Yoon, B.I. and Woo, S.B., 2013. Tidal asymmetry and flood/ebb dominance around the Yeomha channel in the Han River Estuary, South Korea In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)

Several field measurements were conducted to study the characteristic of tidal asymmetry and flood/ebb dominance in the Han River Estuary (HRE), Gyeonggi Bay (GGB) on the western coast of Korea. Tidal currents at this area were simultaneously measured at four stations during the winter season, and previously observed tidal data were analyzed. The HRE is macro-tidal coastal zone with a mean depth less than 12m and a tidal range varying 3.5 (neap) to 8.0m (spring). The tidal amplitude to depth ratio is large enough to generate non-linearity in the tidal wave. The relative phases (2M₂-M₄) are represented flood dominant using harmonic constants from previously observed tidal data. However, there exists a limitation to apply this kind of method for tidal asymmetry to an area in which freshwater discharge is assumed to be relatively small. Statistical analysis of tidal current data in HRE indicated that ebb current is stronger than flood. Analysis of slack time of tidal current showed that ebb duration time is longer than flood. To find the mechanisms for the features of ebb dominance, a tidal curve was reconstructed the major component (M₂), in combination with the shallow water component (M₄). This tidal curve presented domination of flood current. However, these curves showed ebb dominance after incorporating the non-harmonic components that included ebb-directional flow, calculated from tidally-averaged current. The results show that the flood current is overcome by enhanced ebb directional effect, which occurs around the Yeomha channel in the HRE owing to the seaward effect of averaged flow. These ebb directional current could be produced by freshwater and nonlinear effects of long-term variation of sea surface slope due to estuary non-linearity.