2.12: Determining Gradient

Determining Gradient

One of the most basic topographic observations that can be made is the gradient Links to an external site., or slope, of the ground surface.  High, or steep, gradients occur in areas where there is a large change in elevation over a short distance.  Low, or gentle, gradients occur where there is little change in elevation over the same distance.  Steep versus gentle are relative terms, meaning, what would be considered steep in some parts of the country might be considered gentle in another part.  However, gradients can still be compared between different parts of a map. The gradient can be determined through interpretation of the contour line spacing. For example, contour lines that are very close together signify steep terrain, whereas contours lines that are further apart indicate a flatter land surface (Figure 2.17). Gradient can also be determined mathematically using the following formula:

(elevation of point A - elevation of point B) / (distance from point A to point B)

 Gradient typically has units in feet per mile (ft/mi).