Known as the tidal current deposition with special morphology

the palm-like underwater bars in Jianggang Gulf of Subei were the result from transformation and redeposition of the ancient Huanghe and Changjiang Rivers sediment under the converging action of tidal current toward Jianggang Gulf after the northward migration of the Huanghe River into Bohai Sea. Such transformation and redeposition were the resultant of the attachment of sandy bars and sandy islands to the northern bank of Changjiang River

the southward migration of Changjiang River mouth and the subsequent formation of a broad gulf in the central-south coastal section of Subei. The alternation of sandy ridges with tidal channels gave rise to a wavy relief

with their strike being consistent with the direction of tidal current. These sandy ridges consist mainly of well-sorted fine sand and silt

positive or negative skewness in size distribution

whereas the channels are covered with a thin layer of silty sand sandy silt. Based on the investigation of the Jianggang Gulf

it may be concluded that the formation of this mode of underwater tidal bars requires the following four conditions: (1) a broad gulf having a shallow slope under the water; (2) a rich sedimental source or a great deal of loose sediments in this region; (3) a relatively stable coastal condition near the region; (4) a stable tidal action and a strong directive tidal current converging towards the top of the gulf.