Velocity surges and asymmetry in tidal channels

Pethick, John

doi:10.1016/s0302-3524(80)80087-9

Cited by 119 publications

(88 citation statements)

References 6 publications

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“…Similarly, the ebb surge takes place after the drainage of the marsh for a water elevation just below the marsh surface, and it is therefore confined in the channels (Figure 3). The stage-discharge and stage-velocity curves therefore present an asymmetry as observed in the field by many researchers (Pethick 1980;Healey et al 1981).…”

Section: Fluxes Of Watermentioning

confidence: 71%

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

et al. 2013

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Tidal oscillations systematically flood salt marshes, transporting water, sediments, organic matter, and biogeochemical elements such as silica. Here we present a review of recent studies on these fluxes and their effects on both ecosystem functioning and morphological evolution of salt marshes. We reexamine a simplified model for the computation of water fluxes in salt marshes that captures the asymmetry in discharge between flood and ebb. We discuss the role of storm conditions on sediment fluxes both in tidal channels and on the marsh platform. We present recent methods and field instruments for the measurement of fluxes of organic matter. These methods will provide long-term data sets with fine temporal resolution that will help scientists to close the carbon budget in salt marshes. Finally, the main processes controlling fluxes of biogenic and dissolved silica in salt marshes are explained, with particular emphasis on the uptake by marsh macrophytes and diatoms.

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Section: Fluxes Of Watermentioning

confidence: 71%

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

et al. 2013

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“…These simplifications make the model most valid for relatively short embayments, such that the water surface at any give time can be assumed to depart only slightly from a flat configuration. This assumption has been done in continuity models developed in the past [Boon, 1975;Pethick, 1980] The flow field in a tidal lagoon is described by the twodimensional, depth-averaged equations of momentum and continuity which, assuming the Boussinesq approximation in the horizontal and the hydrostatic approximation in the vertical to be satisfied [Dronkers, 1964] in the continuity equation, we set F = 1, which allows us to estimate the length scale L o. On the basis of data reported in Table A1, We note that (A9) is appropriate for analysis of the integral properties of a tidal basin (such as delineation of drainage divides) but not for the determination of the exact velocity distribution [Zimmerman, 1982].…”

Section: Appendixmentioning

confidence: 99%

Tidal networks: 2. Watershed delineation and comparative network morphology

Rinaldo¹,

Fagherazzi²,

Lanzoni³

et al. 1999

Water Resources Research

194

285

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Abstract. Through the new method for automatic extraction of a tidal network from topographic or bathymetric fields described in a companion paper [Fagherazzi et al., this issue], we analyze the morphology of aggregated patterns that we observe in nature in different tidal environments. Specifically, we define, on the basis of a hydrodynamic analysis, a procedure for watershed delineation and for the identification of the "divides" for every subnetwork and look at the resulting drainage density and its related scaling properties. From the systematic, large-scale plots of drainage density and channel width versus watershed area we address the issue of a possible geomorphic criterion that corresponds to the parts of the tidal landscape that are characterized by river-like features. We also analyze the relationship of total contributing tidal basin area to channel widths and to mainstream lengths (Hack's law). We study comparatively probability distributions of total drainage areas and of "botanical" mass (the area of the channelized landscape upstream of a given section) for tidal and fluvial patterns and find altered scaling features of tidal landforms that reflect the complex interactions of different mechanisms that shape their geometry. Simple geomorphic relationships of the types observed in the fluvial basin (e.g., power laws in the watershed area versus drainage density, mainstream length, or channel width relationships) do not hold throughout the range of scales investigated and are site-specific. We conclude that tidal networks unlike rivers exhibit great diversity in their geometrical and topological forms. This diversity is suggested to stem from the pronounced spatial gradients of landscape-forming flow rates and from the imprinting of several crossovers from competing dynamic processes. IntroductionIn this paper, the second in a series of three, we quantify various tidal network properties including common power law relationships which have been well documented for terrestrial river systems [Rodriguez-Iturbe and Rinaldo, 1997]. Our goals here are both to explore tidal channel scaling properties and to infer, based on scaling breaks, possible changes in dominant formative process through a network. We anticipate that spatial variation in the dominance of ebb versus flood tides and in erosional resistance associated with vegetation and sediment texture could give rise to limited scaling compared to that found in terrestrial systems (where single power law relationships typically apply across many orders of magnitude). Hence we propose to apply common power law relationships quantified for terrestrial systems to tidal systems and use these analyses to identify possible geomorphic "signatures" of dominant processes. In order to perform morphometric analysis of tidal networks, we need an objective procedure for delineating the drainage area to any link. Here we first introduce a new method, based on flow hydrodynamics, for delineating drainage directions and contributing areas throughout the tidal network...

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“…La agradación sedimentaria en marismas se debe al comportamiento asimétrico del ciclo de marea (Pethick, 1980): durante el semiciclo de llenante el flujo mareal transporta sedimento en suspensión, básicamente arcillas y limos, que se acumulan durante la pleamar una vez que el flujo se detiene, a menudo gracias a procesos de floculación biogénica de partículas arcillosas. Durante y tras su sedimentación, las partículas arcillosas desarrollan enlaces electrostáticos que rápidamente les confieren una creciente cohesión interna.…”

Section: Morfodinámica De Las Marismas Y Salinas De La Bahía De Cádizunclassified

Evolución histórica y geomorfología de las explotaciones salineras en marismas mareales. Ejemplos de la bahía de Cádiz

Prieto

Villalobos

Abarca

2017

CyG

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Las marismas son espacios explotados por el ser humano a lo largo de siglos debido a la importancia de sus recursos y a la posibilidad de obtenerlos con cierta facilidad. Diferentes AbstractThis work displays a synthesis about the current knowledge about the origin and historical development of the salines on the Bay of Cádiz. Geoarchaeological data suggest that the first salines were probably built in the area during the Phoenician period, although their development seems to have been greater in the Roman epoch, favored by a sedimentation rate increase in the marshes of the zone. Nowadays very few records exist of the ancient salt works and salt harvesting, due to the continuous reutilisation of these structures over centuries. The present location of salines in the Bay of Cádiz is in part controlled by the distribution of the sedimentation rates registered in the salt marshes, which are conditioned by the geometry of the tidal channels. After the last phase of saline expansion during the 19 th century, the Bay of Cádiz salinas have suffered a progressive abandonment and degradation, due both to human actions (infilling for agricultural, transportation, industrial and urban uses) and to natural processes (aeolian sand sedimentation, erosion due to the acceleration of tidal fluxes, etc.). Nevertheless, despite their deterioration, today their preservation as anthropogenic landscapes of heritage interest for public could be insured due to their membership of the Bay of Cádiz Natural Park, and to be placed within the public maritime-terrestrial domain (Spanish Shore Act).

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Velocity surges and asymmetry in tidal channels

Cited by 119 publications

References 6 publications

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

Tidal networks: 2. Watershed delineation and comparative network morphology

Evolución histórica y geomorfología de las explotaciones salineras en marismas mareales. Ejemplos de la bahía de Cádiz

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