Physical Geology Helpful Lab Hints

Exercise 8: Rivers & Humid Climate Landscapes

Problem 1

1. Complete Table 8.1 (p. 154)
   • "Are there:" For these 5 characteristics, refer to the lab text (p. 146) and figures 8.5 and 8.6 (p. 149).
   • Gradient = feet the river drops/miles of river length.
     • feet the river drops = number of contour lines crossed by the river X the contour interval
     • Measure the river length with a map wheel.
     • Be sure to note the scale and contour interval (C.I.) of the map.
   • Width of flood plain: measure bluff to bluff using the bar scale or the map wheel.
   • Sketch of valley profile: What does this valley look like in profile?
     • Sketch a profile in the space provided by using the pattern of contour lines.
     • Where the lines are close together, draw a steep slope.
     • Where the lines are far apart, draw a flat line.
     • Example for Missouri River: \____/
     • Bonus: You may draw a topographic profile (side view) as described below and submit for extra credit.
   • Is the river eroding down (down-cutting) or side-to-side (lateral) or a combination of both?
2. Think about how natural levees form and how they are depicted in the figures in the text and lab books.
   • Lab book on page 146 and shown in the diagram on page 149
   • Text book in Section 16.8, part B.
3. Which type of levee (natural or man-made) is larger? Which type is more continuous? What characteristics would make it more likely that a levee would show up on the map?
4. Look very carefully at the map. Contour lines make a V when they cross a stream. The V points uphill (upstream).
5. 1. When a river floods, the levees, although next to the river channel, are the high ground and will flood last.
   2. Cutoffs are described in:
      • Lab book on page 146 and shown in the diagram on page 149
      • Textbook in Section 16.5, part C
   3. A canal would be straight.

Topographic profile: Draw a cross-section from A-A' on page 161.

• Refer to pages 103 & 105 in the lab book (in lab 6) for the technique.
• Use the Lab Help from Lab 6, Exercise 2f as a refresher.

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last updated: 2020-09-06