RESPONSES OF BED MORPHOLOGY TO LARGE WOOD DEPOSITION USING A COMPUTATIONAL HYDRODYNAMIC MODEL

This study develops a numerical model for large wood dynamics in a braided river considering the root wad effect and anisotropic bed friction. The newly developed numerical model can precisely simulate the behavior of large pieces of wood using a 2-dimensional depth-averaged Eulerian flow model that calculates the water flow and bed morphology. We developed a Lagrange-type wood transport model and combined with the flow model, and the applicability of the combined model is examined in a comparison with experimental results. From the simulation results, we quantitatively calculate the Active Braiding Index (ABI), Bed Relief Index (BRI), and averaged values of deposition position and deposition angle. We then analyze the relationship between the bed morphology responses and the wood deposition patterns in terms of the root wad effect and input supply. The proposed model reproduces the prominent features of the flume experiment, indicating that the present numerical approach can clarify and predict the behavior of large pieces of wood in accordance with the bed morphology.