nspired by the two-layer model of a stratified lake forced by wind stress, we introduce the concept of Wedderburn number (W) to quantify, for the first time, how turbidity and contour currents interacted to determine sedimentation in unidirectionally migrating deep-water channels (UCs). Bankfull turbidity flows in the studied UCs were computed to be supercritical (Froude number of 1.11-1.38) and had velocities of 1.72-2.59 m/s. Contour currents with assumed constant velocities of between 0.10 m/s and 0.30 m/s flowing through their upper parts would result in pycnoclines between turbidity and contour currents, with amplitudes of up to 7.07 m. Such pycnoclines, in most cases, would produce Kelvin-Helmholtz billows and bores that had velocities of 0.87-1.48 m/s and prograded toward the steep channel flanks by 4.0° to 19.2°. Pycnoclines' wavefronts with the strongest shocks and deepest oscillations would, therefore, occur preferentially along the steep flanks, thereby promoting erosion; on the other hand, their wavetails with the weakest shocks and shallowest oscillations would occur preferentially along the gentle flanks, thereby promoting deposition. Such asymmetric intra-channel deposition, in turn, forced individual channels to consistently migrate toward the steep flanks, forming channels with unidirectional channel trajectories and asymmetrical channel cross sections.

How do turbidity flows interact with contour currents in unidirectionally migrating deep-water channels?

Rebesco M;Salon S;
2018

Abstract

nspired by the two-layer model of a stratified lake forced by wind stress, we introduce the concept of Wedderburn number (W) to quantify, for the first time, how turbidity and contour currents interacted to determine sedimentation in unidirectionally migrating deep-water channels (UCs). Bankfull turbidity flows in the studied UCs were computed to be supercritical (Froude number of 1.11-1.38) and had velocities of 1.72-2.59 m/s. Contour currents with assumed constant velocities of between 0.10 m/s and 0.30 m/s flowing through their upper parts would result in pycnoclines between turbidity and contour currents, with amplitudes of up to 7.07 m. Such pycnoclines, in most cases, would produce Kelvin-Helmholtz billows and bores that had velocities of 0.87-1.48 m/s and prograded toward the steep channel flanks by 4.0° to 19.2°. Pycnoclines' wavefronts with the strongest shocks and deepest oscillations would, therefore, occur preferentially along the steep flanks, thereby promoting erosion; on the other hand, their wavetails with the weakest shocks and shallowest oscillations would occur preferentially along the gentle flanks, thereby promoting deposition. Such asymmetric intra-channel deposition, in turn, forced individual channels to consistently migrate toward the steep flanks, forming channels with unidirectional channel trajectories and asymmetrical channel cross sections.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.14083/619
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