Climate-Driven Slope Instability: Landslide Hazard at Danube riverside slopes (Hungary)

Pesisir Selatan District is one of the areas in West Sumatra that often experiences natural disasters of landslides. Natural disasters of landslides that occur in this area often cause losses in the form of property or human lives and disruption of road access to other areas. The aims of this research were to analyze the hazard of landslides based on land characteristics, analyze the carrying capacity of the region based on landslide hazards, analyze social vulnerability, and analyze prediction of Population loss. The method used in this study is a survey method with a geomorphological approach. Data used in the form of primary data and secondary data. The technical analysis used is in the form of scoring to analyze landslide hazards and GIS used to analyze the carrying capacity of the region, vulnerability, and exposed populations. The results showed that the hazard of landslides in the study area was divided into three, namely low, medium, and high hazards. The hazard of low landslides is generally found in plain areas near the coast. This area is formed due to the results of sedimentation processes from both rivers and the sea. The hazard of moderate landslides is generally found in hilly areas, and the hazard of high landslides is generally found in hilly or mountainous areas. The hazard of landslides is caused by physical characteristics in the form of high rainfall, steep slopes to very steep slope, high rock weathering. Social vulnerability in the research area is divided into two parts, namely low and medium. Low social vulnerability is caused by the ratio of male population more than female population, ratio of vulnerable groups, ratio of poor Population, and a ratio of disabled Population. Social vulnerability is being caused by a greater number of female populations, ratios of vulnerable groups, and disabled Population. The prediction of population loss found in the Lakitan Tengah area is in Lengayang Subdistrict, which is 11,869 Population.

The paper investigates the influence of a foundation layer on relatively steep undrained slopes with spatially variable soil strength. The definition of a relatively steep slope in this context is a slope angle that is steeper than that established by Taylor for the transition point between toe failures and base failures in uniform slopes which occurs at around 53°. It is shown that when the soil strength is spatially variable, critical failure mechanisms can pass into the foundation layer even in relatively steep slopes, which could never happen in a uniform soil. Although the worst‐case correlation length is a well‐established phenomenon in geotechnical reliability, it has usually been associated with slopes with relatively low factors of safety based on the mean. The paper demonstrates for the first time that even slopes with high factors of safety based on mean strength, can exhibit a striking worst‐case correlation length, confirming that failure to account for spatial variability can lead to unsafe predictions of the probability of failure.

The aim of the PhD thesis was to look for a relationship between the landslide-induced damage recorded on structures and facilities based on the results of several field campaigns and kinematic parameters quantitatively estimated by remote sensing techniques. Investigations were developed on two test sites: a deep-seated landslide in Colle Lapponi-Piano Ovetta in municipality of Agnone (Molise region, southern Italy) and the landslides affecting the southwestern sector of Volterra (Tuscany region, central Italy). First of all, a re-enactment of the evolution of both landslides were conducted, by means of 3D reconstructions based on historical aerial series of images and the analysis of Persistent Scatterers of ERS1/2, ENVISAT and COSMO-SkyMed satellites. The 3D Points Clouds and models were developed on several sets of aerial historical images dating from different years starting from 1945 and 1954 for Agnone and Volterra, respectively. To better understand the morpho-evolutionary stages, a qualitative assessment of changes of volume were made combining the oldest and the latest 3D reconstructed Points Clouds. This interpretation, even if qualitative and not quantitative, can be helpful for understanding possible effects of future reactivations and as a support to realize mitigation plans, susceptibility maps and other useful for the local administrators. The Persistent Scatterers were used to monitor the evolution in recent years, up to 2015. Then, for both case studies, the damage was revealed on structures and facilities by several field surveys and classified by means of five literature damage categorizations. During their application, some drawbacks and benefits of the methodologies were carried out and a new approach to improve the categorization of the damage on structures, facilities and ground surfaces was developed. This was conceived in two subsequent phases: i) a classification to use during the field campaign to quantify the severity of cracks and fractures on structures, facilities and ground surfaces; ii) an a posteriori ranking to apply on the entire structure, involving the extension of damage classes, performed by a cell-grid matrix. Furthermore, a damage recording scheme, useful for the recognition of cracks and fractures during the field surveys, was proposed. A critical comparison between the results obtained applying the different classification approaches, then followed. Buildings and facilities, for both sites, were categorized using also kinematic parameters such as velocity and maximum displacement measured along the Line Of Sight, derived by A-DInSAR, and their absolute values re-projected along the steepest local slope. Once characterized and categorized all structures and facilities of both sites of interest, a correlation between the surveyed damage classes and the deriving parameters by satellite were looked for. The investigation was carried to understand the behaviour of entire structures, subject to displacements. The first analysis was conducted on the Agnone test site where for several constructions an upper regression line between damage categories and velocity reprojected along the slope was recognized. Some outlayers were identified, mainly for low damage levels, then singularly investigated. To assess the reliability of all the structures, a matrix involving damage and velocity along the slope parameter acquired by ENVISAT and COSMO-SkyMed sensors was developed in order to obtain a classification. To validate the correlation and the reliability matrix the same procedure was applied to the Volterra site. Once asserted the validity of the relation between the velocity reprojected along the steepest slope and the classes of damage also for this area, the reliability matrix was applied on the constructions of the Volterra site. In this way, the relation between the displacement occurred during the period covered by ENVISAT and COSMO-SkyMed shows how the surveyed damage construction are related to the displacement. Some areas where damage occurred in the 2000 shows high reliability with ENVISAT recorded velocity, while others structures exhibits high reliability with COSMO-SkyMed data. The results were interesting because they highlight the fact that for some construction there is correlation between velocity of displacement of the entire structure and affecting damage; for others, instead, the high damage is related to the differential settlement and not necessarily to a high rate of displacement velocity.

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.

Abstract. The Umbria Region of Central Italy has a long history of mass movements. Landslides range from fast moving rock falls and debris flows, most abundant in mountain areas, to slow moving complex failures extending up to several hectares in the hilly part of the Region. Despite landslides occurring every year in Umbria, their impact remains largely unknown. We present an estimate of the impact of slope failures in the Umbria region based on the analysis of a catalogue of historical information on landslide events, a recent and detailed regional landslide inventory map, and three event inventories prepared after major landslide triggering events. Emphasis is given to the impact of landslides on the population, the transportation network, and the built-up areas. Analysis of the available historical information reveals that 1488 landslide events occurred at 1292 sites in Umbria between 1917 and 2001. In the same period 16 people died or were missing and 31 people were injured by slope movements. Roads and railways were damaged by slope failures at 661 sites, and 281 built-up areas suffered landslide damage. Three event inventories showing landslides triggered by high intensity rainfall events in the period 1937–1941, rapid snow melting in January 1997, and earthquakes in September–October 1997, indicate the type, abundance and distribution of damage to the population, the built-up areas and the transportation network caused by typical landslide-triggering events. Analysis of a geomorphological landslide inventory map reveals that in some of the municipalities in the region total landslide area exceeds 25%. Of the more than 45 700 landslide areas shown in the geomorphological inventory map, 4115 intersect a road or railway, and 6119 intersect a built-up area. In these areas slope failures can be expected during future landslide triggering events.

<p>The spatial impact of a single shallow landslide is small compared to a deep-seated, impactful failure and hence its damage potential localized and limited. Yet, their higher frequency of occurrence and spatio-temporal correlation in response to external triggering events such as strong precipitation, nevertheless result in dramatic risks for population, infrastructure and environment. It is therefore essential to continuously investigate and analyze the spatial hazard that shallow landslides pose. Its visualisation through regularly-updated, dynamic hazard maps can be used by decision and policy makers. Even though a number of data-driven approaches for shallow landslide hazard mapping exist, a generic workflow has not yet been described. Therefore, we introduce a scalable and modular machine learning-based workflow for shallow landslide hazard prediction in this study. The scientific test case for the development of the workflow investigates the rainfall-triggered shallow landslide hazard in Switzerland. A benchmark dataset was compiled based on a historic landslide database as presence data, as well as a pseudo-random choice of absence locations, to train the data-driven model. Features included in this dataset comprise at the current stage 14 parameters from topography, soil type, land cover and hydrology. This work also focuses on the investigation of a suitable approach to choose absence locations and the influence of this choice on the predicted hazard as their influence is not comprehensively studied. We aim at enabling time-dependent and dynamic hazard mapping by incorporating time-dependent precipitation data into the training dataset with static features. Inclusion of temporal trigger factors, i.e. rainfall, enables a regularly-updated landslide hazard map based on the precipitation forecast. Our approach includes the investigation of a suitable precipitation metric for the occurrence of shallow landslides at the absence locations based on the statistical evaluation of the precipitation behavior at the presence locations. In this presentation, we will describe the modular workflow as well as the benchmark dataset and show preliminary results including above mentioned approaches to handle absence locations and time-dependent data.</p>

Some differences in soil slope‐depth relationships between the Great Basin and the Klamath Mountains were noted while mapping soils in arid to semiarid central Nevada and in humid western Siskiyou County, California. The noted relationships were tested statistically with data from 78 pedons sampled over bedrock in western Siskiyou County during the soil survey of the Klamath National Forest, 46 pedons in Dixie Valley, and 39 pedons in White River Valley, Nevada. Each of the areas has moderate proportions of both shallow and deep soils on very steep (61 to 82%) slopes. On moderately steep (16 to 30%) slopes, however, there is a larger proportion of deep soils in western Siskiyou County (α < 0.05), and a larger proportion of shallow soils in central Nevada. There is a significantly larger proportion of shallow soils on south than on north slope aspects in western Siskiyou County (α < 0.05). These different soil slope‐depth relationships are explicable by natural processes of slope, regolith, and soil evolution. There are few argillic horizons in soils with frigid or cryic soil temperature regimes in the Klamath Mountains; otherwise, soils with argillic horizons are more common on moderately steep and less common on very steep than on steep slopes (α < 0.01). No significant differences in argillic horizon frequencies were detected among pedons in soils with mesic soil temperature regimes on north and south slope aspects in western Siskiyou County.

During the highway construction along the Yangtze River in Anhui, China from 2015 to 2018, regional slope failures occurred frequently near the routes and constituted significant hazards to infrastructures. Especially from June to September in 2016 and 2017, the high-temperature weather and intensive rainfall hit this region, triggering a lot of slope failures. These slope failures have two puzzling features: (1) low height (2.5–5 m) or gentle dip angles (8–25°). Such height and dips are unlikely to fail in theory; (2) slope failure emerged immediately during rainfall, while the slope materials consist of clay soil with extremely low permeability. Field investigations, laboratory tests, and a large-scale slope model test were conducted to investigate the failure modes and mechanism of the slope failures. The results show (1) low steep slopes generally show failure modes of surface erosion, or repeated local failures around the slope shoulder, while the gentle slopes often display failure modes of overall failure or even landslides; (2) the slope material mainly contains clay mineral of illite and displays strong shrinkage ability, which is prone to forming desiccation cracks during drying evaporation. Desiccation cracks can significantly improve the infiltration capacity of soils with three or four orders of magnitude. Shear strength of the soil is sensitive to water and decreases sharply with the increased water content; (3) the large-scale slope model test confirms that desiccation cracks can induce slope failure by providing preferential flow pathways for rainwater to rapidly infiltrate into deep soils. Based on the above results, the difference of failure modes and scales between the steep slope and gentle slope is interpreted. It is inferred that desiccation cracks are difficult to develop stably and constantly on the inclined surface of steep slopes due to the intense surface runoff. Thus, surface erosion and shallow flow-slip dominate the failure modes of the low steep slopes. Conversely, a gentle slope surface is favorable for the development of desiccation cracks. Hence, overall slope instability or a landslide is more likely to occur in a gentle slope after long periods of drying-wetting cycles.

<p>According to the Centre for Research on Epidemiology of Disasters, every year landslides are to be blamed worldwide for at least 17% of all fatalities from natural disasters. Rainfall-induced shallow landslides are responsible for a significant number of those: they mobilize the first few meters (usually <2m) of soil, have high velocities and occur after abundant and prolonged rainfall events.</p><p>The runout of a landslide, defined as the difference between the total area of a landslide and its source area, from which the sediment is first mobilized, is what determines how far a landslide travels and how big the affected area is, and yet the runout is often neglected when it comes to analysing the overall hazard caused by potential landslides.</p><p>The land use practices have been proven as one of the factors which impact the susceptibility of an area to the formation of shallow landslides, it is however less clear if the land use also plays a role in influencing the size of the area of runout.</p><p>The aim of the present work is to investigate the correlation between the runout area and the land use in which the shallow landslide develops.</p><p>To do so, two inventories of landslides, which occurred in neighbouring regions in Northern Italy (Lombardy and Piedmont), comparable for lithology, land use, geomorphology and climate, were analysed.</p><p>The result of the analysis was that there were statistical differences in the distribution of the runout among different land use classes, meaning that an influence of the land use on the runout was highly probable. Such results could improve the comprehension on shallow landslides mobility and runout and could lead to the development of possible models of assessment of the runout at different scales.</p>

The nest-site preferences of six burrowing petrel species, Salvin's prion Pachyptila vittata salvini, blue petrel Halobaena caerulea, great-winged petrel Pterodroma macroptera, Kerguelen petrel Pterodroma brevirostris, soft-plumaged petrel Pterodroma mollis and white-chinned petrel Procellaria aequinoctialis, in the northeastern part of Marion Island (Prince Edward Island group, southern Indian Ocean) were analyzed by step-wise multiple regression. The nest-site characteristics measured were slope angle, soil depth and moisture content, percentage cover by stones or boulders and percentage cover by each of seven major plant species. The major nest-site preferences were: exposed areas with shallow soil (Salvin's prion); steep coastal slopes (blue petrel); sheltered well-drained slopes with deep soil (great-winged petrels); wet areas along drainage lines (Kerguelen petrel); steep slopes (soft-plumaged petrel); and areas with deep soil (white-chinned petrel). Similar species showed no significant avoidance of nest sites where there were burrows of potential competitors but did tend to nest spread out over different habitats. Burrow densities were determined in six habitat and seven vegetation types. Salvin's prion was the most abundant species (81% of burrows, with a maximum density of 279 burrows ha-1) and used both burrows and natural cavities for nesting. For all species combined, burrow densities at Marion Island were lower than in comparable habitats and vegetation types at neighbouring Prince Edward Island. Depredation by feral house cats Felis catus, absent from Prince Edward Island, is assumed to be largely responsible for this difference.

Rainfall induced landslides are one of the most frequent natural hazards on slanted terrains. They lead to significant economic losses and fatalities worldwide. Most factors inducing shallow landslides are local and can only be mapped with high levels of uncertainty at larger scales. This work presents an attempt to determine slope instability using buffer and threshold techniques to downscale large areas and minimize slope uncertainties at local scales, then in a second stage, logistic regression is used to determine susceptibility at large scales. ASTER GDEM V2 is used for topographical characterization of slope and buffer analysis. Four static parameters (slope angle, soil type, land cover and elevation) for 230 shallow rainfall-induced landslides listed in a comprehensive landslide inventory for the continental United States are examined. A delimiting buffer equivalent to 5, 25 or 50 km is created around each landslide event facilitating the statistical analysis of slope thresholds. Slope angle thresholds at the pixel points 50, 75, 95, 99 and maximum percentiles are compared to one another and tested for best fit in a logistic regression environment. It is determined that values lower than the 75-percentile threshold misrepresents susceptible slope angles by not including slopes higher than 35°. Best range of slope angles and regression fit can be achieved when utilizing the 99 percentile slope angle threshold. The resulting logistic regression model predicts the highest number of cases correctly with 97.2% accuracy. The logistic regression model is carried over to ArcGIS where all variables are processed based on their corresponding coefficients. A regional landslide probability map for the continental United States is created and analyzed against the available landslide records and their spatial distributions. It is expected that future inclusion of dynamic parameters like precipitation and other proxies like soil moisture into the model will further improve accuracy. Keywords: Shallow landslides; Slope instability; Threshold analysis; Logistic regression; Regional analysis; GIS; Remote sensing Introduction Rainfall induced landslides are one of the most frequent natural hazards on slanted terrains. They usually result in great economic losses and fatalities globally. Worldwide at least 32,322 deaths between 2004 and 2010 have been reported [1] and in the United States alone, landslides cause $1-2 billion in damages and more than 25 fatalities in average each year [2]. Understanding, mapping, modeling and preventing the aftermath of these devastating events represents an important scientific and operational endeavor [3]. The term “Landslide” describes the downward and outward movement of slope-forming materials that include rock, earth, and debris or a combination of these [4]. Although landslides are considered to be dependent on the complex interaction of several static and dynamic factors [5-7] slope angle has great influence on the susceptibility of a slope to sliding. Increased slope angle usually correlates to increased likelihood of failure even if the material distribution on the slope is uniform and isotropic [5]. Undeniably, many other parameters are essential to the analysis of landslide risk. For example, changes in land use and land cover such as deforestation, forest logging, road construction, cultivation and fire on steep slopes can have a significant effect on landslide activity [8]. In addition, forest vegetation

Tropical mountainous regions are often identified as landslide hotspots with particularly vulnerable populations. Anthropogenic factors are assumed to play a role in the occurrence of landslides in these populated regions, yet the relative importance of these human-induced factors remains poorly documented. In this work, we aim to explore the impact of forest cover dynamics, roads and mining activities on the occurrence of landslides in the Rift flank west of Lake Kivu in the DR Congo. To do so, we compile an inventory of 2730 landslides using © Google Earth imagery, high resolution topographic data, historical aerial photographs from the 1950’s and extensive field surveys. We identify old and recent (post 1950’s) landslides, making a distinction between deep-seated and shallow landslides, road landslides and mining landslides. We find that susceptibility patterns and area distributions are different between old and recent deep-seated landslides, which shows that natural factors contributing to their occurrence were either different or changed over time. Observed shallow landslides are recent processes that all occurred in the past two decades. The analysis of their susceptibility indicates that forest dynamics and the presence of roads play a key role in their regional distribution pattern. Under similar topographic conditions, shallow landslides are more frequent, but of smaller size, in areas where deforestation has occurred since the 1950’s as compared to shallow landslides in forest areas, i.e. in natural environments. We attribute this size reduction to the decrease of regolith cohesion due to forest loss, which allows for a smaller minimum critical area for landsliding. In areas that were already deforested in 1950’s, shallow landslides are less frequent, larger, and occur on less steep slopes. This suggests a combined role between regolith availability and soil management practices that influence erosion and water infiltration. Mining activities increase the odds of landsliding. Mining and road landslides are larger than shallow landslides but smaller than the recent deep-seated instabilities. The susceptibility models calibrated for shallow and deep-seated landslides do not predict them well, highlighting that they are controlled by environmental factors that are not present under natural conditions. Our analysis demonstrates the role of human activities on the occurrence of landslides in the Lake Kivu region. Overall, it highlights the need to consider this context when studying hillslope instability characteristics and distribution patterns in regions under anthropogenic pressure. Our work also highlights the importance of considering the timing of landslides over a multi-decadal period of observation.

<p>Tropical mountainous regions are often identified as landslide hotspots with particularly vulnerable populations. Whereas both natural (e.g., rainfall, lithology) and anthropogenic (e.g., deforestation, mining) factors are expected to be involved in landslide occurrence, the relative importance of such factors remains poorly documented. The objective of this study is to understand the role played by natural and anthropogenic factors in the occurrence of landslides in the Rift Flank west of Lake Kivu in DR Congo. First, we inventoried 2856 landslides of various types using Google Earth imagery, high resolution topographic data, historical aerial photographs from1950’sand intense field surveys. We made a distinction between old and recent deep-seated landslides, shallow landslides and mining-related landslides. The difference in susceptibility patterns and in size distributions between old and recent deep-seated landslides indicates that natural factors contributing to their occurrence were either different or changed over time. The shallow landslides are all recent. The susceptibility analysis shows that their regional pattern is mainly controlled by forest dynamics and the presence of roads. The occurrence of shallow landslides in forest areas, i.e. in natural environments, strongly increases with slope gradient. In areas with similar topographic conditions where deforestation has occurred since the 1950’s, shallow landslides are more frequent, but of smaller size. This size reduction is attributed to the decrease of regolith cohesion due to forest loss, which allows a smaller minimum critical area for landsliding. In areas that were already deforested in 1950’s, shallow landslides are less frequent, larger, and occur on less steep slopes. This suggests a combined role between regolith availability and soil management practices that influence erosion and water infiltration. Landslides associated with mining activities are larger than shallow landslides but smaller than the recent deep-seated instabilities. They are not well predicted by the susceptibility models, showing that they respond to environmental factors that are not present under natural conditions. This research highlights the importance of human activities on the occurrence of landslides and the need to consider this context when studying hillslope instability patterns in regions under anthropic pressure.</p><p> </p><p>Keywords: landslide processes, multi-temporal inventory, historical deforestation, mining and quarrying, susceptibility assessment, Africa</p>

The strength of rock mass and the stress in a slope are each complex fields of investigation. They are also intimately related as increasing confining stress makes a rock mass stronger and the strength of a rock mass can limit the magnitude of stress. Whereas these interactions are comparatively well understood for soils, principally through the advances of laboratory soil mechanics, the scale of rock masses, principally the presence of discontinuity surfaces, limits the capacity for laboratory investigation. The interaction of strength and stress in rock slopes is most evident in high, steep slopes where stress is typically greater. The slope angle and failure mechanisms occurring in the rock slope can reveal the ways that strength and stress interact to produce the observed morphology. McKay Bluff, near Nelson, South Island, New Zealand, is a high, steep rock slope affected by marine coastal erosion at its base. Finite element modeling illustrates sensitivities in determination of the stress magnitude in the slope. Engineering geology methods demonstrate the difficulty in precise determination of the rock mass strength. The ranges of these parameters are compared to find a compatible range for the interacting factors. The stress in a range of other high, steep slope types is reviewed and the implications for geomorphic analysis are discussed.

Reconstructing high-magnitude/low-frequency landslide events based on soil redistribution modelling and a Late-Holocene sediment record from New Zealand