Assessment of physical parameters impacts on debris flow modeling with RAMMS

Area of Science:

• Geosciences
• Computational modeling
• Natural hazard analysis

Background:

• The Rapid Mass Movement Simulation (RAMMS) model is crucial for debris flow analysis.
• Accurate input data is essential for reliable RAMMS outputs.
• Understanding input parameter uncertainties is key to improving debris flow simulations.

Purpose of the Study:

• To evaluate the impact of various input data uncertainties on RAMMS outputs.
• To quantify the sensitivity of debris flow simulations to DEM resolution, friction coefficients, inflow direction, and terrain curvature.

Main Methods:

• A real debris flow event was simulated using the RAMMS model.
• Scenarios were created by varying DEM cell sizes (1-20m), Voellmy-fluid friction coefficients (Dry-Coulomb µ and viscous-turbulent [Formula: see text]), inflow directions (±50 degrees), and terrain curvature.
• Model outputs were analyzed to assess the influence of each parameter variation.

Main Results:

• Increasing DEM cell size drastically reduced output accuracy, with up to 724% increase in inundation area error for 20m cells compared to 1m.
• The Dry-Coulomb friction coefficient (µ) had a more significant impact on results than the viscous-turbulent coefficient ([Formula: see text]).
• Terrain curvature and inflow direction variations showed minor effects on the overall simulation results.

Conclusions:

• High-resolution DEM data is critical for accurate debris flow simulations using RAMMS.
• Friction parameters are key drivers of simulation outcomes, necessitating careful calibration.
• Model sensitivity to terrain curvature and inflow direction is relatively low, suggesting these parameters may be less critical for broad-scale analysis.