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Annual Soil Erosion by Wind on Cropland as a Proportion of the (T), 1997

Average Annual Soil Erosion by Wind on Cultivated Cropland as a Proportion of the Tolerable Rate (T), 1997

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Description

This map shows the 1997 actual soil erosion due to wind as a proportion of the tolerable rate (T) for each 8-digit hydrologic unit. Four legend categories show areas that are less than the tolerable rate, from one to two times the tolerable rate, two to four times the tolerable rate, and four or more times tolerable rate. Actual soil erosion rate is determined using the average annual Wind Erosion Equation (AAWEQ). This map excludes areas where cultivated cropland is less than 5% of the total surface area. Areas with 95% or more Federal area are shaded gray.

Cautions for this Product:
NRI maps reflect national patterns rather than site-specific information. This map does not show total erosion. 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: 8 Digit Hydrologic Unit Areas with Federal Land
Other Layers Displayed: States, Rivers


Definitions

Cultivated Cropland:
Includes land identified as being in row or close crops, summer fallow, aquaculture in crop rotation or other cropland not planted -- including cropland in short-term set-aside programs; or land in horticulture that is double cropped; or land in hay which had at least one of the three previous years in row or close grown crops; or land in pasture which had at least one of the three previous years in row or close grown crops.

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]

T-Factor:
The soil loss tolerance which can be used with the USLE or the WEQ. It is the maximum rate of annual soil erosion that will permit crop productivity to be sustained economically and indefinitely. [SSM]

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: 5152
Production Date: 1/25/01
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.