Location of the study area.
(a) DEM image of the TGR. The inset shows the location of the landslide in China.
(b) UAV image of the landslide.
(c)–(e) Surface deformation signs of the landslide.

Chinese Researchers Harness InSAR and Simulation to Decode Landslides, Offering Global Solutions to Geological Hazards

A groundbreaking study from China is revolutionizing how scientists analyze and mitigate landslides worldwide. Researchers at Central South University have combined advanced Interferometric Synthetic Aperture Radar (InSAR) technology with numerical simulations to unravel the complex mechanisms behind the Shuizhuyuan landslide in the Three Gorges Reservoir area. Their innovative approach offers a blueprint for understanding and managing landslides in diverse regions across the globe.

The study, published in a leading geosciences journal, leverages InSAR to track surface deformation at millimeter precision. By combining this with fluid–solid coupling simulations, the team uncovered how rainfall infiltration, fluctuating reservoir water levels, and seepage forces contribute to slope instability. The research revealed distinct patterns of deformation and identified water-level drops as the primary trigger for progressive failure, insights that could transform landslide risk assessments in reservoir, coastal, and mountainous regions alike.

“This study represents a milestone in using technology to monitor and predict landslides,” said Dr. Guoshi Liu, the study's lead author. “Our findings don’t just apply to China—they can help protect communities living in landslide-prone areas worldwide.”

The Shuizhuyuan landslide, located in the Three Gorges Reservoir—a site notorious for geological instability—served as a testbed for the research. By integrating InSAR observations and numerical modeling, the study not only mapped real-time deformation but also predicted future stability under varying hydrological conditions.

The implications are vast. In the United States, coastal landslides in places like Rolling Hills, California, and reservoir-triggered landslides in Hoover Dam areas could benefit from these methods. Similarly, regions like the Western Ghats in India or the Andes in South America, plagued by rainfall-induced landslides, stand to gain from these technologies.

“Reservoir-induced landslides, such as Italy’s Vaiont disaster or Brazil’s mining-related failures, share striking similarities with Shuizhuyuan. This research equips us with tools to better understand and prevent such catastrophes,” said Dr. Bin Wang, a co-author of the study.

Beyond disaster mitigation, the research holds promise for urban planning and infrastructure development in landslide-prone regions. By modeling the interaction between water infiltration, slope stress, and deformation, engineers can design safer structures and implement more effective early-warning systems.

The Shuizhuyuan study underscores the growing role of technology in tackling environmental challenges. With climate change intensifying rainfall patterns and increasing landslide risks, this pioneering work highlights the importance of global collaboration in safeguarding communities from geological hazards.

“This is not just a breakthrough for China,” Dr. Liu emphasized. “It’s a step toward a safer world.”

New Insights Into the Reservoir Landslide Deformation Mechanism From InSAR and Numerical Simulation Technology | IEEE Journals & Magazine | IEEE Xplore

G. Liu et al., "New Insights Into the Reservoir Landslide Deformation Mechanism From InSAR and Numerical Simulation Technology," in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 18, pp. 2908-2927, 2025, doi: 10.1109/JSTARS.2024.3523294.

Abstract: Reservoir landslides represent a significant geological hazard that jeopardizes the safety of reservoirs. Deformation monitoring and numerical simulation are essential methodologies for elucidating the evolutionary patterns of landslides. Nonetheless, the existing approaches exhibit limitations in revealing the potential deformation mechanism. Consequently, this study proposes an innovative strategy that incorporates interferometric synthetic aperture radar (InSAR) deformation characteristics alongside fluid–solid coupling stress analysis to investigate the deformation, focusing on the Shuizhuyuan landslide within the Three Gorges Reservoir area as a case study. Using temporary coherence point InSAR technology, significant motion units were identified, with a maximum deformation rate of −60 mm/yr. The complete deformation time series reveals three independent components of landslide movement and their trigger factors geometrically. Subsequently, the saturation permeability coefficient of the sliding mass in the seepage analysis is modified with the assistance of InSAR deformation. Then, we coupled the seepage analysis results to FLAC3D model for stress and strain analysis, and determined the seepage-induced progressive failure mechanism and the deformation mode of the Shuizhuyuan landslide, driven by reservoir water-level (RWL) drop. The numerical simulation results aid in interpreting the deformation mechanism of different spatial and temporal patterns of landslides from three aspects: hydrodynamic pressure from rainfall infiltration, groundwater hysteresis caused by RWL drop, and seepage forces from RWL rise. Furthermore, our findings reveal that the dynamic factor of safety (FOS) of landslide during the InSAR observation period is highly consistent with the periodic fluctuations of the RWL. However, there is also a small trend of overall decline in FOS that cannot be ignored.

keywords: {Terrain factors;Deformation;Reservoirs;Geology;Monitoring;Numerical simulation;Stress;Stability analysis;Soil;Permeability;Deformation mechanism;fluid–solid coupling analysis;independent component analysis (ICA);interferometric synthetic aperture radar (InSAR);numerical simulation;Shuizhuyuan landslide},

URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10817503&isnumber=10766875

Background of the study:
This study focuses on investigating the deformation mechanism of the Shuizhuyuan landslide, which is located in the Three Gorges Reservoir area in China. The Shuizhuyuan landslide is a large landslide that has been reactivated by the impoundment of the Three Gorges Reservoir. The researchers aim to understand the spatial and temporal patterns of deformation, as well as the potential failure modes and triggering mechanisms of this landslide.

Research objectives and hypotheses:
The main objectives of this study are:

To use interferometric synthetic aperture radar (InSAR) technology to reconstruct the deformation field of the Shuizhuyuan landslide and identify the spatial and temporal patterns of deformation.
To analyze the triggering factors related to the independent components of deformation using independent component analysis (ICA).
To modify the saturation permeability coefficient of the sliding mass based on the InSAR deformation time series and perform fluid-solid coupling analysis to investigate the deformation mechanisms of the landslide.

Methodology:

InSAR analysis: The researchers used the temporary coherence point (TCP) InSAR method to reconstruct the deformation field of the Shuizhuyuan landslide. They also employed ICA to analyze the triggering factors related to the independent components of deformation.
Fluid-solid coupling analysis: The researchers modified the saturation permeability coefficient of the sliding mass based on the InSAR deformation time series. They then performed seepage analysis and coupled the results with a FLAC3D model for stress-strain analysis to investigate the deformation mechanisms of the landslide.

Results and findings:

The InSAR analysis detected significant deformation in the front, middle, and trailing edge of the Shuizhuyuan landslide, with a maximum deformation rate of -60 mm/year.
The ICA analysis identified three independent components of deformation, which were related to different triggering factors: rainfall, reservoir water level (RWL) fluctuations, and RWL drop.
The fluid-solid coupling analysis revealed that the primary driver of deformation and instability at the slope toe is the drop in RWL, which induces hydrodynamic pressure and reduces the stability of the landslide.

The Shuizhuyuan landslide in the Three Gorges Reservoir (TGR) area of China

The Shuizhuyuan landslide is a significant geological hazard located on the north bank of the Yangtze River in the Three Gorges Reservoir (TGR) area of China, near Quchi Township, Wushan County, Chongqing City. Here are key details about the landslide:

Geological Characteristics:

Size and Structure:
- Length: ~800 meters.
- Width: 360–1200 meters.
- Thickness: ~30 meters.
- Total Volume: ~1850 × 10⁴ m³.
- Area: ~62 × 10⁴ m².
Geology:
- It is an accumulative landslide with the sliding mass composed of colluvial deposits (Q₄) and gravelly silty clay.
- Bedrock consists of Triassic and Jurassic strata, mainly marl (T₂b).

Triggers and Influences:

Reservoir-Induced Effects:
- The impoundment of the Three Gorges Reservoir since 2003 has contributed to strain softening at the slope toe.
- Periodic fluctuations in reservoir water levels (FRWL) significantly impact stability.
Rainfall:
- Heavy rainfall exacerbates hydrodynamic pressures, leading to surface water infiltration and destabilization.

Deformation and Failure Patterns:

Observed Deformation:
- InSAR technology revealed significant deformation at the landslide’s front, middle, and trailing edges, with rates reaching up to −60 mm/year.
- The deformation exhibits continuous, periodic, and stepwise patterns.
Failure Mode:
- The landslide shows traction-progressive failure along a circular arc sliding surface.
- Failure is primarily driven by seepage effects, hydrodynamic pressure during reservoir water-level drops, and groundwater hysteresis.

Hazards and Risks:

The landslide poses a threat to shipping on the Yangtze River due to its proximity and potential for sudden failure.
Stability analyses indicate that rapid reservoir water-level drops significantly decrease the Factor of Safety (FOS), increasing failure risks.

Research and Monitoring:

Technologies Used:
- InSAR for detailed spatiotemporal deformation monitoring.
- Numerical simulations, including fluid–solid coupling and stress-strain analysis, to understand deformation mechanisms.
Findings:
- Stability is highly sensitive to reservoir water-level changes.
- Rainfall primarily influences the trailing edge and middle sections, while FRWL impacts the toe.

Other Applicable Landslides

The research on the Shuizhuyuan landslide in the Three Gorges Reservoir provides insights that can be applied to other reservoir-induced or hydrologically driven landslides worldwide. Below are some examples of landslide-prone regions where similar mechanisms and mitigation strategies might be relevant:

1. Reservoir-Triggered Landslides

These are landslides influenced by water-level fluctuations in reservoirs, akin to the Shuizhuyuan case.

Vaiont Landslide, Italy (1963):
- A catastrophic landslide triggered by rapid reservoir filling caused a massive wave that overtopped the dam, leading to over 2,000 deaths.
- Mechanisms: Water infiltration weakened rock and increased pore pressure.
- Relevance: Numerical modeling and monitoring methods, like those used in Shuizhuyuan, could help analyze deformation and improve safety in similar settings.
Hoover Dam Area, USA:
- Reservoir-induced stress changes have caused slope failures along the Colorado River.
- Monitoring reservoir fluctuations using InSAR and modeling pore pressure changes can prevent instability.

2. Rainfall-Induced Landslides

Regions with heavy seasonal rainfall face landslides caused by infiltration and saturation.

Western Ghats, India:
- Heavy monsoon rains often cause large-scale landslides.
- Relevance: The InSAR and fluid–solid coupling techniques used in the Shuizhuyuan study can model the impact of rainfall infiltration on slope stability.
Petropolis, Brazil (2022):
- Intense rainfalls triggered deadly landslides in mountainous areas.
- Using InSAR for early detection of deformation and modeling infiltration effects could aid in disaster mitigation.

3. Glacier-Dammed or Periglacial Landslides

Water levels behind glaciers or in glacial lakes can cause destabilization of slopes.

Seti River Landslide, Nepal (2012):
- Triggered by glacier-lake outbursts and water infiltration.
- Relevance: The techniques for studying reservoir water-level fluctuations and seepage-induced deformation can also apply here.
Denali National Park, USA:
- Periglacial landslides caused by melting ice and hydrological shifts.
- Monitoring deformation with high spatial resolution, as with InSAR, can provide insights.

4. Hydropower-Influenced Landslides

Hydropower reservoirs often face challenges due to fluctuating water levels and associated instability.

Laxiwa Hydropower Station, China:
- Landslides triggered by seepage and water-level changes in the Yellow River Basin.
- The study's fluid–solid coupling analysis is directly applicable for assessing slope stability under similar conditions.
Baihetan Dam, China:
- Landslides in the reservoir area are driven by seepage and saturation of slopes.
- Combining InSAR deformation monitoring with stress-strain numerical modeling could improve predictions.

5. Coastal and Riverine Landslides

Areas with fluctuating water levels due to tides or river flows also experience landslides.

Malibu, California, USA:
- Coastal cliffs fail due to wave erosion and fluctuating groundwater levels.
- The dynamic response modeling of Shuizhuyuan can help understand slope stability under these conditions.
Yangtze River Tributaries, China:
- Riverbank failures due to water-level changes from seasonal flows and rainfall.
- Applying deformation monitoring and seepage simulations could enhance stability assessments.

6. Mining and Artificial Reservoir-Triggered Landslides

Man-made water bodies and mining pits often experience instability due to changing hydrology.

Chuquicamata Mine, Chile:
- Open-pit mines face slope instability due to water infiltration and altered stress fields.
- The study’s techniques can analyze seepage effects and failure mechanisms.
Brumadinho Dam Disaster, Brazil (2019):
- Although triggered by dam failure, subsequent landslides were influenced by water-saturated soil.
- Similar modeling approaches could help in future risk assessments.

Global Relevance

This research provides a methodology for combining InSAR monitoring and numerical simulations to analyze deformation mechanisms under varying hydrological conditions. It is particularly useful for:

Regions with reservoirs, hydropower projects, or large dams.
Areas prone to rainfall-triggered or seepage-induced landslides.
Environments with slow-moving, deep-seated landslides where long-term monitoring is critical.

By adapting these methods, researchers and authorities worldwide can better assess and mitigate landslide risks.

Rolling Hills

The methods and insights from the Shuizhuyuan landslide study can apply to coastal landslides like those in the Rolling Hills area of Los Angeles, California, though with some adaptation for local conditions. Here’s how:

Common Features

Hydrological Triggers:
- Coastal landslides are influenced by water infiltration from rainfall, groundwater fluctuations, and, in some cases, wave action. The Shuizhuyuan study highlights how rainfall and water-level changes contribute to instability, which aligns with the mechanisms at play in Rolling Hills.
Slope Deformation:
- Coastal landslides often involve slow, progressive deformation before failure, similar to the progressive traction deformation identified in Shuizhuyuan.
Pore Pressure and Seepage:
- Seepage forces and pore pressure dynamics are significant in coastal slopes, particularly where saturated soils overlay impermeable bedrock, as in many areas of Rolling Hills.

Application of Shuizhuyuan Methods

InSAR Monitoring:
- InSAR can be used to track surface deformation over time in Rolling Hills. The high spatial resolution of InSAR allows for early detection of movement, helping predict failure before it occurs.
Numerical Simulations:
- Fluid–Solid Coupling: Simulations that model the interactions between pore pressure, rainfall infiltration, and slope stability are directly applicable to Rolling Hills. This can help understand the role of hydrology in driving deformation.
- Stress-Strain Analysis: Modeling the stress changes from water infiltration and soil weight, as done for Shuizhuyuan, could provide insights into the potential for progressive failure.
Trigger Analysis:
- The Shuizhuyuan study's approach to analyzing the impact of rainfall and groundwater level changes on deformation could be applied to assess the influence of rainfall intensity, coastal erosion, and potential groundwater drawdown in Rolling Hills.
Failure Mode Prediction:
- The traction-progressive failure mode observed in Shuizhuyuan may also be relevant to Rolling Hills, where coastal cliffs and slopes often fail along circular or planar slip surfaces.

Unique Considerations for Rolling Hills

Wave Action:
- Unlike reservoir landslides, coastal slopes in Rolling Hills are subject to wave erosion at the base, which exacerbates instability. Incorporating wave loading into numerical simulations would be necessary.
Geological Composition:
- The Rolling Hills area is characterized by weak sedimentary formations, such as shale and sandstone, which are prone to weathering and erosion. This requires fine-tuning material properties in models.
Urban Development:
- Rolling Hills is heavily urbanized, meaning human activities like irrigation, septic systems, and road drainage can significantly impact groundwater levels and slope stability.
Tidal Effects:
- Coastal slopes experience periodic fluctuations in stress due to tidal changes, which might need to be modeled alongside rainfall and seepage forces.

Potential Benefits

Early Warning Systems: InSAR data combined with real-time rainfall and groundwater monitoring could help establish thresholds for landslide warnings.
Improved Risk Assessment: Numerical models incorporating both rainfall and coastal dynamics could enhance the prediction of failure timing and magnitude.
Informed Mitigation: Insights into deformation mechanisms could guide engineering solutions, such as drainage systems or slope reinforcements, tailored to local conditions.

By adapting the Shuizhuyuan study's methods to include coastal-specific factors like wave erosion and tidal effects, researchers and engineers can better understand and mitigate landslide risks in areas like Rolling Hills, Los Angeles.

Prevention and Mitigation:

Risk management efforts emphasize the importance of monitoring water-level fluctuations and implementing early-warning systems to mitigate disaster risks.

The Shuizhuyuan landslide exemplifies the challenges posed by large reservoir systems in landslide-prone areas, highlighting the need for advanced monitoring and preventive strategies.

Discussion and interpretation:

The hydrodynamic pressure caused by rainfall infiltration and the sliding force resulting from increasing soil weight are the driving factors of deformation at the middle and trailing edge of the landslide.
The groundwater hysteresis caused by the drop in RWL is the primary mechanical mechanism driving deformation at the toe of the landslide.
The seepage force from rising RWL and the counterpressure effect of hydrostatic pressure contribute to the elastic deformation of the landslide.

Contributions to the field:
This study provides a new approach to investigate the deformation mechanism of reservoir landslides by integrating InSAR deformation characteristics and fluid-solid coupling analysis. The findings offer valuable insights into the complex deformation patterns and triggering mechanisms of the Shuizhuyuan landslide.

Achievements and significance:
The study successfully identified the spatial and temporal patterns of deformation, as well as the key triggering factors, for the Shuizhuyuan landslide. The fluid-solid coupling analysis also provided a detailed understanding of the mechanical mechanisms driving the deformation of the landslide, which is crucial for developing effective prevention and mitigation strategies.

Limitations and future work:

The study focuses on a specific landslide, and the findings may not be directly applicable to other reservoir landslides with different geological and hydrological conditions.
The accuracy of the numerical simulation results depends on the reliability of the input parameters, such as the saturation permeability coefficient, which can be challenging to measure accurately due to the spatial heterogeneity of the sliding mass.
Future research could explore the integration of additional monitoring data, such as GNSS and groundwater level measurements, to further validate and refine the deformation mechanisms proposed in this study.

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Tuesday, January 21, 2025