Unlike general landslides, debris flow has a high water content, due to large floods and rainfall. On steep slopes, it behaves like a large specific-weight sediment–water mixture, rather than general fluid. Thus, its momentum rapidly increases, damaging human lives and properties. This study developed a numerical model of debris flow considering driftwood and entrainment erosion, and performed numerical simulations based on the 2011 observation data of Mt. Umyeon. To develop the debris-flow model, the Nays2DFlood model, which is a flooding model based on the shallow-water equation, was coupled with the advection and diffusion of the sediment–water mixture, debris-flow bottom shear-stress, and entrainment-erosion modules. The simulation better reproduced the depth, flow velocity, and debris-flow volume of Mt. Umyeon. In particular, the driftwood generation and motions, by debris flow, were well demonstrated in the numerical simulation. Moreover, the driftwood partially reduced the drag force, and the shielding effect of the forest caused a delay in the runoff duration-time. The results of this study are expected to help establish measures to reduce debris disasters that can respond to the current situation, wherein debris damage is increasing, owing to the increased rainfall because of climate change. This subsequently increases the possibility of debris flows and the consequent damage. In particular, the predictive methodology of the refined model expands the understanding of numerical treatment for debris flow and driftwood, by reflecting the detailed physical regime.

This study aims to experimentally and numerically investigate the fluvial processes of channels disturbed through sand or gravel mining. A two-dimensional numerical model is applied to simulate flume experiments. A moving boundary-fitted coordinate system is used to describe the channel changes. As a numerical scheme, the cubic interpolated pseudoparticle method is used to calculate the flow field and bed changes, which introduces little numerical diffusion. The numerical model is verified with experimental data. The inflow sediment from the upstream is trapped into a pit and the sediment deposit wedge migrated to the downstream with a steep submerged angle of repose. The numerical and experimental results show that the sediment deposit wedge in the pit migrates to the downstream under the condition of steady state. The adjustment time within the disturbed channels increases as the dimension of the pit is increased. The sediment mining pit migrates with speed in the steep channel. Moreover, the numerical experiments show that the migration speed is proportional to the sediment inflow. And the disturbed channels by the sediment mining are affected by the sediment inflow conditions of the upstream and adjusted to the new state of equilibrium.

Jon-Lark Kim, Jae-Hyun Baek, Keon-Hwi Kim, Tae Hyo Baek, and Chang-Lae Jang. International Journal of Fuzzy Logic and Intelligent Systems 2026;26:10-9. https://doi.org/10.5391/IJFIS.2026.26.1.10