Coastal Environmental Geology

choppedspleenMechanics

Feb 22, 2014 (3 years and 1 month ago)

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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 Sedimentation

Natural 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 Waves

Storm 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 km
2

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