Lecture 9: Surfzone Circulation

Question 1

Is energy flux conserved in a surfzone?

Answer 1

Surfzone: Waves slow down, height decreases (energy flux is not conserved)

Some lost to sound, foam, mixing ect..

Question 2

Do waves effect water level in an area?

Answer 2

Yes

• Waves also effect the mean
  water level. This drives currents.

Question 3

What is ‘wave set up’

Answer 3

• Wave set up:

rapid increase in mean water level in surfzone

Question 4

What is ‘wave set down’

Answer 4

• Wave set down:

small decrease in mean water line in shoaling zone

Question 5

Is wave set up larger with big or small waves?

Answer 5

• Wave setup is larger with
  large waves

Question 6

How do surfzone currents form?

Answer 6

• Pressure gradients can drive
  currents
• If there is variation (gradients) in
  wave height in along-shore direction, this results in alongshore pressure gradients, drive currents

Question 7

If a wave shoals at an angle what happens?

Answer 7

closest angle to the beach will break force. Mean water level in the area will be higher than along the angled wave.

following the pressure gradient a horizontal current is formed.

Question 8

What would happen if there was no variation in the sea floor in the surfzone?

Answer 8

: Without alongshore wave variation, there are no horizontal wave-driven currents