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In debris-flow disasters, boulders moving at high velocities cause significant damage to houses and other facilities. Through a flume model test, this study explored the influences of the length/width ratio of the boulders, the angle between the long axis of the boulders and the flow direction, and the density of the mudflow on their starting movement. The experimental results indicate that in the process of a mudflow impacting the boulders, the angle between the long axis and the flow direction influences the magnitude of the component forces of the dragging force in the long- and short-axis directions, thus causing the boulders to deviate. Deflection changes the area of action of the debris-flow drag force on the boulder. Once the boulder gains a certain velocity, it deviates toward a state in which the long axis is parallel to the flow direction to reduce the resistance in the movement process. When the long axis of the boulder is parallel to the flow direction, as the mass of the boulder decreases, the efficiency of the mudflow in transferring the velocity of the boulder increases. When there is an angle between the long axis of the boulder and the flow direction, as the angle increases, the area of the drag force and efficiency of the velocity transfer increase. The movement laws of boulders in mudflows are crucial for engineering construction and sustainable development in mountainous areas. [ABSTRACT FROM AUTHOR]

The paper discusses issues related to global climate change. It’s identified that climate change is associated with global warming, caused by a sharp increase in the concentration of greenhouse gases in the atmosphere. Climate warming is accompanied by intense snowmelt and water evaporation. The cloud cover that accumulates in the atmosphere contains a tremendous amount of water, which falls as prolonged heavy rainfall, leading to catastrophic floods accompanied by mudflows, landslides, and erosion processes. The authors developed simple, reliable, and relatively inexpensive protective structures used during floods, mudflows, and landslides. Additionally, new designs for coastal protection were developed. The construction of these structures utilizes waste materials such as recycled tires and reinforced concrete sleepers. [ABSTRACT FROM AUTHOR]

Tailings dam breach modelling studies have received considerable attention recently due to the rise in the number of tailings dam failures and catastrophic consequences caused by downstream flooding. Numerical models are useful tools in risk management for assisting urban planners in planning for the safe evacuation of the vulnerable communities located downstream in the so-called "shadow area" of such dams. Several challenges and uncertainties exist when conducting risk assessments of tailings dam failure. In this study, recent advances in modelling approaches for tailings dam breach analysis and downstream flood wave routing are summarized and critically reviewed. This study evaluates different mudflow modelling studies that involve single-phase, quasi-two-phase, and two-phase modelling approaches; dam breach outflow modelling; tailings rheological characterization; and application of geographic information system (GIS) and remote sensing to tailings dam breach analysis. Recommendations for further research are provided based on the findings. In addition, this study will help dam engineers and practitioners to maintain industry standards and include state-of-the-art practices in their work. [ABSTRACT FROM AUTHOR]

Extreme rainfall events, within the context of climate change, pose a heightened risk of geohazards to mountainous regions. On 22 June 2022, a rainstorm-induced landslide-mudflow occurred in a terraced field in Longsheng County, Guangxi Zhuang Autonomous Region, China. The disaster began as a rotational slide, and mobilized into a mudflow with high mobility and long runout, causing significant damage to the local community. This event served as a wake-up call not only for the safety of mountain settlements, but also for the protection of terraced fields as Globally Important Agricultural Heritage Systems. To elucidate the trigger and mudflow mobilization of the event, field investigation, hydrological and agricultural analyses, and laboratory tests were conducted. It was found that the persistent and record-breaking rainfall directly triggered the disaster by increasing pore water pressure. The transition from paddy terraces to dry terraces was deduced to have contributed to a lack of maintenance in the terrace drainage system, thereby heightening the likelihood of landslides. The mudflow mobilization was attributed to excess pore water pressure generated by soil contraction and an undrained condition maintained by low permeability soil. Soil experiencing sliding may be more susceptible to shear contraction, consequently resulting in long-runout motion. Under conditions of increasing extreme rainfall, greater attention needs to be paid to geo-disaster prevention and terraced field protection in mountainous regions. [ABSTRACT FROM AUTHOR]

Quito (Ecuador) has a history of mudflow events from ravines that pose significant risks to its urban areas. Located close to the Pichincha Volcanic Complex, on 31 January 2022, the northwest and central parts of the city were hit by a mudflow triggered by unusual rainfall in the upper part of the drainage, with 28 fatalities and several properties affected. This research focuses on the affected area from collector overflow to the end, considering sedimentological characteristics and behavior through various urban elements. This study integrates the analysis of videos, images, and sediment deposits to understand the dynamics and impacts of the mudflow using a multidisciplinary approach. The methodology includes verifying multimedia materials using free software alongside the Large-Scale Particle Image Velocimetry (LSPIV) to estimate the kinematic parameters of the mudflow. The affected area, reaching a maximum distance of 3.2 km from the overflow point, was divided into four zones for a detailed analysis, each characterized by its impact level and sediment distribution. Results indicate significant variations in mudflow behavior across different urban areas, influenced by topographical and anthropogenic factors. Multimedia analysis provided insights into the mudflow's velocity and evolution as it entered urban areas. The study also highlights the role of urban planning and infrastructure in modifying the mudflow's distribution, particularly in the Northern and Southern Axes of its path, compared with a similar 1975 event, seven times larger than this. It also contributes to understanding urban mudflow events in Quito, offering valuable insights for disaster risk management in similar contexts. [ABSTRACT FROM AUTHOR]

Quito (Ecuador) has a history of mudflow events from ravines that pose significant risks to its urban areas. Located close to the Pichincha Volcanic Complex, on 31 January 2022, the northwest and central parts of the city were hit by a mudflow triggered by unusual rainfall in the upper part of the drainage, with 28 fatalities and several properties affected. This research focuses on the affected area from collector overflow to the end, considering sedimentological characteristics and behavior through various urban elements. This study integrates the analysis of videos, images, and sediment deposits to understand the dynamics and impacts of the mudflow using a multidisciplinary approach. The methodology includes verifying multimedia materials using free software alongside the Large-Scale Particle Image Velocimetry (LSPIV) to estimate the kinematic parameters of the mudflow. The affected area, reaching a maximum distance of 3.2 km from the overflow point, was divided into four zones for a detailed analysis, each characterized by its impact level and sediment distribution. Results indicate significant variations in mudflow behavior across different urban areas, influenced by topographical and anthropogenic factors. Multimedia analysis provided insights into the mudflow’s velocity and evolution as it entered urban areas. The study also highlights the role of urban planning and infrastructure in modifying the mudflow’s distribution, particularly in the Northern and Southern Axes of its path, compared with a similar 1975 event, seven times larger than this. It also contributes to understanding urban mudflow events in Quito, offering valuable insights for disaster risk management in similar contexts.

This article is devoted to the study of the process of natural reforestation after a mudflow. Mudflows pose a significant threat to forest ecosystems, causing significant changes in the structure and composition of forest communities. Recovery processes can take different times depending on the intensity of the mudflow, local climatic conditions and other factors. The purpose of this study is to study the processes of natural reforestation occurring after a mudflow that affected the territory of the Almaty Nature Reserve. The main task is to analyze the dynamics of vegetation cover, assess the impact of mudflows on the structure of the forest community, and identify species that are most adapted to the conditions of natural restoration. An analysis of the consequences of mudflows for forest ecosystems was carried out, features of the dynamics of the formation of tree species of the phytocenosis and changes in its structure were identified, and factors influencing the successful restoration of forest cover were assessed. The results of the study allow us to more deeply understand the processes of natural reforestation and provide recommendations for optimizing natural mechanisms of forest restoration after natural disasters, such as mudflows. The data obtained are of practical importance for managing forest resources and maintaining the sustainability of forest ecosystems in conditions of a changing climate and natural disasters. [ABSTRACT FROM AUTHOR]

The paper presents particular issues of mudflow dynamics, one of the hazardous natural disasters, namely the theoretical study of the flow power during mudflow movement in the wave regime taking into account its rheological properties. The paper discusses the physical process of mudflow mass impetus accumulated in erosion banks, taking into account the impact of the tense state of the eroded mass, in particular, similar to soil mechanics problems, the density of the mudflow-forming mass (ρ), the free fall acceleration (g), angle of internal friction (φ), the adhesive force (Pe), the height equivalent to pressure (h′), the height of the mudflow-forming mass (H), the intensity of transverse pressure (P), and the value of the active pressure of the inertial mass cohesion (C) on the deformation mode of the mudflow mass. On the basis of the basic equations of mudflow dynamics and theoretical studies, an equation is obtained to calculate the values of flow power when mudflows move in the wave mode, taking into account the main rheological properties of a mudflow mass. [ABSTRACT FROM AUTHOR]

Debris flows are powered by sediment supplied from steep hillslopes where soils are often patchy and interrupted by bare‐bedrock cliffs. The role of patchy soils and cliffs in supplying sediment to channels remains unclear, particularly surrounding wildfire disturbances that heighten debris‐flow hazards by increasing sediment supply to channels. Here, we examine how variation in soil cover on hillslopes affects sediment sizes in channels surrounding the 2020 El Dorado wildfire, which burned debris‐flow prone slopes in the San Bernardino Mountains, California. We focus on six headwater catchments (<0.1 km2) where hillslope sources ranged from a continuous soil mantle to 95% bare‐bedrock cliffs. At each site, we measured sediment grain size distributions at the same channel locations before and immediately following the wildfire. We compared results to a mixing model that accounts for three distinct hillslope sediment sources distinguished by local slope thresholds. We find that channel sediment in fully soil‐mantled catchments reflects hillslope soils (D50 = 0.1–0.2 cm) both before and after the wildfire. In steeper catchments with cliffs, channel sediment is consistently coarse prior to fire (D50 = 6–32 cm) and reflects bedrock fracture spacing, despite cliffs representing anywhere from 5% to 95% of the sediment source area. Following the fire, channel sediment size reduces most (5‐ to 20‐fold) in catchments where hillslope sources are predominantly soil covered but with patches of cliffs. The abrupt fining of channel sediment is thought to facilitate postfire debris‐flow initiation, and our results imply that this effect is greatest where bare‐bedrock cliffs are present but not dominant. A patchwork of bare‐bedrock cliffs is common in steeplands where hillslopes respond to channel incision by landsliding. We show how local slope thresholds applied to such terrain aid in estimating sediment supply conditions before two destructive debris flows that eventually nucleated in these study catchments in 2022. [ABSTRACT FROM AUTHOR]

The purpose of this work is to develop a hybrid model for predicting the consequences of a mudflow breakthrough of hydraulic structures, such as dams and dams. The presented work is devoted to the automation of the processes of modeling and analysis of the destruction of hydraulic structures, based on modern methods of hydrodynamics and thermophysics. The relevance of this work is due to the increasing frequency and scale of catastrophic floods caused by the destruction of hydraulic structures, which requires effective methods for predicting and preventing such events. The methods and models proposed in the work are of significant practical importance for risk assessment, planning evacuation measures and minimizing damage from emergencies associated with dam and dam breaks. [ABSTRACT FROM AUTHOR]

Earthquake-triggered mudflows are typical in scale and hazard, and their formation mechanism is extremely complex. In this study, the liquefaction and mobility mechanisms of a catastrophic mudflow, namely, the Yongguangcun (YGC) mudflow, in Minxian, Gansu Province, China, under the coupled action of historical earthquakes, active faults, groundwater, long-term rainfall before an earthquake, and the 2013 Mw6.6 Minxian–Zhangxian earthquake were systematically analyzed. Through a detailed field investigation and laboratory testing, the stratigraphic structure of the YGC mudflow was revealed, a geomechanical model was established, and the complex chain process leading to the formation of the YGC mudflow was elucidated. This process includes sliding along the contact zone between the loess and strongly weathered mudstone, liquefaction of the saturated loess under the groundwater table, and liquefaction and collapse of the unsaturated loess above the groundwater table. The slightly low terrain provides the topographic conditions required for groundwater convergence, and sets the conditions for the deformation and further liquefaction of saturated loess during earthquakes. The undulating terrain in the meizoseismal area enhances the complexity of the earthquake waves. In summary, the YGC mudflow was caused by long-term geological evolution and the synergistic effects of other factors; and the site conditions, such as the local topography and groundwater, are the fundamental reasons for the failure and mobility differences between the YGC mudflow and the eastern landslide. The results of the investigation of this mudflow would enrich our understanding of mudflows, promote research on the formation mechanism of geological disasters under complex conditions on the Loess Plateau, and provide important information for improving the scientific prevention and control of landslides of the same type. [ABSTRACT FROM AUTHOR]

The mud undrained shear strength and viscosity are the essential parameters in understanding the behavior of mudflow. One of the laboratory test methods to estimate the undrained shear strength and viscosity is Vallejo and Scovazzo's cylinder strength meter test (CSMT) and flume channel test, respectively. This paper compares the undrained shear strength of kaolin and bentonite muds obtained from the CMST to those obtained using the fall cone and mini vane shear tests and also studies the scale effects in the flume channel test in measuring the mud viscosity at a 20o to 40o slope angles and at various liquidity indexes. The results exhibit that CMST could estimate the undrained strength of mud as low as 0.45 kN/m2 with a liquidity index of up to 5.93. Then, the reduction of the size of the flume channel by half resulted in a mud viscosity of about 2.3 times higher. [ABSTRACT FROM AUTHOR]

The paper presents particular issues of mudflow dynamics, one of the hazardous natural disasters, namely the theoretical study of the flow power during mudflow movement in the wave regime taking into account its rheological properties. The paper discusses the physical process of mudflow mass impetus accumulated in erosion banks, taking into account the impact of the tense state of the eroded mass, in particular, similar to soil mechanics problems, the density of the mudflow-forming mass (ρ), the free fall acceleration (g), angle of internal friction (φ), the adhesive force (Pe), the height equivalent to pressure (h′), the height of the mudflow-forming mass (H), the intensity of transverse pressure (P), and the value of the active pressure of the inertial mass cohesion (C) on the deformation mode of the mudflow mass. On the basis of the basic equations of mudflow dynamics and theoretical studies, an equation is obtained to calculate the values of flow power when mudflows move in the wave mode, taking into account the main rheological properties of a mudflow mass.

Purpose: to make a semi-quantitative assessment of mudflow risk based on empirical data on mudflows and the consequences of their collapse, obtained during the work at the construction and reconstruction of the Lgovskoe – Grushevka – Sudak highway on the territory of the Republic of Crimea and to develop recommendations on state stabilization, based on the assessment results. Materials and methods. The initial data on mudflows are divided into three groups, for each a step-by-step calculation was performed and points were assigned. The criteria by which the assessment has been made: the level of mudflow hazard and the amount of damage, the dependence of the amount of damage on the protective structures’ state. Calculated indicators such as mudflow velocity, flow rate, etc. have also been determined. Each group is assigned a mudflow risk category based on the results of scoring, taking into account their significance. Results. According to the results of the study, the total score for the third group is 15.18, which corresponds to the second category of mudflow risk, which is characterized by a high probability of significant damage. For the first and second groups, the total score is 9.88 and 11.34, respectively, thus, both groups fall within the boundaries of the third category of mudflow hazard. Conclusions. A semi-quantitative assessment of mudflow risk allows identifying potentially dangerous areas, informing on the threat and taking measures for land protection in advance. In order to protect lands from the destructive power of mudflows within the boundaries of the basins of the third group, it is necessary to erect mudflow protection structures, namely: agroforestry-reclamation erosion protection structures, mudflow retention, mudflow passage, mudflow-preventing structures and other engineering protection facilities of the territory.

The factors influencing the formation of mudflows in areas of the permafrost are considered. The data of studies performed in two regions of Chukotka – “Continental” (the Anyuysky ridge) and “Coastal” (the Iskaten ridge) were used for this research. The air temperature data series obtained in Chukotka in 2000–2020 demonstrate a steady growth of the average annual values. The air temperature rise estimated for the mudflow–dangerous period (June–August) amounted 1.4°C for the “Continental” area, and 1.0°C for the “Coastal”. This warming affects thickness of the seasonal melt layer of permafrost, mainly in the bottoms of valleys and on the slopes of mountains. This factor promotes the involvement of certain volumes of ground into mudflows. As a result of the research, it was found that the dynamics of the change in the thickness of the seasonal melt layer within the studied areas is positive, which is a consequence of warming and leads to additional moistening of grounds. The two periods of the mudflow formation were identified. During the first one (May–June), the mudflow formation is connected with the onset of intensive snowmelt that is favorable mainly for snow-water streams and loose mudflows. In the second period (July–August), mudflows are mostly caused by liquid precipitations, when the maximum thickness of seasonal melt layer is reached. It is the second period when a release of a large cohesive mud stream is the most probable. On the whole, the results obtained allow making a conclusion that in the near future the predominant type of mudflows in Chukotka will remain those of snow genesis. But, at the same time, under conditions of the climate change, occurrence of the snow-water mud streams will increase, especially in the “Coastal” area.

Purpose: to explore the territory of the alpine-climatic resort “Alpika-Service” in the North-Western Caucasus near the village of Esto-Sadok, Krasnopolyansky settlement district of Adler region of Sochi in field conditions for dangerous geological processes; on the basis of the conducted field survey of the territory, to determine the zones of mudflow accumulation, to assess the state of the existing mudflow protection structures; to make the necessary calculations of the mudflow in the program for designing flexible engineering protection systems DEBFLOW and to propose measures to stabilize the situation on this basis. Methods and materials. In the course of research, the types of mudflow protection structures were described, it was determined that, according to climatic zoning, the site belongs to subarea III B1. The morphometric parameters of mudflows were determined by sampling and field surveys. On the basis of the DEBFLOW software, the calculation of the load on each designed barrier was carried out. Results: three mudflow basins were found on the territory of the facility, which, during prolonged heavy rains and snowmelt, form mudflows causing damage to Olympic infrastructure facilities, including the Aibga-2 cable car and engineering protection facilities, a technological road, an antenna-mast building no. 2, a pedestrian crossing of the Alpika-Service alpine-climatic resort. Conclusions. On the basis of field surveys, it was determined that the existing mudflow protection facilities are not enough to ensure the complete safety of the Olympic facilities and adjacent buildings. According to the calculations, the recommendations to stabilize the situation, namely along the Sulimovsky stream were given: installation of flexible mudflow protection barriers, placement of a network of catch drains and implementation of erosion-control measures.

High-localition loess landslide has the characteristics of high potential energy, suddenness, concealment, rapid sliding speed, wide threat range, and strong destructive impact capacity. The main forms of damage are destruction and burial, making them a difficult problem for disaster prevention, reduction, and engineering governance in loess areas. Different landform types, stratum lithology, hydrogeological conditions and tectonics have essential differences in landslide formation. Based on typical examples of high-altitude loess landslides in Renda Town, Jingning County, Pingliang City and Dagou, Maiji District, Tianshui City, a systematic study was conducted through technical means such as engineering geological mapping, engineering geological exploration, and high-precision drone aerial surveys from the aspects of spatial distribution, landslide characteristics, causes, motion mechanisms, and disaster characteristics. The results showed that according to the classification of terrain and topography, high-localition loess landslide can be divided into slope type and valley type. Among them, the landslide in Renda Town, Jingning County, Pingliang City belongs to the slope type, moving in the form of “soil waves” , with the same periodicity and continuity as the landslide initiation in terms of movement time. The movement speed is rapid, and the movement sequence is as follows: the sliding body separates from the parent body, the soil slides, and the soil accumulates. The Dagou in Maiji District, Tianshui City belongs to a valley type and moves in the form of mud flow. The sliding of landslides and the initiation of accumulation bodies have a certain lag in time, and the speed is relatively slow compared to the former. The movement sequence is as follows: the sliding body separates from the parent body → soil accumulation → soil sliding → sedimentation, and its movement and accumulation characteristics are basically similar to those of viscous debris flows.

The mineral and granulometric composition and some physical and physicochemical parameters of soils identified during laboratory studies allowed us to reveal the peculiarities of soils of the Chukotka mudflows. The influence of these peculiarities on the formation of a mudflow suspension, which is a transporting mudflow substance, is estimated. The structural–rheological model of movement for the reviewed territory implies the formation of mostly cohesionless mudflows, the main water part of which is free. The laboratory studies, however, showed the presence of a significant amount of finely dispersed aggregated particles in the mudflow matrix, which saturate the water flow with a clay suspension in case of flooding, which allows us to classify these flows as cohesive. The cohesion of the mudflow mass during the movement is acquired due to the decomposition of aggregates leading to a change in physical characteristics of the mudflow. [ABSTRACT FROM AUTHOR]

The difficulty in determining the rheological characteristics of tailings inside reservoirs as well as their intrinsic variability adds uncertainty to tailings dam failures in flood studies. Uncertainty propagation in non-Newtonian hydrodynamic models stands as a great scientific challenge. This article explores the sensibility of tailings dam breach flood mapping to rheological parameters in Bingham and Herschel-Bulkley (H-B) models. The developed approach was based on the probabilistic Latin Hypercube Sampling of rheological parameters. It was automated to propagate uncertainty throughout multiple hydrodynamic simulations using the HEC-RAS v.6.1 software. Rheological parameter ranges and distributions were based on a broad bibliographic review. Bingham models were revealed to be more sensitive than H-B in terms of simulated min-max area values: for Bingham, flood areas, maximum depths, and arrival times varied by 17.9%, 9.3%, and 8.2%, respectively; for H-B, variations were 25.7%, 5.1%, and 3.9%. However, Bingham was less sensitive in terms of hydrodynamically associated probability: high probability ratios were related to a small range of simulated areas in Bingham, while H-B presented great variability. Finally, for each model, the parameters that affect uncertainty the most were identified, reinforcing the importance of determining them properly. Furthermore, the identified parameter ranges for both models should be valuable for defining variable value boundaries for flood sensitivity tests on specific tailings materials for other case studies. The automated algorithm can be used or adapted for specific tests with other hydrodynamic simulations. [ABSTRACT FROM AUTHOR]

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A soil depleted of its organic carbon content is typically destabilized, i.e., its capacity to maintain its microstructure intact under various stress conditions weakens, and consequently, landslides and mudflows can be triggered and propagated more easily. In a previous work, we showed with a rheological analysis that the removal of the sole water-soluble organic carbon "destabilized" the slurry very similarly to what occurs with the removal of the vast majority of soil organic carbon. In principle, the water-soluble organic carbon can be dissolved by rainfall, during which water can infiltrate the soil, eventually leaving it either by percolation or evaporation. These two processes are mimicked here with two different soil water wetting procedures. The stability of the treated (wetted) soils is studied with rheological and granulometric experiments. The former run on concentrated suspensions, while the latter run on very diluted ones. Despite this, the results agreed very well, indicating that the two wetting procedures induce the same destabilization of the soil which behaves as the one depleted by the whole water-soluble organic carbon. Our results concluded that a soil destabilized by a wetting procedure, i.e., by a rainfall event, will be more prone to trigger a landslide that will propagate more swiftly and will stop with more difficulties. [ABSTRACT FROM AUTHOR]

Gravity-driven mass flows are typically large-scale complex multi-phase phenomena involving multiple interacting phases. Various types of mass flows usually exhibit distinct behaviors in their formation, propagation and deposition. In such large-scale geological systems, many uncertainties may arise from the variations in material composition and phase behavior. The present study aims to investigate the important characteristics of some common types of mass flows including debris flows, mudflows and earth flows, based on a recently developed multi-phase computational framework, r.avaflow for flow simulation. Fractions of different phases are varied to reflect different characteristics of material composition of various mass flows and simulate the resulting flow behavior. The evolution of the critical entities during the flow motion, such as velocity, peak discharge, flow height, kinetic energy, run-out distance and deposition is examined; considerable differences among various flows are identified and discussed. Overall, the simulated mudflow cases develop higher velocity, peak discharge, kinetic energy, and longer run-out distance than the debris flow cases. The fluid fraction has a significant influence on the flow dynamics; a higher fluid fraction often leads to higher velocities and long run-out distances, but lower kinetic energy, and it also affects the final deposition and deposition pattern considerably. The present study shows promising potential of a quantitative approach to the physics and mechanics of mass flows that may assist in the risk assessment of such large-scale destructive geological hazards or disasters.

Problem statement. The increased human pressure on natural geo-complexes is causing the revival of undesirable processes that create an extensive risk for the inhabitants of these regions. Alpine-type orogenic zones, which belong to the northeastern slope of the Greater Caucasus, are distinguished from many geomorphological systems by excessive activity of endo- and exogenous processes. Therefore, at this time, the task of diagnosing and assessing the ecological and geomorphological risk that the population faces in the development of new territories of the region seems to be important. Analysis of recent research and publications. After analyzing a number of techniques used to assess the landslide and mudflow hazards, the conclusion was made that most of them had their flaws. Research method. There are a large number of methods for assessing the risk of environmental management and predicting hazardous exodynamic processes. However, in modern conditions, these techniques are not sufficiently reliable. This, in turn, determines the relevance and the need to develop new or modernised methods of strategies for the prevention, protection, and elimination of the consequences of catastrophes and natural disasters. The purpose of this work is to reveal the geomorphological features and dynamics of the development of the most dangerous and often repeating landslide and mudflow processes based on field geomorphological studies, as well as fund literature, indicate the reasons for their formation and propose measures to combat them. Research results. The article discusses the results of ecological and geomorphological surveys on the northeastern slope of the Greater Caucasus, dedicated to the assessment of landslide and mudflow risk for the period from 1990 to 2020. To assess them in order to obtain morphometric characteristics (including the down gradient of slopes, the length and shape of slopes, areas of mudflow centers), large-scale (M 1:100000) topographic maps were used, as well as interpretation materials for different-scale and multi-temporal ASP. Based on the interpretation of the ASP within the studied region, in order to clarify the general picture of the dissection of the modern relief of the studied region, a map of morphometric tension was compiled, which includes the degree of vertical dissection of the territory, the down gradient of slopes, etc., and also maps of the risk of landslides and mudflows were compiled according to the degree of danger of landslide and mudflow processes, and the area of their distribution was calculated. Landslide and mudflow risk analysis mainly used high-resolution aerospace imagery (ASI) from CNES / Airbus, Maxar Technologies (GeoEye-1), and medium resolution Sentinel-2A and 2B. Thus visual and semi-automatic interpretation (classification with training) was performed in the ArcGIS environment. As a result, taking into account the morphometric tension, as well as the mudflow and landslide hazards, a map of the morphodynamic tension of the northeastern slope of the Greater Caucasus was compiled, which makes it possible to reveal the modern nature of the manifestation of exodynamic processes, to predict and assess the risk coming from them. Conclusion. The results of the research will make it possible to use the obtained data for the development of the Program for the safe and sustainable functioning and development for the purpose of recreational and tourist development of the difficult of access mountain geosystems of Azerbaijan.

Sediment related disaster is the most significant natural disaster in Malaysia and many countries in this world from the perspective of magnitude, damage and loss to human life and infrastructure as well as disruption to socio-economic activities. Debris, mud flood, landslide and cliff failure are some of the major catastrophic problems and became a history for the country especially Cameron Highlands in a state of Pahang. As rainfall is the main culprit to sediment-related disaster occurrences, therefore the rainfall data is very crucial to be used in the correlation of the occurred events. Due to that fact, several studies worldwide have been made to estimate critical rainfall conditions and this being useful to draw the benchmark to predict the occurrences of the landslide specifically for DMF and shallow landslides. This paper discussed the development of the rainfall threshold in Malaysia by compiling the framework of the threshold to determine the lesson learned as well as the way forward. As Malaysia needs to move at a faster pace towards embracing the whole aspects in determining the threshold as well to implement it into the operational threshold, therefore the first step is very important to initiate the momentum while the collaboration or networking among government agencies in National Disaster Risk Reduction (DDR) should be enhanced and strengthened.

The alleviation of landslide impacts is a priority since they have the potential to cause significant economic damage as well as the loss of human life. Mitigation can be achieved effectively by using warning systems and preventive measures. The development of improved methodologies for the analysis and understanding of landslides is at the forefront of this scientific field. Identifying effective monitoring techniques (accurate, fast, and low cost) is the pursued objective. Geographic Information Systems (GISs) and remote sensing techniques are utilized in order to achieve this goal. In this study, four methodological approaches (manual landslide delineation, a segmentation process, and two mapping models, specifically object-based image analysis and pixel-based image analysis (OBIA and PBIA)) were proposed and tested with the use of Unmanned Aerial Vehicles (UAVs) and data analysis methods to showcase the state and evolution of landslides. The digital surface model (DSM)-based classification approach was also used to support the aforementioned approaches. This study focused on streamside landslides at research sites in three different countries: Greece, Romania, and Turkey. The results highlight that the areas of the OBIA-based classifications were the most similar (98%) to our control (manual) classifications for all three sites. The landslides' perimeters at the Lefkothea and Chirlesti sites showed similar results to the OBIA-based classification (93%), as opposed to the Sirtoba site, where the perimeters of the landslides from OBIA-based classification were not well corroborated by the perimeters in the manual classification. Deposition areas that extend beyond the trees were revealed by the DSM-based classification. The results are encouraging because the methodology can be used to monitor landslide evolution with accuracy and high performance in different regions. Specifically, terrains that are difficult to access can be surveyed by UAVs because of their ability to take aerial images. The obtained results provide a framework for the unitary analysis of landslides using modern techniques and tools. [ABSTRACT FROM AUTHOR]

Flow-like landslides are a serious geologic hazard that can cause life and property loss all over the world. Mudflow is a kind of debris flow that has been classified as a non-Newtonian flow. The Smoothed particle hydrodynamics method (SPH) is a powerful tool for modeling fluids, such as debris/mudflows, which can be described in terms of local interactions of their constituent parts. In this paper, the Herschel-Buckley rheology model and SPH are used to simulate free-surface mudflow under the gate. The run-out distance and velocity of mudflow during the time are calculated with numerical simulation and compared with the laboratory result. Our results indicate the rate of increase of run-out and viscosity in the computer model is more than the experimental model and it is because of friction that is assumed to be zero. In the computer simulation, friction is exactly zero but in the experimental model, it could be measured and assumed zero. Finally, Abacus had a good result and can be used for mudflow simulation and protection of run-out distance and viscosity. [ABSTRACT FROM AUTHOR]

Sediment-related disaster is one of the most significant natural disasters, from the perspective of magnitude, damage and loss to human life and infrastructure, and disruption to socio-economic activities. Debris, mud flood, landslide and cliff failure are the major catastrophic problems commonly experienced in most developing countries, including Malaysia. As rainfall is the main culprit to sediment-related disaster occurrences, rainfall data are crucial in the correlation of the occurred events. Several studies have been undertaken worldwide to estimate the critical rainfall conditions and draw the benchmark to predict landslide occurrences, specifically for debris and mudflows (DMF), and shallow landslides. Therefore, this paper presents an up-to-date picture on the development of the rainfall threshold from Malaysia's perspective. Additionally, the open issues and challenges of deriving the rain threshold are also discussed in three aspects: collection of the dataset features, identification of the threshold and validation of the threshold. The outcomes of this review could serve as references for future studies in Malaysia and other developing countries in managing sediment-related disasters. [ABSTRACT FROM AUTHOR]

Gravity-driven mass flows are typically large-scale complex multi-phase phenomena involving multiple interacting phases. Various types of mass flows usually exhibit distinct behaviors in their formation, propagation and deposition. In such large-scale geological systems, many uncertainties may arise from the variations in material composition and phase behavior. The present study aims to investigate the important characteristics of some common types of mass flows including debris flows, mudflows and earth flows, based on a recently developed multi-phase computational framework, r.avaflow for flow simulation. Fractions of different phases are varied to reflect different characteristics of material composition of various mass flows and simulate the resulting flow behavior. The evolution of the critical entities during the flow motion, such as velocity, peak discharge, flow height, kinetic energy, run-out distance and deposition is examined; considerable differences among various flows are identified and discussed. Overall, the simulated mudflow cases develop higher velocity, peak discharge, kinetic energy, and longer run-out distance than the debris flow cases. The fluid fraction has a significant influence on the flow dynamics; a higher fluid fraction often leads to higher velocities and long run-out distances, but lower kinetic energy, and it also affects the final deposition and deposition pattern considerably. The present study shows promising potential of a quantitative approach to the physics and mechanics of mass flows that may assist in the risk assessment of such large-scale destructive geological hazards or disasters. [ABSTRACT FROM AUTHOR]

Abstract The 7.5 M w tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction, triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. This study focuses on the generating factors of liquefaction such as the condition of soil lithology, depth of water table, the distance to the focal mechanism, and the thickness of soft sediment. Microtremor data, including the Horizontal Vertical Spectral Ratio (HVSR), geological condition, and borehole data, were examined to conduct the liquefaction analysis. The analysis results based on the microtremor data showed that the distribution of ground shear strain values in Palu City ranged from 0.75 × 10–4 to 2.56 × 10–4. The distribution of the locations of the liquefaction was correlated to the distribution of ground shear strain values. High ground shear strain values and a shallow groundwater level were discovered in Palu City valley, which indicates that liquefaction in Palu City will undoubtedly occur. The semi-empirical method confirmed that Balaroa, Petobo, and Jono Oge had undergone large-scale liquefaction at a maximum depth of 16 m below the ground level. The average peak of water runoff that generated the mudflow was estimated to be at 11.31 cm3/s. Since the soil has loose soil grain with high water content, the soil will turn into a massive amount of mud during the liquefaction.

Mudflows from the ongoing eruption of a mud volcano near Sidoarjo (East Java, Indonesia) have continued for more than 15 years and now cover an area of 8.2 km2 to a depth of more than 15 m. The mudflows are contained within a system of perimeter earthen levees/dykes that were constructed as a series of temporary defenses. The levees have marginal stability and limited freeboard due to the low shear strength and high compressibility of the 25-m-deep soft clay foundations, which have already resulted in ground deformations exceeding 7 m. In this paper, we analyze the deformations and stability of the downstream staged construction at a critical reach in order to (1) understand causes of a recent failure (2018); and (2) assess the current state of the levee following completion of a fifth construction stage (2019) that included a 35-m-wide, 4-m-high stabilization berm with an array of prefabricated vertical drains (PVDs) to accelerate consolidation. Our analyses used large-deformation elastoplastic finite-element analyses to simulate consolidation and lateral spreading of the foundation soils due to levee construction and mudflow loads. Levee stability was evaluated using numerical limit analyses for the deformed geometry and simulating changes in undrained strength with the consolidation state and direction of shearing at each stage of construction. The results were consistent with the magnitudes of the observed levee settlements and mechanism of failure; they also show the potential for an additional >2 m settlement over the next 5 years, even without considering creep of the clay or larger-scale processes controlling subsidence around the volcanic caldera. Future construction stages to contain the expected mudflow will require improvement of the mechanical properties of the alluvial clay to ensure adequate long-term freeboard. [ABSTRACT FROM AUTHOR]

The Santa Barbara post-wildfire debris flows and the Brumadinho tailing-dam failure were two of the most catastrophic flood events of the late 2010s. Both these events carried so much solid-phase material, that classic, clear-water, flood risk approaches cannot replicate them, or forecast other events like them. This case study applied the new non-Newtonian features in HEC-RAS 6.1 to these two events, testing the most widely used flood risk model on the two most common mud and debris flow hazards (post-wildfire floods and mine tailing dam failures). HEC-RAS reproduced the inundation boundaries and the event timing (where available) for both events. The ratio between the largest debris flow clasts and the channel size, parametric trade-offs, the "convex" alluvial plain topography, and the stochasticity introduced by urban infrastructure made the Santa Barbara modeling more difficult and less precise than Brumadinho. Despite these challenges, the results provide prototype scale validation and verification of these new tools in this widely applied flood risk model. [ABSTRACT FROM AUTHOR]

We calibrate the k- ω S S T turbulence model for free surface flows in the channel or on the slope using machine learning techniques. To calibrate the turbulence model, an experiment is carried out in an inclined rectangular research chute. In the experiment, the pressure values in the flow are measured at different distances from the bottom; after transforming data, the flow velocity profile is obtained. The k- ω S S T turbulence model is calibrated based on experimental data using the Nelder-Mead optimization algorithm. The calibrated turbulence model is then used to calculate the glacial lake Maliy Azau outburst flood on the Elbrus (Central Caucasus). [ABSTRACT FROM AUTHOR]

The Azerbaijani part of the Greater Caucasus consists of mountain ranges, mountainous depressions and sloppy plains. Different types of relief forms and landscapes have been formed during the repetition of endogenous and exogenous processes that have emerged as a result of the mutual influence of internal and external forces on the relief. The factors which influence the southern slope geosystems of the Greater Caucasus were first studied by us. Landscape-ecological assessment of the area was carried out using suitable, satisfactory, tense, crisis-critical and standard criteria, and a landscape map was compiled on its basis. The materials include the steppe expedition data. The applied methods are landscape-geomorphological, historical, comparative, mathematical-statistical, cartographic. Resistance of natural landscapes to anthropogenic influences is determined.

China–Nepal Highway is an important international passage connecting China and Nepal. Owing to its location in a complex mountainous area in the Qinghai– Tibet Plateau, the Shigatse section of the China–Nepal Highway is often impacted and troubled by mudflow. In order to effectively conduct road construction and maintenance and improve early disaster-warning capability, the relationship between various hazard factors and disaster points was analysed. It is found that four factors such as slope, precipitation, soil type and digital elevation have the strongest correlation with the occurrence of the disasters. From the distribution of disaster points, it is observed that the disaster point is closely related to the slope, its local correlation with precipitation is good and the its local correlation with the soil type and Digital Elevation Model (DEM) data is significant. In order to quantitatively evaluate the susceptibility of mudflow disasters in the Shigatse region, this paper uses the analytic hierarchy process (AHP) as the main analysis method supplemented by the fuzzy clustering method. The results show that the slope, when accompanied by heavy rainfall, is the most important factor among four factors. In this paper, the neural network method is used to establish the identification and early warning model of mudflow susceptibility. When the recognition rate reaches 66% or above, it can be used as an early-warning threshold for mudflow disasters. This study has conducted a useful exploration of the research, assessment and early warning of mudflow disasters along the Shigatse section of the China–Nepal Highway.

The conservation of water resources in developed countries has become an increasing concern. In integrated water resource management, water quality indicators are critical. The low groundwater quality quantitates mainly attributed to the absence of protection systems for polluted streams that collect and recycle the untreated wastewater. Egypt has a limited river network; thus, the supply of water resources remains inadequate to satisfy domestic demand. In this regard, high-quality groundwater is one of the main strategies for saving water supplies with water shortage problems. This paper investigates the critical issues of groundwater protection and environmental management of polluted streams, leading to overcoming water demand-about 18 × 103 km of polluted open streams with a discharge of 9.70 billion Cubic Metter (BCM). We have proposed proposals and policies for the safe use of groundwater and reuse of wastewater recycling for agriculture and other purposes. This study was carried out using the numerical model MODFLOW and MT3DMS—(Mass Transport 3-Dimension Multi-Species) to assess the Wastewater Treated Plant's (WWTP) best location and the critical path for using different lining materials of polluted streams to avoid groundwater contamination. The three contaminants are BOD, COD, and TDS. Five scenarios were applied for mitigating the impact of polluted water: (1) abstraction forcing, (2) installing the WWTP at the outlet of the main basin drain with and without a lining of main and sub-basin streams (base case), (3) lining of main and sub-main streams, (4) installing WWTP at the outlet of the sub-basin streams, and (5) lining of the sub-basin and installing WWTP at the outlet of the sub-basin. The results showed that the best location of WWTP in polluted streams is developed at the outlets of sub-basin with the treatment of main basin water and the lining of sub-basins streams. The contamination was reduced by 76.07, 76.38, and 75.67% for BOD, COD, and TDS, respectively, using Cascade Aeration Biofilter or Trickling Filter, Enhancing Solar water Disinfection [(CABFESD)/(CATFESD)] and High-Density Polyethylene lining. This method is highly effective and safe for groundwater and surface water environmental protection. This study could be managing the water poverty for polluted streams and groundwater in the Global South and satisfy the environmental issues to improve water quality and reduce the treatment and health cost in these regions. [ABSTRACT FROM AUTHOR]

The Maebashi volcanic mudflow deposits constitute major basement strata in the Maebashi-Takasaki area, central Japan. Sr isotope analysis of large volcanic blocks and 14C dating of buried wood blocks elucidated that the volcanic mudflow originated from a failure event of Kurofu volcano, an initial stage volcanic edifice of Asama volcano located about 50km west of these cities, which occurred ca.27 ka cal BP within the last glacial period. However, the cause of sector collapse and mechanism of long-distance movement of volcanic blocks are unknown. In order to get some clues for these problems, we studied the mode of occurrence of volcanic blocks and their specific gravity and Sr isotope ratio（87Sr/86Sr）, which are sparsely remained along the route of the Maebashi mudflow from the northern foot of Asama volcano to the Maebashi-Takasaki area through the Agatsuma and Tone Rivers. Here, we report the results for 13 volcanic rocks from a hummocky hill near Asama volcano, large blocks near the Agatsuma River and small blocks within the Maebashi mudflow deposit. All of them, except one sample, yielded narrow range Sr isotope ratios（0.70394-0.70416; av.：0.70406 ± 0.00001）close to the published data for Asama volcano. A large block transported by the Tenmei mudflow caused by the eruption of Asama volcano in 1783 was confirmed to have the same isotope ratio as above values. The two large blocks similar to Iwagami-no-Tobi-ishi, a representative large block related to the Maebashi mudflow, occur on the slopes 30-50m above present riverbed of the Agatsuma River, suggesting the devastating volume of the mudflow which transported these blocks. An exceptional case on the riverbed of the Tone River in the foot of Akagi volcano was interpreted as a block originated from the eroded hummocky hill from Akagi volcano. [ABSTRACT FROM AUTHOR]

Thick volcanic mudflow deposits originated from the sector collapse of Kurofu volcano, an initial stage volcanic edifice of Asama volcano in central Japan, are distributed in the Maebashi-Takasaki area of Gunma Prefecture and Saku-Karuizawa area of Nagano Prefecture. Preliminary 14C age dating of wood blocks found in these mudflow deposits yielded ca.27 ka cal BP and older ages of more than 10 ka y. The dominant ages around ca.27 ka cal BP may represent the main collapse event, while the older ages may also suggest preceding collapse or slope failure events although its scale is unknown. In order to get some more insights into the failure events in Kurofu volcano, we focused our additional 14C study on the Saku-Karuizawa areas where age data are insufficient. Two wood blocks found in the Tsukahara mudflow deposits in the Saku area yielded nearly identical ages with the dominant ages of ca.27 ka cal BP, confirming the age of the sector collapse. The erratic ages older than ca.27 ka cal BP are interpreted to represent a scenario that local-scale mudflows involved trees in the foot of Kurofu volcano and the buried wood blocks were incorporated into the mudflow caused by the main collapse event. A younger age of ca.17 ka cal BP was obtained for a specimen from a group of wood blocks which coexists with pumice blocks within a silt bed overlying the Tsukahara mudflow deposits. This age is correlated with a large pumice eruption event that occurred in an intermediate stage activity of Asama volcano. [ABSTRACT FROM AUTHOR]

Problem statement. The increased human pressure on natural geo-complexes is causing the revival of undesirable processes that create an extensive risk for the inhabitants of these regions. Alpine-type orogenic zones, which belong to the northeastern slope of the Greater Caucasus, are distinguished from many geomorphological systems by excessive activity of endo- and exogenous processes. Therefore, at this time, the task of diagnosing and assessing the ecological and geomorphological risk that the population faces in the development of new territories of the region seems to be important. Analysis of recent research and publications. After analyzing a number of techniques used to assess the landslide and mudflow hazards, the conclusion was made that most of them had their flaws. Research method. There are a large number of methods for assessing the risk of environmental management and predicting hazardous exodynamic processes. However, in modern conditions, these techniques are not sufficiently reliable. This, in turn, determines the relevance and the need to develop new or modernised methods of strategies for the prevention, protection, and elimination of the consequences of catastrophes and natural disasters. The purpose of this work is to reveal the geomorphological features and dynamics of the development of the most dangerous and often repeating landslide and mudflow processes based on field geomorphological studies, as well as fund literature, indicate the reasons for their formation and propose measures to combat them. Research results. The article discusses the results of ecological and geomorphological surveys on the northeastern slope of the Greater Caucasus, dedicated to the assessment of landslide and mudflow risk for the period from 1990 to 2020. To assess them in order to obtain morphometric characteristics (including the down gradient of slopes, the length and shape of slopes, areas of mudflow centers), large-scale (M 1:100000) topographic maps were used, as well as interpretation materials for different-scale and multi-temporal ASP. Based on the interpretation of the ASP within the studied region, in order to clarify the general picture of the dissection of the modern relief of the studied region, a map of morphometric tension was compiled, which includes the degree of vertical dissection of the territory, the down gradient of slopes, etc., and also maps of the risk of landslides and mudflows were compiled according to the degree of danger of landslide and mudflow processes, and the area of their distribution was calculated. Landslide and mudflow risk analysis mainly used high-resolution aerospace imagery (ASI) from CNES / Airbus, Maxar Technologies (GeoEye-1), and medium resolution Sentinel-2A and 2B. Thus visual and semi-automatic interpretation (classification with training) was performed in the ArcGIS environment. As a result, taking into account the morphometric tension, as well as the mudflow and landslide hazards, a map of the morphodynamic tension of the northeastern slope of the Greater Caucasus was compiled, which makes it possible to reveal the modern nature of the manifestation of exodynamic processes, to predict and assess the risk coming from them. Conclusion. The results of the research will make it possible to use the obtained data for the development of the Program for the safe and sustainable functioning and development for the purpose of recreational and tourist development of the difficult of access mountain geosystems of Azerbaijan. [ABSTRACT FROM AUTHOR]

Flow-like landslides are a serious geologic hazard that can cause life and property loss all over the world. Mudflow is a kind of debris flow that has been classified as a non-Newtonian flow. The Smoothed particle hydrodynamics method (SPH) is a powerful tool for modeling fluids, such as debris/mudflows, which can be described in terms of local interactions of their constituent parts. In this paper, the Herschel-Buckley rheology model and SPH are used to simulate free-surface mudflow under the gate. The run-out distance and velocity of mudflow during the time are calculated with numerical simulation and compared with the laboratory result. Our results indicate the rate of increase of run-out and viscosity in the computer model is more than the experimental model and it is because of friction that is assumed to be zero. In the computer simulation, friction is exactly zero but in the experimental model, it could be measured and assumed zero. Finally, Abacus had a good result and can be used for mudflow simulation and protection of run-out distance and viscosity. [ABSTRACT FROM AUTHOR]

The relevance of the research is caused by the need to ensure the safety of construction and operation of the facilities of the Sport and Tourism Complex «Gorny vozdukh» in Yuzhno-Sakhalinsk. The aim of the research is to detect the signs of activation of exogenous geological processes while constructing the facilities of the Sport and Tourism Complex «Gorny vozdukh», to assess their danger and study their influence on water bodies. Objects: the territory under cable cars, ski slopes, buildings and constructions of the infrastructure and technological roads on the northern and southern slopes of Bolshevik, reservoir on the river Rogatka, water intake on the river Yelanka. Methods: study of the results of engineering surveys carried out by various organizations on the slopes of Bolshevik Mountain; investigation of the operation mode of water intakes on the Yelanka and Rogatka rivers; field survey of the facilities of the Sport and Tourism Complex «Gorny vozdukh» on the slopes of Bolshevik; sampling of water from water bodies for chemical analyzes. Results. In the territories under cableways and newly built ski slopes, bare ground is observed, in places up to the zone of exogenous fissuring and bedrock. In cable trenches there are insignificant drawdowns of bulk ground, caused by gravity densification and suffosion processes. Traces of water erosion are noted. There are no signs of landslide and mudflow activity. Brooks flowing down the slopes are transparent. Construction works in the valley of the Yelanka River affect only the duration of breaks in the operation of the water intake. The influence of the Sport and Tourism Complex construction on water quality in the reservoir on the river Rogatka is not established, the operation mode of the water intake in the reservoir has not changed.

In the studied region, vast land areas are influenced by construction and operation of large linear facilities, such as oil-gas pipelines, power lines, motor roads and railways. In the areas along and inside the construction right-of-way zones, considerable changes occur in landscapes, microclimate conditions, hydrological features of water bo­dies, and geological engineering characteristics of the rocks. Furthermore, anthropogenic soil materials are produced. In our study, such materials are termed ‘man-made / technogenic soils’, which means the soil material displaced during stripping operations in the areas allocated for construction of linear objects, and the soil material resulting from coal mining and quarrying. The above-mentioned changes in the geological environment lead to intensive exogenous geodynamic processes (EGP) taking place during construction and in the first years of the object operation. In areas where such objects are located near and in residential areas, the EGP impact is observed in the zones that have been previously not at all influenced or only slightly affected by EGP. In our comprehensive study aimed at the assessment of the scale of the regional landslide and mudflow processes, the physical and chemical properties of technogenic soils were determined, their mineral and chemical composition was analyzed, and the levels of chemical contamination of the studied soils were estimated. The research results can be used in engineering-geological, construction, hydrometeorological surveys, as well as forecasting the development of EGP and their impact on the territory adjacent to the large linear objects.