The horizontal distance between points A and B can be measured with a scaled ruler and used to determine the slope percent.Įxample 4 - What is the slope percent in Exercise 2 above?įor this computation, the rise, or vertical ground distance, and run, or horizontal ground distance, are needed. Notice the tick marks pointing toward lower elevation. The figure above illustrates a depression and its representation using contour lines. (b) Notice how a mountain saddle, a ridge, a stream, a steep area, and a flat area are shown with contour lines. The figure above illustrates various topographic features. Contour lines that are very close together indicate a steep slope. Widely separated contour lines indicate a gentle slope. The peak is normally considered to be located at half the interval distance. Note: The intervals are increasing, therefore, the contours indicate a hill. From the contour map, a profile can be drawn of the terrain.Įxample 2 - Draw a profile showing the elevations of the contours. The even spacing indicates the hill has a uniform slope. The contour lines in this figure are equally spaced. Pick two contour lines that are next to each other and find the difference in associated numbers. Sharp contour points indicate pointed ridges.Įxample 1 - In the graphic below, what is the vertical distance between the contour lines? Contour lines tend to enclose the smallest areas on ridge tops, which are often narrow or very limited in spatial extent. A rounded contour indicates a flatter or wider drainage or spur.

They then cross the stream and turn back along the opposite bank of the stream forming a 'v'. As a contour approaches a stream, canyon, or drainage area, the contour lines turn upstream. If the numbers associated with the contour lines are decreasing, there is a decrease in elevation. If the numbers associated with specific contour lines are increasing, the elevation of the terrain is also increasing. Index contours are bold or thicker lines that appear at every fifth contour line. A contour interval is the vertical distance or difference in elevation between contour lines. A contour line is a line drawn on a topographic map to indicate ground elevation or depression.

Contour line definition science