Revisiting the relationship between tidal asymmetry and basin morphology: a comparison between 1D and 2D models

Abstract

Tidal basin morphology is strongly dependent on the condition of tidal asymmetry which may result in either net import (flood-dominance) or export (ebb-dominance) of sediment. Based on the one-dimensional (1D) shallow water equations, various stability relationships have been developed linking tidal parameters with basin geometry. This study revisits the widely used numerical stability relationship developed by Friedrichs and Aubrey (1988), using a 2D depth-averaged model which is able to describe a more extensive flow field and more realistic bathymetries. Model comparison between 1D and 2D models indicates that excluding or including intertidal areas as a momentum-conveying component can highly affect the tidal velocity distribution and magnitude, particularly when the relative water depth is large (i.e., the ratio between tidal amplitude and mean water depth is small). Meanwhile, the tidal distortion parameters (relative tidal phase 2M2-M4 and tidal amplitude ratio M4/M2) derived from the 2D model appear to be more strongly controlled by the relative water depth (a/h) than that in the 1D model. Further research can be devoted to developing more generic stability relationships which can be applied in a more quantitative manner.

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ORCID for Ian Townend: orcid.org/0000-0003-2101-3858

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