• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.3
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• pp.149-157
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• 1998

Seasonal changes of topography, sediment grain size and accumulation rate in the Gomso-Bay tidal flat, west coast of Korea, have been studied in order to understand the seasonal accumulation pattern and preservation potential of the tidal-flat sediments. Seasonal levelings across the tidal flat show that the landward movement of both intertidal sand shoals and cheniers accelerates during the winter and typhoon periods, but it almost stops in summer when mud deposition is instead predominant at the middle and upper tidal flats. Seasonal variations of mean grain size were largest on the upper part of middle tidal flat where summer mud layers were eroded during the winter and typhoon periods. Measurements of accumulation depths from sea floor to basal plate reveal that accumulation rates were seasonally controlled according to the elevation of tidal-flat surface. The upper tidal flat where the accumulation rate of summer was generally higher than that of winter was characterized by a continuous deposition throughout the entire year, whereas in the middle tidal flat, sediment accumulations were concentrated in winter relative to summer and were intermittently eroded by typhoons. The lower tidal flat were deposited mostly in winter and eroded during summer typhoons. Can cores taken across the tidal flat reveal that sand-mud interlayers resulting from such seasonal changes of energy regime are preserved only in the upper part of the deposits and generally replaced by storm layers downcore. Based on above results, it is suggested that the storm deposits by winter storms and typhoons would consist of the major part of the Gomso-Bay sediments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.283-293
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• 2006

The purpose of this study is to quantitatively estimate the erosional properties for cohesive sediments on Keum Estuary. Then the spatial variation was evaluated, through analyzing and comparing the seasonal variation of the erosional properties in Keum Estuary with that of the erosional properties in the other sites. As erosional properties of cohesive sediments are also influenced largely by basic physico-chemical property of cohesive sediments themselves, the impact that the basic physico-chemical property has on the erosional properties is analyzed in this study. Erosional tests are performed under the condition of uniform beds. Total 8 times of tests using an annular flume are also conducted in a location, low times respectively by seasons: the fall, winter. Experimental results of erosional tests show that the critical shear stress for erosion varies in the range of $0.12{\sim}0.36N/m^2$ and the coefficient of erosion rate varies in the range of $120.91{\sim}6.72mg/cm^2{\cdot}hr$, over the corresponding bulk-density range $1.15{\sim}1.34g/cm^3$. Although the calculated parameters of erosional properties are remarkably different in quantity compared with those of other cohesive sediments(lake Okeechobee) and Kaolinite, their seasonal variabilities within Keum Estuary appear to be insignificant.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.3
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• pp.83-92
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• 2004

A continuous monitoring of textural characteristics of surface sediments, sedimentation rates and beach profile was carried out to investigate the seasonal variations of sedimentary processes in the Imjado beach, southwestern coast of Korea for two years. The beach profiles consist of steep beach face and relatively flat middle and low tide beaches. The slope of the beach face increases in summer and decreases in winter, in good accordance with the standard beach cycle. Ridge and runnel systems are well developed in the middle and low tide beaches during the summer, but these structures are replaced by mega-ripples during the winter. The sediments are fining southward as well as landward. The mean grain-size tends to be increasingly coarser during seasons of autumn and winter on the north beach and during seasons of winter and spring on the south one. In addition, the sediments are eroded on the north beach and accumulated on the south one as a whole. These are probably due to southward transportation of the sediments as long-shore current (NE-SW) runs around the coastal line of the beach. However, the seasonal variations in accumulation rates are very complex and irregular. It is considered that the Imjado beach represents in non-equilibrium state, as a result of coastal and submarine topographic changes by artificial agents and sea-level uprising associated with global warming.

• Economic and Environmental Geology
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• v.35 no.2
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• pp.171-177
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• 2002

Two piston-core sediments, obtained from the southwestern margin of the Ulleung Basin in East Sea, are analyzed to investigate the stratigraphy and sedimentary environment of the Late Quaternary. The cores consist mainly of cuddy sediments with silty sands, lapilli tephra and ash layers. The chronostratigraphic correlation with known eruption ages reveals that the core sediments contain the stratigraphic document over the past 46.1 kyr and the sedimentation rates during the last glacial period were relatively higher (12.1-14.9 cm/kyr) than those in pelagic ocean. Several sedimentary facies, mainly affected by turbidity currents, are commonly present in the core interval accumulated during the oxygen-isotope stage 2. Many of horizontal voids, which are thought to have formed by gas expansion, are observed in fore 00GHP-07. The total organic carbon (TOC) contents of the core sediments are noticeably high (average 1 .8%). Particularly, these TOC valuers increased during Termination I, suggesting that dering this time interval the sedimentary environment of the study area was changed to more anoxic.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.67-72
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• 2007

A model for predicting potentials of land erosion and deposition over a natural basin was developed based on the mass balance principle. The program was developed based on sediment mass balance principle for each cell in a GIS. Sediment yield from a cell was estimated with RUSLE. The outflow sediment from a cell was calculated by multiplying the sediment yield of the cell by the sediment delivery ratio (SDR) of the cell. The outflow sediment from the upstream cell becomes the incoming sediment of the downstream cell. Therefore the erosion and deposition potential of each cell could be determined from the sediment mass balance i.e., the difference between the incoming and outflow of sediments of each cell. The developed model was validated by comparing the predicted sediment yields for three basins with measured data.

• Journal of the Korean earth science society
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• v.26 no.3
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• pp.253-267
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• 2005

Seasonal and spatial variations of tidal flat sediments were studied in Yeoja Bay. Results of the yearly observation of tidal flat transect lines indicated that the monthly change of grain size composition was not distinct from each tidal flat transect line, but it was quite clear that clay covered $40\~70\%$ of the sediment composition. Clay composed most highest in the northern part of the bay, and lowest in the western. As clay content increased, water and organic matter showed a tendency of increase, while the mean grain size was fixed per clay amount. Shear strength came out as 0 kPa as a whole. Seasonal variations of clay contents in each tidal flat were higher in winter and spring, but lower in summer and autumn. Thefine sediments were likely to be accumulated in the winter and spring. The average accumulation rate of each tidal flat was $-14.62\~38.57mm{\cdot}yr^{-1}$. The numbers showed $32.13mm{\cdot}yr^{-1}$ in the northern, $-14.62mm{\cdot}yr^{-1}$in the western, and $6.46mm{\cdot}yr^{-1}$ in the eastern part. During the coarse of this study sediment accumulation rates indicated that the sediments deposited continuously in the northern part of tidal flat, whereas erosion occurred in the western part. However, there was no distinct change in the eastern part. It was due to the clockwise lateral circulation in Yeoja Bay. Seasonally, sedimentation happened during the dry season (winter and spring) and erosion during the wet season (summer and autumn).

• Journal of Wetlands Research
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• v.6 no.1
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• pp.167-178
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• 2004

The southern tidal flat of Kanghwa Island is one of the biggest flats on the west coast of Korea. Tide is typically a semidiurnal with maximum range of about 10m. The tidal flat receives large amount of sediments from Han River system. Surface sediments for sedimentary analyses were sampled at 83 stations in the study area in August 2003. The surface sediments consisted of five sedimentary facies. Generally, sandy mud sediments dominated in the southern tidal flat of Kanghwa Island, whereas sand sediments dominated in channel and subtidal zones of the western part of Kanghwa Island. The area of sandy mud sediment extended to eastward tidal flat compared to sedimentary facies in August 1997. Sedimentary facies analysis of three core sediments from the tidal flat to the south of the Kangwha Island revealed three sedimentary facies: trough-cross-bedded sand, laminated silt, and bioturbated silt. Distribution of the facies in the cores suggested that sedimentation rates has been generally high in the margin of main tidal channel, especially in the east of the Donggeum Island. Twelve-and-half-hour anchoring survey was carried out for measurements of hydrodynamic parameters at Yeomha channel near Choji Bridge(K1) and channel near Donggeum Island(K2) in June 2003. Residual flows indicated strong ebb-dominated tidal currents. Depth-integrated net suspended sediment loads for one tidal cycle were seaward movement with 309,217.9kg/m and 128,123.1kg/m at station K1 and K2, respectively. The higher value of net suspended sediment loads at station K1 suggested that lots of suspended sediments from Han River deposited in the eastern part of tidal flat.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.531-545
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• 2013

This paper was considered on the applicability of EFDC KUNSAN_SEDTRAN MODEL (2012) to calculate Gunsan Port sediment deposition height efficiently and to use for grasping its aspects quantitatively and providing its prevention measures reasonably based on well-known 3-dimensional EFDC sediment transport module. This model was calibrated and verified with various measured field data of A Report of Hydrological Variation on Kum River Estuary (2004). Due to the model calibration and relevant literature investigation for cohesive sediment parameters, settling velocity (WS), critical deposition stress (TD), reference surface erosion rate (RSE), critical erosion stress (TE) were identified as 2.2E-04m/s, 0.20 $N/m^2$, 0.003 $g/s{\cdot}m^2$, 0.40 $N/m^2$ respectivly on this model. In order to examine the applicability and precision of the model computation, the calculated model data of sediment deposition height at 13 stations for 71 days and suspended-sediment concentration at 2 stations, inner port and outer port for 15 days were compared and analyzed with the measured field data. As a result, the model applicability for sediment deposition height simulation was evaluated as NSE coefficient 0.86 and the precision for suspended-sediment concentration computation was evaluated as time averaged relative error (RE) 23%.

• Korean Journal of Environment and Ecology
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• v.33 no.2
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• pp.228-236
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• 2019

This study investigated the effect of the sediment phosphorus fraction sampled from the southern coast of Korea on the release characteristics of sediments by environmental changes of water quality. We conducted the release experiment in the laboratory for 20 days and measured the phosphorus fraction properties, the environmental factors of water quality, and the release rate of total phosphorus. The results showed a decrease in dissolved oxygen by the growth of microorganisms in the water layer, leading to the anaerobic condition in which the redox potential of the sediments decreased. As such, the decreasing variability of phosphates bonded to iron oxide in the sediment phosphorus was higher after 20 days of the release experiment than the first day. It means that the metal ions and the separated inorganic phosphorus transfer into the water when the iron oxide is reduced. The separated inorganic phosphorus is easily absorbed by the plankton. The analysis of total phosphorus in the water layer showed that it continuously increased to up to 0.304 mg/L for 20 days, and the release rate had a high correlation with the decrease of dissolved oxygen after 5 days of culture. Therefore, it is necessary to pay attention to the characteristics of iron bonded to phosphorus in the phosphorus fraction and dissolved oxygen to manage the eutrophication of the system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.125-135
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• 2008

The purpose of this study is to quantify the erosion parameters of cohesive sediments in Keum Estuary. This study also involves the examinations on the local/seasonal variation of them in Keum Estuary and on their spatial variation comparing with those of other sites. As erosional properties of cohesive sediments are in general influenced largely by the physico-chemical properties of cohesive sediments themselves, this study also involves the qualitative analyses on the impact by the physico-chemical properties. Erosion tests have been performed under the uniform bed condition using the Chonbuk annular flume and total 16 tests have been carried out with various bed densities and bottom shear stresses. Experimental results show that the critical shear stress for erosion varies in the range of $0.19{\sim}0.41N/m^2$ and the coefficient of erosion rate varies in the range of $54.26{\sim}7.70mg/cm^2{\cdot}hr$, over the corresponding bulk-density range of $1.14{\sim}1.38g/cm^3$. While erosion parameters estimated for Keum estuary sediments are found to be remarkably different in quantity compared with those for cohesive sediments from other sites, their local/seasonal variabilities within Keum Estuary are found to be insignificant.