The Nature of Cohesive Sediment

Winterwerp, Johan C.; Kesteren, W.G.M. van

doi:10.1016/s0070-4571(04)80004-9

Cited by 144 publications

(69 citation statements)

References 5 publications

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“…Hydrodynamics are to a large degree controlling the sedimentation processes 50 and higher hydrodynamic forcing causes increased carbon (and likely nitrogen) erosion on the sediment surface 43 ; therefore, it was not surprising that the sediment carbon and nitrogen per sediment dry weight was negatively associated with wave exposure, as indicated previously 14 , 51 . Similarly, sediment with low density and high mud content, which was found in hydrodynamically sheltered meadows, has previously been linked to higher carbon storage in both temperate and tropical seagrass meadows 14 , 15 , 31 , 45 , 52 , as organic matter generally has lower weight than minerogenic material 50 , and contains more water 53 . However, a higher water content reduces the compaction and negatively affects the stability of the sediment 50 , 54 and consequently, a low sediment density is lowering the erosion threshold 55 , 56 .…”

Section: Discussionmentioning

confidence: 76%

The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

Dahl

Asplund

Björk

et al. 2020

Sci Rep

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Cold-temperate seagrass (Zostera marina) meadows provide several important ecosystem services, including trapping and storage of sedimentary organic carbon and nutrients. However, seagrass meadows are rapidly decreasing worldwide and there is a pressing need for protective management of the meadows and the organic matter sinks they create. Their carbon and nutrient storage potential must be properly evaluated, both at present situation and under future climate change impacts. In this study, we assessed the effect of wave exposure on sedimentary carbon and nitrogen accumulation using existing data from 53 Z. marina meadows at the Swedish west coast. We found that meadows with higher hydrodynamic exposure had larger absolute organic carbon and nitrogen stocks (at 0-25 cm depth). This can be explained by a hydrodynamically induced sediment compaction in more exposed sites, resulting in increased sediment density and higher accumulation (per unit volume) of sedimentary organic carbon and nitrogen. With higher sediment density, the erosion threshold is assumed to increase, and as climate change-induced storms are predicted to be more common, we suggest that wave exposed meadows can be more resilient toward storms and might therefore be even more important as carbon-and nutrient sinks in the future. Carbon sequestration and nutrient retention are highly important ecosystem services provided by seagrass ecosystems 1-4. The natural carbon and nutrient sinks these meadows provide are suggested to contribute to the mitigation of the acute threats to human wellbeing posed by climate change and increased anthropogenic pressure on the coastal zone 5,6. Therefore, there is an urgent need to increase protection of environments with high capacity for long-term carbon storage and nutrient filtering 7,8 , where environmental managers also need to consider future effects of climate change. Seagrass meadows have been highlighted as efficient carbon and nutrient sinks 9-12 , but this ecosystem function is not constant and varies significantly among regions and species 13-15. The ability of seagrass meadows to sequester and store organic matter is linked to their high primary production, the slow decomposition in marine sediment and their efficient trapping of allochthonous particles from surrounding habitats 16,17. The contribution of allochthonously derived organic matter to the accumulation of sedimentary organic matter can be substantial 17,18 , as seagrasses trap organic particles by reducing the flow of the water within the canopy 19-21 causing suspended organic matter to settle within the meadow and increasing the sedimentation rate 22. Hydrodynamics will thus largely determine sedimentation processes in seagrass-dominated environments 23 and it has been shown that low exposure to wind and wave action tends to favour a build-up of

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Section: Discussionmentioning

confidence: 76%

The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

Dahl

Asplund

Björk

et al. 2020

Sci Rep

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“…Talke et al 2009;Wang 2010;Papenmeier et al 2013). Hence, the erosion rate of the fluid mud layer is probably large, with a fairly low critical bed shear stress τ cr and large erosion parameter M. We use a classical approach to describe the dynamics of the fluid mud layer: erosion is computed with Partheniades' equation for erosion E, and deposition D as a shear stress independent flux (Sanford and Halka 1993;Winterwerp 2007):…”

Section: Model Formulationsmentioning

confidence: 99%

Fine sediment transport into the hyper-turbid lower Ems River: the role of channel deepening and sediment-induced drag reduction

2015

Self Cite

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Deepening of estuarine tidal channels often leads to tidal amplification and increasing fine sediment import. Increasing fine sediment import, in turn, may lower the hydraulic drag (due to a smoother muddy bed and/or sedimentinduced damping of turbulence), and therefore, further strengthen tidal amplification, setting in motion a process in which the sediment concentration progressively increases until the river becomes hyper-turbid (Winterwerp and Wang, Ocean Dyn 63(11-12):1279-1292, 2013). To advance our understanding of the relative role of bed roughness and bed topography on sediment import mechanisms and sediment concentration, a Delft3D numerical model has been setup for an estuary which has been deepened and as a consequence experienced a strong increase in suspended sediment concentration: the lower Ems River. This model is calibrated against present-day hydrodynamic and sedimentary observations, and reproduces the basic sediment transport dynamics despite simplified sedimentological formulations. Historic model scenarios are semi-quantitatively calibrated against historic high and low water observations, revealing that changes in hydraulic roughness and deepening are probably equally important for the observed tidal amplification. This model is subsequently used to better understand historic changes in the hydrodynamic and sediment transport processes in the lower Ems River. Import of fine sediment has increased because of larger tidal transport, even though the degree of tidal asymmetry may not have significantly changed. The resulting rise in suspended sediment concentration reduced hydraulic drag, amplifying the tidal range. Export of fine sediment became less because the river-induced residual flow velocity decreased with deepening of the channel.

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“…The deposition flux D (kg/m 2 /s) is computed without a critical shear stress for deposition, so deposition is modelled independently of the bed shear (Sanford and Halka 1993;Winterwerp 2007). All sediments initially deposit in the surface layer S 1 .…”

Section: Modelling Approach 21 Model Formulationsmentioning

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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The Nature of Cohesive Sediment

Cited by 144 publications

References 5 publications

The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

Fine sediment transport into the hyper-turbid lower Ems River: the role of channel deepening and sediment-induced drag reduction

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

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