SCIENCE ACTIVITY
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Saving the Inlet

Purpose

To investigate beach erosion caused by longshore waves.

Materials

  • a paint tray (or other shallow rectangular container)
  • 500mL of moist “play” sand
  • 1L of water
  • one wave stick (a paint stir-stick works well)
  • one tongue depressor or craft stick
  • small pebbles or rocks

Lockwood's Folly Inlet dredging project.
  • a 10cm x 10cm piece of corrugated board
  • scissors
  • notebook
  • poster board or construction paper
  • pen, pencil, and markers for poster
The Story

Lockwood's Folly Inlet  was once the mouth of Lockwood's Folly River. Today the inlet separates two barrier islands:Oak Island and Holden Beach Isle.

Legand has it that the river and inlet got their names back in the 1600s when a man named Lockwood began building a boat on the bank of the river. After months of hard work, Lockwood finished his boat and pushed it into the river. The boat floated well but it floated too deep.  When he tried to sail into the Atlantic, Lockwood's boat ran aground on a sandbar at the mouth of the river. 

Lockwood tried and tried to free his boat but it was stuck so tightly in the sand that it could not be freed. He finally gave up and left his boat to rot in the sand. People soon began calling the boat "Lockwood's Folly" and according to the legand, that name became the name of the river and the inlet.

The same sandbar that snagged Lockwood's boat back almost 400 years ago would still be there today if it were not not for dredging . The sandbar forms when the longshore current carries sand from Oak Island and drops in the gap between Oak Island and Holden Beach Isle. Every few years, the current deposits enough sand in the inlet to clog it again.  Could there be a better way? Dredging is used to remove the sand and open the channel to boats.

Procedure

The Army Corps of Engineers has hired you and your partner to study how different structures can stop or slow the erosion that the longshore current causes.

STEP:

  1. Building a Beach    Create a model beach by spreading 500mL of wet play sand across the shallow/higher end of a paint tray. Make the beach straight and flat.
  2. Adding an Inlet     Split the beach into two parts by digging a trench in the sand that reaches the bottom of the paint trap.  This will represent the inlet. The inlet should be about 4 cm.
  3. Filling the Ocean    Add approximately 1L of water to the deep part of the tray where there is no sand. The water represents the ocean.  (Add just enough water to fill the inlet making sure that two beaches remain.) In your notebook, draw a diagram of your model.
  4. Making Waves    You and your partners should each take a turn creating waves in the ocean. Hold the wave stick vertically and use quick but short pushing motions to make a wave at an angle to the beach. Each of you will make 20 waves at the same angle. After everyone has had a turn, make a second diagram. Label any special features caused by the erosion. Compare the before-and-after diagrams and describe how the shape of the coastline has changed.
  5. Saving the Inlet     Brainstorm ways that you can use the rocks and/or tongue depressor (or craft stick) to keep your beach from eroding away and the inlet from filling. Seawalls, groins, jetties , and other barriers are used to prevent beach erosion. Decide on a strategy and test it by rebuilding your beaches and inlet then repeating the wave-making procedure described in Step 4. Again, try to make the waves at the same angle to the beach as before. Draw another set of before-and-after diagrams.

Conclusion:

 

You and your partners have been asked to present your results in the form of a poster. The poster will show the results of your experiments to protect an inlet from filling up with sand because of the eroding forces of waves hitting a beach at an angle. Your poster needs two pairs of before-and-after diagrams. The first pair will show the erosion caused by wave action without protection. The second pair of diagrams will show how well the protective feature you tested worked. Your poster needs a title, labels for all features shown, and a conclusion. Make sure that all words are spelled correctly and printed neatly; and the drawings are neat and clean.  (IMPORTANT: Identify which partner completed which item(s) on the poster.)

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The river name appears on a map from 1671, making Lockwood's Folly River one of the oldest named rivers in North Carolina.

Teachers may click here to see the Teachers Guide for this activity.


Copyright © 2010 Event-Based Science Project