coastal regions and land loss
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Coastal Regions and Land Loss. Chapter 10. Morris Island Lighthouse, SC. Coastlines. Active vs. passive margins Population concentration Seven of 20 largest US cities on or near coastline 53% US population lives in coastal counties. Deep-water wave form (water depth > 0.5L). - PowerPoint PPT PresentationTRANSCRIPT
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Coastal Regions and Land Loss
Chapter 10
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Morris Island Lighthouse, SC
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Coastlines
Active vs. passive marginsPopulation concentration
• Seven of 20 largest US cities on or near coastline
• 53% US population lives in coastal counties
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Deep-water wave form (water depth > 0.5L)
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Factors controlling waves
1. Wind speed2. Duration3. Fetch
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Plunging breakers
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Spilling breakers
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Coastal erosion along beach at Santa Barbara, CA
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Longshore drift and transport
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Sea level changes
Eustatic sea level rise caused by• Changes in amount of water in oceans
Short-term• Changes in shapes and volumes of oceans
Very long term Related to sea floor spreading
Climate is major control• Thermal expansion or contraction of water
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Shoreline conditionsEmergent
• Earthquakes and uplift/downdrop• Glacial rebound• Area: New England
Submergent• Higher sea level• Irregular shorelines common• Area: Mid-Atlantic area – Chesapeake Bay
(VA)
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Very short-term changes
Storm surgesChanging tides
• Extreme: Bay of Fundy, eastern Canada• 15 m tidal range twice daily
• Normal daily changes (2 high, 2 low)
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Coastal erosion rates
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Note changes based on shoreline typelow coastlines most affected
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Minimizing coastal hazards
Hard stabilizationSeawalls: concrete, large blocks
Cause more problems than they solve; they enhance beach erosion
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n Groins: built perpendicular to shoreline
n Problem is the area down drift from groin is not fully replenished
n Fix by beach nourishment
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Chesil Beach on southern coast of England
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Breakwaters
Built to protect shoreline by intercepting waves
Jetties
Usually pairs of protrusions
Note beach modifications
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Soft (beach) Stabilization
Moving sand around, usually from offshoreTemporary solution due to dynamicsMust be repeated
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Managed “retreat” solution
Prevent buildingRelocate threatened buildings
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Miami Beach, FL24 million cubic yards over 10 years
Before beach nourishment After beach nourishment
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Cape Hatteras lighthouse
Built 500 m from water Later moved 850 m inland