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. EXERCISE 13.2 Why Some Streams Meander but Others Are Straight (continued) Name: Course: Section: Date:
(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. ( Which probably has the steeper gradient, the River Cuckmere or the Yellowstone River? Explain your reasoning.
(g) Which of the streams in Figure 13.3 probably has the steepest gradient? The gentlest gradient? Explain your 13.3 Stream Valley Types and Features