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Morphological evolution of the Dee Estuary, Eastern Irish Sea, UK: a tidal asymmetry approach

Moore, Rowena D.; Wolf, Judith; Souza, Alejandro J.; Flint, Stephen S.. 2009 Morphological evolution of the Dee Estuary, Eastern Irish Sea, UK: a tidal asymmetry approach. Geomorphology, 103 (4). 588-596. 10.1016/j.geomorph.2008.08.003

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Abstract/Summary

Asymmetry in the tide (unequal ebb and flood duration) is a dominant factor in causing residual sediment transport and morphological changes in estuaries. The evolution of estuarine morphology is a process of dynamic equilibrium in the short-term, while these features are ephemeral in the long-term. In this study we investigate the spatial distribution of tidal distortion and asymmetry in the Dee estuary, UK, by 3-dimensional numerical modelling methods. High resolution LIDAR surveys are used to underpin and explain our numerical modelling results in terms of basin hypsometry and areas of recent erosion and deposition. Harmonic analysis of the numerical modelling results showed that the shallower intertidal areas (sand and mud banks) were the most tidally asymmetric, showing flood dominance. The main navigation channels showed some ebb dominance but the tides here were relatively undistorted. This overall flood dominance is likely to induce net sediment import to the Dee, which explains known historical morphological changes (large scale accretion over the last two centuries) and also recent morphological changes as seen from the LIDAR surveys (which show predominantly net accretion between 2003 and 2006). Hypsometrical analysis suggests the Dee may be approaching equilibrium, and that the flood dominance and sedimentation rate may therefore decrease in the future. In an infilling estuary, an increase in the area and elevation of tidal flats can eventually shift an estuary towards ebb dominance, as shown by previous research and by ‘idealised estuary’ modelling results presented in this study. The large tidal amplitude to hydraulic depth ratio of the Dee, however, suggests that the tidal flats would have to be very extensive indeed for this to occur

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.geomorph.2008.08.003
Programmes: NOC Programmes > Marine Systems Modelling
Oceans 2025 > Shelf and coastal processes
ISSN: 0169-555X
Additional Information. Not used in RCUK Gateway to Research.: Available online August 22, 2008, print version Feb. 2009, 103 (4) Moore, Rowena D.; Flint, Stephen S., Univ Liverpool, Dept Earth & Ocean Sci, Liverpool L69 3GP, Merseyside, England Moore, Rowena D.; Wolf, Judith; Souza, Alejandro J., Proudman Oceanog Lab, Liverpool L3 5DA, Merseyside, England
Additional Keywords: MORPHOLOGY; DEE ESTUARY; TIDAL ASYMMETRY; SEDIMENT TRANSPORT; HYDRODYNAMICS; HYPSOMETRY; EMPIRICAL STABILITY; RELATIONSHIPS; SALT MARSH; MODEL; INLET; SYSTEMS; PROPAGATION
NORA Subject Terms: Marine Sciences
Date made live: 18 Mar 2009 17:38
URI: http://nora.nerc.ac.uk/id/eprint/6505

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