Seasonal Changes in Sediment Characteristics on the Tidal Flat in Geunso Bay, West Coast of Korea

Abstract

Geunso Bay, located in Taean, western Korean Peninsula, is a semi-enclosed-type bay with a mean tidal range of about 6 m. Tidal flats are largely developed along the sides of the bay. A digital elevation model showed that 95% of the total area of the bay is tidal flat. Observations in both winter and summer of 2009 revealed that the surface sediments in the bay were mainly muddy sand, and the sediments were classified into five sedimentary facies: sandy silt, slightly gravelly sandy mud/sandy mud, slightly gravelly muddy sand/muddy sand, silty sand, and sand. In the eastern tidal flat, the annual sedimentation rate ranged from -71.3 to 12.4 mm/year, with a net erosion rate of -15.0 mm/year. Erosion was dominant on the tidal flat in the middle part of the bay, whereas deposition occurred in the western tidal flat in winter and spring, with a net deposition rate of 10.8 mm/year. Suspended sediments were supplied to the bay in relatively large amount in winter and spring and were transported in an anti-clockwise direction. Winter waves played a limited role in the seasonal variation in sedimentation due to the southwestward opening bay mouth. It seems that the supply of suspended sediments and the circulation pattern of tidal currents are the most important factors for seasonal variations in sediments on the Geunso tidal flat.