1. Assignment 3 - Solution

2. Assignment 3 - Grades

3. Wave Breaking
The release of energy derived from the wind, along a narrow coastal zone - geomorphic work done by wind, really, translated through medium of water.

4. Wave Breaking
In the next several lectures, we’ll cover the following topics:
Nearshore Wave Breaking
Surf Zone Wave Decay
Set-up and Set-down
Wave Runup
Infragravity Water Motions

5. Wave Breaking

6. Show videos of Wave Break
Vilano beach movie
Steamer’s Lane movie

7. Wave Breaking - Mathematically
As waves shoal into shallow water:
Wave steepness:
Wave height shoals up.
Wave length gets shorter
Steepness varies by h^(-3/4) going to infinity at the shoreline. Obviously cannot happen.
Something has to give!

8. Wave Breaking – When it occurs?.
Common misconception – “breaking is a result of waves dragging on the bottom, then trip forward due to friction” – NO!
Friction plays a very small role – computer simulations that completely neglect friction can still produce breaking waves.
A wave breaks when it becomes overly steep, because the velocity of water particles in the wave crest exceed the velocity of the wave form!

9. Style of Breaking
Schematic and traces of high-speed photos illustrating different types of wave breaking behavior.
But what causes each one of the different breaking styles?

10. Style of Breaking - Illustrated
Spilling waves (flat beaches)
Plunging waves (moderate beaches)
First observations recognized that beach slope and wave steepness had something to do with this...
Surging waves (steep beaches)

11. x < 0.5 xb < 0.4 x > 3.3 xb > 2.0 Iribarren Number x
This ratio of beach steepness to wave steepness has a deep-water form and a nearshore form.
0.5 < x < 3.3
0.4 < xb < 2.0
x > 3.3
xb > 2.0
From Battjes, 1974

12. Wave Break Style vs. Ir. #
Lab Results from a Wave Tank