Modelling Flow and Vegetation Effects in a Curved Channel

Channel bank erosion devastates land of agriculture, contributes largely to the sediment yield from watersheds, and deteriorates the downstream channel morphology and water quality. An important part of the bank erosion is due to bank failure known to be related to many factors including properties of bank materials, porous water, roots of vegetation in the bank, and the hydrological process in the channel. However, bank erosion is also affected by the hydrodynamics of the channel flow, the shear stress due to the flow would erode the bed (bank toe) and the bank surfaces resulting in not only sediment yield directly but also more potential mass failures. In this study, the numerical models developed at the NCCHE, CCHE3D/2D, were applied to simulate the flow in a natural channel, Goodwin Creek, Northern Mississippi, with a complex topography. Vegetation effects were modeled, since woody vegetations occupy a large portion of the channel strongly affecting the flow distribution. In addition, the main flow, helical secondary current and the associated shear stress distribution in the main channel are affected by the flow from a side channel. This study is intended to resolve the 3D flow field and its associated shear stress distribution in this curved channel. The information of flow pattern and shear stress from the numerical analysis will be applied to bank erosion and channel change studies. Flow data, channel topography, and in-stream vegetation condition were provided by the National Sedimentation.