loading page

Hydrodynamic processes of incipient meander chute cutoffs- implications for morphodynamics and depth-averaged modeling
  • +5
  • Jason Tzu-Yao Lin,
  • Esteban Lacunza,
  • Roberto Fernández,
  • Marcelo H García,
  • Bruce L. Rhoads,
  • James L. Best,
  • Jessica Zinger LeRoy,
  • Gary Parker
Jason Tzu-Yao Lin
University of Illinois at Urbana-Champaign

Corresponding Author:[email protected]

Author Profile
Esteban Lacunza
Universidad Nacional de la Plata
Author Profile
Roberto Fernández
Department of Civil and Environmental Engineering, The Pennsylvania State University
Author Profile
Marcelo H García
University of Illinois at Urbana Champaign
Author Profile
Bruce L. Rhoads
University of Illinois at Urbana Champaign
Author Profile
James L. Best
UIUC
Author Profile
Jessica Zinger LeRoy
United States Geological Survey
Author Profile
Gary Parker
University of Illinois at Urbana Champaign
Author Profile

Abstract

Meander chute cutoffs are a common and geomorphically important feature of meandering rivers. They exhibit complex dynamics and distinctive morphologic features. To date, however, the geomorphic processes governing the evolution and formation of these features are poorly understood due to limited knowledge of cutoff hydrodynamics. This paper investigates three-dimensional mean flow structure, turbulent flow structure, and bed shear stress distribution from high-resolution flow velocity data in a sediment-free physical model. The results show that 1) the chute channel conveys around 1.4 times the unit-width flow discharge as the cutoff bend; 2) mean flow structure is highly three-dimensional, with strong convective acceleration throughout the bends and pronounced flow separation zones in both the chute channel and the cutoff bend; 3) turbulent kinetic energy is intense at shear layers bounding the flow separation zones at several locations in the channel; and 4) bed shear stress is elevated due to strong turbulence in the chute channel and is low in the cutoff bend. The unique hydrodynamics of meander chute cutoffs explain their distinctive morphologic behaviors, including the rapid widening and deepening of chute channels and locations of bars and pools. Moreover, this paper quantitatively compares the secondary flow structure before and after the cutoff, showing that cross-sectional redistribution of streamwise momentum by secondary flow decreases due to more vertically uniform flow in the presence of the chute cutoff, suggesting lesser correction on the 2D depth-averaged hydrodynamics compared with the pre-cutoff single-channeled meander in numerical modeling.
05 Aug 2024Submitted to ESS Open Archive
05 Aug 2024Published in ESS Open Archive