The Coastal Zone: How do waves shape our coastline?

Backwash

Water returning to the ocean from waves washing onto a beach. The movement of water back to the sea after a wave has broken on the shore. The movement is at right angles to the coast.

Wave length

The distance between two successive wave crests

Fetch

The distance of open water over which the wind can blow.

Swash

The movement of water up the beach after a wave breaks.

Crest

The top of the wave.

Constructive wave

Small waves that contain less energy. Sand and other materials are more likely to be carried up in the swash and laid down as deposits on the beach. They are small waves with a long wave length and low frequency. Swash is stronger than the backwash, therefore deposition is greater than erosion.

Destructive wave

Stronger waves that remove some of the materials from the beach. Here backwash is stronger than swash, therefore there is more erosion than deposition. They are larger waves, which are steep with a short wave length. They have a high frequency and steepen rapidly when reaching the shore and plunge over.