beaches

beaches extend from the low tide line landward across the unvegetated sediment to the beginning of permanent vegetation, or the next geomorphic feature (dune, rocky cliff, seawall, etc.)

parts of a beach area

• nearshore

• foreshore - also includes
• the swash zone
• ridge and runnel (swash bar)

• <>backshore - may include
• <>storm ridge 

• reflective beach
  

• dissipative beach

beach materials

nearly anything that can be transported by waves can form a beach, for example

• mud beach
  

• gravel beach

beach processes

waves and the currents they generate influence the sediment and the structure of beaches

• each crash of a wave suspends an amount of sediment directly proportional to the size of wave
  

• the sediment is then moved by currents; types of currents:
• combined flow current
• longshore currents
• rip currents 
• swash currents

beach cycles - sediment transport

• accretional beaches

• storm beaches

• erosion profile

• storm beach is a temporary condition

• pre-req is supply of sediment and wind
  

• coastal dunes are not restricted to barrier islands, although all barrier islands have at least small dunes

dune formation and distribution

sea breeze and land breeze

sand shadows

gravel lag

• obstructions


• bedrock cliffs
• vegetation
• existing dunes
• human construction
  

• dune ridge: linear arrangement of dunes, one dune wide; called the foredune ridge

dune dynamics

dunes are quite vulnerable to even the modest storm

rising sea levels exposes dunes to further erosion

wind can cause the migration of part or all of the dune

• blowover
• angle of repose
  

• migrate landward
  

barrier islands

barrier islands characterize much of the coasts along trailing edge coasts; they form as sediment accumulates by the combined action of waves and wave-generated longshore currents; protects the landward part of the coast against wave attack; include:

- barrier beaches
- barrier spits
- barrier reefs 

- barrier islands - focus in this chapter

barrier islands

• waved-dominated and mixed-energy depositional systems
  

• make up 12-15% of the Earth's outer coastline

•   relatively young: < 7000 years old

accepted theory of origination:  waves caused sediment to accumulate in an upward shoaling fashion that eventually led to a supertidal sandbar

barrier island components

• backbarrier
  

• washover fans
  

• lagoons
  

• tidal inlets
  

• tidal deltas
  

• <>ebb delta
• tide dominated
• wave dominated
  

• flood delta
• tide dominated

barrier island types

waves dominant: long and narrow
mixed wave-tide dominant: drum stick appearance; longshore current is interupted at an inlet and more sediment is deposited at mouth of inlet