Deep critical zone controls on shallow landslides.

Area of Science:

• Geosciences
• Hydrology
• Geotechnical Engineering

Background:

• The deep critical zone (CZ) is crucial for shallow landslide dynamics but often excluded from watershed-scale models.
• Previous models struggled to incorporate deep CZ influences on slope stability.

Purpose of the Study:

• To demonstrate the feasibility of approximating deep CZ structures in coupled hydrologic and slope stability models.
• To improve the prediction of shallow landslide location, timing, and magnitude at the watershed scale.

Main Methods:

• Utilized coupled, process-based models integrating deep CZ structures, 3D transient hydrology, and multidimensional slope stability.
• Calibrated models using data from an intensively monitored field site.

Main Results:

• Deep, conductive CZ structures effectively guide groundwater flow, controlling soil saturation and seepage forces.
• The presence of deep, weathered bedrock reduces pore pressures, localizing instability and leading to similar landslide sizes.
• Absence of conductive bedrock results in widespread pore pressures, larger landslides, and earlier storm-induced failures.

Conclusions:

• First-order variations in deep CZs explain observed differences in shallow landslide susceptibility, magnitude, and timing.
• CZ structure can potentially be inferred from landsliding patterns and timing.