In this study, we investigate tidal wave propagation characteristics, and classify regional tidal regime using tidal form number considered distribution of astronomical tide, overtides, and compound tides in the Han River Estuary, Gyeonggi Bay. The characteristics of the tidal wave propagation in main channels show dominance of major tidal constituents (e.g., and) contributing to the astronomical tide however, distinct increasing of shallow water (e.g., M 4) and long period (e.g., MS f) components toward up-estuary. Using the characteristics of tidal form number to astronomical tide, overtides, and compound tides, the regional tidal regime could be assorted into three regions. Firstly, a dominance area of astronomical tide was presented from open sea to a front of Incheon Harbor (Yeomha channel) and to north entrance of Seokmo channel. The area between south and north entrance of Yeomha channel and Ganghaw north channel classified into zone of showing strong shallow water components. It could be separated into upper estuary, upstream the Singok underwater dam, showed dominance of shallow overtides (e.g., M 4 and MS 4) water and long-term compound tides (e.g., MS f) larger magnitude than astronomical tide. The shallow water components was earlier generated in lower part (south entrance) of Yeomha channel have strong bottom by effect of shallower and narrower compared with Seokmo channel. Tidal asymmetries of upper estuary cause by a development of overtides and compound tides are mainly controlled by influence of man-made structure.
This study estimates the region of freshwater influence (ROFI) by Han River discharge in the Yeomha channel, Gyeonggi Bay. A 3-D numerical model, which is validated for reproducibility of variation in current velocity and salinity, is applied in Gyeonggi Bay. Distance of freshwater influence (DOFI) is defined as the distance from the entrance of Yeomha channel to the point where surface salinity is 28 psu. Model scenarios were constructed by dividing the Han River discharge into 10 categories (200~10,000 m3/s). The relation equation between freshwater discharge and DOFI was calculated based on performing a non-linear regression analysis. ROFI in Yeomha channel expands from the southern sea area of Ganghwa-do to the northern sea area of Yeongheung- do as the intensity of Han River discharge increases. The discharge and DOFI are a proportional relationship, and the increase rate of DOFI gradually decreases as discharge increases. Based on the relation equation calculated in this study, DOFI in the Yeomha channel can be estimated through the monthly mean Han River discharge. Accordingly, it will be possible to respond and predict problems related to damage to water quality and ecology due to rapid freshwater runoff.
This study investigated the flow patterns and affecting factors in the North Port of Incheon, South Korea, to understand the inner-port circulation characteristics by applying an unstructured grid finite volume community ocean model (FVCOM) together with a field survey. The FVCOM considered the tide, river discharge, surface winds, and atmospheric pressure with the highest resolution of 50 m around the port. The model results were validated with current velocity and salinity observations. In the main channel, the difference in salinity between the sea surface and bottom increased during the neap tide due to weakened tidal currents, thus strengthening the stratification. However, at the inner port, strong stratification was observed during spring tide as the near-surface freshwater from upstream of the estuary moved relatively farther south of the port than that during the neap tide. Freshwater flowed into the port during the flood current and was trapped in the semi-closed geometry of the inner port. The horizontal salinity gradient between the trapped fresher water in the port and saltier water in the main channel increased during the flood current. As a result, density-driven circulations associated with near-bed currents towards the port were maintained for more than 3 h after high tide. This result implies that the baroclinic effect, mainly due to the salinity gradient in the North Port, could significantly affect residual circulation at the inner harbor in a macro-tidal environment and the mass transport mechanism, such as sediment transport. In general, such enhanced baroclinic effects due to salinity and tides are not limited to the North Port and can have greater effects on inner-port circulation in other macro-tidal harbors that suffer from severe sedimentation problems.
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