Coastal Processes and Tides


Coastal Processes Topic outline:

A. Wave action

  1. Wave refraction
  2. Longshore current
  3. Longshore drift (transport)
  4. Littoral cells (beach compartments)

B. Coastline classifications and features

  1. Erosional – wave-cut bench, marine terrace, sea cave, stack, arch
  2. Depositional – delta, spit, tombolo, barrier islands

C. Human influence on coastal processes

  1. groins, breakwaters, and jetties


Tides Topic outline:

A. Equilibrium theory of tides

  1. Gravitational force
  2. Daily recurrence of tides – tidal bulges
    1.  Lunar day
  3. Solar bulges
  4. Monthly tidal cycle
    1. Neap tide
    2. Spring tide
  5. Other factors
    1. Declination of sun and moon

B. Dynamic theory of tides

  1. Shape of ocean basin - amphidromic point
  2. Tidal patterns
    1. Tidal datum - mean sea – MLLW - MLW


Interesting places to visit:

Great photos of America's coastlines:


Clear explanation of tidal bulges:


Tides charts for U.S.:


Tidal animation:


When you are finished with this topic, you should be able to answer the following questions:

  1. Distinguish between a summertime and wintertime beach.  Why do these differences occur?
  2. How are longshore currents formed?  How is longshore drift (transport) related to longshore current?
  3. Distinguish between groins, jetties, and breakwaters.
  4. What are some coastal features associated with erosional coastlines? With depositional coastlines?
  5. What are the parts of a beach compartment (littoral cell)?
  6. Why is a lunar day 24 hours and 50 minutes long, while a solar day is only 24 hours long?
  7. What causes the recurrence of high and low tides at a given location each day?
  8. How are the tidal bulges on each side of the earth generated?
  9. What causes the differences between neap and spring tides and what are those differences?