Modeling flocculation in a hypertidal estuary

Ramírez-Mendoza, Rafael; Souza, Alejandro J.; Amoudry, Laurent O.

doi:10.1007/s10236-013-0675-4

Cited by 11 publications

(13 citation statements)

References 44 publications

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“…Turbulent mixing influences collisions, and therefore the potential for growth, but increases in G also lead to increased stress on the flocs and increases in breakup and erosion rates. Therefore, larger values of G lead to smaller equilibrium floc sizes in both the laboratory [e.g., Mietta et al ., ; Mikeš and Manning , ; Verney et al ., ] and field [e.g., Safak et al ., ; Ramírez‐Mendoza et al ., ], with d fe typically being

\propto η_{k}

[ Tambo and Hozumi , ; Akers et al ., ; van Leussen , ; Verney et al ., ; Kumar et al ., ]. G can also influence floc density.…”

Section: Introductionmentioning

confidence: 99%

“…The findings overviewed above on the role of G in setting floc properties have primarily been arrived at by either examining the same batch of flocs formed from suspensions of primary particles under constant turbulent mixing in the laboratory or through field observations of flocs under varying tidal or storm events [ Manning and Bass , ; Manning and Schoellhamer , ; Safak et al ., ; Ramírez‐Mendoza et al ., ]. Less work has been done to examine, in a Lagrangian framework, how the same suspension of mud responds to turbulent shear fields that change with time.…”

Section: Introductionmentioning

confidence: 99%

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Flocculation in a decaying shear field and its implications for mud removal in near‐field river mouth discharges

Strom

Keyvani²

2016

JGR Oceans

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We measure the change in floc size in a decaying shear field that mimics the decay found in a river mouth discharge. The primary questions explored are: (1) how far from equilibrium are the flocs during the decay? And, (2) how significant are the changes in size, and hence settling velocity, brought on by the changes in shear when it comes to predicting settling flux? These questions are examined in the laboratory using a camera system that allows for flocs to be sized within a turbulent suspension. We also examine how inclusion of various approaches to account for flocculation impacts the plume concentration and deposition rates in a simple river mouth discharge model. In the experiments, flocs grew from their initial size of 20–50 μm up to 100–200 μm due only to changes in shear over time scales of decay similar to those in a small river mouth discharge. It is estimated that such growth would lead to fourfold or greater fold increase in the mud settling velocity within the first few kilometers from the river mouth, even though floc sizes were only 0.5–0.8 of their equilibrium values. The plume modeling highlights the strong dependence of the mud deposition rate on the method chosen to account for flocs, and the importance of the settling to entrainment velocity ratio in dictating plume concentrations.

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\propto η_{k}

[ Tambo and Hozumi , ; Akers et al ., ; van Leussen , ; Verney et al ., ; Kumar et al ., ]. G can also influence floc density.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Flocculation in a decaying shear field and its implications for mud removal in near‐field river mouth discharges

Strom

Keyvani²

2016

JGR Oceans

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“…Classical links between turbulent properties and flocs in the Dee Estuary following which aggregation occurs during periods of weak turbulence (slack water at low and high tide) and break-up during periods of intense turbulence (maximum flood or ebb current) have been reported (e.g., Thurston, 2009;Ramírez-Mendoza et al, 2014) and included in numerical models . Amoudry et al (2014) highlighted the importance of horizontal gradients in suspended sediment, themselves due to gradients in turbulence and bed sediment distribution, toward reproducing observed SPM behaviour in the Hilbre Channel.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Effective energy controls on flocculation under various wave-current regimes

et al. 2016

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Transport of sediments is a critical process in the coastal zone because of its relation with coastal erosion, productivity and pollution. Of particular interest are the dynamics of suspended cohesive sediments, known as flocs, which can aggregate and break-up during the flocculation process. This changes their size, density, settling velocity and overall transport. Even though turbulence is widely accepted to be an important control on floc aggregation and break-up, specific and detailed floc behaviour is still not fully understood. The present study seeks to help in the understanding of the intra-tidal turbulence-induced flocculation under different current-wave regimes. Observations of floc size and currents at high sample rates are used to investigate the changes throughout a fortnightly cycle. The occurrence of waves at different stages during the sampling period enabled determination of three regimes of currents dominant, combined waves and currents,

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“…However, validation has shown it is still capable of simulating the frontal position, although the small scale variability is lost requiring the need for an additional high resolution nest in Liverpool Bay (Bricheno et al, 2014). Numerous studies validating the third 180 m nested model against observations (e.g., Bolaños et al, 2013;Brown et al, 2013;Amoudry et al, 2014;Bricheno et al, 2014;Ramirez-Mendoza et al, 2014;Brown et al, 2015) gives confidence in this 1.8 km to 180 m nested configuration.…”

Section: Model Setupmentioning

confidence: 99%

Impact of operational model nesting approaches and inherent errors for coastal simulations

et al. 2016

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A region of freshwater influence (ROFI) under hypertidal conditions is used to demonstrate inherent problems for nested operational modelling systems. Such problems can impact the accurate simulation of freshwater export within shelf seas, so must be considered in coastal ocean modelling studies. In Liverpool Bay (our UK study site), freshwater inflow from 3 large estuaries forms a coastal front that moves in response to tides and winds. The cyclic occurrence of stratification and remixing is important for the biogeochemical cycles, as nutrient and pollutant loaded freshwater is introduced into the coastal system. Validation methods, using coastal observations from fixed moorings and cruise transects, are used to assess the simulation of the ROFI, through improved spatial structure and temporal variability of the front, as guidance for best practise model setup. A structured modelling system using a 180 m grid nested within a 1.8 km grid demonstrates how compensation for error at the coarser resolution can have an adverse impact on the nested, high resolution application. Using 2008, a year of typical calm and stormy periods with variable river influence, the sensitivities of the ROFI dynamics to initial and boundary conditions are investigated. It is shown that accurate representation of the initial water column structure is important at the regional scale and that the boundary conditions are most important at the coastal scale. Although increased grid resolution captures the frontal structure, the accuracy in frontal position is determined by the offshore boundary conditions and therefore the accuracy of the coarser regional model.

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Modeling flocculation in a hypertidal estuary

Cited by 11 publications

References 44 publications

Flocculation in a decaying shear field and its implications for mud removal in near‐field river mouth discharges

Flocculation in a decaying shear field and its implications for mud removal in near‐field river mouth discharges

Effective energy controls on flocculation under various wave-current regimes

Impact of operational model nesting approaches and inherent errors for coastal simulations

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