Purpose: This activity will allow students to observe how erosion changes the geography of a region by carrying sediment from one location and depositing it in another. Students will then investigate how different types of surfaces and barriers can slow or accelerate erosion.
Procedural overview: In this activity, the class will begin by watching a stream table demonstration. Following this demonstration, students will record their observations, noting how different geography affected how water carried sediments from one location to another. After the demonstration, students will work with their own stream tables in groups to explore variables that affect erosion.
Each group will change one variable that could affect erosion rates and record what they see. Each group will then repeat their stream table work for the class to share how their variable influenced erosion on their table.
The stream table work can be paired with erosion-related activities in the Science News Learning Educator Guide: Shores Still Reeling from the 2010 Oil Spill.
Approximate class time: 1 class period
Disposable heavyweight aluminum foil pans
Rocks of varying sizes
Directions for teachers:
Have students read the onlineScience News article “The Deepwater Horizon oil spill ruined long-term shore stability” for homework. A version of the article, “Shores still reeling from 2010 oil spill,” appears in the March 25, 2023 print issue of Science News.
Gather all necessary supplies and place them at stations around the room. Read “Stream table teacher demonstration” and review the diagram of the stream table setup. to prepare for your classroom demonstration. Also, punch holes at one end in the bottom of the disposable aluminum foil pans that will serve as the stream tables.
Stream table teacher demonstration
The stream table will be made of a disposable foil pan elevated at one end with holes punched in the bottom of the pan at the other end. This pan should be elevated so that the end of the pan with holes is placed inside a second foil pan or similar object that can collect water used during the demonstration.
Fill the foil pan with enough sand that it reaches the top of the pan on one end. Then slope the sand from the elevated end of the pan down toward the lower end of the pan. The lower end of the pan should have several holes punched into the bottom, and the sloped sand should end approximately 2 inches from these holes. No sand should rest at the lower end of the pan when the demonstration begins. The amount of sand needed will vary depending on the size of the aluminum pan used.
Using a watering can or cup, pour water at the elevated end of the pan, letting the water flow over the sand and out the holes at the bottom. A diagram showing the setup of the stream table is provided.
Demonstration 1 will show erosion on a sloped, flat surface. After water is poured on the top of the stream table and you’ve given students time to record their observations, reset the stream table for Demonstration 2.
For Demonstration 2, reset the sand so that it slopes down from the top of the stream table, and then create mounds of sand on the slope to represent mountains. Pour water on the top of the stream table, allow students to record observations and then reset the stream table for Demonstration 3.
In Demonstration 3, flatten the sand so that it slopes down toward the bottom of the pan and then carve a straight line in the sand to mimic a straight streambed or channel. The aluminum pan should be visible at the bottom of this streambed/channel. Pour water over the stream table the same way as in Demonstrations 1 and 2.
Ask students to record their observations.
Stream table observations
After you finish your streambed demonstrations, ask students to answer the following questions.
1. What happened to the sediment as water flowed down the stream table?
As water flowed down the stream table, it carried sand from the top of the stream table to the bottom of the stream table, where it was then deposited.
2. What happened to the mountains as water flowed down the stream table?
As water flowed down the stream table, it moved around the mountains, creating deep valleys. The water also eroded the mountains, making them smaller.
3. What happened to the straight streambed as water flowed down the stream table?
As water flowed through the straight stream, the stream’s banks began to break down, which caused the stream to change course.
4. The stream table demonstrates the process of erosion. What is erosion?
Erosion is the geologic process in which wind and water carry sediment from one location to another.
5. What changes do you think would increase erosion in the stream table? Why?
Student answers will vary. More erosion could occur as the change in elevation from the top to the bottom of the stream table increases and as sand is sloped to create geographical features, like mountains. These changes happen because water picks up speed as it moves downhill, allowing the water to carry more sediment as it goes.
6. What changes do you think would decrease erosion in the stream table?
Student answers may vary. Having groundcover around a stream might reduce the amount of erosion that occurs. Plants can hold the soil in place as water flows through the stream, preventing the soil from eroding.
7. Describe the sediment used in the stream table. Why might we use this type of sediment in the stream table to demonstrate erosion?
The stream table contains sand. Sand does not stick together, meaning that water and wind can easily carry sand away, causing erosion. Using sand in the stream table helps accelerate a process that might be much slower with sediments that stick together, like clay.
8. How is the simulated erosion in the stream table different from how erosion actually occurs?
The stream table has not been exposed to wind or other natural weathering processes. The stream table also does not include plants, non-sand soil or other elements that might affect erosion rates, and the table does not include human impacts.
How erosion happens
Following the teacher-led stream table demonstration, students will be divided into six groups. Each group will work with their own stream table to study a variable that influences erosion. The materials that each group needs along with their experimental approaches are noted below. Please provide the needed materials and instructions for their approach to each group.
Group 1 will study elevation change within their stream table and test their different elevations with straight streambeds of flattened sand (based on teacher-led Demonstration 1). This group should raise and lower the elevated end of their stream table to adjust its slope.
Group 2 will use different sediments in their stream table and will also perform their tests with straight streambeds of flattened sediments. This group should be provided with soil in addition to the sand. Ideally, this group should be provided at least two different soil samples to test.
Group 3 will experiment with different stream patterns: a straight stream, a curving stream and a branched stream. The branched stream can be either a dendritic stream or a distributary. Dendritic stream patterns occur when multiple creeks, streams and rivers converge to form a single stream as they flow downward. To model this in the stream table, create multiple streams at the top of the stream table and have them converge into a single stream before reaching the bottom of the stream table. Distributaries occur when a single stream branches into smaller streams. Model a distributary by creating one stream at the top of the stream table and then add splits to create multiple streams before reaching the bottom of the stream table.
Group 4 will observe how erosion affects different landforms: hills, mountains of varying heights and an island coastline. Students will create large rolling hills by making waves in the sand; mountains will be piles of sand. To create the island coastline, move all the sand to one side of the stream table. For this final scenario, the water should be poured at the top of the stream table near the edge of the sand to model ocean currents along a coast.
Group 5 will study different surfaces to see how they influence erosion patterns and perform their tests with a streambed of flattened sand. Provide this group with felt, rocks and craft foam that can be placed on top of the flattened sand in ways that model a landscape. Tell students that the felt represents ground cover/plant life, the rocks represent rocky surfaces and the craft foam represents impermeable surfaces.
Group 6 will focus on how weather conditions can cause erosion. This group should be located near a sink or another water source. Students will perform their tests with streambeds of flattened sand. Students can use a watering can to pour water at slow, medium or fast speeds over the top of their stream table to represent different rainy conditions. The first test should mimic a light rain, the second a moderate rainfall and the third should be a heavy rain that could cause flooding.
Students should use their worksheets to record how the changes they make influence erosion. After students have experimented with their stream tables, each group should set up their stream table using the parameters that produced the most interesting results for a class-wide demonstration. As each group shares, students should note key observations on their worksheets.