1987 Wetland Delineation Manual - The Wetlands Regulation Center
1987 Wetland Delineation Manual - The Wetlands Regulation Center
1987 Wetland Delineation Manual - The Wetlands Regulation Center
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<strong>Wetland</strong> Delination <strong>Manual</strong>, <strong>1987</strong> 31<br />
present. NWI “User Notes” are available that correlate the classification system with local<br />
wetland community types. An important feature of this classification system is the water<br />
regime modifier, which describes the flooding or soil saturation characteristics. <strong>Wetland</strong>s<br />
classified as having a temporarily flooded or intermittently flooded water regime should be<br />
viewed with particular caution since this designation is indicative of plant communities that are<br />
transitional between wetland and nonwetland. <strong>The</strong>se are among the most difficult plant<br />
communities to map accurately from aerial photography. For wetlands “wetter” than<br />
temporarily flooded and intermittently flooded, the probability of a designated map unit on<br />
recent NWI maps being a wetland (according to Cowardin et al. 1979) at the time of the<br />
photography is in excess of 90 percent. CAUTION: Due to the scale of aerial photography<br />
used and other factors, all NWI map boundaries are approximate. <strong>The</strong> optimum use of NWI<br />
maps is to plan field review (i.e. how wet, big, or diverse is the area?) and to assist during field<br />
review, particularly by showing the approximate areal extent of the wetland and its association<br />
with other communities. NWI maps are available either as a composite with, or an overlay for,<br />
USGS base maps and may be obtained from the NWI Central Office in St. Petersburg, Fla., the<br />
<strong>Wetland</strong> Coordinator at each FWS regional office, or the USGS.<br />
(2) Plant database. This database of approximately 5,200 plant species that occur in wetlands<br />
provides information (e.g., ranges, habitat, etc.) about each plant species from the technical<br />
literature. <strong>The</strong> database served as a focal point for development of a national list of plants that<br />
occur in wetlands (Appendix C, Section 1).<br />
c. Soil surveys. Soil surveys are prepared by the SCS for political units (county, parish, etc.)<br />
in a state. Soil surveys contain several types of information:<br />
(1) General information (e.g. climate, settlement, natural resources, farming, geology, general<br />
vegetation types).<br />
(2) Soil maps for general and detailed planning purposes. <strong>The</strong>se maps are usually generated<br />
from fairly recent aerial photography. CAUTION: <strong>The</strong> smallest mapping unit is 3 acres, and a<br />
given soil series as mapped may contain small inclusions of other series.<br />
(3) Uses and management of soils. Any wetness characteristics of soils will be mentioned<br />
here.<br />
(4) Soil properties. Soil and water features are provided that may be very helpful for wetland<br />
investigations. Frequency, duration, and timing of inundation (when present) are described for<br />
each soil type. Water table characteristics that provide valuable information about soil<br />
saturation are also described. Soil permeability coefficients may also be available.<br />
(5) Soil classification. Soil series and phases are usually provided. Published soil surveys will<br />
not always be available for the area. If not, contact the county SCS office and determine<br />
whether the soils have been mapped.<br />
25 February 1997 Environmental Techncal Services Co. 834 Castle Ridge Rd Austin, Texas 78746