Earth Science: Topographic Profiles and Watershed Boundaries
Reading contour maps, drawing profiles, and identifying drainage divides
Earth Science: Topographic Profiles and Watershed Boundaries
Reading contour maps, drawing profiles, and identifying drainage divides
Earth Science - Grade 6-8
- 1
A topographic map has contour lines labeled 200 m, 220 m, 240 m, and 260 m. What is the contour interval on this map? Explain how you know.
Subtract the elevation of one contour line from the next contour line.
The contour interval is 20 meters. The elevation increases by 20 meters from one labeled contour line to the next. - 2
On a topographic map, contour lines are very close together on the east side of a hill and far apart on the west side. Which side has the steeper slope? Explain your answer.
The east side has the steeper slope because closely spaced contour lines show that elevation changes quickly over a short distance. - 3
A stream crosses contour lines labeled 500 m, 480 m, 460 m, and 440 m. In which direction does the stream flow if it crosses them in that order from north to south?
Streams flow from higher elevation to lower elevation.
The stream flows from north to south because water flows downhill from higher elevations to lower elevations. - 4
Contour lines form a series of V shapes where they cross a stream. The points of the V shapes point uphill. If the V shapes point toward the west, which direction is upstream?
The V shape made by contour lines points toward higher elevation and upstream.
Upstream is toward the west because contour line V shapes point upstream where they cross a stream. - 5
Point A is on a 320 m contour line. Point B is on a 400 m contour line. If a straight trail connects A to B, what is the total elevation gain from A to B?
The total elevation gain is 80 meters because 400 meters minus 320 meters equals 80 meters. - 6
A map scale shows that 1 centimeter equals 0.5 kilometers. A stream is 6 centimeters long on the map. What is the stream length in kilometers?
Multiply the map distance by the distance represented by 1 centimeter.
The stream length is 3 kilometers because 6 centimeters times 0.5 kilometers per centimeter equals 3 kilometers. - 7
A topographic profile is drawn along a line from point A to point B across a hill. The contour elevations crossed are 100 m, 120 m, 140 m, 160 m, 140 m, 120 m, and 100 m. Describe the shape of the land along the profile.
The land rises from 100 meters to a high point of 160 meters and then descends back to 100 meters. The profile shows a hill or ridge crossed by the line from A to B. - 8
When making a topographic profile, why is it important to mark where each contour line crosses the profile line?
A profile graph shows distance along the line and elevation at each point.
It is important because each crossing gives the elevation at a specific location along the profile line. These points are used to draw the shape of the land surface. - 9
A watershed boundary separates two stream systems. What happens to rainwater that falls on opposite sides of the boundary?
Rainwater that falls on opposite sides of the watershed boundary drains into different stream systems or different drainage basins. - 10
On a topographic map, watershed boundaries are usually drawn along which landforms: valley floors, stream channels, or ridges and high ground? Explain your choice.
A divide is high ground that separates the direction water flows.
Watershed boundaries are usually drawn along ridges and high ground because water flows away from high areas into different drainage basins. - 11
A ridge has elevations of 700 m, 720 m, and 740 m along its crest. Two streams start on opposite sides of the ridge and flow away from it. Explain why the ridge is likely a watershed boundary.
The ridge is likely a watershed boundary because it is high ground, and streams on opposite sides flow away in different directions into separate drainage areas. - 12
Look at a topographic map where a closed contour line has small tick marks, called hachures, pointing inward. What landform does this usually show?
Hachure marks on contour lines point toward lower elevation.
A closed contour line with hachures pointing inward usually shows a depression, which is an area lower than the land around it. - 13
A student draws a watershed boundary across the middle of a stream channel. Explain why this is usually incorrect.
This is usually incorrect because a watershed boundary separates drainage areas, while a stream channel is where water collects and flows. Boundaries are usually on ridges or high ground, not in stream channels. - 14
A line from X to Y crosses contour lines at these elevations: 50 m, 100 m, 150 m, 200 m, 250 m, and 300 m, with no decrease in elevation. What would the topographic profile look like?
A profile rises when each contour line crossed has a higher elevation than the one before it.
The topographic profile would show a steady uphill slope from X to Y because the elevation increases continuously from 50 meters to 300 meters. - 15
A town is located in a watershed that drains into River A. A factory is built upstream in the same watershed. Explain why pollution from the factory could affect the town's water.
Pollution from the factory could affect the town's water because water and dissolved materials flow downhill through the same watershed into River A. If the town uses water from that river or connected streams, the pollution could travel downstream to the town.