Total Wind and Water Erosion, 1997
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.
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