Runout Path Research Articles

Analysis of Uncertainty and Sensitivity in Tailings Dam Breach-Runout Numerical Modelling

AbstractTailings dam breaches (TDBs) and subsequent flows can pose significant risk to public safety, the environment, and the economy. Numerical runout models are used to simulate potential tailings flows and understand their downstream impacts. Due to the complex nature of the breach-runout processes, the mobility and downstream impacts of these types of failures are highly uncertain. We applied the first-order second-moment (FOSM) methodology to a database of 11 back-analyzed historical tailings flows to evaluate uncertainties in TDB runout modelling and conducted a sensitivity analysis to identify key factors contributing to the variability of the HEC-RAS model output, including at different locations along the runout path. The results indicate that prioritizing resources toward advancements in estimating the values of primary contributors to the sensitivity of the selected model outputs is necessary for more reliable model results. We found that the total released volume is among the top contributors to the sensitivity of modelled inundation area and maximum flow depth, while surface roughness is among the top contributors to the sensitivity of modelled maximum flow velocity and flow front arrival time. However, the primary contributors to the sensitivity of the model outputs varied depending on the case study; therefore, the selection of appropriate rheological models and consideration of site-specific conditions are crucial for accurate predictions. The study proposes and demonstrates the FOSM methodology as an approximate probabilistic approach to model-based tailings flow runout prediction, which can help improve the accuracy of risk assessments and emergency response plans.

Time-resolved triggering and runout analysis of rainfall-induced shallow landslides

AbstractRainfall-induced shallow landslides often turn into flows. These phenomena occur worldwide and pose severe hazard to infrastructure and human lives on mountainous areas. Risk assessment, and the design of mitigation measures, can both be informed by back-analysis of previous events. However, shallow instabilities are frequently spread over a large area, with the generated flows occurring in sequences, or surges. Conventionally, back-analysis exercises tackle the problem by simulating runout as a single event, with all surges happening simultaneously. This simplification has repercussions that have not been explored in the literature so far, and whose impact in hazard assessment practice is unclear. Therefore, a novel time-resolving procedure is proposed in this paper, which can for the first time be applied to resolve instability sequences of arbitrary duration. The methodology discretizes the event, detecting instabilities at equally spaced time intervals as a function of rainfall. Thanks to this, the post-failure behaviour of each surge can be tracked by a runout model, with a separate simulation performed every time a new instability is detected. The methodology robustness is tested on two documented case studies. The results reveal that, under some conditions, the time-resolving procedure can lead to significantly different results in terms of runout path, flooded area, and flow heights. This leads to criticism on how back-analysis is conventionally applied, prompting for a review of historical cases.

Monitoring and modelling of debris-flow erosion in the Rebaixader catchment (Pyrenees, Spain)

Debris flow and other torrential processes can entrain large volumes of sediments along their runout path. Since the debris-flow hazard strongly depends on the volume, the research on the entrainment is relevant and has been analysed by multiple approaches in the past. In this study, the erosion volume due to torrential processes has been monitored in the Rebaixader catchment (Spain) by digital elevation models obtained from Uncrewed Aerial Vehicle (UAV) surveys and by the instrumental monitoring system installed in the channel reach. In addition, the entrainment of debris flows has been modelled by the numerical code FLATModel. The results of both approaches show that debris flows in the studied catchment are characterised by a large entrainment and the assumption of landslide-triggered debris flows has been refuted. Important erosion in the gullies of the initiation area has been detected by the UAV data and the numerical modelling. An average annual erosion volume of about 6100 m3/y has been determined.

Geological characterization and failure analysis of a catastrophic landslide in volcaniclastic soils: the Banjarnegara–Jemblung Landslide (Indonesia)

The Banjarnegara–Jemblung Landslide was triggered on 12 December 2014 near the village of Jemblung in Central Java (Indonesia). The disaster occurred on the northern slope of Gunung Telagalele and caused more than 100 fatalities, making it the most disastrous landslide to have occurred in Indonesia in the past few decades. The event was characterized by multiple slope failures forming two landslide events A and B, with two connected scarps but two separated runout paths. According to eyewitnesses, landslide A was mobilized only a few minutes after the initial failure of B. Initially, both landslides began as earth slides that developed subsequently into very to extremely rapid earth flows. Although the failure volume was moderate, both slide flows reached very high velocities of several metres per second and travelled long distances, leading to remarkably low travel angles of 14° and 15°. Field investigations confirmed that slope failure was exacerbated by its geological predisposition based on a slope-parallel layering of volcaniclastic sediments of different origin and age, as well as intensive tropical weathering that generated clay-rich soils. Temporal relationships, as well as stability analysis, indicate that antecedent rainfall over 2 months and heavy rainfall the day before triggered the slope failure. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices

Inferring Dynamic Fragmentation Through the Particle Size and Shape Distribution of a Rock Avalanche

AbstractOn 28 August 2017, a large catastrophic rock avalanche occurred in Nayong, Guizhou Province, China. It claimed 35 lives and caused large property losses. The Nayong rock avalanche provides a rare opportunity to infer the dynamic fragmentation of rock masses from deposits. Field surveys combined with an uncrewed aerial vehicle image analysis system were performed to investigate the particle size and shape distribution along the runout path of the Nayong rock avalanche. The Weibull particle size distribution (PSD) model was tested and possesses the highest accuracy and capability over the entire range of the Nayong rock PSD, and it shows that the median size (D50) values of the particles range from 0.16 to 16.31 m along the runout path. Moreover, the evolution of D50 along the runout path confirms that the degree of rock fragmentation varies greatly in different regions. Additionally, the relative breakage (BR) of particles in the deposition area is 0.191. Particle R values increase significantly from 0.55 to 0.78 along the runout path, which indicates that the rock grinding (shape change) process continuously occurs throughout the avalanche path. The image analysis results confirm that the dominance of rock fragmentation and grinding alternates during granular flow transport. Based on these results, the classic fragmentation‐spreading model for long‐runout rock avalanches is optimized by taking into account the method by which grinding rocks increases the speed of avalanches.

Predicting landslide runout paths using terrain matching-targeted machine learning

Landslide debris will travel certain distances and threaten people and properties along its runout path, highlighting the importance of runout path prediction in landslide risk management. Conventional landslide runout models, either statistical or machine learning-based, only consider the geographic characteristics at the source without fitting the terrain features along the path. A novel terrain matching-targeted machine learning model is proposed for predicting landslide runout paths, in which a consistent terrain matching strategy is introduced for both training and prediction. The model first forward predicts multiple travel distances based on geographic characteristics of all cells along a possible runout path, and then determines the termination cell whose predicted travel distance fits the terrain features best to backward estimate model parameters. Such a terrain matching process not only accounts for geographic characteristics along the paths but also enables the incorporation of three-dimensional terrain reality into model training. A case study of natural terrain landslides in Hong Kong is conducted to validate the proposed machine learning model. Results indicate that the terrain matching-targeted machine learning models significantly outperform conventional statistical models in terms of prediction accuracy. The fall height and landslide scale are the most critical physical factors affecting travel distances of channelized landslides and open hillslope landslides, respectively. The landslide runout model is applied to the Mid-Levels at the foot of Victoria Peak to identify high-risk urban areas vulnerable to landslides, which provides guidelines for designing landslide prevention and mitigation measures.

Origin and emplacement of the Blue Diamond landslide breccia, southern Nevada, U.S.A.

ABSTRACT Landslide deposits are common in basin fill of tectonically active areas, including the Basin and Range province of western North America. However, interpreting and reconstructing ancient landsliding events from these deposits is challenging, but can be aided by detailed field analysis. Remnants of the Blue Diamond landslide breccia are exposed capping hills and ridges in the foothills of the eastern Spring Mountains near Blue Diamond, Nevada, USA. Uncertainties surrounding the origin and emplacement of the ancestral Blue Diamond landslide have emerged based on the disparate distribution of landslide outcrops. Therefore, in this study we used detailed sedimentological data and observations to interpret a two-phase emplacement history for the Blue Diamond landslide. Sedimentological observations are consistent with Blue Diamond landslide breccia emplacement as a rock avalanche. The presence of clastic dikes and flame structures and negligible incorporation of bedrock substrate material suggest that runout occurred over a saturated substrate. Flow transformation into a debris avalanche is ruled out because clast-count data show that debris entrainment was not sufficient to act as the sole mechanism behind the excessive mobility experienced by the Blue Diamond landslide. Instead, we propose that the excessive mobility was driven by flow entrainment of large Aztec Sandstone boulders and interaction with a saturated runout path substrate that caused a reduced basal frictional resistance, enabling initial emplacement onto Blue Diamond Hill. We therefore suggest that the Blue Diamond landslide was derived from a source area about 8.5 km northwest of the Blue Diamond townsite and flowed into the Blue Diamond Hill site where it was emplaced onto Moenkopi Formation atop the hill during the Miocene. Due to loading by this new overburden, incompetent gypsum horizons failed in the upper Kaibab Formation stratigraphically below the Moenkopi Formation. These failed gypsum horizons then served as a compound landslide rupture surface, transporting the overlying Moenkopi Formation and landslide breccia. This secondary emplacement likely ceased by late Miocene to Pliocene time.

Frost cracking dictated landslide distribution in response to temperature change since Last Glacial Maximum across the Eastern Qilian Mountains

AbstractTemperature‐dependent frost cracking is a major weathering process that dominates sediment supply and hillslope erosion by reducing shear strength and conditioning slopes to be more failure‐prone in cold mountain regions. Landslides are a common erosional process in such landscapes. The linkage between these two processes has been proposed but many of the mechanisms remain to be investigated. In this study we compile a landslide inventory in the Eastern Qilian Mountains including 2482 rockfalls and 5373 elongate transport zone footprints. We use a widely accepted frost cracking model to explore this weathering process as a mechanism of paleoclimate control on the modern landslide distribution. The results show that landslides concentrate in a narrow altitudinal range and that this elevation dependence varies with slope aspect. Based on the paleoclimate record, we calculate the time‐averaged frost cracking intensity (Fci) since Last Glacial Maximum (LGM) and adopt different parameters for two slope aspects. We find that time averaged Fci is a good predictor of the landslide elevation distribution for both aspects. We then introduce two slope‐based landslide initiation and runout models (i.e., SHALRUN and FCIRUN) to examine the relative roles of slope versus temperature in determining the landslide probability in space. The FCIRUN model, which incorporates Fci as a measure of sediment supply, consistently outperforms the SHALRUN model. This result suggests that frost cracking determines the pattern of landslide initiation, although topography still controls their runout path. Our study highlights the potential of introducing Fci into slope‐based landslide prediction models to improve model skill in identifying hazardous areas (e.g., rockfall) across weathering‐limited landscapes like the Qilian Mountains.

Runout Number: A New Metric for Landslide Runout Characterization

ABSTRACT Landslide runout has traditionally been quantified by the height-to-length ratio, H/L, which, in many cases, is strongly influenced by the slope of the runout path. In this study, we propose an alternative mobility measure, the unitless Runout Number, measured as the landslide length divided by the square root of the landslide area, which characterizes landslide shape in terms of elongation. We used a database of 158 landslides of varying runout distances from locations in northern California, Oregon, and Washington state to compare the two runout measurement methods and explore their predictability using parameters that can be measured or estimated using geographic information systems. The Runout Number better describes the overall runout for several landslide and slope geometries. The two mobility measures show very little correlation to each other, indicating that the two parameters describe different landslide mobility mechanisms. When compared to predictive parameters shown by prior research to relate to landslide runout, the two runout measurement methods show different correlations. H/L correlates more strongly to initial slope angle, upslope contributing area, landslide area, and grain size distribution (percent clay, silt, total fines, and sand). The Runout Number correlates more strongly to planimetric curvature, upslope contributing area normalized by landslide area, and percent sand. Although these correlations are not necessarily strong enough for prediction, they indicate the validity of both runout measurement methods and the benefit of including both numbers when characterizing landslide mobility.

A virtual geographic environment for dynamic simulation and analysis of tailings dam failure

ABSTRACT It is of great significance for disaster prevention and mitigation to carry out disaster simulations for dam failure accidents in advance, but at present, there are few professional systems for disaster simulations of tailings dams. In this paper, we focused on the construction of a virtual geographic environment (VGE) system that provides an effective tool for visualizing the dam-break process of a tailings pond. The dam-break numerical model of the tailings dam based on computational fluid dynamics (CFD) was integrated into the VGE system. The infrastructure of the VGE was supported by a 3-D geographic information system (GIS) with a user-friendly interface for the initiation, visualization, and analysis of the dynamic process of tailings dam failure. Key technologies, including the integration of numerical models, rendering of large-scale scenes, and optimizations of disaster simulation and visualization, were discussed in detail. In the prototype system, information on the run-out path, travel distance, etc. can be obtained to visually describe the flow motion released by two dam failure cases. The simulation results showed that the VGE can be used for the multidimensional, dynamic and interactive visualization of dam-break disasters, and can also be useful for assessing the risk associated with tailings dams.

When hazard avoidance is not an option: lessons learned from monitoring the postdisaster Oso landslide, USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

Coupled 3D numerical model for a landslide-induced impulse water wave: A case study of the Fuquan landslide

Large impulse waves are generated when a highly mobilized landslide impacts a water body along the runout path. On August 27, 2014, a massive landslide occurred in Fuquan, Guizhou, China and induced an impulse wave upon contact with a quarry lake. The landslide and its associated impulse wave were a multiphase and multicomponent mixture that collectively destroyed two villages. The present study provides insights into multiphase dynamic analysis by employing an existing 3D coupled discrete element modeling and computational fluid dynamics approach to model a case study of the Fuquan landslide and its impulse wave. EDEM and Fluent were two-way coupled by an application programming interface, which transferred data between the models to simulate subaerial movement and impulse wave generation. The simulated results indicate a maximum velocity of 31.7 m/s achieved by the subaerial movement and a runout duration of 39 s. The detached mass entered the quarry lake at a velocity of 24.3 m/s, at t = 7.1 s after the landslide initiation. Energy was transferred between the sliding mass and lake water, and the generated water wave rushed toward the opposite slope. The generated wave had a run-up of 28.4 m and traveled approximately 90 m in the lateral direction, with a maximum dynamic pressure of 3.03 MPa. Qualitative validation of the present model was performed using Fritz's experimental setup for wave generation, and the velocity evolution was physically verified. This study provides calibrated parameters for the forward simulation of similar cases of landslide-induced impulse water waves and related hazard zonation.

Snow cornice and snow avalanche monitoring using automatic time lapse cameras in Tasiapik Valley, Nunavik (Québec) during the winter of 2017–2018

A series of automatic time-lapse cameras installed along the southwestern side of Tasiapik Valley, near the village of Umiujaq, Nunavik (northern Québec) documented several departure modes and types of snow involved in snow avalanches during winter 2017–2018. These included cornice–avalanche dynamics, slab and loose snow avalanches, and clean and dirty snow avalanches. At the top of the selected slope, a camera monitored the development of a snow cornice beginning in November 2017, detecting multiple cornice failures over the winter and spring. The track and deposition area of the runout paths were monitored from two cameras downslope, revealing the concomitance of snow–cornice fall and snow avalanche triggering. Snow avalanche activity remained relatively infrequent until the end of May 2018. Spring snow avalanche activity is characterized by wet and dirty snow avalanches carrying debris to the foot of the slope and by runout zones located near the road along the slope.

Debris Flow Susceptibility Assessment and Runout Prediction: A Case Study in Shiyang Gully, Beijing, China

At 14:00 on 18 June 2017, floods occurred in Shiyang gully at the junction of Beijing and Hebei Province, China. The floods put 12 people at risk, 6 of whom died. After the occurrence of the floods, the environment in Shiyang gully has undergone tremendous changes. There are many loose residual materials in the watershed. Therefore, it was necessary to evaluate the debris flow susceptibility of Shiyang gully after the disaster. The factor analysis method, entropy weighting method and geomorphic information entropy method were used to evaluate the debris flow susceptibility of each sub-watershed in Shiyang gully. By comparison with the technical standard published by the China Ministry of Lands and Resources, it was found that the susceptibility assessment results are not ideal. To improve the accuracy of the assessment results, we used a comprehensive method. The accuracy of the susceptibility assessment obtained by the comprehensive method is 87.5%. This accuracy shows that the comprehensive method is applicable to the susceptibility assessment of debris flows in this region. To predict the runout path of potential debris flows in four sub-watersheds with very high susceptibility, the authors used the SFLOW software developed by Jilin University to simulate the debris flow hazards. Combined with the on-site investigation data, debris flows in the four sub-watersheds were simulated at 10-, 20-, 50-, and 100-year recurrence intervals. The obtained runout path could provide some guidance and reference for the avoidance of disasters and treatment of debris flows.

Investigation of the dynamic process of the Xinmo landslide using the discrete element method

Abstract As a useful tool to simulate the movement of granular materials, the Particle Flow Code is used to analyze the dynamic process of the Xinmo landslide, including: disintegration, entrainment, granular flow and accumulation. The microparameters of the landslide rock mass were calibrated with uniaxial compression and landslide deposition simulations. The results show that the kinetic characteristics of the collapse mass were more sensitive to the bond strength than to the friction coefficient. For the colluvium on the runout path, the influence on the kinetic characteristics was insignificant in the case of the lower bond strength and friction coefficient. The whole process lasted approximately 100 s, and the main sliding time was 65 s. The peak velocity was 72.4 m/s, and the maximum displacement was approximately 2.5 km. The results indicate that the gravitational potential energy was mainly converted into friction energy and kinetic energy in the acceleration stage. However, the proportion of the collision energy increased gradually in the deceleration stage. The entrainment effect plays an important role in the Xinmo landslide movement. The high gravitational potential energy of the collapse mass was the basis of the high mobility, and the mobility was further enhanced because of the entrainment effect.

Sturzprozesse ausgehend von Felsböschungen: Abschätzung der Reichweite mithilfe numerischer Modelle

AbstractRunout processes originating from rock slopes can be classified according to their process behaviour into rockfall, rock mass fall and rock avalanche. Their process behaviour is primarily determined by the volume of the detached rock mass, the degree of fragmentation of the moving mass and the morphology and nature of the runout path. The initial conditions of these processes depend on the initial failure mechanism. It is difficult to predict the runout and magnitudes of these types of rapid landslides since the complexity of the processes requires major simplifications in the calculation approaches. A good understanding of the process and clear mechanical model conceptions are therefore crucial in the development and choice of prediction models. The paper presents a classification of the runout processes originating from rock slopes on the basis of clearly defined mechanical models and provides an overview of the currently available models for prediction.

Rock slide–debris avalanches: flow transformation and hummock formation, examples from British Columbia

Rock slides quite commonly transform into flow-like landslides along their runout paths. At three initial rock slides in northern British Columbia, which occurred between 2002 and 2005, around 50–70% of the entire runout distance is composed of debris avalanche and debris flow deposits, which is comparable to other composite landslides around the world. Saturated ground conditions at the time of rock sliding make entrainment or undrained loading as agents of flow transformation from initially dry rock slides to partially saturated debris avalanches, respectively, fully saturated debris flows likely. Hummocks occur as clusters within the rock slide parts, whereas the flow-like depositions have more subdued morphologies. We show that late- or post-emplacement motion of individual hummocks is possible and can even divert in direction from the dominant landslide trajectory by responding to the underlying topographic gradient. Analyses of the well-preserved deposits suggest hummock formation above a basal sliding plane (low-angle normal fault) and along subordinate shear zones (high-angle normal faults) within a largely translational mass movement, thereby supporting the hypothesis of hummock formation proposed by Paguican et al. (2014). Pebbles on top of rock slide-debris avalanche boulders and on top of snapped-off trees record much higher dynamic debris flow heights. These and other features are not recorded on ancient landslides due to rapid erosion.

The 2016 Lamplugh rock avalanche, Alaska: deposit structures and emplacement dynamics

Supraglacial landslides result from the catastrophic failure of periglacial rock slopes and deposit large volumes of rock and ice onto the glacier surface. The most remarkable features of these landslides are their prominent long flowbands and a high mobility that exceeds that of their counterparts in other environments. Based on field surveys, high-resolution digital elevation models, and continuous seismic data, we show that the emplacement dynamics of the 2016 rock avalanche on Lamplugh Glacier were characterized by two distinct stages. During the first stage, the debris traveled about 5 km from the base of the slope. Clear long-period seismic signals during this stage record strong interactions of the rock avalanche debris with the ground, suggesting dynamic processes such as grain collisions and fragmentation. The second stage was essentially aseismic at long periods and dominated by low-friction sliding at slow deceleration rates. A higher density of flowbands and increased entrainment of snow from the runout path characterize the morphology of this second-stage distal deposition. Around the margins, lobes are offset by up to 400 m along major strike-slip faults, whereas within individual lobes, offsets between flowbands are much less pronounced (0 to < 10 m). The two-stage emplacement model may explain the higher apparent mobility of supraglacial landslides.

How does a cluster of buildings affect landslide mobility: a case study of the Shenzhen landslide

Urban landslides always occur where development has taken place on pre-existing unstable land. Due to rapid urbanization, human activities expand onto sloping terrain and disturb the geological environment, increasing the urban landslide risk. When a rapid flow-like landslide occurs, the landslide mobility can be affected by the presence of buildings located along its flow path. In this paper, the effect of building blockage on landslide mobility and the associated energy dissipation mechanisms are evaluated based on a well-documented landslide, which happened on 20 December 2015 in Shenzhen, China. The landslide flow process is reproduced by three-dimensional terrain analyses using LS-DYNA, considering three scenarios; namely, green field, movable buildings, and fixed buildings. Simulations show that the presence of densely located buildings significantly affects flow pattern, travel distance, deposition, and energy transfer mechanism. A fully developed debris fan in the flat area is observed in the green field case. The buildings in the runout path decelerate the flow process, leading to lower landslide mobility and less volume deposited in the accumulation zone. The shortest runout distance and widest and thickest deposits are observed in the fixed buildings case. The debris fan in the movable buildings case is closer to reality. Fixed buildings pose more constraint on surface moving material, leading to the largest deformation, largest internal energy, and smallest kinetic energy of the soil mass. The dissipation of the largest frictional energy occurs in the movable buildings case due to the long sliding distance of the damaged buildings. The internal energy of the landslide mass dominates the energy transfer mechanism. The results presented here indicate the need to consider building clusters when conducting urban landslide hazard mapping and risk assessment.

Insights into the catastrophic Xinmo rock avalanche in Maoxian county, China: Combined effects of historical earthquakes and landslide amplification

A large and catastrophic rock avalanche occurred at the Xinmo village in the Maoxian county of the Sichuan province of China on June 24, 2017. The avalanche destroyed 64 houses and killed 10 people, and 73 people were reported to be missing. In this study, we focused on the contributions of six historical earthquakes to the collapse of rocks in the source area and the landslide amplification caused by the entrainment of pre-existing deposits on the landslide path. The historical earthquakes in this area contributed different levels of damage on the source rocks; particularly, the 1933 Diexi earthquake induced a few initial cracks in rocks at the crest of the steep hillslope. Under the combined time-effects of long-term weathering and gravity, the rock blocks in the source area were detached from the crest along the intersecting cracks and over-dip soft layer (namely, the sliding surface). The avalanche was amplified by the entrainment of colluvium on its path. The influence of the colluvium on the movement process of the Xinmo landslide was modelled by the GPU-based parallel discontinuous deformation analysis (DDA) method, and the effect of the impact and entrainment in the debris flow was rigorously analysed. The results indicate that the impact and entrainment can continuously increase the volume of debris flow, and the thickness of the colluvium was established to be in the range of 25.9–33.9 m based on the analysis of the deposit pattern and movement duration of the avalanche. There were numerous unstable rocks induced by historical earthquakes, at the crests of steep hill slopes in the earthquake-stricken area. With long-term damage caused by environmental factors and gravity, the failure of unstable rocks with high potential energy is likely to cause severe disasters. The excess pore water pressure likely to be present in the colluvium or deposits during impact and entrainment can considerably reduce the effective stress and degrade friction resistance along the runout path. As a result, the landslide can be intensively amplified owing to the effect of impact and entrainment under a lower friction resistance