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