Development and application of a two-dimensional numerical model for debris flow-induced impulsive wave considering debris flow erosion-entrainment process

Landslides and debris flows occurring in reservoir watersheds can generate tsunami-like waves by inflowing into the reservoir. When such disasters occur during periods of high-water levels, such as the flood season, overtopping due to waves is inevitable. Analyzing such events is essential since they could lead to a dam break, which is particularly significant for Earth-fill dams, where overtopping alone greatly increases the risk of failure. Although several studies have attempted to address these phenomena through numerical modeling, there remains a lack of research that adequately considers the erosion and entrainment processes, which critically influence debris flow dynamics and the amplitude of debris flow-induced waves. In response, this study developed Deb2L, a two-dimensional two-layer numerical model based on shallow-water equations discretized using the finite volume method, capable of considering erosion, entrainment, and deposition processes. The performance of Deb2L was validated using theoretical and laboratory experiment results, demonstrating a quantitative accuracy with an R² value greater than 0.85 and an RMSE of less than 0.10 m. Its applicability to field-scale events was confirmed by simulating the 2020 Sanyang Reservoir event in Icheon, South Korea. Additionally, to verify the applicability of scenario analysis, the simulation results from the landslide analysis model TiVaSS were used as input data for Deb2L, confirming the potential for coupling these models. According to the results, simulations without erosion and entrainment processes led to an underestimation of the debris flow-induced wave complex disaster.