Wave refraction, rocky coasts Flashcards
Alongshore sediment transport is always happening and so…
Amount of sediment transported adds up.
Longer time scales > storms and recovery.
Amount of transport depends on
Breaking wave height (higher wave = more force, more momentum)
Breaking wave angle relative to shoreline.
What determines wave breaking height and angle?
Refraction
How do waves refract?
Waves slow down in shallower water. If different parts of the crest encounter different depths on the bed -> the part of the crest in shallower water is moving more slowly and overall this results in the bending of a wave. Crests bend parallel to beach Swells = faster Velocity -> slow down more -> bend more
Amount of bending in wave refraction depends on
Velocity differences
Wave angle of approach (angle of incidence) in deep water
What also happens to a wave crest as it bends?
It stretches.
If part of it is moving faster than another, the more bending has to happen and the more stretching has to happen.
If stretched, means wave height has to get smaller (rubber band - stretching = thinning) forcing crest to get longer without changing mass.
Why do cliffs occur on some coasts (and barriers on others)?
The Bruun rule- given formative wave conditions, coastal profile wants to maintain this shape
- Can move left and up, or right and down
Background landscape slope
What is landscape slope?
Elevation over some cross shore distance
Define wave base
The place in the near shore where the wave energy is just beginning to interact with the bed.
Wave base is an average depth (since wave size might vary a lot for a given location)
Shape of the shore-face profile is a function of…
How the waves are interacting with the shoreline
Difference between landscape slope and shore-face slope?
Landscape slope- set by geologic setting, pre-existing geology
Shore-face slope- set by wave environment
Based on landscape slopes and shore-face slopes, how do you get a cliff?
If your landscape slope is steeper than your shore-face slope
