Canadian ‘landslide’

We analyzed multi-time satellite images of the Central Caucasus glacial zone and interpreted more than thirty rock avalanche events in the 21st century with a total damage area of more than 25 km2 (including the collapse zone of the Kolka Glacier disaster). The highest rock and rock-ice avalanche activity is detected in the section of The Greater Caucasus range (northern and southern slopes) with a length of about 20 km between the Bashkara and Kulaktau peaks (16 rock avalanches) and in the section of the Kazbek-Dzhimaray Massif (series of rock avalanches to the surface of Kolka, Suatisi and Devdoraki glaciers). The feature of the rock and ice-rock avalanches is the large runout distance. For 12 events (about 40%) the distance was more than 2000 m. One ice-rock avalanche from the Mount Kazbek (excluding the Kolka Glacier disaster in 2002) reached the runout distance more than 10 km. In some areas, the rock avalanches occurred several times. In particular, a large number of avalanches were in the cirque of the Kolka Glacier; the last of them at the end of 2019. Thrice шт each case, rock avalanches originated from Mount Bashkara, in the cirques of the Murkvam Glacier, the East Shtulu Glacier, and the Devdoraki Glacier. Ice and rock avalanches were the initial stage of the complex process of the Kolka Glacier disaster and following catastrophic glacial debris flow in the Genaldon/Gizeldon River valley in 2002. Also, they were causes of glacier surges, formation of dammed lakes, and debris flows. As a result of the collapse of the hanging glacier and bedrock, the former right tributary of the Kolka Glacier surged to 200 m in 2006. Ice-rock avalanche from Mount Kazbek in 2014 load up the former right tributary of the Devdoraki Glacier and caused its advancing in 2015–2019, at a distance of more than 400 m. The avalanches caused catastrophic debris flows in the Amilishka/Kabakhi River valley in 2014, the Mestiachala River valley in 2019. Rock avalanches can cause outbursts of lakes and debris flows. Two dammed lakes formed as a result of the rock avalanche from the cirque above the Seri Glacier in the Tviberi River valley of the in May 2016. The lakes (total area was more than 0.05 km2) have outburst at the end of August 2017 after heavy rains. Rock avalanches of the 20th century led to an abrupt deceleration in the retreat of the Yusengi, Bartuytsete, East Shtulu and Mosota glaciers. The formation of rock avalanches in the 21st century took place at high altitudes (an average of about 3900 m). Possibly, the reason was associated with an increase of the «0» isotherm and of the high border of the zone of intense frost weathering due to climate warming. Some rock avalanches in the section of the Kazbek-Dzhimarai Massif have been caused by endogenous factors (seismicity and volcanism).

Introduction: Landslides are one of the critical natural processes, which cause enormous damage to life and property..Uttarakhand Himalaya is vital to sustainity of region. This region is very fragile due to topographic and climatic condition. Landslides in the mountainous terrains are natural derivational processes and one of the most. There is a need for Landslide Hazard Zonation for identification of potential landslide areas. Keeping this in mind one hilly district, Pauri district of Uttarakhand, India was selected. Materials and Methods: The present study is an attempt towards development of a landslide model by using multi-criteria decision analysis in GIS and remote sensing techniques for landslide hazard zonation. The IRS LISS-4 satellite imageries, Survey of India topographical maps, and ancillary data were used as inputs to the study. The data layers of land use–land cover and geology were interpreted from satellite image and available ancillary data. Other raster thematic layers, i.e., slope, aspect, elevation, and drainage density, have been generated in Arc info three-dimensional analyst tool using ASTER DEM of 30 m resolution. A numerical rating scheme for the factors was developed for spatial data analysis in GIS. Results and Decision: Using high-resolution LISS-IV and Cartosat-2A, merged data of 2011–2012 landslides were mapped by visual interpretation of satellite image. A total of 167 landslides have been identified. Elevation map of Pauri district was prepared by classifying digital elevation model into 5 elevation categories. Distribution of landslides in different elevation categories is also done. Maximum landslides have occurred in elevation category (710–1134 m) and (185–709 m). Slope map has been generated and classifi ed into 6 slope classes, i.e. 0°–5°, 5°–10°, 10°–20°, 20°–30°, 30°–40°, and more than 40°. Distribution of landslides in different slope categories is also done. Maximum landslides have occurred in slopecategories (10°–20°), (20°–30°), and (30°–40°). Aspect map has been generated and classified into 8 aspect classes. Maximum landslides have occurred in aspect categories South-West (14.37%), South (35.97%), and South East (15.57%) directions. The Southern aspect (SW-S-SE) contributes to 65.91% of total landslides. Drainage density map has been generated from ASTER DEM using three-dimensional Analyst tool and classified into 6 classes, namely 0–2, 2–4, 4–6, 6–8, and more than 8 (km/sq.km). Geological map of Pauri district has been adopted from Geological map from Geological SOI. Rock types such as phyllites, quartzites, slates, siltstone, sandstones, graywacks, granitoids, alluvium, crystallines and metamorphics, and limestones are present in the district. Distribution of landslides in different drainage density categories is also done. Maximum landslides have occurred in drainage density category 2–4, 4–6, and 6–8 (km/sq.km). LULC map of Pauri was classified into various classes such as water body, forest scrub, wasteland/scrub, tree-clad, forest evergreen, agriculture land, built up, forest deciduous open, and forest deciduous dense/close. Maximum landslides have occurred in forest deciduous open category (84) followed by agriculture land (22), forest scrub (14), forest evergreen and forest deciduous dense/close (13 each), and water body. Conclusion: The above-mentioned 6 layers were integrated in the weighted overlay model of Arc Info and weights were assigned corresponding to landslide occurrence in these layers. The influence of the layer in causing landslide has also assigned. The final LHZ map generated after processing 6 themes. The final map has been classified into 3 categories, namely high, moderate, and low hazard categories. Of a total of 167 landslides, 110Landslides fall in the high HZ and 43 landslides fall in moderate HZ category while only 14 landslides fall in the low HZ category. 34.01% of the district falls under low HZ category and 40.73% falls under moderate HZ category while 25.26 under high HZ category. More layers need to be added in the model to obtain more precision. This map is not checked in the fi eld ground truth.

روستای هاونان در 15کیلومتری جنوب غرب بیرجند و در دامنه شمالی رشته‌کوه باقران واقع شده و تاریخ اولین حرکت اصلی لغزش در منطقه در سال 1364 و تاریخ آخرین حرکت اصلی در سال 1385 است. در این مقاله پهنه‌بندی حساسیت به لغزش و تحلیل پارامترهای فیزیکی- هیدرولوژیکی و تکتونیکی به‌منظور شناسایی بیشتر وضعیت شکل‌گیری توده‌های لغزشی منطقه و تحلیل پایداری دامنه‌ها به کمک مدل فرآیندی SINMAP انجام‌شده است. این مدل نشان می‌دهد بخش اندکی از پهنه لغزشی هاونان در محدوده رطوبتی اشباع قرار می‌گیرد و کمتر از 30 درصد آن دارای حساسیت متوسط تا بالا به لغزش است؛ لذا بایستی در این محدوده به دنبال علل خارجی تأثیرگذار در پدیداری لغزش بود. محدوده هاونان متأثر از سه سری گسل اصلی با روندهای مختلف می‌باشد و در اثر تقاطع این سه سری گسل، واحدهای سنگی (اسپیلیت ها، پریدوتیت ها و گابروها) به‌صورت بلوک‌های گسلی کشیده درآمده و در اثر ادامه فرآیند برش، این بلوک‌ها متحمل تغییر شکل، جابجایی و چرخش شده‌اند. ترکیب سنگ‌شناسی (قرارگیری اسپیلیت بر روی سرپانتینیت) و وجود دو سری شکستگی به‌موازات گسل‌های هاونان و مزار مهم‌ترین عوامل ناپایداری هستند. علاوه بر این برخاستگی رشته‌کوه باقران باعث افزایش تدریجی نشیب دامنه و رخداد زمین‌لرزه‌ای ادواری نیز موجب تشدید لغزش می‌گردد.

Slope failure is one of the serious issues faced by geotechnical engineers, the mechanism of which are case-specific. Shear strength and rainfall are the two critical parameters that require careful consideration with regard to slope failure risk. A laboratory scale model set-up was developed to assess failure susceptibility in embankment slopes. The material used in this study was silty soil having 15% fine content. Rainfall induced failure mechanism was investigated. Effect of slope angle was studied to arrive at a safe slope in a low permeable soil. A warning system was developed using laser diodes that capture soil movement. It was found that during the event of rainfall, the factor of safety with respect to shear reduced drastically. The warning system could capture the surface movement that occur at any section along the slope. Small-scale experimentation set up developed in the present study has the convenience of adjusting slope geometry, soil properties and failure mechanisms.

The use of preevent and postevent digital elevation models (DEMs) to estimate the volume of rock avalanches on glaciers is complicated by ablation of ice before and after the rock avalanche, scour of material during rock avalanche emplacement, and postevent ablation and compaction of the rock avalanche deposit. We present a model to account for these processes in volume estimates of rock avalanches on glaciers. We applied our model by calculating the volume of the 28 June 2016 Lamplugh rock avalanche in Glacier Bay National Park, Alaska. We derived preevent and postevent 2‐m resolution DEMs from WorldView satellite stereo imagery. Using data from DEM differencing, we reconstructed the rock avalanche and adjacent surfaces at the time of occurrence by accounting for elevation changes due to ablation and scour of the ice surface, and postevent deposit changes. We accounted for uncertainties in our DEMs through precise coregistration and an assessment of relative elevation accuracy in bedrock control areas. The rock avalanche initially displaced 51.7 ± 1.5 Mm3of intact rock and then scoured and entrained 13.2 ± 2.2 Mm3of snow and ice during emplacement. We calculated the total deposit volume to be 69.9 ± 7.9 Mm3. Volume estimates that did not account for topographic changes due to ablation, scour, and compaction underestimated the deposit volume by 31.0–46.8 Mm3. Our model provides an improved framework for estimating uncertainties affecting rock avalanche volume measurements in glacial environments. These improvements can contribute to advances in the understanding of rock avalanche hazards and dynamics.

Rapid flow-like landslides are characterized by their high mobility and catastrophic consequences. These landslides tend to entrain a great amount of loose materials along their travelling paths, resulting in the enlargement of landslide volume and covering area. This phenomenon is called bed entrainment/scouring in literatures. Although previous studies showed that bed entrainment was a significant factor influencing the mobility of rapid flow-like landslides, few of them considered its impact on the rheology of the sliding mass, and needless to say quantifying this impact in numerical modeling. Therefore, this paper proposes an improved finite difference model based on momentum conservations of both the landslide and erodible mass. In this model, the influence of bed entrainment on the rheology of a landslide is quantified by modifying the rheological parameters of the landslide according to the calculated entrainment depth. Then the Ximiaodian landslide, a typical rapid flow-like landslide located at the south bank of the Jinghe River in Shaanxi Province, is simulated by the new model. It shows that the run-out process of this landslide can be divided into the rapid acceleration stage(0~5 s) and the slow deceleration stage(5~14 s). During the acceleration stage, the extent of entrainment is small, so its impact on the motion of this landslide is slight. However, the entrainment obviously promotes the mobility of this landslide at the deceleration stage by reducing the basal resistance. In addition, the modeling results of considering and not considering bed entrainment show totally different patterns. The simulated covering area and final deposit agree well with the measured data when adopting the improved model, while those neglecting the impact of bed entrainment-induced rheology change are obviously smaller than that of the fact. It turns out that the new model proposed here is more suitable for simulating those rapid flow-like landslides with similar bed entrainment phenomenon.

A physically-based multi-hazard risk assessment platform for regional rainfall-induced slope failures and debris flows

This study aimed to evaluate the landslide risk map in the Algerian Western coasts. This evaluation was based on three steps. The first step requires evaluating the landslide hazard. To reach this, a field surveys data, combined with Geographical Information System (GIS) analysis and Remote Sensing (RS) image processing were carried out. Seven controlling factors were considered: lithology, geomorphology, slope, land use, distance to stream, rainfall and distance to fault. A topographic map of 1/ 25 000 was used to generate a Digital Elevation Model (DEM) with 15 × 15 m of resolution. From this DEM, the slope was extracted. Based on knowledge approach, the different factors were weighted according a scale value ranging from 1 to 9. The lowest values were assigned to the factors which have a minor influence on landslide triggering, and the highest values were given to the important parameters for landslide occurrence. These factors were combined using weighted linear combination (WLC). The landslide hazard map was classified into five levels: very low, low, moderate, high and very high. The landslide vulnerability was evaluated through the identification of the elements at risk. Three vulnerabilities aspects were considered: physical, environmental and socio-economic. The weights of each factor were given depending on the magnitude and the rate of landslide. Landslide Vulnerability Map (LVM) for Algerian western coasts was generated by the combination of the physical, environment and socio-economic vulnerability maps. Landslide risk was evaluated by combining the hazard map and the vulnerability map, and it was divided into four classes: very low, low, moderate and high.

Landslide hazard and risk are growing as a consequence of climate change and demographic pressure. Land‐use planning represents a powerful tool to manage this socio‐economic problem and build sustainable and landslide resilient communities. Landslide inventory maps are a cornerstone of land‐use planning and, consequently, their quality assessment represents a burning issue. This work aimed to define the quality parameters of a landslide inventory and assess its spatial and temporal accuracy with regard to its possible applications to land‐use planning. In this sense, I proceeded according to a two‐steps approach. An overall assessment of the accuracy of data geographic positioning was performed on four case study sites located in the Italian Northern Apennines. The quantification of the overall spatial and temporal accuracy, instead, focused on the Dorgola Valley (Province of Reggio Emilia). The assessment of spatial accuracy involved a comparison between remotely sensed and field survey data, as well as an innovative fuzzylike analysis of a multi‐temporal landslide inventory map. Conversely, long‐ and short‐term landslide temporal persistence was appraised over a period of 60 years with the aid of 18 remotely sensed image sets. These results were eventually compared with the current Territorial Plan for Provincial Coordination (PTCP) of the Province of Reggio Emilia. The outcome of this work suggested that geomorphologically detected and mapped landslides are a significant approximation of a more complex reality. In order to convey to the end‐users this intrinsic uncertainty, a new form of cartographic representation is needed. In this sense, a fuzzy raster landslide map may be an option. With regard to land‐use planning, landslide inventory maps, if appropriately updated, confirmed to be essential decision‐support tools. This research, however, proved that their spatial and temporal uncertainty discourages any direct use as zoning maps, especially when zoning itself is associated to statutory or advisory regulations.

Modeling snowmelt influence on shallow landslides in Tartano valley, Italian Alps

Post-glacial rock avalanches in the Obersee Valley, Glarner Alps, Switzerland

A new theory of vision : Fritz Schanz. ( Zeit. f. Physik., Dec. 9, 1922)

A geospatial database of over 24,000 slope failures across the state of North Dakota was developed. The database revealed that nearly 1,500 slopes failures were larger than 100,000 m2 in area posing significant safety concerns and engineering issues. To better understand the influence of various conditioning factors, a statistical study was undertaken in this paper. The slope failures were found to be concentrated in western North Dakota primarily occurring in the Sentinel Butte Formation. Statistical analyses suggest that this is likely due to the steeper topography and the abundance of Sentinel Butte Formation in this region in comparison to eastern North Dakota. The number of slope failures were log-normally distributed with the slope inclination. The mean slope inclination on which slope failures occurred was found to be 9.5° with a standard deviation of 5.7°. Interestingly, despite the presence of high salt concentrations in the soils underlying the majority of the state, the slope failures were found to be concentrated in areas with low salt concentrations. This may be attributed to the lower shear strengths of the soils with lower pore fluid salinity than that of soils with greater concentrations of salinity in the pore fluid.

In this paper, the material point software(Anura 3D) is used to set up the contact algorithm and fluid-solid coupling. Based on the M-C strength criterion, the whole process of the true submarine landslide in the South Mediterranean is simulated and back-analyzed. The coefficient of friction is 0.052. The landslide starts at the foot of the slope and gradually develops to the interior to form a whole landslide body. The whole body of the landslide accelerates and slides along the slope. At the 15th second, the maximum speed is 14.52ms-1,after which the friction is due to friction. ResistanceSlide force, the landslide body begins to decelerate. At the 21st second, the landslide body slides into a gentle section(slope is 1.1),the sliding force is close to 0, and the speeds of different particles are different, so the diffusion occurs in the horizontal direction. In the 57s, the speed drops to 0 and the sliding stops, The final sliding distance is 420.3m. The concept of the comprehensive friction coefficient() of the contact surface of the submarine landslide was put forward, and the phenomenon of soil softening and hydroplaning caused by seawater mixing during the sliding process of the submarine landslide was characterized by , and applied to the submarine landslide movement.

In March 2015, exceptional meteoric events occurred in southern Piedmont caused a remarkable rise of the rivers water level of the Tanaro Basin with flooding and many landslides. The engineering geological study reported here, concerns a triggering of a previous landslide occurred in 1982 in the hills, shaped in the marine sedimentary succession (Lugagnano Clay, lower Pliocene) of the southern Asti Reliefs, near San Martino Alfieri village. Detailed geological, morphological and topographic surveys of this landslide, with the aim to recognize the morphological features linked to the previous landslide and those connected to the triggering of it, have been carried out. The reactivation of the landslide was highlighted by the presence of a main scarp with minor escarpments and tracks. The mechanism activation of the main landslide is due to a rotational movement. To define the engineering geological model of the landslide body, standard cone penetration tests. rotary drilling borings with S.P.T. and geotechnical laboratory tests were performed. Through surveys, both main slip surface and deep-water seepage have been detected. In details, failure mechanism in OC clays was caused by: a) rapid increase in the bulk density or volume weight during rainfall events; b) rise of interstitial pressures along the sliding surface with reduction of normal stress and consequent reduction of the shear strength along this surface (progressive failure); c) reduction of cohesion and friction angle, due to clay softening. The results of the study have highlighted the need, as a primary factor of slopes consolidation, to install sub-horizontal drainage pipes in order both to avoid subsoil imbibition and to control the changes of interstitial pressure. The consolidation works focused on the construction of containment structures with deep consolidation and the execution of drainage works in the landslide area.