• Journal of the Korean earth science society
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• v.22 no.1
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• pp.30-39
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• 2001

To consider the distribution of the surface sediments and sedimentary processes in tidal flat after the construction of sea-walls in the semiclosed Muan Bay, the southwest coast of Korea, studies on the sediments and sedimentation rates along two transect lines from February 1999 to March 2000 were carried out. The surface sediments in the bay are classified into 5 facies on the basis of textural parameters. The gravelly sediments including the cobbles and pebbles deposited in the bay-mouth are relic sediments which are formed in nearshore and fluvial environments at the low stand of sea level. In addition, it is considered that the muddy sediments widely distributed on the tidal flat might be originated from suspended matter transported from several rivers and/or offshore. Although the sedimentation rates on the tidal flat vary with season, their estimation rates are -8.9 mm/yr on Line-GR and -48.9 mm/yr on Line-YH, respectively. The erosion-dominated processes in the tidal flat would be caused by strengthened ebb tides due to the decrease of tidal choking at Mokpogu and the migration of tidal currents at the bay-mouth. The hydrodynamical changes mentioned above are interpreted to be occurred after/before the construction of sea-dike/sea-walls in coastal zone of Mokpo.

• 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 Industry Convergence
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• v.23 no.5
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• pp.717-726
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• 2020

Social costs are increasing in Gangwon-do east coast due to coastal erosion. Long-term coastline change information is essential for analyzing this phenomenon. In this study, aerial photographs immediately after liberation are used for 1950's coastline extraction. The study area is from Sokcho Cheongho beach to Yangyang Seorak beach. The aerial photograph is geometrically corrected using DLT(Direct Linear Transformation) method to extract past coastline and compare it with present data. Coastal erosion and deposition areas are calculated in study area. Artificial structures such as harbors and breakwaters have caused changes in ocean currents and sediments from river estuaries. In most cases, the deposition occurred at the southern area of artificial structures and the erosion occurred on surrounding beaches. Coastline information extracted from past aerial photographs can be useful to provide information on long-term changes.

• 한국해양학회지
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• v.26 no.1
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• pp.24-37
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• 1991

Marine benthic diatoms and environmental factors were studied at 60 sites on the Mangyung-Dongjin tidal flat of the west coast of Korea. Sediment samples were taken quantitatively from the upper 5 mm layer to obtain a representative estimate of the epipelic and epipsammic cell concentration. Surface sediments taken simultaneously with the quantitative diatom samples were analysed for the grain size. Exposure duration of study sites were calculated by the tide data recorded at Kunsan Outer-Harbour. Coarse sediments dominated mainly on the offshore coastal and lower tidal flat, whereas fine sediments occurred on inner and higher tidal flat. Total 371 diatom taxa were collected and the genera represented by a great number were Navicula and Nizschia. The 16 abundant species occupying more than 1% of total cell number are of the following: Paralia sulcata, Navicula sp. 1, Navicula arenaria, Cymatosira belgica, Amplora holsatica, Amphora coffeaeformis, Achnanthes hauckiana, Rhaphoneis amphiceros, Thalassionema nitzschioides. Navicula sp. 2, Dimeregramma minor, Amphora sp. 1, Cyclotella atomus, C, striata, Nitzschia kuetzingiana, Stephanodiscus sp. 1. The distribution pattern of these dominant species are described in relation to the habitat condition. Most of these species showed high densities in fine sediments. However, they occurred even silty sand and sandy sediments in low abundance. The epipsammic forms belonging to the Araphidineae and Monoraphidineae were restricted on the lower tidal flat. The typical species found in coarse sediments were: Cocconeis sp. 1, Opephora martyi, Amphora sabyii, Dimeregramma minor var. nana, Fragilaria virescens var. oblongella, F. virescens, Cocconeis grata. The higher tidal flat consisting of fine sediments showed relatively higher cell numbers than the lower tidal flat. River mouth region was the highest in abundance.

• Journal of Environmental Science International
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• v.22 no.7
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• pp.787-799
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• 2013

The aim of this study was to investigate the accumulation of metallic elements and the control effect of marine pollution caused by ocean dumping in the sediments at a waste disposal area in the Yellow Sea. In July 2009, concentrations of organic matter and metallic elements (Al, Fe, As, Cd, Cr, Co, Hg, Ni, Mn, Pb, and Zn) were measured in surface sediments at the site. The ignition loss (IL) in the surface sediments showed a mean value of 15.4%, about 1.5 times higher than the mean value of the sediments in the coastal areas of Korea. The chemical oxygen demand (COD) at some disposal sites exceeded 20 mg $O_2/g{\cdot}dry$, which signifies the initial concentration of marine sediment pollutants in Japan. The disposal sites contain higher concentrations of Cr, Cu and Zn than the sediments of bays and estuaries that might be contaminated. The magnitude of both metal enrichment factors (EF) and adverse biological effects suggest that pollution with Cr and Ni occurred due to the dumping of waste in the study area. In addition, the geoaccumulation index (Igeo) showed that the surface sediments were moderately contaminated. By the mid-2000s, when the amount of waste dumped at this site was the highest, the concentration of metallic elements was higher than ever recorded. On the other hand, in 2008-09, the need for environmental management was relatively low compare with the peak. As a result, the quality of marine sediment has been enhanced, considering the effect of waste reduction and natural dilution in the disposal area.

• Journal of the Korean earth science society
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• v.37 no.4
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• pp.200-210
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• 2016

Geoacoustic modeling is used to predict sound transmission through submarine bottom layers of sedimentary strata and acoustic basement. This study reconstructed four geoacoustic models for sediments of 50 m thick at the Jeongdongjin area in the western continental margin of the East Sea. Bottom models were based on the data of the highresolution air-gun seismic and subbottom profiles (SBP) with sediment cores. P-wave speed was measured by the pulse transmission technique, and the resonance frequency of piezoelectric transducers was maintained at 1MHz. Measurements of 42 P-wave speeds and 41 attenuations were fulfilled in three core sediments. For actual modeling, the P-wave speeds of the models were compensated to in situ depth below the sea floor using the Hamilton method. These geoacoustic models of coastal bottom strata will be used for geoacoustic and underwater acoustic experiments reflecting vertical and lateral variability of geoacoustic properties in the Jeongdongjin area of the East Sea.

• Analytical Science and Technology
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• v.15 no.3
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• pp.287-299
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• 2002

The residue levels of total PCBs in the surface samples were detected low concentration compared to the coastal area in Korea, and the PCBs pattern were very similarly to the arochlor mixture(1016+1232+1248+1260). The selected area divided into three area(Kanghwa:A, Yellow:B and Jangdo:C) by depending on the chlorine ratio. The PCBs were mainly detected dichlorinated and trichlorinated biphenyls in far sea, and heptachlorinated and octachlorinated biphenyls in the near the Incheon coastal area. The residue levels of PCBs were detected 0.72${\sim}$9.20 ng/g in the surface samples, 1.60~3.00 ng/g for Kanghwa and 0.34~9.20 ng/g for Jangdo in the core samples, and the PCBs concentration increased from bottom to top.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.296-301
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• 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 association of regional geographers
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• v.12 no.6
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• pp.631-644
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• 2006

The study area is a pocket beach which consisted of sandy beach, dune, agricultural land and residential area etc. The coastal dune area is classified to foredune, dune plain, secondary (or back) dune. The foredune area is covered by herbaceous dune plants(ex. Carex kobomugi, Wedelia prostrata, etc.), whereas the dune plain area is covered by herbs and shrubs(Vitex rotundifolia). The most inner area, secondary dune, is planted by pine forest(Pinus thunbergii). The mean size of the beach and dune sediments ranges from 1.1 to $1.8{\Phi}$, which mean these values are higher than normal sediments. Sorting and Skewness is $0.6{\sim}-1.2{\Phi}$ and $-2.7{\sim}1.6{\Phi}$ respectively. We found that the soil formation process in the secondary dune area has been progressed rapidly from the analysis of fine grain content, organic matter content, and CEC.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.325-331
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• 2016

Three diatom assemblage zones were erected from HMB-103 core sediment of the Heuksan Mud Belt. The paleoenvironmental changes were reconstructed basing on diatom analyses using indicator species, cold and warm water species, and salinity. Seventy-six species belonging to 41 genera were identified in the core sediments. The number of diatom valves per gram of dry sediment ranged from 0.1 to $15.4{\times}10^4g^{-1}$. As a result, diatom assemblage I in about 45,000 yr B.P showed a high abundance in cold species indicating a major influence by the Korea Coastal Current. Diatom assemblage II from 14,000 to 11,646 yr B.P is characterized by rare abundance and indicative of the cold periods at Younger Dryas with the lower sea-level. However, diatom assemblage III from 11,646 yr B.P to Holocene was more affected by the Yellow Sea Warm Current while the progressive sea level rise.