Flow structure and channel morphodynamics of meander bend chute cutoffs: A case study of the Wabash River, USA

Authors

  • Jessica A. Zinger,

    Corresponding author
    1. Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    • Corresponding author: J. A. Zinger, Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, 605 East Springfield Avenue, Champaign, IL 61820, USA. (zinger1@illinois.edu)

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  • Bruce L. Rhoads,

    1. Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    2. Department of Geology, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    3. Ven Te Chow Hydrosystems Laboratory, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
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  • James L. Best,

    1. Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    2. Department of Geology, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    3. Ven Te Chow Hydrosystems Laboratory, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
    4. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
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  • Kevin K. Johnson

    1. US Geological Survey, Illinois Water Science Center, Urbana, Illinois, USA
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Abstract

[1] This paper documents the three-dimensional structure of flow and bed morphology of two developing chute cutoffs on a single meander bend on the lower Wabash River, USA, and relates the flow structure to patterns of morphologic change in the evolving cutoff channels. The upstream end of the cutoff channels is characterized by: (1) a zone of flow velocity reduction/stagnation and bar development in the main channel across from the cutoff entrance, (2) flow separation and bar development along the inner (left) bank of the cutoff channel immediately downstream from the cutoff entrance, and (3) helical motion and outward advection of flow momentum entering the cutoff channel, leading to erosion of the outer (right) bank of the cutoff channel. At the downstream end of the cutoff channels, the major hydrodynamic and morphologic features are: (1) flow stagnation along the bank of the main channel immediately upstream of the cutoff channel mouth, (2) convergence of flows from the cutoff and main channels, (3) helical motion of flow from the cutoff, (4) a zone of reduced velocity along the bank of the main channel immediately downstream from the cutoff channel mouth, and (5) development of a prominent bar complex that penetrates into the main channel and extends from the stagnation zone upstream to downstream of the cutoff mouth. These results provide the basis for a conceptual model of chute-cutoff dynamics in which the upstream and downstream ends of a cutoff channel are treated as a bifurcation and confluence, respectively.

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