HIGH-RESOLUTION MORPHOLOGICAL CHARACTERISTICS OF SAND WAVES OFF THE WEST HAINAN ISLAND

The sand waves in the eastern Beibu Gulf off Dongfang coast were high-accurately investigated by using SIMRAD-EM3000 multibeam sounding system and DGPS position system. The investigated results indicate that:(1) the bedform from coast to continental shelf obviously has the character of zonation, that is poor-erosion zone, the sand wave and ridge zone and the flat zone. Sand waves only exist in the sand wave and ridge zone, which is in the depth of 20~50 m. The sand waves have many shapes, including two and three dimensional sand waves. The wave height is 0.7~2.5 m and length is 20~70 cm, and the ratio of L/H is 20~60 and the symmetry index (the ratio of gentle slope to steep slope) is 1~3. (2) The transportation direction of the sediment in sand wave and ridge zone presents an apparent regularity. On the west edges of the ridges, sediment transport is mainly towards north; while on the east edges of the ridges, sediment transport is mainly towards south. (3) The formation and development of these sand waves are mainly controlled by tidal current and also influenced by tropical storm.