Location: Watershed Physical Processes ResearchTitle: Numerical modeling of dune progression in a high amplitude meandering channel
|MENDOZA, ALEJANDRO - University Of Pittsburgh|
|WANG, DOGCHEN - Electricite De France (EDF)|
|ABAD, JORGE - University Of Pittsburgh|
|TASSI, PABLO - Electricite De France (EDF)|
|EL KADI ABDERREZZAK, KAMAL - Electricite De France (EDF)|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2014
Publication Date: 8/27/2014
Citation: Mendoza, A., Wang, D., Abad, J.D., Langendoen, E.J., Tassi, P., El Kadi Abderrezzak, K. 2014. Numerical modeling of dune progression in a high amplitude meandering channel. n Proceedings of River Flow 2014, September 3-5, 2014, Lausanne, Switzerland. A. J. Schleiss, G. De Cesare, M. J. Franca, & M. Pfister (eds.) pp. 1097-1104.
Interpretive Summary: Calculations of bank erosion rate in meandering streams generally use boundary shear stress estimates that are only affected by river geometry at the reach scale, such as channel curvature and the point bar located on the inside of a meander bend. However, laboratory experiments have shown that bank shear stress may be increased locally by migrating bed forms. As a result, current formulations of bank retreat rate may be underestimating the rate at which rivers migrate. Scientists of the USDA-ARS National Sedimentation Laboratory in collaboration with researchers of the University of Pittsburgh and the French National Hydraulics Laboratory-Chatou, have developed a detailed computer simulation of the three-dimensional flow, sediment transport, and bed morphology in meandering rivers. The computer simulation was validated against laboratory experiments conducted at the University of Illinois. It was found that the sediment transport conditions imposed at the upstream boundary of the computer simulation significantly impacted the geometry and migration rate of migrating bed forms. Recirculating the sediment from the downstream boundary to the upstream boundary better predicted the observed bed forms than imposing a constant sediment feed rate. The latter boundary condition is typically used to model sediment transport in rivers. The findings can be used by scientists and engineers involved in evaluating sediment management in rivers using computer models to reduce uncertainty in model results.
Technical Abstract: Laboratory experiments carried out by Abad and Garcia (2009) in a high-amplitude Kinoshita meandering channel show bed morphodynamics to comprise steady (local scour and deposition) and unsteady (migrating bedforms) components. The experiments are replicated with a numerical model. The sediment transport formulation was calibrated using the sediment transport rates measured in the experiments. The unsteady bed condition is achieved by using a periodic sediment boundary condition, and the steady bed condition is achieved by using an averaged sediment transport rate. For both cases dune-like bedforms develop, however the periodic boundary condition produces more active dunes. Also, the periodic boundary condition produces zones of higher shear stress, which is similar to results obtained by Abad et al. (2013).