• 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 Korea Water Resources Association
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• v.42 no.2
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• pp.141-148
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• 2009

Each river in each country has peculiar channel characteristics at every section. Korea consists of mountains at the rate of 70%. Due to this, the sections that display unique channel form are scattered. One of the typical features is the narrow pass of channel section that presents in the process of the generation of alluvial channel and deformation channel. Around as this narrow pass of channel, it often comes to be regular flood disaster section. Regardless of this situation, investigations and plans that reflect channel characteristics at the narrow pass of channel have been wholly wanting until now. In accordance with this, we have investigated and analysed hydraulic significance and channel form of the narrow pass of channel in Seonsan in this study. The study has found real minute classification of sediment phenomenon at river bed of low flow channel on investigation section which is sand-bed river, but it was vaguely difficult to conclude that classification of sediment arises from explicit natural force. We were able to assume that the phenomenon comes from gentle bed slope, supply of river bed materials which is nearly uniformity. However, classification of sediment would come from collecting an aggregate rather than natural force. And we found that compound cross section conversion has been developing dramatically with channel form of movable bed section referring to movement which was active before at drainage district of the narrow pass of channel. With this, we could find the phenomenon that river width of low flow channel diminished largely. This kind of situation implies that it may cause compound section weighting, flood dimension decreasing, revetment at low flow channel or the local scour at bottom of levee when extraordinary flood occurs.

• 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.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.2
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• pp.42-53
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• 2020

In this study, heavy metal in road-deposited sediments (RDS) and marine sediment around Gwangyang Bay area have been investigated to assess the pollution status of metals and to understand the environmental impact of RDS as a potential source of metal pollution. Zn concentration for <63 ㎛ size fraction was the highest (2,982 mg/kg), followed by Cr, Ni, Pb, Cu, As, Cd, and Hg. Metal concentrations in RDS increased with decreasing particle size and relatively higher concentrations were observed around the metal waste and recycling facilities. For particle size in RDS smaller than 125 ㎛, EF values indicated that Zn was very high enrichment and Cr, Cd, Pb were significant enrichment. The concentrations of metals in marine sediments were mostly below the TEL value of sediment quality guidelines of Korea. However, the Zn concentrations has increased by 30~40% compared to 2010 year. The amounts of Zn, Cd and Pb in less than 125 ㎛ fraction where heavy metals can be easily transported by stormwater runoff accounted for 54% of the total RDS. The study area was greatly affected by Zn pollution due to corrosion of Zn plating materials by traffic activity as well as artificial activities related to the container logistics at Gwangyang container terminal. The fine particles of RDS are not only easily resuspended by wind and vehicle movement, but are also transported to the surrounding environments by runoff. Therefore, further research is needed on the adverse effects on the environment and ecosystem.

• 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.

• Ocean and Polar Research
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• v.43 no.4
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• pp.307-320
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• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.

• Journal of Korean Society of Forest Science
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• v.81 no.3
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• pp.263-272
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• 1992

In a torrential river, the flow of debris forms deposits in the river bed, which show the characteristics of the channel bed movement in the watershed. The annual rings of the trees, in the natural evenaged forests on the deposits, indicate when each deposit occurred. Based on the topographical and vegetational indicators on the sediment of Yongcheon and Yeounae rivers, the movement occurrence years were estimated. 1. The cross sectional shapes of deposits in torrential river are in tiers and even-aged forests tend to establish on each tier. 2. Generally the older the forest age is, the higher the height of step from the lowest base tend to become, which indicates discrete movement in magnitude and frequency. 3. The ages of trees indicate the year when deposition occurred, and so may be useful as plant indicator to get spatial-temporal information of deposits. 4. The deposits volumes(F. V.) were dependent on the age distribution of deposits in length, average width and average height. And the average width and the average height of deposits were increasing with the age.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.44-52
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• 2007

Contaminated sediments more than 30 million/$m^3$ is generated from dredging work for harbours and coastal maintenance in Korea. Approximately 300 million/$m^3$ of sediments is dredged to deepen harbours and shipping lanes in US and of which $3{\sim}12million/m^3$ is highly contaminated. Although much is known about technologies for the remediation of heavy metal contaminated soil, much less is known about the treatment of contaminated sediment. In general, negatively charged fine particles will migrate towards positively charged system of electrodes under the influence of electrophoresis. However, the electrically induced migration of colloidal particles contaminated with heavy metals may be hindered by the positively charged heavy metal contaminants adsorbed onto the soil surfaces depending on the contamination level. This paper demonstrates settling behaviour of clayey soil by comparison with electrophoretic particle movement under the effects of heavy metal contamination, applied electric field strength, and its polarity changed by the electrode configuration.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.193-206
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• 2004

Geophysical data including chirp (3 7 kHz) subbottom profile and detailed bathymetry were obtained over three seamounts in the Ogasawara Fracture Zone (OFZ) of the western Pacific, as a part of manganese crust survey onboard R/V Onnuri in 2003. The OFZ is a 150-km-wide, 600-km-long rift zone, which separates the East Mariana and Pigafetta Basin. The OFZ is unique in that it includes many seamounts (e.g., Magellan Seamounts andseamounts on the Dutton Ridge). The sub-seafloor acoustic echoes obtained near the OFZ were classified into following types on the basis of their characteristics: types I-1(pelagic sediment with parallel or subparallel reflectors), I-2 (pelagic sediment with no internal reflectors), and III-1 (reef build-up complex) on summit; types II-1 and III-2 (basement outcrop) on flank rift zone and upper slope, respectively; type III-3 (slump) on the lower slope and embayment between the flank rift zones; types II-2 (debrite) on the base of slope and basin floor; and types II-3 (turbidite or pelagic sediment) and II-4 (turbidite) on the basin floor. The mass-wasting that produced the complex of type II-2 debrite and III-3 slump on the lower slope and basin may have been caused by (1) strong tensional stress in the OFZ which may cause the numerous fissures or basement faults and (2) complex of the faults on the summit and steep upper slope. The variations in the echo type of pelagic sediment in the summit of seamounts may be related with the changes in the depositional and/or erosional environments. Type I-2 pelagic sediment, which is characterized by a thin and intermittent coverage, was probably deposited at a sheltered area when the current was strong, whereas type I-1 pelagic deposit occurred during a stage of progressive sedimentation.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.116-119
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• 2009

HSPF is a comprehensive, continuous, lumped parameter, watershed-scale model that simulates the movement of water, sediment, and a wide range of water quality constituents on pervious and impervious surfaces, in soil profiles, and within streams and well-mixed reservoirs. The hydrologic calibration of HSPF is performed manually using the decision-support software Expert System for the Calibration of HSPF (HSPEXP). The initial values for the HSPF hydrologic parameters were estimated based on guidance from BASINS Technical Note 6. Initial parameter values were adjusted for the study watershed during the calibration period within the recommended ranges for the parameters.