• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.5 no.4
• /
• pp.296-301
• /
• 1993

A hydrodynamic solution for the lateral spreading of a river plume which was developed by assuming a Gaussian distribution of density difference between a turbulent jet river plume and ambient salt water is verified by the field data in the Nakdong river plume. Effect of the river plume on the transport of fine-grained suspended sediment at the Nakdong Estuary is also examined. The analysis of fold data showed a reasonably good correspondence with the theoretical solution adopted in this work Therefore, the hydrodynamic solution can be used as a useful tool in dealing with the lateral spreading of a river plume. The density stratification due to the existence of a river plume seems to cause a retarded settling of the suspended sediments in the water column. and thus a farther transport of the fine sediment is expected than in the normal steady flow.

• Journal of the korean society of oceanography
• /
• v.39 no.1
• /
• pp.26-34
• /
• 2004

The evolution of intricate and striking patterns of suspended sediments (SS), which are created by certain physical dynamics in the East China and Yellow Seas, has been investigated using satellite ocean color imageries and vertical profiles of particle attenuation and backscattering coefficients. The structure of these patterns can reveal a great deal about the process underlying their formation. Sea surface temperature (SST) analyzed from the Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data were used to elucidate the physical factors responsible for the evolution of suspended sediment patterns in the East China Sea. The concomitant patterns of suspended sediments were tracked from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data. The detailed examination about these patterns gave birth to the definition of the evolution of suspended sediments (SS) into four stages: (1) Youth or Infant stage, (2) Younger stage, (3) Mature stage, and (4) Old stage. We describe about the three directional forces of the tidal currents, ocean warm currents and estuarine circulations that lead to occurrence of various stages of the evolution of suspended sediments that increase turbidity at high levels through out the water column of the inner and outer shelf areas during September to April. The occurrence of these four stages could be repeatedly observed. In contrast, vertical profiles of the particle attenuation ($c_{p}$) and backscattering ($b_{bp}$) coefficients displayed obvious patterns of the propagation of suspended sediment plume from the southwestern coastal sea that leads to eventual collision with the massive sediment plume originating from the Yangtze banks of the East China Sea.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5B
• /
• pp.557-562
• /
• 2006

In order to predict the dispersion of suspended sediment arising from dredging operation in port and navigation channel, a hybrid model for dispersive transport of turbidity plume was developed using Lee's(1998) hybrid method. Using hybrid modeling scheme advection-diffusion equation was solved by the forward particle-tracking method for advection process and by the fixed Eulerian grid method for diffusion process. To examine numerical model simulation in accuracy, the simulated results for 1-D, 2-D, and 3-D cases were compared with the analytical solutions including Kuo, et al's (1985) 3-D mathematical model. The model results were in a good agreement with the analytical solutions and mathematical model for the dispersion of turbidity plume.

• Ocean and Polar Research
• /
• v.25 no.spc3
• /
• pp.399-408
• /
• 2003

The behavior of Suspended Sediment Concentrations (SSC) around a silt screen in a microtidal coastal area was hydrodynamically measured. The current speed at the mid-layer about 30m downstream of the screen reduces to about half that at the same distance upstream. It was caused by the contraction of the vertical section due to the screen. Even during a relatively weak storm period the SSC increases to that of the value caused by dredging. Section-averaged SSC at the downstream of the screen is higher by about 60% than that at the upstream, suggesting that the silt screen plays an adverse effect rather than a constructive role in the reduction of SSC generated by dredging.

• Korean Journal of Remote Sensing
• /
• v.27 no.3
• /
• pp.235-258
• /
• 2011

The purpose of this study is to investigate climatological variations from the temporal and spatial surface particulate organic carbon (POC) estimates based on SeaWiFS spectral radiance, and to determine the physical mechanisms that affect the distribution of pac in the Gulf of Mexico. 7-year monthly mean values of surface pac concentration (Sept. 1997 - Dec. 2004) were estimated from Maximum Normalized Difference Carbon Index (MNDCI) algorithm using SeaWiFS data. Synchronous 7-year monthly mean values of remote sensing data (sea surface temperature (SST), sea surface wind (SSW), sea surface height anomaly (SSHA), precipitation rate (PR)) and recorded river discharge data were used to determine physical forcing factors. The spatial pattern of POC was related to one or more factors such as river runoff, wind-derived current, and stratification of the water column, the energetic Loop Current/Eddies, and buoyancy forcing. The observed seasonal change in the POC plume's response to wind speed in the western delta region resulted from seasonal changes in the upper ocean stratification. During late spring and summer, the low-density river water is heated rapidly at the surface by incoming solar radiation. This lowers the density of the fresh-water plume and increases the near-surface stratification of the water column. In the absence of significant wind forcing, the plume undergoes buoyant spreading and the sediment is maintained at the surface by the shallow pycnocline. However, when the wind speed increases substantially, wind-wave action increases vertical motion, reducing stratification, and the sediment were mixed downward rather than spreading laterally. Maximum particle concentrations over the outer shelf and the upper slope during lower runoff seasons were related to the Loop Current/eddies and buoyancy forcing. Inter-annual differences of POC concentration were related to ENSO cycles. During the El Nino events (1997-1998 and 2002-2004), the higher pac concentrations existed and were related to high runoffs in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico. During La Nina conditions (1999-2001), low Poe concentration was related to normal or low river discharge, and low PM/nutrient waters in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico.

• Environmental Engineering Research
• /
• v.17 no.3
• /
• pp.167-174
• /
• 2012

In situ particle size spectra are obtained from two sequent cruises in order to evaluate the physical consequences of suspended particulate matters caused by episodic storm runoff from the Santa Ana River watershed, an urbanized coastal watershed. Suspended particles from various sources including surface runoff, near-bed resuspension, and phytoplankton are identified in empirical orthogonal function (EOF) analysis and an entropy-based parameterization (Shannon entropy). The first EOF mode is associated with high turbidity and fine particles as indicated by the elevated beam attenuation near the Santa Ana River and Newport Bay outlets, and the second EOF mode explains the suspended sediment dispersal and particle coarsening at the near-surface plume. Chlorophyll particles are also distinguished by negative magnitudes of the first EOF mode, which is supported by the relationship between fluorescence and beam attenuation. The integrated observation between the first EOF mode and the Shannon entropy index accentuates the characteristics of two different structures and/or sources of sediment particles; the near-surface plumes are originated from runoff water outflow, while the near-bottom particles are resuspended due to increased wave heights or mobilizing bottom turbidity currents. In a coastal pollution context, these methods may offer useful means of characterizing particle-associated pollutants for purposes of source tracking and environmental interpretation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.5 no.4
• /
• pp.295-304
• /
• 2000

Vertical measurement of CTDT at about 30 min intervals and spatial surface temperature, salinity, and concentration of suspended particulate matters were conducted to elucidate the character of water column and the dispersal pattern in a floating ice-dominated fjord, Marian Cove, West Antarctica. Marian Cove showed two distinct water layers in terms of turbidity; 1) cold, fresh, and turbid surface plume in the upper 2 m,2) warm, saline, and relatively clean Maxwell Bay inflow between 15-45 m in water depth. Thermal melting of Maxwell Bay inflow and tidewater glacier/floating ices developed the surface mixed layer and the activity of floating ices cause Maxwell Bay inflow to be unstable. Due to the unstable water column, the development of Maxwell Bay inflow and subsequent surface plume are not influenced by tidal frequency. Coastal current generated by strong northwesterly wind may extend warm, saline, and turbid surface plume into the central part of the cove along the northern coast via the western coast of Weaver Peninsula. Terrigenous sediments of meltwaters from the glaciated ice cliffs near the corner of tidewater glacier and some coasts enter into the cove and their dispersion depends upon the hydrographic regimes (tide, wind, wave etc.). At the period of spring tide, the strong wind stress with the northwesterly wind direction reserve suspended sediment-fed surface plume and so allow the possibility of deposition of terrigenous sediments within the basin of cove.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2001.05a
• /
• pp.154-159
• /
• 2001

Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from upper river was deposited at this area. It has caused many problems such as changes in topography and tidal current. In this paper, field observation data on tidal currents and sediments were investigated as well as historical topographic changes by dredging and reclamation of the foreshore. Then, the numerical model considered the settling velocity of the suspended solids according to the particle size was applied to examine the characteristic of deposition. The results are as follows : 1. Changes of characteristics of deposition were caused by topographic changes of Nakdong estuary 2. Characteristics of deposition were influenced by river plume and tidal currents. 3. Numerical model which considers settling velocity reappeared distribution of deposition by particle-size. 4. Used model is only resonable for discussion in the quality, so, it is strongly suggested that the new model development is needed including the quatitative deposition processes.

• Ocean and Polar Research
• /
• v.22 no.2
• /
• pp.69-80
• /
• 2000

A 3-D particle tracking model with normalized characteristic equations has been developed to predict the variation of near-field mixing characteristics and the far-field transport of the effluent plumes discharged from sea outfalls. The model was applied to the case study on the Masan sea outfall plumes discharged through a submerged multiport-diffuser. Numerical simulations of the effluent transport for 15 days which cover neap and spring tidal cycles in Masan Bay were conducted using fall velocities of the solid wastes and the initial plume characteristics obtained from normalized near-field characteristic equations. The results showed that time variations in near-field minimum dilutions with tidal ambient flow conditions are about $45{\sim}49$. Most of the heavy particles in the effluent plumes were settled and deposited in the vicinity of the outfalls immediately, and the finer particles were transported eastwards 3 km away from the outfalls for 15 days. A similar depositional trend of contaminated sediment was also found during a recent field survey.

• Ocean and Polar Research
• /
• v.36 no.4
• /
• pp.383-394
• /
• 2014

The surface sediments from the manganese nodule exploration area of Korea in the Clarion-Clipperton fracture zone were investigated to understand the resource potential of and emplacement mechanism for rare earth elements (REEs). The sediments are categorized into three lithological units (Unit I, II and III from top to bottom), but into two groups (Unit I/II and Unit III) based on the distribution pattern of REEs. The distribution pattern of REEs in Unit I/II is similar to that of Post-Archean Australian Shale (PAAS), but shows a negative Ce anomaly and enrichment in heavy REEs (HREEs). In Unit III, the HREE enrichment and Ce anomaly is much more remarkable than Unit I/II when normalized to PAAS, which are interpreted as resulting from the absorption of REEs from seawater by Fe oxyhydroxides that were transported along the buoyant plume from remotely-located hydrothermal vents. It is supported by the PAAS-normalized REE pattern of Unit III which is similar to those of seawater and East Pacific Rise sediments. Meanwhile, the PAAS-normalized REE pattern of Unit I/II is explained by the 4:1 mixing of terrestrial eolian sediment and Unit III from each, indicating the much smaller contribution of hydrothermal origin material to Unit I/II. The studied sediments have the potentiality of a low-grade and large tonnage REE resource. However, the mining of REE-bearing sediment needs a large size extra collecting, lifting and treatment system to dress and refine low-grade sediments if the sediment is exploited with manganese nodules. It is economically infeasible to develop low-grade REE sediments at this moment in time because the exploitation of REE-bearing sediments with manganese nodules increase the mining cost.