and remote sensing, the Nyingchi event triggered at least 1820 co-seismic landslides. The landslides mainly occurred in the Grand Canyon region within an area of 527 km
2
(the inner area of Namcha Barwa tectonic node). The landslide distribution characterises an obvious hanging wall effect and is classified as “small concentration region and large landslide distribution area”. The failure patterns mainly consist of rock falls, rock avalanches, and deposit failures. One co-seismic landslide partially blocked the Yarlung Zangbo River, and the barrier lake remained. Different influencing factors, such as the seismic fault, river, slope aspect, slope angle, rocks, and elevation, have different influences on landslide occurrences, and the co-seismic landslides in the hanging wall area and footwall area present obviously different characteristics. Additionally, the post-earthquake effect impacted the recent Sedongpu landslide.
Field investigations and back analyses were conducted on a rockfall hazard. The flexible barrier protection system constructed along the roadside was damaged by the rockfall impact and lost its ...mitigation ability. Vital physical characteristics such as rockfall trajectory and kinetic energy were presumed based on the data from the aerial survey and the slope digital model. A numerical model, including slope, rockfalls, and flexible barrier, was created and thus the impacting process was reproduced. It demonstrates that the impact kinetic energy of the rockfall is only around 40 % of its design protection energy. The improper connections of members are the leading causes of damage, which prevent the flexible barrier from producing significant deformation and reduce its capacity to absorb impact force. The damage can be avoided by changing the connections of the members to improve the ability of the nets and ropes to slide and deform. The calculation results indicate that the impact resistance of the optimized model is 3 times better than the actual project. The findings can be used as a guide when designing a flexible protection system that performs better.
In this work, we apply a physically based model, namely the
HIRESSS (HIgh REsolution Slope Stability Simulator) model, to forecast the
occurrence of shallow landslides at the regional scale. HIRESSS ...is a physically
based distributed slope stability simulator for analyzing shallow landslide
triggering conditions during a rainfall event. The modeling software is made up of two
parts: hydrological and geotechnical. The hydrological model is based on an
analytical solution from an approximated form of the Richards equation, while
the geotechnical stability model is based on an infinite slope model that
takes the unsaturated soil condition into account. The test area is a portion
of the Aosta Valley region, located in the northwest of the Alpine mountain chain. The
geomorphology of the region is characterized by steep slopes with elevations
ranging from 400 m a.s.l. on the Dora Baltea River's floodplain to
4810 m a.s.l. at Mont Blanc. In the study area, the mean annual
precipitation is about 800–900 mm. These features make the territory
very prone to landslides, mainly shallow rapid landslides and rockfalls.
In order to apply the model and to increase its reliability, an in-depth
study of the geotechnical and hydrological properties of hillslopes
controlling shallow landslide formation was conducted. In particular, two
campaigns of on site measurements and laboratory experiments were performed
using 12 survey points. The data collected contributed to the generation of an input map
of parameters for the HIRESSS model. In order to consider the effect of
vegetation on slope stability, the soil reinforcement due to the presence of
roots was also taken into account; this was done based on vegetation maps and
literature values of root cohesion. The model was applied using back analysis
for two past events that affected the Aosta Valley region between 2008 and
2009, triggering several fast shallow landslides. The validation of the
results, carried out using a database of past landslides, provided good
results and a good prediction accuracy for the HIRESSS model from both a
temporal and spatial point of view.
In this work an overview of the potential rock fall source areas and propagation assessment in the Province of Potenza territory has been presented. The rock fall process is characterized by two ...steps: the detachment of blocks and subsequently their propagation along the slope. The adopted methodology, used for the first time in the study area, and the software Histofit and FlowR have been very useful tools for the preliminary assessment of rock fall susceptibility at a regional scale, in particular because they have required low data of the study area. Only the DEM may be sufficient together with an appropriate choice of the input parameters and algorithms, that is to say: calculation method, directions algorithm, inertial algorithm and friction loss function. The output of the model is a map of the rock fall source areas, the propagation probabilities and the propagation kinetic energy. The results show that the adopted methodology is successful for the identification of rock fall source areas at a regional scale and the propagation probability obtaining an interesting rock fall susceptibility map.
Debris cover on glaciers is an important component of glacial systems as it influences climate–glacier dynamics and thus the lifespan of glaciers. Increasing air temperatures, permafrost thaw and ...rock faces freshly exposed by glacier downwasting in accumulation zones result in increased rockfall activity and debris input. In the ablation zone, negative mass balances result in an enhanced melt‐out of englacial debris. Glacier debris cover thus represents a clear signal of climate warming in mountain areas. To assess the temporal development of debris on glaciers of the Eastern Alps, Austria, we mapped debris cover on 255 glaciers using Landsat data at three time steps. We applied a ratio‐based threshold classification technique and analysed glacier catchment characteristics to understand debris sources better. Across the Austrian Alps, debris cover increased by more than 10% between 1996 and 2015 while glaciers retreated in response to climate warming. Debris cover distribution shows significant regional variability, with some mountain ranges being characterised by mean debris cover on glaciers of up to 75%. We also observed a general rise of the mean elevation of debris cover on glaciers in Austria. The debris cover distribution and dynamics are highly variable due to topographic, lithological and structural settings that determine the amount of debris delivered to and stored in the glacier system. Despite strong variation in debris cover, all glaciers investigated melted at increasing rates. We conclude that the retarding effects of debris cover on the mass balance and melt rate of Austrian glaciers is strongly subdued compared with other mountain areas. The study indicates that, if this trend continues, many glaciers in Austria may become fully debris covered. However, since debris cover seems to have little impact on melt rates, this would not lead to prolonged existence of debris‐covered ice compared with clean ice glaciers.
Across the Austrian Alps, debris cover on glaciers increased significantly between 1996 and 2015 while glaciers retreated inresponse to climate warming. Distribution and dynamics of debris cover are found being highly variable due to topographic,lithological and structural settings. We conclude that, if this trend continues, many glaciers in Austria may become fully debriscovered. Debris cover seems to have little impact on melt rates and will not extend the existence of debris‐covered ice compared with clean ice glaciers.
glaciers.
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