coastal regions and land loss chapter 10. morris island lighthouse, sc
Post on 19-Dec-2015
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TRANSCRIPT
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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 margins Population 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. 1.Wind speed 2. 2.Duration 3. 3.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 conditions Emergent 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 surges Changing 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 type low coastlines most affected
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- Minimizing coastal hazards Hard stabilization Seawalls: concrete, large blocks Cause more problems than they solve; they enhance beach erosion
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- n n Groins : built perpendicular to shoreline n n Problem is the area down drift from groin is not fully replenished n 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 offshore Temporary solution due to dynamics Must be repeated
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- Managed retreat solution Prevent building Relocate threatened buildings
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- Miami Beach, FL 24 million cubic yards over 10 years Before beach nourishmentAfter beach nourishment
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- Cape Hatteras lighthouse Built 500 m from waterLater moved 850 m inland