Coastal Environmental Geology
Environmental Issues and Coastal Geology
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Excessive Sedimentation
Shoreline Erosion
Coastal Subsidence
Sea Level Rise
Storm Surges
Tsunamis
Wave Motions
• Particles in a wave travel circular paths
• The water in a deep-water wave does not
move forward
• Below wave base, wave effects are negligible
Wave Motions
Wave Fetch
Wave Fetch
The Highest Recorded Ocean Wave
When Waves Meet the Shore
When the bottom interferes with wave
motion, the wave steepens and the top
overtakes the bottom.
Wave Refraction
• Waves change path when they reach shallow
water
• Wave energy is concentrated on headlands and
spread out in bays
Rips
• When waves break parallel to a beach, rips
occur
Rips, Lake Superior
Excessive Sedimentation
Natural Sedimentation
• Rarely an issue; Nobody complains about too
much beach
• Siltation of harbors and channels
– Ephesus, Turkey
– Bruges, Belgium
Artificial Sedimentation
• Smothering of Marine Communities and
Wetlands
Ephesus, Turkey
Shoreline Retreat
Shoreline Erosion
• Sediment Starvation
Coastal Subsidence
• Compaction
• Sediment Starvation
Sea Level Rise
• Thermal Expansion
• Glacial Melting
Shoreline Retreat, Wisconsin
Beach Erosion, Surfside, Texas
Beach Erosion, Surfside, Texas
Beach Erosion, Surfside, Texas
In the long run, nothing is as
futile as trying to resist shoreline
change.
Change can be resisted for a while,
but when the water wants
something badly enough, it will
come in and take it.
Property
Values and
Shoreline
Erosion
• If more than half the original lot is left, it’s
Location, Location, Location
• After that, it becomes obvious there soon
won’t be any location left
Longshore
and Beach
Drift
• Most Beach Sand Is Created by Weathering and
Carried to Coasts by Rivers
• Beach Sand Moves along the Coast by Longshore
and Beach Drift
Longshore and Beach Drift
Beach Drift, New Jersey
Catastrophic Waves
Storm Surges
• Galveston 1900 (6000-8000 dead)
• Bangladesh 1970 (300,000 dead)
• Bangladesh 1991 (140,000 dead)
– Operation Sea Angel
• Katrina 2005 (1700 dead)
• Myanmar 2008 (200,000 dead)
Tsunamis
• Indian Ocean 2004 (250,000 dead)
Bangladesh
Annual
Flooding
Bangladesh
Cyclone
Hazard
Hurricane
Evacuation
Marker
Storm Waves: Galveston, Texas, September 8, 1900:
• 6000-8000 dead
• 3600 houses destroyed
Raising Galveston – 6 in. to 17 ft.
“A rickety maze such as Dr. Seuss might have drawn”
The Lift in Progress
Pumping in
the Sand
The Galveston Seawall
Seawall, Galveston, Texas
Seawall, Galveston, Texas
Centennial
Monument
Seawall Model, Galveston, Texas
Raised Hotel, Galveston, Texas
Seawall Buffer, Galveston, Texas
Seawall, Galveston, Texas
Behind the Seawall
Beach Growth, Galveston, Texas
Any Port in a Storm?
Cemetery, Galveston
Monument
to 1900
Hurricane
Monument
to 1900
Hurricane
The Decline of Galveston
• In 1900, Houston and Galveston were
comparable in size
• It took years for Galveston to recover
• The East Texas oil boom happened during the
recovery and bypassed Galveston
• Business and shipping relocated to Houston
• Galveston 60,000
• Houston 1.6 million
Katrina, 2005
Coastal Wetland, Louisiana
Mississippi River Levee
Mississippi River Levee
Levee and French Quarter
New Orleans
Katrina Flooding
Katrina
Flooding
The Katrina Disaster
• Could have been much worse
– Storm weakened before landfall (5 to 3+)
– Eye passed east of New Orleans
– Many levees failed after peak of storm
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Predictable Disaster
Poor Individual Preparedness
Unrealistic Expectations
Media Sensationalism
Insufficient FEMA Authority
Coastal Subsidence in Louisiana
• Compaction of sediment
– Formerly offset by new sediment
– Interception of sediment by dams
– Delta buildup far offshore
– Atchafalaya diversion?
• Sea Level Rise
• Oil drilling?
Neglected Factors in Louisiana
• Atchafalaya sedimentation
– 6.5 km2 per year
– Channel dredging needed
– Concern over loss of wetlands
• Mississippi is long overdue to shift to the Atchafalaya
– Before locks, 1/3 of Mississippi being diverted
– Diversion will starve other areas of coast –
naturally
• No amount of sediment will raise New Orleans
North Sea Flood, 1953
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1835 fatalities in Netherlands
307 in Britain
28 in Belgium
230 at sea
Storm surge plus high tide
Up to 5.6 meters
European Windstorms
• Intense extra-tropical cyclonic storms
• Often hurricane force and above
• In 1990’s averaged insurance losses of
€1.4 billion per year ($2 billion).
• 1634 flood in Holland and Germany killed
8,000-15,000
European Windstorm
1953 North
Sea Flood
Holland is
Vulnerable
Flooding, 1953
Netherlands
Delta
Project
Netherlands Delta Project
Netherlands Delta Project
Flood Risk,
Britain
Thames Barrier
Thames Barrier
The Great Tsunami
December 26, 2004
Banda
Aceh
Waves Approaching Sri Lanka
Waves
Hitting Sri
Lanka
Wave
Height and
Travel Time