• 한국해양학회지
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• v.26 no.4
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• pp.332-339
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• 1991

The sedimentation pattern in Namhaepo Bay, a macrotidal coastal embayment of western Korea, was investigated by means of analysing high-resolution seismic profiles, sediment samples, and tidal currents. Recent sediments up to 20 m which overlie the irregular surface of the acoustic basement. The sediments consist mainly of sandy silt and silt; the mean grain size of these sediments ranges from 4 to 5.5 phi, showing a shoreward-fining distribution pattern. This distribution pattern agrees are largely reversed during ebb, with a maximum velocity of 39 cm/sec. The calculated shear velocity of the tidal currents at sea bed ranges from 0.5 to 3.3 cm/sec during flood and from 0.7 to 2.5 cm/sec during ebb. The mean values of these velocities exceed the critical shear velocity for the silt particles. The data suggest that the tidal currents play an important role in the transportation and deposition of sediments in the bay and the surface topography of the sea floor is largely deter-mined by tidal sedimentation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.594-604
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• 2021

To evaluate the causes of beach erosion in Sinji-Myeongsasimni Beach, external forces, such as tides, tidal currents, and waves, were observed seasonally from March 2019 to March 2020, and the surface sediments were analyzed for this period. In addition, the shoreline positions and beach elevations were regularly surveyed with a VRS GPS and fixed-wing drone. From these field data, the speed of the tidal currents was noted to be insufficient, but the waves were observed to af ect the deformation of the beach. As the beach is open to the southern direction, waves of heights over 1 m were received in the S-SE direction during the spring, summer, and fall seasons. Large waves with heights over 2 m were observed during typhoons in summer and fall. Because of the absence of typhoons for the previous two years from July 2018, the beach area over datum level (DL) as of July 2018 was greater by 30,138m² compared with that of March 2019, and the beach area as of March 2020 decreased by 61,210m² compared with that of March 2019 because of four typhoon attacks after July 2018. The beach volume as of March 2019 decreased by 5.4% compared with that of July 2018 owing to two typhoons, and the beach volume as of September 2019 decreased by 7.3% because of two typhoons during the observation year. However, the volume recovered slightly by about 3% during fall and winter, when there were no high waves. According to the sediment transport vectors by GSTA, the sediments were weakly influxed from small streams located at the center of the beach; the movement vectors were not noticeable at the west beach site, but the westward sediment transport under the water and seaward vectors from the foreshore beach were prominently observed at the east beach site. These patterns of westward sediment vectors could be explained by the angle between the annual mean incident wave direction and beach opening direction. This angle was inclined 24° counterclockwise with the west-east direction. Therefore, the westward wave-induced currents developed strongly during the large-wave seasons. Hence, the sand content is high in the west-side beach but the east-side beach has been eroded seriously, where the pebbles are exposed and sand dune has decreased because of the lack of sand sources except for the soiled dunes. Therefore, it is proposed that efforts for creating new sediment sources, such as beach nourishment and reducing wave heights via submerged breakwaters, be undertaken for the eastside of the beach.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.67-82
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• 2003

A 2-dimensional hydrodynamic model has been applied to understand water circulation pattern in Lake Deacheong. The simulation results have been used in sediment transport modeling. A sediment transport model using a particle tracking method has been developed to simulate sediment transport in the ocean, river and reservoir. The model was applied to estimate transport track of particulate pollutants in the lake. The hydrodynamic model was verified for water level variations and showed good agreements. Through the results we found out that water velocity is less than 5 cnysec for mean yearly flow and more than 120 cnysec at some points for the simulated flood flow. The incoming sediment particles in flood season reached into the Daecheong Dam. But the incoming sediment particles in the mean flow were settled down at riverbed and didn't move into the dam. These results can be used in setting up water quality management plan in the lake.

• Economic and Environmental Geology
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• v.39 no.1 s.176
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• pp.83-93
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• 2006

The Kita-Yamato Trough is characterized by a SW-NE trending narrow graben between the Yamato Bank and the Kita-Yamato Bank in the central East Sea/Japan Sea (ES/JS). Core 20EEZ-1 was obtained in the flat summit of a small ridge from the southwest Kita-Yamato Trough. The sedimentation was mainly controlled by the supply of hemipelgic sediments and substantial tephras from explosive volcanic eruptions of the Quaternary volcanoes. The aim of this study is to reconstruct the tephrostratigraphy from the marine sediments collected from the Kita-Yamato Trough and to provide the atmosphere and ocean conditions during the explosive volcanic eruptions. According to the detailed tephrostratigraphy and lithofacies records, the core sediments were deposited during the last marine isotope stage (MIS) 7. The core consists of four lithofacies, idetified as, oxidized mud (OM), crudely laminated mud (CLM) and bioturbated mud (BM), interbedded with coarse-grained tephra (TP). The major element geochemistry and stratigraphic positions of seven tephra layers suggest that they originated from the Aira caldera in Kyushu area among the Japanese islands (AT tephra; 29.24 ka), unknown submarine volcano in the south Korea Plateau (SKP-I; MIS 3, SKP-II; MIS 4, SKP-IV; boundary between MIS 6 and MIS 5e, SKP-V; MIS 6, respectively), and the Baegdusan volcano in the Korean Peninsula (B-KY1; ca. 130 ka, B-KY2; ca. 196 ka). The absence of tephras originated trom Ulleung Island in core 20EEZ-l suggest that the tephras had not been transported into the Kita-Yamato Trough by atmosphere conditions during the eruptions. On the other hand, the B-KYI and the B-KY2 tephras derived from the Baegdusan volcano were founded in the Kita-Yamato Trough by a presence of prevailing westerly winds during the eruptions. Furthermore, the SKP tephras were characterized by the transport across the air-water interface, causing quickly thrust of raising eruption plumes from subaqueous explosive eruptions. Surface currents may play an important role in controlling the distribution patterns of the SKP tephras to distal areas. The tephrostratigraphic study in the Kita-Yamato Trough provides the important chronostratigraphic marker horizons and the detailed atmosphere and ocean conditions during the explosive eruptions.

• 한국해양학회지
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• v.25 no.4
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• pp.182-188
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• 1990

The sedimentation processes and heavy metal distributions at the Nakdong estuary were investigated during October 1987 and September 1988. The depositional sedimentary environment of the studied area was estuarine environments and was divided into three provinces depending on its textural parameters such as barrier, tidal falt, and water passes. The relationship between the textural parameters showed that the barrier was under strong wave action, that the tidal flat was under relatively weak wind-driven currents, and that the water passes were under strong and continuous tidal currents. Each environments was resulted from different transport mechanism. the sand barrier sediments were transported by all three populations including suspension, saltation, and bed load, and water pass-deposited sediments were by the bad load with some suspension population. In water mass over the studied area, the concentrations of heavy metals including Cu, Cd, $Cr^{+6}$, Pb and Zn were recorded to be 27.8, 6.7, 20.4, 16.3, and 37.3 ppb in their highest concentrations, respectively. and those in sediments were 20.0, 1.65, 25.4, 15.4, and 132.0 ppm, respectively. The total up take factored of Cu, Cd, $Cr^{+6}$, Pb, and Zn by V. Muller (corbicula fluminea) were 1600, 310, 310, 490 and 7900, respectively.

• Journal of the Korean earth science society
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• v.23 no.7
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• pp.565-574
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• 2002

Based on previous investigations of aerial photographs and topographical surveys, this study focuses on the sedimentologic features of the Daebudo area including sedimentation processes, sedimentary facies and hydrologic conditions of the erosional coast. A total of 137 surface sediments and one core (by hand auger) sediment were obtained to interpret the depositional environment of the erosional coast in the macro-tidal coast. Surface sediments are distributed from sandy gravel (sG) to silt (Z). Textural parameters are characterized not only by coarse, poorly sorted, positive skewed and multi-modal distribution in the supra-tidal flat, but also finer, relatively well-sorted, symmetric distribution in the intertidal flat. According to the C/M diagram, sediment transport modes of study area are characterized by the mixed mode of suspension and bedload in the upper-, middle-tidal flat and by uniform suspension in the lower-tidal flat due to tidal effect. Vertical sediment distribution of the core, collected near shoreline, shows coarsening-upward, poorly sorted pattern by the input of detritus resulting from coastal erosion. Considering the sedimentological features of the study area, it appears to be composed of a coastal zone changed by not only artificial reclamation, but also by natural processes such as strong wave action due to typhoons and storms during high water level and long/short-term sea level rising. As a result, tide-dominated erosional coasts show that the shore is affected by local, temporal and hydrological conditions near high tide level and that the intertidal flat is represented by a general tide-dominated sedimentary environment.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.1-13
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• 2013

Padori beach is one of the representative composite mixed beach in Korea and shows divert geomorphic landscape change. It belongs to the Taean National Park. The purpose of this study is to clarify movement mechanism of sediments from sediment distribution of Padori beach associated with morphology. In addition, it is to explain morphological landscape change under different wave and tide condition in the composite mixed beach consisting of a dissipative low tide terrace and a reflective beach face with a high tide range of 5 to 7m. The results of this study are: First, the mean grain size of sediments becomes smaller from the south of the beach, where there is a wide wave-cut platform, to the north because gravels are supplied from the wave-cut platform as well as sea-cliff in the south of the beach. A sedimentation pattern of the sandy gravel on the beach face and gravel on the berm, and gradation phenomena of grain size on cross-shore and alongshore direction in the beach can be explained with a pattern of sediment movement, overpassing, in the composite mixed beach. Second, micro-topography on beach face and berm were changed depending on effects of wave height and tide. As a result, in low-wave energy environments, a berm is developed in large size, and beach cusps are formed on the upper beach face, while in high-wave energy environments, a berm is built up in relatively small size, and mixture of sediments occur on the upper beach face.

• Journal of Wetlands Research
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• v.23 no.2
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• pp.107-115
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• 2021

In order to analyze wave propagation, tidal current, and sediment transport in the vicinity of the Gaeya open channel, it was classified into before(CASE1W) and after(CASE2W) installation of various artificial structures, and the calculation results for CASE1W and CASE2W were compared. For wave propagation, the results of incident and reflected waves were derived using the SWAN numerical model, and the tidal current velocity results were derived using the FLOW2DH numerical model for tidal current. The results of the SWAN numerical model and the FLOW2DH numerical model became the input conditions for the SEDTRAN numerical model that predicts sediment transport, and the maximum bed shear stress and suspended sediment concentration distribution near the Gaeya open channel were calculated through the SEDTRAN numerical model. As a result of the calculation of the SWAN numerical model, the wave height of CASE2W was increased by 40~50 % compared to CASE1W because the incident wave was diffracted and superimposed and the reflected wave was generated by about 7 km long northen jetty. As a result of the calculation of the FLOW2DH numerical model, According to the northen breakwater, the northen jetty and Geumrando, CASE2W was calculated 10~30 % faster than CASE1W in the tidal current of the Gaeya open channel. As a result of the calculation of the SEDTRAN numerical model, the section where the maximum bed shear stress is 1.0 N/m² or more and the suspended concentration is 80mg/L or more was widely distributed in the Gaeya open channel from the marine environment by the complex wave field(incident wave, reflected wave and tidal wave) and the installation of various artificial structures. it is believed that a sedimentation phenomenon occurred in the Gaeya open channel.

• The Korean Journal of Petroleum Geology
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• v.7 no.1_2 s.8
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• pp.28-34
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• 1999

The Cretaceous Poongam sedimentary Basin in Kangwon-do, Korea consists alluvial deposits of conglomerates, sandstones, mudstones or siltstones, and volcaniclastics. The Poongam Basin was formed as a fault margin sag or a transpressional basin developed along a strike-slip fault zone, and received huge amount of clastic sediments from the adjacent fault-scaip. It formed an aggrading alluvial fan system and a volcaniclast-supplied marginal lake environment, while tectonic activity and volcanism attenuated toward the end of basin formation. Following the Folk's classification, the sandstones of the Poongam Basin are identified as lithic wackes or feldspathic wackes. The areal and sequential variation of the mineral composition in the sandstones is not distinct. The results of K-Ar age dating from the intruding andesites, volcaniclastics and volcanic fragments in sedimentary rocks show a range of 70 Ma to 84 Ma. It suggests that volcarism occurred sequentially within a relatively short period as the pre-, syn-, and post-depositional events. It was the short period in the late Cretaceous that the basin had evolved i.e., the basin formation, the sediment input and fill, and the , intrusion and extrusion of volcanic rocks occurred. The Poongam sedimentary sequence is a typical tectonic-controlled coarse sedimentary facies which is texturally immature.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.3
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• pp.88-102
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• 2017

Long-term changes in bathymetry and grain size of surface sediments were investigated for understanding depositional sedimentary environments in the channelized Yeongsan River Estuary, Korea. The results revealed that an average depth of the estuary had decreased up to 2.1 m from 1982 to 2006, while it had increased to 0.3 m from 2006 to 2012. The rapid decrease of the water depth from 1982 to 2006 was due to the vast deposition of mud caused by the change of water course and flow velocity after the estuary was dammed. Meanwhile the increase of the water depth from 2006 to 2012 may be associated with multiple erosional processes, including a dredging at the southern part of the estuary and other erosions from the dike sluice expansion work. Considering the water-depth change and tidal-level variation in the study area, an depositional rate in the estuary is estimated to be 8~9 cm/yr for the last 2 decades (1982~2006). The sediments of Yeongsan River Estuary are largely composed of silt-clay mixtures: overall, silt is distributed mainly in the shallow area of the estuary edge, while clay is confined to the deep area of the estuary center. Mean grain size of the sediments is 6.0 Ø on average in 1997, 7.8 Ø on average in 2005 and 7.7 Ø on average in 2012, respectively, suggesting that the sediments became finer due to the increase of silt and clay contents in 1997~2005. Furthermore, several lines of evidences, including the comparison between the amounts of the sediment influx discharged from the Yeongsan River and the sediments in the estuary, and the changes in distribution pattern of silt and clay contents implying that they moved from offshore to estuary dike, indicate that the mud sediments are originated mainly from the offshore, not from the river.