Sediment Characteristics and Sedimentation Processes of Tidal Sand Flat(beach) in the Tide-Dominated Coast

초록

Various coasts have been designated as wave-dominated and tide-dominated. Typically, there is an association made between coastal morphology and the dominant process that operates on the coast. The surface sediment characteristics and sedimentation processes of tidal sandy flat (beach) depend upon the changes of the spatial and temporal hydrologic parameters (tide, wave, wind etc.). Tidal effects on beach processes have comparatively received little attention in the literature despite the fact that a significant proportion of the world’s beaches situates in mesotidal or macrotidal environments. Therefore, investigation of sediment characteristics, sedimentation processes of tide-dominated beach and sedimentological comparison with eastern and western beach of Korea Peninsular have been simultaneously done. Surface sediments have been sampled in the five western beaches in the tide-dominated (Eulwang-ri, Mongsanpo, Manlipo, Chonlipo, Taechon) and three eastern beaches in the wave-dominated (Kyongpodae, Bongpyung, Taejin) bimonthly or seasonally (1991. 3, 7, 9 and 1996. 11  1997. 9). Simultaneously, beach profiling and leveling have been done to compare between morphologic variation and sedimentation processes. The textural parameters of surface sediments have been calculated by the graphic method of Folk and Ward (1957). Surface sediments of western beaches are characterized relatively by finer grain size (medium sand and fine sand) and poorly sorted distribution in comparison with coarser, well sorted those of eastern beach. Grain size distribution of western beach shows a finning trend toward offshore, while medium sand is significantly dominant in surf zone due to the effect of wave breaking. Beach sediments in the tide-dominated, transported shoreward during flood tide, have been winnowed out by wave action, in the same time, resuspended sediments have moved offshore during ebb tide. In eastern beaches, surface sediment characteristics are influenced by