Name: _______________________________________________ Section:_______________________

part 2: topographic map Interpretation

Use the Dublin, GA and Thousand Springs, ID topographic maps (Figure 17.6 and 17.7) and the key to topographic map symbols to answer these questions.

1. What is the scale for each of these maps?

Dublin, GA 1:24000

Thousand Springs, ID 1:24000

2. What is the contour interval for each of these maps?

Dublin, GA 10’

Thousand Springs, ID 20’

3. What is the total relief (difference between highest and lowest elevations) for each of these maps? [just the photocopy]

Dublin, GA Thousand Springs, ID

a. Highest elevation: ~305’ ~3450’

b. Lowest elevation: ~200’ ~2890’

c. Total relief: ~105’ ~560’

4. Both maps have the same scale but different contour intervals.

a. Why are the contour intervals different? (Hint: consider the total relief.)

The greater elevation difference (especially on the very steep canyon walls) in Idaho makes it less feasible to show clearly separate contour line per unit horizontal distance.

b. What would the Thousand Springs, ID map look like if it had the same contour interval as the Dublin, GA map?

Twice as many contour lines per unit distance, and an unreadable cluster at the “cliffs”.

5. Calculate the following three gradients in feet per mile. Round your answers off to one decimal place. Show all your work!

a. from point A to point B on the Dublin, GA map 28.3’/mile

102’/3.6mi

b. from point A to point B on the Thousand Springs, ID map 115.6’/mile

208’/1.8mi

c. from point C to point D on the Thousand Springs, ID map 1305’/mile

261’/0.2mi

6. Compare the three gradients you calculated in question 5 with the spacing of the contour lines associated with each location. Classify the contour line spacing as wide, moderate or close.

Gradient Contour Line Spacing

a. Dublin (A to B) 28.3’/mile wide

b. Thousand Springs (A to B) 115.6’/mile moderate

c. Thousand Springs (C to D) 1305’/mile close

d. What relationship exists between gradient and contour line spacing?

Steeper elevation gradients (“slopes”) have closer contour line spacing

7. Draw a topographic profile along the line drawn from point X to point Y on the Dublin, GA map. Use the graph paper in Figure 17.8. Transfer the contour lines to the edge of a piece of paper as a series of tick marks, and then transfer the tick marks along with their elevations to the bottom of the graph paper. Determine the range of elevations that need to be included on the vertical axis. The map scale, and the scale of the horizontal axis on the graph is 1:24,000 or, 1 inch on the map or graph equals 2000 feet on the Earth. Draw the profile with a vertical exaggeration of 20X. A vertical exaggeration of 20X means that a distance of 1 inch equals 2000 feet on the horizontal axis, but on the vertical axis, a distance of 20 inches equals 2000 feet. As a result, 1 inch on the vertical axis equals 100 feet. The lowest elevation is marked on the graph (Figure 17.8). Finish labeling the vertical axis, increasing elevation 100 feet every time you move up 1 inch. Plot a point at the appropriate elevation above each tick mark and connect the points with a smooth curve. Remember to give your profile a title, label your axes, state the vertical exaggeration, and copy the graphic scale from the map. Mark on the profile and label the location of any rivers that cross the profile line. See Appendix C for more details on profiling.

8. Draw a topographic profile along the line drawn from point X to point Y on the Thousand Springs, ID map. Use the graph paper in Figure 17.9. Follow the same steps as for question 7. Use a vertical exaggeration of 20X for this profile.

9. Using your topographic profiles from questions 7 and 8, determine the local relief for the following two river valleys:

Hunger & Hardship Ck, GA Snake River, ID

a. Highest elevation: 306’ 3996’

b. Lowest elevation: 204’ 2893’

c. Local relief: 102’ 1103’

10. a. Examine your profile of Dublin, GA. Circle the two steepest segments of your topographic profile.

b. What is the contour line spacing like at these two segments compared to the contour line spacing along the rest of the profile line? Much closer spacing

c. Examine your profile of Thousand Springs, ID. Are the two steepest segments on this profile steeper, about the same, or less steep than the two segments you circled on your Dublin, GA profile? East canyon wall is steeper; west wall about the same as steepest Dublin slope

d. Could we just look at the contour line spacing on these two maps to determine which map has steeper slopes? Why or why not? Probably not, because the contour interval differs

11. Figures 17.10 and 17.11 have other versions of the topographic profile for Thousand Spring, ID. These profiles were drawn along the same line as the profile you drew for question 8, but Figure 17.10 has a 10X vertical exaggeration, while Figure 17.11 has only a 2X vertical exaggeration. Compare Figures 17.10 and 17.11 with your profile from Thousand Springs, ID (Figure 17.9).

a. Does the change in vertical exaggeration affect the way the landscape is portrayed?

Heightens the vertical appearance

b. Does the change in vertical exaggeration affect how steep the landscape looks on the profile? (Think if you were planning to hike along this line – does one profile suggest an easier hike than the other?)

Yes; vertical exaggeration appears to amplify steepness

c. What do you think your profile from Dublin, GA would look like if you had drawn it with only a 2X vertical exaggeration?

d. If you want to compare the landscape in Dublin, GA with the landscape in Thousand Springs, ID, which Thousand Springs profile would be more appropriate, the one you drew (Figure 17.9), Figure 17.10, or Figure 17.11? Why?

The amount of exaggeration is less important for comparison than using the SAME exaggeration level.

12. The small squares on the Dublin, GA map represent individual buildings (houses, schools, businesses, etc.).

a. In what part of Dublin are there the most new buildings? The west side uplands

b. Why aren’t all the buildings in downtown Dublin drawn in? pink urban area is too crowded with buildings (and they change too often) to show all.

c. How does the map show that the downtown area has a lot of buildings? Pink shading

13. a. Which map has more wooded area, Dublin, GA or Thousand Springs, ID?

Dublin

b. How do you know? More green shading

14. Streams and rivers are shown in blue. Streams that flow only during the wet season or during storms are called intermittent streams and are shown by a blue line drawn as a dash and three dots. Streams that flow all year round are shown by a solid blue line. Larger streams and rivers are thicker blue lines.

a. Which river probably has more water in it, the Snake River, ID, or the Oconee River, GA? How do you know?

Snake River; it is a larger year-round channel

b. Does the northwestern part of Hunger and Hardship Creek, GA flow all year round? How do you know? No; it has an occasionally dotted (intermittent) channel

c. Tributaries are smaller streams that flow into larger streams. Do the tributaries along the northwestern part of Hunger and Hardship Creek, GA flow all year round? How do you know? No; they have occasionally dotted (intermittent) channels

15. Examine the contour lines that cross the northwestern part Hunger and Hardship Creek, GA.

a. Which way do these contour lines bend (north, south, northeast, etc) as they cross the creek? Toward the northwest

b. What does this tell us about the direction the water is flow towards? Toward the southeast

c. Do the contour lines crossing the tributaries to Hunger and Hardship Creek bend towards or away from Hunger and Hardship Creek? away

d. Based on the way the contour lines bend, is the water in these tributaries flowing into or out of Hunger and Hardship Creek? into

e. Keeping in mind your answers to the above questions, which of the two lines, labeled J and K on the Dublin, GA map, is a more likely location for a stream? [There is no J or K on the current copy!]