4
Wetland Delineation: Past and Current Practice

INTRODUCTION

Technical manuals that provide agency wide guidance on wetland delineation are a relatively recent arrival in federal wetlands programs. Before 1986, none of the federal agencies with regulatory responsibilities—the U.S. Army Corps of Engineers (USACE), the Environmental Protection Agency (EPA), the Natural Resources Conservation Service (NRCS) (formerly the Soil Conservation Service [SCS])—had adopted a uniform technical manual or formal rules for delineation. Instead, the agencies used local and national aids, including draft and proposed manuals and district guidance documents, to assist individuals charged with delineating wetlands. In the late 1980s, each agency adopted its own delineation manual and then worked on the 1989 interagency manual. The manuals were intended to ensure consistent regulation of wetlands.

A delineation manual is not meant to define a wetland, but rather to aid a delineator in applying a definition of wetland; the manual gives details about what constitutes a wetland that must be confirmed during delineation. The complementarity of a regulatory definition and a delineation manual can be shown by juxtaposing the key words of the USACE regulatory definition with the implicit issues that each word raises (in bold):

Those areas (distinguish wetland from upland)

that are inundated (specify depth)

or saturated (interpret proximity to surface, water table)

by surface or ground water (assess water source)



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Wetlands: Characteristics and Boundaries 4 Wetland Delineation: Past and Current Practice INTRODUCTION Technical manuals that provide agency wide guidance on wetland delineation are a relatively recent arrival in federal wetlands programs. Before 1986, none of the federal agencies with regulatory responsibilities—the U.S. Army Corps of Engineers (USACE), the Environmental Protection Agency (EPA), the Natural Resources Conservation Service (NRCS) (formerly the Soil Conservation Service [SCS])—had adopted a uniform technical manual or formal rules for delineation. Instead, the agencies used local and national aids, including draft and proposed manuals and district guidance documents, to assist individuals charged with delineating wetlands. In the late 1980s, each agency adopted its own delineation manual and then worked on the 1989 interagency manual. The manuals were intended to ensure consistent regulation of wetlands. A delineation manual is not meant to define a wetland, but rather to aid a delineator in applying a definition of wetland; the manual gives details about what constitutes a wetland that must be confirmed during delineation. The complementarity of a regulatory definition and a delineation manual can be shown by juxtaposing the key words of the USACE regulatory definition with the implicit issues that each word raises (in bold): Those areas (distinguish wetland from upland) that are inundated (specify depth) or saturated (interpret proximity to surface, water table) by surface or ground water (assess water source)

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Wetlands: Characteristics and Boundaries at a frequency (apply recurrence threshold) and duration (apply duration threshold) sufficient to support (identify requirements of vegetation) and that under normal circumstances (adjust for altered conditions) do support a prevalence (assess prevalence) of vegetation (consider entire community) typically adapted (categorize species) for life (distinguish long term persistence from short term presence) in saturated (relate vegetation and saturation) soil conditions (characterize soils). This chapter summarizes the ways regulatory agencies have developed, interpreted, and applied such definitions. WETLAND DELINEATION: MOTIVATION AND PROCEDURE Wetlands are delineated primarily because property owners need to know which parts of their land could be within the regulatory jurisdiction of one or more federal statutes. As explained in Chapter 3, the primary regulatory programs arise under the Clean Water Act (CWA), which is administered by USACE and EPA, and the Food Security Act (FSA), which is administered by the NRCS. Some states also have wetland protection programs that require landowners to know the boundaries of wetlands on their properties. Although the U.S. Fish and Wildlife Service (FWS) is responsible for developing maps for the National Wetland Inventory (NWI), the inventory does not have regulatory effect, and it was not intended or designed for use in delineation. Other state and federal programs require wetland delineations as well; these include rules that tax undeveloped and developed property at different rates. Clean Water Act Wetlands are protected by the CWA (P.L. 95-217) and are subject to the act's prohibition against filling without a permit. The act's physical jurisdiction is defined in the statute and in its regulations. The act applies to ''navigable waters,'' which the statute defines as "waters of the United States" (33 U.S.C. § 1362(7)). As explained in Chapter 3, USACE and EPA, acting in response to the Calloway decision as reflected in the 1977 CWA amendments, now regard waters of the United States to include wetlands and other bodies of water (33 C.F.R. §§ 328.3(a), (b); 40 C.F.R. §§ 230.3(s), 230.41). The CWA wetland protection feature is the statutory prohibition against discharging materials into U.S. waters without a permit (33 U.S.C. § 1311(a)). The permit program for discharges of fill material is established in Section 404 (33 U.S.C. § 1344) and administered by USACE.

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Wetlands: Characteristics and Boundaries Although USACE has administrative responsibility for Section 404, ultimate authority for determining the act's reach rests with EPA. In 1979, the U.S. Attorney General decided that, in light of the more extensive responsibility that EPA has under the CWA, it, and not USACE, should have final authority in deciding for the areal extent of the law's jurisdiction (43 Op. Att'y Gen. 15, 1979). USACE and EPA (1979) have entered into a memorandum of agreement (MOA) on delineation authority, which specifies that USACE will make most jurisdictional determinations in administering Section 404. EPA reserves the authority to determine jurisdiction in special cases, which it may designate either in generic or in project-specific instances. Jurisdictional determinations—or wetland delineations—made by either agency are binding on the other. Final jurisdictional determinations must be written and must be signed either by an EPA regional administrator or by a USACE district engineer. In the event of a disagreement, final authority rests with EPA. Either USACE or EPA can make wetland delineations, but the responsibility for determining and knowing the boundaries of wetlands rests on the regulated entities (Want, 1989). A private party may request that USACE conduct a jurisdictional delineation (33 C.F.R. § 325.9), but USACE does so at its own discretion. Because many USACE offices lack the resources to provide timely responses to delineation requests, most entities pay private consultants to do them. A USACE delineation is valid for 3 years, although a period of up to 5 years may be justified by appropriate information (Regulatory Guidance Letter 90-06, 57 Fed. Reg. 6591; 1992). The CWA and federal regulations establish a process for evaluating whether a person should be authorized to fill wetlands. In Section 404(f), the statute exempts certain filling activities, such as normal agriculture and silviculture, and minor filling associated with some construction activities such as temporary roads. In addition, some filling is authorized by general permits that are applicable nationwide. These general permits establish criteria for amount of filling and other management practices. As long as a person complies with the general permit criteria, no other authorization is required. If an individual permit is necessary, the permit application is evaluated under standards set out in EPA and USACE regulations. EPA's regulations, which are the 404 (b)(1) guidelines, establish environmental standards for issuance or permits. USACE regulations, which are known as the public interest standards, require evaluation of a broad range of environmental and legal criteria. USACE regulations also establish the procedures for consideration of permits, including public notice of permits and application of the National Environmental Policy Act. A wetland delineation is often requested or contracted by a property owner who needs to know restrictions on the development or use of the land. In particular, a property owner might need a delineation when seeking an individual or nationwide permit. Nationwide permits, or "permits by rule," authorize filling of relatively small areas if the permitted activity is consistent with CWA regula-

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Wetlands: Characteristics and Boundaries tions. For example, some nationwide permits cover modest bank stabilization or utility line backfill and bedding, or filling of wetlands in hydrologically isolated areas or headwaters (Chapter 6). A nationwide permit does not require an application if the activity is consistent with the scope of the permit, and if the activity can be expected to have minimal effect individually or in combination with other related activities. Some nationwide permits require landowners to file a predischarge notification, which includes a wetland delineation for review by USACE. USACE regulations encourage all permit applicants to consult with a USACE district office before making an application so that jurisdictional limits can be clarified (33 C.F.R. § 325.1(b)), and federal or state agencies can comment. Permits are generally valid from 3 to 5 years after issuance, and a wetland delineation that is made in connection with a permit is valid for the term of the permit. The EPA may conduct a wetland delineation when it designates an area as a special case under the 1989 MOA. The EPA also has discretionary authority to identify wetlands in advance of any permit application through its program for advanced identification of wetlands (40 C.F.R. § 230.80; see Chapter 10). The program does not substitute for individual permit review, however. Instead, it categorizes wetlands either as suitable or as generally unsuitable for filling. The designations developed through the program are not binding in the review of a permit application. Not all activities under Section 404 are regulatory. Inventory and non-regulatory protection of wetlands are examples of Section 404 activities that extend beyond permitting. The Food Security Act The Food Security Act of 1985 and its 1990 amendments established two conservation programs for the protection of wetlands: the "swampbuster" program and the wetland reserve program (16 U.S.C. §§ 3801-3862). Rather than prohibiting filling activities as the CWA does, the FSA specifies incentives and penalties to protect wetlands, and its programs require wetland delineations. The methods for delineation under FSA have been different from those of the CWA, although efforts are under way to create some concordance between the two. NRCS, which is part of the U.S. Department of Agriculture, has primary responsibility for the FSA conservation provisions. The Agricultural Stabilization and Conservation Service (ASCS) also has FSA duties, however. NRCS does the wetland delineations; ASCS decides on the eligibility of farmers for exemptions. Each agency operates through local and county offices. Both the CWA and FSA regulate agricultural activities. The CWA, however, exempts most routine agricultural practices from the Section 404 permit requirement. Exemptions include plowing; seeding; cultivating; and minor drainage associated with production of food, fiber, or forest products; construction or maintenance of farm or stock ponds or ditches; maintenance of drainage ditches;

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Wetlands: Characteristics and Boundaries and farm road construction or maintenance (33 U.S.C. § 1344(f). The scope of these CWA Section 404 exemptions has been litigated frequently, and the courts have generally construed the exemptions narrowly: United States v. Huebner, 752 F.2d 1235 (7th Cir., 1985); United States v. Akers, 785 F.2d 814 (9th Cir., 1986). Converting wetlands to new uses as farmland is not within the scope of the Section 404 exemptions: United States v. Cumberland Farms of Connecticut, Inc., 826 F.2d 1151, 1st Cir., 1987 (conversion to cranberry bogs is an illegal change of uses); Hobbs v. United States, 947 F.2d 941, 4th Cir., 1991 (conversion of wetland to hayfield is illegal). The FSA wetland reserve program authorizes the federal government to purchase 10-year easements on wetlands, and it stipulates that the wetlands must be maintained in their natural state. The swampbuster provision of the law, in contrast, makes farmers who convert wetland acreage to cropland after Dec. 23, 1985, ineligible for agricultural subsidies—price supports, loans, or crop insurance, for example—for any agricultural commodity crop planted in the former wetland (16 U.S.C. § 1311, Supp. 1992). Agricultural commodity crops are specifically listed as sugarcane and crops that require annual tilling of the soil (16 U.S.C. § 3801(a)(1), Supp. 1992); 7 C.F.R. § 12.2(a)(1). Some lands are exempted by definition (Chapter 3). Wetlands converted to farmable land before December 1985, or "prior converted cropland," are exempt (16 U.S.C. § 3801(A)(4)(a), Supp. 1992). Also exempt are artificial ponds that hold agricultural water; wetlands made farmable by natural conditions, such as drought; wetlands for which it is determined that the cropping would have only a "minimal effect"; wetlands for which the farmer demonstrates "undue economic hardship" based on conversion expenditures made before Dec. 23, 1985 (7 C.F.R. § 12.5(b)). Eligibility determinations, including decisions about exemptions under the swampbuster provision, are made by ASCS. NRCS applies the minimal effect exemption. Under the FSA, NRCS makes wetland delineations at the request of farmers and based on its own regulations and the National Food Security Act Manual (NFSAM). NRCS is authorized to make wetland delineations by use of soil maps and aerial photography, without field visits (Chapter 8). The differences in objectives and statutory exemptions of the FSA and the CWA have caused some confusion over the regulatory status of wetlands on agricultural lands; the federal government has tried to resolve these. The Clinton administration issued a wetlands policy on Aug. 23, 1993, which notes that NRCS, USACE, EPA, and FWS signed an interagency agreement to develop consistent administration of their wetland programs (White House Office on Environmental Policy, 1993). USACE and EPA amended their regulations so that land qualifying as prior converted cropland under the FSA would not be treated as wetland under CWA (58 Fed. Reg. 45, 007, 1993; 33 C.F.R. § 328.3(a)(8); 40 C.F.R. §§ 110.1, 112.2, 116.3, 117.1, 122.2, 230.3). As a result,

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Wetlands: Characteristics and Boundaries property designated by NRCS as prior converted cropland does not require a Section 404 permit regardless of the characteristics of the land. In January 1994, USACE, EPA, and NRCS entered into an MOA regarding wetland jurisdictional delineations on agricultural lands (Memorandum of Agreement, 1994). The agreement states that NRCS is responsible for making wetland delineations on all agricultural lands and that the delineations are to be used for the swampbuster provisions and for CWA. NRCS is to use NFSAM for swampbuster delineations, and it uses the USACE 1987 manual for CWA delineations. The three agencies agreed to seek consistency in wetland delineations. Because NRCS relies heavily on maps and aerial photographs, the memorandum provides that the agencies are to agree on mapping conventions as well. The FSA, like Section 404 of the CWA, motivates non-regulatory activities that supplement regulatory programs. Examples include inventory and conservation initiatives. FEDERAL AGENCY MANUALS BEFORE 1989 As explained in Chapter 3, the federal wetland definitions embrace three factors: water, substrate, and biota. The characteristic state of each is a criterion for the identification of wetlands. All of the manuals prepared by the federal agencies provide guidance on the use of indicators for testing each of the criteria at specific sites. This kind of technical guidance is essential because the definitions themselves are too general to be used directly. USACE Manual Until 1987, USACE administered the CWA Section 404 program, including jurisdictional determinations and permit decisions on wetlands, without the benefit of a technical manual. In 1978, shortly after the 1977 CWA amendments and the consequential amendments to the USACE regulations that define wetlands, USACE assigned the Environmental Laboratory at the Waterways Experiment Station (WES) the task of developing a delineation manual. WES originally conceived of a two-volume manual: Volume I would specify criteria for hydrology, vegetation, and soils; Volume H would describe methods and procedures for delineation. The first draft of Volume I was circulated for review within USACE in 1982. Because of internal disagreements over this draft, it was held in draft form while WES continued to work on Volume H. During the early 1980s, WES worked with USACE districts to test the proposed methods and procedures in the field. Ultimately, the two-volume draft manual was combined into a single volume that was reviewed within USACE in 1985 and 1986. The final product was published in January 1987 as the U.S. Army Corps of Engineers Wetlands Delineation Manual (1987 Corps manual) (Environmental Lab, 1987). The 1987 Corps manual gave detailed guidance so that USACE personnel could perform

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Wetlands: Characteristics and Boundaries wetland delineations simply and quickly. It also gave instructions on the exercise of professional judgment for atypical situations. After the 1987 Corps manual was published, USACE evaluated its application by the districts. In early 1988, USACE (WES, headquarters, and district representatives) began to assess the need to modify the manual. In spring 1988, however, USACE joined EPA, NRCS, and FWS in developing a joint manual for wetland delineations. The result was the 1989 interagency manual (Federal Interagency Committee for wetland Delineation, 1989), which was subsequently withdrawn from use. The federal government then proposed revisions to the manual in 1991. When the 1989 interagency manual was withdrawn, and while proposed revisions were pending, USACE continued to use its 1987 Corps manual. In fact, Congress directed that USACE follow the 1987 Corps manual and that landowners who had delineations made under the 1989 interagency manual be given the opportunity to revise them according to the 1987 Corps manual (Energy and Water Development Appropriation Act of 1993, P.L. 102-377, 106 Stat. 1315, 1992). EPA Manual In April 1988, EPA (1988a) published its two-volume wetland Identification and Delineation Manual. EPA began developing its manual with the issuance in 1980 of interim guidance for the identification of wetlands. In 1983, the rationale and guidance were revised and expanded, and a draft manual was prepared. A revised draft was prepared and circulated again in 1985 for agency and external review. After field testing and modification in response to review, the 1988 manual was published. EPA stated, as had USACE, that it was following the "three-parameter" definition of wetlands found in USACE and EPA regulations and based on hydrology, soils, and vegetation. The 1988 EPA manual, however, allows delineators to rely on vegetation alone for routine delineations and when obligate wetland or upland species are dominant. According to the manual, soils and hydrology must be evaluated if the vegetation is not dominated by obligate wetland or upland species. The manual describes the difficulties of using hydrologic indicators for delineating wetland boundaries, and it justifies the heavier reliance on soils and vegetation in terms of these difficulties. The field methodology in Volume II of EPA's 1988 manual, which was to be used by EPA personnel, includes a "simple approach" for "routine" jurisdictional determinations and a "detailed approach" for "large and/or controversial sites or projects." The simple approach uses vegetation to define the wetland unless there are reasons to look at other indicators. These approaches are analogous to the 1987 Corps manual's ''routine approach" and ''comprehensive approach." For vegetation units dominated by facultative species (not dominated by obligate

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Wetlands: Characteristics and Boundaries wetland plants), the manual requires that soils and hydrology be checked; indirect indicators of hydrology are sufficient for this purpose. The detailed approach requires greater quantification of the composition of vegetation and an examination of soils and hydrology. Similarly, the manual requires a more detailed examination for atypical or disturbed areas. Shortly after EPA published its 1988 manual, it collaborated in publishing the 1989 interagency manual. After the 1989 interagency manual was withdrawn and its proposed revisions were developed, EPA announced that it would follow the 1987 Corps manual (58 Fed. Reg. 4,995, 1993). NFSAM NRCS uses a wetland delineation manual that was developed in response to FSA. In March 1994, NRCS released the third edition of NFSAM, thus replacing the 1988 second edition and its amendments. The third edition incorporates changes that implement the 1994 MOA, although some important components were still under development when it was released. As these are finished, they will be published as amendments to NFSAM. In addition to wetland delineation, NFSAM discusses other NRCS programs, such as determination of highly erodible land, exemptions, and procedures for NRCS and ASCS. Part 513 of the NFSAM describes the preparation for wetland determinations; part 514 describes the procedures for wetland determinations. Indicators for field delineation are given in part 527. The FSA requires NRCS to consult with FWS on wetland delineation matters; the 1994 MOA also requires coordination with USACE, EPA, and FWS. The NFSAM identifies the NRCS wetland decisions that require consultation or coordination with other agencies. The 1994 MOA authorizes NRCS to make wetland delineations on agricultural lands and associated nonagricultural lands. The NFSAM makes it clear that NRCS will apply the FSA for agricultural lands and CWA for nonagricultural lands. Thus, for nonagricultural lands, NRCS will use the 1987 Corps manual. The NFSAM requires that, for agricultural lands, three factors—hydric soils, hydrology, and hydrophytic vegetation—be assessed independently. Appendixes to the NFSAM list indicators for soils, vegetation, and hydrology. Under the terms of the FSA, farmers must obtain a wetland delineation before NRCS determines whether their lands qualify for statutory exemptions or exclusions. NRCS will perform wetland delineations at the request of a farmer. Some areas that would otherwise qualify as wetlands are exempt from NRCS-administered programs. These include artificial wetlands on farmland that was cropped before Dec. 23, 1985 (7 C.F.R. §§ 12.31-12.33), prior converted cropland, irrigation-induced wetlands, farmed wetlands on which fanning is compatible with wetland status, wetlands created by mitigation, and wetlands or portions of wetlands covered by the minimal-effect exclusion. NRCS determines whether an exclusion applies and, if so, marks the excluded areas. Under the NFSAM, an

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Wetlands: Characteristics and Boundaries NRCS wetland delineation is valid for 5 years unless new information warrants a revision. The NFSAM also provides that an NRCS wetland determination stays with the land "until officially changed." The NFSAM directs NRCS to make as many office determinations as possible. Office determinations are based on review of at least three aerial photographs, soil surveys, and other determinations previously made for the property (Chapter 8). NRCS, USACE, EPA, and FWS are continuing to work on protocols for mapping and photography that will be acceptable to all four agencies for wetland delineations. NFSAM provides that NRCS do a field wetland determination if the information is insufficient for an office determination. In practice, field determinations are done only when a farmer appeals an office determination. NFSAM sets standards for classes of wetlands defined by FSA. These classes relate to the kinds of farming activities that are allowed or prohibited on farmed wetland—areas that were drained or otherwise manipulated before Dec. 23, 1985, and planted at least once with an agricultural commodity crop. A farmed wetland that is a playa, pothole, or pocosin must be inundated for at least 7 consecutive days or saturated for at least 14 consecutive days during the growing season. Farmed wetlands that are not potholes, playas, or pocosins must have a 50% chance of being seasonally flooded or ponded for at least 15 consecutive days during the growing season or for 10% of the growing season, whichever is less. NFSAM specifically acknowledges that these especially restrictive guidelines are intended to protect the unique wetland functions of potholes, playas, and pocosins. Wetland used for pasture or forage production, but not permanently drained or altered, qualifies as fanned wetland. The hydrologic thresholds for fanned wetland pasture require inundation for at least 7 consecutive days or saturation for at least 14 consecutive days during the growing season. FSA requires coordination between NRCS and FWS on all wetland identification, exemption, and mitigation and restoration projects. NRCS participated with USACE, EPA, and FWS in the interagency efforts that resulted in the 1989 interagency manual. NRCS did not, however, formally adopt the 1989 interagency manual because it has its own regulations. Unlike USACE and EPA, NRCS does not apply the 1987 Corps manual to its wetland delineations on agricultural lands. Attempts to Revise the Federal Manuals As mentioned in Chapter 3, after the 1989 interagency manual was criticized, the Bush administration proposed a revised delineation manual (1991 proposed revisions, 56 Fed. Reg. 40,446; 1991). It initially announced that the 1989 interagency manual would remain in effect pending adoption of revisions. After Congress directed that USACE follow the 1987 Corps manual, however, EPA agreed to do the same (58 Fed. Reg. 4,995; 1993). NRCS has continued to use

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Wetlands: Characteristics and Boundaries NFSAM and its own regulations. The 1991 proposed revisions, which followed the 1989 interagency manual, also generated considerable public and serious scientific criticism. The controversy resulted in continued use of the 1987 Corps manual, and a congressional mandate that the National Academy of Sciences conduct a study, as described in Chapter 1. COMPARING THE FEDERAL MANUALS Table 4.1 lists some features of the 1987 Corps manual, the 1989 interagency manual, the 1991 proposed revisions, and NFSAM. Each manual applies a three factor definition of wetland, yet each does so differently. Many of the differences among the manuals seem minor, but they can be significant in the field. The 1987 Corps manual gives criteria and lists indicators for hydrology, hydric soils, and hydrophytic vegetation. Delineators must test hydrology, vegetation, and soils, but indirect indicators may be used to show that criteria are satisfied. Only for routine determinations affecting an area of less than 5 acres (about 2 ha) and in special cases, such as disturbed wetlands where vegetation has been removed, can evidence on specific criteria be omitted, however. The 1987 Corps manual is supplemented with USACE guidance letters and memoranda addressing specific issues pertinent to wetland delineation. The 1989 interagency manual allows somewhat greater latitude in the use of indicators. For example, if hydric soils and wetland hydrology are present, a delineator can assume that the vegetation is hydrophytic. Similarly, if the hydrology is unaltered, wetland hydrology can be inferred from hydric soils or from characteristics of vegetation (plant adaptation to recurrent inundation or saturation) for routine and intermediate level determinations but not for comprehensive determinations. The 1991 proposed revisions require strict proof of hydrology, vegetation, and soils with separate field evidence. For example, hydrophytic vegetation or hydric soils cannot be used as indicators of hydrology. TABLE 4.1 Comparison of Manuals Characteristic 1987 Corps Manual 1989 Interagency Manual 1991 Proposed Manual 1993 NFSAM Manual Factors 3 3 3 3 Allowable combinations Show each separately; use fewer than three only for special cases (disturbed sites) or very strong evidence of two Strong evidence of two sufficient to support the third Show each separately Show each separately

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Wetlands: Characteristics and Boundaries NFSAM requires independent assessment of hydric soil, hydrology, and hydrophytic vegetation. Because few NFSAM delineations are done in the field, however, it can be misleading to compare NFSAM's field requirements with those of the other manuals that require field delineations. NFSAM also incorporates by reference the field office technical guides, which provide specific information. For example, field indicators of hydric soils appear not in NFSAM, but in the technical guides maintained in NRCS field offices. Hydrology The manuals differ in their treatment of hydrology, as shown in Tables 4.2 and 4.3. Hydrologic Evidence The 1987 Corps manual establishes saturation thresholds as a percentage of growing season, which is defined by frost-free days. The manual also lists classes of hydrologic regimes that range from permanently inundated to intermittently or never saturated. The 1987 manual requires that saturation be to the surface. The surface can be dry, however, even though an area is considered saturated to the surface, because the critical water table depth is 12 in. (30 cm). The rationale is that capillary action saturates the upper surface of the soil above TABLE 4.2 Comparison of Manuals: Hydrology Characteristic 1987 1989 1991 NFSAM Hydrologic threshold Inundation or saturation at surface for >12.5% or 5-12.5% of growing season with other evidence Inundation or saturation at surface for at least 7 days of growing season Inundation at surface (15 days; saturation at surface (21 days during growing season Inundation at surface for 15 days for most areas; 7 days for potholes, playas, or pocosins Critical depth Root zone (12 in.; 30 cm) 0.5 to 1.5 ft (15-46 cm); depending on soil Surface Surface Growing season Frost-free days, based on air temperature Biological zero (41°F; 5°C) 20 in (50 cm) below. soil surface; soil temperature zones estimated Three weeks before to 3 weeks after last killing frost Biological zero, estimated from frost-free days

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Wetlands: Characteristics and Boundaries TABLE 4.5 Comparison of Manuals; Vegetation Characteristic 1987 1989 1991 NFSAM (field determinations)a Use of Hydrophyte Listb to determine indicator status (OBL, FACW, FAC, FACU, UPL) of plant species Y Y Y Y Use of + and - to modify indicator Y N N Y Hydrophytic vegetation; >50% of the dominant species OBL, FACW, or FACc Y Yd N N Hydrophytic vegetation; prevalence indexe less than 3.0 using all species presentc N Yd Yf Y Other indicators of hydrophytic vegetation allowed (morphologic adaptations, documentation from technical literature, physiologic adaptations) Ye, g Nh Nh N FAC-neutral option Y Ni Nj N a Most NFSAM determinations are not made in the field. NFSAM incorporates the 1987 USACE Manual for field delineation matters that it does not address specifically. b OBL, obligate; FACW, facultative-wet; FAC, facultative; FACU, facultative-upland; UPL, upland species. c Where OBL, 1.0; FACW, 2.0; FAC, 3.0; FACU, 4.0; UPL, 5.0. d If the hydric soil is present and wetland hydrology is verified, vegetation is assumed to be hydrophytic even if the vegetation criterion is not met. Such areas, however, are considered to be problem area wetlands and appropriate cautions are advised. e Weighted average. A single number that summarizes quantitative data about a large number of species within a community and gives weight to each species' contribution to the final number in terms of an assigned value. f Listed specific exceptions to this criterion. g See text for list of adaptations. h Some morphologic adaptations are used as indicators of hydrology. i Although the FAC-neutral test is not explicitly listed as an option, one vegetations indicator (see footnote c) can be considered a type of FAC-neutral test. j Sought comments of the use of this option and several variants of it. The 1989 interagency manual uses the following wording: macrophytic plant life growing in water, soil or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content. The 1991 proposed revisions define hydrophytic vegetation as plants that live in conditions of excess wetness. For purposes of this manual, hydrophytes are defined as macrophytic plant life growing in water or on sub-

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Wetlands: Characteristics and Boundaries merged substrates, or in soil or on a substrate that is at least periodically anaerobic (deficient in oxygen) as a result of excessive water content. NFSAM uses the FSA definition (16 U.S.C. §3801(a)(9)), which states that hydrophytic vegetation is plants growing in water or in a substrate that is at least periodically deficient in oxygen during the growing season as a result of saturation or inundation by water. Notwithstanding the differences among these definitions, all of the manuals rely on one FWS publication, the National List of Plant Species that Occur in Wetlands (P.B. Reed, 1988)—commonly called the Hydrophyte List—for identification of hydrophytic species and assignment of indicator status. The Hydrophyte List divides plants into five fidelity categories, by their wetland indicator status, that reflect "the range of estimated probabilities (expressed as a frequency of occurrence) of a species occurring in wetland versus nonwetland" (P.B. Reed, 1988, p. 8) (Chapter 5). The categories are as follows: OBL, obligate wetland plants, which almost always occur in wetlands (estimated probability >99%) but can occur rarely elsewhere (estimated probability <1%). FACW, facultative wetland plants usually occur in wetlands (estimated probability >67-99%) but also occur elsewhere (estimated probability 1-33%). FAC, facultative plants have a similar likelihood of occurring in wetlands and nonwetlands (estimated probability 33-67%). FACU, facultative upland plants sometimes occur in wetlands (estimated probability 1-33%) but more often in nonwetlands (estimated probability >67-99%). UPL, obligate upland plants occur rarely in wetlands (estimated probability <1%). Determining Prevalence The manuals differ in the indicators and specific criteria they set up for determining whether a site contains a predominance or prevalence of hydrophytic vegetation (Table 4.5). The 1987 Corps manual does not use the term "criterion" for vegetation but refers instead to "diagnostic environmental characteristics": The prevalent vegetation consists of macrophytes that are typically adapted to areas having hydrologic and soil conditions described in the following definition of wetlands: those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances to support, a prevalence of vegetation typically adapted for life in saturated soil conditions. According to the 1987 Corps manual, any one of the following is indicative that hydrophytic vegetation is present:

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Wetlands: Characteristics and Boundaries More than 50 percent of the dominant species are OBL, FACW, or FAC on lists of plant species that occur in wetlands. Other indicators, specifically: (1) visual observation of plant species growing in areas of prolonged inundation and/or soil saturation; (2) morphological adaptations; (3) technical literature, including taxonomic references, botanical journals, technical reports, technical workshops, conferences, and symposia, and the wetland plant data base of the National Wetland Inventory [currently the Hydrophyte List]; (4) physiological adaptations; and (5) reproductive adaptations. In the case of the ''other indicators'' listed under (b) above, the 1987 Corps manual notes that "additional training and/or experience may be required to employ these indicators." Under the methods section, the 1987 Corps manual further specifies that for on-site inspections of areas of more than 5 acres (2 ha), if morphologic or physiologic adaptations are used to indicate hydrophytic vegetation, two or more of the dominant species must have these adaptations. The 1989 interagency manual allows alternative criteria to show that wetland vegetation is present: An area has hydrophytic vegetation when, under normal circumstances: more than 50 percent of the composition of the dominant species from all strata are obligate (OBL), facultative wetland (FACW), and/or facultative (FAC) species, or a frequency analysis of all species within the community yields a prevalence index value of less than 3.0 (where OBL = 1.0, FACW = 2.0, FAC = 3.0, FACU = 4.0, and UPL = 5.0). CAUTION: When a plant community has less than or equal to 50% of the dominant species from all strata represented by OBL, FACW, and/or FAC species, or a frequency analysis of all species within the community yields a prevalence index value of greater than or equal to 3.0, and hydric soils and wetland hydrology are present, the area also has hydrophytie vegetation. (Note: these areas are considered problem area wetlands.) The 1989 interagency manual states that wetland vegetation can be indicated by any of the following evidence: OBL species comprise all dominants in the plant community; or OBL species do not dominate each stratum, but more than 50 percent of the dominants of all strata are OBL, FACW, or FAC species (including FACW+, FACW-, FAC+, and FAC-); or A plant community has a visually estimated percent coverage of OBL and FACW species that exceed the coverage of FACU and UPL species; or A frequency analysis of all species within the community yields a prevalence index value of less than 3.0 (where OBL = 1.0, FACW = 2.0, FAC = 3.0, FACU = 4.0, and UPL = 5.0); or

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Wetlands: Characteristics and Boundaries A plant community has less than or equal to 50% of the dominant species from all strata represented by OBL, FACW, and/or FAC species, or a frequency analysis of all species within the community yields a prevalence index value of greater than or equal to 3.0, and hydric soils and wetland hydrology are present. (Note: In other words, if the hydric soil and wetland hydrology criteria are met, then the vegetation is considered hydrophytic. For purposes of this manual, these situations are treated as disturbed or problem area wetlands because these plant communities are usually nonwetlands.) The 1991 proposed revisions set up a single prevalence index threshold as an indicator of hydrophytic vegetation: An area meets the hydrophytic vegetation criterion if, under normal circumstances, a frequency analysis of all species within the community yields a prevalence index value of less than 3.0 (where OBL = 1.0, FACW = 2.0, FAC = 3.0, FACU = 4.0, and UPL = 5.0). Specific wetland types that do not meet this requirement are listed as exceptions, including prairie potholes, playas, and vernal pools. Comments were sought on additional exceptions. The 1991 proposed revisions do not give specific field indicators, although the methods section (Part III) refers to indicators of hydrophytic vegetation. As in the 1989 interagency manual, some adaptations of plant structure and morphology are used as indicators of hydrology but not of hydrophytic vegetation; physiologic and reproductive adaptations are not used as indicators. For field delineations, NFSAM uses the numerical prevalence index in a manner similar to that of the 1991 proposed revisions. NFSAM also cross-references and incorporates by reference the hydrophytic indicators from the 1987 Corps manual. Because both the 1987 Corps manual and the 1989 interagency manual refer to "50% of the dominant species" as a threshold for determining whether hydrophytic vegetation is prevalent, the term "dominant species" must be defined and methods must be established for measuring dominance and selecting dominant species. The 1987 Corps manual (pp. 16-17) defines ''dominant species" in the section on characteristics and indicators as those that ''contribute more to the character of a plant community than other species present, as estimated or measured in terms of some ecological parameter or parameters." In the methods section, dominant species are "those that have the largest relative basal area (overstory), height (woody understory), number of stems (woody vines), or greatest areal cover (herbaceous understory)." That is, a measure of dominance is established for each stratum, or layer, of the vegetation. For routine determinations, the measure of dominance is estimated visually and dominant species are determined subjectively. For comprehensive determinations, however, dominant species are selected by ranking the species in each stratum in descending order of dominance based on the appropriate measure for that stratum. The three species

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Wetlands: Characteristics and Boundaries of highest rank from each stratum are selected as the dominant species if four strata are present. If only one or two strata are present, the five species of highest rank are selected. Thus, in the case of a plant community with four strata, 12 species (the three top-ranked in each layer of the vegetation) are selected as dominants. If 7 or more (more than 50%) of these dominant species are OBL, FACW, or FAC, then the community is predominantly hydrophytic according to the 1987 manual's "50% rule." In the case of a plant community with only two strata, 10 species are selected as dominants, and at least 6 must be OBL, FACW, or FAC if the community is to be classified as predominantly hydrophytic. The 1989 interagency manual also ranks species in each stratum in descending order of the value of the dominance measure used for that stratum, but it selects dominant species differently: For each stratum (e.g., tree, shrub, and herb) in the plant community, dominant species are the most abundant plant species (when ranked in descending order of abundance and cumulatively totaled) that immediately exceed 50 percent of the total dominance measure (e.g., basal area or areal coverage) for the stratum, plus any additional species comprising 20 percent or more of the total dominance measure for the stratum. For each stratum, all of the species are ranked in descending order of abundance. The abundances for all species in the stratum are totaled, and the cumulative abundance is then computed for each species on the list. Two thresholds are identified: 50% of the total, and 20% of the total. The dominants are species whose abundances fall above the 50% mark on the cumulative abundance list for the stratum, plus any other species that individually account for 20% or more of the total abundance. For example, if the herb layer contains one species with 90% cover, two species with 40% cover, one species with 20% cover, and one species with 10% cover, the total abundance (dominance measure) for this layer would be 200%, 50% of the total would be 100%, and 20% of the total would be 40%. Only the first three species would be considered dominants. This procedure is repeated for each stratum. The numbers of dominant species in all strata are totaled to obtain the total number of dominant species. If the herb layer had 3 dominant species, the shrub layer had 2 dominant species, and the tree layer had 3 dominant species, then the entire plant community would have 8 dominant species. If 5 or more (more than 50%) of these species are OBL, FACW, or FAC, then the community is predominantly hydrophytic according to the 1989 interagency manual's "50% rule." Like the 1987 Corps manual, the 1989 interagency manual uses visual estimates of dominance for routine determinations, and it establishes more detailed and quantitative methods for measuring dominance in comprehensive determinations. The method of selecting dominant species, however, is the same for all determinations. The 1989 interagency manual identifies five strata (tree, sapling, shrub, woody. vine, herb) for which dominant species should be selected, plus a moss layer for some types of wetlands.

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Wetlands: Characteristics and Boundaries The 1989 interagency manual's method of selecting dominant species became acceptable for use under the 1987 Corps manual through the issuance of a regulatory guidance letter (RGL) by USACE in March 1992. The same RGL authorizes the use of five strata for determinations of dominant species, as did the 1989 interagency manual. Both the 1987 Corps and 1989 interagency manuals allow the same species to be considered dominant in more than one stratum. The 1991 proposed revisions do not define dominant species, because all species are considered in calculating the prevalence index—the only indicator used for hydrophytic vegetation. NFSAM applies the methods of the 1987 Corps manual for routine determinations in the field. For comprehensive determinations, NFSAM uses the prevalence index, which does not require selection of dominant species. Treatment of FAC Species and FACU-Dominated Wetlands The manuals differ in their treatment of FAC and FACU species in determining whether the vegetation is hydrophytic. The differences affect wetland determinations most significantly where independent evidence of hydrology, vegetation, and soils is required. Areas that satisfy the criteria for hydrology and for soils can have plant communities dominated by FAC or FACU species. If FAC or FACU species are not treated as hydrophytic, regardless of evidence on hydrology and soils, such areas would not be classified as wetlands. Discussion of this issue has focused on the "FAC-neutral test," which eliminates consideration of FAC species from determinations of prevalence. According to the 1987 manual, this option can be adopted by individual USACE districts if the district questions the indicator status of a facultative species and provides documentation to the USACE representative on the regional plant list panel (Chapter 5). Guidance issued by USACE in March 1992 on the use of the 1987 Corps manual provides that the FAC-neutral test may be used to help clarify a delineation where evidence of wetland hydrology or soils is weak, but it may not be used to exclude areas that otherwise qualify as wetlands. The 1989 interagency manual does not use the term "FAC-neutral test." One field indicator of hydrophytic vegetation, however, could be interpreted as a FAC-neutral test. The primary way that the 1989 interagency manual handles FACand FACU-dominated wetlands, however, appears as number 5 in the list of field indicators of hydrophytic vegetation. This indicator specifies that where 50% or fewer of the dominant species are OBL, FACW, or FAC (where FAC or FACU species dominate), the vegetation is hydrophytic only if hydric soil and wetland hydrology criteria are met. Furthermore, the 1989 interagency manual treats these areas as disturbed or problem area wetlands and outlines special procedures for their evaluation. The 1991 proposed revisions use only the prevalence index, which incorporates all species, for vegetation determinations. However, the authors of the

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Wetlands: Characteristics and Boundaries revisions sought comments on six variants of the FAC-neutral test. FAC and FACU-dominated wetlands are treated as "exceptions to the three criteria"; they are wetlands that fail to satisfy all the criteria for hydrology, soils, and vegetation. The only named exceptions to the three criteria were pocosins, playas, prairie potholes, vernal pools, and three types of conifer swamps dominated by FACU species: white pine bogs of the Northeast and northern Midwest, eastern hemlock swamps and bogs in the Northeast, and tamarack bogs. The first four were included because they are "widely recognized wetlands that fail to meet the hydrology criterion." The possible exceptions on which comments were sought included pitch pine lowlands in the Northeast, jack pine and white spruce in evergreen-forested swamps in the northern Midwest, lodgepole pine bogs and muskegs in the Northwest and Alaska coasts, sugar maple and paper birch swamps and bogs in the upper Midwest, and longleaf pine wet savannahs of the Southeast. Other wetlands dominated by FAC and FACU species would be excluded under the 1991 proposed revisions. NFSAM does not specifically address wetlands dominated by FACU species. When field delineations are done, the delineator uses all species, including FAC and FACU, in calculating the prevalence index. NFSAM incorporates by reference the 1987 Corps manual for vegetation, but the NRCS relies on a prevalence index that uses all species. Hydric Soils Each manual uses the definitions of hydric soils established by the National Technical Committee for Hydric Soils (NTCHS): A hydric soil is a soil that in its undrained condition is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions that favor the growth and regeneration of hydrophytic vegetation. The third edition of "Hydric Soils of the United States," issued in 1991, modifies the definition by deleting the reference to hydrophytic vegetation. The manuals, however, continue to use the 1985 NTCHS definition. There are some differences between the manuals with regard to methods of identifying hydric soils (Table 4.6). The field indicators of hydric soils are essentially the same in all of the manuals, and include: organic soils, histic epipedon, sulfidic material, aquic or peraquic moisture regime, reducing conditions, soil color, high level of organic matter at surface, streaking by organic matter, and organic pan. Correlation between the presence of wetland hydrology and the occurrence of hydric soil characteristics is well established, but the period of inundation or saturation required to produce them is less well understood (Chapter 5). According to all three manuals, hydric soils can be inferred if hydrologic observations indicate that threshold durations have been reached. In most cases, the 1987 Corps and

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Wetlands: Characteristics and Boundaries TABLE 4.6 Comparison of Manuals: Soils Characteristic 1987 1989 1991 NFSAM Soil definition NTCHS NTCHS NTCHS NTCHS Field verification Field evidence only Field evidence, maps with field verification Field evidence only Field evidence, maps Evidence for hydric soils Assumes soil is hydric where OBL or OBL and FACW species with same abrupt boundary Seven-day flooding demonstrates hydric soilsa 15 days' inundationa 21 days' saturation onlya Seven-day flooding or 14 days' saturation at or near surfaceb a Number of days saturated during the growing season. b "Saturated to the surface" is when the water table is within 0.5 ft of the surface for coarse sand, sand, or fine sandy soils, or 1.0 ft of the surface for all other soils (NFSAM, 1994). 1989 interagency manuals require field identification of hydric soils for any delineation. Where there is strong evidence of wetland vegetation and hydrology, the 1987 Corps manual authorizes a wetland delineation without field verification of hydric soils. The 1989 interagency manual provides that soils need not be verified where all dominant plant species are OBL or where all dominant plant species are OBL and FACW and the wetland boundary is abrupt. For these two manuals, the characterization of the plant community comes ahead of soils or hydrology. NFSAM gives criteria for hydric soils (Chapter 5) and also refers to "The Field Indicators of Hydric Soils in the United States", a field office technical guide, for evaluation of soils in the field. NFSAM relies heavily on soil maps (Chapters 5, 8). Soils are assessed first, and then hydrology is determined from aerial photographs. Special Situations: Disturbed Areas, Problem Areas, Exceptions Each manual takes a different approach to special cases (Table 4.7). The 1987 Corps manual separates "atypical situations" and "problem areas." Atypical situations involve alterations that obscure indicators of vegetation, soils, or hydrology. Alterations include discharge of dredged or fill material; fires, avalanches, volcanic activity, or changing river courses; and artificial wetlands. This manual also stresses the need to assess normal circumstances for an area. For example, if impounded water has become a normal circumstance, the area affected may be considered wetland. Methods to be used for site investigations in atypical situations also are given separately for vegetation, soil, and hydrology.

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Wetlands: Characteristics and Boundaries TABLE 4.7 Comparison of Manuals: Special Cases Characteristic 1987 1989 1991 Disturbed areas Areas subject to filling, removal of vegetation, levee or dam, construction wetlands newly created by human action or natural events Areas that would have been classified as wetlands prior to disturbance Same as 1989 Problem areas Wetlands on drumlins, seasonal wetlands, prairie potholes, vegetated flats FACU-dominated: evergreen-forested wetlands; wetlands on glacial till; variable seasonal wetlands; interdunal swale wetlands; river bars; vegetated flats; caprock limestone wetlands; newly created wetlands; wetlands on Entisols, red parent material, Spodosols, Mollisols Newly created wetlands; wetlands on glacial till; mosaics; cyclical wetlands; vegetated flats; interdunal swale wetlands; springs and seeps; drought-affected wetlands Exceptions None listed None listed Pocosins, playas, prairie potholes, vernal pools, white pine bogs, eastern hemlocks, tamarack bogs, others as proposed Problem areas, as described in the 1987 manual, are those for which application of the criteria is difficult, at least seasonally. Four categories are considered (Table 4.7). The 1987 manual requires them to be evaluated for wetland functions. "Atypical situations" in the 1957 manual are "disturbed areas" in the 1989 interagency manual. These areas have been modified by human activities or natural events. The methods of site investigation of disturbed areas are the same as for atypical areas in the 1987 Corps manual, with two additional methods for characterizing hydrology. The 1989 interagency manual identifies a greater number of problem areas than does the 1987 Corps manual (Table 4.7). Both manuals provide detailed procedures for delineating problem wetlands. The 1991 proposed revisions describe "disturbed wetlands" as those that

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Wetlands: Characteristics and Boundaries would have met the criteria for hydrology, soils, and vegetation before their disturbance. The 1991 proposed revisions do not describe atypical wetlands, but they do describe atypical hydric soils (Table 4.7). The revisions use the same methods for site investigations of atypical wetlands that appear in the 1989 interagency manual, but they include more descriptive methods for ground water investigations. The 1991 proposed revisions list some types of wetlands as exceptions and problem areas (Table 4.7). Wetlands that are exceptions, as well as the problem area wetlands, are subject to more detailed procedures than are other wetlands. For field delineations, NFSAM identifies "disturbed areas" as those in which the soils, vegetation, or hydrology have been altered so as to make standard wetland identification unreliable. NFSAM refers to and incorporates by reference the section of the 1987 Corps manual that addresses atypical situations for procedures to be followed when soils, vegetation, or hydrology have been disturbed. Regulatory treatment of special situations illustrates very well the distinction between identification and boundary setting for wetlands on one hand and jurisdiction on the other. The reference definition of wetlands given in Chapter 3 makes no exclusions of wetlands on the basis of origin. The definition applies equally to ancient wetlands as well as wetlands of recent origin, to natural as well as artificial wetlands, and to wetlands created by intent as well as those created by accident. For reasons that are quite understandable in a sociopolitical context, the jurisdictional treatment of wetlands is much more complex. Differences Resulting from Application of the Manuals Comparisons among the manuals have produced many claims regarding the differences in results that can arise from their use. The manuals sometimes provide inconsistent guidance on the same subject. Also, each manual is organized differently, so comparisons among them can be misleading. It is difficult to ascertain whether the degree to which differences in delineation results occur because of misapplication of a manual or because of actual differences among manuals. The office delineation method used by NFSAM does not lend itself to extensive comparison with other manuals. Wetland delineations conducted with office methods are susceptible to errors that do not affect field delineations (Chapter 8). After field testing the 1991 proposed revisions and the 1987 and 1989 manuals, a four-agency team in the Pacific Northwest concluded that the 1991 proposed revisions would result in an overall reduction exceeding 50% of the acreage delineated as wetland under the 1989 and 1987 manuals. This was primarily because of the limited number of acceptable indicators of hydrology (personal communication, Oct. 29, 1991 to Larry Vinzant from Thomas Yocom, Robert A. Leidy, Nancy A. Dubbs, and Mary Butterwick). In the Mississippi Valley, scien-

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Wetlands: Characteristics and Boundaries tists commenting on the 1991 proposed revisions indicated that 30% of the bottomland hardwood wetlands in Louisiana would cease to be delineated as wetlands if the 1991 proposed revisions were adopted. This estimate was based on field testing by USACE (Lower Mississippi Valley Division) and the Coalition to Restore Coastal Louisiana. Significant interannual variations in flooding and saturation were cited as reasons that much of the bottomland hardwood forest would fall to meet the hydrologic requirements (personal Communication, Dec. 13, 1991 to Gregory Peck, EPA, from James G. Gosselink and G. Paul Kemp, Coalition to Restore Coastal Louisiana). A study by the Environmental Defense Fund and the World Wildlife Fund suggests that the hydrologic requirements of the 1991 proposed revisions would result in exclusion of approximately 50% of the remaining wetlands in the United States. Substantial areas of bottomland hardwood forest, northeastern and midwestern bog areas, 23% of the Everglades National Park, and 80% of the Great Dismal Swamp in Virginia and North Carolina would be dropped. As a general matter, it seems certain that less area would be delineated as wetland under the 1991 proposed revisions than under the 1989 or 1987 manuals. The difference results primarily from the proposed requirement that hydrology, soils, and vegetation be documented separately, and from the limitations on indicators that can be used for each, especially hydrology. The 1987 and the 1989 manuals are the most similar of the group. Where there is a difference between the two, it generally results in less area delineated as wetland under the 1987 Corps manual than under the 1989 interagency manual. This is explained mainly by a broader and more flexible array of indicators in the 1989 interagency manual.