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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #242470
Title: Merging of RVR meander with CONCEPTS: Simplified 2D model for long-term meander evolution

Author
item MOTTA, DAVIDE - University Of Illinois
item ABAD, JORGE - University Of Illinois
item Langendoen, Eddy
item GARCIA, MARCELO - University Of Illinois

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/30/2009
Publication Date: 9/1/2009
Citation: Motta, D., Abad, J.D., Langendoen, E.J., Garcia, M.H. 2009. Merging of RVR meander with CONCEPTS: Simplified 2D model for long-term meander evolution. In: River, Coastal and Estuarine Morphodynamics: RCEM 2009. pp 37-42.

Interpretive Summary: Application of one-dimensional channel evolution computer models, such as the ARS computer model CONCEPTS, is problematic in meandering streams because of the strong three-dimensional nature of the stream flow. The topography and flow dynamics in meander bends increase the forces exerted by the flowing water on the stream bank at the outside of a meander bend compared to those exerted on stream banks in straight channels. Current two-dimensional computer models developed specifically to simulate the migration of meandering streams, however, employ simplified empirical relationships to determine channel migration and therefore stream bank erosion. To model the mechanics of meander migration correctly the stream bank erosion component of the CONCEPTS model was combined with the meander model RVR MEANDER developed by the University of Illinois. Application of the new model to a highly meandering reach of Trout Creek in the Tahoe Basin, California, shows that flow and the adjustment of channel geometry are adequately simulated. The presented methodology improves the accuracy and reduces the uncertainty in model outcome for streams with a meandering planform. One-dimensional channel evolution models are widely used by federal and state agencies, such as the US Geological Survey, the US Bureau of Reclamation, the US Corps of Engineers, the Natural Resources Conservation Service and the US Environmental Protection Agency, to design stream-channel conservation measures and assess their long-term stability and benefits.

Technical Abstract: RVR Meander is a simplified two-dimensional (2D) hydrodynamic and migration model (Abad and Garcia, 2006) while CONCEPTS (CONservational Channel Evolution and Pollutant Transport System) is a one-dimensional (1D) hydrodynamic and morphodynamic model (Langendoen and Alonso, 2008; Langendoen and Simon, 2008; Langendoen et al., 2009). Originally, RVR Meander reported only the use of Ikeda et al. (1981)’s hydrodynamic model, where the bank migration (M) was modeled by using the concept of near bank excess velocity (u_e). In this regard, the bank migration was expressed as M = C * u_e, where C is a bank migration coefficient, calibrated upon historical centerlines. The bed morphology was not modeled according to the sediment mass conservation (Exner equation), but instead it was assumed that the transversal bed slope was directly related to local curvature. On the other hand, CONCEPTS uses an advanced treatment of the bank retreat. However, since CONCEPTS is a 1D model, it does not incorporate corrections for secondary flow and transversal bed slope: therefore its applicability to meander bends might underestimate the shear stress along the stream banks and consequently underpredict the migration rate. This paper shows the preliminary results of an ongoing effort to merge both models, with the goal of implementing a hydrodynamic and morphodynamic model capable of reproducing the flow field and the river migration for predicting long-term evolution needed in engineering and geological applications.