Education > Classroom

WebQuest: Saltwater Diversion and Outfall Management

Introduction: In order to understand the challenges presented within Louisiana wetlands, it is important to study saltwater intrusion in freshwater marshes. To investigate this phenomenon, follow the links below to answer the research questions. At the end of the study, you will be able to identify causes of wetland loss and discuss options for hydrologic restoration in vulnerable areas.

Watch the following video:

  1. Explain how humans have directly impacted Louisiana water throughout history.
    • Which of the behaviors are still occurring today?
  2. Pause the video at 1:10.
    • Predict the effects of saltwater intrusion on marsh habitats.
    • Then, watch the video through 1:45 to determine if your prediction was accurate.
  3. What is the major cause of wetland loss?
  4. The video mentions that the freshwater marshes support diverse plant populations. Why do you think diversity in plants is important?
    • After watching the video through 2:47, check your understanding of the role of marsh plants.
  5. You may have heard the term coastal erosion before. How does the information in the video change or support your idea of it?
  6. Now that you have witnessed the outcome of saltwater intrusion, how could these effects impact biodiversity within the ecosystem?
  7. Create a collage of images from approved sources to represent organisms that could be impacted by saltwater intrusion. This collage should include plants and animals. Share your collage with your group and discuss five interesting facts you learned about these organisms. Within your groups, decide your level of success based on the rubric below:
    • If you added 5 (total) correct plants and animals to your collage, you will be named a Wetlands Enthusiast.
    • If you added 7 (total) correct plants and animals to your collage, you will be named a Wetlands Researcher.
    • If you added 10 (total) correct plants and animals to your collage, you will be named a Wetlands Expert.

  8. Pause the video at 3:51
  9. The next section of the video will discuss the process of Hydrologic Restoration. Use the root words in this term to anticipate what the process will entail. After making a prediction, play the video and check your answer.
  10. Define hydrology using other resources.
    • How does the definition of this term relate to wetlands?
  11. The video discusses the importance of wetlands remaining at their optimum salinity and water levels. To help you understand what that means, read the following excerpt from Salinity Stress and Tolerance

    Saltwater intrusion makes fresh bodies of water more saline than they usually are. The problem with this is that the plants that live in such places are adapted to live in freshwater and generally cannot deal with increases in salinity more than 1 or 2 parts per thousand (ppt). For reference, the Gulf of Mexico’s average salinity is approximately 36ppt.

  12. The following image illustrates how salinity naturally changes across marsh regions

    Salinity Graphic
    Sidenote information: This is a good time to stop and talk with your teacher about why salinity fluctuations are impactful.
    Osmosis is the movement of water from a region of lower concentration of solutes to a region of higher concentration of solutes. Therefore, if a plant is accustomed to growing in a region of low salinity, it cannot quickly adapt to the loss of water that will occur if its environment is suddenly flooded with saltwater. This phenomenon can happen on a large scale if the wetlands aren’t properly maintained.
    Photo of ghost forest
    A ghost forest in tidal freshwater forested wetlands of the Sampit River, South Carolina.
    (Courtesy: Dr. William Conner, Clemson University)

  13. Once you have explored the importance of stable salinity levels, continue with the video. Study the hydrologic restoration techniques that are discussed. Take notes about those techniques below. You will use this information in the engineering challenge that follows.
  14. The video mentions that engineering technology continues to increase which can aid in identification and construction of functional hydrologic restoration systems. CWPRRA wants to challenge you and your team to explore the engineering technology necessary to protect fragile wetlands. To do that, you are asked to design and construct a unique way of managing water levels and salinity to protect marshes. To get started, get your thinking caps on and dig into the following real-life project.

    CWPPRA Fresh Water Bayou Marsh Creation

    Background Information: This area was damaged by Hurricanes Rita, Gustav, and Ike. Currently, Freshwater Bayou threatens to breach into the large interior open water and establish a hydrologic connection that previously did not exist. This would increase the environmental problems affecting marshes in this area. Additionally, interior marsh loss has increased and organic soils are being exported into Freshwater Bayou. Interior marsh loss will increase without construction of the proposed project.

    • Discuss the first paragraph with your project partner(s). What is the problem here?
    • Why is this a challenge for the ecosystem?
    • This region is located in Vermilion Parish, Louisiana. Locate this area on a map.
      • List three cities/towns in this parish.
      • Locate the waterways in this parish. Be sure to make note of regions that would be freshwater and regions that are made of saltwater.
      • Sketch the marsh areas and the interconnected waterways for use in the engineering challenge.

    Restoration Plan: The original project goals in this region include:
    1. creating/nourishing marsh and associated edge habitat for aquatic species through pipeline sediment delivery via dedicated dredging from the Gulf of Mexico or beneficial use of maintenance dredging from the Freshwater Bayou Canal;
    2. restoring a wetland buffer between the large open water areas in the Mermentau Basin and Freshwater Bayou. Project features include creating and/or nourishing approximately 401 acres of marsh using dredge material.
    • Discuss the project goals with your group.
      • What specific actions are being taken to encourage a healthy marsh habitat?
      • Your group should clarify your understanding with your teacher.
    • Refer to the map of this area to locate where these actions will be done.

    Engineering Challenge:
    1. After learning about ongoing restoration efforts, work with your group to design a tangible solution to the loss of marsh near Freshwater Bayou. To get started, your group should identify some of the many challenges present. Then, work to propose possible solutions.
      • This brainstorming process should include a plan for continued management of the region.
      • For an engineering bonus: The technique used should consider the amount of sediment that must be managed and the flow of water and materials required.
      You may want to refer back to the video about hydrologic restoration to review ideas. Additionally, here are other references for you to further explore:
      • Hydrologic Restoration Matures as a Component in Many CWPPRA Projects:

    2. Models are often used in science to solve problems on a small scale before large-scale construction begins. Models are important since they highlight areas where improvements need to be made, and they often save project money since solutions can be identified more easily.

      As a part of the team to remedy the Freshwater Bayou concerns, you and your partners are now asked to build your original design that aids in hydrologic restoration. Although models can be in the form of computer simulations, 3-D construction, blueprint designs, and other formats, you will model the Freshwater Bayou region with a computer simulation or a 3D model.

      Minecraft: Using the game Minecraft, construct the Freshwater Bayou area. It is important that you include marsh areas, waterways, and saltwater regions. Although Minecraft does not differentiate between saltwater and freshwater areas, you can use signs (or a key - if you’re up for the challenge) throughout the world to identify the areas. To make it more realistic, put flowing water where it would be naturally.

      Then, using your original design, build a model of your engineering solution. The model should contain detailed construction that would aid in marsh restoration. If you are a Minecraft expert, make the design functional. Keep in mind that you can use redstones, pressure plates, and other unique solutions to make your idea come to life.

      3-D construction: You are asked to use common household materials to construct your restoration tool(s). These materials may include recyclable materials such as empty paper towel rolls, cardboard boxes, empty water bottles, etc. Other materials for consideration may include: string, wooden craft sticks, plastic bins, aluminium foil, and modeling clay.

      First, it is important for you to set up a model of the Freshwater Bayou area. This can be done with Play-doh, modeling clay, water in containers, or other creative materials.

      Upon completion of the area, use the household materials to construct a functional model of your group’s engineering design for hydrologic restoration of Freshwater Bayou.

    3. Conclusion: Upon completion of your construction, present your groups’ ideas to the rest of the class. Offer explanations for your design and construction. Include descriptions of how your design will manage saltwater intrusion, encourage marsh diversity, and mitigate anthropogenic impact. Ask your audience to provide feedback to your discussion.

About This Site

The Louisiana Coastal Wetlands Planning Protection and Restoration Act Program web site contains information and links relating to coastal restoration projects in coastal Louisiana. This site is funded by CWPPRA and is maintained by the USGS National Wetlands Research Center.