근소만 퇴적물 특성 변화

Abstract

The western tidal flats of Korean Peninsula are widely developed due to relatively large tidal ranges (max. 9 m). The sedimentary processes on the tidal flats are directly influenced by monsoons, resulting deposition and/or erosion of sediments. Geunso Bay in the mid-west of Korea is a semi-enclosed bay with a mean tidal range of about 6 m. Digital elevation model showed that 95% of the total area of the bay was tidal flat. In order to understand seasonal variations of sediment characteristics on Geunso tidal flat, sedimentary analysis and monitoring sedimentation rates were conducted. The surface sediments in the bay consisted of mainly muddy sand and were classified into five sedimentary facies in winter and summer 2009. The sedimentation rates were determined by burying a plate at sub-bottom depth and periodically measuring the changes in depth between the surface and plate. In the eastern tidal flat, the annual sedimentation rates were ranged -71.3 to 12.4 mm/year, resultantly annual erosion rate of -15.0 mm/year. The erosion was dominated on the middle part of the tidal flat, while the deposition on the western tidal flat during winter and spring with the net depositional rate of 10.8 mm/year. The suspended sediments were supplied relatively a large amount into the bay in winter and spring and were transported in anti-clockwise direction. Sediment transport paths were calculated using grain-size parameters of the surface sediments in winter 2009. The resultant sediment transport pattern showed relatively predominant westward transport vectors in the tidal flat. The winter waves played a limited role in the seasonal variation of sedimentation due to the southwestwardly opened bay mouth. It seems that the supply of suspended-sediments is most important for seasonal variation of sediments on the tidal flat. The net sedimentation showed that the deposition occurred in the western tidal flat and the erosion occurred in the middle and eastern tidal flat of the bay.