1. Field Trip Preparation
When: Tues. Mar. 30th, 2008, 8am - 6pm
Where: Leave from Williamson Loading Dock
What: ~3 stops, one paleo-coastal, the rest modern coastal, we’ll measure beach profiles, dig a trench, do a short beach walk, talk about waves, tides, and currents, and have lunch (either bring your own or ?)
Who: You all and me.
Vehicles?
Check the weather and dress appropriately
* We will discuss particulars in greater detail on Thursday in class.

2. Early Numerical Models

3. Early Numerical Models

4. More Recent Numerical Models

5. More Recent Numerical Models
Solitary Wave Runup on a beach

6. More Recent Numerical Models
3-D Weakly Plunging Breaking Wave on a Beach

7. More Recent Numerical Models
3-D Weakly Plunging Breaking Wave on a Beach

8. Wave Breaking Condition – g (gamma) - ratio of Hb to hb
Is this a constant? some disagreement
= > 1.03, from lab studies of monochromatic waves
For a given wave steepness, the higher the beach slope, the greater the value of b

9. Breaker Height Prediction - various forms
Munk (1949) - based on Solitary Wave Theory
Komar and Gaughan (1972) - based on Airy Wave Theory
Kaminsky and Kraus (1993) - based on Lab Measurements

10. Wave Breaking Exercise – Solitary Solution
>> H=1; T=20; L=9.8*(T^2)/(2*pi), S=H/L, Hb_s=H/(3.3*((S)^(1/3)))
L =
S =
Hb_s =
>> H=2; T=10; L=9.8*(T^2)/(2*pi), S=H/L, Hb_s=H/(3.3*((S)^(1/3)))
L =
S =
>> H=3; T=8; L=9.8*(T^2)/(2*pi), S=H/L, Hb_s=H/(3.3*((S)^(1/3)))
L =
S =
Hb_s =
>> H=4; T=15; L=9.8*(T^2)/(2*pi), S=H/L, Hb_s=H/(3.3*((S)^(1/3)))
L =
S =
Hb_s =
>> H=5; T=15; L=9.8*(T^2)/(2*pi), S=H/L, Hb_s=H/(3.3*((S)^(1/3)))
S =
Hb_s =

11. Breaker Height Prediction - reconfigured
Data span 3 orders of magnitude of breaker heights
Remarkably well-behaved data
----->

12. Plunge Distance

13. Surf Zone Wave Decay and Energy Dissipation
Steep, reflective beaches -
Wave breaking (and energy dissipation) is concentrated through plunging breakers.
Broken wave surges up the beach as runup.
Wave energy dissipation pattern depends on morphology of the beach
Villano Beach
Low-slope, dissipative beaches -
Extensive, wide surf zone over which spilling breakers dissipate energy.
At any time, several broken wave bores, and smaller unbroken waves, are visible.
Anastasia Island

14. Reasons for understanding surf zone wave decay
Understanding the patterns of wave decay in the surf zone is important for two significant reasons:
Wave energy dissipation is inversely related to the alongshore pattern of wave energy delivery -- so it can help identify relative vulnerability of coastal property.
Wave energy expenditure is partially transformed into nearshore currents, which are responsible for sediment transport and beach morphologic modification.

15. Thornton & Guza (1982) - Torrey Pines Beach
Torrey Pines Beach – fine sand with minimal bars and troughs.
Wave staffs and current meters - measurements from 10 m water depth to inner surf zone.
Published the distributions of wave breaking within the surf zone on a natural beach

16. Measurements of Wave Breaking Distributions
Histograms of breaking wave height distributions illustrate a greater fraction of broken waves at shallower depths.
Histograms of all waves in nearshore (broken and unbroken) show skewed distributions -- many small waves and few large waves -- comparable to that of a Rayleigh distribution, which also describe the distribution of deep water wave heights.
Histograms of broken waves only (cross hatched pattern) show a more uniform distribution.
Measurements of Wave Breaking Distributions
1. Constant H and T - Lab channel - easy to determine breaking conditions.
2. Natural setting - range of H and T, so surf zone witnesses range of broken/unbroken waves/bores.
Unbroken = Rayleigh distributions
Broken = Modified distributions

17. Energy Saturation of Broken Waves

18. Surf wave heights after initial breaking