How to Read Topographic Maps

BAE 3313Natural Resources Engineering

Sourcehttp://www.cis.ksu.edu/~dha5446/topoweb/guide.html

How is a Watershed?

The total land area that contributes water to a stream, river or lake.

Source: http://www.epa.gov/owow/watershed/whatis.html

What is a Topographic Map?1. Shows elevation data for a small piece of the

earth2. Shows physical and manmade features3. 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

1:250,0004. Amount of detail shown on a map is proportional

to the map scale 1:24,000 - high detail 1:100,000 - moderate detail 1:250,000 - low detail

1:24,000 Topographic Map1. Covers 7.5 minutes of latitude by 7.5 minutes of

longitude2. Approximately equal to 8 miles north-south and 6

miles east-west3. One map called a quadrangle or “quad”4. 28 inches long by 21 inches wide5. Purchase from USGS or most outdoor stores

Cultural and Physical Symbols

Forest: Shown in greenUnforested: White; May be grass, soil, or some other surfaceRoads: Two parallel lines; Unbroken lines indicate paved roads, broken lines unpavedTrails: Dashed linesStreams and Rivers: Thin lines for streams, large blue area for larger riversLake: Solid blue areaMarshy Area: Blue symbols enclosed by blue dashed lineBuildings: Building shapes shown, may be filled or unfilledUTM Grid Lines: Especially useful for GPS, each grid square is 1 km x 1 km

Contours

1. Contour lines are continuous brown lines. Each line represents a specific elevation, and all locations along that line have the exact same elevation.

2. "Contour Interval 20 Feet" means that the elevation change between contour lines is 20 feet.

3. Contour lines close together have a large amount of elevation change.4. Darker contour lines are Index and labeled contour.5. An ‘X’ marks a spot elevation.

Contours - Slopes

1. How can you tell which side of the hill slope is highest?2. Look at the contour lines ‘A’ and ‘B’3. ‘A’ is at elevation 7500 ft; ‘B’ is at elevation 7600 ft.4. Traveling along line ‘C’ would be uphill; 100 ft elevation change.5. Slope = Rise/Run

Contours - Direction of Flow

1. Water travels down gradient.2. When contour lines identify a stream, they form a ‘V’ shape.3. The ‘V’ always points upstream.

Contours – Hill Tops

1. Contour circle at ‘H’ shows that the land inside the circle is higher than the surrounding area.

2. ‘F’ and ‘K’ are also high points.3. Exception: At ‘I’ there are tiny tick marks that point to the inside of

the circular shape. This is a depression with no outlet.