Classroom activity Grade 7 Art & Music
Keelback Creek Culvert: A Flow-Line Drawing Studio
Grade 7 pairs test three ways to draw water speeding up in a narrow culvert (streamlines, streaks, and scaled arrows), then swap drawings for a cold-read test.
Objectives
- Students will draw the same stretch of moving water with three visual conventions: evenly counted streamlines, motion streaks, and arrows scaled to speed.
- Students will explain why streamlines must crowd together, rather than stop or multiply, where water passes through a smaller opening.
- Students will use a cold-read test with other viewers to judge which convention communicates speed most clearly.
Vocabulary
Key words: streamline, motion streak, visual convention, line spacing, constant of proportionality, culvert, cold read
Teacher overview
This station activity for pairs gives grade 7 students a real illustration problem: how to draw water so that a stranger can see where it speeds up. The fictional Rushford Nature Center plans a trail sign beside the Keelback Creek culvert, where the creek squeezes through a concrete pipe under the path, and the sign needs a drawing that shows the water moving faster inside the pipe. Pairs try three visual conventions at three stations (six evenly counted streamlines, motion streaks, and arrows scaled to speed), then pass their drawings to another pair for a cold-read test in which the readers must find the fastest and slowest water without seeing the data. Each drawing rule communicates only if it follows how water actually moves, so students must apply the hydraulics correctly in order to make the drawing clear.
Teaching note: a common misconception is that water slows down when it is forced through a narrow opening, as if the pipe holds it back. In steady flow the same volume of water passes every cross-section each second (flow equals area times velocity), so when the opening shrinks to one third of its area, the speed triples. Students carry the same error into their drawings. Many draw extra lines inside the culvert to show "more" water, or let streamlines stop at the culvert mouth, and both choices tell the viewer that water is being created or lost inside the pipe. Station A is built to surface this, and the debrief returns to it directly.
Activity Directions
- Before class (about 10 minutes of prep), draw the culvert outline described below and print three copies per pair, print one data card per pair from the Student Handout, and set up three station tables labeled A, B, and C, each with markers and rulers. The outline is a top view drawn left to right across a landscape letter sheet: a channel 3 inches wide narrows to a culvert 1 inch wide, which opens into a pool 6 inches wide, with each part about 3.5 inches long. With 30 students you will have 15 pairs, 5 at each station.
- Opening (5 minutes). Project the outline and read the data card aloud. Point out that in our scenario the water is the same depth everywhere, so the width of each part of the outline stands for its area. Ask for a show of hands on where the water moves fastest, then state the rule on the card: every second, the same 12 cubic feet of water passes through each part, so the speed must be highest where the opening is smallest. Tell students their job is to make a hiker see that in a few seconds.
- Station rounds (3 rounds of 10 minutes). Each pair makes one drawing per station on a fresh outline sheet, then rotates from A to B to C (pairs that start at B go to C and then A). The station rules are printed on the handout. At Station A pairs draw exactly six streamlines that never start, stop, cross, or merge inside the water. At Station B they draw motion streaks whose lengths keep the speed pattern on the data card. At Station C they choose a constant, write it on the sheet, and draw one arrow in each part with a length equal to the constant times the speed.
- Cold-read test (7 minutes). Each pair folds scrap paper over any numbers on its sheets and passes its three drawings to the pair on its left. Readers mark F where the water looks fastest and S where it looks slowest on each drawing, and rate how sure they are from 1 (guessing) to 3 (certain). Readers may not talk to the artists during this step.
- Tally (3 minutes). Return the drawings. For each convention, ask artists to raise a hand if their readers placed both F and S correctly, and record the three counts on the board.
- Debrief and close (5 minutes). The activity ends when the tally is posted and pairs have answered the debrief questions on the handout. Ask two questions aloud: "Why must the six streamlines squeeze together inside the culvert instead of stopping at its mouth?" and "Which convention would a hiker read correctly in three seconds, and what would you borrow from the other two for the final sign?"
Student Handout
Keelback Creek data card (fictional, for this activity)
The Rushford Nature Center wants a trail sign that shows Keelback Creek flowing through a culvert, a concrete pipe that carries the creek under the trail. In our scenario the water is the same depth in every part, so the width on your outline shows the area of the opening.
| Part of the creek | Area of the opening | Speed of the water | Width on your outline |
|---|---|---|---|
| Upstream channel | 12 square feet | 1 foot per second | 3 inches |
| Culvert | 4 square feet | 3 feet per second | 1 inch |
| Downstream pool | 24 square feet | 0.5 foot per second | 6 inches |
In every part, 12 cubic feet of water passes by each second, because area times speed is the same everywhere.
Station rules
- Station A, streamlines: Draw exactly six lines that follow the water from left to right. A line may bend, but it may not start, stop, cross another line, or join another line inside the water. Space the lines evenly across each part.
- Station B, motion streaks: Draw short dashes that show how far a bit of water moves in one second. A culvert streak must be 3 times as long as an upstream streak, and a pool streak must be half as long as an upstream streak. You choose the upstream length.
- Station C, scaled arrows: Choose a constant, such as 1 inch of arrow for every 1 foot per second. Write it in the corner of your sheet. Draw one arrow in each part. Each arrow's length equals your constant times the speed.
Cold-read record (for readers)
For each drawing you receive, mark F where the water looks fastest and S where it looks slowest. Next to the letters, write how sure you are: 1 means guessing, 2 means fairly sure, and 3 means certain.
Debrief questions
- Use the data card. How many times faster does the water move in the culvert than in the upstream channel?
- At Station A, your six streamlines spread across 3 inches upstream and across 1 inch in the culvert. How many times closer together are the lines inside the culvert?
- A classmate draws ten streamlines inside the culvert but only six upstream, to show that the culvert is "busier." What does that drawing wrongly tell a viewer about the water?
- At Station C, one pair chose a constant of 1.5 inches of arrow for every 1 foot per second. How long should their culvert arrow be?
- For the same pair, with the same constant, how long should the pool arrow be?
- Look at the class tally. Which convention did readers get right most often? Give one reason based on how the eye reads spacing, length, or line weight.
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: 3 times faster.
The culvert speed is 3 feet per second and the upstream speed is 1 foot per second, and 3 divided by 1 is 3. - Answer: 3 times closer together.
Upstream, six lines share 3 inches, so they sit about 1/2 inch apart. In the culvert they share 1 inch, so they sit about 1/6 inch apart, and 1/2 divided by 1/6 is 3. The spacing shrinks by the same factor as the width, which is also the factor by which the speed rises. - Answer: It tells the viewer that water is being added inside the pipe.
Each streamline stands for a path that water follows, so four extra lines that begin inside the culvert show water appearing from nowhere. The same water must pass through, so the six lines should crowd together instead. - Answer: 4.5 inches.
1.5 inches per foot per second times 3 feet per second equals 4.5 inches. - Answer: 0.75 inch.
1.5 inches per foot per second times 0.5 foot per second equals 0.75 inch. - Answer: Accept any convention that matches the class tally when the reason refers to a visual property.
A strong reason names what the eye actually does. Crowded streamlines form a darker, denser patch that a viewer notices before measuring anything, while arrows ask the reader to compare lengths, which works best when the constant makes the culvert arrow clearly the longest. A reason such as "the lines bunch up and look darker where the water is fast" earns full credit, whichever convention the class tally favored.
Differentiation
Support
Give pairs outline sheets with the upstream part already drawn for each station: six streamlines spaced 1/2 inch apart for Station A, one upstream streak for Station B, and one 1-inch upstream arrow for Station C. Students then only continue the rule through the culvert and the pool. A paper ruler strip marked with the three widths (3 inches, 1 inch, and 6 inches) also helps students check their spacing without measuring from scratch.
Extension
Suppose the fictional trail crew replaces the culvert with a wider one whose opening is 6 square feet. Ask pairs to find the new culvert speed from the rule that 12 cubic feet passes each second (12 divided by 6 gives 2 feet per second), redraw one convention for the new culvert, and write two sentences explaining how their line spacing or arrow length changed and why. Pairs who finish early can design the final sign by combining the strongest features of two conventions and adding line weight as a second signal.
ELL supports
Post a word wall with a small sketch beside each term: streamline, streak, arrow, constant, culvert, upstream, and downstream. During the cold-read test, readers only need to write the letters F and S and a number, so students still building English can take full part. For the debrief, offer sentence frames such as "The water is fastest in the ... because the opening is ..." and "The lines should not stop because ...".
Extensions
Photographers show moving water with long exposures, in which fast water blurs into long streaks and slow water stays crisper. If a phone with a long-exposure setting is available, students can photograph water running from a school downspout or a faucet into a narrowing funnel and compare where the blur is longest with their Station B streaks. Comic artists use speed lines for the same purpose, and students can collect three examples from school library graphic novels and sort them by which convention they resemble.