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Total Wind and Water Erosion, 1997

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Description

This dot map shows tons of erosion due to wind and water on cropland and CRP land. Each blue dot represents 200,000 tons of average annual erosion due to water (1,068 million tons per year). Each red dot represents 200,000 tons of average annual erosion due to wind (840.5 million tons per year). The combined erosion for the U.S. is 1.9 billion tons per year. Data are aggregated by 8-digit hydrologic unit. The Universal Soil Loss Equation (USLE) is used to calculate water erosion. The Average Annual Wind Erosion Equation (AAWEQ) is used to calculate wind erosion. Areas with 95% or more Federal area are shaded gray. Sheet and Rill (water) erosion mostly occurs in areas east of the Corn Belt and Southern Plains. Wind erosion is mostly in the West, Northern Plains, Southern Plains, and parts of the Corn Belt. Several parts of the country battle difficult problems with both wind and water erosion.

Cautions for this Product:
Erosion by water includes sheet and rill erosion and excludes gully erosion. Within an 8-digit hydrologic unit, dot counts represent totals correctly plus or minus one dot to account for remainders. This map does not show the rate at which erosion is occuring. This map does not show erosion that is occuring on land other than cropland and CRP land. Data are not collected on Federal land. Data are not available for Alaska or the Pacific Basin. Data for Puerto Rico and the U.S. Virgin Islands are aggregated by 6-digit hydrologic unit.



Sources

Source: National Resources Inventory, 1997
Distributor: USDA-NRCS-RIAD
Reliability:
NRI sample data are generally reliable at the 95% confidence interval for state and certain broad substate area analyses. Generally, analyses that aggregate data points by smaller geographic areas and/or more specific criteria result in fewer data points for each aggregation and therefore less reliable estimates. NRI maps reflect national patterns rather than site- specific information.


Layers

Aggregate Layer: Cross of State with 8 Digit Hydrologic Units and Federal Land
Other Layers Displayed: States, Rivers


Definitions

Conservation Reserve Program (CRP):
A Federal program established under the Food Security Act of 1985 to assist private landowners to convert highly erodible cropland to vegetative cover for 10 years. [NMCSP]

Cropland:
A Land cover/use category that includes areas used for the production of adapted crops for harvest. Two subcategories of cropland are recognized: cultivated and noncultivated. Cultivated cropland comprises land in row crops or close-grown crops and also other cultivated cropland, for example, hayland or pastureland that is in a rotation with row or close-grown crops. Noncultivated cropland includes permanent hayland and horticultural cropland. [NRI-97]

Erosion:
The wearing away of the land surface by running water, waves, or moving ice and wind, or by such processes as mass wasting and corrosion (solution and other chemical processes). The term "geologic erosion" refers to natural erosion processes occurring over long (geologic) time spans. "Accelerated erosion" generically refers to erosion that exceeds what is presumed or estimated to be naturally occurring levels, and which is a direct result of human activities (e.g., cultivation and logging). [NSSH-96]

Gully erosion:
The erosion process whereby water concentrates in narrow channels and, over short periods, removes the soil from this narrow area to considerable depths, ranging from 1 to 2 feet to as much as 75 to 100 feet. [NRI-97]

Hydrologic units:
A hierarchical system developed by the U.S. Geological Survey that divides the United States and the Caribbean into 21 major regions, 222 subregions, 352 accounting units, and further subdivided into 2,150 cataloging units that delineate river basins having drainage areas usually greater than 700 square miles. [USGS]

Sheet and rill erosion:
Removal by runoff water of a fairly uniform, usually imperceptible, thin layer of soil often accompanied by formation of many small eroding channels. Rills are only a few inches deep and do not hinder farm machinery. Tillage erases them, but they tend to recur after heavy rain during the growing season, especially where cover is limited. [SSM]

Universal soil loss equation (USLE):
This equation estimates average annual soil loss from sheet and rill erosion. Location specific data for the field in which the NRI point falls or that portion of the field surrounding the point that would be considered in conservation planning are used in the NRI calculations. The equation is: A = RKLSCP, where A is the computed soil loss per unit area, R is a rainfall factor, K is a soil erodibility factor, L is a slope length factor, S is a slope- steepness factor, C is a cover and management factor, and P is a conservation practice factor. [NAM]

Water Erosion:
The process of detachment, transport and deposition of soil in which the primary agent is water. This may include sheet, rill and gully erosion; however, for the purposes of this analysis, unless otherwise stated, water erosion refers only to sheet and rill erosion and excludes gully erosion.

Wind erosion:
The process of detachment, transport, and deposition of soil by wind. [NAM]

Wind erosion equation (WEQ):
An erosion model designed to predict long-term average annual soil losses from a field having specific characteristics (NAM). E= f(IKCLV) where E is the estimated average annual soil loss expressed in tons per acre per year; I is the soil erodibility; K is the soil ridge roughness factor; C is the climatic factor; L is the equivalent unsheltered distance across the field along the prevailing wind erosion direction; and V is the equivalent vegetative cover. [NAM]


Product Information

Product ID: 5112
Production Date: 12/5/00
Product Type: Map


For additional information contact the Resources Inventory and Assessment Division. Please include the Product ID you are inquiring about. nri@wdc.usda.gov or 1400 Independence Avenue SW - P.O. Box 2890 - Washington D.C. 20013. If you use our analysis products, please be aware of our disclaimer.