Modelling hyperconcentrated flow in the Yellow River

Maren, D.S. van; Winterwerp, Johan C.; Wang, Baosheng; Zhou, Jianjun

doi:10.1002/esp.1760

Cited by 82 publications

(31 citation statements)

References 29 publications

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“…In that case, σ t should be closer to 2. In a model with comparable vertical resolution as applied here, the observed sediment-induced stratification effects during hyperconcentrated floods could only be reproduced using a Prandtl-Schmidt number of 2 (van Maren et al 2009). …”

Section: Hydraulic Dragmentioning

confidence: 90%

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

2015

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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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Section: Hydraulic Dragmentioning

confidence: 90%

“…Previous work showed that this term is essential to capture the suspended sediment dynamics in high-concentration environments (Winterwerp and van Kessel 2003;van Maren 2007;van Maren et al 2009). However, in this study, the sedimentinduced density effects only limitedly influenced the hydrodynamics and sediment dynamics.…”

Section: Hydraulic Dragmentioning

confidence: 99%

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

2015

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“…Determining when a flow is hyperconcentrated is not straightforward because hyperconcentrated flow has not been properly defined until now (Qian et al 1979;Wang 1996;Jiao 2004). It is usually classified based on the magnitude of C value (van Maren et al 2009). In the study area, Xu (1999aXu ( , 2002 gave a threshold C of 300 kg m -3 .…”

Section: The Development Of Hyperconcentrated Flowmentioning

confidence: 99%

Spatial scale dependence of sediment dynamics in a gullied rolling loess region on the Loess Plateau in China

Fang

Qiangguo

et al. 2010

Environ Earth Sci

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Sediment dynamics is still imperfectly understood, especially at spatial scale in the highly erodible region of the Loess Plateau, and few studies have been heretofore conducted. Using 5-year continuous water and sediment records, three plots and three basins in the gullied rolling loess region were selected and sediment dynamics at spatial scale was studied. Results showed that the floods, where the peak discharge (Q p ) did not come earlier than the sediment peak, were predominant in slope zones, occupying [90 and [70% of the total for the Mao slope and for the Entire slope, respectively. However, in basins, most of the sediment peaks (C p ) lagged behind Q p , implying that slope zone was the main origin of sediment. More than 50% of the events presented clockwise hysteresis loops in the Mao slope area, while almost all the events had anticlockwise hysteresis loops in basins. This can be attributed to less occurring frequency of hyperconcentrated flow, as well as its instability in slope zones, compared to those in the basins. Within these contexts, gravitational erosion made the highest sediment concentration (C) in Tuanshangou basin and median developing status of C-discharge (C-Q) relationships in the Entire slope area. This study provides insights into the protection of slope surface and disruption of the development of hyperconcentrated flow to reduce soil loss.

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“…However, at such concentrations, the fall velocity decreases due to hindered settling, therefore leading to a more uniform distribution of sediment over the water column and reducing stratification. This phenomenon has for example been observed in the Yellow River (Van Maren et al 2009). …”

Section: Extension To Tidal Flowsmentioning

confidence: 66%

“…, with σ ρ = 2 (Van Maren et al 2009). At the bed, sediment deposits at a rate D and erodes at rate E, which are described by…”

Section: Model Equationsmentioning

confidence: 99%

The hyperturbid state of the water column in estuaries and rivers: the importance of hindered settling

2018

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Over the last few decades, some estuaries have undergone a transition to a hyperturbid state, characterised by suspended sediment concentrations of several grammes per litre averaged over the water column. To improve our understanding of this transition and of naturally hyperturbid estuaries, we systematically identify the processes allowing for high suspended sediment concentrations using a water column (1DV) model. Under a range of realistic forcing conditions, the state of the water column can be characterised by one of two equilibrium states. The first is an erosion-limited state, in which there still is sediment available for erosion at the bed. We find that this state only occurs with relatively low concentrations. The second is a supply-limited state, in which all erodable sediment is in suspension. The concentration in this state depends entirely on the amount of sediment in the system and can potentially be very high. We identify the conditions under which the state of the water column can jump from a low to a high concentration and identify hysteresis in the transition between the two states. The mechanism responsible for this hysteresis is hindered settling. It thus follows that hyperturbidity is only possible in a supply-limited state. From this observation we derive a necessary condition for an estuarine system to make the transition from low turbidity to hyperturbidity in a 1DV context. This is an important step towards understanding why some estuaries are hyperturbid and assessing the risk that particular estuaries may become hyperturbid in the future.

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Modelling hyperconcentrated flow in the Yellow River

Cited by 82 publications

References 29 publications

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

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

Spatial scale dependence of sediment dynamics in a gullied rolling loess region on the Loess Plateau in China

The hyperturbid state of the water column in estuaries and rivers: the importance of hindered settling

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