Wetlands Characteristics and Boundaries (1995) / Chapter Skim
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4 WETLAND DELINEATION: PAST AND CURRENT PRACTICE
4 WETLAND DELINEATION: PAST AND CURRENT PRACTICE
Pages 65-89
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From page 65... ...
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.
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From page 66... ...
, 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.
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From page 67... ...
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.
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From page 68... ...
§§ 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.
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From page 69... ...
NRCS applies the minimaleffect 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)
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From page 70... ...
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.
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From page 71... ...
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 When the 1989 interagency manual was withdrawn, and while proposed revisions were pending, USACE continued to use its 1987 Corps manual.
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From page 72... ...
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.
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From page 73... ...
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.
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From page 74... ...
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.
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From page 75... ...
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 NRC S field offices.
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From page 76... ...
The 1989 interagency manual and the 1991 proposed revisions also allow plant adaptations to indicate hydrology as well as hydrophytic vegetation, as in the 1987 Corps manual. The 1989 interagency manual allows hydric soils to be used as an indicator of hydrology, but does not allow wetland delineation to be
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From page 77... ...
For field delineations, the form for entering hydrologic data in a routine wetland delineation for~ requires information about observed water, rainfall regime, water marks, drift lines, waterborne sediment, water-stained leaves, adaptations in plant morphology, the presence of oxidized rhizospheres, or other information similar to that provided by the indicators listed in the 1987 Corps manual.
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From page 78... ...
Although the beginning and end of the actual growing season can vary by several weeks within a given temperature region or from site to site, the use of the temperature regions does allow the delineator to work with a fixed growing season and decreases the need for site-specific temperature information. The 1991 proposed revisions do not use biological zero; they define the growing season as an interval extending from 3 weeks before to 3 weeks after the frost-free period as determined by use of local weather information.
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From page 79... ...
of plant species Use of + and - to modify indicator Hydrophytic vegetation; >50% of the dominant species OBL, FACW, or FACC Hydrophytic vegetation; prevalence indexe less than 3.0 using all species presents Other indicators of hydrophytic vegetation allowed (morphologic adaptations, documentation from technical literature, physiologic adaptations) FAC-neutral option Y Y Y Y Y N N Y Ed N N N Ad yf ye, g Nh Nh N Ni Nj N aMost NFSAM determinations are not made in the field.
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From page 80... ...
~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.
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From page 81... ...
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 hydrophytic vegetation. (Note: these areas are considered problem area wetlands.)
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From page 82... ...
The 1991 proposed revisions set up a single prevalence index threshold as an indicator of hydrophytic vegetation: An area meets the hydrophyt~c vegetation criterion if, under normal circum stances, a frequency analysis of all species within the community yields a prevalence index value of less than 3.0 (where 0BL = 1.0, FACW = 2.0, FAC = 3.0, FACU = 4.0, and UPL = 5.04. Specific wetland types that do not meet this requirement are listed as exceptions, including prairie potholes, playas, and vernal pools.
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From page 83... ...
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)
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From page 84... ...
The primary way that the 1989 interagency manual handles FAC- and 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)
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From page 85... ...
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.
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From page 86... ...
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.
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From page 87... ...
The 1987 manual requires them to be evaluated for wetland functions. "Atypical situations" in the 1987 manual are "disturbed areas" in the 1989 interagency manual.
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From page 88... ...
Wetland delineations conducted with office methods are susceptible to errors that do not affect field delineations (Chapter 89. 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.
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From page 89... ...
. 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.
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