Numerical modelling of turbidity currents in the Xiaolangdi reservoir, Yellow River, China

Hu, Peng; Cao, Zhixian; Pender, Gareth; Tan, Guojun

doi:10.1016/j.jhydrol.2012.06.032

Cited by 64 publications

(61 citation statements)

References 46 publications

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“…Sediment deposition by turbidity currents affects their storage capacity, which can have significant strategic importance in locations affected by rapid siltation, such as the large reservoirs along the Yellow River in China (Hu et al, 2012;Wei et al, 2013). Turbidity current deposition can also impair navigation and block intake structures, whilst flushing of sediment can impact locations further downstream (Fan and Morris, 1992;De Cesare et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Talling

Paull

Piper

2013

Earth-Science Reviews

211

184

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Subaqueous sediment density flows are one of the volumetrically most important processes for moving sediment across our planet, and form the largest sediment accumulations on Earth (submarine fans). They are also arguably the most sparely monitored major sediment transport processes on our planet. Significant advances have been made in documenting their timing and triggers, especially within submarine canyons and delta-fronts, and freshwater lakes and reservoirs, but the sediment concentration of flows that run out beyond the continental slope has never been measured directly. This limited amount of monitoring data contrasts sharply with other major types of sediment flow, such as river systems, and ensure that understanding submarine sediment density flows remains a major challenge for Earth science. The available monitoring data define a series of flow types whose character and deposits differ significantly. Large (N 100 km 3 ) failures on the continental slope can generate fast-moving (up to 19 m/s) flows that reach the deep ocean, and deposit thick layers of sand across submarine fans. Even small volume (0.008 km 3 ) canyon head failures can sometimes generate channelised flows that travel at N 5 m/s for several hundred kilometres. A single event off SE Taiwan shows that river floods can generate powerful flows that reach the deep ocean, in this case triggered by failure of recently deposited sediment in the canyon head. Direct monitoring evidence of powerful oceanic flows produced by plunging hyperpycnal flood water is lacking, although this process has produced shorter and weaker oceanic flows. Numerous flows can occur each year on river-fed delta fronts, where they can generate up-slope migrating crescentic bedforms. These flows tend to occur during the flood season, but are not necessarily associated with individual flood discharge peaks, suggesting that they are often triggered by delta-front slope failures. Powerful flows occur several times each year in canyons fed by sand from the shelf, associated with strong wave action. These flows can also generate up-slope migrating crescentic bedforms that most likely originate due to retrogressive breaching associated with a dense near-bed layer of sediment. Expanded dilute flows that are supercritical and fully turbulent are also triggered by wave action in canyons. Sediment density flows in lakes and reservoirs generated by plunging river flood water have been monitored in much greater detail. They are typically very dilute (b 0.01 vol.% sediment) and travel at b 50 cm/s, and are prone to generating interflows within the density stratified freshwater. A key objective for future work is to develop measurement techniques for seeing through overlying dilute clouds of sediment, to determine whether dense near-bed layers are present. There is also a need to combine monitoring of flows with detailed analyses of flow deposits, in order to understand how flows are recorded in the rock record. Finally, a source-to-sink approach is needed because the character of subm...

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Section: Introductionmentioning

confidence: 99%

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Talling

Paull

Piper

2013

Earth-Science Reviews

211

184

View full text Add to dashboard Cite

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“…However, the measured data contained many uncertainties because of the disadvantageous field conditions or the limitations of measuring method. In addition, the measured interface elevation was highly sensitive to the threshold sediment concentration for identifying the surface position of the underflow (Hu et al, 2012).…”

Section: Model Verificationmentioning

confidence: 99%

“…Hu and Cao (2009) developed a depth-averaged model for turbidity currents over erodible beds, based on rigorous conservative laws coupling the processes of flow-sediment transport and bed evolution. The proposed model was applied to simulate turbidity current events occurring in the Xiaolangdi Reservoir (Hu et al, 2012). As pointed out by Cao et al (2015), models of this type are restricted to predicting the propagation of turbidity currents after their formation.…”

Section: Introductionmentioning

confidence: 99%

“…As pointed out by Cao et al (2015), models of this type are restricted to predicting the propagation of turbidity currents after their formation. Therefore, the application of these models usually focused on typical case studies with specified inflow conditions (e.g., Bradford and Katopodes, 1999a, b;Sequeiros et al, 2009), or depended on observed data downstream of the plunge point for reservoir turbidity currents (e.g., Hu et al, 2012). However, in-situ measurements around the plunge location in a turbidity current event are rare owing to the Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 12:38 AM unsteady characteristic.…”

Section: Introductionmentioning

confidence: 99%

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One-dimensional morphodynamic model coupling open-channel flow and turbidity current in reservoir

Wang

Xia

Deng

et al. 2016

Journal of Hydrology and Hydromechanics

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Traditional depth-averaged morphodynamic models for turbidity currents usually focus on the propagation of currents after plunging. However, owing to the unsteady characteristic of the plunge point locations and the tough conditions of field measurement within the plunge zone in a reservoir, it is difficult in practice to directly provide upstream boundary conditions for these models. A one-dimensional (1D) morphodynamic model coupling open-channel flow and turbidity current in a reservoir was proposed to simulate the whole processes of turbidity current evolution, from formation and propagation to recession. The 1D governing equations adopted are applicable to open-channel flows and turbidity currents over a mobile bed with irregular cross-section geometry. The coupled solution is obtained by a two-step calculation mode which alternates the calculations of open-channel flow and turbidity current, and a plunge criterion is used to determine the location of the upstream boundary for the turbidity current, and to specify the corresponding boundary conditions. This calculation mode leads to consecutive predictions of the hydrodynamic and morphological factors, from the open-channel reach to the turbidity current reach. Turbidity current events in two laboratory experiments with different set-ups were used to test the capabilities of the proposed model, with the effect of free-surface gradient also being investigated. A field-scale application of the coupled model was conducted to simulate two turbidity current events occurring in the Sanmenxia Reservoir, and the method for calculating the limiting height of aspiration was adopted to estimate the outflow discharge after the turbidity currents arrived in front of the dam. The predicted plunge locations and arrival times at different cross-sections were in agreement with the measurements. Moreover, the calculated interface evolution processes and the sediment delivery ratios also agreed generally with the observed results. Therefore, the 1D morphodynamic model proposed herein can help to select the design capacity of the outlets, and optimize the procedure for sediment release in reservoirs.

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“…Layer-averaged refers to the fact that the physical quantities (velocity and sediment concentration) are averaged along the thickness of the turbidity currents. However, to date, most existing layer-averaged models for turbidity currents are single layer-averaged models, in which the upper clear-water flow is ignored and not modeled at all (e.g., Fukushima et al 1985;Parker et al 1986;Choi 1998;Bradford and Katopodes 1999a, b;Sequeiros et al 2009;Hu et al 2012;Lai and Wu 2013). Thus they are restricted to modeling the propagation of turbidity currents after their formation.…”

Section: Introductionmentioning

confidence: 99%

Whole-Process Modeling of Reservoir Turbidity Currents by a Double Layer-Averaged Model

Cao

Pender

et al. 2015

J. Hydraul. Eng.

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Turbidity current is formed as subaerial open-channel sediment-laden flow plunges into a reservoir. The whole process of reservoir turbidity current, i.e., formation, propagation, and recession, is generally controlled by the water and sediment inputs from upstream and also the reservoir operation scheme specifying the downstream boundary condition. Enhanced understanding of reservoir turbidity current is critical to effective sediment management in alluvial rivers. However, until now there has been a lack of physically based and practically feasible models for resolving the whole process of reservoir turbidity current. This is because the computing cost of three-dimensional modeling is excessively high. Also, single layer-averaged models cannot resolve the formation process characterized by the transition from open-channel sediment-laden flow to subaqueous turbidity current, or the upper clear-water flow as dictated by the operation scheme of the reservoir, which has significant impacts on turbidity current. Here a new two-dimensional double layer-averaged model is proposed to facilitate for the first time whole-process modeling of reservoir turbidity current. The two hyperbolic systems of the governing equations for the two layers are solved separately and synchronously. The model is well balanced because the interlayer interactions are negligible compared with inertia and gravitation, featuring a reasonable balance between the flux gradients and the bed or interface slope source terms and thus applicable to irregular topographies. The model is benchmarked against a spectrum of experimental cases, including turbidity currents attributable to lock-exchange and sustained inflow. It is revealed that an appropriate clear-water outflow is favorable for turbidity current propagation and conducive to improving sediment flushing efficiency. This is significant for optimizing reservoir operation schemes. As applied to turbidity current in the Xiaolangdi Reservoir in the Yellow River, China, the model successfully resolves the whole process from formation to recession. The present work facilitates a viable and promising framework for whole-process modeling of turbidity currents, in support of reservoir sediment management.

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Numerical modelling of turbidity currents in the Xiaolangdi reservoir, Yellow River, China

Cited by 64 publications

References 46 publications

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

One-dimensional morphodynamic model coupling open-channel flow and turbidity current in reservoir

Whole-Process Modeling of Reservoir Turbidity Currents by a Double Layer-Averaged Model

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