CHARACTIERISTICS OF THE TOPOGRAPHY AND SOIL IN FORESHORE TIDAL FLATS AND ITS TYPE CALSSIFICATION

A series of field surveys investigating the stability of natural/manmade tidal flats were conducted from June 2000 to April 2001, i. e., the profile of the seabed and the stiffness and grain-size distribution of sediment were measured. Five natural and seven artificial tidal flats were investigated including one natural and three artificial sand beaches. The terrace of the foreshore region in most natural tidal flats consists of a main flat part and a multiple bar-trough part (multi-bar). The former serves as an important habitat, while the latter is needed to ensure stability of the main flat part against wave actions which occupy the area from the ebb tide shoreline to 200-350m shoreside. Types of forcshorc tidal flats are classified in the condition of the incident wave height and the grain-size of bottom sediments.