Title: Coastal Hazards
1Coastal Hazards
- Chapter 9
- Melinda Balk Jennifer Lowney
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7Tsunami damage from 1946
8What if
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14Hurricane Andrew August 1992
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17Huge waves swamp this lighthouse at the entrance
to the harbor at Les Sables d'Olone (France) on
the Bay of Biscay on November 6, 2000.
18The French Storm
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20A couple watches huge waves break along Point
Lobos as a fierce winter storm bears down.
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22Surf pounds Peggotty Beach, Massachusetts
23Violent wave overtopping occurs when waves break
against sea walls in Great Britain.
Would you stand here?
24Scientists are compiling the first detailed map
of Britain's receding coastline. (2001)
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26Rapid coastal erosion caused by block failures at
Key Point, Yukon.
(July, 1987)
27Coastal flooding in Bangladesh
.In Texas
28Flood in China, 2002
Indonesian Flood, 2002
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35Most Serious Coastal Hazards
36Tropical cyclones
37Tropical Cyclones
- Typhoons in the Pacific
- Hurricanes in the Atlantic
- Wind speeds greater than 100 km/hr
- Wind blows in a large spiral around the eye (calm
center)
38Facts
- Between 8 degrees north and 15 degrees south of
the equator - Warm surface water temperatures
- US Hurricanes
- Begin as thunderstorms in Africa
- Move west and north and gain energy from warm
ocean waters
39Hurricane Info
- Storms that become hurricanes are monitored from
satellites and planes
- Hazards
- High Winds
- Flooding (causes the most damage for property and
people) - Storm Surges are major rises in ocean levels (10
meters)
40Flood Facts
- - Nine out of ten "Presidential Disaster
Declarations" - Flood waters move fast enough to roll boulders,
tear out trees, and - obliterate bridges
- Flooding has killed more than 10,000 people since
1900. Property - damage from flooding totals over 1 billion
each year in the United - States.
- -The average automobile can easily be swept away
in just two feet of water. - - Floods are most likely to occur in spring due
to snow melt and rains.
41What would happen if the ocean rose one meter?
- http//archive.abcnews.go.com/sections/us/global_c
oast1008/
42Never attempt this!
43Hurricane Andrew (1992)
- Costliest in US history
- Over 20 billion dollars in damage
- 250,000 homeless
- More than 100,000 buildings damaged, including
the hurricane center
44Costliest
45Deadliest
46Most Intense
47Waves
- Size depends on
- Velocity of the Wind
- (Greater the velocity, the greater the wave)
- Time period (duration) that wind blows
- Distance (fetch) that the wind blows across the
water. (The longer the fetch, the greater the
wave)
- Wave form
- Wave height (difference in height between the low
and the high) - Wave length (distance between successive peaks)
- Wave period (time in seconds between successive
waves to pass a point)
48Swells
- The wave groups generated by storms far at sea.
- If we can predict the velocity and height of the
waves, we can estimate when waves with a
particular erosive ability can strike the
shoreline. - When waves enter shallow water, wave period
remains constant, wave length and velocity
decrease and height increases. - When water depth wave height, waves break
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50Tsunamis
- What causes a tsunami?
- Usually the result of a sudden rise or fall of a
section of the earth's crust under or near the
ocean. - Tsunami waves can also be created by volcanic
activity and landslides occurring above or below
the sea surface.
51Tsunami Waves
- When these waves approach shore, the speed of the
wave decreases as they begin to "feel" the
bottom. It is at this time that the height of
the wave drastically increases. As the waves
strike shore they may inundate low-lying coastal
areas resulting in mass destruction and in many
instances loss of life.
52Beach Composition Formation
- Loose material like sand or gravel
- Accumulates by wave action at the shoreline
- Made from shells, coral, volcanic rock (depends
on the geography)
- Various areas of beach (top down)
- Berms
- Beach face
- Swash zone
- Surf zone
- Breaker zone
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54Littoral Transport of Beach
- Waves can cause drifting of sand and beach
materials
55Homes destroyed by coastal erosion
56How close should we build to the water?
(Rhode Island)
57Coastal Erosion
- Erosion and the Economy More than 100,000 state
residents and tens of thousands of out-of-state
tourists use Rhode Islands beaches each summer,
bringing millions of dollars in revenue.
58Coastal Erosion
- Property located along Rhode Islands coast
represents an enormous investment. It has been
estimated that if a 100-year storm had occurred
in 1989, losses of properties in the coastal
floodplain would have exceeded 280 million.
Losses would be even higher today, due to both
sea-level rise and to additional construction
since 1989.
59- Rhode Island's Changing Coast
- The majority of Rhode Islands south shore is
eroding over the long term, with an average
annual rate of retreat of 1 to 2 feet. - Exposed sandy shores can recede by as much as 30
feet in a single severe hurricane. - If sea level continues to rise by 1 foot per
centuryas is actually being measured at
Newportall of Rhode Islands low-lying coastal
areas (76 percent of the shoreline) could be
adversely affected.
60Coastal Erosion
- Natural, continuous process
- Predictable
- We spend lots of money trying to control it
- 75 of the US lives near the coast
- We have interfered with material flow of sand
from inland areas by building dams that trap sand - This causes beaches to be deprived of sediment
and erode
61Seacliff Erosion
- Result of natural processes
- Storms
- Cyclones
- Marine life that destroys rocks (mollusks)
- Weather (waves)
- Rain
- Human Activities
- Urbanization
- Recreation
62Controlling Erosion
- Cannot be completely controlled
- Natural process!
- Spend money
- Seawalls (reflect waves)
- Groin fields (trap sand)
- Breakwaters (break up large waves)
- Jetties (wave protection, prevents movement and
settling of sediments) - These control erosion of a coast but can
contribute to erosion of their immediate area
63Jetties
64Seawall
65Breakwaters
66Groins
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68Erosion Waterfall Formation
- http//earthsci.terc.edu/content/visualizations/es
1305/es1305page01.cfm?chapter_novisualization
69Human Activity Coastal Erosion
- Humans like to live near water
- Causes coastal disturbances
- Increases erosion rate
- Eventually, this can potentially cause millions
and billions in damage - Some do not see erosion as a problem
70In The Classroom
- As mentioned earlier, people that have their
property destroyed can have their homes rebuilt
in the same location. Should we continue to
allow this? - Debate the benefits and consequences of using
engineering structures to decrease the rate of
erosion. Should we use more natural means?
71Classroom Extension
- Fieldtrip to a beach
- Examine beach composition
- Vegetation surround the beach
- Other structures present that influence erosion
rates - Human factors local developments, recreation,
etc.
72Interdisciplinary
- Math Estimate the impact of waves on a local
shore by using wave velocity, height, and
distance between waves - English Write a letter to a local government
official explaining your opinion on the
conditions of local beaches and what should be
done to preserve them. - Art Make observations and inferences of an area
and draw a picture showing the same area after it
has experienced a severe coastal hazard.
73Final Thought
- How do you make people consider erosion (a
problem that is constantly occurring) as a
serious coastal threat when there are more
immediate and devastating coastal hazards?