1. How to Read Topographic Maps Natural Resources Engineering
BAE 3313
Natural Resources Engineering
Source

2. Source: http://www.epa.gov/owow/watershed/whatis.html
How is a Watershed?
The total land area that contributes water to a stream, river or lake.
Source:

3. What is a Topographic Map?
Shows elevation data for a small piece of the earth
Shows physical and manmade features
U.S. Geological Survey (USGS) is the primary distributor of topographic maps
7.5 minute maps, 1:24,000 scale
Complete US coverage also available for 1:100,000 and 1:250,000
Amount of detail shown on a map is proportional to the map scale
1:24,000 - high detail
1:100,000 - moderate detail
1:250, low detail

4. 1:24,000 Topographic Map
Covers 7.5 minutes of latitude by 7.5 minutes of longitude
Approximately equal to 8 miles north-south and 6 miles east-west
One map called a quadrangle or “quad”
28 inches long by 21 inches wide
Purchase from USGS or most outdoor stores

5. Cultural and Physical Symbols
Forest: Shown in green
Unforested: White; May be grass, soil, or some other surface
Roads: Two parallel lines; Unbroken lines indicate paved roads, broken lines unpaved
Trails: Dashed lines
Streams and Rivers: Thin lines for streams, large blue area for larger rivers
Lake: Solid blue area
Marshy Area: Blue symbols enclosed by blue dashed line
Buildings: Building shapes shown, may be filled or unfilled
UTM Grid Lines: Especially useful for GPS, each grid square is 1 km x 1 km

6. Contours
Contour lines are continuous brown lines. Each line represents a specific elevation, and all locations along that line have the exact same elevation.
"Contour Interval 20 Feet" means that the elevation change between contour lines is 20 feet.
Contour lines close together have a large amount of elevation change.
Darker contour lines are Index and labeled contour.
An ‘X’ marks a spot elevation.

7. Contours - Slopes
How can you tell which side of the hill slope is highest?
Look at the contour lines ‘A’ and ‘B’
‘A’ is at elevation 7500 ft; ‘B’ is at elevation 7600 ft.
Traveling along line ‘C’ would be uphill; 100 ft elevation change.
Slope = Rise/Run

8. Contours - Direction of Flow
Water travels down gradient.
When contour lines identify a stream, they form a ‘V’ shape.
The ‘V’ always points upstream.

9. Contours – Hill Tops
Contour circle at ‘H’ shows that the land inside the circle is higher than the surrounding area.
‘F’ and ‘K’ are also high points.
Exception: At ‘I’ there are tiny tick marks that point to the inside of the circular shape. This is a depression with no outlet.