15. Coastal Processes Flashcards
What are waves?
Waves are formed as a result of the friction between the wind and the surface of the sea
What is swash?
Waves that move up the sea
What is the backwash?
waves that move back down the beach
What two factors determine the size of waves?
- The fetch, which is the distance of sea over which a wave moves. The greater the fetch, the more powerful the waves
- The speed and duration of the wind
What is wave length?
The average distance between successive wave crests
What is the wave crest?
The tallest part of the wave
What is the wave trough?
The lowest point of the wave
What is wave height?
The vertical distance between a wave trough and a wave crest
What is wave refraction?
The process by which waves bend and change as they approach the shore due to difference in water depth.
What are features of a destructive wave?
Wave height: High > 1m
Wave energy: High
Wave frequency: High > 10/min
Swash-Backwash: More backwash
Main process: Erosion
What are features of a constructive wave?
Wave height: Low <1m
Wave energy: Low
Wave frequency: Low < 10/min
Swash-Backwash: More swash
Main process: Deposition
What is hydraulic action?
The sheer force of waves smashing against a coastline. The type of rock impacts the erosive power, e.g sedimentary
What is abrasion?
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
What is attrition?
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
What is air compression?
Air is trapped in notches in the coast. When the wave hits, the air cannot escape and shatters rock over time
What are features of coastal erosion?
Cliffs, Caves, Arches, Bays and Headlands
What is a process of coastal transportation?
Longshore drift
What are features of coastal deposition?
Beaches, Sand-Dunes, Sand Spits, Lagoons and Tombolos
What are sea walls?
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.
What is rock armour/riprap?
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
What are groynes?
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
What are gabions?
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.
