Residual Flow and its Implication to Macro-Tidal Flats in Kyunggi Bay Estuary Of Korea

Abstract

The urban estuary, Kyunggi Bay in mid-west of Korea is undergoing coastal erosion and geomorphologic change near the tidal flats. Understanding the tidal flat dynamics requires the field observation as well as numerical modeling to find out the relevant cause factors. The residual flow, defined as the flow averaged over the tidal cycle, plays an important role in estuarine and coastal processes. The present study investigates the characteristics and variability of the residual flows at major channels. A set of one-year long current data measured by using acoustic current meters has been analyzed to estimate the residual flows by applying different averaging periods such as arbitrary periods, M2 and its harmonics, and fortnightly period. It is strongly recommended that the time average for the residual flow estimation should be done over the fortnightly at best, or over the harmonics of M2 tide. Taking average over arbitrary time span would yield unrealistic value. In Jangbong channel of Kyunggi Bay, the residual flow is the flood dominant one, while in the Seokmo channel the residual flow is ebb-dominant flow flowing southwestward. During the summer wet season, the residual flow at Seokmo channel shows the maximum in the year as 26.7 cm/s, enhanced by the fresh water discharging through the Seokmo channel, while the minimum of the year occurs at W21 as 15.7 cm/s due to the retarding effect of fresh water flowing in opposite direction. During winter, at W21 the maximum of the year reaches at 27.7 cm/s flowing eastward, while at W22 the minimum of the year reaches at 19.8 cm/s flowing southwestward (Ebb direction).