Hydraulic action

The force of waves hitting against the coast weakens and breaks rocks, and the broken rocks are carried away by the water.

Another way is which water erodes the coast is when water enters lines of weakness in the rocks and compresses the air within these joints or cracks.

Thus, pressure is exerted on these lines of weakness. When the waves retreat, the pressure is release, causing the air to expand greatly.

Through repeated compression and expansion of air, the joints are weakened and eventually broken down.

Corrasion/Abrasion

Corrasion is the most aggressive form of coastal erosion. Materials such as pebbles and gravels carried by the waves repeatedly hit against the coast, breaking down the rocks and eroding the coast.

Attrition

Materials carried by the water collide with one another and are broken down into smaller, smoother and rounded pieces.

Solution/Corrosion

Solution refers to the dissolving of materials through chemical reactions. A good example of such a substance is limestone (calcium carbonate), which dissolves after reacting with seawater. Thus, the rocks break down.

Factors influencing rate of coastal erosion

The rate of erosion at different coasts are different due to many factors.

Type of wave

As destructive waves have a more powerful backwash, it erodes more materials than it deposits, thus, coasts with destructive waves are eroded at a higher rate.

Position of coast

The position of a coast determines if it is sheltered from prevailing winds, an exposed coast would be eroded at a higher rate than a sheltered coast such as a bay between two headlands. This is because coasts exposed to the prevailing winds are more exposed to wave action.

Composition and structure of rocks

The mineral composition of rocks affects their resistance to erosion, thus affecting the rate of erosion. Coasts with less resistant rocks would be eroded at a higher rate than those with more resistant rocks.

A rock with more lines of weakness would be less resistant to erosion, so the structure of rocks also affects the rate of erosion at coasts.

Climate

The rate of erosion is higher during monsoon seasons when there are strong prevailing winds blowing onshore, exposing the coast to more wave action.

Human Interference

Structures such as seawalls and breakwaters built on coasts help to reduce the amount of erosion.

A breakwater at East Coast helping to reduce erosion.