15. Coastal Processes

Question 1

What are waves?

Answer 1

Waves are formed as a result of the friction between the wind and the surface of the sea

Question 2

What is swash?

Answer 2

Waves that move up the sea

Question 3

What is the backwash?

Answer 3

waves that move back down the beach

Question 4

What two factors determine the size of waves?

Answer 4

1. The fetch, which is the distance of sea over which a wave moves. The greater the fetch, the more powerful the waves
2. The speed and duration of the wind

Question 5

What is wave length?

Answer 5

The average distance between successive wave crests

Question 6

What is the wave crest?

Answer 6

The tallest part of the wave

Question 7

What is the wave trough?

Answer 7

The lowest point of the wave

Question 8

What is wave height?

Answer 8

The vertical distance between a wave trough and a wave crest

Question 9

What is wave refraction?

Answer 9

The process by which waves bend and change as they approach the shore due to difference in water depth.

Question 10

What are features of a destructive wave?

Answer 10

Wave height: High > 1m
Wave energy: High
Wave frequency: High > 10/min
Swash-Backwash: More backwash
Main process: Erosion

Question 11

What are features of a constructive wave?

Answer 11

Wave height: Low <1m
Wave energy: Low
Wave frequency: Low < 10/min
Swash-Backwash: More swash
Main process: Deposition

Question 12

What is hydraulic action?

Answer 12

The sheer force of waves smashing against a coastline. The type of rock impacts the erosive power, e.g sedimentary

Question 13

What is abrasion?

Answer 13

Rock and other materials being transported by the sea are thrown against the coast by waves. Abrasion is affected the hardness of material, velocity of waves and mass of objects

Question 14

What is attrition?

Answer 14

Rocks hit off each other in the sea and become round and smooth. Attrition is affected by size, shale and hardness of particles and wave velocity and temperature

Question 15

What is air compression?

Answer 15

Air is trapped in notches in the coast. When the wave hits, the air cannot escape and shatters rock over time

Question 16

What are features of coastal erosion?

Answer 16

Cliffs, Caves, Arches, Bays and Headlands

Question 17

What is a process of coastal transportation?

Answer 17

Longshore drift

Question 18

What are features of coastal deposition?

Answer 18

Beaches, Sand-Dunes, Sand Spits, Lagoons and Tombolos

Question 19

What are sea walls?

Answer 19

Concrete sea walls are built to protect coastal towns from attack from the sea, they have a curved top to deflect waves back out to sea.

Question 20

What is rock armour/riprap?

Answer 20

Large boulders placed at the base of soft cliffs or in front of sand dunes. The power of the wave is reduced as it hits the boulders

Question 21

What are groynes?

Answer 21

Low walls, often made of wood, built at right angles to the coast. They reduce longshore drift and encourage deposition of sand in certain areas of the beach

Question 22

What are gabions?

Answer 22

Wire cages filled with small stones placed along beaches or sand dunes. They break and absorb the power of waves and help slow down the rate of erosion.