Revisions and updates to this layer include: None
SSURGO depicts information about soil features on or near the surface of the Earth. The data were collected as part of the National Cooperative Soil Survey.
The following is taken from the US Department of Agriculture, Soil Conservation Service, Technical Guide, Section II-A-2, June 1991, Hydric Soils, Union County, North Carolina.
Hydric Codes (HC): 1=Hydric soils, only because of saturation for a significant period during the growing season 2=Hydric soils that are frequently flooded for long or very long periods during the growing season 3=Hydric soils that are ponded for long or very long periods during the growing season
Vegetation Codes (VC): 1=Hydric soils that support woody vegetation under natural conditions 2=Hydric soils that do not support woody vegetation under natural conditions
Hydric soils in this county cannot be farmed under natural conditions without removing woody vegetation or hydrology manipulation.
Some map units and included soils listed as hydric soils in this county may not meet the definition of hydric soils and wetlands because the hydrology has been altered through drainage or other manipulations.
A.) Map units that are all hydric soils or have hydric soils as a major component: Map Unit Symbol HC VC Map Unit Name --------------- -- -- ------------- None B.) Map units with inclusions of hydric soils or have wet spots: Map Unit Map Unit Name Hydric HC VC Normal Symbol Inclusions Location Inclusion ----------- ------------- ---------- -- -- ---------- ChA (3A) Chewacla silt poorly 1 1 depressions loam, 0 to 2% drained along base of slopes, frequently soils upland slopes flooded CoA (14B) Colfax sandy poorly 1 1 depressions loam, 0 to 3% drained along drainageways slopes soils HeB (57B) Helena fine poorly 1 1 along drainageways sandy loam, drained depressions 2% to 8% soils slopes IrA (51A) Iredell loam poorly 1 1 depressions 0 to 3% slopes drained along drainageways soils ScA Secrest-Cid Complex poorly 1 1 depressions (18B, 10A) 0 to 6% slopes drained along drainageways soilsTo receive a copy of the Union County Soils Survey contact:
Craig Ditzler NRCS-Raleigh Office 4405 Bland Road, Suite 205 Raleigh, NC 27609 (919) 790-2905
This data set is not designed for use as a primary regulatory tool in permitting or citing decisions, but may be used as a reference source. This is public information and may be interpreted by organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application. Federal, State, or local regulatory bodies are not to reassign to the Natural Resources Conservation Service any authority for the decisions that they make. The Natural Resources Conservation Service will not perform any evaluations of these maps for purposes related solely to State or local regulatory programs.
Photographic or digital enlargement of these maps to scales greater than at which they were originally mapped can cause misinterpretation of the data. If enlarged, maps do not show the small areas of contrasting soils that could have been shown at a larger scale. The depicted soil boundaries, interpretations, and analysis derived from them do not eliminate the need for onsite sampling, testing, and detailed study of specific sites for intensive uses. Thus, these data and their interpretations are intended for planning purposes only. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.
NCCGIA Director, Karen Siderelis Database Administration, Zsolt Nagy Database Management, Ken Shaffer Project Manager, Zsolt Nagy North Carolina Center for Geographic Information and Analysis Governor's Office Office of State Planning 301 North Wilmington Street, Suite 700 Raleigh, NC 27601-2825
The Nutrient Sensitive Watershed Project supplied funding for the digital conversion.
Union County, North Carolina provided funding for the creation of this metadata.
The Survey was made cooperatively by:
The USDA-Natural Resources Conservation Service; the United States Dept. of Agriculture, Forest Service; the NC Department of Environment, Health and Natural Resources; North Carolina Agricultural Research Service; The North Carolina Cooperative Extension Service; the Union Soil and Water Conservation District; and the Union County Board of Commissioners.
Certain node/geometry and topology (GT) polygon/chain relationships are collected or generated to satisfy topological requirements. (The GT-polygon corresponds to the soil delineation). Some of these requirements include: chains must begin and end at nodes, chains must connect to each other at nodes, chains do not extend through nodes, left and right GT-polygons are defined for each chain element and are consistent throughout, and the chains representing the limits of the file (neatline) are free of gaps. The tests of logical consistency are performed using vendor software. Data within a specified tolerance of the neatline are snapped to the neatline.
All internal polygons are tested for closure with vendor software and are checked on hard copy plots. All data are checked for common soil lines (i.e., adjacent polygons with the same label). Quadrangles are edgematched within the soil survey area.
A map unit is a collection of areas defined and named the same in terms of their soil and/or nonsoil areas. Each map unit differs in some respect from all others in a survey area and is uniquely identified. Each individual area is a delineation. Each map unit consists of one or more components.
Soil scientists identify small areas of soils or nonsoil areas (special soil features) that have properties and behavior significantly different than the named soils in the surrounding map unit. Other inclusions that have a minimal effect on use and management, or those that could not be precisely located, were not mapped.
Specific limits were established on the classification of soils, design, and name of map units, location of special soil features, and the percentages of allowable inclusions. These limits are outlined in U.S. Department of Agriculture. 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. Soil Conserv. Serv., U.S. Dep. Agric. Handb. 436.; U.S. Department of Agriculture. 1992. Keys to Soil Taxonomy. SMSS Technical Monograph No. 19. Soil Surv. Staff, Soil Conserv. Serv.; U.S. Department of Agriculture. 1993. National Soil Survey Handbook, title 430-VI. Soil Surv. Staff, Soil Conserv. Serv.; and U.S. Department of Agriculture. 1993. Soil Survey Manual. Soil Surv. Staff, U.S. Dep. Agric. Handbook 18.
The actual composition and interpretive purity of the map unit delineations were based on statistical analysis of field observations and transect data. Adherence to National Cooperative Soil Survey standards and procedures is based on peer review, quality control, and quality assurance. Quality control is outlined in the memorandum of understanding for the soil survey area and in documents that reside with the Natural Resources Conservation Service state soil scientist. Four kinds of map units are used in soil surveys: consociations, complexes, associations, and undifferentiated groups.
Consociations - Consociations are named for the dominant soil. In a consociation, delineated areas are dominated by a single soil taxon and similar soils. At least one half of the pedons in each delineation are of the same soil components so similar to the named soil that major interpretations are not affected significantly. The total amount of dissimilar inclusions of other components in a map unit generally does not exceed about 15 percent if limiting and 25 percent if nonlimiting. A single component of dissimilar limiting inclusion generally does not exceed 10 percent if very contrasting.
Complexes and associations - Complexes and associations are named for two or more dissimilar components with the dominant component listed first. They occur in a regularly repeating pattern. The major components of a complex cannot be mapped separately at a scale of about 1:24,000. The major components of an association can be separated at a scale of about 1:24,000. In each delineation of either a complex or an association, each major component is normally present, though their proportions may vary appreciably from one delineation to another. The total amount of inclusions in a map unit that are dissimilar to any of the major components does not exceed 15 percent if limiting and 25 percent if nonlimiting. A single kind of dissimilar limiting inclusion usually does not exceed 10 percent.
Undifferentiated Groups - Undifferentiated groups consist of two or more components that do not always occur together in the same delineation, but are included in the same named map unit because use and management are the same or similar for common uses. Every delineation has at least one of the major components and some may have all of them. The same principles regarding proportion of inclusions apply to undifferentiated groups as to consociations.
Minimum documentation consists of three complete soil profile descriptions that are collected for each soil added to the legend, one additional per 3,000 acres mapped; three 10 observation transects for each map unit, one additional 10 point transect per 3,000 acres.
A defined standard or level of confidence in the interpretive purity of the map unit delineations is attained by adjusting the kind and intensity of field investigations. Field investigations and data collection are carried out in sufficient detail to name map units and to identify accurately and consistently areas of about 5 acres.
The accuracy of these digital data is based upon their compilation to basemaps that meet National Map Accuracy Standards. The difference in positional accuracy between the soil boundaries and special soil features locations in the field and their digitized map locations is unknown. The locational accuracy of soil delineations on the ground varies with the transition between map units.
For example, on long gently sloping landscapes the transition occurs gradually over many feet. Where landscapes change abruptly from steep to level, the transition will be very narrow. The digital map elements are edge matched between data sets. The data along each quadrangle edge are matched against the data for the adjacent quadrangle.
A polygon coverage depicting soils as classified by the US Dept. of Agriculture-Natural Resources Conservation Service. The polygon attribute table (PAT) has attribute data including total area in coverage units, (square feet) total perimeter (linear feet), polygon internal identification number, polygon user identification number, the NRCS abbreviation for soil type, and the NRCS classification of soil hydric properties.
UNCODSL.PAT Polygon Attribute Table COLUMN ITEM NAME WIDTH OUTPUT TYPE DEC DESCRIPTION 1 AREA 4 12 F 3 Total area in feet 5 PERIMETER 4 12 F 3 Total perimeter in feet 9 UNCODSL# 4 5 B - Poly internal id number 13 UNCODSL-ID 4 5 B - Poly user id number 17 DSL-NAME 6 7 C - NRCS abbreviation for soil type 23 HYDRIC 1 2 C - NRCS classification of soil hydric properties UNCODSL.AAT Arc Attribute Table COLUMN ITEM NAME WIDTH OUTPUT TYPE DEC DESCRIPTION 1 FNODE# 4 5 B - From-node id of linear feature 5 TNODE# 4 5 B - To-node id of linear feature 9 LPOLY# 4 5 B - Left-side polygon id of linear feature 13 RPOLY# 4 5 B - Right-side polygon id of linear feature 17 LENGTH 4 12 F 3 Length of linear feature in feet 21 UNCODSL# 4 5 B - Internal id number 25 UNCODSL-ID 4 5 B - Internal id number 29 ATYPE 4 5 B - Arc type