Laboratory Manual for Introductory Geology 4e

EXERCISE 13.2
Why Some Streams Meander but Others Are Straight
Name:
Course:
Section:
Date:
In this exercise, you will use the maps in FIGURES 13.4, 13.5, and 13.6. Approximate mile measurements to the nearest
tenth of a mile.
(a) Compare the course of the Bighorn River between points A and B with that of its tributary between points C and
D (Fig. 13.4). Fill in the table below.
Bighorn River
Unnamed tributary
Channel length (miles)
Straight-line length (miles)
Sinuosity (no units)
Channel length divided by straight-line length
Highest elevation* (feet)
Lowest elevation* (feet)
Vertical drop
Highest elevation minus lowest elevation (feet)
Gradient* (feet per mile)
Vertical drop divided by channel length
*Streams aren’t considerate; they don’t begin and end on contour lines. Scan the entire stream looking for and estimating the highest and
then the lowest point on each stream. Then calculate the vertical drop and gradient.
(b) What is the apparent relationship between a stream’s gradient and its sinuosity?
(c) Test this hypothesis on the Genesee River of New York (Fig. 13.5) and the Casino Lakes area of Idaho (Fig. 13.6).
Fill in the table below and describe how the Genesee River differs from the Idaho streams.
Valley shape (V-shaped or broad with flat bottom)
Gradient (feet/mile)
Valley width (miles)
Channel width (feet)
Genesee River
(A–B)
Casino Lakes area
Stream A–B
Stream C–D
Channel essentially fills valley floor.
Valley width/channel width ~1.0 ~1.0
Sinuosity
Channel length divided by straight-line length
(continued)
13.2 HOW DO STREAMS WORK?
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