Waves And Beaches Flashcards
What causes waves?
Most waves originate locally - forming when wind blows over water.
What affects their size?
It’s related to wind speed (the greater the speed, the greater the wave).
What does wind do?
Creates frictional drag, which produces movement in the upper surface of the water.
What happens when waves approach the coast?
The water becomes shallower and the circular orbit of the water particles changes to an elliptical shape.
The wavelength and the velocity both decrease, and the wave height increases - causing water to back up from behind.
Force pushes the wave higher, so that it becomes steeper before spilling (or plunging) and breaking onshore.
The water rushes up the beach as swash, and flows back as backwash.
What is wavelength?
The distance between the crests of two waves
What is swash?
When a wave breaks, water is washed up the beach.
What is backwash?
When water runs back down the beach.
What is fetch?
The distance of open water over which waves move.
The greater the fetch, the larger the wave.
What are the different types of waves?
Constructive
Destructive
What are constructive waves?
Low, surging waves - with a long wavelength
Strong swash, weak backwash
Beach gain (constructive)
What are destructive waves?
High, plunging waves - with a short wavelength
Weak swash, strong backwash
Beach loss (destructive)
What is morphology?
Form or shape
Beaches consist of loose material so it alters as waves change.
How do beach profiles change?
Seasonal changes in wave type create summer and winter profiles or gradients - sediment is dragged offshore by destructive waves during winter, and returned by constructive waves in summer.
What happens to size and type of sediment?
Beach material becomes smaller towards the shoreline.
