Author(s): P. Zinke; N. R. B. Olsen; J. Bogen
Linked Author(s): Nils Reidar B. Olsen, Peggy Zinke
Keywords: Delta; CFD modeling; Vegetation resistance; Flood; Levee
Abstract: A three-dimensional numerical model was used to compute the water flow and the sediment deposition for two different flow situations during a large flood in the delta of Lake Oyeren in Norway. The model solved the Navier-Stokes equations with the k-H turbulence model on a 3D unstructured grid with dominantly hexahedral cells. The sediment transport was computed solving the convection-diffusion equation for sediment concentration, using an empirical formula for the bed pick-up rate. Bed elevation changes were calculated from sediment continuity in the bed cell. The results were tested against documented water level gradients and sedimentation heights obtained from field measurements. Based on the computations, it appears that the depositions on the lower and the higher parts of the islands happened during different stages of the flood. Therefore the modeling of the real deposition heights requires a computation for the complete discharge and sediment time-variation curve during the flood. Together with the correct definition of the boundary conditions for the flow and sediments, the proper parametrization of the delta vegetation's flow resistance seems to play a key role for the modeling, since height and density of vegetation strongly affected the position and intensity of the sediment depositions.
Year: 2009