A Simplified CVFEM-Based Model for Debris Flow Fan Morphology at Tributary Confluences

This study presents a simplified approach using the control volume finite element method (CVFEM) to model debris flow fan morphology at tributary confluences, with a specific focus on the effects of main channel flow rates and slopes. Conventional models often require extensive parameterization and computational resources to simulate such complex sediment transport processes. In contrast, our simplified model introduces an effective slope parameter to represent the influence of the main stream on the evolving fan morphology. This adjustment allows for a more efficient yet reliable simulation framework, particularly in scenarios where real-time analysis or rapid assessments are needed. To validate the model, we conducted field-based comparisons using morphological data from the confluence of the Yu-Shui River and Laonong River, a region prone to frequent debris flow events and significant sediment deposition. The model successfully reproduced essential features observed in the field, including fan elongation and narrowing in response to increased main stream flow rates. Despite its simplified structure, the model showed consistent agreement with field observations across varying hydraulic and topographic conditions, highlighting its capability to capture key morphological trends without the need for excessive computational effort. By incorporating the effective slope parameter to simulate main stream influence, this approach offers a practical and computationally efficient tool for simulating debris flow fan dynamics. The simplified model holds promise for applications in geomorphological research, sediment transport analysis, and disaster risk management, particularly in data-scarce or rapidly evolving environments.