ABSTRACT
The bank erosion in alluvial river often causes scour near floodplain area and channel meandering, then it may make the embankment collapse, fatalities and property damages. In this study, a three-dimensional mobile-bed model, called CCHE3D is adopted to simulate the morphological bed changes and local scour near embankment. The reach of Baibufan embankment in Taan River, Taiwan is selected as the study site. Due to the channel migration and mountain wall, the study reach had serious erosion problems and related structure failures in recent years. The influences of inflow discharge and sediment condition on riverbed changes and bank erosion are also discussed.
The local scour scheme of CCHE3D has been proposed and applied successfully in a case of bridge pier under non-uniform sediment conditions (Jia et al., 2017). It is assumed that the sediment entrainment and transport in the scour hole are related to the turbulence in the approach flow and the turbulence stimulated by the bridge pier. The turbulence fluctuations in the water are brought into the sediment layer via the strong vertical flow. The intruding turbulence fluctuation near sediment layer enhances the power of the flow to entrain sediment. This enhancement can be modeled using additional shear stress related to the intruding turbulence fluctuation.
Figure 1 and Figure 2 show the simulated velocity distribution and 3D vectors in the reach of Baibufan embankment. The mountain wall leads the flow shifting to the right bank and causes the erosion and local scour along the channel near Baibufan embankment. It shows that the model has the capability of simulating morphological changes and local scour in field case.
