Background - A stream table may be used to study rivers and river processes. A stream table consists of a system with a slope that delivers water to one end which moves downhill through and over soil, sand, or other substances. Observing what happens in a stream table can be very helpful in interpreting what we see in nature.

Procedure - Step One - Before the water is turned on, observe the stream table layout. Make sketch 1 of the path you think the water will follow.

Step Two - Observe the stream table for awhile with the water running. Do you see evidence of ground water accumulation? Are there any springs developing? Make sketch 2 of the stream after the water is stopped. Did it follow the path you had thought it would? Why or why not?

Step Three - With the water turned back on, watch for places you see erosion occurring. Note these on sketch 2 with arrows and labels. Is there a pattern to where the erosion seems to take place? When the teacher stops the water again, make sketch 3 of the stream. Has it remained the same?

Step Four - Plant some ‘trees’ in some of the places where the erosion is occurring and turn the water back on. What happens?

Step Five - Place a few long rocks in the stream bed. What happens? Try them in pairs at different 45 degree angles with the stream flow. Any differences in how they affect the stream?

Step Six - Notice the curvature in the stream. This characteristic is called a meander and is the predominant pattern of streams The radius of curvature is measured by visualizing the meander as part of a circle and then measuring the radius of the circle. What is the radius of curvature of the most circular meander?

Step Seven - The wavelength is the distance from one point on a wave to the next place that it occurs again. For example, measuring from crest to crest of two waves will give the wavelength. Measure and record the wavelength of this meander. Channel width is the distance across the channel. Measure and record the channel width.

In most streams, a relationship occurs between the radius of curvature, the wavelength and the channel width. The wavelength is usually about 11 times the channel width. The radius of curvature averages about one fifth or 0.2 or 20% of the wavelength.

Step Eight - Using the measurements you have just collected, calculate how many times larger the wavelength is than the channel width? Record this. Were you close to 11?

Using the data just collected, calculate the ratio of the radius of curvature to the wavelength. Record this. How close were you to 20%?

Step Nine - The thalweg is the deepest part of the stream. In most streams, bars, or shallow areas, alternate on the sides of the thalweg. Smooth the stream table and make one more stream. Sketch 4 should show the path of the stream, the thalweg and a series of bars. Do they alternate?

Conclusion: Write a paragraph discussing what you’ve learned in this activity. Include your ideas about why streams meander and why our stream table may behave differently than a stream in nature.