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In mesotidal nearshore zones, patterns of sedimentation commonly are dependent on the characteristics of the interactions between wave surge and tidal flow. Sedimentary processes associated with waves alone or with tidal currents alone are generally insufficient for explaining the distributions, orientations, textures, and structures of bedforms in zones exhibiting wave-surge/tidal-current interactions. The resultant forces produced by the interaction of wave surge and tidal currents generally
have a greater influence on sedimentation than these individual components. Studies using fluorescent-tagged grains aided in determining the sedimentary responses of sand to the complicated interactions of wave surge and tidal flow.
In shallow, subtidal areas, bedform orientations and the greatest distances of sediment transport generally are determined by the directions of tidal flow. In shallower areas around the margins of offshore sand banks, bedform configurations and orientations are predominantly affected by wave surges, whereas the greatest distances of sediment transport are determined by tidal currents.
At intertidal parts of offshore sand banks, the characteristics of sedimentation during the flooding tide are predominantly controlled by surging waves. During the ebbing tide, the periodic wave surges and tidal currents are in opposite directions and sediment transport is in gyral paths.
At the shoreline, tidal and longshore currents are in separate zones and sediment transport is controlled by the directions of the water flow in the respective zones. When tidal and longshore currents flow in opposite directions, sediment transport is in bipolar flow directions corresponding to the flow in the respective current zones.
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