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Coastal Processes

Waves, tides, currents, rips, storm surges and tsunamis form and transform coastal landscapes.

Winds generate waves and create swell. Destructive waves cause erosion of coastal landforms and are often associated with storm conditions (see figure 2).

Constructive waves deposit sediments to form beaches and sand dunes and are associated with calm weather (see figure 3).

Swash is the water that is washed onto the beach when a wave breaks. Backwash is the water that runs back down the beach. Destructive waves have more powerful backwash than swash. Constructive waves have more powerful swash than backwash.

Figure 2 - Destructive Wave: 

The backwash is more powerful than the swash.

Figure 3 - Constructive waves:
The swash is more powerful than the backwash.

Long Shore Drift 

Longshore drift occurs when the ongoing swash and backwash moves in a sideways direction and moves material in a zig zag pattern along the coastline (see figure 4).

Erosion and deposition are the main natural processes that create coastal change.

Videos explaining Longshore Drift

Figure 4

Questions: ​

  1. Outline the two main coastal processes that form coastal landforms.

  2. Describe the differences between constructive and destructive waves.

  3. Explain how longshore drift moves sand along a coastline.

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