Technical Report

 
15. Soil slope
Soil slope has a number of distinct properties: gradient, length, aspect, and surface configuration.
Slope influences many aspects of soil development, such as water movement, runoff, erosion, and 
other factors.
Slope gradient is the slant or inclination of the soil surface from the horizontal. Slope gradient is 
usually determined with a hand level or clinometer.
For example, if the difference in elevation is 1 meter over a horizontal distance of 100 meters, the 
slope is 1 percent. Some of the terms used to describe a slope gradient are level, gently sloping, and 
steeply sloping. Slope length is a term describing how 'long' or 'short' a slope extends over the local 
physiography.
Slope aspect is the compass direction in which the soil surface faces.
It is expressed as an angle between 0 and 360 degrees measured clockwise from true north. Slope 
aspect is important in terms of amount of exposure to the sun.
South-facing slopes receive more solar radiation in the northern hemisphere than do north-facing 
slopes.
Surface configuration describes the shape of the local landscape. An alluvial fan and the shoulder of a 
ridge both have a convex slope, in which the gradient increases downslope. Foot slopes have a 
concave slope in which the gradient decreases downslope.
 
16. Vegetation
In a site evaluation, an estimate should be made of the kinds and amounts of natural vegetation 
present.
The vegetation present is closely related to the genesis of the soil. A note should be made of 
vegetation even if the area has been disturbed by cropping, grazing, timbering, strip mining, or other 
practices. Notes of this kind can help to clarify or even discover plant-soil relationships.
Recognition of plant communities and knowledge of soil-plant relationships can aid in the 
identification of soil boundaries.