• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.179-183
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• 2001

Shortnecked clam, Ruditapes philippinarum, is one of the very important shellfish produced in south-western coast of Korea. But it's ready to be polluted and have sand in flesh because it mainly inhabit in silt at the inside of coastal area. This study was carried out to obtain informations about the elimination of sand in shortnecked clam harvested from western coast of Korea. During rearing shortnecked clams in water tank, the elimination rates of sand from them at 6, 13, 23, $28^{\circ}C$ were 59.0, 88.2, 97.9, $96.1^{\circ}C$ after 48 hours, respectively. The sand was eliminated above $95^{\circ}C$ from the shellfish at 32,9 to $40\%_{\circ}$ of salinity after 48 hours. But the sand elimination from them was incomplete and inconsistent at 10 to 20 of salinity. The sand was eliminated rapidly at pH 1.9 to 9.0 however, its elimination was not effective at neutral or acidity range, It was found that the sand elimination was most effective at $23^{\circ}C, 35\%_{\circ}$ salinty and pH 9.0. Reasonable flow rate for sand eliminate in shortnecked clam was above 150 L/min./shellfish $m^3$ under both 3,000 and 4,000 L/shellfish $m^3$, and above 100 L/min,/shellfish $m^3$ under both 6,000 and 8,000 L/shellfish $m^3$ in water tank.

• Journal of the Korean Geographical Society
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• v.37 no.5
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• pp.511-521
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• 2002

Coastal sand dunes in West coast of Korea are under stress. Due to the newly constructed Seohaean(West Coast) Highways, the number of visitors and the anthropogenic pressures will keep rising in near future. Sea level rise due to the global warming may cause a lot of damage to the natural resources and residents of coastal area. Therefore, many countries including United States are doing nationwide coastline survey using highly sophisticated methodology. In this study, high resolution IKONOS satellite images along with aerial photographs taken since 1960's have been sequentially analyzed using GIS software (Erdas Imagine 8.3). Onsite monitoring has been performed at the 31 measuring points in 10 beaches since the May of 2001 in order to measure the sand budget. Post-construction monitoring after installation of sand fences is also being done on sites regularly. Restoration works seem to be effective at this moment.

• 한국해양학회지
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• v.20 no.1
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• pp.43-49
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• 1985

The Changgu Bay, a macrotidal coastal embayment of the west coast of Korea, is an area of extensive intertidal sedimentation. Three types of major sediment facies are identified based on grain size analysis: silt, sandy-silt, and silty-sand facies. It is found that intertidal sediment facies comprise a continuum of progressively finer sediments from lower flat to upper one. The X-radiography of the cores in the intertidal zone show a wide variety of physical and biogenic sedimentary structures. The major structures include bioturbation, current ripple and parallel-laminae. Bioturbations are observed in all core samples, especially in the silt flat zone. The degree of bioturbation increases laterally from sandy facies (low tide level) to silt facies (high tide level) due to favorable properties of fine mud for organisms. The ripple laminae, composed of current ripple foresets, characterize the silty-sand and sandy-silt flats. The parallel laminae are extensively bioturbated, and two types of laminae are distinguishable; thick-laminae with a thickness of 1 to 5mm and thin-laminae with a thickness of less than 1mm.

• The Korean Journal of Ecology
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• v.20 no.2
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• pp.133-143
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• 1997

From 1984 to 1989 reclaimed coastal lands in Choongnam Province of the western coast of Korea were studied for soil texture at three sites(Daeho, Hyundai A and Hyundai B) and for desalination one site(Hyundai B). The soil textures of varied sites in Hyundai A were horizontally similar and composed of 39-40% clay, 40-49% silt and 8-14% sand. But those in Da돼 and Hyundai B differed horizontally in the same area and vertically at the same site. Soil texures of Da돼 were composed of 15-17% clay, 30-45% silt and 40-55% sand and those of Hyundai B were composed of 22-45% clay, 26-49% silt and 17-31% sand. The measured electrical conductivity(EC), which represents whole salt content of the reclaimed soil, decreased year by year. The vertical distribution of the EC changed temporally and spatially in the upper zone above a 50 cm depth but not in The lower zone below a 50 cm depth. The EC valus of the soil were inversely proportional to the magnitued of annual precipitation, evaporation and the numbers of rainy days with r equalling -0.97. But the annual decrease of the EC was directly proportional to climatic factors with r=0.7. Salt in the reclaimed land was leached out by the percolative action of surplus rain water, or moved up by evaporation and carried away by running rain water. The running out of the salt on the soil surface was most efficiently carried out over 10 mm precipitation per day.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.184-189
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• 2001

Surf clam, Mactra veneriformis, is a important shellfish produced in south-western coast of Korea. But it's ready to be contaminated and have sand in flesh because it mainly inhabit in silt at tHe inside of coastal area. We determined optimum conditions for the sand elimination and microbial depuration in the shellfish harvested from western coast of Korea. It was found that the most effective conditions of process water for the sand elimination were $23^{\circ}C$, $32.9-35.0\%_{\circ}$ salinity and pH $7.9\~9.0.\;A$ surf clam contained about 210 mg of sand whose $94\%$ was eliminated after 24 hours in natural sea water ($32.9\%_{\circ}$ , pH 7.9) controlled at $23^{\circ}C$. To eliminate both sand and microorganisms contaminated in surf clam, the process water should be run during at least 36 hours for the former and 24 hours for the latter at 150 L/minute/$m^3$of shellfish, when its volume was above 4,000 L/$m^3$ of shellfish in 2 tons of tank.

• Ocean Systems Engineering
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• v.12 no.4
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• pp.403-411
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• 2022

Annually, about 48-60% of sediment discharge of the Mekong River is delivered near the mouths of the Mekong River branches which is mostly coinciding with the southwest (SW) monsoon. This sediment budget in turn will be southwestwardly transported along the coast of the Mekong Delta (MD) during the northeast (NE) monsoon. Analysis of monsoonal changes in grain-size distribution (GSD) of surface sediment contributes to a better understanding of erosion and deposition processes along the MD. This study aims to figure out changes in GSD and sediment textures along the MD between SW and NE monsoons based on 183 surficial sediment samples collected along the MD during two field surveys carried-out in October 2016 and February-March 2017. Compared to the GSD during the SW and NE monsoon, the GSD along the MD changed significantly, especially in the estuary areas and along the coast of Bac Lieu and Ganh Hao. Whereas, in the west coast of the MD, GSD seem no changes between the two seasons. These changes in seabed sediment suggest that sediment with grain-sizes ranging from silt to fine sand can be transported during only a NE season.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.493-500
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• 2013

Comparisons of surface sediment distributions in summer 1997 and 2011 and elevations on the tidal flats in April 1998 and March 2013 had been used for understanding the long-term changes of sedimentary environments at southern Kanghwa tidal flat, west coast of Korea. The mud sediments dominated in the eastern part and sandy mud sediments dominated in the western part of the tidal flat in 1997. In 2011, the surface sediments were dominant mud and sandy mud at Sunduri and Tonggum in the eastern part, sandy mud at Tongmakri in the middle part, and sand and muddy sand at Yeochari and Changhwari tidal flats in the western part. The area of mud sediments had decreased, but that of sand-mud mixed sediments extended to eastward tidal flat for 14 years. The long-term topographic changes showed that deposition occurred at Tongmakri and Yeochari and erosion occurred at Changhwari tidal flat during 15 years. These changes should be effected the local hydrodynamic changes by several constructions near the tidal flat since the 1990s.

• Journal of the Korean earth science society
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• v.33 no.1
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• pp.1-10
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• 2012

Analysis on high-resolution seismic and core data reveals that the sedimentary strata in Gyeonggi Bay consists of four sedimentary units (Unit I-IV, from top to bottom) formed during the late Quaternary period. Unit I is interpreted as sediments of tidal flat and channel-fill deposits, formed during the Holocene transgression. Unit II is divided into shallow-marine facies unit in offshore area and channelized fluvial to estuarine facies unit in nearshore sand ridge and tidal flat. Unit III is considered as tidal flat deposits with the uppermost severely weathered and oxydized layers. This unit is composed of shallow marine sedimentary successions formed during the MIS-5 highstand. The lowermost Unit IV rests on Mesozoic basement rocks, considered as the shallow marine and shelf deposits formed before the MIS-5 lowstand.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.87-94
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• 1999

Sand drain as a vertical drainage is widely used in soft ground improvement. Recently, sand, the principal source of sand drain, is running out. A laboratory model test was carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. D is the diameter of the column. The transient process of pore water pressure with loading and the characteristics of consolidation were studied with the data gained from the measuring instrument place on the surface of the container. The parameter study was performed for the marine clayey soil before and after the test in order to check the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. According to the test, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. As a result, it is assumed that gravel is relatively acceptable as a drainage material.

• Economic and Environmental Geology
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• v.11 no.2
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• pp.81-88
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• 1978

Nearly 300 bottom sediments and 20 box-cores were sampled from the Asan bay. The central portion of the Asan bay is covered by sand, slightly gravelly sand and gravelly muddy sand. Between the central and marginal zones gravelly mud and slightly gravelly sandy mud are characteristically distributed. The gravel population in the sediments seems to be originated from the rocky bottom on the area near the bay because the gravel is angular and composed of the schist and gneiss. The quartz/feldspar ratio is about 3/2. It is considered to be that the amount of feldspar in this bay is much higher than that of any other areas in the Yellow Sea. This is considerd to be comparatively short distance of transport ion of these sediment from the provenance.