한국 서해안 강화 갯벌의 퇴적환경 변화

Abstract

The southern tidal flat of Kanghwa Island with an area of approximately 90 km2 is one of the biggest flats on the west coast of Korea. Tide is typically a semidiurnal with maximum range about 10 m. As a big tidal flat in the estuary of Han River system, the tidal flat receives large amount of nutrients from land and contains diverse fauna and flora. Recently, constructions of artificial structures such as new airport, island-connecting bridges and dikes near the tidal flat might change tidal current and river flow patterns. These have an effect on sedimentary environments and ecosystem in the tidal flat. The purpose of this study is to investigate changes sedimentary characteristics on the tidal flat due to artificial impacts. Surface sediments for sedimentary analyses were sampled at 83 stations in August 1997, September 1999, August 2000 and August 2003. Generally, the very poorly-sorted mud sediments were predominant in the eastern part, whereas the poorly-sorted sandy mud sediments were dominant in the western part of the tidal flat. The area of mud sediment distribution diminished, but that of sandy mud sediment extended during study periods. The short-term net sediment accumulation rates indicated that the sediments deposited continuously in the eastern part, but eroded in the western part of the tidal flat. The seasonal variations of sedimentation showed that deposition occurred during the period of spring to summer, whereas erosion occurred in winter in the western part of the tidal flat. 12.5 hour-anchored survey was carried out for measurements of hydrodynamic parameters at Yeomha channel near Choji Bridge (K1) and channel near Tonggom Island (K2) in June 2003. Residual flows indicated strong ebb-dominated tidal currents. Depth-integrated net suspended sediment loads (Qs) for one tidal cycle were seaward movement with 309,217.9 kg/m and 128,123.1 kg/m at station K1 and K2, respectively. The higher value of Qs at station K1 suggested that lots of suspende