• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.289-296
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• 2009

The appearance and variation of cold water area and its expansion mechanism of tidal front in the south western coast of Korea in summer were studied on the basis of oceanographic data(1966-1995), satellite images from NOAA and SeaWiFs and numerical model. Cold water appearance in southwestern field of Jindo was due to the vertical mixing by strong tidal current. Tidal front where horizontal gradient of water temperature was more than $0.3^{\circ}C$/km parallels to contours of H/$U^3$ parameter 2.0~2.5 and the outer boundary of cold water region corresponds with contours of the parameter 2.5~3.0 in the southwestern sea of Korea during the period between neap and spring tides. The position replacement of tidal front formed in the study ares varies in a range of 25~75km and cold water region extends about 90km. These suggest that the magnitude of variation of frontal position and cold water area was proportionate to the tidal current during lunar tidal cycle. Moreover, it was estimated that the southwestward expansion of cold water region was derived from the southwestward tide-induced residual currents with speed more than 10cm/s.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.6
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• pp.582-596
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• 2013

In order to estimate the tide and flow properties around the archipelago, around Dolsan, Choyak, Geogeom and Jindo which located in the southwestern waters of the south sea of Korea, tidal currents, residual flows and tidal energy dissipation were investigated by using 2-dimensional numerical model. The maximum speeds of tidal currents are small around Dolsando(31.92 cm/s) and large around Jindo(87.55 cm/s). The residual flow is fastest around Choyakdo where many channels and islands as compared with other study areas. The area around Jindo has the highest currents speed, but shows the flat movements. The margins between the maximum and the minimum dispersion rates of tidal energy in the areas are estimated and designate the order of values around Dolsando($392.6{\times}10^7$ erg/s), Geogeumdo($125.7{\times}10^7$ erg/s) and Jindo($23.1{\times}10^7$ erg/s) sequently. These circumstances are same as in the amplitude of M2 constituent. This means that rapid depth changes and narrow channels play an important role in tide and tidal currents energy in archipelago.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.247-258
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• 2014

To evaluate the influence of the external force components on the littoral currents in the Gusipo beach, Jeonbuk, West Coast of Korea where a wide tidal sand flat developed, a coupled hydrodynamic model considered real time tidal currents and wave-induced currents was constructed in which the EFDC for tides and tidal currents, the SWAN for waves and the SHORECIRC for wave-induced currents were used as the hindcasting models. A series of field observations for tides, tidal currents and incident waves were carried out and especially to observe the littoral currents in the tidal sand flat, the GPS mounted and light weight drogues were used. Also wind data were collected from the adjacent weather station. To analyze the littoral current components, the numerical drogue tracking results considered real time winds, tides and waves were compared with the field drogue data. The drift speed of numerical drogues was reproduced as the range of 68.0~105.2% compared with the field data and the velocity error of main direction component showed a good result as -16.7~10.0%. As a result, in the mild slope tidal flat including wide surf zone, the tides and winds were the major affection component of the littoral currents, on the other hand, the wave-induced currents seemed the minor component when the incident wave heights were relatively small.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.217-227
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• 2012

On 31 March 2007, the abnormal wave occurred along western coast of Korean including Yeonggwang. In this paper, this event is studied using available field measurement data for the event analysis and numerical model for reproducing the unknown waves. We found several 1-min interval tidal elevation and mean sea level pressure (MSLP) data along the western coast of Korea and analyzed it using wavelet technique. We computed the arrival time and the propagation direction of abnormal wave using wavelet results and performed the numerical simulation using 2 dimensional shallow water wave model. The sea level under the forcing of air pressure jump was obviously amplified by the Proudman resonant effect. The computed sea levels compared with observations are underestimated, but the order of arrival time at the tidal station showed good agreement.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.236-244
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• 2014

This study considered a seagrass habitat in order to analyze the characteristics of a marine environment of seagrass located in the Seomjin river estuary, through an analysis of the distribution of the water depth, field observation, and three-dimensional numerical experiments using an EFDC model. The seagrass habitat was usually distributed at D.L(-) 0.5~0.0 m, and was hardly seen in the intertidal zone higher than that range. The distribution of the water temperature was within the range of $7.0{\sim}23.2^{\circ}C$, and the seagrass was demonstrated to have a strong tolerance to changes in the water temperature. In addition, the salinity distribution was found to be 27.2~31.0 psu, with suspended solids of 32.1 mg/L, which were higher than the previous research results (Huh et al., 1998), implying that there may be a reduction in the amount of deposits caused by the suspended solids. As for the sedimentary facies, they were comprised of 62.7% sand, 19.1% silt, and 18.2% clay, indicating that the arenaceous was superior and the sedimentary facies were similar to that of Dadae Bay. According to a numerical experiment, the maximum tidal current was 75 cm/s, while the tidal residual current was 10 cm/s, confirming that it sufficiently adapted to strong tidal currents. The erosion and deposition are predicted to be less than 1.0 cm/year. Thus, it is judged that the resuspension of sediments due to tidal currents and the changes in sedimentary facies are insignificant.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.276-276
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• 2022

Estuarine dams are constructed for securing freshwater resources, flood control, and improving upstream navigability. However, their impact on estuarine currents, stratification, and sediment fluxes is not well understood. To develop a general understanding, an idealized modeling study was carried out. Tide and river forcing were varied to produce strongly stratified, partially mixed, periodically stratified, and well-mixed estuaries. Each model ran for one year. Next, the models were subject to the construction of an estuarine dam and run for another year. Then, the pre- and post-dam conditions were compared. Results showed that estuarine dams can amplify the tidal range and reduce the tidal currents. The post-dam estuaries tended to be a salt wedge during freshwater discharge and a bay during no freshwater discharge. For all estuaries, the estuarine turbidity maximum moved seaward, and the suspended sediment concentrations tended to decrease. In terms of sediment flux mechanisms, the estuarine dam increased the seaward river runoff for cases with strong river, and increased the landward tidal pumping for cases with strong tides.

• Water for future
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• v.21 no.1
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• pp.87-94
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• 1988

Tidal asymmetry in the Keum River Estuary has been investigated from the observed tides. Despite strong frictional attenuation within the estuary, the $M_4$ tides reach significant amplitude, resulting in strong tidal distortion. The observed asymmetry over the area shows that generally more intense flood flows transport more sediment that do less intense ebb flows of longer duration. This causes filling of the estaury as evidenced by sand flats spreaded over the inner area. The spatial distribution of peak bottom stress associated with the dominant $M_2$ and $M_4$ tides calculated via two-dimensional numerical tidal model suggest that present tidal sedimentation regimemay be altered, sepecially in the approach channel to outer Kunsan Port and downstream part of the dike, due to the construction of barrier.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.219-235
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• 2013

In order to investigate the changes in sea water characteristics and stratification due to operation of Shihwa tidal power plant, three dimensional numerical model is used. In summer, the density of inner part of Shihwa Lake is more affected by salinity than water temperature due to fresh water discharge. Before tidal power plant operation, the sea water characteristics in Shihwa Lake shows relatively high temperature and low salinity. After tidal power plant operation, water temperature decreases slightly and salinity tends to increase in Shihwa Lake. Also, density increases and stratification tends to weaken by mixing with sea water.

• 한국해양학회지
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• v.12 no.1
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• pp.33-40
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• 1977

British Hydraulics research Station's Sparse Scheme was suggested for the solution of two dimensional finite difference tidal equations. 2D-numerical tidal model formed with 4.8km rectangular cells was set up to find out the barrage effects on tidal ranges of some possible areas for tidal power generation in Korea. The comparisons were made hetween spring tidal ranges with and without barrages at the entrance of Asan Bay, Garorim bay, Cheonsu bay and near Incheon Bay. Because of the coarseness of the grid, the model results could not represent the values of changes precisely. However the results show that the tidal amplitude near Incheon Bay increased by about 40cm by setting a barrage and about 50cm increase near the entrance of Asan Bay, respectively. But there were only a few centimeter changes in other areas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.151-164
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• 1998

Changes in tides and tidal currents in Chonsu Bay caused by the construction of Seosan A and B reclamation regions have been investigated using a depth-integrated two-dimensional tidal model. Three water level recorders were deployed for about one month and used for the specification of the open boundary condition. The computed currents were found to be in a good agreement with the measurements at two stations within Chonsu Bay. Comparison of the absolute velocities computed with the conditions before and after the embankment clearly shows that the reduction in tidal current amplitude is evident throughout the bay and the magnitude of the reduction increases to the north. Calculation shows that the embankment has advanced the time of drying at the northern part of the bay by about 51 minutes and has increased the exposure time by about 23 minutes. The high water time has advanced by about 1 hour, lowering the high water level by about 15 cm.