Document of bibliographic reference 206761

BibliographicReference record

Type

Bibliographic resource

Type of document

Journal article

BibLvlCode

AS

Title

Morphodynamic equilibrium in straight tidal channels: combined effects of Coriolis force and external overtides

Abstract

A new physical mechanism that is potentially relevant for the equilibrium morphodynamics of tide-dominated estuaries and in understanding the occurrence of lateral shoals in these systems is identified. The mechanism acts in relatively straight and wide channels (width of the order of the horizontal tidal excursion length) in which both external overtides and the Coriolis force affect sediment transport. This is investigated by analyzing an idealized model, which consists of the 3D shallow water equations, mass conservation for suspended load, and a bed evolution equation. The model is forced by a prescribed depth-averaged tidal current. It is demonstrated that, when viewed in the direction of the flood flow, a flood (ebb)-dominant current generates a net cross-sectional sediment transport to the left (right) in the Northern Hemisphere. A morphodynamic equilibrium is established by a counteracting dispersive sediment flux, generated by shear stresses that increase toward shallower water. This dispersive flux is much larger than the flux due gravitational downslope effects. The equilibrium bed profile has a constant slope in the lateral direction that varies as cos(j), where j is the phase difference between the M₂ and M₄ external horizontal tide. Hence, the smallest depths are found on the left (right) in case of a flood (ebb)-dominant current. Typical cross-channel depth differences may be as large as several meters. Velocity data collected in the Dutch Western Scheldt estuary are used to tune the hydrodynamic parameters in the model. Analysis of the bathymetric data seems to confirm the qualitative results of the model.

WebOfScience code

https://www.webofscience.com/wos/woscc/full-record/WOS:000181232500002

Bibliographic citation

Schramkowski, G.; de Swart, H.E. (2002). Morphodynamic equilibrium in straight tidal channels: combined effects of Coriolis force and external overtides. J. Geophys. Res. 107(C12): 17 pp. http://dx.doi.org/10.1029/2000JC000693

Is peer reviewed

true