Tidal currents are of great importance in many ways. These currents near the shore and in shallow water have great transporting power. In case their velocity is great enough, they may move material directly.
In shallow water on-shore waves stir up material lying on the bottom, and this is then picked up and moved laterally by the tidal currents. The strong tidal currents are of great significance to the shipping industry.
They influence the speed of the ship relative to the ground. For smaller vessels they may prove dangerous, especially when high, wind-generated waves run opposite to the tidal current. Smaller vessels may literally roll over by the sea before they can rise from a wave trough to the next wave crest.
Besides, if there is a storm, then short, breaking waves develops which are the most dangerous to small fishing vessels. Tremendous amount of energy is associated with tidal currents.
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Attempts are being made to harness the tidal energy technologically, but only limited success has been achieved so far. However, there is one disadvantage namely; there is periodical fluctuation in the tidal energy.
In a quarter of a tidal period, the tidal energy may oscillate from zero to the maximum value. In France, a very large tidal current power-station is being constructed in the Bay of St. Malo where the great tidal range of Europe occurs.
The tidal currents build up sand waves on the sea floor which are .5 to 2 meters high, and their length varies from 30 to 50 meters. These currents bring about a change in the bottom relief of the oceans which in turn influences the sea waves. Thus, the coastal morphology is largely affected.