Acres of Highly Erodible Cropland, 1997
This dot density map shows the total number of 1997 highly erodible cropland acres. Dots are aggregated by and placed randomly within 8-digit hydrologic units. Each red dot represents 25,000 acres of highly erodible cropland. Areas with 95% or more Federal area are shaded gray. There are 104 million acres of highly erodible cropland in the U.S. For comparison with non- highly erodible cropland, see map #4969
Cautions for this Product:
See definition of Highly Erodible Land. This map may not be used to determine site-specific information. Within an 8-digit hydrologic unit, dot counts represent acreage totals correctly plus or minus one dot to account for remainders. 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.
Source: National Resources Inventory, 1997
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.
Aggregate Layer: Cross of State with 8 Digit Hydrologic Units and Federal Land
Other Layers Displayed: States, Rivers
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]
Erodibility Index (EI):
The soil erodibility index (EI) provides a numerical expression of the potential for a soil to erode considering the physical and chemical properties of the soil and the climatic conditions where it is located. The higher the index, the greater the investment needed to maintain the sustainability of the soil resource base if intensively cropped. It is defined to be the maximum of (RxKxLS)/T (from the Universal Soil Loss Equation) and (CxI)/T (from the Wind Erosion Equation), where R is a measure of rainfall and runoff, K is a factor of the susceptability of the soil to water erosion, LS is a measure of the combined effects of slope length and steepness, C is a climatic characterization of windspeed and surface soil moisture and I is a measure of the susceptability of the soil to wind erosion. Erodibility Index scores equal to or greater than 8 are considered highly erodible land. (NRI, 1992)
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]
A land ownership class designating land that is owned by the Federal Government. It does not include, for example, trust lands administered by the Bureau of Indian Affairs nor Tennessee Valley Authority (TVA) land. No data are collected for any year that land is in this ownership. [NRI-97]
Highly Erodible Land (HEL):
Land that has an erodibility index of eight or more (NFSAM).
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]
Product ID: 4970
Production Date: 12/4/00
Product Type: Map
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