Tidal asymmetry and estuarine morphology

Dronkers, J.

doi:10.1016/0077-7579(86)90036-0

Cited by 461 publications

(372 citation statements)

References 27 publications

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“…When the ebb and flood durations are unequal, this is known as tidal asymmetry and is caused by tidal wave distortion during propagation into shoaling water, along the coastal shelf and on entry into estuaries (Dronkers, 1986). The mechanism by which this occurs is the non-linear effect of tidal propagation.…”

Section: Tidal Asymmetrymentioning

confidence: 99%

“…Under ebb-dominant conditions, the opposite is true and net seaward transport will occur (Lanzoni and Seminara, 2002), causing sediment export from the estuary. The suspended load fraction of sediment transport is affected to a greater extent by tidal asymmetry than is the bedload fraction (Dronkers, 1986). Hence, the effect is likely to be greatest where small grain sizes dominate and suspension is the dominant transport method.…”

Section: Tidal Asymmetrymentioning

confidence: 99%

“…Conversely, 'top-down' models use basin scale morphological behaviour such as analysing geometrical relationships to predict changes. Examples of this include regime relationships like the tidal prism relationships of O'Brien (1939) and Eyesink (1991), form analysis (Prandle and Rahman, 1980) and tidal asymmetry analysis (Dronkers, 1986;Friedrichs and Aubrey, 1988). A mixture of these two approaches is seen in semi-empirical or 'hybrid' models which combine the complex 'bottom-up' method for simulating hydrodynamics, but use empirical formulae to simulate morphological changes (for example, van Dongeren and de Vriend, 1994).…”

Section: Introduction and Objectivesmentioning

confidence: 99%

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

Moore¹,

Wolf²,

Souza³

et al. 2009

Geomorphology

130

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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 shortterm, while these features are ephemeral in the long-term. In this study we investigate the spatial distribution of tidal distortion and asymmetry of 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 2 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. 1

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Section: Tidal Asymmetrymentioning

confidence: 99%

Section: Tidal Asymmetrymentioning

confidence: 99%

Section: Introduction and Objectivesmentioning

confidence: 99%

See 1 more Smart Citation

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

Moore¹,

Wolf²,

Souza³

et al. 2009

Geomorphology

130

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“…Residual sediment transport is sensitive to the tidal velocity pattern, thus system bathymetry is strongly influenced by ebb-flood asymmetries (Friedrichs and Perry 2001;Dronkers 1986). Tidal asymmetries can also arise from other interacting processes including variability of estuarine morphology (Fischer et al 1979;Dronkers 1986), phasing of principle tidal constituents with their higher harmonics (Aubrey and Speer 1985;DiLorenzo 1988), and channel friction and depth relationships (Aubrey and Speer 1985). The San Francisco Estuary is possibly unique because its overall ebb dominance arises from tidal harmonic content that sequences the low-low tide after the high-high tide about 80 % of the time (Malamud-Roam 2000).…”

Section: Introductionmentioning

confidence: 99%

Broad Timescale Forcing and Geomorphic Mediation of Tidal Marsh Flow and Temperature Dynamics

Enright

Culberson

Burau

2013

Estuaries and Coasts

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Tidal marsh functions are driven by interactions between tides, landscape morphology, and emergent vegetation. Less often considered are the diurnal pattern of tide extremes and seasonal variation of solar insolation in the mix of tidal marsh driver interactions. This work demonstrates how high-frequency hydroperiod and water temperature variability emerges from disparate timescale interactions between tidal marsh morphology, tidal harmonics, and meteorology in the San Francisco Estuary. We compare the tidal and residual flow and temperature response of neighboring tidal sloughs, one possessing natural tidal marsh morphology, and one that is modified for water control. We show that the natural tidal marsh is tuned to lunar phase and produces tidal and fortnight water temperature variability through interacting tide, meteorology, and geomorphic linkages. In contrast, temperature variability is dampened in the modified slough where overbank marsh plain connection is severed by levees. Despite geomorphic differences, a key finding is that both sloughs are heat sinks in summer by latent heat flux-driven residual upstream water advection and sensible and long-wave heat transfer. The precession of a 335-year tidal harmonic assures that these dynamics will shift in the future. Water temperature regulation appears to be a key function of natural tidal sloughs that depends critically on geomorphic mediation. We investigate approaches to untangling the relative influence of sun versus tide on residual water and temperature transport as a function of system morphology. The findings of this study likely have ecological consequences and suggest physical process metrics for tidal marsh restoration performance.

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“…As diferenças de densidade provocam o aumento das velocidades de correntes de maré enchente no fundo do canal e uma diminuição da mesma próximo à superfície e nas áreas rasas do estuário. O inverso ocorre com as correntes de maré vazante (Dronkers, 1986). À montante da transição água doce -água salgada, o fluxo fluvial está restrito aos canais e a velocidade e turbulência são relativamente altas.…”

Section: Introductionunclassified

Modelagem numérica da dinâmica do sistema estuarino Caravelas - Peruíbe, BA

Santos¹

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Tidal asymmetry and estuarine morphology

Cited by 461 publications

References 27 publications

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

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

Broad Timescale Forcing and Geomorphic Mediation of Tidal Marsh Flow and Temperature Dynamics

Modelagem numérica da dinâmica do sistema estuarino Caravelas - Peruíbe, BA

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