Classroom activity Grade 4 Science
Holding the Chandry Creek Bank: A Cover Fair Test
A grade 4 station rotation testing bare soil, grass mat, and gravel on identical sloped trays to see which cover keeps a fictional creek bank from washing away.
Objectives
- Students will keep slope, water amount, and pour height the same while changing only the bank cover.
- Students will measure the channel cut into each tray and compare the cloudiness of the runoff collected.
- Students will use their station data to recommend one cover for a creek bank that keeps washing out.
Vocabulary
- Erosion
- Erosion is the wearing away and carrying off of soil and rock by moving water, wind, or ice. Fast-moving stormwater can strip soil from bare ground and stream banks.
Also: runoff, sediment, fair test, variable
Teacher overview
Groups of three or four rotate through three sloped trays that stand in for the same stretch of bank along Chandry Creek, a fictional creek that has been losing soil into the water after every storm. Each tray has a different cover on its lower half, and every other condition stays the same, so the tray is a controlled test rather than a demonstration. Students change only the cover as they move between stations, and they record only two things at each tray: how far the water cut into the slope and how much soil the water carried away. By the end of the rotation each group holds three jars of runoff and can line them up in order from clearest to muddiest.
Activity Directions
Set up the three stations before class (15 min of prep). Fill each tray with sand or dry topsoil about two inches deep and smooth the surface. Prop the same end of every tray on a book of the same thickness so all three slopes match. Leave Station 1 bare. Lay the sod or grass mat over the lower half of Station 2. Spread gravel over the lower half of Station 3. Set a clear jar at the low end of each tray to catch the runoff, and put a labeled cup with a small hole in it at each station.
Frame the problem (5 min). Tell students that the bank along Chandry Creek washes out after storms and fills the creek with mud. Ask what the town could put on that bank to hold the soil. Record their ideas, then name the three covers they will test.
Set the fair-test rules together (5 min). Write the rules where everyone can see them. The same 300 milliliters of water goes into every cup. The cup is held at the same height, marked with tape on a ruler taped upright at each station. The slope is the same at all three trays. Only the cover changes. Ask the class why changing two things at once would make the results useless.
Run station 1 (10 min). Each group pours its measured water into the cup, holds the cup at the marked height, and starts the timer. When the water stops running, students measure the longest channel cut into the soil in centimeters, then hold the collection jar against white paper and rate the cloudiness from 1 for clear to 5 for very muddy. They record both numbers on the handout.
Rotate to stations 2 and 3 (20 min). Groups repeat exactly the same procedure at the two covered trays, catching the runoff in their own jar and resetting the tray surface with a plastic spoon between groups. Remind students not to press the cover down harder at one station than another, because packing the soil is a change they did not intend to make.
Debrief (10 min). Ask each group to line up its three jars from clearest to muddiest and hold them up. Ask two questions of the whole class. Which cover let the least soil move, and how do the jars show it? What would you tell the town of Chandry to put on the bank, and which measurement is your best evidence? The activity ends when every group has three completed rows and has answered the handout questions.
Student Handout
Each tray stands for the same stretch of bank along Chandry Creek. Only the cover on the bank changes. At every station your group pours the same 300 milliliters of water, holds the cup at the same marked height, and uses the same tray slope and the same soil. Record your measurements as you go. Rate cloudiness from 1 for clear water to 5 for very muddy water.
| Station | Cover on the bank | Channel length (cm) | Cloudiness (1 to 5) |
|---|---|---|---|
| 1 | Bare soil | ||
| 2 | Grass mat | ||
| 3 | Gravel |
Which station had the longest channel cut into the soil?
Which station gave you the clearest jar of runoff?
How much longer was the channel at Station 1 than the channel at Station 2?
Name three things your group kept the same at all three stations.
Which cover would you tell the town of Chandry to put on the creek bank? Use one number from your table as your reason.
Muddy runoff carries soil into the creek. Explain one problem that extra soil could cause for the creek.
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: Accept the station the group's own data shows, most often Station 1.
Bare soil almost always cuts the longest channel because nothing slows the water at the surface. Accept a different station only when the group's recorded numbers support it.Answer: Accept the station the group's own data shows, most often Station 2.
The grass mat usually gives the clearest jar because the roots and blades hold loose grains in place. Gravel often comes second.Answer: Accept any difference the group's two measurements support.
Check the subtraction against the two channel lengths in the table. A group with 14 centimeters at Station 1 and 5 centimeters at Station 2 should write 9 centimeters.Answer: Accept any three of the controlled conditions.
Correct responses include the amount of water, the pour height, the slope of the tray, the type of soil, and the cup used. Do not accept the cover, because the cover is the one thing that changed.Answer: Accept any cover the group's own numbers support.
A complete answer names one cover and cites one measurement, such as a shorter channel or a lower cloudiness rating, as the reason for the choice.Answer: Accept any reasonable harm caused by extra soil.
Correct responses include cloudy water blocking sunlight from plants, mud settling on the stream bottom and covering fish eggs, or the creek filling in and holding less water during a storm.
Differentiation
Support
Pair these students with a recorder and give them a pre-drawn ruler strip taped along the tray so channel length can be read directly rather than measured from zero. Provide a printed cloudiness card with five shaded circles so the rating is a match rather than a judgment, and complete Station 1's row together as a class before groups rotate.
Extension
Have students design and run a fourth station of their own, choosing a cover the class did not test, such as wood mulch or a row of craft-stick fences set across the slope. They must state what they will keep the same, predict where their cover will rank, and then compare the result with their prediction in writing.
ELL supports
Pre-teach erosion, runoff, and fair test at the trays themselves, pouring a small amount of water while naming each word. Provide a picture card for each of the three covers to match to the table rows. Give sentence frames for the debrief: "Station ___ had the longest channel" and "I would use ___ because my jar was ___."
Extensions
Take the class outside to find a spot on the school grounds where soil has washed out, then sketch it and label the cover that is present or missing. Groups can write a short recommendation to the grounds crew that names one cover from the rotation and one measurement from their table.