Landslide Dam Research Articles

Rapid prediction models for 3D geometry of landslide dam considering the damming process

Rapid prediction models for 3D geometry of landslide dam considering the damming process

Energy equation and stress–dilatancy relationship for crushable granular materials incorporating particle breakage

The ROWE’s stress–dilatancy relationship is widely employed to characterise the shear dilatancy behaviour of granular materials. However, particle breakage energy dissipation is excluded from the ROWE’s energy balance equation. In this study, three crushable granular soils with significantly different strengths were subjected to triaxial testing, and the dissipation of energy during the tests was explored. For all three materials, the incremental particle breakage energy dissipation increases and then decreases. It was assumed that at the critical state, particle breakage ended and only frictional energy dissipation occurred. To more accurately characterise the energy dissipation process, an exponential expression of particle breakage energy dissipation is added to the ROWE’s stress–dilatancy relationship. The proposed stress–dilatancy relationship is consistent with the shear dilatancy behaviour of crushable granular materials, and the modified energy equation can more precisely describe the energy dissipation process. The hypothesised stress–dilatancy relationship is applicable to three distinct types of crushable granular materials with varying strengths, including sand-gravel material, landslide dam material and calcareous sand.

Physical and Numerical Simulation of the Mechanism Underpinning Accumulation Layer Deformation, Instability, and Movement Caused by Changing Reservoir Water Levels

Large-scale physical models of landslides can potentially accurately reflect the interactions between many internal and external factors and elucidate the process of slope deformation and failure. In order to reveal the mechanism of deformation of the reservoir bank accumulation layer, in this study, a large-scale physical test model with a similarity ratio of 1:200 was constructed based on the actual engineering geological section. Two reservoir water level cycle fluctuation conditions were simulated, and the reservoir water level drop rate was strictly controlled to be two times the rise rate. This study analyzed pore water pressure and deformation characteristics in the accumulation layer in relation to fluctuating reservoir water levels. The results showed that the rise in reservoir water level will make landslides more stable. The periodic sudden drop in water level seriously endangers the stability of landslides. The deformation and failure of landslides are more likely to occur in the weak interlayer area. The failure mode of the accumulation body in the test was traction failure. It is suggested that the front part of the accumulation body can be reinforced in practical engineering. To reveal the progression of instability and movement during accumulation layer large-scale landslides, a numerical model was constructed using the material point method. The accumulation layer sliding process could be divided into three stages: acceleration sliding, deceleration sliding and stabilization. After destabilization, the river channel may be altered by the landslide mass to form a landslide dam, potentially threatening the integrity of the dam via impulse waves generated during destabilization. The research results provide technical support for reservoir scheduling in major water conservancy and hydroelectric power station reservoirs as well as engineering risk assessment and prevention.

Prediction model of outburst debris flow triggered by landslide dam failure considering the erosion process

The formation of outburst debris flow is different from other types of debris flow as it is formed by the gradual erosion of the riverbed by the unsteady and rapid outburst flow triggered by landslide dam failure. However, a prediction model for outburst debris flow that comprehensively considers the erosion effect has not yet been established. In this paper, the shallow water equation is used to describe the motion of outburst flow. This study proposes a method for constructing a virtual unit and resetting the terrain variables to reproduce the wet and dry boundary. An erosion model considering the effect of hindered erosion is introduced. By combining the shallow water equations, a debris flow prediction model that considers the entire erosion process of outburst flow is thus proposed. The established model is verified by numerical experiments on the evolution of dam-break flow on a dry fixed bed and on a moveable bed; additionally, it is verified by physical experiments on the formation of outburst debris flow. Combined with the calculation results of erosion models with and without a hindered erosion effect, the erosion model without the hindered erosion effect overestimates the flow concentration in this paper. The simulation results are closer to the actual values when considering the effect of hindered erosion in the analysis of outburst debris flow formation. The proposed model in this paper can be used as a tool to predict the occurrence of outburst debris flow.

A Statistical Risk Assessment Model of the Hazard Chain Induced by Landslides and Its Application to the Baige Landslide

Landslides are usually caused by rainstorms and geological processes such as earthquakes and may have a massive impact on human production and life. The hazard chain of landslide–river blockage–outburst flood is the most common hazard chain caused by landslides. A database based on existing landslide cases was established in this study to investigate the assessment formulas of the risk of river blockage, dam stability, and peak flood discharge after a dam has broken. A risk assessment model of the landslide–river blockage–breaching hazard chain was established, including the downstream vulnerability. The case of the Baige landslide verified the applicability of the model. This model can be used in a landslide-prone area to predict whether a relatively massive river blockage will form after the landslide occurs, whether the landslide dam formed by the river blockage will breach in a short time, and the impact of the outburst flood on the downstream area.

Multimodal multiscale characterization of cascading hazard on mountain terrain

Extreme precipitation (rain or/and snow) in upstream areas of the Himalayan region often triggers water and sediment hazards, including flash floods, landslides, debris flow, and river damming. These hazards often interact with the environmental and human systems, resulting in acute and chronic disasters that deleteriously impact the economy, infrastructure, and livelihoods. As cascading and compound hazards become more common in the Himalayan region, a more holistic approach is needed to understand the complex interaction among human, natural, and engineered systems and tackle problems connected to several system constraints. Recent catastrophes like the 2021 Melamchi disaster cannot be attributed to a single cause; rather, they result from several geomorphologic and hydroclimatic factors and physical processes. Individual and interacting dynamics and their cascading and compounding effects occurred in various settings, from high elevations to river valleys along the Melamchi River. This study diagnoses the likely causal effects of hydroclimatic processes of the 2021 Melamchi disaster by integrating space-borne remotely sensed data, hydrologic and hydrodynamic modeling, and machine learning techniques. We have evaluated several scenarios of landslide damming and breaching and analyzed flooding impacts on major settlements across the Melamchi River. Model outputs evaluated using satellite flood imagery, field-based surveys, and published reports were used to understand the characteristics of the 2021 Melamchi disaster. We find that earlier rain episodes had saturated the soil and increased the river’s water level. Therefore, after the outburst of the landslide dam coupled with heavy downpours, a sudden release of huge water had enormous energy to inundate vast areas of flood plains and damaged settlements near riverbanks far downstream up to the Melamchi Bazar. It was not just one extreme event that led to the devastation but a series of non-extreme events. This further reinforces the idea that not just extreme events, but several not-extreme series of events may lead to disaster. Thus, the chances of such a sequence of cascading events must be investigated for risk computation along with extreme events.

Laboratory-scale investigation of the material distribution characteristics of landslide dams in U-shaped valleys

Laboratory-scale investigation of the material distribution characteristics of landslide dams in U-shaped valleys

Geoinformatics-based investigation of slope failure and landslide damming of Chenab River, Lahaul-Spiti, Himachal Pradesh, India

A huge landslide blocked the flow of the Chenab River near Nalda village on the morning of 13th August 2021 in the Lahaul-Spiti district of Himachal Pradesh, which led to the flooding of several villages (Nalda, Jasrath, Tarang, etc.) in the Udaipur subdivision. The slope (∼200 ​m height, ∼220 ​m width, and approx. 30 ​m depth) on the left bank of the Chenab River failed, which brought colossal soil and debris. This resulted in the damming of the Chenab River near Leh Baring village, which lies upstream of Nalda Village Bridge and opposite to Junde village, creating a huge water reservoir that later started overflowing, posing a major threat to downstream villages. This caused damage to the houses located downstream, which were submerged, animals were also washed away, and a large part of agricultural land was also inundated. The event was observed and studied using satellite images of high-resolution obtained from Google Earth and Sentinel 2A. The Spatio-temporal satellite images were used to observe the scars developed in the region over the past few years along the river, which evidently show the early signatures of slope failure. To analyze the stability of the hill slope, the factor of safety of the hill was evaluated using SLOPE/W GeoStudio software. Slope map and drainage density map were also generated, showing the vulnerability of the hill slope. The debris flow runout simulation of the event was performed using the RAMMS debris flow model to calculate the volume of the landslide and the water reservoir formed due to damming of the Chenab River. The volume of the landslide (debris) due to slope failure was approx. 2.22 million m3 and the water reservoir volume was approximately 0.3 million m3. The significant factors accountable for the landslide i.e. the slope of the hill, geomorphology of the area, lithology (phyllites), presence of narrow and elongated valleys, the confluences of the river in the area, and continuous rainfall in the region during that period were evaluated. The paper also emphasizes monitoring of such vulnerable areas based on high-resolution time series satellite images, which are available on a regular basis to avoid the loss of human lives in the future.

Rainfall and Earthquake-induced Landslide Susceptibility Assessment

When rainfall and earthquake occur simultaneously, large-scale landslides can cause direct damage to lives and structures. To reduce such large-scale landslide damage, rainfall and earthquake-induced landslide susceptibility has to be evaluated. Therefore, in this study, landslide susceptibility was evaluated by considering only rainfall, only earthquake, and both rainfall and earthquake in the Atsuma region of Japan, where a large-scale landslide was triggered by a combination of rainfall and earthquake. Through quantitative index analysis, the accuracy of the landslide susceptibility map was improved when both rainfall and earthquake were considered. The proposed method was also applied to the Naari basin in Yangnam-myeon, Gyeongju as a pilot district. We found that the landslide-susceptible area increased when rainfall and earthquake were considered simultaneously than when rainfall and earthquake were considered separately. Through such research, can be used as basic data for complex disaster vulnerability assessment.

Integrated Approaches for Field Mapping by Traditional Investigation and Satellite PSInSAR Data: Results from the Montemartano Landslide (Central Italy)

The study presents an integrated investigation of a complex landslide based on multitemporal stereo aerial photographic interpretations, existing geotechnical monitoring data, and different PSInSAR datasets. The available information allowed for the quantification of the deformation history, also in periods with no monitoring in the field, making it possible to revise the geometry of the landslide compared to the official landslide mapping. Data from sparse inclinometers are compared with more spatially continuous satellite measurements, showing that the two monitoring techniques are consistent in terms of cumulative deformation trend and in terms of response to prolonged drought and wet periods. Therefore, reliable landslide mass displacements can be monitored using satellite products when ground instrumentations are no longer operating. Understanding the landslide behavior to rainfall conditions offers an important insight into the velocities and cumulative displacements expected during similar stages of enhanced landslide activity. The findings can be helpful to support urban planners in re-evaluating hazard and risk classification and implementing efficient mitigation techniques to reduce landslide damage.

Primary and potential secondary risks of landslide outburst floods

Outburst floods triggered by breaching of landslide dams may cause severe loss of life and property downstream. Accurate identification and assessment of such floods, especially when leading to secondary impacts, are critical. In 2018, the Baige landslide in the Tibetan Plateau twice blocked the Jinsha River, eventually resulting in a severe outburst flood. The Baige landslide remains active, and it is possible that a breach happens again. Based on numerical simulation using a hydrodynamic model, remote sensing, and field investigation, we reproduce the outburst flood process and assess the hazard associated with future floods. The results show that the hydrodynamic model could accurately simulate the outburst flood process, with overall accuracy and Kappa accuracy for the flood extent of 0.956 and 0.911. Three future dam break scenarios were considered with landslide dams of heights 30 m, 35 m, and 51 m. The potential storage capacity and length of upstream flow back up in the upstream valley for these heights were 142 × 106m3/32 km, 182 × 106m3/40 km, and 331 × 106m3/50 km. Failure of these three dams leads to maximum inundation extents of 0.18 km2, 0.34 km2, and 0.43 km2, which is significant out-of-bank flow and serious infrastructure impacts. These results demonstrate the seriousness of secondary hazards associated with this region.

Quantitative assessment on landslide dam risks and mitigation: an in-depth study on the Baige lake breach

Quantitative assessment on landslide dam risks and mitigation: an in-depth study on the Baige lake breach

Reconstruction of a Holocene landslide-dammed lake in the Yalong basin, eastern Tibetan Plateau

The failures of natural dams formed by landslides and glaciers in mountain areas have triggered the most destructive flood events on Earth. Outburst floods are effective agents in modifying landscapes, such as carving bedrock gorges and transporting surface masses. Reconstructing the ages and magnitudes of prehistoric landslide damming events allows us to capture the full range of frequencies and magnitudes of similar events and deepen our understanding of the interaction between large landslides and trunk rivers in tectonically active high-relief mountains. Previous studies have revealed many paleo-landslide-dammed lakes in the Yarlung Tsangpo River and its tributaries, the Jinsha River and the Min River. However, most studies associated with paleo-event reconstruction lack an estimation of the extent and volume of paleo-landslide-dammed lakes. The paleo-level of a landslide-dammed lake can be recorded in the variation in the sedimentary sequence and the geometry of the breach channel of a landslide dam. This information has not been fully exploited. In this study, we identified sedimentary evidence formed by an ancient landslide-dammed lake in the Liqiu River, a left-bank tributary of the Yalong River. The 12 exposures that we investigated mainly consist of typical clay or silt varves deposited in deep water and the Bouma sequence deposited by subaqueous turbidity flows, as well as climbing ripples that formed in a near-shore environment. Based on sedimentary analysis, we inferred that the minimal lake volume of this ancient lake was approximately 2.4 × 108 m3, corresponding to a lake level at 3,187 m a.s.l. The maximal lake extent derived from relict dam morphology reveals a lake volume of 3.2 × 108 m3 at the level of 3,200 m a.s.l. An initial drainage that occurred as the lake water overtopped the landslide dam was suggested to explain the small discrepancy in the lake level. The relict lake has remained stable over a long period of time and has accommodated continuous clay varve deposits. Furthermore, the optically stimulated luminescence dating results illustrate that the dammed lake initiated before 7.9 ka BP and persisted until at least 3.9 ka BP. The long-term cumulative coupled effect of tectonic movement and the rapid river incision rate provided favorable conditions for the failure of the Yuting landslide.

Centrifugal model tests and numerical modeling on overtopping-induced breach processes of landslide dams

This study used the 400 g-ton geotechnical centrifuge model test system at the Nanjing Hydraulic Research Institute (NHRI) to investigate the breach evolution characteristics and hydrograph process of overtopping-induced breaching of landslide dams. It was achieved by taking advantage of the “time-space amplification” effect created by high-speed rotation using a centrifuge overweight force field. The effects of dam height, slope ratio, and soil gradation on the overtopping failure process of landslide dams were investigated by centrifugal model tests for the first time. In addition, a detailed physically-based dam breach model was developed to simulate the overtopping failure of landslide dams. Results show that the breach process of a landslide dam can be divided into four stages based on the measured breach morphology evolution process and the abrupt variations of breach flow discharge: initial scour on the downstream slope, retrogressive erosion to the dammed lake, erosion along the breach channel, and breach stabilization. Moreover, the peak breach flow is most sensitive to the dam height, followed by the average particle size; the time to peak is mainly affected by the slope ratio, and the relative residual dam height is primarily susceptible to the average particle size. In practice, the calculated results are consistent with the measured results. This study provides a scientific reference for the cognition of the overtopping-induced breach mechanism of landslide dams.

Ground Investigations and Detection and Monitoring of Landslides Using SAR Interferometry in Gangtok, Sikkim Himalaya

The Himalayan state of Sikkim is prone to some of the world’s largest landslides, which have caused catastrophic damage to lives, properties, and infrastructures in the region. The settlements along the steep valley sides are particularly subject to frequent rainfall-triggered landslide events during the monsoon season. The region has also experienced smaller rock slope failures (RSF) after the 2011 Sikkim earthquake. The surface displacement field is a critical observable for determining landslide depth and constraining failure mechanisms to develop effective mitigation techniques that minimise landslide damage. In the present study, the persistent scatterers InSAR (PSI) method is employed to process the series of Sentinel 1-A/B synthetic aperture radar (SAR) images acquired between 2015 and 2021 along ascending and descending orbits for the selected areas in Gangtok, Sikkim, to detect potentially active, landslide-prone areas. InSAR-derived ground surface displacements and their spatio-temporal evolutions are combined with field investigations to better understand the state of activity and landslide risk assessment. Field investigations confirm the ongoing ground surface displacements revealed by the InSAR results. Some urban areas have been completely abandoned due to the structural damage to residential housing, schools, and office buildings caused by displacement. This paper relates the geotechnical investigations carried out on the ground to the data obtained through interferometric synthetic aperture radar (InSAR), focusing on the triggering mechanisms. A strong correlation between seasonal rainfall and landslide acceleration, as well as predisposing geological-structural setting, suggest a causative mechanism of the landslides.

Residual electron spin resonance signals of quartz from the 2018 Baige dammed lake in Tibet: Implications for the identification of sediment layers caused by megafloods

Residual doses may cause overestimation of electron spin resonance (ESR) ages for fluvial sediments. However, ESR residual doses in outburst megaflood sediments have rarely been evaluated. The Jinsha River, situated in the southeastern Tibetan Plateau, is characterized by active faults, narrowed canyons, and dammed lakes. Consequently, the river is a rare opportunity for a reconstruction study of outburst flood events from a paleo-dammed lake. After the destruction of the Baige dammed lake in the upper Jinsha River in 2018, outburst megafloods formed a thick diluvium that was deposited in broad valley land along the lower Jinsha River. Based on detailed field investigation and laboratory studies, preliminary hydraulics estimates and residual quartz ESR signals indicate the following. 1) Among the multiple quartz ESR centers, the Al, E1ʹ, Ti-H, and Ti-Li centers could be measured. The Ti-H center had the lowest residual dose and would provide relatively accurate ages for outburst megaflood sediment. 2) The Ti-Li and Al centers commonly used for ESR dating provide overestimates of 283 ± 42 ka ∼ 462 ± 63 ka and 1,010 ± 88 ka ∼ 1,400 ± 219 ka, respectively, for present outburst megaflood sediment. 3) The diverse ages given by the same ESR signal may be caused by various precursors of megaflood sediments, which are mainly sourced from landslide dams and from various terraces and slope sediments along the river. Results demonstrated that the apparent ESR ages observed for the outburst megaflood sediment in the southeastern Tibetan Plateau may be counterfeit, providing an age much older than its real age. This could be interpreted to mean that the narrowed lower channel makes the upper reaches of the broad valley appear lake-like, with diluvium deposits having large non-negligible residual ESR signals without enough exposure to adequate sunlight, despite having good stratification and sorting characteristics similar to those of fluvio-lacustrine sediments. Thus, abrupt reversal in quartz ESR ages in multiple centers observed in the geochronological framework of the fluvial sedimentary profile may indicate a diluvial or flood layer in the absence of other inducements.

Review on risk assessments of dammed lakes

As one type of natural disaster, dammed lakes pose a serious threat to the safety of lives and properties downstream. Scientific risk assessments of dammed lakes are key for pre-disaster prevention and post-disaster rescue. However, due to the lack of basic information and uncertainty surrounding materials and loads, risk assessments of dammed lakes are more complex than those of artificial reservoir dams, and comprehensive assessment methods are lacking. Based on the evolution of dammed lake hazard chains, starting with the concept of a dammed lake risk assessment, this paper focused on six aspects: worldwide dammed lake databases, hazard assessments for landslide dams, breach mechanisms and breach processes, flood routing after landslide dam breaching, loss assessments, and risk mitigation measures. A comprehensive review was conducted on the qualitative and quantitative risk assessment methods around the world, as well as future outlooks.

Селевая активность и особенности селеформирования в долине р. Гейзерной (камчатка)

A map of debris flow activity of the Geysernaya river basin, where large-scale debris flow processes associated with the collapse of fragments of the left side of the valley have been observed three times over the past 40 years, was compiled. Three independent debris flow areas of the river basin have been identified and characterized: the upper reaches of the river — the Levaya Geysernaya basin, the middle river course — below the dammed lake formed in 2014, and the lower downstream part — below the dammed lake that existed in 2007–2014. It was found that debris flow processes are typical for most of the Geysernaya river tributaries. Moreover, in the left tributaries debris flows may have aseasonal character, because they are formed in conditions of constant heating and active gas-hydrothermal influence within the thermal fields. The landslide dam formed in 2014 is resistant to erosion, and an independent breakthrough of the dammed lake is unlikely. With further erosion of the 2007 dam and the expansion of the breach in the dam body, collapse of its sides and debris flow in the lower part of the Geysernaya river valley cannot be ruled out. Risks of rockfall, landslide and debris flow processes, the initiation of which is most likely on the left side of the valley, should be considered in planning the development of recreational facilities.

Long-term monitoring of sediment runoff for an active sediment control in Joganji River

There were huge sediment yielding and deposition due to debris flows by breaking natural landslide dams which were formed by earthquake in 1858 at upstream reach of Joganji River. Sediment transportation is still active by debris flow and flow with bedload due to rainfall, though a lot of erosion control dams have been constructed. Continuously measuring sediment runoff for long term along a main river is necessary to evaluate the propagation of sediment after the huge events for sediment management in the basin using well hydrological information. Appropriate tools are selected and applied to monitoring in the area managed by Tateyama Mountain Area Sabo Office along Joganji River, using a Reid-type bedload slot sampler, robust-type hydrophone and velocity meter on the bed for bedload and turbidity meter for washload. Monitored data is concentratedly collected at the office to apply risk management for sediment movement due to heavy rainfall and so on. Several typical data and problems to solved were shown because it passed around twenty years since sediment monitoring started, and those are reported in present study.

Life span of a landslide dam on mountain valley caught on seismic signals and its possible early warningsの紹介

Life span of a landslide dam on mountain valley caught on seismic signals and its possible early warningsの紹介