Long-term, process-based morphodynamic modeling of a fluvio-deltaic system, part I: The role of river discharge

Guo, Leicheng; Wegen, Mick van der; Roelvink, Dano; Wang, Zheng Bing; He, Qing

doi:10.1016/j.csr.2015.09.002

Cited by 46 publications

(55 citation statements)

References 45 publications

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“…The relative strength of fluvial and tidal discharges is the key factor governing the estuarine pattern formation. Model results indicate that larger river discharges (

Q_{R}

) result in more pronounced delta formation (for both M2D and M3D runs) because of the stronger erosion of sediment from the upstream river bed (Figure ), which was also reported in Zhou et al () and Guo et al (). The distributary channels appear to be deeper when

Q

is larger, due to the river‐enhanced ebb current.…”

Section: Resultssupporting

confidence: 82%

“…A schematic model bathymetry of an exponentially convergent estuary is designed following Guo et al (). To prevent the flood tide from reaching the river boundary, a relatively long estuary of approximately 800 km is considered (Figure ;

x

‐ and

y

‐directions respectively represent along‐ and across‐estuary directions).…”

Section: Methodsmentioning

confidence: 99%

“…Schematic view of the model domain with dimensions similar to Guo et al (). Note that the scales are distorted in the plot…”

Section: Methodsmentioning

confidence: 99%

“…The estuarine environment is normally characterized by fine and cohesive sediment, so mud is considered in this study, unlike several existing studies (e.g. Zhou et al, 2014a;Guo et al, 2015b). Fine sediment is treated as suspended load, which can be highly affected by baroclinic effects induced by salinity gradients (Dalrymple and Choi, 2007).…”

Section: Numerical Model Descriptionmentioning

confidence: 99%

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The role of salinity in fluvio‐deltaic morphodynamics: A long‐term modelling study

Zhou

Tao

Gong

et al. 2020

Earth Surf Processes Landf

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Salinity difference between terrestrial river discharge and oceanic tidal water plays a role in modifying the local flow field and, as a consequence, estuarine morphodynamics. Although widely recognized, recent numerical studies exploring the long‐term morphological evolution of river‐influenced estuaries with two‐dimensional, depth‐averaged models have mostly neglected salinity. Using a three‐dimensional morphodynamic model, we aim to gain more insight into the effect of salinity on the morphodynamics of fluvio‐deltaic systems. Model results indicate that the resultant estuarine morphology established after 600 years differs remarkably when a salinity gradient is included. A fan‐shaped river‐mouth delta exhibits less seaward expansion and is cut through by narrower channels when salinity is included. The inclusion of salinity tends to generate estuarine circulation, which favours landward sediment transport and hence limits the growth of the delta while enhancing the development of intertidal areas. The formation of deltaic channel–shoal patterns resulting from morphodynamic evolution tends to strengthen salinity stratification, which is characterized by an increased gradient Richardson number. The direction of the depth‐averaged residual sediment transport over a tide may be opposite to the direction of residual velocity, indicating the significant influence of baroclinic effects on the net sediment transport direction (and hence morphological change). The effect of salinity on morphological evolution becomes less profound when the strength of tidal or fluvial forcing is dominant over the other. The effects of sediment type and flocculation, which are particularly important when salinity gradients are present, are also discussed. Overall, this study highlights that neglecting salinity to simulate long‐term estuarine morphodynamics requires more careful justification, particularly when the environment is characterized by fine sediment types (favouring suspended transport), and relatively large river discharge and estuarine depth (favouring baroclinic effects). © 2020 John Wiley & Sons, Ltd.

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“…The relative strength of fluvial and tidal discharges is the key factor governing the estuarine pattern formation. Model results indicate that larger river discharges (

Q_{R}

Q

is larger, due to the river‐enhanced ebb current.…”

Section: Resultssupporting

confidence: 82%

x

‐ and

y

‐directions respectively represent along‐ and across‐estuary directions).…”

Section: Methodsmentioning

confidence: 99%

“…Schematic view of the model domain with dimensions similar to Guo et al (). Note that the scales are distorted in the plot…”

Section: Methodsmentioning

confidence: 99%

Section: Numerical Model Descriptionmentioning

confidence: 99%

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The role of salinity in fluvio‐deltaic morphodynamics: A long‐term modelling study

Zhou

Tao

Gong

et al. 2020

Earth Surf Processes Landf

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“…The arc in the figure corresponds to a break in scaling behavior of channel depth, width and the ratio between tidal and fluvial discharges, which splits the distributary channels into parts where the river discharge dominates the channel morphology (dark blue) and parts where the tidal discharge is dominant (purple In a predefined modeling domain, subaqueous patterns of channels and shoals can be predicted. This is here illustrated for an idealized setting under combined river and tidal forcing 50 . The terminal estuarine morphology and residual sediment transport vectors are shown based on model simulations with an increasing river discharge (Q).…”

mentioning

confidence: 99%

Tidal controls on river delta morphology

et al. 2017

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River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world's largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology.Tides interacting with river discharge can play a crucial role in the morphodynamic development of delta channels under pressure. Emerging insights into tidal controls on river delta morphology suggest that -despite the active morphodynamics in tidal channels and mouthbar regions -tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing nonlinear interactions between river discharge and the tide that lead to flow changes within channels and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.3

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The effect of asymmetric dune roughness on tidal asymmetry in the Weser estuary

Herrling

Becker

Lefebvre

et al. 2021

Earth Surf Processes Landf

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The bed of estuaries is often characterized by ripples and dunes of varying size.Whereas smaller bedforms adapt their morphological shape to the oscillating tidal currents, large compound dunes (here: asymmetric tidal dunes) remain stable for periods longer than a tidal cycle. Bedforms constitute a form roughness, that is, hydraulic flow resistance, which has a large-scale effect on tidal asymmetry and, hence, on hydrodynamics, sediment transport, and morphodynamics of estuaries and coastal seas. Flow separation behind the dune crest and recirculation on the steep

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Long-term, process-based morphodynamic modeling of a fluvio-deltaic system, part I: The role of river discharge

Cited by 46 publications

References 45 publications

The role of salinity in fluvio‐deltaic morphodynamics: A long‐term modelling study

The role of salinity in fluvio‐deltaic morphodynamics: A long‐term modelling study

Tidal controls on river delta morphology

The effect of asymmetric dune roughness on tidal asymmetry in the Weser estuary

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