Appendix 4. USGS Topographic Map Exercise

We are accustomed to dividing our landscape according to political (municipal, county, state, or national) boundaries, but watersheds almost always cross political boundaries. Using topographic maps to delineate watersheds and determine their location with respect to political boundaries provides an alternative, more holistic way to look at our environment.

To familiarize your students with topographic maps (maps that show changes in elevation, and therefore can be used to determine watershed areas), purchase one or more of the four United States Geological Survey (USGS) maps that show a portion of the Great Swamp watershed (to show the entire watershed you need to piece together all four maps). The Great Swamp watershed is shown on the following USGS quadrangle maps: Chatham, Bernardsville, Mendham, and Morristown. Many area outdoor stores sell these maps for four or five dollars a piece. They can also be ordered directly from the USGS by calling 1.888.ask.usgs (be sure to ask for several copies of the "Topographic Map Symbols" brochure as well). If you plan to use the maps more than once, it is worth getting them laminated and having students use dry erase markers on the maps rather than pens or pencils.

Materials:

• One or more USGS topographic maps for the Great Swamp watershed area
• Current road map of the area (for comparison/location purposes)
• Dry erase markers
• USGS topographic key
• Great Swamp black and white topographic map (included)

Procedure:

1. Begin by establishing small groups gathered around one topographic map each. Go over the map using the topographic map symbols brochure to introduce students to the type of information that can be found on a topographic map. Once they are familiar with the way information is displayed on these maps, ask them to answer the following questions:

• What towns and counties are shown?
• What types of land use and land cover are present?
• When was the map originally drafted? Most recently updated?
• What is the contour interval for the map?

Then have the students examine the map for spatial patterns, such as:

• Changes in elevation from one area of the map to another
• How have humans adapted to the terrain (e.g., villages located in valleys versus steep hillsides, etc)?
• What direction do the streams flow in?

Finally, have the students delineate one or more watersheds on the map, using the points of highest elevation to determine the outline of a watershed (show them the Great Swamp watershed topographic map included with this activity).

• Have them mark x s (using pencils on un-laminated maps, or dry erase markers on laminated maps) along the ridge lines to determine points of highest elevation, and arrows to show which way the water would flow off the ridges or high points.
• Ask the students to delineate both the largest watershed on the map, and the smallest one they can find (e.g., perhaps the catchment area around their school).

Copyright 2000. Great Swamp Watershed Association.