Man-induced regime shifts in small estuaries—II: a comparison of rivers

Winterwerp, Johan C.; Wang, Zheng Bing; Braeckel, Alexander Van; Holland, G. van; Kösters, Frank

doi:10.1007/s10236-013-0663-8

Cited by 150 publications

(112 citation statements)

References 6 publications

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“…The latter is because tidal currents instigate net transport and mixing of, e.g., salt, sediment and nutrients, and thereby may cause zones of high turbidity (Allen et al 1980) where oxygen values will be low (Talke et al 2009b). Field data (see Jiang et al 2012, Schuttelaars et al 2013and Winterwerp et al 2013 indicate that tidal characteristics in many estuaries have changed during the last decades, probably in response to anthropogenic measures such as large-scale deepening of navigation channels and construction of jetties and groynes. Tides also change on longer time scales due to, e.g., sea level rise and changes in tidal forcing related to altered tidal motion in seas and oceans (Van der Spek 1997;Hall et al 2013;Mudersbach et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of tidal motion in well-mixed estuaries to cross-sectional shape, deepening, and sea level rise

2015

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For well-mixed estuaries, key physical mechanisms are identified and quantified that cause changes in characteristics of the semi-diurnal sea surface elevation and lateral velocity due to modifications of the lateral bottom profile, channel deepening, and sea level rise. This is done by decomposing solutions of a new analytical model into components relating to different physical processes. The default geometry and parameter values are representative for the Ems estuary, with a converging width and a reflective landward boundary. The default Gaussian lateral bottom profile is modified to obtain profiles with the same crosssectional area, but with a different skewness or steepness. Results show that a steeper lateral bottom profile leads to amplification of the sea surface elevation. The width convergence is shown to influence the resonance characteristics. Channel deepening and sea level rise result in amplification of the sea surface elevation until a resonance peak is reached. When flooding is incorporated, the amount of sea level rise at which maximum tidal amplification occurs is found to be about two times lower. When using a symmetric Gaussian bottom profile, the lateral tidal flow is determined by Coriolis deflection of longitudinal flow and lateral density gradients caused by differential salt advection. However, an additional lateral tidal flow component incorporating the effect of continuity related to sea level variations and longitudinal gradients in longitudinal flow is shown to become increasingly important for skewed lateral bottom profiles. Furthermore, the lateral flow due to the lateral density gradient is enhanced for bottom profiles with increased steepness.

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Section: Introductionmentioning

confidence: 99%

Sensitivity of tidal motion in well-mixed estuaries to cross-sectional shape, deepening, and sea level rise

2015

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“…net transport due to the correlation between tidal currents and tidally varying SSC), sediment transport by Stokes return flow and transport by residual flow that results from tidal straining. Other studies also point at the importance of wind (North et al 2004), stirring of sediment by wind waves at the intertidal areas (Green 2011) and flocculation processes (Winterwerp et al 2013). Note that in the present model, flocculation is only considered in a simple way, by using different values of settling velocity during spring tide and neap tide.…”

Section: Model Assumptions and Their Connection To Field Datamentioning

confidence: 99%

“…A similar conclusion was made by Chernetsky et al (2010) with respect to net sediment transport that results from the interaction between the M 2 tide and external M 4 tide. Recent studies (Donker and de Swart 2013;Winterwerp et al 2013) stressed the role of flocculation and hindered settling in sediment trapping.…”

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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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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“…In the lower Ems River (a tidal river that drains into the Ems Estuary), channel deepening has increased the SSC to the extent that the estuary has become hyperturbid (Winterwerp et al 2013;van Maren et al 2015b). The mechanisms responsible for the increase in SSC in the outer estuary are less straightforward.…”

Section: Management Scenarios: the Effect Of Equifinalitymentioning

confidence: 99%

Uncertainty in complex three-dimensional sediment transport models: equifinality in a model application of the Ems Estuary, the Netherlands

Maren

Cronin

2016

Ocean Dynamics

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Estuarine suspended sediment transport models are typically calibrated against suspended sediment concentration data. These data typically cover a limited range of the actual suspended sediment concentration dynamics, constrained in either time or space. As a result of these data limitations, the available data can be reproduced with complex 3D transport models through multiple sets of model calibration parameters. These various model parameter sets influence the relative importance of transport processes such as settling, deposition, erosion, or mixing. As a result, multiple model parameter sets may reproduce sediment dynamics in tidal channels (where most data is typically collected) with the same degree of accuracy but simulate notably different sediment concentration patterns elsewhere (e.g. on the tidal flats). Different combinations of model input parameters leading to the same result are known as equifinality. The effect of equifinality on predictive model capabilities is investigated with a complex threedimensional sediment transport model of a turbid estuary which is subject to several human interventions. The effect of two human interventions (offshore disposal of dredged sediment and restoration of the tidal channel profile) was numerically examined with several equifinal model settings. The computed effect of these two human interventions was relatively weakly influenced by the model settings, strengthening confidence in the numerical model predictions.

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Man-induced regime shifts in small estuaries—II: a comparison of rivers

Cited by 150 publications

References 6 publications

Sensitivity of tidal motion in well-mixed estuaries to cross-sectional shape, deepening, and sea level rise

Sensitivity of tidal motion in well-mixed estuaries to cross-sectional shape, deepening, and sea level rise

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

Uncertainty in complex three-dimensional sediment transport models: equifinality in a model application of the Ems Estuary, the Netherlands

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