Bedform dynamics and sand transport pathways in the Garolim Bay tidal flat, west coast of Korea

An autonomous instrument was deployed over a period of 17 days on the sand flat in Garolim Bay, west coast of Korea to investigate sand transport and bedform dynamics. Spring tidal currents reaching up to 0.9 m/s in depth-averaged speed generated 3-D, small dunes with average wavelength and height of 2.3 m and 0.15 m, respectively. The dunes migrated back and forth in response to reversing tidal currents with the migration distance less than one wavelength for each of flood and ebb. With a decrease of current speed below ca. 0.6 m/s (depth-averaged) during the spring-neap transition, the dunes were rapidly replaced with 3-D ripples. The ripples, however, did not grow to dunes with increasing current speed in the following spring tide. Bedload transport was estimated quantitatively on the basis of the hydrodynamic data. Over the measurement period, repeated flood-and ebb-oriented transport towards the SSW and the NE, respectively, resulted in residual bedload transport towards the ESE. By synthesizing the present result with the previously known bedload transport in the adjacent subtidal areas, it is inferred that the sands in Garolim Bay circulate through the subtidal channels and sand bodies and the intertidal flat, following two, discrete but interconnected, clockwise pathways.