Analysis on residual coarse sediment transport in estuaries

Chu, Ao; Wang, Zheng Bing; Vriend, H.J. de

doi:10.1016/j.ecss.2015.06.003

Cited by 21 publications

(11 citation statements)

References 27 publications

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“…Because of the higher water depth, the tidal wave crest travels faster than the trough, increasing the current during flood (Friedrichs, ; Hunt et al, ). A detailed analysis of tidal harmonics in the YRE delta indicates that the contribution of the M4 constituent to tidal asymmetry is the largest and that interactions of the residual current M0 with all tidal constituents also affect the residual sediment transport (Chu et al, ). Here, for sake of simplicity, we only focus on the M2 and M4 constituents, exploring whether their contribution to tidal asymmetry changed between 1997 and 2010.…”

Section: Resultsmentioning

confidence: 99%

“…Tidal asymmetry can impact the sediment transport and morphological evolution of tidally dominated estuaries van der Wegen, 2013). The large fluvial flow controls residual currents in the SP, NP, and NC resulting in an ebb-dominated system (Figure 12; see also Chu et al, 2015). However, tidal distortion can amplify or decrease ebb dominance and the transport of sediments to the ocean.…”

Section: Tidal Asymmetrymentioning

confidence: 99%

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A Positive Feedback Between Sediment Deposition and Tidal Prism May Affect the Morphodynamic Evolution of Tidal Deltas

et al. 2018

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Tidal deltas are fragile systems whose morphology can be easily impacted by variations in water and sediment fluxes caused by natural and human processes. Here we explore the relation between tidal prism and sediment dynamics in tidal deltas using the recent evolution of the Yangtze River estuary, China, as an example. Using the numerical model Delft3D, we examine how changes in delta morphology can trigger variations in tidal signal, suspended and bed load transport, and how these could ultimately cause additional morphological changes. Our results show that a positive feedback between sediment deposition and tidal prism dominates the morphodynamic evolution of the delta. Accretion of the shoals in the delta front increases the dissipation of tides and decreases the tidal prism leading to weaker tidal flows. This reduction in tidal currents lowers the sediment flushing capacity of the system, promoting deposition on the shoals and tidal dissipation. This positive feedback potentially traps more sediment in the delta topset and possibly offsets the decrease in sediment load triggered by the construction of upstream dams, often present in tidal deltas.

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Section: Resultsmentioning

confidence: 99%

Section: Tidal Asymmetrymentioning

confidence: 99%

A Positive Feedback Between Sediment Deposition and Tidal Prism May Affect the Morphodynamic Evolution of Tidal Deltas

et al. 2018

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“…Residual flow causes a residual sediment transport in the same direction, and the tidal flow fluctuations strengthen it (Van de Kreeke & Robaczewska, 1993; Chu et al, 2015). Residual flow through a tidal inlet can be due to the following causes: Freshwater input.…”

Section: Sediment-sharing Systemmentioning

confidence: 99%

Sediment budget and morphological development of the Dutch Wadden Sea: impact of accelerated sea-level rise and subsidence until 2100

Wang

Elias

Spek

et al. 2018

Netherlands Journal of Geosciences

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The Wadden Sea is a unique coastal wetland containing an uninterrupted stretch of tidal flats that span a distance of nearly 500km along the North Sea coast from the Netherlands to Denmark. The development of this system is under pressure of climate change and especially the associated acceleration in sea-level rise (SLR). Sustainable management of the system to ensure safety against flooding of the hinterland, to protect the environmental value and to optimise the economic activities in the area requires predictions of the future morphological development.The Dutch Wadden Sea has been accreting by importing sediment from the ebb-tidal deltas and the North Sea coasts of the barrier islands. The average accretion rate since 1926 has been higher than that of the local relative SLR. The large sediment imports are predominantly caused by the damming of the Zuiderzee and Lauwerszee rather than due to response to this rise in sea level. The intertidal flats in all tidal basins increased in height to compensate for SLR.The barrier islands, the ebb-tidal deltas and the tidal basins that comprise tidal channels and flats together form a sediment-sharing system. The residual sediment transport between a tidal basin and its ebb-tidal delta through the tidal inlet is influenced by different processes and mechanisms. In the Dutch Wadden Sea, residual flow, tidal asymmetry and dispersion are dominant. The interaction between tidal channels and tidal flats is governed by both tides and waves. The height of the tidal flats is the result of the balance between sand supply by the tide and resuspension by waves.At present, long-term modelling for evaluating the effects of accelerated SLR mainly relies on aggregated models. These models are used to evaluate the maximum rates of sediment import into the tidal basins in the Dutch Wadden Sea. These maximum rates are compared to the combined scenarios of SLR and extraction-induced subsidence, in order to explore the future state of the Dutch Wadden Sea.For the near future, up to 2030, the effect of accelerated SLR will be limited and hardly noticeable. Over the long term, by the year 2100, the effect depends on the SLR scenarios. According to the low-end scenario, there will be hardly any effect due to SLR until 2100, whereas according to the high-end scenario the effect will be noticeable already in 2050.

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“…However, we adopted the wellreceived assumption of net sediment transport being governed by the M2 and M4 constituents, whose temporal variability is small in the Wadden Sea (Gräwe et al 2014). Chu et al (2015) investigated the importance of including more constituents into the modeled tidal forcing, concluding that interactions among M0, M2, M4, and M6 are the most important in absence of river discharge.…”

Section: Residual Transport and Balancing Mechanismsmentioning

confidence: 99%

“…Further enhancements of this approach were made by, e.g., Pritchard and Hogg (2003), Pritchard (2005), and Bartholdy (2000). On the other hand, the Eulerian FOR has been used to quantify net sediment transport by tidal asymmetries (e.g., Dronkers 1986; Van de Kreeke and Robaczewska 1993;Wang et al 1999;Chu et al 2015). Different frames of reference make it difficult to quantitatively compare the various mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

2017

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Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats' morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats' equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

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Analysis on residual coarse sediment transport in estuaries

Cited by 21 publications

References 27 publications

A Positive Feedback Between Sediment Deposition and Tidal Prism May Affect the Morphodynamic Evolution of Tidal Deltas

A Positive Feedback Between Sediment Deposition and Tidal Prism May Affect the Morphodynamic Evolution of Tidal Deltas

Sediment budget and morphological development of the Dutch Wadden Sea: impact of accelerated sea-level rise and subsidence until 2100

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

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