Cracking dams intro

Webquest

for the Advanced level
groups of 3
on gravity dams



[quest] [tasks] [roles] [process] [worksheet] [conclusion] [for the teacher]


Quest(ion)

The government engineers have learned that the Narrows Dam on the Little Missouri River has two problems: the dam is cracked in two places and it has caused a decrease in the number of salmon in the river. He heard that your group is researching dams and asks your help: should he repair the dam or decommission (*) it?


Tasks

  • Assign each member of the group a role. Each person has the responsibility to lead the parts of the process listed under their role.

  • Follow the process below.

  • Answer the questions on your worksheet as you proceed.

  • Post messages on the bulletin board as directed, particularly to state your group's position on the dam repair or decommissioning at the end of the quest.

    •

    Roles

    Each of these roles are civil engineers who work for different organizations. You have come together to make a decision on whether the Narrows Dam on the Little Missouri should be repaired or decommissioned. Each person should lead the parts of the process listed for their role.
  • The US Bureau of Reclamation Engineer, concerned with the forces on the dam and the cracking. Take charge of the simulation.
  • The US Army Corp Engineer, concerned with the balance of service provided by the dam and the ecological impact of the dam. Take charge of research on both the services and the environmental impacts.
  • Association of State Dam Safety Officials Engineer, concerned with the repair and possible loss of life impact of the dam. Take charge of the review of case histories and loss of life estimations.

    • Process

    Bookmark the Webquest. You should return to this Process at the beginning of each step. Assign roles.

    1. The government has told you that there are problems with the Narrows Dam, so you need to gather some basic information about that dam, which is on the Little Missouri River. Look up the Narrows Dam in the National Inventory of Dams (#). Fill in your worksheet about this dam.

    2. Next, you must consider what services the dam is providing and how important these are. Go to the Dams section and read about the societal nature of dams. Fill in your worksheet about the services dams provide.

    3. Next you must consider the environmental impact the Narrows Dam is having on the number of salmon in the river. Read through the section on Opposition to dams to see what is being done currently to improve dams' effects on fish. Answer the questions on your worksheet.

    4. Go to the section on gravity dams to begin gathering the tools to perform a simulation. There are three tools you will find in this section. Follow your worksheet once you have moved to the dams section.

    5. Go to the section on Cracks. Here you will learn about the final two tools you need to do a computer simulation of cracking in a dam. Follow your worksheet.

    6. Go to the Simulation section. Review the steps of performing a simulation and then proceed to the simulation applet on the next page. Perform a simulation of what you have sketched on your worksheet. Be sure to watch the movies on how to perform each step.

    7. Post a message on the bulletin board under the heading "Simulation Results" about the results of your simulation -- did the cracks grow? Also post a message under "Using Simulations" about why computer simulations might be helpful.

    8. Find the population of the city nearest to the dam using the U.S. Census Bureau (#) database. Use this in the loss of life estimation for a dam failure. Try the different combinations on the worksheet and fill in your results. Post a message on the bulletin board under the heading "Loss of life scenarios" on what else you would want to take into account for determining the loss of life and impact of dam failure.

    9. Now you must think about the cause of cracking. The government has told you that the dam is subjected to intense solar radiation. Review of the Fontana Dam case history will help you figure out if this is a cause of cracking and what can be done to repair it. Fill in the answers to questions on your worksheet for this step.

    10. Considering the services, cracking, and ecological impacts, do you think the dam should be repaired or decommissioned? Write out your decision and then post your statement to the government engineers on the bulletin board under the heading "Social and Ecological Impacts of Dams."

    Worksheet

    The worksheet is here and should be printed out and filled in as you go along.


    Conclusion

    Whatever your group's decision, you probably helped save lives and save the environment. The South Fork Dam in Johnstown, PA actually did kill over 2000 people and the Lower Snake River dams have seriously contributed to the endangerment of several fish species. You can see how much of an impact dams have on society. You learned how to work together, as engineers, to solve a problem and make a decision. This involved lots of research and some technical work, with a healthy consciousness for safety and the environment. You can show the engineers how to do their jobs now!


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