Coastal Communities and Processes: Beach and Dunes

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Coastal Communities and Processes Beach and Dunes

• Introduction to Coastal Management

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Coastal Communities and Processes

• Beach and Dunes
• Shrub Thicket and Maritime Forest
• Freshwater Wetlands
• Tidal Marsh
• Estuarine Waters/Sand and Mud Flats

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Barrier Island transect from ocean to sound
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Beach, Dunes and Shrub Thicket
Cumberland Island, Georgia
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Dune Formation

• Elements required for dune formation

Sand
Wind
Object
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Dune Formation
Sand, moved by the process of saltation,
accumulates around objects including vegetation
and flotsam
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American Beachgrass (Ammophila breviligulata)
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Sea Oats (Uniola paniculata)
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Panic Grass (Panicum amarum)
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Saltmeadow Cordgrass (Spartina patens)
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Sea Elder (Iva imbricata)
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Primary Dunes

• Most seaward
• Unmodified dunes

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Secondary Dunes

• large landward dunes
• modified primary dunes

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Strand Line or Wrack Line

• Line of debris at spring tide
• Debris is called wrack
• Most dunes form here

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Strand Line or Wrack Line

• Large quantities of sand moved across strand
• Common on prograding (growing) beaches
• Rare on eroding beaches

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Dune Environments

• Youngest strand lines lie most seaward
• Multiple dune ridges form as strand lines are
  colonized

Oldest - - - - - - gt Youngest
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Dune Environments

• Dunes and colonizing plants grow in concert

Year 3
Year 2
Year1
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Dune Environmental Conditions

• Low soil nutrients (N and P)
• Desiccating winds
• Blowing sand

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Dune Environmental Conditions

• Air and soil temperatures are highly variable

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Dune Processes

• Unvegetated dunes migrate or move from lt1 m to
  gt15 m annually
• Migrating dunes engulf surroundings

? Natural revegetation a long term process
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Blowouts

• Occur when vegetation mantle is destroyed
• Difficult to stop, once started
• Creates environment called slack

blowout
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Natural and Man-induced Impacts on Dunes

• Oceanic overwash
• erosion

Washovers
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Natural and Man-induced Impacts on Dunes

• Off-road vehicle (ORV) traffic
• Sand fencing wooden, brush, trees

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Salt Aerosol Impact on Plants
Source of salt aerosol (ocean side)
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Source of Salt Aerosols
Salt Aerosols
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Salt Aerosol Impacts
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Salt Aerosol Impact on Plants

• Generally decreases from strand line, landward
• Highest on foredunes
• Lowest in slacks and lee of dunes

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Shrub Thicket Environments

• Early colonizers (survive low nutrients)
• Best examples are in dune slacks
• Reduced salt aerosol environment allows
  arborescent vegetation to flourish

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Wax Myrtle (Myrica pennsylvanica)

• Northern Bayberry is common in thickets from Cape
  Hatteras northward into New England
• Bayberry candles are made from the waxy coating
  on the berries

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Yaupon (Ilex vomitoria)