Transcript Shorelines and Shoreline Processes Chapter 20

Shorelines and Shoreline Processes
Chapter 20
•
The legend lives on from the
Chippewa on down
Of the big lake they called
'Gitche Gumee'
The lake, it is said, never gives
up her dead
When the skies of November
turn gloomy
With a load of iron ore twentysix thousand tons more
Than the Edmund Fitzgerald
weighed empty.
That good ship and true was a
bone to be chewed
When the gales of November
came early.
•
The ship was the pride of the
American side
Coming back from some mill in
Wisconsin
As the big freighters go, it was
bigger than most
With a crew and good captain
well seasoned
Concluding some terms with a
couple of steel firms
When they left fully loaded for
Cleveland
And later that night when the
ship's bell rang
Could it be the north wind
they'd been feelin'? © 1976
Moose Music, Inc.
Factors of controlling Shoreline
Evolution
•
•
•
•
•
•
Currents
Wind Driven Water Waves
Storm Surge
Sediment Supply
Nearshore Topography
Relative Elevation Change
– Emergent
– Neutral
– Submergent
Major Ocean Currents
Gulf and Atlantic Currents
• Currents redistribute
materials (generally
sand)
Wind Driven Currents in Lake
Michigan
Southerly Beach Drift, Florida
Coast
Wind Driven Water Waves
• Several empirical
equations relating the
variables to waves
produced!!!
– Fetch
– Wind Velocity
– Direction
• Constant
• Variable
– Duration
Wind Driven Water Waves
• Sea - where waves are
generated
• Waves of several
wavelengths and
amplitudes
• Waves moving in different
directions (veering winds)
• Wave cancellation and
addition
• Possible rogue waves
• Swell - beyond the sea
where waves are sorted
into a narrow spectrum
• Similar wavelengths and
amplitudes
• Every third or fourth wave
5 to 10% larger
Track of Lows November 8-10, 1975
Plot of Lows and Ships Plot,
November 10, 1975
Ship Observations Reported by Radio
Calculated Maximum Wave
Height in Open Ocean
Is this sea or swell?
el
l
50%
Sw
a
50%
Se
1. Sea
2. Swell
Wave-train in the Swell
no net transport in the water column
Prograde
Retrograde
Wave Base
Changes in the water column as
water shallows
Erosion of bottom sediment
Oblique Waves
Sand transport
oblique waves and beach drift
Return Current (Rip)
Wave Refraction and beach
transport
Pt. Reyes, California
Point Reyes, California
1890
1970
1910
1990
1920
Nye Beach, Newport, Oregon.