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> 69<br />
bring nonwetland areas having wetzand indicators of two, but not all three, parameters into<br />
Section 404 jurisdiction.<br />
a. <strong>Wetland</strong>s on drumlins. Slope wetlands occur in glaciated areas Tn-which thin soils cover<br />
relatively impermeable glacial till or in which layers of glacial till have different hydraulic<br />
conditions that produce a broad zone of ground-water seepage. Such areas are seldom, if ever,<br />
flooded, but downslope groundwater movement keeps the soils saturated for a sufficient<br />
portion of the growing season to produce anaerobic and reducing soil conditions. This fosters<br />
development of hydric soil characteristics and selects for hydrophytic vegetation. Indicators of<br />
wetland hydrology may be lacking during the drier portion of the growing season.<br />
b. Seasonal wetlands. In many regions (especially in western states), depression areas occur<br />
that have wetland indicators of all three parameters during the wetter portion of the growing<br />
season, but normally lack wetland indicators of hydrology and/or vegetation during the drier<br />
portion of the growing season. Obligate hydrophytes and facultative wetland plant species<br />
(Appendix C, Section 1 or 2) normally are dominant during the wetter portion of the growing<br />
season, while upland species (annuals) may be dominant during the drier portion of the<br />
growing season. <strong>The</strong>se areas may be inundated during the wetter portion of the growing<br />
season, but wetland hydrology indicators may be totally lacking during the drier portion of the<br />
growing season. It is important to establish that an area truly is a water body. Water in a<br />
depression normally must be sufficiently persistent to exhibit an ordinary high-water mark or<br />
the presence of wetland characteristics before it can be considered as a water body potentially<br />
subject to Clean Water Act jurisdiction. <strong>The</strong> determination that an area exhibits wetland<br />
characteristics for a sufficient portion of the growing season to qualify as a wetland under the<br />
Clean Water Act must be made on a case-by-case basis. Such determinations should consider<br />
the respective length of time that the area exhibits upland and wetland characteristics, and the<br />
manner in which the area fits into the overall ecological system as a wetland. Evidence<br />
concerning the persistence of an area's wetness can be obtained from its history, vegetation,<br />
soil, drainage characteristics, uses to which it has been subjected, and weather or hydrologic<br />
records.<br />
c. Prairie potholes. Prairie potholes normally occur as shallow depressions in glaciated<br />
portions of the north-central United States. Many are landlocked, while others have a drainage<br />
outlet to streams or other potholes. Most have standing water for much of the growing season<br />
in years of normal or above normal precipitation, but are neither inundated nor have saturated<br />
soils during most of the growing season in years of below normal precipitation. During dry<br />
years, potholes often become incorporated into farming plans, and are either planted to row<br />
crops (e.g. soybeans) or are mowed as part of a haying operation. When this occurs, wetland<br />
indicators of one or more parameters may be lacking. For example, tillage would eliminate<br />
any onsite hydrologic indicator, and would make detection of soil and vegetation indicators<br />
much more difficult.<br />
d. Vegetated flats. In both coastal and interior areas throughout the Nation, vegetated flats are<br />
often dominated by annual species that are categorized as OBL. Application of procedures<br />
25 February 1997 Environmental Techncal Services Co. 834 Castle Ridge Rd Austin, Texas 78746