Experiment 12.3: Modeling Water Erosion and Landforms

Student Information

Purpose

To model and observe how flowing water creates different landforms through erosion and deposition processes.

Background Information

Water is one of the most powerful forces shaping Earth's surface. As water flows over land, it can erode (wear away) soil and rock, transport sediment, and deposit materials in new locations, creating various landforms.

When water flows downhill, it picks up and carries sediment. The faster the water moves, the larger the particles it can carry. As water slows down, it begins to drop its sediment load, with larger particles settling first.

Some key landforms created by water erosion and deposition include:

Meanders: Curves in a river formed when faster water on the outside of a curve erodes the bank while slower water on the inside deposits sediment.
Oxbow Lakes: Curved lakes formed when a river cuts through the neck of a meander, abandoning the original curved channel.
Flood Plains: Flat areas around a stream that are covered by water during floods.
Alluvial Fans: Fan-shaped deposits formed when a stream flows from steep mountains onto a flat plain.
Deltas: Deposits formed where a river enters a lake or ocean and slows down, dropping its sediment.

In this experiment, you will create a model stream table to observe how water creates these landforms through the processes of erosion and deposition.

Materials

Large plastic storage container or aluminum baking pan (at least 12" x 16")
Sand (about 5 pounds)
Small pebbles or aquarium gravel (about 1 pound)
Clay or modeling clay (small amount)
Water (1-2 gallons)
Watering can or plastic bottle with holes punched in the cap
Wooden blocks or books to create slope
Ruler
Spoon or small trowel
Paper towels
Camera or smartphone for documentation
Optional: Food coloring to track water flow

Safety

Safety Precautions:

Be careful when handling water around electronic devices.
Clean up any spilled water promptly to prevent slipping hazards.
Wash hands after handling sand and clay.
Perform this experiment in an area that can get wet, like outdoors or on a water-resistant surface.

Procedure

Part 1: Setting Up Your Stream Table

Place your plastic container or baking pan on a flat surface.
Prop up one end of the container using books or wooden blocks to create a slope (about 2-3 inches higher than the other end).
Fill the higher end of the container with a mixture of sand and small pebbles to a depth of about 2 inches. This represents the land surface.
At the lower end of the container, leave a small area without sand to serve as a "lake" or "ocean" where water can collect.
Use your finger or a spoon to create a small depression down the center of your sand mixture. This will be the initial path for your "river."
Optional: Place a small piece of clay in one area to represent more resistant rock.

Part 2: Creating Water Erosion

Fill your watering can or plastic bottle with water. If using food coloring, add a few drops to help visualize the water flow.
Slowly pour water at the highest point of your stream table, allowing it to flow down through the depression you created.
Observe how the water flows and how it affects the sand and pebbles. Take photos or make sketches at this stage.
Continue adding water in small amounts, observing the changes each time.
After several additions of water, let the model sit for a few minutes to allow sediment to settle.

Part 3: Creating Meanders and Oxbow Lakes

Reshape your stream table by smoothing out the sand and creating a gentle slope.
This time, make a slightly winding path for your initial stream instead of a straight one.
Pour water slowly and observe how the curves in your stream become more pronounced over time.
Continue adding water until you observe the formation of meanders.
If possible, continue until you see the water cut through the neck of a meander, creating an oxbow lake.

Part 4: Creating Alluvial Fans and Deltas

Reshape your stream table again, creating a steeper slope at the upper end that transitions to a flat area.
Mix some sand with water to create a slurry.
Pour this mixture down from the top of the slope and observe how it spreads out when it reaches the flatter area, forming an alluvial fan.
For a delta, ensure there is a small "lake" at the bottom of your slope and observe how sediment builds up as water enters the lake.

Data Collection

Landform	Observations	Sketch/Photo Description
Initial Stream Formation
Meanders
Oxbow Lake (if formed)
Alluvial Fan
Delta
Areas of Erosion
Areas of Deposition

Analysis Questions

1. How did the speed of water affect erosion in your model? Where was erosion most noticeable?

2. Explain how meanders formed in your stream model. Why did the water flow faster on the outside of curves?

3. Compare and contrast the formation of alluvial fans and deltas in your model. What conditions led to each?

4. How does the size of sediment particles relate to where they were deposited in your model?

5. How does this model represent real-world water erosion processes? What are some limitations of this model?

Conclusion

Summarize what you learned about water erosion and deposition from this experiment. Explain how these processes shape Earth's surface and create different landforms over time.

Extension Activities

Try these additional activities to further explore water erosion and landforms:

Research real-world examples of meanders, oxbow lakes, alluvial fans, and deltas. Find satellite images and compare them to your model.
Investigate how human activities like dam construction affect natural erosion and deposition processes in rivers.
Modify your experiment to test how vegetation (represented by small plants or moss) affects erosion rates.
Create a time-lapse video of your stream table to show how landforms develop over time.
Design an experiment to compare water erosion with wind or glacial erosion processes.