Modeling river morphodynamic process using a depth-averaged computational model and an application to a mountain river

Authors: YAFEI, JIA - Mississippi State University; YAOXIN, ZHANG - Mississippi State University; KEH-CHIA, YEH - National Chaio Tung University; CHUNF-TA, LIAO - National Chaio Tung University

Submitted to: Intech
Publication Type: Book / Chapter
Publication Acceptance Date: 7/1/2019
Publication Date: 1/8/2020
Citation: Yafei, J., Yaoxin, Z., Keh-Chia, Y., Chunf-Ta, L. 2020. Modeling river morphodynamic process using a depth-averaged computational model and an application to a mountain river. Intech. http://dx.doi.org/10.5772/intechopen.86692.
DOI: https://doi.org/10.5772/intechopen.86692

Interpretive Summary: Natural rivers often change their courses due to internal dynamic processes of flow and sediment transport. Bank erosion is a primary mechanism influencing course changes. These processes can be simulated using well developed numerical models which include effective and efficient methodologies. In this paper, the two dimensional model, CCHE2D, is described, validated using physical experimental data and applied to simulate severe bank erosion problems for the Chuoshui River, a natural river in Taiwan. This is one of the large rivers in the world with an active bank erosion problem. The model was shown to be capable of simulating unsteady flows with nonuniform sediment transport and cohesive/non-cohesive material bank erosion. Utilization of bed load and suspended sediment formulations within the model provide capabilities to determine the effects of secondary currents on sediment transport induced by flow curvatures. The model simulation enabled local water resource engineers to better understand bank erosion and mitigate the problems.

Technical Abstract: Bank erosion is a dominant river morphodynamic process resulting in encroaching valuable farming land and channel migration. Prediction of bank erosion and channel migration requires understanding of the morphodynamics of the entire river system. Numerical modeling is an ideal method for this task. However, models with full capabilities and applications on complex real-world problems are rare. In this study the finite element-based computational model, CCHE2D, and its flow, sediment transport, and bank erosion modules are introduced. The model is capable of simulating unsteady flows with nonuniform sediment transport and cohesive/non-cohesive material bank erosion. The effects of helical secondary current on sediment transport induced by flow curvatures are reflected in both bed load and suspended sediment formulations. This model is validated using multiple sets of experimental data and applied to bank erosion problems of the Chuoshui River, a real-world mountain river in Taiwan. Characterized by typhoon floods, steep channel slopes, and high sediment load and mobility, this river often exhibits a braided pattern consisting of multiple curved channels. Channel bed change and bank erosion caused by 10 years of typhoon floods in a selected reach have been simulated, and the computed bank erosion results agreed with the field observation.