As the waves move away from a storm centre, their lengths increase relative to their heights. Small waves, on the other hand, disappear sooner. This is how the long swell is produced from a distant storm.

These waves, if they are of moderate size, build up the beach, and are called constructive waves. The rate of travel of these waves is fast, and they have a low orbital velocity. In such cases the backwash of one wave has hardly returned before the succeeding wave breaks.

The fast returning wave appears to transfer all its momentum and energy into the swash which, as a result thereof, rushes much farther up the beach. The orbital velocity of water particles also ends abruptly at the breaking point. Besides, the backwash becomes weaker due to friction with the sea bottom down the foreshore.

It is undoubtedly true that independent and solitary waves of translation play dominant role in moving the material landward and deposit the same at the shore.


According to Grant, oscillatory waves can transport materials on a sea floor in the direction of their propagation because of the difference in their forward and backward velocities in favour of the landward movement.