Stream Flow: Does the stream meander?

Purpose/Hypothesis

Rivers and streams can carve patterns into Earth's surface. This experiment will simulate the force that water can have in an environment. Will a water travel in a straight path down a slope? Before you begin, make an educated guess about the outcome of this experiment based on your knowledge of stream patterns. This educated guess, or prediction, is your hypothesis. A hypothesis should explain these things:

• the topic of the experiment
• the variable you will change
• the variable you will measure
• what you expect to happen

A hypothesis should be brief, specific, and measurable. It must be something you can test through observation. Your experiment will prove or disprove whether your hypothesis is correct. Here is one possible hypothesis for this experiment: "A gentle flow of water across a downward sloping landscape will create a meandering stream path, while a more forceful flow will create a straighter path."

In this case, the variable you will change is the velocity of the water flow, and the variable you will measure is the resulting stream pattern. You expect the stream to meander for low flows and be straighter for higher flows.

Level of Difficulty

Easy.

Materials Needed

• flat outdoor area
• hose and water supply
• 24-inch (61-centimeter) long shallow pan, such as a plant tray
• 5 pounds (2.2 kilograms) sand for a sandbox
• 5 pounds (2.2 kilograms) gravel
• 2 bricks or wooden blocks for support

Approximate Budget

$8 for sand and gravel.

Timetable

45 minutes.

How to Experiment Safely

Handle the bricks carefully to prevent injury.

Step-by-Step Instructions

1. Pour equal amounts of gravel and sand into the tray and mix well. Make the surface level and smooth from one end to the other.
2. Lift one end approximately 6 inches (15 centimeters) high and place a brick underneath. Place the other brick in front of the lower end to keep it from sliding.
3. Place the end of the hose at the high end of the box.
4. Turn the hose on for 2 minutes, allowing a very soft flow of water to run over the sand.
5. After 2 minutes, turn off the water and diagram the pattern of water.
6. Turn the water on again for 2 more minutes; then turn it off and diagram the pattern again.
7. Smooth the surface of the sand and gravel and repeat steps 4 through 6 with a higher water flow rate.

Summary of Results

Study your diagrams and the tray of sand. Which size particle of sand or gravel moved the most? As the stream flowed longer, how were the patterns affected? Did your stream begin to meander at the lower flowrate and go straighter at the higher flowrate? Write a paragraph summarizing your results and explaining them.

Source: Experiment Central. U·X·L, 2000.