Wave Transformation

1
(No Transcript)
2
(No Transcript)
3
(No Transcript)
4
Project

• Compare Hurricane Isabel to 1933 August
  Hurricane storm surge and propensity for
  flooding
• What would sea level rise do to coastal
  vulnerabilty from the same storm in year 2100
• Changing wind fields during Isabel and wave
  propagation

5
Wave Transformation

• Basic Relationships
• L gT2/2p
• (L 1.56T2)
• C L/T
• (C 1.56T)
• Group wave celerity (Cg) Cn
• N 0.5 deep water
• N 1.0 very shallow water
• Group wave celerity ltindividual waves

6
Wave Energy

• E 1/8 ? g H2
• ? water density
• G acceleration due to gravity
• H wave height
• Wave Power P Ecn
• C (gh)½
• H water depth

7
Shallow Water

• As the wave shoals, the wave period no longer is
  important as determinant of wave celerity, rather
  depth
• Because E must remain constant, and Celerity (Cn)
  decreases, wave height (h) has to increase
• Moreover, as wave period is constant, wavelength
  has to decrease

8
Refraction of Shoaling Waves

• Waves bend around obstacles as they try to remain
  parallel to depth contours
• Sin a (C/C0) sin a0
• ? angle between wave crest and depth contour
• C wave celerity
• Subscripts are deep water values for these
  variables
• Wave height and energy changes with refraction
• P ECnS
• The spacing between the rays increases with
  refraction, and in shallow water energy must
  decrease

9
Breaking Waves

• Point of breaking function
• ? Hb/h0
• Numerator at wave break point
• 1.2 for steep beaches, 0.6 for flat beaches
• Low waves will break closer in shore

10
Swash and Backswash

• Swash the uprush of water after the wave breaks
• Depends on wave conditions
• Rs 0.7 H0
• H0 deep water wave height
• Permeability of the beach coarse sand vs. fine
  sand
• Backswash return of water after swash runup
• On gravel beaches there is none