• Journal of the Korean Professional Engineers Association
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• v.35 no.4
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• pp.48-51
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• 2002

Due to locally torrential downpours which shows Increasing trend, high tide of the southern sea of Korea and etc. submerged and Inundated districts at the lowlands of Nakdong River Basins has been Increasing year by year In order to protect flood hit, it is necessary to make an early implementation of flood control dam and other flood protection works according to Nakdong River Comprehensive Development Project. In addition to the large scale comprehensive projects, local key measures, such as lowland development control, embankment reinforcement, leakage protection, maintenance and management of facilities, increase in pumping station, will be highly effective.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.111-122
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• 2010

As the Jamsu-bridge and the floodplains of the Han River can be flooded during the rainy season, the exact prediction of the peak flood time is very important for mitigation of flood hazard. This study analyzes the effect of outflow of Paldang Dam and tide of Yellow Sea on the Han River. A target area is from the Paldang dam to Jeonryu gauging station. Water level of Jeonryu as a downstream boundary condition was estimated through multi linear regression analysis with outflow of Paldang dam and tide level of Incheon, because it was influenced by both a tide of Yellow Sea and outflow of Paldang dam. In this study, Water Level Rising Travel Time of the Jamsu-bridge and some floodplains in the Han River are estimated. Also, The second order polynomial expressions for relationships of outflow of Paldang Dam and Water Level Rising Travel Time were developed considering the outflow of Paldang dam and tide of Yellow Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.6
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• pp.511-516
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• 2004

As a preliminary study on the sediment flux, concentrations of suspended particulate matter and current speeds were measured at three inlets of Gwangyang Bay during one tidal cycle of a spring tide of March 2003. The suspended sediment flux rate $(g/m^{2}/s)$ at the mouth of Seomjin River (St. K1) was observed to be higher throughout surface layer during ebb tide $(14.3\;g/m^{2}/s)$ and throughout near-bottom layer during the flood tide $(23.2\;g/m^{2}/s),$ resulting in a net upstream-ward transport of$0.9{\times}10^{3}kg/m$ during 13 period. At the inlet toward Yeosu Bay (St. K2), a relatively low rate ($(5.0-6.7\;g/m^{2}/s)$ of sediment flux occurred throughout the water column compared to St. K1, with a depth-integrated net transport of $5.6{\times}10^{3}kg/m$ toward the outer reaches of Gwangyang Bay inlet. At St. K3 located at Gwangyang Bay-side of Noryang Strait, the outward flux toward the Jinju Bay was observed to be dominant during the flood tide $(16.2-23.2\;g/m^{2}/s)$, especially through the mid and near bottom layer, compared to the inward flux throughout the whole water column during the ebb tide $(13.1-19.7\;g/m^{2}/s).$ The net transport at St. K3 was calculated to be $4.0{\times}10^{3}kg/m$ toward the outside of Gwangyang Bay. The outward net transport of suspended sediment at all three inlets seems to be consistent with a trend of bottom sediment texture, which suggests a net movement of sediment from a relatively coarse and poorly sorted inner-bay toward a relatively fine and better sorted outer-bay environment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.3
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• pp.214-227
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• 2021

The distribution of tidal current and tidal induced residual current, topographical eddies and tidal residual circulation in the waters surrounding the Geumo Island-An Island channel were identified through numerical model experiments and vorticity balance analysis. Tidal current flows southwest at flood and northeast at ebb along the channel. The maximum flow velocity was about 100-150 cm/s in neap and spring tide. During the flood current in the neap tide, clockwise small eddies were formed in the waters west of Sobu Island and southwest of Daebu Island, and a more grown eddy was formed in the southern waters of Geumo Island in the spring tide. A small eddy that existed in the western waters of Chosam Island during the ebb in neap tide appeared to be a more grown topographical eddy in the northeastern waters of Chosam Island in spring tide. Tidal ellipses were generally reciprocating and were almost straight in the channel. These topographical eddies are made of vorticity caused by coastal friction when tidal flow passes through the channel. They gradually grow in size as they are transported and accumulated at the end of the channel. When the current becomes stronger, the topographic eddies move, settle, spread to the outer sea and grow as a counterclockwise or clockwise tidal residual circulation depending on the surrounding terrain. In the waters surrounding the channel, there were counterclockwise small tidal residual circulations in the central part of the channel, clockwise from the northeast end of the channel to northwest inner bay of An Island, and clockwise and counterclockwise between Daebu Island and An Island. The circulation flow rate was up to 20-30 cm/s. In the future, it is necessary to conduct an experimental study to understand the growth process of the tidal residual circulation in more detail due to the convergence and divergence of seawater around the channel.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.2
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• pp.114-125
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• 2020

In order to understand the currents around Hampyung Bay and Haeje Peninsula, 2D numerical simulations for tidal currents and tide-induced residual currents were carried out. Dominant semidiurnal tidal currents have reversing form and flow NNE-SSW from northern Haeje Peninsula to Songi Island, E-S at northern Haeje Peninsula and NNW-SSE in Hampyung Bay. In flood, a part of currents from Imja Island~Nakwhol Island flow along the main stream flowing northeast at offshore region and the rest flow into Hampyung Bay flowing east along the northern coast of Haeje Peninsula. In ebb, currents from Hampyung Bay flow west along the northern coast of Haeje Peninsula and run together with the main stream flowing southeast at offshore region. The currents create an anticyclonic circulation in flood and a cyclonic circulation in ebb around Haeje Peninsula including Hampyung Bay. Tidal currents are accumulated on Doripo which located at the entrance of Hampyung Bay and show high current velocities. Tidal currents and tide induced residual currents are weak at the inside of Hampyung Bay which has narrow entrance, shallow water depth and wide intertidal zone. An anticyclonic eddy is formed around Gaksi Island as a result of tide induced residual currents. In northern coast of Haeje Peninsula, slow constant currents flow east. It is expected that a gradual change of sediment and an increase of flushing time for suspended materials are carried by tidal currents occurring in Hampyung Bay.

• Journal of Korea Water Resources Association
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• v.45 no.9
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• pp.915-928
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• 2012

Han River estuary (HRE) is located at the middle of the western coast of Korea, and tidal currents were measured at 4 stations in this estuary during the winter season, and previously observed tide data was analyzed. The results of amplitude ratio of $M_4/M_2$ showed that increasing upward to estuary in the HRE. Tide harmonic constants of relative phase $2M_2-M_4$ represent flood dominance, with under 180 degree. But this method has a limit of analysis that typically based on the non-linear distortion of the tidal current in tidal lagoon system where freshwater discharge is assumed to be relatively small. The results of statistically tidal current data indicated that ebb current velocity would be great unlike tide data. Ebb and flood duration time is calculated by slack time of tidal current showed that ebb duration time is longer than flood. The results of correlation of analysis show high value (0.9) between tidal current stations from Incheon harbor to north entrance of Yeomha channel. We reconstructed to find the reasons for the features of ebb dominance the results of harmonic analysis. As major component ($M_2$) in combination with shallow water component ($M_4$), the tidal curve was presented flood dominance that has a flood current is stronger. However, these curve were changed to ebb dominance add up the non-harmonic components that had ebb direction flow by calculated tidally averaged current. The characteristic of enhancement on ebb is showed around the Yeomha channel in the HRE, because averaged flow which acts seaward such as long-term tidal current components due to non-linear effect and freshwater which overcome the flood current.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.266-274
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• 1997

To understand seawater exchange are important to analyze the formation of watermass, material circulation and transfer of pollutant material etc. The purpose of this study is to review the previous studies and to propose new exchange ratio. where,$C_1$ ; average salinity of the water at low water$C_2$ ; average salinity of the water at the next low water$C_0$ ; average salinity of the water passing the bay mouth on the flood tide$V_2$ ; total water volume of the bay on the low water$V_0$ ; the volume of the remaining outer bay water entering during the flood tideSeawater exchange ratio of Dongho Bay calculated by new method are 26.1%, 23.8% respectevely.The average fresh water residence ratio calculated by equation (12) is 2.2 days, that is corresponding 23.5 % of exchange ratio. Thus, it appears similar result as proposed exchange ratio.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.13 no.1
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• pp.1-5
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• 1977

A series of echo-sounding and current measurements as well as the drogue and the drift bottle experiments were carried out in Asan Bay since November 1974. Several sand bars or sand flats covered by silts were developed at ebb tide in the bay. Sand waves and sand ripples were seen on the surface of the sand bars, around which sea channels of 8~ 12 meters in depth are formed. The main stream axis of the flood current which is separated into east and west branch flows southward. A cyclonic and an anticyclonic eddy are developed at the early stage of flood tide. They are transformed into a clockwise eddy before the slack water. The maximum tidal current speed observed was 3.1 ~ 3.2 knots at the entrance of the bay, while it was 1.O ~ 2.8 knots in the bay. The location of the main stream axis of the tidal current coincides well with the sea channel. A salt wedge was observed at the estuary of the Sabgyo-cheon River.

• Water Engineering Research
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• v.2 no.2
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• pp.113-121
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• 2001

The objective of this study is to develop a prediction mode for a flood forecasting system in the downstream of the Nakdong river basin. Ranging from the gauging station at Jindong to the Nakdong estuary barrage, the hydraulic flood routing model(DWOPER) based on the Saint Venant equation was calibrated by comparing the calculated river stage with the observed river stages using four different flood events recorded. The upstream boundary condition was specified by the measured river stage data at Jindong station and the downstream boundary condition was given according to the tide level data observed at he Nakdong estuary barrage. The lateral inflow from tributaries were estimated by the rainfall-runoff model. In the calibration process, the optimum roughness coefficients for proper functions of channel reach and discharge were determined by minimizing the sum of the differences between the observed and the computed stage. In addition, the forecasting lead time on the basis of each gauging station was determined by a numerical simulation technique. Also, we suggested a model structure for a real-time flood forecasting system and tested it on the basis of past flood events. The testing results of the developed system showed close agreement between the forecasted and observed stages. Therefore, it is expected that the flood forecasting system we developed can improve the accuracy of flood forecasting on the Nakdong river.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.167-175
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• 2005

Based on the observation on 20, 23 and 26 July 2004, the distributions of temperature, salinity and stratification was investigated in relation to ebb, turn of tide and flood. The results are as follows: I) The high temperature and low saline water with $23.5\~24.0^{\circ}C\;and\;32.4\~33.0psu$ existed at Naro Island. 2) The cold surface water below $21.0^{\circ}C\;and\;33.0\~33.4psu$ appeared in the area near Gae Island and Geumo Island. 3) The cold and saline water, below $24.0^{\circ}C$ at the surface and $17.0^{\circ}C$ near the bottom, $32.8\~33.8psu$ at the surface and $33.8\~34.0psu$ near the bottom, existed in Sori Island. These waters were more saline compared to the South Sea Coastal Water with about 31.8psu. This suggests that the oceanic saline water intruded into the Bottol Bada through the area near Sori Island. The stratification appeared during all the observation periods due to a high solar radiation of $22MJ/m^2$, and a weak wind speed of 2.9m/s on the average while the mean speed of wind in July is around 3.9 m/s. It qualitatively suggested that the stratification was maintained during the observation periods because of a high solar radiation, a weak wind speed and intrusion of saline oceanic water.