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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