Landslide Dam Research Articles

Assessment of the Ecological Risks of Landslide Damages in the Carpathian Region

The dynamism of the landslides within the Carpathian region of Ukraine is because of the difficult engineering and geological conditions. High landslide den sity and significant population density contribute to the fact that environmental parameters worsen and require rational management. Permanent natural factors like clay flysch formation, fault tectonics, high seismic activity, and dense network of rivers mostly facilitate the active development of landslides in the Carpathian region. However, it is triggered by extreme long-term precipitation. The numerical parameters of population density, the landslide damage coefficient, and the predictive range of landslide intensification were selected to assess the ecological risk of damages in the area. The landslide dam age coefficient characterizes the tendency of the area to landslide development, considering all the factors contributing to the landslides. Risk, as a multifunctional calculated complex, includes the calculation of damage, according to which we can assess the possibility of risk for the human being while assuming the equal distribution of the population within the study area. The integral components of the risk are calculated based on the data gathered to assess the growth of risks in the future, considering the area distribution and predictive time series of the landslide intensification. This analysis has identified engineering and geological areas having the greatest risk to human life.

Predicting landslide susceptibility based on decision tree machine learning models under climate and land use changes

Landslides are most catastrophic and frequently occurred across the world. In mountainous areas of the globe, recurrent occurrences of landslide have caused huge amount of economic losses and a large number of casualties. In this research, we attempted to estimate the potential impact of climate and LULC on future landslide susceptibility in of Markazi Province of Iran. We considered the boosted tree (BT), random forest (RF) and extremely randomized tree (ERT) models for landslide susceptibility assessment in Markazi Province. The results of evaluation criteria showed that ERT model is most optimal than other models used in this study with AUC values of 0.99 and 0.93 for the training and validation datasets, respectively. According to the ERT model, the spatial coverage of the very high and high land slide susceptible zones for the current period, 2050s considering RCP 2.6 and 2050s considering RCP 8.5 are 428.5 km2, 439.6 km2 and 465.2 km2, respectively. From this analysis it is clear that the impact of climate and LULC changes on future landslide susceptibility is prominent. The results of the present study help managers to reduce landslide damages, not only for current but also for future conditions, based on climate and LULC changes.

The formation and geometry characteristics of boulder bars due to outburst floods triggered by overtopped landslide dam failure

Abstract. Boulder bars are a common form of riverbed morphology that could be affected by landslide dams. However, few studies have focused on the formation and geometry characteristics of boulder bars due to outburst floods triggered by landslide dam failure. In such a way, eight group landslide dam failure experiments with a movable bed length of 4 to 7 times the dam length with 25 boulder bars were carried out. In addition, 38 boulder bars formed in the field triggered by four landslide dam failures were investigated. The aim of this paper is to study the formation and geometry characteristics of boulder bars along the riverbeds. The results show that boulder bars are formed after peak discharge of outburst flow. The number of boulder bars is 0.4 to 1.0 times the ratio of riverbed length to dam bottom length. Besides, boulder bars have the characteristic of lengthening upstream during the failure process. A boulder bar's upstream edge has a more extensive development than a boulder bar's downstream edge. The length of a boulder bar along the channel changes faster than the boulder bar's width and height. After the dam failure, the boulder bar's length is about 8 to 14 times its width. The relationship between the ratio of boulder bar length to width and the boulder bar's dimensionless length could be described with a hyperbolic equation. The dimensionless area of the boulder bar increases linearly with the dimensionless area of the river section, and the linear ratio is about 0.5. With the field data, this demonstrates that the formation and geometry characteristics of boulder bars in tests are consistent with the field boulder bars. Therefore, the results in this paper are credible and can be applied to the riverbed's geomorphological characteristics analysis triggered by overtopped landslide dam failure. The plentiful experimental and field data could contribute to the community boulder bar research.

Multi-phase flow simulation of landslide dam formation process based on extended coupled DEM-CFD method

The landslide-river interaction and the impulse waves involved in the landslide dam formation process may not be insignificant and have not been extensively investigated and simulated. This paper presents a numerical investigation on the formation process of landslide dams and resulting free surface flow dynamics in the impacted river via coupled discrete element method (DEM) and computational fluid dynamics (CFD) with the volume of fluid (VOF). The accuracy and validity of the extended coupled method are verified using a series of test cases involving three-phase interaction and free surface evolution. It is then applied to simulate the landslide dam formation processes related to landslide and river flow scenarios of different kinematic characteristics. Furthermore, quantitative analysis is performed to describe the complex evolution of the dam morphology and dynamic evolution of impulse waves. It is found that the impact between the landslide, river flow and valley drives the dam formation process. The landslide velocity considerably influences the propagation of impulse waves, while the river flow velocities control the dam morphology in opposite ways in the upstream and downstream. This research provides a practical modeling framework to understand the formation mechanism of landslide dams and support applications in hazard prediction and mitigation.

Large-scale field model tests of landslide dam breaching

The breaching of landslide dams is a severe geological disaster, and the resulting breaching floods significantly threaten people in downstream areas. In this study, a large-scale physical model was constructed in a natural river channel using unconsolidated dam material with a wide grain size distribution. Terrestrial laser scanning was used to capture three-dimensional geometric information of the landslide dam during the breaching process. The results showed that the dominant erosion pattern during dam breaching was surface progressive erosion. The breaching process could be divided into three stages based on different erosion characteristics: headward erosion, rapid erosion, and attenuated erosion. Longitudinal and lateral evolution models were proposed based on the field test results. The longitudinal evolution model describes the erosion at the dam crest and the sedimentation at the dam toe during the breaching process by defining the erosion and rotation points. The lateral evolution model revealed different lateral erosion characteristics at different cross-sections. Both the longitudinal and lateral evolution models were validated using two dam break events of the Baige landslide. The evolution models proposed in this study provide a scientific reference for numerical simulations of dam breaching and the prevention and mitigation of landslide dams.

Warning Decision-Making for Landslide Dam Breaching Flood Using Influence Diagrams

Warning and evacuation are among the most effective ways for saving human lives and properties from landslide dam hazards. A new warning decision model for landslide dam break is developed using Influence Diagrams to minimize the total losses. An Influence Diagram is a simple visual representation of a decision problem. It analyzes the qualitative (causal) relationships between the variables via a logic diagram and determines the quantitative relationships via conditional probability and Bayes’ theorem. The model is applied for the warning decision-making of the 2008 Tangjiashan landslide dam. The new model unifies the dam failure probability, evacuation, life loss, and flood damage in an Influence Diagram. Besides, a warning criterion is proposed for efficient decision-making. The model is more advanced than the decision tree since the inter-relationships of influence factors are qualitatively analyzed with causality connections and quantitatively analyzed with conditional probabilities. It is more efficient than a dynamic decision-making model (DYDEM) as it can directly calculate the three types of flood loss (i.e., evacuation cost, flood damage, and monetized life loss) and the expected total loss. Moreover, the probabilities of the influence factors leading to known results can be obtained through inversion analysis based on Bayesian theory. The new warning decision model offers an efficient way to save lives from landslide dam breaking and avoid unnecessary expenses from premature warning and evacuation.

Geomorphic effects of recurrent outburst superfloods in the Yigong River on the southeastern margin of Tibet

Landslide dam outburst floods have a significant impact on landform evolution in high mountainous areas. Historic landslide dams on the Yigong River, southeastern Tibet, generated two outburst superfloods > 105 m3/s in 1902 and 2000 AD. One of the slackwater deposits, which was newly found immediately downstream of the historic dams, has been dated to 7 ka BP. The one-dimensional backwater stepwise method gives an estimate of 225,000 m3/s for the peak flow related to the paleo-stage indicator of 7 ka BP. The recurrence of at least three large landslide dam impoundments and super-outburst floods at the exit of Yigong Lake during the Holocene greatly changed the morphology of the Yigong River. More than 0.26 billion m3 of sediment has been aggraded in the dammed lake while the landslide sediment doubles the channel slope behind the dam. Repeated landslide damming may be a persistent source of outburst floods and impede the upstream migration of river knickpoints in the southeastern margin of Tibet.

Large-Scale Field Test Study on Failure Mechanism of Non-Cohesive Landslide Dam by Overtopping

In recent years, landslide lake disasters occur frequently in southwest mountainous areas of China. Considering the influence of dam size and discharge channel location, three large-scale field tests were carried out in a natural river to study the failure process and mechanism of non-cohesive soil landslide dam, and the process and mechanism of non-cohesive landslide dam breach were analyzed. The results show that the dam size and discharge channel location have a significant influence on the breach mechanism of the landslide dam. The dam failure process can be divided into three stages: the initiation stage, the development stage and the failure stage. When the discharge channel is located close to the bank, the width of the breach is smaller, and the volume of the residual dam body is larger. The more stable the dam body is, the longer the breach process time is, and the smaller the peak discharge is. This study can provide a scientific reference for the emergency disposal and risk assessment of landslide dam.

A novel parameter inversion method for an improved DEM simulation of a river damming process by a large-scale landslide

The Discrete Element Method (DEM) is one of the most common numerical methods employed for the study of landslide disasters. Herein, this study proposes a method addressing the challenges associated with the selection of contact parameters for DEM blocks (or particles) when simulating landslide hazards. In 2018, two landslides occurred successively at the same slope of Baige, in Tibet, China. To efficiently simulate the entire process of landslide dynamics, a Graphics Processing Unit (GPU) program for blocky DEM, named CoSim-DEM, is developed. Furthermore, a parameter inversion method for the DEM simulation considering the deformation and failure process of landslide is provided and used to obtain the contact parameters for DEM blocks based on the failure process of the first landslide. The failure process of the second landslide is also simulated with the parameters obtained. The geomorphic characteristics of the landslide dams of the two times lanslides obtained by CoSim-DEM are validated by the field investigations. Based on the numerical results, the landslide damming process is divided into five stages and the entire path of the landside is divided into three zones. The results of this study provide a method to construct a database of parameters for geomaterials by using an inversion method based on the previous landslide cases. The method will be important for the rapid assessment and study of landslide hazards in the future.

Analyzing the multi-hazard chain induced by a debris flow in Xiaojinchuan River, Sichuan, China

The damage caused by a single natural hazard can be amplified in time and space to form a disaster chain. One such chain was induced by a debris flow that occurred on June 17, 2020 along the Xiaojin River on the eastern Tibetan Plateau of China. The debris flow dammed the Xiaojin River, and subsequent dam breaches instigated a multi-hazard chain that flooded many towns upstream; moreover, the flooding reactivated an ancient landslide downstream, the Aniangzhai landslide. To understand the failure mechanism and risk of such events, a combination of in-situ investigation, remote sensing analysis, and simulation were performed. Field investigations and high-resolution images confirmed that two potential sliding masses detached from the slope, with a overall volume of approximately 30 million m3. To understand the overall disaster chain and evaluate the effects linked to these potential sliding masses, the multi-hazard chain was systematically analyzed using various data and approaches, Finding shows that the reactivation of the Aniangzhai landslide are resulted from the continuous down-cutting and erosion by outburst flooding. Finally, the hypothetical scenarios analyses were completed with respect to the landslide dam and resultant flooding. Integrated studies of disasters based on such a systematic approach can be applied to future analysis of similar hazard chains.

Ambient noise and ERT data provide insights into the structure of co-seismic rock avalanche deposits in Sichuan (China)

The post-seismic history of the 2008 Mw7.9 Wenchuan earthquake shows that marginally stable deposits of large co-seismic landslide dams can pose persistent debris flow hazards for the downstream areas. Here, we combine analyses of single-station recordings of ambient noise with electrical resistivity tomography (ERT) surveys to explore the potential of drawing information on structure and geometry of the deposit of a large rock avalanche triggered by the Mw 7.9 2008 Wenchuan earthquake, which dammed the Yangjia stream in the Sichuan Province (China). The substantial thickness and heterogeneity of this kind of deposits limit the application of standard geophysical techniques, like active seismic surveys, which require highly energetic sources and long linear geophone arrays to reach adequate investigation depths. Passive single-station methods, relying on ambient noise recordings to determine site resonance properties, controlled by the contrast between soft surface layers and a stiffer substratum, offer the opportunity of investigating subsoil properties down to larger depths. In particular, we use a recently developed technique, which isolates the contribution of Rayleigh waves to ambient noise and draws information on sub-soil properties from the inversion of Rayleigh wave ellipticity curves plotted as function of frequency. In this framework, the ERT data can support the ellipticity curve inversion, typically affected by highly non-univocal solutions, by providing constraints for defining of the thickness of the uppermost surficial layers. The results allowed inferring the overlap of different layers within the 2008 rock avalanche deposit, as well as estimating lateral variations in their thickness and S-wave (Vs) velocities.

Uncertainty quantification in shallow water-sediment flows: A stochastic Galerkin shallow water hydro-sediment-morphodynamic model

All shallow water hydro-sediment-morphodynamic (SHSM) models are prone to uncertainty arising from inadequate representation of the underlying physics and error in input parameters. At the time of writing, most SHSM models solve deterministic problems, whilst studies of uncertainty quantification in SHSM models remain rare. Here a new stochastic SHSM model is proposed, extended from a well-balanced, operator-splitting-based, generalized polynomial chaos stochastic Galerkin (gPC-SG) solver of the one-dimensional shallow water hydrodynamic equations. A series of probabilistic numerical tests are carried out, corresponding to idealized dam break flow over a fixed bed and laboratory experiments of flow-sediment-bed evolutions induced by a sudden dam break and by landslide dam failure. The proposed modelling framework shows promise for uncertainty quantification of shallow water-sediment flows over erodible beds.

Numerical simulation of landslide dam overtopping failure considering headward erosion

Landslide dams often fail shortly after the formation, resulting in huge risks to the downstream residents and properties. Fast and accurate forecasting of the breaching process and discharge hydrograph is important for a decision making to mitigate the damages. Morphological data indicate that the longitudinal length of most landslide dams is much larger than their transverse length. Additionally, headward erosion is more intense in landslide dams than manmade dams during the overtopping failure process. However, most existing models neglect this phenomenon. The objective of this study is to build up a dam-break model considering the headward erosion process, assuming that the change rate of downstream slope-angle is consistent with the rate of breach vertical erosion. And a dam-break numerical model to simulate the overtopping failure process of landslide dams considering the headward erosion was developed based on the theories of hydraulics, hydrology, soil mechanics, sediment dynamics, and etc. Nevertheless, the breach final bottom elevation, which can only be measured after the dam failure, is directly applied in currently available dam break models. To overcome this problem and for the prediction purpose of a newly formed landslide dam, we proposed an empirical model to estimate the breach final bottom elevations of high, medium and low erodibility landslide dams based on the statistical analysis of worldwide landslide dam failure cases collected recently. To verify the effectiveness of proposed dam-break numerical model, the ‘11.03′ Baige landslide dam which locates at the border of Tibet Autonomous Region and Sichuan province was selected as a case study. Results of this study show that the relative errors in the simulated peak discharge, time to the peak, and the total flood volume are 1.59%, 3.50% and 0.53%, respectively, which meet the accuracy requirements of hydrological forecasting. The relative error in the prediction of breach final bottom elevation is 4.28%, which indicates that the accuracy of the simulation is satisfactory. Finally, a sensitivity analysis indicates that the downstream slope affects the prediction of the breach and flood hydrograph significantly, and the excavation of diversion channel is an effective measure to reduce the peak discharge of dam overtopping failure.

Erratum: Risk-Based Warning Decision Making of Cascade Breaching of the Tangjiashan Landslide Dam and Two Smaller Downstream Landslide Dams

An erratum on: Zhu Y, Peng M, Cai S and Zhang L (2021) Risk-Based Warning Decision Making of Cascade Breaching of the Tangjiashan Landslide Dam and Two Smaller Downstream Landslide Dams. Front. Earth Sci. 9:648919. doi: 10.3389/feart.2021.648919Due to an oversight during the review process, an existing conflict of interest between the handling editor and one of the authors was not declared. The publisher apologizes for this mistake.The original version of this article has been updated.

Experimental study on breaching mechanisms of landslide dams composed of different materials under surge waves

After the formation of a landslide barrier lake, additional landslides in the lake area can generate huge waves, which may overtop the landslide dam and eventually lead to breaching failure of the dam. Since landslide dams are natural dams without compaction, the dam materials are heterogeneous, loose and highly erodible, so that the breaching process under wave actions is rather complex. Although a number of model tests have been conducted by different workers, several critical issues have not been addressed satisfactorily, including influences of landslide dam materials on breaching characteristics, stability criteria for landslide dams under surge waves, and differences in the breaching mechanisms by surge wave impact and natural overtopping flow. In this study, 9 flume tests were conducted to study the breaching mechanisms of landslide dams composed of fine, medium and coarse materials under surge waves of three wave heights. Compared with the natural overtopping condition, the breaching process under surge wave impact is much faster (the consumed time is only 2%-20%) and the peak discharge of breaching flood is 1.1-5.1 times larger. The surge waves accelerate the landslide dam breaching with more intense surface erosion and larger dynamic pore pressure. The total erosion volume and breaching duration decrease with the increase of mean particle size. With the increase of wave height, both the average erosion rate and peak discharge of the breaching flood increase. An empirical equation of wave climbing height for landslide dams was established based on the flume test results, which considers slope angle, surface roughness of dam and wave characteristics. The net overtopping height, ΔH, which is the difference between the sum of wave climbing height and still water level and the effective dam height, can be adopted as a useful index to preliminarily judge whether the landslide dam is stable or not under the impact of surge waves. When ΔH < 0, the dam is stable; otherwise the dam is unstable.

Effect of vertical velocity profile approximations on estimates of dam breach discharge using surface velocities

AbstractIn order to investigate the relationship between water surface velocity and breach hydrograph, a series of dam breach experiments with a generalised landslide dam were conducted in an open channel of 50 m × 4 m × 2 m. The large‐scale particle image velocimetry (LSPIV) technique was applied to measure the time history of water surface velocity during the dam breach process, and the hydrography was obtained by integrating the surface velocity along the water depth. The influence of different vertical velocity profile approximation and suspended sediment concentration on the peak breach discharge were analysed and discussed. The results showed that the water depth over the breach crest can be described as a function of water surface velocity using . A simple formula based on surface velocity and breach width for the estimation of breach discharge was further proposed and verified.

Mapping Outburst Floods Using a Collaborative Learning Method Based on Temporally Dense Optical and SAR Data: A Case Study with the Baige Landslide Dam on the Jinsha River, Tibet

Outburst floods resulting from giant landslide dams can cause devastating damage to hundreds or thousands of kilometres of a river. Accurate and timely delineation of flood inundated areas is essential for disaster assessment and mitigation. There have been significant advances in flood mapping using remote sensing images in recent years, but little attention has been devoted to outburst flood mapping. The short-duration nature of these events and observation constraints from cloud cover have significantly challenged outburst flood mapping. This study used the outburst flood of the Baige landslide dam on the Jinsha River on 3 November 2018 as an example to propose a new flood mapping method that combines optical images from Sentinel-2, synthetic aperture radar (SAR) images from Sentinel-1 and a Digital Elevation Model (DEM). First, in the cloud-free region, a comparison of four spectral indexes calculated from time series of Sentinel-2 images indicated that the normalized difference vegetation index (NDVI) with the threshold of 0.15 provided the best separation flooded area. Subsequently, in the cloud-covered region, an analysis of dual-polarization RGB false color composites images and backscattering coefficient differences of Sentinel-1 SAR data were found an apparent response to ground roughness’s changes caused by the flood. We carried out the flood range prediction model based on the random forest algorithm. Training samples consisted of 13 feature vectors obtained from the Hue-Saturation-Value color space, backscattering coefficient differences/ratio, DEM data, and a label set from the flood range prepared from Sentinel-2 images. Finally, a field investigation and confusion matrix tested the prediction accuracy of the end-of-flood map. The overall accuracy and Kappa coefficient were 92.3%, 0.89 respectively. The full extent of the outburst floods was successfully obtained within five days of its occurrence. The multi-source data merging framework and the massive sample preparation method with SAR images proposed in this paper, provide a practical demonstration for similar machine learning applications using remote sensing.

Assessing Earthquake-induced Debris Flow Risk in the first UNESCO World Heritage in Malaysia

The Mw 6.0 Ranau earthquake dated on 05th June 2015 was recorded as one of the strongest earthquakes in the history of Sabah, Malaysia. The earthquake induced many cascading geohazards and earth material in the vicinity of Mount Kinabalu, the first UNESCO World Heritage Site in Malaysia. The earthquake formed a temporary landslide dam that later breached and remobilized as debris flows. This paper provides a new insight into the cascading geohazards as a result of the 2015 Ranau earthquake in Sabah. We evaluated the surface changes of source area that contributes to the landslide damming formation using the remote sensing techniques and field validation. Two image classification methods were performed, including the Maximum Likelihood Classification (MLC), and Nearest Neighbor Classification (NNC). Both presented the supervised pixel- and object-based classifications respectively. This study delineated the source area of before- and after earthquake using the Geographic Information System (GIS), followed by the image classification, accuracy assessment, and surface changes. A series of field mapping was carried out to validate the local evidence. The findings determined three classes within the source area, namely; vegetation cover, bare earth, and stripped earth material (SEM). The surface changes resulted from the earthquake using the MLC was −1.62 km2 (vegetation cover), +0.23 km2 (bare earth), and +1.39 km2 (SEM), while using the NNC was −1.44 km2, +0.12 km2, and +1.32 km2 accordingly. The accuracy assessment of before and after earthquake for the MLC was 86% and 89%, whereas the NNC resulted in a 97% and 95% respectively. The NNC produced higher accuracy of 11% and 6% than the MLC. The increased SEM of 1.44 km2 has contributed to the accumulated earth material and resulted in the landslide damming formation. As a conclusion, this study explores the local risk of debris flow induced by the earthquake, by means of remote sensing technology with improved classification methods. A new insight of possible sediment-induced disaster was presented in the inaccessible and rugged topography, and rapid investigation of potential damming areas in a tectonically active region. This study provides an important clue to understand the local risk and substantially develop Disaster Risk Reduction (DRR) and resilience strategies in the vicinity of UNESCO World Heritage to support the achievement of global targets of the Sendai Framework for Disaster Risk Reduction 2015–2030.

Geometry and the Mechanism of Landslide Occurrence in a Limestone Area – Case Examples of Landslides in Vietnam and from Europe, China, and Japan –

Landslide damage has been reported in many limestone areas in Europe, where the population lives close to limestone areas, and in Guilin in southern China and Ha Long in Vietnam, which are known for their unique limestone landscapes. There are few studies on the mechanism and type of landslide motion in and around such limestone areas. The lack of basic data is a problem for risk assessment and countermeasures in limestone areas. In this study, we summarized the causes and mechanisms of landslide occurrence, including geology and groundwater, focusing on six landslides that occurred in limestone areas in northern Vietnam, and classified them into six types of landslide movement. In the case of Japan, the occurrence of landslides in limestone areas is rare despite the wide distribution of limestone, and it is difficult to classify the type of movement. Differences in the landslide mechanisms are caused by the difference between limestones generated in the pelagic environment of Japan and limestones developed along the Tethys Sea coast, which are mixed with pelitic rocks as shallow-water sediments in Europe, China, and Vietnam. It is necessary to elucidate the relationship between landslides and the formation environment and sedimentary characteristics of limestone as an accretionary prism based on comparisons of a wide range of cases in future studies.

A Numerical Study of the Critical Threshold for Landslide Dam Formation Considering Landslide and River Dynamics

Landslide dam formation can be influenced by the erosive capacity of river flow and the dynamic characteristics of the landslide. When the deposition rate of a landslide that reaches a river is higher than the erosion rate of river flow, the landslide can form a dam by blocking the channel. Hence, in this paper, a dimensionless discharge threshold for landslide dam formation considering landslide and river dynamics is established and studied numerically. A two-layer depth-averaged model coupled with an erosion term is presented to simulate river and landslide movements and their interactions. Several numerical cases are simulated to study the influence of landslide and river dynamics on the critical threshold for dam formation by considering some key factors, such as landslide velocity and the angle between the river and landslide transport directions. Through the simulations, three types of landslide intrusion into river can be reflected: a dam forms quickly, a dam forms or does not form close to a critical state, and no dam forms. The results show that these factors together affect the process of dam formation if the difference between the landslide and river discharges is relatively small. All results are helpful to further clarify the formation of such dams for natural hazard prevention under future climate change conditions.