Sediment Study - Lesson Plan

Lesson Plan
Day 1: Experimentation

  1. Before leaving the classroom, introduce the project by posing the following questions to students:
  2. How are sediments distributed along a river or creek?
  3. Does it vary by location (the source, mid-stream, and the mouth)?
  4. Does it vary by the velocity of the current?
  5. What other factors might affect the distribution of sediments and why?
  6. On the front board, create a list of factors that students believe would affect the distribution of sediments.
  7. Tell students that they will be analyzing sediment samples from different parts of the creek in the school’s watershed. They will be making observations of the sediments at different places along the creek and will be looking for the reasons that sediments have been deposited in those ways.
  8. Point out the 3 sediment study sites on the topographic map of the creek. Assuming you will be studying the creek in the school’s watershed, students should already be very familiar with this map from the Topo Tour lesson. Ask students to point out the geographical differences between the 3 sites. Which site is at the highest elevation? Which site is steepest? Is any in a valley, on a flat plain, on a hillside, etc?
  9. Have students open their lab notebooks and set up a new page with the title of the study, the date, etc. Have students write down the question: “How are sediments distributed along the creek in our watershed? If the sediments are different from place to place, what causes the variability?”
  10. Have students make hypotheses about what to expect. I find that if you give students fill-in-the-blank style statements, I get much better hypotheses than if they are just told to make some predictions about what they might expect at each of the study sites and explain why. I used the following fill-in-the-blank style statements:
    • I think ______ are the most important factors that influence the way sediments are distributed along a creek.
    • At the first study site near the source I would expect to find _______, because ______.
    • At the second study site mid-stream I would expect to find _______, because ______.
    • At the third study site near the mouth I would expect to find _______, because ______.
  11. If you are dividing Day 1 into 2 class periods, stop here and continue the following day with Step 7.
  12. When students finish writing down their hypotheses, distribute the Sediment Study Directions and describe the experiment procedures that will be completed at the creek. Tell students what teams they will be working with and how to find a study site (you can assign them there or they may find their own site). Show them how to stake out their survey site with the string and stakes.
  13. Depart for the trip.
  14. When you arrive, make sure that each team has an appropriate survey site and a creek kit. Make sure that groups are setting up their string and stakes correctly.
  15. Allow students to get started immediately collecting the information in their lab notebooks. Circulate among groups to help students who have questions.
  16. Teams that finish early can sit quietly with a field guide and try to identify the plants and animals they found.
  17. When all groups are finished, return to the classroom.

Day 2: Soil Separation Tests

  1. Tell students to get out their soil samples. Tell them to set up a soil separation test with the sediment collected at their site, making sure to label each container with their team name, the sample number, and the location where it was collected.

Day 3: Data Analysis and Summary

  1. Allow students 10-15 minutes to interpret soil separation tests and clean up those stations. For each sample, they should draw a picture of the separation test in their lab notebook, labeling each layer with what the layer is made of (gravel, sand, silt or organic material) and the height of that layer in millimeters.
  2. Have students create a table like the one below in their lab notebook:
       Line 1 Line 2 Line 3  Line 4  Line 5  Average Percent 
    Organic material              
  3. Show students how to use this table to average the results from their 5 sediment samples and then turn the average heights into a percent.
  4. This information, along with the other data can be entered on the Data Summary Sheets and posted below one of the 3 site headings around the room.

Day 4: Drawing Conclusions

  1. Remind students of the questions posed at the beginning of this activity. Allow them to spend a moment rereading the hypotheses they made at the beginning of the project.
  2. The remainder of this class period will vary according to the data your students collected and the conclusions that may be drawn from this data. The general idea is to have the students devise a way to summarize the data collected at each of the study sites and then look for patterns. I spent 20-30 minutes  simply creating tables and charts with my students – tables of width and depth measurements, tables of current speed, tables of sediment composition, bar graphs for the more interesting types of data. I found that starting by comparing the width and depth measurements enabled students to imagine what each of the areas looked like – a pond, a small stream, a wide channel. Adding the current velocity information confirmed their suspicions of how quickly the water moved at each site. Finally, once they have had experience averaging the previous data, the most complicated task of interpreting the sediment composition data is more accessible than if we had tackled that first, even though that is the whole point of the exercise. Some issues that are interesting to explore:
    • Was there variability within the 5 sediment samples collected by a single team? Why is it important to collect 5 samples instead of just 1?
    • Was there variability among the data collected by the different teams at a single study site along the creek? What might have caused those differences?
    • What patterns in sediment distribution were found at each of the 3 study sites?
    • What factors (width, depth, current velocity, others) may have caused the variation in sediment distribution? Why do you feel this factor is important?