Tidal bedforms in eastern part of the Bohai Sea

A system of tidal bedforms has developed in the part of the Bohai Sea. It consists of the Laotieshan Channel, the Liaodong Shoal and the Shoal. The first of these is a tidal current scour region and the other two are tidal current depositional regions. The morphology of the sea floor has a close relation with tidal current vekxity. The maximum tidal current velocity is up to 5 knots in the Laotieshan Channel where strong erosion occurs. The maximum tidal current velocity is 1.3-2.3 knots and the absolute value of M₂ tidal current ellipticity is less than 0.4 in the Liaodong Shoal, indicating that the reciprocating tidal current is strong enough to form tidal sand ridges. The maximum tidal velocity is 1.2-1.6 knots and the absolute value of M₂ tidal current ellipticity is larger than 0.4 in the Bozhong Shoal, indicating that rotation of tidal currents increases so as to form tidal sand sheet. The small-scale bedforms surveyed in detail in the area and shown in the side scan sonar mosaic are subaqueous dunes, sand ribbons, comet-tail marks and scour furrows, which indicate that the sand ridges and sand sheet are still under the action of tidal current processes at the present time. Based on the interpretation of tidal currents, bedforms, and sedi ment thickness, it is inferred that the general direction of sediment transport within the study area is from the Laotieshan Channel to the Liaodong and Bozhong Shoals. The small scale bedforms in the detailed survey area indicate that the net sediment transport direction is from south to north.