Coastal Environmental Geology. Environmental Issues and Coastal Geology Excessive Sedimentation...
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Transcript of Coastal Environmental Geology. Environmental Issues and Coastal Geology Excessive Sedimentation...
Coastal Environmental Geology
Environmental Issues and Coastal Geology
• 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
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 SedimentationNatural Sedimentation
• Rarely an issue; Nobody complains about too much beach
• Siltation of harbors and channels
Artificial Sedimentation
• Smothering of Marine Communities and Wetlands
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
Beach Drift
Beach Drift, New Jersey
Catastrophic WavesStorm Surges
• Galveston 1900 (6000-8000 dead)
• Bangladesh 1970 (300,000 dead)
• Bangladesh 1991 (140,000 dead)– Operation Sea Angel
• Katrina 2005 (1300 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
Beach Growth, Galveston, Texas
Any Port in a Storm?
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
• 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
The Great Tsunami
December 26, 2004
Banda Aceh
Waves Approaching Sri Lanka
Waves Hitting Sri
Lanka
Wave Height and
Travel Time