This study investigates flow resistance models for debris flow simulations based on 2D shallow water equations. With an aim of reproducing the catastrophic debris flow disaster that occurred in Atami City, Japan, in 2021, three flow resistance models are evaluated to capture the flow and deposition characteristics of debris flows. A preliminary parameter study is conducted to calibrate two critical empirical parameters: Manning roughness coefficient and the internal friction angle, by comparing simulation results with experimental data reported in the literature. The calibrated models and their parameter combinations are then subsequently applied to the actual debris flow disaster in Atami City. Their applicability is discussed through comparison of simulation results with post-disaster survey data. The findings indicate that the combined turbulent and frictional resistance model demonstrates superior performance in replicating both the flow and deposition characteristics of the debris flow. However, further refinement is required to fully account for the complex interactions observed during the actual event. Additionally, this study provides insights into valid parameter ranges for specific flow resistance models, contributing to more intuitive debris flow simulations.

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