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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.

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]

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.

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]

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]

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]

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.

The 7.5 Mw 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. [ABSTRACT FROM AUTHOR]

We calibrate the k-ωSST 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-ωSST 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).

The paper presents a description of three Late Pleistocene sections within the Khibiny pluton, outcropping on the proximal slope of the Kukisvum morainic ridge, a fluvioglacial terrain in the valley of the Kukisiok River, and a glacial complex in the valley of the Vuonnemiok River. Various small disturbances of the primary stratification were found in the first two sections. These structures do not form horizons sustained along the strike and are associated with the top of sand-silt sediments with horizontal or wavy bedding of shallow lacustrine genesis. They form small wavy bends, 'tongues", ovoids, and flexural microfolds that could not be preserved at the bottom of the basin and, consequently, formed after overlapping deposits accumulation. Analysis of the cross bedding of the coarse clastic deposits of the fluvioglacial terrace has allowed us to relate its formation to north-to-south glacial water discharge along the trough valley of the Kukisiok River. In the glaciolacustrine varve clays of the third section (the Koashva open pit), extended horizons of plicative disturbances 0.5-2 m in thickness and 300 m in length were studied. The soft-sediment deformations are covered with an unstructured horizon composed of coarse grains dispersed in sand-silt matrix, which means that the deformation was caused by either a glacial flood or a mudflow. The study has revealed no signs of seismic liquefaction during the formation of the folded structures. The relevance of the performed study is determined by the fact that it has become possible not only to clarify the formation conditions of the Quaternary Khibiny deposits but also to develop the objective criteria for determination of the soft-sediment deformation structures associated with thixotropic effects in weakly consolidated sediments. Similar structures are sometimes regarded as seismic convolutions, which can lead to unjustified overestimation of the regional seismic hazard level. [ABSTRACT FROM AUTHOR]

The characteristics of mudflow understood as a two-phase (in certain cases, three-phase) nonuniform, nonsteady motion of a non-Newtonian fluid are considered. An analysis of the dependence of the energy of a mudflow on time is proposed. The viscosity of mudflowis calculated on the basis of experimental data. The role of viscosity of mudflow in the determination of the energy of a two-phase flow is demonstrated. [ABSTRACT FROM AUTHOR]

Prediction of runout distance and deposit morphology is of great importance in hazard mitigation of geophysical flows, including viscoplastic mudflows. The major rheological parameters of mudflows, namely, yield stress and viscosity, are crucial factors in controlling the runout and deposition processes. However, the roles of the two parameters, especially in mudflows with high inertia, remain poorly understood and are not accounted for in runout scaling relations with source volume. Here we investigate the effects of flow rheology on runout scaling and deposit morphology using small‐scale laboratory experiments and three‐dimensional numerical simulations. We find that yield stress and viscosity both influence flow velocity gained during downslope propagation of mudflows, which is strongly correlated with the runout distance; the role of yield stress is more significant than viscosity. High yield stress and low viscosity lead to an elongated deposit, where longitudinal propagation is more significant than lateral spreading. In contrast, high viscosity promotes the dominance of lateral spreading of the deposit, while low yield stress and moderate viscosity produce an initial elongate deposit, followed by a secondary surge that spreads laterally near the head of the deposit. Following appropriate scaling relations for viscosity and yield stress, a general scaling function is proposed to incorporate flow properties in the well‐known correlation of runout distance and source volume. Our findings regarding the inertia effects and the roles of yield stress and viscosity enhance our understanding of mudflows, muddy debris flows, and other viscoplastic geophysical flows. [ABSTRACT FROM AUTHOR]

The paper describes a proposed unified hydro-elasto-plastic model with a solid–fluid transition. The model associates a hydro-elasto-plastic model for partially saturated geomaterials, a Bingham’s viscous law, and the transition criterion between solid and fluid states. The model describes both solid and fluid behaviours of partially saturated geomaterials in a unified framework. In addition, this paper describes a novel Finite Element Method with Lagrangian Integration Points (FEMLIP) formulation for solving hydro-mechanical problems. Based on the equilibrium equation of momentum and the continuity equation of water flow, the formulation was developed and implemented in a FEMLIP tool. Bishop’s effective stress expression and proper water retention diagrams were taken into account. A heuristic column and real rainfall-induced mudflows were also simulated and analysed in this study. The permeability effects of partially saturated soil and the effective cohesion were considered, which included consideration of the entire mudflow process. The results were proven satisfactorily in a qualitative fashion. [ABSTRACT FROM AUTHOR]

As a common problem all over the world, the flow-like landslides have been widely and deeply investigated. Most investigations were performed focusing on the failure mechanisms in the pre-failure stage, and the fast propagations in the post-failure stage, respectively. This study attempted to simulate a real mudflow in a consistent manner, and to describe the initiation, propagation and arrest stages of the disaster using only one constitutive model. A visco-elasto-plastic model with solid-fluid transition was briefly presented and used in the study, and necessary physical parameters were carefully calibrated. Two failure mechanisms induced by increasing gravity and decreasing suction were discussed, and the definition for the interface between viscous and elasto-plastic layers was explained. Finally, the consistent simulation of the mudflow was performed, and the impact effect against a remaining wall was heuristically studied. [ABSTRACT FROM AUTHOR]

The Lajia Ruins in the Guanting Basin, NW China, are a product of the prehistoric Qijia Culture. Like Pompeii, they are a rare example of an archaeological site preserved by a natural disaster and are therefore important in archaeology, anthropology and geology. However, the nature of the disaster(s) responsible for the destruction of the site remains controversial. Most studies have focused on an earthquake and a red clay layer directly overlying the site and a detailed stratigraphic study of the mid-Holocene sedimentary strata combined with other intervals of red clay deposition (hence possible disasters) is lacking. We identified a mid-Holocene paleosol sequence (the Shanglajia section) at the site which contains two layers of red clay, dated to 3950 a BP and 3500 a BP, intercalated within the mid-Holocene paleosol (S 0 ). Subsequent multi-proxy analysis indicated that the characteristics of the two red clay layers resemble those of typical Tertiary red clay deposits and the modern gully deposit at the foot of the Great Red Hills, but are distinctly different from those of the slackwater deposits of the Yellow River and the mid-Holocene paleosol. Our results suggest that, at 3950 a BP and 3500 a BP, two large-scale rainstorm-induced mudflow events, originating from the gullies to the north, flooded the Lajia area on the second terrace of the Yellow River, devastating and burying the human settlements. We infer that the intensified erosion and mass wasting were caused by human activity; in addition, natural factors such as rainstorms and earthquakes, may also have played an important role in triggering catastrophic mudflow events in the Tertiary Red Clay deposits. Overall, our results provide further insights into prehistoric man-land relationships in this environmentally sensitive region which may have implications for modern land use in this region of China and elsewhere. [ABSTRACT FROM AUTHOR]

The total area of debris flow territories of the Russian Federation accounts for about 10% of the area of the country. The highest debris flow activity areas located in Kamchatka-Kuril, North Caucasus and Baikal debris flow provinces. The largest debris flow events connected with volcano eruptions. Maximum volume of debris flow deposits per one event reached 500 × 10 m (lahar formed during the eruption of Bezymyanny volcano in Kamchatka in 1956). In the mountains of the Greater Caucasus, the maximum volume of transported debris material reached 3 × 10 m; the largest debris flows here had glacial reasons. In the Baikal debris flow province, the highest debris flow activity located in the ridges of the Baikal rift zone (the East Sayan Mountains, the Khamar-Daban Ridge and the ridges of the Stanovoye Highland). Spatial features of debris flow processes within the territory of Russia are analyzed, and the map of Debris Flow Hazard in Russia is presented. We classified the debris flow hazard areas into 2 zones, 6 regions and 15 provinces. Warm and cold zones are distinguished. The warm zone covers mountainous areas within the southern part of Russia with temperate climate; rain-induced debris flows are predominant there. The cold zone includes mountainous areas with subarctic and arctic climate; they are characterized by a short warm period, the occurrence of permafrost, as well as the predominance of slush flows. Debris flow events are described for each province. We collected a list of remarkable debris flow events with some parameters of their magnitude and impact. Due to climate change, the characteristics of debris flows will change in the future. Availability of maps and information from previous events will allow to analyze the new cases of debris flows. [ABSTRACT FROM AUTHOR]

Extended horizons of 0.5-2-m-thick soft-sediment deformation structures, which were earlier described as the effects of strong earthquakes in the Late Pleistocene, are studied in glaciolacustrine deposits of the Khibiny massif (central part of the Kola Peninsula). The unstructured horizon of coarse-fragmental inclusions is found everywhere over the folds, which makes it possible to consider these structures as the result of debris flow impact on consolidated bottom sediments probably caused by glacial mudflow. Despite intense and instantaneous crumpling of sediments, no liquefaction or fluidization phenomena typical of seismites are recognized in the deformation structures. Thus, the new data on the genesis of folded horizons in glaciolacustrine sediments in the Khibiny massif does not confirm the high seismic potential of this region. [ABSTRACT FROM AUTHOR]

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An experimental study of the rheological properties of mudflows at Lianyungang in China was carried out by the RS6000 rheometer, including steady and dynamic measurements. Five samples with the range of mud volume concentration from 0.058 to 0.179 were investigated. Based on the experimental data, a Dual-Herschel–Bulkley model was developed to analyze the flow curve and interpolate the static and dynamic yield stresses. The results show that in the steady measurement, the consolidation time and the system temperature show some effects on the rheogram and the yield stress for the sample with low sediment volume concentration, and the effects are strengthened gradually with the sediment volume concentration increasing. Under a shear stress sweep, two linear visco-elastic regions, showing the viscous and the elastic behaviors respectively, were discovered. Complex viscosity, elastic modulus and loss modulus in the elastic region are several orders of magnitude larger than those in the viscous region. Furthermore, the analysis of experimental data show that both steady and dynamic rheological properties can be expressed as appropriate exponential functions of the sediment volume concentration. [ABSTRACT FROM AUTHOR]