• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.49-60
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• 2015

Open-water sediment disposal has many applications in costal construction. Dumping of sediment in open water can be divided into descending stage under water and sedimentation stage on the seabed, and retained rate is evaluated from analyzed results of these two successive stages. Descending particle cloud have two distinct thermal and swam phase, and trajectory equations for each phase are derived to describe settling velocity and radius of particle cloud. For sedimentation stage, a numerical simulator is used to calculate growth factors for particle fiction angle and current velocity. Retained rate is defined as a mass rate of remained sediment inside the circle which has a center at dumping point on the sea level and user-defined effective radius. Retained rate map for Singapore coast is presented with water depth of 20 m, current velocity of 0.0~1.5 m/s, and effective radius of 5 m. It will decrease sediment mass loss during disposal operation and minimize surrounding environmental pollution.

• Korean Journal of Microbiology
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• v.38 no.2
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• pp.119-126
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• 2002

ATP concentrations far estimating total microbial biomass in the sediment were measured in three different marine sedimentary environments. ATP concentrations were highest in the surface sediment and decreased with increasing sediment depth and distance from the land. The results indicated that the benthic microbial biomass is primarily controlled by nutrient inputs from the overlying water column. Because of the longer residence time and adsorption to the sediment, the variations in organic carbon (OC) contents with sites and depths were not as distinct as that of ATP, and the correlation between OC and ATP was not significant in the coastal sediments. No significant correlation between OC and ATP in the coastal sediments also suggested that microbial biomass in the labile organic-enriched coastal sediment is suppressed by the grazing of higher trophic level such as meiofauna. Overall regional and vertical distribution of ATP indicated that h\`w can be a relevant tool for measuring total microbial biomass in various marine sedimentary environments.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.57-61
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• 2004

According to the research result of existing regarding the seabed organic sediment, contamination it flows from the land and the sea become the enemy in the coastal water. It was caused with the summer season water temperature rise and dispersing recall respect advancement. Phosphorus which is a main reason of red tide actual condition came to reveal vast quantity with the facts that it gushes. Specially, in the case of the coastal closing waters and the nursery, as the corpse and the fresh fish washing veterinarian was imbrued, it is the actual condition where is more deepened. Consequently the development of shallow layer dredging method of that suction power which is stabilized is demanded to be able to dredge only the sediment layer which has not become the pressure and is a main reason of being imbrued. The dredging methods using the pressure difference minimize the suction of the seabed sediment. This method is stable that suction power which occurs from guard difference of the guard and the guard of the dredging system inland water. That's why it is possible to sort dredging of the organic sediment ranging in upper layer sediment and it will be able to expect the minimization of dredging quantity. Increase of the expense that it followsin orthocenter with the fact will not grow. Because the pressure difference of the dredger inland water is occurred by the suction power. Maintenance administrative costs are reduced, because the one of smallest dredging system maneuvers and the barge which affixes an integrated operation system is mainly in a resting. To reduce a dredging hour, it will be able to solve in the condensed water as operating the jar guard post.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.542-550
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• 2011

Changes of suspended sediment concentration in the Seomjin river estuary located in south sea of the Korea peninsula were investigated during the spring tide in autumn (i.e. 25 hours in October) 2000 and winter (i.e. 25 hours in February) 2001. The changes of temperature and salinity during the spring tide in October 2000 showed larger variations than the those in February 2001. During the spring tide in October 2000, currents at bottom layer were observed to be stronger than during the spring tide in February 2001, showing that both of the two periods had ebb currents-predominant tide asymmetries. The suspended sediment concentrations in October 2000 were larger than the those in February 2001. At the time of the maximum of tide currents or after about one hour of the maximum during the autumn months, the suspended sediment turbidity was observed to be maximum. Another observation station at Hadong upstream from the Seomjin river estuary showed about one hour delay in tide phase, Thereby, the suspended sediment concentration showed high turbidity after two hours at bottom and three hours at surface layer, in particular, in October 2000. This results can be explained by the facts that river discharge increased significantly after the summer rainy season, causing also increase of erosion processes by strong current velocity at bottom layer.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.531-541
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• 1997

Unconsolidated sediments of Youngjong Island were investigated to consider the vertical distribution of clay minerals and their origin. At least three sedimentation units can be recognized by color, magnetic susceptibility, and pH. X-ray diffraction analysis of clay size fraction reveals that illite is the most abundant phase (52.06%), and chlorite (27.16%), kaolinite (16.92%), smectite (3.86%) occur next to it. Detailed XRD study suggests that illitic materials contain fairly large amount of ordinary muscovite derived from the mica schist in Youngjong Island and adjacent area. The relative amount of kaolinite and chlorite is less than those of samples from estuary mouth of several rivers that flow to Yellow Sea and South Sea. Especially smectite content of the present sample is much higher than those of estuary sediments. These indicate that the unconsolidated sediments of tidal-flat deposit in Youngjong Island are largely affected by marine influence and partly affected by sediment in influx from China. However, some degree of source of this unconsolidated sediments is inland origin from adjacent estuary sediment and in situ or nearby weathered materials.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.15 no.1
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• pp.35-42
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• 1979

This paper concerns the receding of the eastern coastline of Korean peninsula at a macroscopic point of view, the result is as following. 1. Eastern coast is gradually developed from maturity stage to full maturity stage. 2. The coastline recession due to sea level rise is amounted to the receding distance, x=0.045 m per yr. 3. The author proposes another classification from the new view point, which is classified by comparing quantities between river supplying sediment loads, and the littoral drifting due to wave actions. According this, eastern coast is receding(Type Q-A), and we could find it's geomorphological characteristics. 4. The general piofile of eastern coast sand beach is erosional storm profile(Type I) which accompany offshore bar. 5. From the wave measuring data of eastern coast(Hoopo port), I can derive the linear regression line of the exceedance probability of wave height from the log-normal distribution. $z=O. 113+4.335 log_lo H, r=0.983.$ Above equation made it possible to estimate $\omega[=P(H>H_c)]for the effective wave height H_c=2. Om4, 4. Om and their corresponding values are considerable (7.8%, 0.3%) 6. Eastern coastline certainly have the tendency of erosive and receding, owing to the sea level rise, poor sediment source and effective wave actions. It's very desirable to survey coastline evolution for a long time systematically, in order to make more elaborate diagnosis.

• 한국해양학회지
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• v.26 no.1
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• pp.38-46
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• 1991

size data of 1,044 surface sediments from Korean shelf area were compiled and reexamined. Size distribution curves of the sediments are unimodal (31% of the total number), bimodal (54%), or multimodal 915%), Size curves of the sediments and modal subpopulations of the mixed sediments show resemblance to normal curve in shape. The modal mean value shows systematic change along a direction inside the Recent mud belts of the southeastern Yellow Sea and west of Korea Strait. It was found that the areas covered by unimodal sand are minimal value areas of heavy metal and suspended sediment-concentration in the southeastern Yellow Sea and northern East China transport processes during Recent time. It was also found that the mode analysis is useful method to extract information from sediment size data.

• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.75-80
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• 2007

Measuring the ground speed and the rotation speeds of tracks is an easy and realistic method to detect the track slips. It is very advantageous if the slips can be measured and applied to real time control of the vehicle. With a proper speed, the tractive force of a tracked vehicle may be calculated from the vehicle dynamics. For the control of tracked vehicle, the relationship between the slip and the tractive force is necessary. In this paper, a series of drawbar-pull tests, in which slips of two tracks are measured under the variational draw-bar weight, is executed to directly obtain the slip-tractive force relationship. For the purpose of the test, a tractive vehicle model was manufactured, and an artificial soil was simulated by using a bentonite-water mixture.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.85-85
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• 2022

The world's most extensive and active deltas, Louisiana's wetlands, are deteriorating rapidly due to multiple stressors such as the discharge of the Mississippi River, sea-level rise, and coastal retreat, the substantial but spatially and temporally variable impacts. However, the ecological and anthropogenic histories, the mode of environmental changes on a multi-millennial timescale have not been thoroughly documented. This study, a palynology-based multiproxy analysis, investigates hydrological, geological, geochemical, and anthropogenic impacts on southern Louisiana wetlands and a variety of external forcing agents influencing ecological succession. Sediment cores extracted from a small pond on a mangrove-dominate island near Port Fourchon, Louisiana, USA yielded a 4,000-year record. The site has been transformed from freshwater to saline water environments, to a mangrove dominant island over the late Holocene. The multivariate principal component analysis identified the relative strength of external drivers responsible for each ecological shift. The Mississippi River delta cycle (lobe switching) was the dominant driver of ecosystem changes during the late Holocene, while relative sea-level rise, tropical cyclones, climate, and anthropogenic effects have been the main drivers late in the site's history.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.1
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• pp.30-39
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• 2004

In order to understand the environmental impact of marine cage fish farms, we measured the vertical fluxes of particulate to the sediment, the distribution of organic carbon in core samples, sediment oxygen consumption rate (SOD), and macrobenthos with increasing distance from a fish cage in Miruk island located in Tongyong. The experiment was performed in August 2003. Measured values gradually decreased with distance, indicating that the organic matter in the sediment derived from the fish farm. The dominant macrobenthos species were Tharyx mulifilis, Lumbrineris longifolia, Sigambra tentaculata, and Capitella capitata, occupying 88% of the total population. Capirella capirata, an opportunistic polychaete species, were especially abundant between 0 to 5 m radius range. The estimated impact regions of organic matter enrichment based on sediment consilmption rates and compositions of macrobenthos were in good agreement. Most organic matter derived from the fish farm was deposited within a 10 m radius and then dispersed horizontally to nearby (at least 50 m) surface sediment. The vertical organic carbon fluxes to the sediment at the fish farm were higher by a factor of two than those outside the area. The remineralization organic carbon in the upper sediment layer was estimated to be 50% (1.07 g C m$^{-2}$ day$^{-1}$ ) at the fish farm. In contrast, outside the area, 30% (0.30 g C m$^{-2}$ day$^{-1}$ ) of organic carbon was recycled and the remaining 70% was deposited to the deep sediment layer.