Marine Processes



Constructive Waves	Destructive Waves

Associated with calm weather. Are less powerful waves. Break on the shore and tend to deposit material. Are responsible for transporting material. Swash is stronger than the backwash.	Associated with storm conditions. Are created when the wave energy is high and there is a large fetch. Tend to remove material from the coast and are therefore associated with erosion. Backwash is stronger than the swash.

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Sediment Cell

Diagram to show the principal components involved in the development of a coastal sediment cell. | Source

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Pebbles

The action of waves constantly moves and sorts different sized material beach material.

On some beaches, the sediment is sorted alongshore so that the coarsest material is located at the position with the greatest wave energy and the smallest in the lowest energy environment.

The action of longshore drift can also sort grade beach material, due to the amount of energy required to move sediments. Larger particles will need more energy and therefore move at a slower pace.

Sediment also moves up and down the beaches. In these circumstances, there is little movement of water alongshore and most waves wash up and run back down the beach slope (as 'backwash'). The high sorting of beaches is due to the differentiating effects of swash and backwash. Coarser material is moved up the beach by strong swash, but the backwash is weakened by percolation. The coarsest materials tend to be found at the limit of wave action, while the finer ones are moved in to the lower energy zones offshore.