In this study, laboratory experiments were conducted to observe drifting of objects transported by a tsunami. Tsunami-induced drift motion was simulated using various numerical models, and the results were compared. Experiments were performed with and without obstacles in the terrain, and the differences were assessed. The spread of debris occurred faster in the presence of an obstacle. In the absence of structures in the flow, the debris did not shift perpendicular to the flow direction in any of the numerical models. The experimental results were generally consistent with the calculated results, although they varied in a normally distributed manner. However, when there was a downstream structure, the uncertainty of the drift motion was not accurately simulated. Furthermore, it was observed that debris moved behind obstacles. A numerical model that calculated the collision force between debris using momentum conservation reproduced this phenomenon. Thus, the numerical model with the drag and inertia coefficients was fairly accurate.

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