• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.255-265
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• 2013

In the coastal region of Korea, historical tide harmonic constants were collected. Long-term tides and short-term tides observed by the KHOA were analyzed by a tide harmonic analysis method. Based on the harmonic constants, tidal characteristics such as tide asymmetry in Korean coastal waters were investigated. The harmonic constants obtained from the long-term tide data in the western coast have been used to show the relation between tide variation and reclamation project. $M_2$ amplitudes in the western coast have been decreased and $M_2$ phases were faster. $M_4$ amplitudes also were reduced and $M_4$ phases were faster in overall. In Mokpo and Kunsan tidal nonlinearity is relatively conspicuous. Overall, non-linearity of tidal currents is higher in the tidal channels flowing fast. The tidal non-linearity has increased by the development projects including large reclamation. The flood dominant characteristic in the northern and central part of Korean western coastal waters and the ebb dominant characteristic in the southern part have been intensified. The construction of Saemangeum sea dike has significantly changed the tidal characteristic in Korean western coastal waters.

• Journal of Environmental Science International
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• v.8 no.1
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• pp.83-94
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• 1999

A Study on the choice of proper region for moving cage culture facilities were carried out in the South Sea of Korea. Optimum temperatures of habitats for cage culture fishes, Sebastes schlegeli, Paralichthys olivaceus, Seriola quinqueradiata, Lateolabrax japonicus, Pagrus major, Takifugu vermicularis, and Mugil cephalus were 18~26$^{\circ}C$, 10~$25^{\circ}C$, 15~29$^{\circ}C$, 15~29$^{\circ}C$, 15~3$0^{\circ}C$, 15~$25^{\circ}C$, and 19~27$^{\circ}C$, respectively. In winter, wintering regions for continuous growth of fishes were proper around Komundo, Sorido, Soimal, Gadukdo and Chejudo for Paralichthys olivaceus and Lateolabrax japonicus, while Seoguipo and Udo for Seriola quinqueradiata, Pagrus major and Takifugu vermicularis. Sanji was not proper for wintering region because variation of water temperature is large by effect of strong northwestern wind. Wintering regions of Sebastes schlegeli and Mugil cephalus were not in the south of Korea. In summer, proper regions for fishes to avoid from damage by red tide were Komundo and around Chejudo. No red tide has occurred in these regions for 6 years. Mokpo and Yoja Bay were not proper for moving region because the former had strong tides and the latter had only one exit out of the bay which made it impossible to move cages in other route when dangerous red tides burst into.

• Ocean Systems Engineering
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• v.6 no.1
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• pp.61-97
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• 2016

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.827-833
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• 2019

There are several factors to consider for a ship to enter or depart a port safely. It is particularly important to identify the tides in the port to reduce the risk of stranding the ship. Most previous studies have focused on finding and analyzing harmonic constants. However, the research on the analysis and accuracy of harmonic constants in other hydrographic agencies is lacking. In this study, six Korean ports (Incheon, Gunsan, Yeosu, Busan, Ulsan, and Sokcho) were compared to the British and Korean tide tables based on actual information. To find the cause of tidal difference, the tide height, tide time, and form factor were calculated using harmonic constants. The information was then compared with British and Korean data. As a result of the difference in analysis of actual information and tide tables, there was a difference between the actual tide height and time at each port. The cause was found to be the difference in the harmonic constant, tide, and form factor between the UK and Korea. Therefore, this study, the Korean standard port should be added to the British tide table, and harmonic constants, which are the criteria for creating tides, must be constantly updated with the latest information. Additionally, the tide tables produced in each country are more accurate than the tide tables produced in UK.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.79-89
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• 2005

Groundwater level changes in coastal aquifers occur due to oceanic tides, where the properties of oceanic tides can be applied to estimate hyadraulic parameters. Hydraulic parameters of coastal aquifers located in eastern part of Jeju island were estimated using the tidal response technique. Groundwater level data from a saltwater intrusion monitoring well system was used which showed tidal effects from 3 to 5 km. The hydraulic gradient was assessed by utilizing the filtering method from 71 consecutive hourly water-level observations. Calculated hydraulic diffusivity ranged from 2.94${\times}10^7m^2d^{-1}$ to 4.36${\times}10^7m^2d^{-1}$ . The hydraulic gradient of the coastal aquifer area was found to be ~$10^{-4}$, whereas the gradient of the area between wells Handong-1 and 2 was found to be ~$10^{-6}$, which is very low comparatively. Analysis of groundwater monitoring data showed that groundwater levels are periodically higher near coastal areas compared to that of inner land areas due to oceanic tide influences. When assessing groundwater flow direction in coastal aquifers it is important to consider tidal fluctuation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.262-272
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• 2007

Diurnal and tidal variation in the abundance of the macro- and megabenthic assemblages were studied in the macrotidal flat, Incheon, Korea. The samples were collected by modified otter trawl during 8-9, June 2000. The macro- and megabenthic assemblages comprised a total of 60 species, including 6,309 individuals and 67,835.5 gWWt. As a result, the abundance pattern showed two different categories relating to diel and tidal cycles. First, the diel pattern of these assemblages was subdivided into 3 groups. 1) Diurnal species such as Hexagrammos otakii, Thryssa baelama, Loligo beka, Metapenaeus joyneri. 2) Nocturnal species such as Cynoglossus joyneri, Sebastes schlegeli, Charybdis japonica, Crangon affinis, Trachysalambria curvirostris, Metapenaeopsis dalei. 3)Other species showing no obvious pattern with Johnius grypotus, Platycephalus indicus, Repomucenus richardsonii. However, based on the result of Mann-Whitney U-test, diel patterns of macro- and megabenthos did not reveal any significant differences. Second, tidal variation in the macro- and megabenthic assemblages was significant between ebb and flood tides. Total macro- and megafaunal species number, abundance and biomass were higher in ebb tide$(13^h30',\;16^h30',\;1^h30',\;4^h30')$ than in flood tide$(19^h30',\;21^h30',\;10^h30',\;13^h00')$. As a consequence, the macro- and megabenthic assemblages were clearly influenced by tides but their diel variations were not significantly different.

• Journal of the korean society of oceanography
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• v.34 no.1
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• pp.22-35
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• 1999

The response of the tidal waves to friction effect is investigated in terms of deformation of Kelvin and Poincare modes, The 1st Poincare mode does not exist over the low frequency region less than the critical frequency of omega ${\omega}$${\sqrt{2f}}$, with ${\gamma}$/f=0.0, but the mode comes to exist in the presence of friction. When friction exists and its magnitude increases, the wave number increases, indicating that the wave length of the Poincare mode becomes increasingly short with increasing friction. The damping coefficient gradually increases with increasing friction over the high frequency region, but the trend is reversed over the low frequency region. In case of Kelvin wave the present study substantiates the characters of Kelvin wave examined by Mofjeld (1980) and Lee (1988). Based on the examination of frictional effects on the tidal wave propagation, the co-oscillating tides in the Yellow Sea are examined by considering both the head opening and bottom friction effects. As friction is introduced and increased in addition to partial opening at bay head, the location of the amphidromic point near the Shantung Peninsula moves more southwestward. This southwestward movement of the amphidromic point is increasingly compatible with the observed location of Ogura's or Nishida's tidal chart of the M$_2$ tide.

• Ocean Science Journal
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• v.43 no.4
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• pp.223-232
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• 2008

In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.2
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• pp.53-65
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• 2008

This paper proposes the qualitative method for planning the operation of multi-AUVs with environmental disturbances, which is considered to be a very difficult task. In this paper we use an extension collision map as a collision free motion planner. The tool was originally developed for the multiple ground vehicles with no internal/external disturbance. In order to apply the method to a water environment where there are tides and waves, and currents, we analyze the path deviation error of AUVs caused by external disturbances. And we calculate safety margin for the collision avoidance on the extension collision map. Finally, the simulation result proves that the suggested method in this paper make multi-AUVs navigate to the goal point effectively with no collision among them.

• 한국해양학회지
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• v.18 no.2
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• pp.142-148
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• 1983

In order to understand the circulation dynamics of the Keum River estuary, an extensive study was conducted; (i) variability of salinity boundary layer (ii) fluid dynamic characteristics (iii) tides and tidal currents (iv) circulation, diffusion, and dispersion (v) numerical modelling. As first part of this series of work, the salinity data obtained at six sites by using instantaneous profil]ing technique were analyzed in detail. it is found that the amplitude of salinity variation increases toward the upstream direction and its magnitude is greater at neap tide than spring tide. And also duration of salinity boundary layer is much longer during the neap tide than the spring tide, As a result of this study, the Keum River estuary is classified as a typical standing wave type estuary. Finally, we present a schematic diagram for the duration of the salinity boundary layer, which will be useful for further study on flocculation phenomena and sedimentation dynamics.