Ch. 15.2: Coastal Dynamics

Longshore Drift


-How does longshore drift move material along the coastline?
    -longshore current is created by waves approaching the beach at an angle and the wind pushing the water onto the shore, which creates longshore drift.

"one of the most significant forces shaping the coast is longshore drift, which is the net transport of sediments along the coast by a longshore current."


Visuals/Vocab
    
     Longshore drift- transportation of sediments along the coast.
     Longshore current- waves approaching the beach at an angle, and the wind pushing the water up onto the shore.






Beach Dynamics


-Where does sand come from?
   - most sand comes from erosion.
-A beach is composed of what three sections?
   - foreshore, backshore,  low-tide terrace
-What factors affect the shape and appearance of a beach?
   - grain size of beach sediments, wave energy, degree of the beach slope.
-What is a coastal cell?
   -controls the accumulation and dispersion of sand.


"Longshore drift explains one of the major ways that sand moves along the coast."


Visuals/Vocab





Large scale sand features


-What causes a spit to form?
   - when a longshore current turns a beach corner into the relatively calm water of a bay
-What causes trombolos to form?
   - two spits grow together to form a tombolo
-Why are barrier islands temporary coastal features?
   - they are always gradually moving inland as the sea erodes the coast
-What five features make up a typical barrier island?
   -  1-Lagoon
      2-Salt marsh
      3-Barrier flat
      4-Dune
      5-Ocean beach
      6-Ocean
-What are differences between river dominated, tide dominated, and wave dominated deltas?
   - river dominated- strong rivers, mild tidal action, and mild wave action
   - tide dominated- strong tidal changes that commonly create sand ridges perpendicular to the shore
   - wave dominated- significant wave energy that redistributes river sediments

"A spit is a length of accumulated sand attached to land at one end, pointing in the direction of the longshore drift."


Visuals/Vocab


spit- A spit is a length of accumulated sand attached to land at one end, pointing in the direction of the longshore drift

tombolo- spits that extend between two islands to form an island to the mainland







True or False

1- a coastal cell controls the accumulation and dispersion of sand

2- a beach is composed of foreshore, midshore, and backshore

Fill in the blank


1- A __________ is a spits that extend between two islands to form an island to the mainland

2- Longshore drift is the ________ of sediments along the coast.

Multiple Choice

1- Whats one feature that makes up a typical barrier island?
    a.) Lagoon
    b.) Rift valley
    c.) Tombolos

2- What is one factor that affects the shape and appearance of a beach?
    a.) Amount of people on it
    b.) Wave Energy
    c.) Dunes

Current Research





Summary


Longshore drift is caused by longshore current. Longshore drift moves material along the coastline. most sand comes from erosion, and beaches are made up of three sections. Spits and tombolos are also formed by longshore currents. Barrier islands are temporary, and there are 5 features that make them up. Longshore current is a very important thing and longshore drift and spits/tombolos would not be possible without it.