Scenario-Based Assessment of Material and Hydrological Controls on Attabad Landslide Dam Stability

Landslide-dammed lakes are natural barriers formed by slope failures that can cause serious hazards downstream. Their stability depends on both dam shape and material and on the upstream hydrological conditions that control lake extension and water level. Changes in these conditions can increase lake level and activate hydraulic processes like seepage and overtopping, which can compromise the stability of dam. Understanding the interplay of upstream hydrology and stability is important to assess dam safety and downstream flood risk.

In early 2010, a rockslide in Attabad created a dam on the Hunza River in Pakistan, forming a lake that still exists today. In this study, lake surface area and volume were assessed using Landsat images and the Normalized Difference Water Index (NDWI), and pre-lake digital elevation model was used to estimate lake volume changes. Observations show seasonal fluctuations and consistency in lake volume over the years, influenced by spillway excavations and other hydrological processes.

A simplified geometry of dam body was defined based on literature data and images. Grain size distribution of dam materials typical of rockslides was also analyzed, and the Hazen formula was used to estimate hydraulic conductivity values. These were applied in GeoStudio SEEP/W to simulate nine scenarios with different combinations of clay and gravel permeability. Results show that total seepage (under current conditions) is moderate but strongly depends on material properties. Gravel-dominated zones have higher seepage, while clay-dominated zones have lower seepage. Some gravel areas could be prone to localized internal erosion or piping under high water levels.

We also analyze dam’s stability under different hydrological conditions. One approach is to evaluate seepage and structural response using current lake water level, which can help back-analyze and validate the mechanical properties of the dam materials. The second approach is to simulate future possible water levels to assess whether the dam remains stable under extreme conditions.

This study shows that combining remote sensing and hydrological modelling allows developing scenario-based analyses that can help understand how hydrology and dam material and shape control its stability. It provides a useful approach for monitoring and managing landslide-dammed lakes in areas with limited field data.

Keywords: Landslide dams, hydrological modeling, dam stability, scenario-based analysis, remote sensing