Development and Application of Two-Dimensional Numerical Model for Channel Erosion and Migration

In Taiwan, alluvial rivers are short and with great longitudinal gradient, so when intense rainfall events occur, the short flooding duration could cause serious vertical and lateral erosion on riverbed, leading to migration of the main deep channel. These results could endanger the safety of river structure and riverbank stability. In this study, we aim to develop a two-dimensional depth-averaged hydrodynamic and sediment transport model that includes the riverbank stability module to simulate riverbed vertical and lateral erosion, riverbank failure and channel migration. In this model, the water level, riverbed erosion, the groundwater level and pore water pressure inside the riverbank are firstly calculated. By using the hydrostatic assumption, the flow-induced pressure acting on riverbank can be estimated. Then, the riverbank stability model is developed by considering all the forces acting on the failure force of the riverbank to determine if the riverbank would collapse under certain hydrological conditions. The interactions of the river water level and the groundwater level are also examined to investigate their influences on the riverbank stability. The test results collected in the laboratory experiments are used to calibrate and verify the proposed riverbank lateral erosion and migration model. Finally, an example of riverbank failure occurred in Lao-Nong Creek, Taiwan in 2012 is used to show the feasibility and capability of the developed model.