Classroom activity Grade 8 Engineering & Design
Model Check Dam for Quarry Hollow: A Design-and-Test Activity
A grade 8 build-and-test activity where teams construct a model check dam, measure how much simulated stormwater it holds back, and iterate for a second trial.
Objectives
- Students will build a model check dam from provided materials and test how much simulated storm water it holds back.
- Students will iterate their design at least once based on test data, applying the engineering practice of optimizing through repeated testing.
- Students will compare their design's performance to another team's design and identify a specific difference that affected performance.
Vocabulary
Key words: check dam, iteration, upstream, downstream, peak flow
Teacher overview
The fictional town of Quarry Hollow sits below a steep hillside, and heavy storms send fast-moving water across a footbridge downstream. In this build-and-test activity, teams of three or four students act as engineering consultants, building a small model check dam, a low barrier that slows moving water and holds part of it back, out of clay, gravel, and craft sticks inside a model stream channel. The model works the same way a real check dam does: a barrier that slows water and creates a temporary pool upstream reduces how much water arrives downstream all at once, and rebuilding and re-testing a dam after a first trial is the same test-and-optimize cycle a civil engineer uses when refining a real design.
Activity Directions
Setup (per team). Before class, an adult cuts away one short end of each foil pan so water can flow out, then folds the sharp cut edges over. Give each team the full materials list above. Explain that each team will build one check dam, test it with a simulated storm, then modify their design and test it a second time, keeping track of how much water their dam holds back in both trials.
- Prop the closed end of your pan up about 1 inch using the book or block, so water will flow downhill toward the open end. Mark a line about two-thirds of the way down the channel with a strip of tape and label it "footbridge line."
- Using only the clay, gravel, and craft sticks provided, build a check dam across the channel, upstream of the footbridge line.
- Press the base of your dam firmly into the pan and along both side walls, sealing any gaps where water could slip around rather than through your design.
- Set the pan so its open end reaches just past the edge of the table, and hold your downstream collection cup under the open end, past the footbridge line, to catch any water that gets through or around your dam.
- Measure exactly 300 mL of water into your pouring cup. This represents one simulated storm.
- At a steady rate over about 15 seconds, pour the 300 mL storm into the upstream end of the channel, above your dam.
- Wait 30 seconds after pouring stops for any remaining water to finish moving through or around the dam.
- Measure how much water collected in your downstream cup and record it on your data sheet as Trial 1.
- As a team, discuss one specific change you could make to your design (a different material arrangement, a taller dam, a different base seal) that might hold back more water.
- Modify or rebuild your dam based on that discussion, then repeat steps 5 through 8 for Trial 2, recording your results.
- Calculate how much water your dam held back in each trial (300 mL minus the amount collected downstream), and circle whichever trial performed better.
Ending condition. The building and testing portion ends once every team has completed two full trials and recorded both results on their data sheet. The activity then moves to a whole-class debrief.
Debrief. Bring the class together. Ask two or three teams to share their Trial 1 and Trial 2 held-back amounts and the specific change they made between trials. Then pose the debrief questions below for teams to discuss and answer in writing.
Student Handout
Data Recording Sheet
| Trial | Water poured (mL) | Water collected downstream (mL) | Water held back (mL) |
|---|---|---|---|
| 1 | 300 | ||
| 2 | 300 |
Design change made between Trial 1 and Trial 2: (record your design change here)
Debrief questions. After both trials, discuss these as a team and answer them in writing:
- What is the independent variable and what is the dependent variable in your two-trial test?
- Which of your two trials held back more water, and what was the difference in milliliters between the two trials?
- Why does pressing the base of the dam firmly into the pan and side walls matter when you are testing how well the design holds water back?
- Explain how a check dam changes the way the poured water reaches the footbridge line, and connect this to how real check dams reduce peak flow downstream during a storm.
- Compare your best trial with another team's result. Name one specific difference between the two designs and explain how it likely changed the amount of water held back.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Answer: The independent variable is the specific design change the team made between Trial 1 and Trial 2 (such as a taller dam or a better-sealed base); the dependent variable is the amount of water held back, measured in mL.
- Answer: Answers vary with each team's data; report which trial held back more water and the difference in mL between the two trials.
- Answer: Pressing the dam's base firmly into the pan and side walls closes gaps that water could otherwise slip through, so more of the poured water is forced to go over or be held by the dam itself rather than leaking around it, giving a more accurate test of the dam design.
- Answer: A check dam slows the water moving through the channel and creates a small pool upstream, giving some of the storm's water somewhere to collect instead of reaching the footbridge line all at once, which is the same reason real check dams reduce peak flow downstream during a storm.
- Answer: Answers vary by team; a strong answer names one concrete difference (dam height, base sealing, material choice, or dam shape) and connects it to why that difference likely changed how much water was held back.
Differentiation
Support
Provide a partially built dam frame (clay base already pressed into the pan) so struggling teams start at step 2 with the sealing step demonstrated. Pair students so one partner pours and times while the other measures and records, reducing the number of tasks any one student must track at once.
Extension
Have advanced teams add a second design variable while holding their base design constant, such as testing two different pour rates (fast versus the standard 15-second pour) with the same dam, and write a paragraph comparing which factor, design change or pour rate, produced the bigger difference in water held back.
ELL supports
Provide picture cards showing each material (clay, gravel, craft sticks) and a labeled diagram of the channel with "upstream," "downstream," and "footbridge line" marked, so students can match each word to its location in the physical setup. Allow the data recording sheet's design-change description to be completed with a labeled sketch instead of a written sentence.
Extensions
Teams that want to continue the investigation can test a third trial using a completely different dam material combination (for example, only craft sticks and tape, with no clay) and compare its held-back amount to their best clay-and-gravel design, discussing whether more materials always produce a better-performing dam.