Turbidity maxima in partially mixed estuaries: A two-dimensional numerical model

Festa, John F.; Hansen, Donald V.

doi:10.1016/0302-3524(78)90087-7

Cited by 186 publications

(78 citation statements)

References 7 publications

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“…It extends the model of Huijts et al (2006) in that conditions in the longitudinal direction are not uniform. The present model also extends an earlier model of Festa and Hansen (1978) in the sense that it includes both longitudinal and lateral dynamics. Besides, more sophisticated formulations for turbulent eddy viscosity and eddy diffusivity are used that depend on the degree of stratification and which allow for studying conditions during both spring and neap tides.…”

Section: Introductionsupporting

confidence: 53%

“…Many studies have focused on the mechanisms underlying the distribution of turbidity related to either longitudinal or lateral sediment transport. An important process that results in longitudinal sediment trapping is the joint action of seaward transport caused by river flow and the landward transport by the density-driven flow (Postma 1967;Festa and Hansen 1978;Schubel and Carter 1984;Geyer 1993;Talke et al 2009b). In that case, the maximum SSC occurs at the landward limit of the salt intrusion.…”

Section: Introductionmentioning

confidence: 99%

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Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model

Chen

Swart

2018

Ocean Dynamics

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This study investigates the longitudinal variation of lateral entrapment of suspended sediment, as is observed in some tidal estuaries. In particular, field data from the Yangtze Estuary are analysed, which reveal that in one cross-section, two maxima of suspended sediment concentration (SSC) occur close to the south and north sides, while in a cross-section 2 km downestuary, only one SSC maximum on the south side is present. This pattern is found during both spring tide and neap tide, which are characterised by different intensities of turbulence. To understand longitudinal variation in lateral trapping of sediment, results of a new three-dimensional exploratory model are analysed. The hydrodynamic part contains residual flow due to fresh water input, density gradients and Coriolis force and due to channel curvature-induced leakage. Moreover, the model includes a spatially varying eddy viscosity that accounts for variation of intensity of turbulence over the spring-neap cycle. By imposing morphodynamic equilibrium, the two-dimensional distribution of sediment in the domain is obtained analytically by a novel procedure. Results reveal that the occurrence of the SSC maxima near the south side of both crosssections is due to sediment entrapment by lateral density gradients, while the second SSC maximum near the north side of the first cross-section is by sediment transport due to curvature-induced leakage. Coriolis deflection of longitudinal flow also contributes the trapping of sediment near the north side. This mechanism is important in the upper estuary, where the flow due to lateral density gradients is weak.

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Section: Introductionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model

Chen

Swart

2018

Ocean Dynamics

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“…For example, using a tidally averaged numerical model, Festa and Hansen (1978) investigated the convergence zone of sediment due to the balance between gravitational circulation (Hansen and Rattray 1965;Officer 1976) and freshwater discharge. Recently, the Festa and Hansen approach was extended to include the influence of longitudinal suspended sediment concentration gradients on the tidally averaged flows and the trapping of sediment (Talke et al 2009b).…”

Section: Introductionmentioning

confidence: 99%

The effect of tidal asymmetry and temporal settling lag on sediment trapping in tidal estuaries

2010

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Over decades and centuries, the mean depth of estuaries changes due to sea-level rise, land subsidence, infilling, and dredging projects. These processes produce changes in relative roughness (friction) and mixing, resulting in fundamental changes in the characteristics of the horizontal (velocity) and vertical tides (sea surface elevation) and the dynamics of sediment trapping. To investigate such changes, a 2DV model is developed. The model equations consist of the widthaveraged shallow water equations and a sediment balance equation. Together with the condition of morphodynamic equilibrium, these equations are solved analytically by making a regular expansion of the various physical variables in a small parameter. Using these analytic solutions, we are able to gain insight into the fundamental physical processes resulting in sediment trapping in an estuary by studying various forcings separately. As a case study, we consider the Ems estuary. Between 1980 and 2005, successive deepening of the Ems estuary has significantly altered the tidal and sediment dynamics. The tidal range and the surface sediment concentration has increased and the position of the turbidity zone has shifted into the freshwater zone. The model is used to determine the causes of these historical changes. It is found that the increase of the tidal amplitude toward the end of the embayment is the combined effect of the deepening of the estuary and a 37% and 50% reduction in the vertical eddy viscosity and stress parameter, respectively. The physical mechanism resulting in the trapping of sediment, the number of trapping regions, and their sensitivity to grain size are explained by careful analysis of the various contributions of the residual sediment transport. It is found that sediment is trapped in the estuary by a delicate balance between the M 2 transport and the residual transport for fine sediment (w s = 0.2 mm s −1 ) and the residual, M 2 and M 4 transports for coarser sediment (w s = 2 mm s −1 ). The upstream movement of the estuarine turbidity maximum into the freshwater zone in 2005 is mainly the result of changes in tidal asymmetry. Moreover, the difference between the sediment distribution for different grain sizes in the same year can be attributed to changes in the temporal settling lag.

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“…For example, predictable blooms of diatoms are known to 'Also: Horn Point Environmental Laboratories. Center for Environmental and Estuarine Studies, University of Maryland, Box 775, Cambridge, Maryland 21613, USA accompany the spring freshet in several important estuaries in the United States, including San Francisco Bay (Peterson et al 1975, Festa & Hansen 1976, 1978, Conomos & Peterson 1977, Cloern & Cheng 1981, Cloern et al 1983), Delaware Bay (Sharp et al 1982, Pennock 1985, Pennock & Sharp 1986, and the Hudson River estuary (Malone 1977, Malone & Chervin 1979, Malone et al 1980.…”

Section: Introductionmentioning

confidence: 99%

Long-term trends in the distribution of phytoplankton in Chesapeake Bay: roles of light, nutrients and streamflow

Harding¹

1994

Mar. Ecol. Prog. Ser.

200

134

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This paper synthesizes >40 yr of data on phytoplankton abundance in the Chesapeake Bay, USA, spanning the period 1950 to 1990. Long-term changes in the concentrations of surface chlorophyll (B, mg m-3) and integrated water-column chlorophyll (B',,, mg m-2) are assessed in the context of light and nutrient effects on phytoplankton distributions. Significant long-term increases in B were detected from the 1950s to the 1970s in all regions of the Bay. The seaward, polyhaline Bay showed

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Turbidity maxima in partially mixed estuaries: A two-dimensional numerical model

Cited by 186 publications

References 7 publications

Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model

Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model

The effect of tidal asymmetry and temporal settling lag on sediment trapping in tidal estuaries

Long-term trends in the distribution of phytoplankton in Chesapeake Bay: roles of light, nutrients and streamflow

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