What Is Elevation in Soil?

Measuring Elevation

• The majority of soil elevation measurements are in millimeters or even fractions thereof, depending on the area of inquiry. From pin-sets to laser beams to chains, instrument designers strain to provide accuracy at ever-smaller depths and heights. Instrumentation used determines the meaning of measurements. Soil height may be measured from a fixed area, such as a rock or frozen ground, under the soil. Soil measurements may be taken with instruments reflecting contours of accumulation. Soil elevation may put less emphasis on slope and more on the minute details of what laymen would call soil texture.

Slope

• Slope or pitch is one of the elements of soil elevation. Techniques focus on building slopes out of long sequences of stationary measurements; FAO measurement practices for designing irrigation specify five to 10 fixed points no more than 2 to 3 meters apart. Without measurements of slope, amounts of water needed and the rate at which they can be absorbed make it impossible to irrigate effectively.

Erosion and Flooding Concerns

• Measurements taken to determine the relationship between soil and excess water can be both large and very small. Over a watershed area, soil studies of absorbency need to be done at numerous elevations, not just in the immediate runoff or flooded area, because of the soil characteristics differ at different elevations. Measurements of soil elevations surrounding a potential building site, not just soil onsite, contribute to determining whether the site may be part of a flood plain.

Environmental Preservation Issues

• Measurement of soil elevations is critical to evaluating the impact of floods, hurricanes and other major water-related events on landforms. A three-year hydrology study of the Shark River mangrove swamp area in Southern Florida was able to furnish information about a fragile ecosystem lifecycle, including the surprisingly beneficial effects of Hurricane Wilma. Quantifying soil accretion, erosion and related plant behavior contributes to preservation of many delicately-balanced water ecosystems. Correlations between increased atmospheric CO2 and rising soil elevations in Chesapeake Bay marshes serve as another indicator of the complex natural interrelationships that characterize wetlands.

Agricultural Concerns

• The University of Nebraska Soil Carbon Sequestration Program uses elevation as one of the components of soil carbon content, an index of potential nutritive value. Soil rich in carbon offers good nutrition to crops. Extremely small and frequent changes in soil elevation, in lay terms, roughness, serve as an index of how well soil will process water and provide nutrients.These minute variations in elevation present a considerable measurement challenge. One of the latest technologies involves highly sophisticated shadow-study as a predictor of soil qualities. The pictures it offers remind viewers of how long farmers have visually surveyed their land, anticipating fertility, planning irrigation, and preventing erosion by water and wind.