Coastal processes

Waves can be destructive or constructive.

When a wave breaks, water is washed up the beach - this is called the swash. Then the water runs back down the beach - this is called the backwash. With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger  than the swash.

Destructive wave

• destructive waves are created in storm conditions.
• are created from big, strong waves when the wind is powerful and has been blowing for a long time.
• occur when wave energy is high and the wave has travelled over a long fetch.
• tend to erode the coast.
• have a stronger backwash than swash.
• have a short wave length and are high and steep.

Constructive waves

• constructive waves are created in calm weather and are less powerful that destructive waves.
• break on the shore and deposit material, building up beaches.
• have a swash that is stronger than the backwash.
• have a long wavelength, a low height.

The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways:

Hydraulic action.-Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.

 Abrasion- Bits of rock and sand in waves grind down cliff surfaces like sandpaper.

• Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
• Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone

transport

There are various sources of the material in the sea. The material has been:

• eroded from cliffs.
• transported by longshore drift along the coastline.
• brought inland from offshore by constructive waves.
• carried to the coastline by rivers.