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Activity: Coastal Engineering

NGSS Crosscutting Concepts:

Materials

  • Flat wave tank or large flat plastic bin
  • Water
  • Wind generating source (e.g., fan) or paddle or other object to displace water
  • Table 5.12
  • Sand
  • Toothpicks
  • Assortment of small rocks
  • Small building blocks or other waterproof objects to represent houses
  • Rosemary sprigs or other objects to represent vegetation
  • Ruler
  • Towels
  • Protractor (optional)
  • Metronome or other sound recording device (optional)
  • Camera (optional)
  • Computer program to analyze beach area on pictures (optional)

 

Procedure

Safety Note: If using an electrical device to generate waves, keep the device far away from the water. Promptly clean up splashes to prevent slipping. Consider doing the wave tank part of this activity outside if the weather permits.

 

A. The Scenario
Your group is a coastal management engineering firm. You are competing with the other groups in your class for a contract from a town called Seaside. Over the past few years, Seaside’s sandy beaches have been eroding. You must develop a plan to help the town manage its erosion problem. Your plan must include modifying the beach in some way to address immediate erosion concerns. Your plan must also include at least two policies that do not physically alter the shoreline, but instead regulate human behavior.

 

Each of the major stakeholders (groups of people with an interest in the issue of coastal erosion; Table 5.13) in town will vote on your idea. In order to win the contract, you must balance their competing interests. Your teacher may also give you additional criteria to consider, such as a specific budget or other feasibility constraints.

 

Table 5.13. Seaside stakeholder concerns
Business Owners: Seaside depends on its beaches to bring tourists who will spend money in Seaside. Business owners are concerned that erosion is keeping tourists away. The business owners want a management plan that will solve the erosion problem as soon as possible and cost as little as possible.
Recreational Users: Surfers and swimmers in town are concerned about the erosion problem and whether it will get worse as a result of global warming and sea level rise. They want a management plan that is aesthetically pleasing (looks nice, but does not have to be all-natural) and does not alter the water dynamics too much (so they can keep doing their normal activities like surfing and snorkeling).
Environmentalists: An environmental group wants to protect the habitat of an endangered intertidal crab that lives on one area of the beach. They would prefer that hard structures not be built on the beach. They want a management plan that preserves the crab habitat, maintains natural features, and prioritizes the long-term health of the beach.
Property Owners: There are some houses near the beach. As the beach is eroding, these houses are at risk. The owners who live in these houses want to build a seawall or other hard structure to save their properties and will pay for half of the cost themselves. They want a management plan that will solve the erosion problem immediately.

 

Have a class discussion to come up with the criteria for determining the effectiveness of your engineering plan on controlling beach erosion, a concern of all of the stakeholders. The following are some erosion criteria to consider. Come to a class consensus on which of these criteria you will measure and how you will measure it. You may come up with criteria that are not on this list.  

  1. The height of the coastline
  2. The width of the coastline
  3. The overall shape of the coastline
  4. The amount of sand pulled out to sea
  5. How far up the shore the waves reach

 

B. Set up standardized wave tanks

You will use a wave tank to develop and refine your coastal management strategies.

  1. (Optional) Wash the sand and rocks before the activity to remove fine particles that will make the water in your tank muddy.
     
  2. Fill the tank with water to about one-third full. The height of the water should be the same among all groups.
     
  3. Practice generating waves with a wind source or by displacing water using a paddle or other object. All groups should generate waves using the same method, they should have similar amplitudes and frequencies. Consider using a metronome to standardize wave frequency.
     
  4. Create a beach by carefully pouring sand into one end of the tank, so that a portion of the sand extends above the waterline. Standardize as many variables as possible, you may think of more than the following factors:
    1. The total amount of sand
    2. The height of the beach
    3. The width of the beach
    4. The location of the endangered crab habitat (mark with toothpicks)
    5. The number and location of the houses
       
  5. (Optional) Collect baseline data as a class in one of the tanks. This represents what will occur if nothing were done to the beach.
    1. Mark the shoreline with toothpicks.
    2. Sketch profile and top views of your coastline before generating waves.
    3. Measure things that correspond to your class beach erosion criteria (e.g., beach width)
    4. (Optional) Take “before” pictures of the wave tank and shoreline.
    5. Generate waves for 5 minutes. Try to keep the waves consistent in amplitude and frequency.
    6. Observe the wave patterns that are created. Make sketches of the wave patterns.
    7. At the end of the trial, draw profile and top views of the coastline. To observe changes in the shoreline, compare the location of the current waterline with the location of the toothpicks, which represents the location of the waterline at the beginning of the investigation.
    8. Measure things that correspond to your class beach erosion criteria (e.g., beach width)
    9. (Optional) Take “after” pictures of the wave tank and shoreline.

 

C. Develop Your Management Plan—Shoreline Modifications

  1. Choose a name for your coastal management engineering firm.
     
  2. In your group, discuss your ideas for managing Seaside’s erosion problems. You might consider multiple approaches in your plan to alter the shoreline. The following are some things you might consider:
    1. Building hard structures (some examples are in Table 5.12)
    2. b. Stabilizing the shore with “soft” non-structural techniques, for example, importing or shifting sand or planting vegetation
       
  3. Test your structural ideas in the wave tank following Part B Step 5. During this time while you are developing and improving solutions, you may choose not to follow all of the steps, or you may generate waves for less time than suggested.
     
  4. Collect final “before” and “after” data on your design plan by following all of the steps in Part B Step 5. The data you collect will be used in your presentation to stakeholders.
     
  5. When cleaning up, dry out the sand before storing it by spreading it out in a pan or on plastic tarps in the sun.
     
  6. Analyze and interpret your data.
    1. Compare your “before” and “after” data. How did the shoreline change? How much did it change?
    2. (Optional) Compare your “after” date to the “baseline” data collected in Part B. How did your plan compare to “doing nothing”?
    3. (Optional) If you took “before” and “after” pictures, analyze them to determine the difference in beach area (e.g., in cm2). 

 

D. Develop Your Management Plan—Policies

  1. Based on your wave tank results, and applying what you know about human behavior, suggest two policies for Seaside to consider as part of your management plan.
    1. If your wave tank results show a weakness in your design, policies may be added to prevent that weakness from becoming a problem (e.g., not building in a certain area).
    2. Policies can also be used to help enforce an aspect of your plan that might not be desirable to all of the stakeholders. However, remember that if your policies are unrealistic, none of the stakeholders will vote for your idea.
       
  2. The following are some policy ideas—be creative in coming up with your own!
    1. Relocating structures to areas further away from shore (managed retreat)
    2. Buying-back houses that are too close to the shoreline, destroying the houses and relocating the owners
    3. Setting construction set-back limits
    4. Placing signs on dunes to stop people from walking on them

 

E. Communicate your management plan

  1. Plan with your group how you will present your design solution, including your policy suggestions, to the stakeholders.
    1. You will be given a set amount of time (e.g., 5 min) to present your design.
    2. Decide how you will present your idea: wave tank demonstration, computer presentation, flyers, etc.
    3. You may want to share your before and after pictures and make charts with your data.
       
  2. Communicate your management plan to the Seaside stakeholders. Your teacher might represent all of the stakeholders, other adults or students might role-play a representative from each stakeholder group, or everyone in the class might each be assigned to a stakeholder group.
     
  3. (Optional) Prepare a written engineering design proposal. Use this opportunity to refine your ideas, taking into account any feedback from the stakeholders.

 

Activity Questions: 
  1. Evaluate your proposed solution compared to other groups.
    1. How were different group proposals similar? How were they unique?
    2. Which proposal do you think met each of the four stakeholder’s needs best? Why?
       
  2. What policies did people suggest that went over particularly well? What policies did people suggest that were met with resistance? Why?
     
  3. What were the limitations of your proposal?
     
  4. How well do you think the wave tank modeled engineering designs in the real world? How could the model be improved?
     
  5. Were there things you could have changed to improve your design?
     
  6. How do seawalls, breakwaters, jetties, and other hard structures affect sand transport? What are the negative aspects of these structural stabilization strategies?
     
  7. How do natural ways of stabilizing the shoreline, such as restoring native plant habitats, protect the coast?
     
  8. List at least five reasons why it is important for people to protect beach areas from erosion.
     
  9. Many people want to live as close to the water as possible. Based on your studies, what guidelines would you give a prospective homebuilder who wants to purchase or build near to the water?
     
  10. The accretion, or build-up of sand where it does not normally occur, can be as detrimental as sand erosion. List at least five reasons why it may be important to people to protect against sand accumulation.

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.