Coastal Environmental Geology

1
Coastal Environmental Geology
2
Environmental Issues and Coastal Geology

• Excessive Sedimentation
• Shoreline Erosion
• Coastal Subsidence
• Sea Level Rise
• Storm Surges
• Tsunamis

3
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

4
The Highest Recorded Ocean Wave
5
When Waves Meet the Shore

• When the bottom interferes with wave motion, the
  wave steepens and the top overtakes the bottom.

6
Wave Refraction

• Waves change path when they reach shallow water
• Wave energy is concentrated on headlands and
  spread out in bays

7
Rips

• When waves break parallel to a beach, rips occur

8
Rips, Lake Superior
9
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

10
Shoreline Retreat

• Shoreline Erosion
• Sediment Starvation
• Coastal Subsidence
• Compaction
• Sediment Starvation
• Sea Level Rise
• Thermal Expansion
• Glacial Melting

11
Shoreline Retreat, Wisconsin
12
Beach Erosion, Surfside, Texas
13
Beach Erosion, Surfside, Texas
14
Beach Erosion, Surfside, Texas
15
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.

16
Property Values and Shoreline Erosion

• If more than half the original lot is left, its
  Location, Location, Location
• After that, it becomes obvious there soon wont
  be any location left

17
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

18
Beach Drift
19
Beach Drift, New Jersey
20
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)

21
Bangladesh Annual Flooding
22
Bangladesh Cyclone Hazard
23
Hurricane Evacuation Marker
24
Storm Waves Galveston, Texas, September 8, 1900

• 6000-8000 dead
• 3600 houses destroyed

25
Raising Galveston 6 in. to 17 ft.
26
A rickety maze such as Dr. Seuss might have
drawn
27
The Lift in Progress
28
Pumping in the Sand
29
The Galveston Seawall
30
Seawall, Galveston, Texas
31
Seawall, Galveston, Texas
32
Centennial Monument
33
Seawall Model, Galveston, Texas
34
Raised Hotel, Galveston, Texas
35
Seawall Buffer, Galveston, Texas
36
Seawall, Galveston, Texas
37
Beach Growth, Galveston, Texas
38
Any Port in a Storm?
39
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

40
Katrina, 2005
41
Coastal Wetland, Louisiana
42
Mississippi River Levee
43
Mississippi River Levee
44
Levee and French Quarter
45
New Orleans
46
Katrina Flooding
47
Katrina Flooding
48
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

49
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?

50
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

51
The Great Tsunami

• December 26, 2004

52
(No Transcript)
53
Banda Aceh
54
(No Transcript)
55
Waves Approaching Sri Lanka
56
Waves Hitting Sri Lanka
57
Wave Height and Travel Time