- 17. Geologic type: A national map of bedrock geology at 1:2,500,000-scale resolution is
available from GIS data bases. Identify up to three of the spatially
dominant geologic rock units (units are based on age and kind; see King
and Beikman, 1974) within the basin and report the percentage of the
basin upstream of the reference location occupied by each. The national
coverage scale (1:2,500,000) is provided; record the local coverage scale
of the highest resolution available.
- 18. Soil type: Two soil-type data bases are available through the Soil
Conservation Service: the National Soil Geographic Data Base (NATSGO) and
the State Soil Geographic Data Base (STATSGO). Each represents a
different resolution of soil mapping, but each data base is linked to soil interpretations that
provide information on the proportionate extent of component soils and
their properties. Attributes include particle-size distribution, bulk
density, available water capacity, soil reaction, salinity, and percentage
of organic matter. The NATSGO data base provides a general description of
soils, based on major land-resource area boundaries which were developed
from State general soil maps. The NATSGO map is available in ARC/INFO
format at 1:7,500,000-scale resolution. The STATSGO data base is derived
from soil survey maps and, where soil surveys are unavailable, geology,
topography, vegetation, and climate data are used with satellite imagery
to classify soils. These data are compiled by State at 1:250,000-scale
resolution. Identify up to three of the spatially dominant soil types
within the basin upstream of the reference location and report the
percentage of the drainage area occupied by each. The national coverage
scale (1: 7,500,000) and the local coverage scale (1:250,000) for STATSGO
data are provided.
- 19. Potential natural vegetation: Potential natural vegetation is defined as vegetation that
would exist today if man were removed from the scene (Kuchler, 1970).
Characterizing potential natural vegetation provides important baseline
information for evaluating the influence of human activities on vegetation
within a basin. A classification of potential natural vegetation is based
on whether plants are woody or herbaceous. If woody, they are further
classified as broadleaf or n eedleleaf, evergreen or deciduous. For these
vegetation classes, dominant species are listed. National coverage data
on potential natural vegetation is available from GIS data bases at
1:3,100,000-scale resolution. Record up to three of the spatially d
ominant types of potential natural vegetation for the basin upstream of
the reference location and the percentage of the drainage area that each
occupies. The national coverage scale (1:3,100,000) is provided; record
the local coverage scale of the highe st resolution
available.
- 20. Wetlands: The U.S. Fish and Wildlife Service's National
Wetlands Inventory is designed to determine
the status of and trends in wetlands throughout the United States (Frayer
and others, 1983; Dahl and Johnson, 1991). Wetlands are defined on the
basis of plant types, soils, and frequency of flooding. The map is
structured using a hierarchical classification, with the highest levels
described as Marine, Estuarine, Riverine, Lacustrine, or Palustrine. Each
of these systems has subs ystems for which classes are identified on the
basis of substrate material and flooding regime or vegetative form.
Approximately 70 percent of wetlands in the United States have been mapped
at 1:24,000-scale resolution. Approximately 20 percent of compiled
1:24,000-scale resolution maps have been digitized and are available in
the Map Overlay Statistical System (MOSS) format. Identify up to three of
the spatially dominant wetland types within the basin upstream of the
reference location and report the percentage of the drainage area occupied
by each. The national coverage scale