Biophysical flocculation of suspended particulate matters in Belgian coastal zones

Shen, Xiaoteng; Toorman, Erik; Lee, Byung Joon; Fettweis, M.

doi:10.1016/j.jhydrol.2018.10.028

Cited by 22 publications

(26 citation statements)

References 89 publications

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“…If anything, such a change in biofeedbacks would impact the seasonal variability of floc sizes. Both in the North Sea and in the Westerschelde such seasonality linked to (micro-) biological activity has been documented, with typically higher floc sizes in summer and smaller sizes in winter 47–49 . A seasonality in flocculation dynamics provides a potential mechanism for the existence of alternative sediment distribution patterns after 2008/2009.…”

Section: Discussionmentioning

confidence: 99%

Critical transitions in suspended sediment dynamics in a temperate meso-tidal estuary

Cox

Maris

Engeland

et al. 2019

Sci Rep

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There is growing consensus that human interventions can fundamentally change fine sediment transport in estuaries. Critical transitions in response to human interventions have been hypothesized based on indirect observational evidence and theoretical understanding. So far direct evidence has been lacking. Based on a 20 year data-set of surface suspended particulate matter (SPM) concentrations, we present empirical evidence of critical transitions in a temperate meso-tidal estuary. In 2008–2009 the SPM dynamics of the Scheldt estuary (Belgium/The Netherlands) changed dramatically. Not only did the total amount of sediment in suspension increase, a new maximum turbidity zone (MTZ) at typical winter discharges appeared. At intermediate and low summer discharges the longitudinal distribution of SPM now flickers between two markedly different states. Our data suggest that a range of human interventions (fairway widening and deepening, dredging and dumping activities) set the scene leading to the observed transitions. Moreover the freshwater MTZ in the Scheldt and in its major tributary exhibit an increasing sensitivity towards freshwater discharge, coinciding with water quality improvements. This suggests large scale impacts of changes in eutrophication status on estuarine sediment dynamics. This has largely been a blind spot in morphodynamic research.

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Section: Discussionmentioning

confidence: 99%

Critical transitions in suspended sediment dynamics in a temperate meso-tidal estuary

Cox

Maris

Engeland

et al. 2019

Sci Rep

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“…Lee et al, 2012), and measured chlorophyll levels can be used to estimate the effect of suspended organic matter on flocculation (e.g. Shen et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Observations of Suspended Particle Size Distribution on an Energetic Ebb-Tidal Delta

Pearson

Prooijen

Wit

et al. 2019

Coastal Sediments 2019

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Sustainable management of barrier islands and tidal inlet systems requires a knowledge of sediment transport pathways throughout the system. This paper places in situ suspended sediment observations (obtained using a LISST) in context with seabed sediment samples and hydrodynamic measurements to identify such pathways. The results indicate two distinct populations of sediment in suspension on the ebb-tidal delta: locally resuspended fine sand and (largely flocculated) mud exported from the Wadden Sea on ebb tide. This reinforces the notion of the strong dependence of sediment pathways on particle size. Future work will combine additional lines of evidence to better distinguish suspended sand from sand-sized flocs and provide a more robust definition of these pathways.

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“…For instance, bimodal FSD with one peak at clay/silt size and the other at sand side indicates either the aggregation of silt and/or clay or intense erosion events of sand (Lee et al, ). Moreover, for realistic sediment modeling, knowledge of FSD is important for the selection of subordinate unimodal lognormal FSDs (e.g., Lee et al, ; Shen, Lee, et al, ; Shen, Toorman, et al, ), and the median floc size ( D 50 ), which is a crucial parameter.…”

Section: Introductionmentioning

confidence: 99%

Modeling Sediment Flocculation in Langmuir Turbulence

Liu

Liang

et al. 2019

JGR Oceans

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Cohesive sediments exist as flocs of different sizes, which are built and destroyed through flocculation processes including both aggregation and breakup. This study investigates sediment flocculation processes in wave-driven Langmuir turbulence that is commonly observed in coastal ocean through embedding a size-resolving flocculation model into a turbulence-resolving hydrodynamic model. The specific research questions are how Langmuir turbulence affects flocculation processes and how flocculation processes impact the spatial and size distributions of suspended cohesive sediment. The results show that Langmuir turbulence suspends flocs in the water column and organizes flocs of different sizes. By modulating the encounter of flocs and redistributing flocs in the turbulence field, Langmuir turbulence enhances the aggregation and breakup rates of flocs that are located in similar regions with high turbulent dissipation rates and suppresses those of others. As an outcome of modulated flocculation processes, floc size distribution changes with depth and floc mass concentration profiles change with floc size. The addition of wave breaking increases the shear rate near the surface and reduces the median floc size and averaged settling velocity, leading to increase in total floc mass concentration in the whole water column. Wave breaking also increases cross-shelf sediment transport by more than 15% under the simulated conditions, which is comparable to that due to Langmuir turbulence compared to shear turbulence. Both floc size distribution and floc concentration vary with wind and wave conditions. Key Points:• A size-resolving floc model embedded in a large eddy simulation model is used to study flocculation in shallow-water Langmuir turbulence • Flocculation processes modify vertical mean concentration profiles for flocs of a certain size • Langmuir turbulence modulates aggregation and breakup rates Supporting Information:• Supporting Information S1

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Biophysical flocculation of suspended particulate matters in Belgian coastal zones

Cited by 22 publications

References 89 publications

Critical transitions in suspended sediment dynamics in a temperate meso-tidal estuary

Critical transitions in suspended sediment dynamics in a temperate meso-tidal estuary

Observations of Suspended Particle Size Distribution on an Energetic Ebb-Tidal Delta

Modeling Sediment Flocculation in Langmuir Turbulence

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