Laboratory Manual for Introductory Geology 4e

EXERCISE 13.2
Why Some Streams Meander but Others Are Straight (continued )
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(d) Did the streams in Figures 13.5 and 13.6 support your hypothesis about the relationship between sinuosity and
gradient? Explain.
(e) What is the apparent relationship between sinuosity and the valley width/channel width ratio?
(f) What is the apparent relationship between stream gradient and the shape of a stream valley?
Now apply what you’ve learned to the photographs of the streams in Figures 13.1 and 13.3.
(g) Which probably has the steeper gradient, the River Cuckmere or the Yellowstone River? Explain your reasoning.
(h) Which of the streams in Figure 13.3 probably has the steepest gradient? The gentlest gradient? Explain your
reasoning.
13.3 Stream Valley Types and Features
The Yellowstone River and the River Cuckmere (see Fig. 13.1) illustrate the two
most common types of stream valleys: steep-walled, V-shaped valleys whose bottoms
are occupied fully by the channel, and broad, flat-bottomed valleys much wider
than the channel, within which the stream meanders widely between the valley walls
FIGURE 13.7 shows how these valleys form.
When water is added to a stream in a V-shaped valley, the channel expands and
fills more of the valley. When water is added to a stream with a broad, flat valley and
a relatively small channel, it spills out of the channel onto the broad valley floor in a
13.3 STREAM VALLEY TYPES AND FEATURES
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