1. Coastal Processes and Observations

2. What is a beach? Different things to different people
Strip of unconsolidated material, the shape of which is dependent on:
Wave and tidal energy
Quality and quantity of sediment supply
Respond with great sensitivity to the forces that act on it
Wind
Waves
Currents
Acts as a buffer – retreats when things are rough and returns when things calm down. Shapes itself to best absorb the amount of energy in the waves.

5. Waves Driving force behind most coastal processes
Locally, most common are wind driven waves – initiated by wind shear
Wave height is determined by
Speed
Duration
Fetch – distance a wave travels

6. Wave Anatomy Per Wave length – in meters
Wave Period – Time it take for one complete wave cycle to pass a reference point (sec-1)
Wave Frequency – Number of cycles that pass an observer in a given time

7. Shallow Water Waves
Waves that can feel the bottom – affects the oscillatory motion of the wave particle – begins when depth(z) is half of the wave length (L)
Velocity slows because of drag
Period remains the same
Length decreases
Height increases – wave moves faster at the crest, crest overtakes the trough. When the crest is no longer supported, the wave breaks. Once the wave breaks, particles no longer move in oscilatory motion.

8. Wave Animation Particles travel in clockwise circles
The radius of the circles decreases as the depth into the water increases.

9. Results of Waves Slope of the beach face Long Shore drift
Product of the interaction of swash and backwash
High energy – steep slope, sand being removed
Low energy – shallow slope, sand being added
May be seasonal
Long Shore drift
Mostly responsible for movement of sand
Waves striking at an angle forces surf zone water to move laterally
Breaking waves suspend the sand, LS drift moves it

10. High Energy Beach

11. Low Energy Beach
High Energy

12. Longshore Drift

13. Calculations C=√gz P1 = c (⅛ ρ g H2) sinα cos α Wave speed (c):
Acceleration due to gravity (g) = 9.8 m/sec2
Water Depth (z)
Power of Longshore Transport:
Density of seawater (ρ) = 1015 kg/m3
Angle of the wave to the beach (α)
Power of longshore transport (P1)
Wave Height (H)
C=√gz
P1 = c (⅛ ρ g H2) sinα cos α

14. Rate of Sediment Movement
Density of the sediment (σ) = 2650 kg/m3
Coefficient relating to loss of water due to percolation through sediment = 0.77
Coefficient related to the packing of the individual grains = 0.6
Longshore rate of sediment movement for sand in m3sec-1 (qs)
qs= 0.77 P1/(σ – ρ)g 0.6

15. Littoral Environmental Observations
Simple beach observations and measurements that, if taken over a long period of time, may be used to model coastal erosion and deposition.
Pre-designed data forms to simplify data input and make sure all data are collected
A lot of information can be gathered in a short period of time that gives a relatively sophisticated picture of what is happening

17. Redundancy on Data forms – QC Wave Period (meter stick)
11 crests = 10 wave lengths
Normalize data
Breaker Height (meter stick)
Distance between crest and trough, not bottom
Estimation
Convert inches to ft
Wind speed
Anemometer
Foreshore Slope
inclinometer
Width of surf zone
Where waves start to peak up to where they break

18. Dumping Waves Dumping or Plunging waves break with a tremendous force and can throw a swimmer to the bottom. They usually occur at low tide, when the sand banks are shallow and there is less water for the waves to break onto.
Surging Surging waves may never actually break as they approach the waters edge, as a result of the water being very deep beneath them. They do not lose speed or gain height.
Spilling Spilling waves occur when the crest (top) of the wave tumbles down the face (front) of the wave. As the tide gets lower and the sandbank on which the waves are breaking becomes shallower, this type of wave will form tunnels or 'tubes'.

19. Rip Currents

20. One desperately needs the other!
Precision vs Accuracy
Precision refers to the degree of specified detail which can be observed or closeness of repeated measurements to each other.
Accuracy refers to the truthfulness, or correctness, of the specified data or the closeness of a measured or derived data value to its true value.
For instance a balance with a fault can give bias could give precise (ie very repeatable) but inaccurate (ie untrue) results.
One desperately needs the other!

22. Beach Surveys
Most common method for drawing the cross section of a beach utilizes a surveyor’s level and leveling rod
Vertical elevations are often referenced to the NGVD (National Geodetic Vertical Datum)
Based on mean sea level in 1926 at 26 tidal benchmarks along 3 US coats

24. Take Home Concepts Lots of ways to approach a problem
Choosing the right tool for the job
Instruments
Data Sheet design
Build in QA/QC
Normalization of data
Volunteer programs – helpful or hassel?
Precision vs Accuracy

25. notes
Calculate power of longshore transport (given equations and constants but must know what goes where and how to solve)
Wave anatomy and how it changes with changing parameters
Accuracy and precision