Waves on the Inner Shelf into Beaches:

1
Waves on the Inner Shelf into Beaches As
offshore waves approach the shore, they shoal,
refract, and then break.
2
As waves feel the seabed, Stokes Drift
occurs (function of the non-linearity of waves
in shallow water)
Orbit at wave crest slightly larger than orbit at
wave trough
Results in Mass Transport
3
Wave breaking Type of breaking is a function
of wave steepness beach slope
As the waves break they lose energy and diminish
in wave height.
4
Beach Characterization Dimensionless
ratio Iribarren Number As a storm approaches,
tend to go from reflective towards dissipative
5
Bedload transport on beaches (under waves) Models
are largely inherited from uni-directional
models. Two Examples Madsen (1971) and wave
power due to oblique waves Madsen reaffirmed the
Meyer-Peter Muller model under time-dependent
oscillating velocity
6
Factors that produce a net transport 1. Bottom
slope 2. Non-linear waves 3. Superimposed
currents Net transport arises from a small
difference between two large quantities.
7
Wave power due to oblique waves For larger grain
sizes (sediment that isnt going into
suspension), can use the power expended on the
seabed concept of Bagnolds. Instead of looking
at the energy flux through the boundary layer
- wave energy flux power/unit length of wave
crest (ECg)b where E 1/8 ?
gH2 All of this power must be expended within
the surf zone
8
Convert power to per unit length of shoreline -
cos ? in the longshore direction - sin
? Assumes all longshore current due to
obliqueness of waves no wave-current interaction