MONITORING FLUID MUD IN THE NORTH PASSAGE NAVIGATION CHANNEL OF YANGTZE ESTUARY, CHINA

AbstractA bottom quadrapod was deployed from March 29 to April 5, 2009 to measure bottom boundary layer (BBL) flows and nepheloid layer properties in the Deepwater Navigation Channel in the North Passage of Shanghai Port in the Yangtze estuary. Using a downward-looking acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter, detailed measurements of mean velocity and turbulence distribution within 1 m above the seabed were obtained. It appears that corrupted speeds measured for the deeper bins are caused by formation of the nepheloid layer at the seabed, implying that the ADCP is not a suitable instrument to measure current velocities in the bins nearest the seafloor. A statistical clustering method was used to characterize the current profiles in the BBL. The majority of current profiles within the BBL had a simple shape with current speed monotonically decreasing with depth, reflecting a logarithmic boundary layer. Phase-corrupted ADCP speeds measured for bins close to the bottom are shown to be useful as proxies to indicate the presence of primary and secondary lutoclines/nepheloid layers. A lutocline is a sediment-induced density gradient or pycnocline. The primary lutocline is closest to the bottom, and below it is the nepheloid layer, which is commonly composed of fluid mud. The proxies indicated that a nepheloid layer formed in the neap tide when the current velocity 1 m above the seabed dropped below a threshold of 0.65 m/s. The lutocline height was indicated to be about 0.2 m above the seabed. A secondary lutocline in the water column was also observed in the second half of the record, when the lowest maximum currents occurred.

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Analysis On Characters And Dynamic Mechanism Of The Storm-induced Fluid Mud In the North Passage of the Yangtze Estuary

10.5194/egusphere-egu2020-12649 ◽

2020 ◽

Author(s):

Jiufa Li ◽

Weihua Li ◽

Xiaohe Zhang

Keyword(s):

Storm Surge ◽

Density Profile ◽

Wave Energy ◽

Tidal Current ◽

Steep Slope ◽

Yangtze River Estuary ◽

Main Role ◽

Fluid Mud ◽

The North ◽

Navigation Channel

<p>The development of storm-induced fluid mud is an important factor to disturb the waterway transportation. Based on the observation data of fluid mud from 2010 to 2016, the basic characteristics and dynamic factors of the storm-induced fluid mud in the North Passage of the Yangtze River Estuary are analyzed. The main conclusions are as follows: (1) The sediment composition of the storm-induced fluid mud in the North Passage has little difference with the suspended sediment, which shows high correlation with the bed sediments in the middle/lower channel and the north beach of the North Passage, but the space difference of which is weak. (2) Large-thickness fluid mud in the North Passage mainly locates in the manual dredged navigation channel, and cannot stay in the steep slope beaches. It manly distributes between IIN-C and Y channel unit where is under the protection of the south and north embankments. (3) The storm-induced fluid mud in the North Passage characterizes as three stages. The primary-stage fluid mud develops during the storm surge, characterizes as low density, blurred upper and lower interfaces. It migrates quickly following the tidal current, and can be easily weaken by the peak tidal velocity. The development-stage fluid mud mainly occurs after the storm surge, characterizes as clear upper interface, "h" type density profile, with good stability and slowly migration. The dissipation-stage fluid mud characterizes as decreasing sediment amount, increasing sediment density, fuzzy lower boundary, "L" type or multi-steps type density profile, high stability and very weak flowability. (4) The cumulative wave energy during storm surge processes is the most important factor to determine the scale of the storm-induced fluid mud in the North Passage. The stronger the cumulative wave energy, the longer duration and the larger scale of the storm-induced fluid mud will develops. In addition, the weaker tidal power during the storm surge processes is favorable to the formation of the storm-induced fluid mud in the North Passage. Stronger tidal force would cause the shorter dissipation period of the storm-induced fluid mud. (5) The mechanism that up layer tidal current disturbs the fluid mud layer that make its sediment tends to dissipation and transport to the downstream and reciprocating following the tidal current, which plays the main role during the local extinction process of the storm-induced fluid mud in the North Passage. (6) The process of the high-sediment concentration gravity flow generates in the steep slope of the beach and near-bed invades to the manual dredged navigation channel during the storm surge process, is the key process mechanism for the rapid accumulation of storm-induced fluid mud in the North Passage.</p>

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THE BRANCHING CHANNEL NETWORK IN THE YANGTZE ESTUARY

Coastal Engineering Proceedings ◽

10.9753/icce.v33.sediment.69 ◽

2012 ◽

Vol 1 (33) ◽

pp. 69

Author(s):

Zheng Bing Wang ◽

Pingxing Ding

Keyword(s):

Yangtze Estuary ◽

River Delta ◽

Sediment Supply ◽

Channel Structure ◽

The South ◽

Channel Network ◽

The Yangtze Estuary ◽

The North ◽

Navigation Channel ◽

The Impact

The channels in the Yangtze Estuary have an ordered-branching structure: The estuary is first divided by the Chongming Island into the North Branch and the South Branch. Then the South Branch is divided into the North Channel and South Channel by the Islands Changxing and Hengsha. The South Channel is again divided into the North and South Passage by the Jiuduansha Shoal. This three-level bifurcation and four-outlet configuration appears to be a natural character of the estuary, also in the past (Chen et al., 1982), although the whole system has been extending into the East China Sea in the southeast direction due to the abundant sediment supply from the Yangtze River. Recently, the natural development of the system seems to be substantially disturbed by human interferences, especially the Deep Navigation Channel Project. For the understanding of the behaviour of the bifurcating channel system in the estuary we present analysis on two aspects: (1) the equilibrium configuration of river delta distributary networks, and (2) influence of tidal flow on the morphological equilibrium of rivers. Based on the analyses we conclude that the branching channel structure of the Yangtze Estuary can be classified as tide-influenced river delta distributary networks. Its basic structure is the same as in case of river dominated delta. The empirical relations describing the basic features of the river-dominated distributary delta networks can be explained by theoretical analysis, although they are not fully satisfied by the Yangtze Estuary because of the influence of the tide. Two major influences of the tide are identified, viz. increasing the resistance to the river flow into the sea and increasing the sediment transport capacity. As consequence of these two influences the cross-sectional area of the river/estuary increases in the seawards direction and the bed slope decreases. The insights from the analyses are helpful for the understanding of the impact of the Deep Navigation Channel Project on the large scale morphological development of the estuary.

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Morphodynamic Characteristics and Medium-Term Simulation of the North—South Passage Under the Impact of the Yangtze Estuary Deepwater Navigation Channel Project

China Ocean Engineering ◽

10.1007/s13344-020-0019-3 ◽

2020 ◽

Vol 34 (2) ◽

pp. 198-209

Author(s):

Jian Jiao ◽

Xi-ping Dou ◽

Xiang-yu Gao ◽

Lei Ding ◽

Xiao-yu Yang

Keyword(s):

Yangtze Estuary ◽

Medium Term ◽

The Yangtze Estuary ◽

The North ◽

Navigation Channel ◽

The Impact

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PILOT STUDY ON NAVIGATION CHANNEL REGULATION WORKS IN THE NORTH CHANNEL, YANGTZE ESTUARY

Coastal Engineering Proceedings ◽

10.9753/icce.v32.management.39 ◽

2011 ◽

Vol 1 (32) ◽

pp. 39

Author(s):

Min Gao ◽

Dano Roelvink

Keyword(s):

Pilot Study ◽

Numerical Modelling ◽

Tidal Flow ◽

Yangtze Estuary ◽

Future Studies ◽

Channel Regulation ◽

The North ◽

Navigation Channel ◽

Morphological Processes ◽

Near Future

It is estimated that the waterway in North Passage would not be able to meet the demand of shipping development soon and it is necessary to open a new deep navigation channel with a depth of 10 m in North Channel in the near future. A pilot study on the regulation of North Channel was proposed by Yangtze Estuary Waterway Administration Bureau and Prof. Dano Roelvink from UNESCO-IHE. The idea of regulating the navigation channel in North Channel was raised based on an analysis of morphological processes in this area. Multiple regulation plans were proposed, amongst which a configuration to regulate the North Channel was suggested after a study on a numerical modelling of tidal flow and morphological processes. Some suggestions were put forward for future studies.

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Simulation to Investigate the Reasons for the Sediment Deposition in the Upper Reach of the Deepwater Navigation Channel in the Changjiang River Estuary

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.610-613.1237 ◽

2012 ◽

Vol 610-613 ◽

pp. 1237-1241

Author(s):

Jie Gu ◽

Wei Chen ◽

Xin Qin ◽

Dan Qing Ma ◽

Xiao Li Wang ◽

...

Keyword(s):

River Estuary ◽

Sediment Deposition ◽

Changjiang River ◽

Changjiang River Estuary ◽

The Changjiang River ◽

The North ◽

Velocity Magnitude ◽

Navigation Channel ◽

The Changjiang River Estuary ◽

Set Up

At present, the upper reach of the Deepwater Navigation Channel is silted heavily, which brings negative influences on navigation. A two-dimensional numerical model is set up to simulate the hydrodynamics of the Changjiang River Estuary with Delft3D-FLOW in this paper. This model has been validated with the observed tidal level, flow velocity magnitude and direction, and the computed results agree well with the observed data, which also shows the model can well simulate the hydrodynamics of the Changjiang River Estuary caused by the Deepwater Navigation Channel Project. Based on the analysis of computed results, especially the velocity along the South Passage and North Passage, the flood and ebb flow in the Hengsha Passage, and the flow spilt ratio of South Passage and North Passage, it presents that one fundamental reason for the sediment deposition in the upper reach of the Deepwater Navigation Channel is that the velocity along the North Passage is far less than that along South Passage, above all, the velocity in North Passage upstream of the Hengsha Passage is even smaller; another reason is that the flood and ebb flow of Hengsha Passage are large, which weakens the water exchange between the North Passage and South Channel.

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Effects of waves and currents on the siltation problem of Damietta harbour, Nile Delta coast, Egypt

Mediterranean Marine Science ◽

10.12681/mms.152 ◽

2007 ◽

Vol 8 (2) ◽

pp. 33 ◽

Cited By ~ 5

Author(s):

ABO BAKER.I. ABO ZED

Keyword(s):

Sediment Transport ◽

Nile Delta ◽

Monitoring Program ◽

Wave Direction ◽

Littoral Drift ◽

Wave Refraction ◽

The North ◽

Dynamic Factors ◽

Navigation Channel ◽

Nile Delta Coast

This study evaluates the effect of prevailing dynamic factors on the sedimentation process in Damietta Harbour along the Nile delta coast of Egypt. The monitoring program spanned the period between 1978 and 1999 and included measurements of waves, currents and bathymetric profiles. The evaluation was based on determination of erosion and accretion rates, current regime, sediment transport, wave characteristics and wave refraction. Results revealed that the predominant wave direction from N-NW sector (86 %) throughout the year is responsible for generation of a longshore eastward current. Less frequent waves from the N-NE sector generate an opposing longshore westward current. The refraction pattern for the prevailing wave direction indicates that the harbour and its navigation channel are located within a divergence of wave orthogonal and in an accretion sediment sink area. The annual net rate of littoral drift on the western side of the harbour is about 1.43 * 105 m3 (accretion), while the annual net rate of littoral drift on the eastern side is about 2.54 * 105 m3 (erosion). Currents fluctuate tremendously in speed and direction, especially during the winter months. Hence, sediment transport takes place in offshore, eastward, and onshore directions. Progressive vector diagrams show that the largest near bottom offshore, onshore and easterly net drift occurs during summer, spring and winter respectively. The onshore sediment transport generated during spring and summer plays an important role in the redistribution of eroded sediments during the winter. The overall study of dynamic factors indicated that the harbour site is characterized by eastern, western, offshore and onshore sediment movements. Therefore, the north-south orientation of the navigation channel, with its depth greater than the surrounding area, interrupts sediment drift from different directions and reduces the current speed. Consequently, the sediments sink within the navigation channel from different directions. The sources of sediments contributing to the siltation process of the harbour and its navigation channels are mainly derived from the Rosetta promontory, Burullus beaches, Damietta promontory and from offshore and the dumping area.

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A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater Channel

10.5194/egusphere-egu21-6964 ◽

2021 ◽

Author(s):

Yue Li ◽

Peng Hu ◽

Ji Li

Keyword(s):

Current Model ◽

Yangtze Estuary ◽

Fluid Mud ◽

Governing Equations ◽

The Yangtze Estuary ◽

Simple Movement ◽

Two Layer Model ◽

Layer Flow ◽

Deepwater Channel ◽

Volume Method

<p>The Yangtze Estuary Deepwater Channel Project has brought great economic and social benefits since its completion, but the siltation problem is still worthy of attention. In order to investigate the mechanisms of fluid mud in the estuary and to study the influence of fluid mud on siltation in the Yangtze Estuary Deepwater Channel, a two-dimensional physically-enhanced two-layer flow model will be developed in this paper. The model includes two series of governing equations which are about environment fluid and fluid mud, respectively. The model is based on the unstructured grid, and the governing equations are discretized by the finite volume method, and the improved LTS/GMaTS technology is used to improve the computational efficiency. Firstly, an experiment that the fluid mud was flowing underwater along a gentle slope is reconstructed by the two-layer model. It shows the ability of the model to describe the simple movement of fluid mud. Secondly, the model is applied to Yangtze Estuary. Without the fluid mud layer, the model can be simplified as a tide-current model. The reliability of the tidal current and tide level is verified, and it means the model can describe the tide accurately. Based on this, the process of formation, transport, and break-down of fluid mud is simulated and its effect on the siltation in the Yangtze Estuary Deepwater Channel is estimated.</p>

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