DRAFT
REVISED FEDERAL MANUAL FOR
IDENTIFYING AND DELINEATING VEGETATED WETLANDS
APRIL 26, 1991
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TABLE OF CONTENTS
Page
Part I. INTRODUCTION 1
Purpose 1
Organization of the Manual 1
Use of the Manual 1
Background 2
Federal Wetland Definitions 5
Section 404 of the Clean Water Act 5
Food Security Act of 1985 6
Fish and Wildlife Service's Wetland
Classification System 6
Relationship of Wetlands Identified by this Manual to
"Waters of the United States" 7
Summary of Federal Definitions 8
Part II. MANDATORY TECHNICAL CRITERIA FOR VEGETATED WETLAND
IDENTIFICATION 9
WETLAND HYDROLOGY CRITERION 10
Wetland Hydrology Background 13
Measuring Wetland Hydrology 14
Historical Recorded Hydrologic Data 15
Aerial Photographs 15
Field Observations ' 16
Direct Evidence of Water 16
Other Signs of Wetland Hydrology 16
HYDROPHYTIC VEGETATION CRITERION 18
Hydrophytic Vegetation Background 19
National List of Wetland Plant Species 20
Dominant Vegetation 21
HYDRIC SOIL CRITERION 22
Hydric Soil Background 23
National and State Hydric Soils Lists 23
County Hydric Soil Map Unit Lists 24
Soil Surveys 24
Use of County Hydric Soils Map Units Lists and Soil
Surveys 25
General Characteristics of Hydric Soils 25
Organic Soils 26
Hydric Mineral Soils 27
Soil Related Evidence of Significant Saturation 28
Difficult-to-Identify Wetlands 31
Forested Wetlands 31
Streamside/Riparian Wetlands 31
Wet Meadows/Prairie Wetlands 32
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Pocosins 32
Playas 32
Prairie Potholes 33
Vernal Pools 33
Part III. STANDARD METHODS FOR IDENTIFICATION AND DELINEATION
OF WETLANDS 34
Selection of a Method 34
Description of Methods 38
Offsite Preliminary Determinations 38
Onsite Determinations 38
Disturbed Area Wetland Determinations 41
Appendices 43
Appendix 1. Offsite Preliminary Determination Method 43
Appendix 2. Routine Onsite Determination Method 46
Appendix 3. Intermediate-level Onsite Determination Method 52
Appendix 4. Comprehensive Onsite Determination Method 59
Appendix 5. Descriptions of Difficult-to-Identify Wetlands 74
Appendix 6. Difficult-to-Identify Hydric Soils 82
Appendix 7. Procedures for Difficult-to-Identify Wetlands 86
Appendix 8. Disturbed Area Procedures 89
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PART Z.
INTRODUCTION
Purpose
The purposes of this manual are: (1) to provide mandatory
technical criteria for the identification and delineation of
wetlands, (2) to provide recommended methods for vegetated
wetlands identification and upper boundary delineation, and (3)
to provide sources of information to aid in their identification.
The document can be used to identify jurisdictional wetlands
subject to Section 404 of the Clean Water Act and to the
"Swampbuster" provision of the Food Security Act of 1985, as
amended, or to identify vegetated wetlands in general for the
National Wetlands Inventory and other purposes. Wetland
jurisdictional determinations for regulatory purposes are based
on criteria in addition to technical criteria, so consult the
appropriate regulatory agency for its interpretation. The term
"wetland" as used throughout this manual refers to vegetated
wetlands. This includes wetlands with natural vegetation and
wetlands where natural vegetation has been temporarily disturbed.
This manual provides a single, consistent approach for
identifying and delineating these wetlands from a multi-agency
Federal perspective.
Organization of the Manual
This manual is divided into three major parts: Part I -
Introduction; Part II - Mandatory Technical Criteria for
Vegetated Wetland Identification; and Part III - Methods for
Identification and Delineation of Vegetated Wetlands. References,
a glossary of technical terms, and appendices are also included.
Use of the Manual
This manual should be used for the identification and delineation
of vegetated wetlands in the United States. Emphasis for
delineation is on the upper boundary of wetlands (i.e.,
wetland-upland boundary) and not on the lower boundary between
wetlands and other aquatic habitats. The technical criteria for
wetland identification presented in Part II are mandatory, while
the methods presented in Part III are recommended approaches.
Alternative methods are offered to provide users with a selection
of methods that range from office determinations to detailed
field determinations. If the user departs from these methods, the
reasons for doing so should be documented. If there are any
inconsistencies between Parts I, II, and III, the guidance
provided in Part II has preeminence over guidance provided in the
other parts.
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Background
At the Federal level, four agencies are principally involved with
wetland identification and delineation: Army Corps of Engineers
(CE) , Environmental Protection Agency (EPA), Fish and Wildlife
Service (FWS), and Soil Conservation Service (SCS). The CE and
EPA are responsible for making jurisdictional determinations of
wetlands regulated under Section 404 of the Clean Water Act
(formerly known as the Federal Water Pollution Control Act, 33
U.S.C. 1344). The CE also makes jurisdictional determinations
under Section 10 of the Rivers and Harbors Act of 1899 (33 U.S.C.
403). Under Section 404, the Secretary of the Army, acting
through the Chief of Engineers, is authorized to issue permits
for the discharge of dredged or fill material into the waters of
the United States, including wetlands. EPA has an important role
in developing the Section 404(b)(l) Guidelines and defining the
geographic extent of waters of the Unites States, including
wetlands. The CE also issues permits for filling, dredging, and
other construction in certain wetlands under Section 10. Under
authority of the Fish and Wildlife Coordination Act, the FWS and
the National Marine Fisheries Service review applications for
these Federal permits and provide comments to the CE on the
environmental impacts of proposed work. In addition, the FWS is
conducting an inventory of the Nation's wetlands and is producing
a series of National Wetlands Inventory maps for the entire
country. While the SCS has been involved in wetland
identification since 1956, it has recently become more deeply
involved in wetland determinations through the "Swampbuster"
provision of the Food Security Act of 1985, and the 1990
amendments.
Prior to the adoption of the "Federal Manual for Identifying and
Delineating Jurisdictional Wetlands" by the four agencies in
1989, each agency had its own procedures for identifying and
delineating wetlands. The CE and EPA developed technical manuals
for identifying and delineating wetlands subject to Section 404
(Environmental Laboratory 1987 and Sipple 1988, respectively),
yet neither manual was a nationally-implemented standard even
within the agencies. Consequently, wetland identification and
delineation remained inconsistent. The SCS developed procedures
for identifying wetlands for compliance with "Swampbuster" which
were adopted by the agency for national use in 1987 (7 CFR Part .
12). While it has no formal method for delineating wetland
boundaries, the FWS has established guidelines for identifying
wetlands in the form of its official wetland classification
system report (Cowardin, et al. 1979) . These varied agency
approaches and lack of standardized methods resulted in
inconsistent determinations of wetland boundaries for the same
type of area. This created confusion and identified the need for
a single, consistent approach for wetland determinations and
boundary delineations.
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In early 1988, the CE and EPA resumed previous discussions on the
possibilities of merging their manuals into a single document and
establishing it as a national standard within the agencies, since
both manuals were produced in support of Section 404 of the Clean
Water Act. The FWS and SCS were invited to participate, thereby
creating the Federal Interagency Committee for Wetland
Delineation (Committee) with each of the four agencies (CE, EPA,
FWS, and SCS) represented.
The four agencies reached agreement on the technical criteria for
identifying and delineating wetlands and merged their methods
into a single wetland delineation manual, which was published on
January 10, 1989 as the "Federal Manual for Identifying and
Delineating Jurisdictional Wetlands". This established a
national standard for wetland identification and delineation, and
terminated previous locally implemented approaches that were not,
in some cases, scientifically based nor consistent. Further,
adoption of the manual in 1989 resulted in some changes in the
scope of regulatory jurisdiction in some agency field offices.
During the following two years, the 1989 manual was used by the
agencies for wetland delineation, chiefly for identifying and
delineating wetlands subject to federal regulations under the
Clean Water Act. Unfortunately, during this time many
misconceptions about the intent of the 1989 manual,
misapplication of the 1989 manual (e.g., classifying any area
mapped as hydric soil as wetland without considering other
criteria), and other factors created an obvious need to review
the 1989 manual and revise it accordingly. From the outset, the
Committee recognized that additional clarification and/or changes
might be required.
Accordingly, in May 1990, the Committee initiated an evaluation
of the 1989 manual, which consisted of several steps:
1. Formal field testing was conducted by the Environmental
Protection Agency to evaluate the sampling protocols of
the 1989 manual (Sipple and DaVia 1990);
2. Reviews by agency field staff using the 1989 manual;
3. To afford the public the opportunity to comment on the
technical aspects of the 1989 manual, public meetings
were held in Baton Rouge, Louisiana, Sacramento,
California, St. Paul, Minnesota, and Baltimore,
Maryland; and
4. Written comments on the technical aspects of the 1989
manual were also accepted subsequent to the meetings to
give the public ample opportunity to express any
concerns. More than 500 letters were received and
reviewed.
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The technical comments were reviewed by the Committee and
considered.for incorporation into a revised manual. The Agencies
concluded that while the manual represented a substantial
improvement over pre-existing approaches, several key issues
needed to be re-examined and clarified. Some of the key technical
issues needing re-examination were: (1) the wetland hydrology
criterion, (2) the use of hydric soil for delineating the wetland
boundary, (3) the assumption that facultative vegetation
indicated wetland hydrology, and (4) the open-ended nature of the
determination process which created opportunities for misuse.
The wetland hydrology criterion in the 1989 manual included a
series of requirements related to specific soil types (soil
drainage classes). Looking for water tables at various depths
depending on soil drainage class was confusing, especially since
properties associated with soil drainage classes are not
standardized across the country. The National Technical
Committee for Hydric Soils (NTCHS) criteria for defining hydric
soils were adopted in the 1989 manual. The hydric soil criterion
included wetland hydrology requirements to identify those soils
wet enough to be hydric. In adopting the NTCHS hydric soil
criteria, the 1989 manual retained the hydrology requirements
under its hydric soil criterion and also in effect, repeated them
as the wetland hydrology criterion. This clearly gave the
impression of a less than three criteria approach to wetland
identification.
Perhaps the issue that engendered the most concern over potential
misuse of the 1989 manual involved the use of hydric soils for
wetland identification and delineation. Since the 1989 manual
included wetland hydrology requirements within the hydric soil
criterion, and the delineation methods relied on hydric soil
properties to delineate the wetland boundary, some users got the
impression that the.1989 manual was not based on three mandatory
criteria, but rather based solely on one criterion - the hydric
soil criterion (since it, in fact, embodied the wetland hydrology
criterion). This, by itself, was not a significant problem,
since hydrology was still considered. Some users then
erroneously translated this to mean that any area mapped as a
hydric soil series was a wetland. However, it was the clear
intent of the agencies that specific soil properties derived
directly from wetland hydrology (e.g., significant soil
saturation) would be used to separate those members of hydric
soil series that were associated with wetlands from those that
were not. Hydric soil mapping units include significant acreage
of phases of these soils that were never wetland or no longer
meet the wetland hydrology requirements of the hydric soil
criterion (i.e., dry phases and drained phases, respectively) as
well as inclusions of nonhydric soils.
By considering any mapped hydric soil area as wetland, millions
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of former wetlands (now effectively drained) could be
misidentified as wetland. This grossly exaggerated the extent of
"jurisdictional wetlands" present in the United States. While
the presence of certain plants were required to separate
vegetated wetlands from nonvegetated wetlands, they were not used
to help identify the upper boundaries, although they can be very
useful indicators in certain cases where hydrology has been
altered or where soil properties themselves are difficult to
interpret. Consequently, by ignoring plant composition on the
upper end of the wetland/upland gradient and by erroneously using
mapped boundaries of hydric soil units to delineate wetland
boundaries, errors in judgment were possible.
The 1989 manual specified three mandatory criteria, but did not
require the use of various indicators to verify these criteria,
although the interrelationships were presented. This allowed
individuals to develop their own indicators or ignore strong
indicators in determining whether a particular criterion was met.
Clearly, the criteria needed to be intricately linked to a
limited set of field indicators to prevent their misuse.
A series of meetings of the Committee were held during the period
of October 1990 through April 1991. Major revisions to the 1989
manual were made to correct the technically-based shortcomings
addressed above, reduce misinterpretations and the possibility of
erroneous wetland determinations, and better explain the manual's
usage.
Federal Wetland Definitions
Several definitions have been formulated at the Federal level to
define "wetland11 for various laws, regulations, and programs.
These definitions are cited below with reference to their guiding
document along with a few comments on their key elements.
Section 404 of the Clean Water Act
The following definition of wetland is the regulatory definition
used by the EPA and CE for administering the Section 404 permit
program:
Those areas that are inundated or saturated by surface or
groundwater at a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence of
vegetation typically adapted for life in saturated soil
conditions. Wetlands generally include swamps, marshes, bogs,
and similar areas (EPA, 40 CFR 230.3, December 24, 1980; and CE,
33 CFR 328.3, November 13, 1986).
This definition emphasizes hydrology, vegetation, and saturated
soils. The Section 404 regulations also deal with other "waters
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of the United States" such as open .water areas, mud flats, coral
reefs, riffle and pool complexes, vegetated shallows, and other
aquatic habitats. Both EPA and CE regulations (cited above)
implementing this definition were subject to formal rulemaking
public notice and comment procedures in accordance with the
Administrative Procedures Act (5 USC 553).
Food Security Act of 1985 (as amended)
The following wetland definition is used by the SCS for
identifying wetlands on agricultural land in assessing fanner
eligibility for U.S. Department of Agriculture program benefits
under the "Swampbuster" provision of this Act:
Wetlands are defined as areas that have a predominance of hydric
soils and that are inundated or saturated by surface or ground
water at a frequency and duration sufficient to support, and
under normal circumstances do support, a prevalence of
hydrophytic vegetation typically adapted for life in saturated
soil conditions, except lands in Alaska identified as having a
high potential for agricultural development and a predominance of
permafrost soils.* (National Food Security Act Manual, 1988 and
revised editions)
*Special Note: The Emergency Wetlands Resources Act of 1986 also
contains this definition, but without the exception for Alaska.
This definition specifies hydrology, hydrophytic vegetation, and
hydric soils. Any area that meets the hydric soil criteria
(defined by the National Technical Committee for Hydric Soils) is
considered to have a predominance of hydric soils. The
definition also makes a geographic exclusion for Alaska, so that
wetlands in Alaska with a high potential for agricultural
development and a predominance of permafrost soils are exempt
from the requirements of the Food Security Act.
Fish and Wildlife Service's Wetland Classification System
The FWS in cooperation with other Federal agencies, State
agencies, and private organizations and individuals developed a
wetland definition for conducting an inventory of the Nation's
wetlands. This definition was published in the FWS's publication
"Classification of Wetlands and Deepwater Habitats of the United
States" (Cowardin, et al. 1979):
Wetlands are lands transitional between terrestrial and aquatic
systems where the water table is usually at or near the surface
or the land is covered by shallow water. For purposes of this
classification wetlands must have one or more of the following
three attributes: (1) at least periodically, the land supports
predominantly hydrophytes, (2) the substrate is predominantly
undrained hydric soil, and (3) the substrate is nonsoil and is
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saturated with water or covered by.shallow water at some time
during the growing season of each year.
This definition includes both vegetated and nonvegetated
wetlands, recognizing that some types of wetlands lack vegetation
(e.g., mud flats, sand flats, rocky shores, gravel beaches, and
sand bars). The classification system also defines "deepwater
habitats" as "permanently flooded lands lying below the deepwater
boundary of wetlands." Deepwater habitats include estuarine and
marine aquatic beds (similar to "vegetated shallows" of Section
404) , although aquatic beds in shallow fresh water are considered
wetlands. Open waters below extreme low vater at spring tides in
salt and brackish tidal areas and usually below 6.6 feet in
inland areas and freshwater tidal areas are also included in
deepwater habitats.
Relationship of Wetlands Identified by this Manual to "Waters of
the United States"
This manual is used to identify and delineate vegetated wetlands.
Figure 1 presents a generalized landscape continuum from upland
to open water (deepwater habitat) showing the relationship of the
various Federal wetland definitions. Vegetated wetlands as used
herein means areas that, under normal circumstances, usually have
hydrophytic vegetation, hydric soil, and wetland hydrology.
Further, this manual applies to areas that are vegetated by
erect, self-supporting vegetation (e.g., vegetation extending
above the water's surface in aquatic areas or free-standing on
soil).
Vegetated wetlands are a subset of areas regulated as "Waters of
the United States" under Section 404 of the Clean Water Act, and
one of the areas regulated as "special aquatic sites" under the
Section 404(b)(l) Guidelines promulgated by the Environmental
Protection Agency. Other "special aquatic sites" include
mudflats, vegetated shallows, coral reefs, riffle and pool
complexes, and sanctuaries and refuges. Open water areas are
also part of the "Waters of the United States."
Vegetated wetlands are also a subset of those areas designated as
wetlands under the FHS's "Classification of Wetlands and
Deepwater Habitats of the United States." The FWS definition of
wetland is used for National Wetlands Inventory and is
nonregulatory in nature. The only differences between wetlands
identified by FWS and this manual are those aquatic areas 6.6
feet or less in depth that do not contain emergent vegetation, or
are unvegetatebT. Such areas are identified as wetlands under the
FWS system, but not under the manual. However, there are few if
any areas covered by the FWS classification system that are not
covered under Section 404. For vegetated wetlands, the FWS
classification system and this manual are essentially identical.
Ninety-four percent of all FWS-classified wetlands in the
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coterminous United States are vegetated.
The emphasis of this manual is on the boundary between wetland
and upland, since that is the area most often in question and
where determinations and delineations become most difficult.
However, wetland determinations in lower wetter areas are
generally easy to make and seldom in question from a regulatory
standpoint since both wetland and open water are regulated areas.
Generally, as one moves up slope, it becomes increasingly more
difficult to determine what areas are wetlands. This manual
recognizes this fact and requires less rigorous investigation in
obvious wetland situations than in areas which may be
questionable. In either situation, however, documentation
supporting a delineation is required.
This manual does not change the existing definitions of wetlands
used for Section 404 of the Clean Water Act and the Swampbuster
provision of the 1985 Food Security Act, as amended, or the FWS
wetland definition. The former two definitions are specific to
vegetated wetlands or wetlands that are vegetated under normal
circumstances. These are the wetlands to which the manual
applies. This manual provides for the consistent identification
and delineation of these wetlands in the field. Because this
manual was developed to resolve differences in identifying
wetlands under these definitions, it is limited to vegetated
wetlands and does not address nonvegetated wetlands.
Wetland determinations made through the use of this manual for
the purposes of determining Federal wetland jurisdiction at a
site are subject to modification in accordance with legal and
policy considerations of the applicable regulatory program. For
example, Section 404 regulatory jurisdiction in wetlands is
limited to areas that are waters of the United States because
they have a connection with interstate or foreign commerce.
Another example is the application of Federal wetland
jurisdiction on cropland which is subject to agency policy-based
interpretations of such matters as the relative permanence of the
cropping disturbance and its effect on hydrophytic vegetation
and/or wetland hydrology.. Such matters generally are not
addressed in this manual; rather, the appropriate agency policy
should be consulted in conjunction with the manual for wetland
determinations in such areas.
Summary of Federal Definitions
The CE, EPA, and SCS wetland definitions include only areas that
are vegetated'under normal circumstances, while the FWS
definition encompasses both vegetated and nonvegetated areas.
Except for the FWS inclusion of nonvegetated areas and aquatic
beds in shallow water as wetlands and the exemption for Alaska in
the SCS definition, all four wetland definitions are conceptually
the same; they all include three basic elements - hydrology,
vegetation, and soils - for identifying wetlands.
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PART II.
MANDATORY TECHNICAL CRITERIA FOR
VEGETATED WETLANDS IDENTIFICATION
Wetland hydrology is the driving force of wetlands. Vegetated
wetlands occur in shallow water, on permanently saturated soils,
or in areas subject to periodic inundation or saturation, where
anaerobic conditions usually develop due to excess water.
Certain hydrologic conditions called "wetland hydrology"
therefore drive the formation of wetlands and continue to.
maintain them. Permanent or periodic wetness is the fundamental
factor that makes wetlands different from uplands (nonwetlands) .
Although wetland hydrology is the dominant force creating
wetlands, long-term records for hydrology typically are not
available for identifying the presence of wetlands or for
delineating their upper boundaries. Consequently other
indicators sometimes must be used to determine whether an area
meets the wetland criteria. It has been long recognized that
various plants and their adaptations, certain plant communities,
specific soil properties, and particular soil types (e.g., peats,
mucks, and gleyed soils) can be used to help identify wetlands.
In addition, there are a number of hydrologic indicators that can
be used to help identify wetlands.
Existing wetland definitions recognize that wetlands are driven
by wetland hydrology (permanent or periodic inundation and/or
soil saturation) and that characteristic plants (hydrophytic
vegetation) and soils (hydric soils) are identifiable components
of vegetated wetlands. This manual uses these three components
as criteria for vegetated wetland identification. Field staff
should examine sites for indicators of hydrophytic vegetation,
hydric soils, and wetland hydrology and document the presence or
absence of indicators to the extent practicable. At sites where
wetlands are obvious due to the overwhelming evidence provided by
one indicator (e.g., large stands of undisturbed salt marsh),
documentation of the other indicators, while necessary, need not
be as intensive as in areas where wetlands are not so obvious.
There are, however, many other cases where, as one moves toward
the drier portion of the moisture gradient, rigorous examination
and documentation of soil, vegetation, and hydrology
characteristics is necessary. The fact that such wetlands are
difficult to identify has no bearing on their status as wetlands.
Under natural, undisturbed conditions, vegetated wetlands
generally possess three characteristics: (1) hydrophytic
vegetation, (2) hydric soils, and (3) wetland hydrology. These
characteristics and their technical criteria for identification
purposes are described in the following sections. The three
technical criteria and their verifying characteristics are
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mandatory. For an area to be identified as a wetland, all three
criteria must be met by positive identification of the presence
of one or more of the indicators described below for each
criterion, with two noted exceptions: wetlands in disturbed
conditions such that indicators of one or more of the criteria
are absent; and wetlands that are difficult to identify because
natural fluctuations in hydrology or climate or other site-
specific or unusual conditions prohibit their identification
based on the standard criteria and indicators. The procedures to
be used for identifying and delineating wetlands in areas that
potentially fall within each of these categories of exceptions
are included as an Appendix to this manual. Representative
examples of difficult-to-identify wetlands are also discussed in
this manual. Included with these examples are situations (e.g.,
pit and mound topography) encountered in the field that
complicate the wetland delineation process.
The three mandatory technical criteria are presented below.
Background information for each criterion is also provided.
WETLAND HYDROLOGY CRITERION
An area has wetland hydrology when it is:
1. Inundated and/or saturated at the surface by surface
water or ground water for more than 14 consecutive days
during the growing season in most years, or
2. Periodically flooded by tidal water in most years.
Areas meeting this criterion also are usually inundated or
saturated for variable periods during the non-growing season.
The term "inundated and/or saturated at the surface" means the
soil is inundated or wet enough at the surface to the extent that
water reaches the surface in an unlined borehole or can be
squeezed or shaken from the soil at the surface. The growing
season is the interval between 3 weeks before the average date of
the last killing frost in the Spring to 3 weeks after the average
date of the first killing frost in the Fall, with exceptions for
areas experiencing freezing temperatures throughout the year
(e.g., montane, tundra and boreal areas) that nevertheless
support hydrophytic vegetation. The term "in most years" means
that the condition would occur more than 50 years out of 100
years and, therefore, represents the prevailing long-term
hydrologic condition.
While the above criterion must be met, many times field staff
will not be present to do wetland determinations at the right
time of year or for long enough to directly observe more than two
weeks of inundation and/or saturation. Accordingly, field
personnel need to use indicators of wetland hydrology as a basis
for professional judgment on whether the hydrology criterion is
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met.
An area meets the wetland hydrology criterion above by direct
measurement of inundation and/or soil saturation or tidal
flooding or as documented by one or more of the following
indicators (also see note on page 13):
1. A minimum of 3 years of hydrologic records (e.g.,
groundwater well observations following the protocol on
page 99, or tide or stream gauge records) collected
during years of normal rainfall (amount and monthly
distribution) and correlated with long-term hydrologic
records for the specific geographical area that
demonstrates the area meets the wetland hydrology
criterion; or
2. Examination of aerial photography (preferably early
spring or wet part of the growing season) for a minimum
of 5 years reveals evidence of inundation and/or
saturation in most years (e.g., 3 of 5 years or 6 of 10
years) and correlated with long-term hydrologic records
for the specific geographical areas demonstrate that
the area meets the wetland hydrology criterion; or
3. One or more primary hydrologic indicators below, which,
when considered with evidence of frequency and duration
of rainfall or other hydrologic conditions, provide
evidence sufficient to establish that more than 14
consecutive days of inundation and/or saturation at the
surface during the growing season occurs, are
materially present:
a. Surface water inundation; or
b. Observed free water at the surface in an unlined
borehole; or
c. water can be squeezed or shaken from a soil sample
taken at the soil surface; or
d. Oxidized stains along the channels of living roots
(Oxidized rhizospheres); or
e. Sulfidic material (distinct hydrogen sulfide,
rotten egg odor) within 12 inches of the soil
surface; or
f. Water-stained leaves, trunks or stems that are
grayish or blackish in appearance as a result of
being underwater for significant periods; or
g. Specific plant morphological adaptation/responses
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to prolonged inundation or saturation:
pneumatophores, prop roots, hypertrophied
lenticels, arenchymous tissues, and floating stems
and leaves of floating-leaved plants growing in
the area (may be observed lying flat on the soil),
arid buttressed trunks or stems.
Always consider the frequency and duration of these
primary indicators (or of the wetness that created
them), and whether significant hydrologic modification
(e.g., drainage) has effectively removed wetland
hydrology from the site. Inundation for seven
consecutive days during the growing season generally
results in saturation at the surface for a total of
more than 14 consecutive days. However, certain
inundated wetlands (e.g., some prairie potholes, playa
lakes and vernal pools) exhibit anaerobic conditions at
the surface but may not have 7 days of saturation at
the surface following 7 days of inundation. These and
other exceptions are addressed on page 31 below as
difficult-to-identify wetlands.
4. If none of the indicators in items I, 2, or 3 above is
present, one or more of the following secondary
hydrologic indicators should be used in conjunction
with collateral information (e.g., maps) that supports
a wetland hydrology determination:
a. Silt marks (waterborne silt deposits) that
indicate inundation; or
b. Drift lines; or
c. Surface-scoured areas; or
d. Other common plant morphological
adaptations/responses to hydrology: shallow root
systems and adventitious roots.
These secondary indicators may only be used in
conjunction with other collateral information that
indicates wetland hydrology (e.g., regional indicators
of saturation, hydrologic gauge data, county soil
surveys, National Wetlands Inventory maps, aerial
photographs, or reliable persons with local knowledge
of inundation and/or saturated conditions). This type
of information may also can be used to support
determinations based on the primary indicators listed
above.
NOTE: IN ADDITION, CERTAIN SEASONALLY-SATURATED WETLANDS MAY
LACK THE ABOVE HYDROLOGIC INDICATORS DURING A PORTION OF THE
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GROWING SEASON DUE TO SEASONAL DRYNZSS OR OTHER NORMAL HYDROLOG1C
FLUCTUATIONS. SUCH AREAS ARE LISTED AS DIFFICULT-TO-IDENTIFY
WETLANDS (See Page 31) . UNLESS SPECIFICALLY ADDRESSED IN THE
DIFFICULT-TO-IDENTIFY OR DISTURBED AREAS SECTIONS OF THE MANUAL,
AREAS WITHOUT ANY -OF THE ABOVE HYDROLOGIC INDICATORS ARE
NONWETLAND. IN AREAS OF SUSPECTED SIGNIFICANT HYDROLOGIC
MODIFICATION, FOLLOW THE DISTURBED AREA PROCEDURES TO DETERMINE
IF WETLAND HYDROLOGY STILL EXISTS PAGE 41.
Wetland Hydrology Background
The driving force creating wetlands is "wetland hydrology," that
is, permanent or periodic inundation, or soil saturation for a
significant period (two weeks or more) during the growing season.
Many wetlands are found along rivers, lakes, and estuaries where
flooding is likely to occur, while other wetlands form in
isolated depressions surrounded by upland where surface water
collects. Still others develop on slopes of varying steepness,
in surface water drainageways, or where ground water discharges
to the land surface in spring or seepage areas. Thus, landscape
position provides much insight into whether an area is likely to
be subjected to wetland hydrology.
Permanent or periodic inundation, or soil saturation at the
surface, at least seasonally, are the driving forces behind
wetland formation. The presence of water in the soil for two
weeks or more during the growing season typically creates
anaerobic conditions, which affect the types of plants that can
grow and the types of soils that develop. These conditions hold
true for most wetlands, especially those at the upper end of the
soil moisture gradient. Anaerobiosis does not necessarily occur
in all wetlands and those where it nay not occur include
vegetated sand bars, seepage areas, springs, and the upper edges
of salt marshes. These exceptions are addressed below as
difficult-to-identify wetlands. Wetlands have at least a
seasonal or periodic abundance of water. For example, this water
may come from direct precipitation, overbanX flooding, surface
water runoff due to precipitation or snow melt, ground water
discharge, tidal flooding, irrigation, or other human-induced
activities. The frequency and duration of inundation and soil
saturation vary widely from permanent flooding or saturation to
irregular flooding or saturation. Of the three technical
criteria for wetland identification, wetland hydrology is often
the least exact and most difficult to establish in the field, due
largely to annual, seasonal, and daily fluctuations.
Numerous factors influence the wetness of an area, including
precipitation, stratigraphy, topography, soil permeability, and
plant cover. The frequency and duration of inundation or soil
saturation are important in separating wetlands from nonwetlands.
Areas of lower elevation in a floodplain or marsh usually have
longer duration of inundation and saturation and often more
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frequent periods of these conditions than most areas at higher
levels. Floodplain configuration may significantly affect the
duration of inundation by facilitating rapid runoff or by causing
poor drainage.
Soil permeability related to the texture of the soil also
influences the duration of inundation or soil saturation. For
example, clayey soils absorb water more slowly than sandy or
loamy soils, and therefore have slower permeability and remain
saturated much longer.
Type and amount of plant cover affect both the degree of
inundation and the duration of saturated soil conditions. Excess
water drains more slowly in areas of abundant plant cover,
thereby increasing duration of inundation or soil saturation. On
the other hand, transpiration rates are higher in areas of
abundant plant cover, which may reduce the duration of soil
saturation.
To determine whether the wetland hydrology criterion is met, one
should consider recorded data, aerial photographs, and observed
field conditions that provide direct or indirect evidence of
inundation or soil saturation. Prolonged saturation often leaves
evidence of such wetness in the soil (e.g., sulfur odor) and
these properties are useful for verifying wetland hydrology
provided the area's hydrology has not been significantly modified
on-site or upstream in the watershed. If the hydrology has been
significantly disturbed, particular care must be taken in
assessing the wetland hydrology criterion; refer to disturbed
area procedures (p. 41) to determine whether wetland hydrology
still exists.
Measuring Wetland Hydrology
In certain instances, especially disturbed situations, it may be
necessary to determine an area's hydrology by actively collecting
on-site hydrologic data from direct measurements or observations.
The duration and frequency of inundation by flooding may be
established by evaluating long-term stream or tide gauge data or
by examining aerial photos covering at least a 5-year period and
comparing results with the wetland hydrology criterion.
Saturation at the surface may be determined by making
observations in an unlined borehole and establishing whether or
not the soil is saturated at the surface for more than 14 days
during the growing season. A procedure for this is presented in
the Disturbed Areas section of the manual (p. 41). In general, if
soil saturation is observed at the surface for more than 14 days .
during the growing season wetland hydrology probably exists.
Interpretation of the above observations, however, must always be
done with consideration of recent rainfall conditions (e.g.,
within the past few weeks) as well as the long-term rainfall
patterns (e.g., abnormally wet or dry periods) preceding and
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during the time the hydrologic data were recorded.
Historical Recorded Hydrologic Data
Historical recorded hydrologic data usually provide both short-
and long-term information on the frequency and duration of
flooding, but little or no information on soil saturation
periods. Historical recorded data include stream gauge data,
lake gauge data, tide gauge data, flood predictions, and .
historical flood records. Use of these data is commonly limited
to areas adjacent to streams and other similar areas. Recorded
data may be available from the following sources: (1) CE district
offices (data for major waterbodies and for site-specific areas
from planning and design documents), (2) U.S. Geological Survey
(stream and tidal gauge data), (3) National Oceanic and
Atmospheric Administration (tidal gauge data), (4) State, county
and local agencies (flood data), (5) SCS state offices (small
watershed projects and water table study data), and (6) private
developers or landowners (site-specific hydrologic data, which
may include water table or groundwater well data).
Aerial Photographs
Aerial photographs may provide direct evidence of inundation or
soil saturation at the surface in an area. Inundation (flooding
or ponding) is best observed during the early spring in temperate
and boreal regions when snow and ice are gone and leaves of
deciduous trees and shrubs are not yet fully developed. This
allows detection of wet soil conditions that would be obscured by
the tree or shrub canopy at full leaf-out. For marshes, this
season of photography is also desirable, except in regions
characterized by distinct dry and rainy seasons, such as southern
Florida and California. Wetland hydrology would be best observed
during the wet season in these latter areas.
It is most desirable to examine several consecutive years of
early spring or wet season aerial photographs to document
evidence of wetland inundation or soil saturation. In this way,
the effects of abnormally dry or wet springs, for example, may be
minimized. In interpreting aerial photographs, it is important to
know the antecedent weather conditions. This will help eliminate
potential misinterpretations caused by abnormally wet or dry
periods. Contact the U.S. Weather Service for historical weather
records or the U.S. Geological Survey for hydrologic records.
Aerial photographs for agricultural regions of the country are
often available at county offices of the Agricultural
Stabilization and Conservation Service.
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Field Observations
Direct Evidence of Water
At certain times of the year in wetlands, and in certain types of
wetlands at most times, wetland hydrology is quite evident, since
surface water or saturated soils (e.g., soggy or wetter
underfoot) may be observed. The most obvious and revealing
hydrologic indicator may be simply observing the areal extent of
inundation. However, both seasonal conditions and recent weather
conditions must be considered when observing an area because they
can affect the presence of surface water on wetland and
nonwetland sites. In many cases, soils saturated at the surface
are obvious, since the ground surface is soggy or mucky under-
foot.
To observe free water at the surface it may be necessary to dig a
hole and observe the level at which water stands in the hole
after sufficient time has been allowed for water to drain into
the hole. In some cases, the upper level at which water is
flowing into the hole can be observed by examining the walls of
the hole. This level may represent the depth to the water table.
In some heavy clay soils, however, water nay not rapidly
accumulate in the hole even when the soil is saturated. When
attempting to observe free water in a bore hole, adequate time
should be allowed for water in the hole to reach equilibrium with
the water table.
Soil saturation at the surface may be detected by a "squeeze
test" or "shake test" which involve taking a surface soil sample
and squeezing or shaking the sample. If water can be extracted,
the soil is considered saturated at the surface.
When evaluating soil saturation, both the season of the year and
the preceding weather conditions must be considered, since excess
water may not be present during parts of the growing season in
some wetlands due to high evaporation and plant transpiration
rates which effectively lower the water table. At such times,
other indicators of wetland hydrology nay be present.
Other Signs of Wetland Hydrology
It is not necessary to observe inundation or saturation at the
time of field inspection to identify wetland hydrology so long as
indicators are sufficient to demonstrate to field personnel that
the wetland hydrology criterion on page 10 is met. Other signs
of wetland hydrology may be observed, e.g., oxidized rhizospheres
(root channels) and water-stained leaves or stems.
Some plants are able to survive saturated soil conditions (i.e.,
a reducing environment) because they can transport oxygen to
their root zone. Iron oxide concretions (orangish or reddish
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brown in color) may form along the channels of living roots and
rhizomes creating oxidized rhizospheres that provide evidence of
soil saturation (anaerobic conditions) for a significant period
during the growing season. Ephemeral or temporary oxidized
rhizospheres may develop after abnormally heavy rainfall periods.
Consequently/ oxidized rhizospheres are most meaningful when
observed with other wetland indicators especially in undrained
soils displaying diagnostic hydric soil properties.
Forested wetlands that are inundated earlier in the year will
frequently have trees and shrubs with water-stained trunks or
stems if flooded for long periods, or water-stained leaves in
depressions on the forest floor. The stems are usually black-
colored to the normal high water mark. The leaves are generally
grayish or blackish in appearance, darkened from being underwater
for significant periods.
Other signs that may reflect wetland hydrology include water
marks, drift lines, water-borne deposits, surface-scoured areas,
wetland drainage patterns, and certain plant morphological
adaptations.
('!) Water marks are found most commonly on woody vegetation
or fixed objects (e.g., bridge pillars, buildings, and
fences) but may also be observed on other vegetation. They
often occur as dark stains on bark or other fixed objects.
02) Drift lines are typically found adjacent to streams or
other sources of water flow in wetlands and often occur in
tidal marshes. Evidence consists of deposition of debris in
a line on the wetland surface or debris entangled in
aboveground vegetation or other fixed objects. Debris
usually consists of remnants of vegetation (branches, stems,
and leaves), litter, and other water-borne materials often
deposited more-or less parallel to the direction of water
flow. Drift lines provide an indication of the minimum
portion of the area inundated during a flooding event; the
maximum level of inundation is generally at a higher
elevation that indicated by a drift line. The drift lines
in tidal wetlands are often referred to as "wrack
lines."
03) Water-borne deposits of mineral or organic matter may be
observed on plants and other objects after inundation. This
evidence may remain for a considerable period before it is
removed by precipitation or subsequent inundation. Silt
deposition on vegetation and other objects provides an
indication of the minimum inundation level. When the
deposits are primarily organic (e.g., fine organic material
and algae), the detritus may become encrusted on or slightly
above the soil surface after dewatering occurs. Sediment
deposits (e.g., sandy material) along streams provide
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'\J
evidence of recent overbank flooding.
(4) Surface scouring occurs along floodplains where overbank
flooding erodes sediments (e.g., at the bases of trees).
The absence of leaf litter from the soil surface is also
sometimes an 'indication of surface scouring. Forested
wetlands that contain standing waters for relatively long
duration will occasionally have areas of bare or essentially
bare soil, sometimes associated with local depressions.
(5) Many plants growing in wetlands have developed
morphological features in response to inundation or soil
saturation. Examples include pneumatophores (e.g., cypress
knees), prop roots, floating stems and leaves, hypertrophied
lenticels (oversized stem pore), aerenchyma (air-filled)
tissue in roots and stems, buttressed tree trunks, multiple
trunks, adventitious roots, shallow root systems,
polymorphic leaves, inflated leaves, stems or roots.
Pneumatophores, prop roots, floating steins and leaves,
hypertrophied lenticels, aerenchyma tissue, and buttresssed
tree trunks develop virtually only in wetland or aquatic
environments and therefore are listed as primary hydrologic
indicators in the wetland hydrology criterion. When these
features are observed in young plants, they provide good
evidence that wetland hydrology exists. Multiple trunks,
adventitious roots, shallow root systems, polymorphic
leaves, inflated leaves, stems or roots are commonly found
in many wetland plants, yet not exclusive to them, and
therefore are listed as secondary hydrologic indicators in
the wetland hydrology criterion and indicate wetlands only
when accompanied by other collateral information that
indicates wetland hydrology.
HYDROPHYTZC VEGETATION CRITERION
An area meets the hydrophytic vegetation criterion when, under
normal circumstances:
(1) more than 50 percent of the dominant species from all
strata are obligate wetland (OBL), facultative wetland (FACW),
and/or facultative (FAC) species, or
(2) 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).
NOTE: WETLAND TYPES THAT MAY HAVE VEGETATION THAT DOES NOT MEET
THIS CRITERION ARE LISTED AS DIFFICULT-TO-IDENTIFY WETLANDS (SEE
PAGE 31). AREAS WHERE THE VEGETATION HAS BEEN REMOVED WILL
GENERALLY MEET THE HYDROPHYTIC VEGETATION CRITERIA IF THEY ARE
CAPABLE OF SUPPORTING SUCH VEGETATION. (SEE DISTURBED AREAS
. 18
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SECTION, PAGE 41)
For each stratum (e.g., tree, shrub, and herb) in the plant
community, dominant species are determined by ranking all species
in descending order of dominance (e.g., areal cover or basal
area) and cumulatively totaling species until they exceed 50
percent of the total dominance measure (e.g., total areal
coverage or total basal area for a sample plot). All species
that contribute to exceeding the 50 percent level are considered
dominant species. Any additional species comprising 20 percent
or more of the total dominance measure for the stratum is also
considered a dominant species. All dominants, regardless of
stratum, are treated equally in determining the presence of
hydrophytic vegetation. A valid stratum for identifying
dominants in the plant community must have at least 5 percent
areal cover within the observation area (e.g., plot).
Hydrophytic Vegetation Background
The term "hydrophytic vegetation" describes 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 submerged substrates, or in soil or on a substrate
that is at least periodically anaerobic (deficient in oxygen) as
a result of excessive water content. All plants growing in
wetlands have adapted in one way or another to life in
permanently or periodically inundated or saturated soils. Some
plants have developed structural or morphological adaptations to
inundation or saturation, while others have broad ecological
tolerances (Tiner, 1991). Some of these features are used as
indicators of wetland hydrology in this manual (see hydrology
criterion page 10), since they are a response to inundation
and/or soil saturation. Probably all plants growing in wetlands
possess physiological mechanisms to cope with periodic anaerobic
soil conditions or 1-ife in water. Because they are not
observable in the field, physiological and reproductive
adaptations are not included in this manual.
Persons making wetland determinations should be able to identify
at least the dominant wetland plants in each stratum (layer of
vegetation) of a plant community. Plant identification requires
the use of field guides or more technical taxonomic manuals (see
Appendix for sample list). When necessary, seek help in
identifying difficult species. Once a plant is identified to
genus and species, consult the appropriate Federal list of plants
that occur in wetlands to determine the "wetland indicator
status" of the plant (see explanation below). This information
will be used to help determine whether the hydrophytic vegetation
criterion is met.
One should also become familiar with the technical literature on
wetlands, especially for one's geographic region. Sources of
i
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available literature include: taxonomic plant manuals and field
guides; scientific journals dealing with botany, ecology, and
wetlands in particular; technical government reports on wetlands;
proceedings of wetland workshops, conferences, and symposia; and
the FWS's national- wetland plant database, which contains habitat
information on about 7,000 plant species. Appendix presents
examples of the first four sources of information. In addition,
the FWS's National Wetlands Inventory (NWI) maps provide .
information on locations of hydrophytic plant communities that
can be studied in the field to improve one's knowledge of such
communities in particular regions.
If all wetland plant species grew only in wetlands, plants alone
could be used to identify and delineate wetlands. However, of
the nearly 7,000 vascular plant species which have been found
growing in U.S. wetlands (Reed 1988), only about 27 percent are
"obligate wetland" species that nearly always occur in wetlands
under natural conditions. This means that the majority of plant
species growing in wetlands also grow in nonwetlands to varying
degrees. These plants may or may not be hydrophytes depending on
where they are growing. This variability in habitat occurrence
causes certain difficulties in identifying wetlands from a purely
botanical standpoint in many cases. This is a major reason for
evaluating soils and hydrology when identifying wetlands.
National List of Wetland Plant Species
The FWS in cooperation with CE, EPA, and SCS has published the
"National List of Plant Species That Occur in Wetlands" from a
review of the scientific literature and review by selected
wetland experts and botanists (Reed 1988). The list separates
vascular plants into four basic groups, commonly called "wetland
indicator status," based on a plant species' frequency of
occurrence in wetlands: (1) obligate wetland plants (OBL) that
occur almost always*(estimated probability >99%) in wetlands
under natural conditions; (2) facultative wetland plants (FACW)
that usually occur in wetlands (estimated probability 67-99%),
but occasionally are found in nonwetlands; (3) facultative plants
(FAC) that are nearly equally likely to occur in wetlands or
nonwetlands (estimated probability 34-66%); and (4) facultative
upland plants (FACU) that usually occur in nonwetlands (estimated
probability 67-99%), but occasionally are found in wetlands
(estimated probability 1-33%). If a species occurs almost always
(estimated probability >99%) in nonwetlands under natural
conditions, it is considered an obligate upland plant (UPL).
These latter plants do not usually appear on the wetland plant
list; they are listed only in some regions of the country. If a
species is not on the list, it is presumed to be an obligate
upland plant, yet be advised that the list intentionally does not
include nonvascular plant species (e.g., algae and mosses) or
epiphytic plants. These omitted plants should not be considered
in determining whether the hydrophytic vegetation criterion is
*
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met, unless one has particular knowledge of their frequency of
occurrence in wetlands. Also be sure to check for synonyms in
plant scientific names, since the nomenclature used in the list
varies for some species from that used in regional taxonomic
manuals or commonly used plant identification field guides.
The "National List of Plant Species That Occur in Wetlands" has
been subdivided into regional and state lists. There is a formal
procedure to petition the interagency plant review committee for
making additions, deletions, and changes in indicator status.
Since the lists are periodically updated, the U.S. Fish and
Wildlife Service should be consulted to be sure that the most
current version is being used for wetland determinations.' The
appropriate plant list for a specific geographic region should be
used when making a wetland determination and evaluating whether
the hydrophytic vegetation criterion is satisfied. (Note; The
"National List of Plant Species that Occur in Wetlands" uses a
plus (+) sign or a minus (-) sign to signify a higher or lower
portion of a particular wetland indicator frequency for the three
facultative-type indicators; for purposes of identifying
hydrophytic vegetation according to this manual, however, FACW+,
FACW-, FAC+, and FAC- are included as FACW and FAC, respectively,
in the hydrophytic vegetation criterion.)
Dominant Vegetation
Dominance as used in this manual refers strictly to the spatial
extent of a species that is directly discernable or measurable in
the field. When identifying dominant vegetation within a given
plant community, one should consider dominance within each valid
stratum. All dominants are treated equally in characterizing the
plant community to determine whether the hydrophytic vegetation
criterion is met. For each stratum (e.g., tree, shrub, and herb)
in the plant community, dominant species are determined by
ranking all species.in descending order of dominance (e.g., areal
cover or basal area) and cumulatively totaling species until they
exceed 50 percent of the total dominance measure (e.g., total
areal coverage or total basal area for a sample plot). All
species that contribute to exceeding the 50 percent level are
considered dominant species, along with any additional species
comprising 20 percent or more of the total dominance measure for
the stratum.
Vegetative strata for which dominants should be determined may
include: (1) tree (>5.0 inches diameter at breast height (dbh)
and 20 feet or taller); (2) sapling (0.4 to <5.0 inches dbh and
20 feet or taller); (3) shrub (usually 3 to 20 feet tall
including multi-stemmed, bushy shrubs and small trees below 20
feet tall); (4) woody vine; and (5) herb (herbaceous plants
including graminoids, forbs, ferns, fern allies, herbaceous
vines, and tree seedlings). Bryophytes (mosses, horned
liverworts, and true liverworts) should be sampled as a separate
%
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stratum in certain wetlands, including shrub bogs, moss-lichen
wetlands, and wooded swamps where bryophytes are abundant and
represent an important component of the community, in most other
wetlands, bryophytes should be included within the herb stratum
due to their scarcity. In order to be counted as a valid
stratum, a stratum must have at least 5 percent areal cover for
the area under evaluation, e.g., 5-foot radius plot for herbs and
30-foot radius plot for woody plants. This minimum does not
apply to woody vines; use professional judgment to determine
whether they are abundant enough to count as a stratum. Always
document the omission of any such stratum from the final
evaluation regarding the hydrophytic vegetation criterion.
There are many ways to estimate or quantify dominance measures.
Dominant species for each stratum can be determined by estimating
one or more of the following, as appropriate: (1) relative basal
area (trees); (2) areal cover (all strata); or (3) stem density
(all strata). Direct measurement of tree diameters at breast
height provides data for calculating basal area for determining
dominant tree species. Alternatively, one may wish to perform a
frequency analysis of all species within a given plant community.
These are accepted methods for evaluating plant communities. Part
III of this manual provides recommended approaches for sampling
or analyzing the plant community.
HYDRIC SOIL CRITERION
An area has hydric soil when it has either:
1. Soils listed by series in "Hydric Soils of the United
States" (1987 and amendments), or
2. Organic soils (Histosols, except Folists), or
3. Mineral soils classifying as Sulfaquents, Hydraquents,
or Histic subgroups of Aquic suborders, or
4. Other soils that meet the National Technical Committee
for Hydric Soils' criteria for hydric soil.
An area meets the hydric soil criterion when it has one or more
of the following:
1. Where soil survey maps are available, the subject area
is within:
a. a hydric soil map unit identified on the county
list of hydric soil map units that is verified by
landscape position and soil morphology against the
series description of the hydric soil, or
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b. a soil map unit with hydric soil inclusions
identified on the county list of hydric soil map
units, and the landscape position of the inclusion
and the soil morphology for the identified soil
series as a hydric soil inclusion are verified,
or, if no series is designated, then either:
1) the soil, classified to the series level, is on
the national list of hydric soils, or
2) the soil, classified according to "Soil
Taxonomy", is a Histosol (except Folists),
Sulfaquent, Hydraquent, or Histic Subgroup of
Aquic Suborders, or
3} regional indicators of significant soil
saturation are materially present; or
2. Where soil maps are not available, and the landscape
position is likely to contain hydric soil (e.g.,
floodplain, depression, or seepage slope), subject area
has either:
a. the soil, classified to the series level, is on the
national list of hydric soils, or
b. the soil, classified according to "Soil Taxonomy",
is a Histosol (except Folists), Sulfaquent,
Hydraquent, or Histic Subgroup of Aquic Suborders,
or
c. regional indicators of significant soil saturation
are materially present.
Hydric Soil Background
Wetlands typically possess hydric soils, but not all areas mapped
as a hydric soil series are wetlands (e.g., dry phases that were
never wetlands and drained phases that represent former
wetlands). Hydric soils are defined as soils that are saturated,
flooded, or ponded long enough during the growing season to
develop anaerobic conditions in the upper part (U.S.D.A. Soil
Conservation Service 1987). These soils usually support
hydrophytic vegetation under natural (unaltered) conditions.
National and State Hydric Soils Lists
The SCS in cooperation with the National Technical Committee for
Hydric Soils (NTCHS) has prepared a list of the Nation's hydric
soils (U.S.D.A. Soil Conservation Service 1987). State lists have
also been prepared for statewide use. The national and state
lists identify those soil series that typically meet the NTCHS
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hydric soil criteria according to available soil interpretation
records in SCS's soils database. These lists are periodically
updated, so make sure the list being used is the current one. The
list, while extensive, does not include all series that may have
hydric members; these soils may be determined as hydric when they
have evidence of wetland hydrology and hydrophytic vegetation.
The lists facilitate use of SCS county soil surveys for
identifying potential wetlands. One must be careful, however, in
using the soil survey, because a soil map unit of a nonhydric
soil may have inclusions of hydric soil that were not delineated
on the map or vice versa. Also, some map units (e.g., alluvial
land, swamp, tidal marsh, muck and peat) may be hydric soil
areas, but are not on the hydric soils lists because they were
not given a series name at the time of mapping. These soils meet
the NTCHS criteria for hydric soils.
County Hydric Soil Map Unit Lists
Because of the limitations of the national and state hydric soil
lists, the SCS prepared lists of hydric soil map units for each
county in the United States. These lists may be obtained from
local SCS district offices and are the preferred lists to be used
when using soil survey maps. The hydric soil map unit lists
identify all map units that are either named by a hydric soil or
that have a potential of having hydric soil inclusions. The
lists provide the map unit symbol, the name of the hydric soil
part or parts of the map unit, information on the hydric soil .
composition of the map unit, and probable landscape position of
hydric soils in the map unit delineation. The county lists also
include map units named by miscellaneous land types or higher
levels in "Soil Taxonomy" that meet NTCHS hydric soil criteria.
Soil Surveys
The SCS publishes so.il surveys for areas where soil mapping is
completed. Soil surveys that meet standards of the National
Cooperative Soil Survey (NCSS) are used to identify areas of
hydric soils. These soil surveys Bay be published (completed) or
unpublished (on file at local SCS field offices). Published soil
surveys of an area may be obtained from the local SCS field
office or the Agricultural Extension Service office. Unpublished
maps may be obtained from the local SCS district office.
The NCSS maps contain four kinds of map units: (1) consociations,
(2) complexes, (3) associations, and (4) undifferentiated groups.
(Note: Inclusions of unnamed soils may be contained within any
map unit; the inclusions are listed in the description of the
soil map unit in the soil survey report.) Consociations are soil
map units named for a single kind of soil (taxon) or
miscellaneous area. Seventy-five percent or more of the area is
composed of the taxon for which the map unit is named (and
similar taxa). When named by a hydric soil, the map unit is
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considered a hydric soil map unit for wetland determinations.
However, small areas within these nap units generally too small
to be mapped separately (some areas are identified by "wet spot"
symbols) may not be hydric and should be excluded in delineating
wetlands.
Complexes and associations are soil map units named by two or
more kinds of soils (taxa) or miscellaneous areas. If all taxa
for which these map units are named are hydric, the soil map unit
may be considered a hydric soil map unit for wetland
determinations. If only part of the map unit is made up of hydric
soils, only those portions of the map unit that are hydric are
considered in wetland determinations.
Undifferentiated groups are soil map units named by two or more
kinds of soils or miscellaneous areas. The soils in these map
units do not always occur together in the same map unit but are
included together because some common feature such as steepness
or flooding determines use and management. These map units are
distinguished from the others in that "and" is used as a
conjunction in the name, while dashes are used for complexes and
associations. If all components are hydric, the map unit may be
considered a hydric soil map unit. If one or more of the soils
for which the unit is named are nonhydric, each area must be
examined for the presence of hydric soils.
Use of County Hydric Soils Map Unit Lists and Soil Surveys
The county hydric soils map unit list and soil surveys should be
used to help determine if the hydric soil criterion is met in a
given area. When making a wetland determination, one should first
locate the area of concern on a soil survey map and identify the
soil map units for the area. The county list of hydric soil map
units should be consulted to determine whether the soil map units
are hydric or potentially hydric. If hydric soil map units or map
units with hydric soil inclusions are noted, then one should
examine the soil in the field and compare its morphology with the
corresponding hydric soil description in the soil survey report.
If the soil's characteristics match those described for hydric
soil, then the hydric soil criterion is met, unless the soil has
been effectively drained. If soils have been significantly
disturbed, either mechanically or hydrologically, refer to the
disturbed areas section on page 41. In the absence of site-
specific information, hydric soils also may be recognized by
certain soil properties caused by wetland hydrology conditions
that make soil meet the NTCHS criteria for hydric soils.
General Characteristics of Hydric Soils
Due to their wetness during the growing season, hydric soils
usually develop certain morphological properties that can be
readily observed in the field. Anaerobic soil conditions usually
*
25
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occur due to excessive wetness and they typically lower the soil
redox potential causing a chemical reduction of some soil
components, mainly iron oxides and manganese oxides. This
reduction affects solubility/ movement, and aggregation of these
oxides which is reflected in the soil color and other physical
characteristics that are usually indicative of hydric soils.
Soils are separated into two major types on the basis of material
composition: organic soil and mineral soil. In general, soils
with at least 16 inches of organic material in the upper part of
the soil profile and soils with organic material resting on
bedrock are considered organic soils (Histosols). Soils largely
composed of sand, silt, and/or clay are mineral soils. For
technical definitions, see "Soil Taxonomy", U.S.D.A. Soil Survey
Staff 1975.
Organic Soils
Accumulation of organic matter in roost organic soils results from
anaerobic soil conditions associated with long periods of
submergence or soil saturation during the growing season. These
saturated conditions impede aerobic decomposition (oxidation) of
the bulk organic materials such as leaves, stems, and roots, and
encourage their accumulation over time as peat or muck.
Consequently, most organic soils are characterized as very poorly
drained soils. Organic soils typically form in waterlogged
depressions, and peat or muck deposits may range from about 1.5
feet to more than 30 feet deep. Organic soils also develop in
low-lying areas along coastal waters where tidal flooding is
frequent.
Hydric organic soils are subdivided into three groups based on
the presence of identifiable plant material: (1) muck (Saprists)
in which two-thirds or more of the material is decomposed and
less than one-third of the plant fibers are identifiable; (2)
peat (Fibrists) in which less than one-third of the material is
decomposed and more than two-thirds of the plant fibers are still
identifiable; and (3) mucky peat or peaty muck (Hemists) in which
the ratio of decomposed to identifiable plant matter is more
nearly even (U.S.D.A. Soil Survey Staff 1975). A fourth group of.
organic soils (Folists) exists in tropical and boreal mountainous
areas where precipitation exceeds the evapotranspiration rate,
but these soils are never saturated for more than a few days
after heavy rains and thus do not develop under hydric
conditions. All organic soils, with the exception of the Folists,
are hydric soils.
Hydric organic soils can be easily recognized as black-colored
muck to dark brown-colored peat. Distinguishing mucks from peats
based on the relative degree of decomposition is fairly simple.
In mucks (Saprists), almost all of the plant remains have been
decomposed beyond recognition. When rubbed, mucks feel greasy and
*
26
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leave hands dirty. In contrast, the plant remains in peats
(Fibrists) show little decomposition and the original constituent
plants can be recognized fairly easily* When the organic natter
is rubbed between the fingers, most plants fibers will remain
identifiable, leaving hands relatively clean. Between the
extremes of mucks and peats, organic soils with partially
decomposed plant fibers (Hemists) can be recognized. In peaty
mucks up to two-thirds of the plant fibers can be destroyed by
rubbing the materials between the fingers, while in mucky peats
up to two-thirds of the plant remains are still recognizable
after rubbing.
Hydric Mineral Soils
When less organic material accumulates in soil, the soil is
classified as mineral soil. Some mineral soils may have thick
organic surface layers (histic epipedons) due to heavy seasonal
rainfall or a high water table, yet these soils are still
composed largely of mineral matter (Ponnamperuma 1972). Mineral
soils that are covered with moving (flooded) or standing (ponded)
water for significant periods or are saturated for extended
periods during the growing season meet the NTCHS criteria for
hydric soils and are classified as hydric mineral soils. Soil
saturation may result from low-lying topographic position,
groundwater seepage, or the presence of a slowly permeable layer
(e.g., clay, confining layer, confining bedrock, or hardpan).
The duration and depth of soil saturation are essential criteria
for identifying hydric soils and wetlands. Soil morphological
features are commonly used to indicate long-term soil moisture
regimes (Bouma 1983) . Table lists some of the more commonly
observed morphological properties associated with hydric mineral
soils having a Typic Subgroup and Aquic Suborder.
A thick dark surface, layer, grayish subsurface and subsoil
colors, the presence of orange or reddish brown (iron) and/or
dark reddish brown or black (manganese) mottles or concretions
near the surface, and the wet condition of the soil may help
identify the hydric character of many mineral soils. The grayish
subsurface and subsoil colors and thick, dark surface layers are
the best indicators of current wetness, since the yellow- or
orange-colored mottles are very insoluble and once formed may
remain indefinitely as relict mottles of former wetness (Diers
and Anderson 1984).
A histic epipedon (organic surface layer) is evidence of a soil
meeting the NTCHS criteria. It is an 8 to 16 inch organic layer
at or near the surface of a hydric mineral soil that is saturated
with water for 30 consecutive days or more in most years. It
contains a minimum of 20 percent organic matter when no clay is
present or a minimum of 30 percent organic matter when clay
content is 60 percent or greater. Soils with histic epipedons are
27
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inundated or saturated for sufficient periods to greatly retard
aerobic decomposition of organic matter, and are considered
hydric soils. In general, a histic epipedon is a thin surface
layer of peat or muck if the soil has not been plowed (U.S.D.A.
Soil Survey Staff -1975). Histic epipedons are typically
designated as 0-horizons (Oa, Oe, or Oi surface layers, and in
some cases the terms "mucky" or "peaty" are used as modifiers to
the mineral soil texture term, e.g., mucky loam.
Soil-related Evidence of Significant Saturation
Identification of some wetlands and delineation of the upper
boundary in many wetlands is not readily accomplished without a
detailed examination of the underlying soil. Colors in the soil
are strongly influenced by the frequency and duration of soil
saturation which causes reducing conditions. A gleyed layer and a
low chroma matrix with high chroma mottles, near the surface are
common indicators of hydric soils throughout the county. Other
soil markers of significant soil saturation vary regionally.
These signs include thick organic surface layers (> 8 inches),
gleying, and certain types of mottling. If significant drainage
or groundwater alteration has taken place, then it is necessary
to determine whether the area in question is effectively drained
and is now nonwetland or is only partly drained and remains
wetland despite some hydrologic modification. Guidance for
determining whether an area is effectively drained is presented
in the section on disturbed areas (p. 41).
Soils saturated for prolonged periods during the growing season
in most years are usually gleyed in the saturated zone. Gleyed
layers are predominantly gray in color and occasionally greenish
or bluish gray. In gleyed soils, the distinctive colors result
from a process known as gleization. Prolonged saturation of
mineral soil converts iron from its oxidized (ferric) form to its
reduced (ferrous) state. These reduced compounds may be
completely removed from the soil, resulting in gleying (Veneman,
et al. 1976). Mineral soils that are always saturated are
typically uniformly gleyed throughout the saturated area. Soils
gleyed to the surface layer are evidence of wetland hydrology and
anaerobic soil conditions. These soils often show evidence of
oxidizing conditions only along root channels. Some nonsaturated
soils have gray layers (E-horizons) immediately below the surface
layer that are gray for reasons other than saturation, such as
leaching due to organic acids (see Spodosols page 83).
Mineral soils that are alternately saturated and oxidized
(aerated) during the year are usually mottled in the part of the
soil that is seasonally wet. Mottles are spots or blotches of
different colors or shades of colors interspersed with the
dominant (matrix) color. The abundance, size, and color of the
mottles usually reflect the hydrology - the duration of the
saturation period, and indicate whether or not the soil is
28
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saturated for long periods. Mineral soils that are predominantly
grayish with common or many/ distinct or prominent brown or
yellow mottles are usually saturated for long periods during the
growing season and are hydric soils. Soils that are predominantly
brown or yellow with gray mottles are saturated for shorter
periods and may be hydric depending on the depth to the gray
mottles and the color of the overlying layer. Mineral soils that
are never saturated are usually bright-colored and are not
mottled; they are nonhydric soils (Tiner and Veneman 1987).
Realize, however, that in some hydric soils, mottles may not be
visible due to masking by organic matter (Parker, et al. 1984).
It is important to note that the gleization and mottle formation
processes are strongly influenced by the activity of certain soil
microorganisms. These microorganisms reduce iron when the soil
t -vironment is anaerobic, that is, when virtually no free oxygen
is present, and when the soil contains organic matter. If the
soil conditions are such that free oxygen is present, organic
matter is absent, or temperatures are too low (below 41 degrees
Fahrenheit) to sustain microbial activity, gleization will not
proceed and mottles will not form, even though the soil may be
saturated for prolonged periods of time (Diers and Anderson
1984).
Soil colors as discussed above often reveal much about a soil's
historical wetness over the long term. Scientists and others
examining the soil can determine the approximate soil color by
comparing the soil sample with a Munsell soil color chart. The
standardized Munsell soil colors are identified by three
components: hue, value, and chroma. The hue is related to one of
the main spectral colors: red, yellow, green, blue, or purple, or
various mixtures of these principal colors. The value refers to
the degree of lightness, while the chroma notation indicates the
color strength or purity. In the Munsell soil color book, each
individual hue has its own page (Figure ), each of which is
further subdivided into units for value (on the vertical axis)
and chroma (horizontal axis). Although theoretically each soil
color represents a unique combination of hues, values, and
chromas, the number of combinations common in the soil
environment usually is limited. Because of this situation and
the fact that accurate reproduction of each soil color is
expensive, the Munsell soil color book contains a limited number
of combinations of hues, values, and chromas. The color of the
soil matrix or a mottle is determined by comparing a soil sample
with the individual color chips in the soil color book. The
appropriate Munsell color name can be read from the facing page
in the "Munsell Soil Color Charts" (Kollmorgen Corporation 1975).
Chromas of 2 or less are considered low chromas and are often
diagnostic of hydric soils. Low chroma colors include black,
various shades of gray, and the darker shades of brown and red.
Gleying (bluish, greenish, or grayish colors) in or immediately
29
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below the A-horizon is an indication of a markedly reduced hydric
soil and an area that should meet wetland hydrology in the
absence of significant hydrologic modification. Gleying can occur
in both mottled and unmottled soils. Gleyed soil conditions can
be determined by using the gley page of the "Munsell Soil Color
Charts" (Kollmorgen Corporation 1975). NOTE: GLEYED CONDITIONS
NORMALLY EXTEND THROUGHOUT SATURATED SOILS. BEWARE OF SOILS WITH
GRAY SUBSOILS DUE TO PARENT MATERIALS, SOILS WITH GRAY E-HORIZONS
OR ALBIC HORIZONS DUE TO LEACHING AND NOT TO SATURATION; THESE
LATTER SOILS CAN OFTEN BE RECOGNIZED BY BRIGHT-COLORED LAYERS
BELOW THE E-HORIZON. SEE DISCUSSION ON DIFFICULT-TO-IDENTIFY
WETLANDS SECTION Page 31.
Mineral soils that are saturated for substantial periods of the
growing season, but are unsaturated for some time, commonly
develop mottles. Soils that have brightly colored mottles and a
low chroma matrix are indicative of a fluctuating water table.
The following color features in the horizon immediately below the
A-horizon (or E-horizon, albic horizon) provide evidence of soil
saturation sufficient to be hydric soils and should also meet the
wetland hydrology criterion:
(1) Matrix chroma of 2 or less in mottled soils, or
(2) Matrix chroma of 1 or less in unmottled soils.
NOTE: MOLLISOLS HAVE VALUE REQUIREMENTS OF 4 OR MORE AS '
WELL AS CHROMA REQUIREMENTS FOR AQUIC SUBORDERS; SEE
DIFFICULT-TO-IDENTIFY HYDRIC SOILS FOR OTHER EXCEPTIONS.
The chroma requirements above are for soils in a moistened
condition. Colors noted for dry (unmoistened) soils should be
clearly stated as such. The colors of the topsoil (A-horizon) are
often not indicative of the hydrologic situation because
cultivation and soil enrichment affect the original soil color.
Hence, the soil colors below the A-horizon (and E-horizon, if
present) usually must be examined.
NOTE: BEWARE OF HYDRIC SOILS THAT HAVE COLORS OTHER THAN THOSE
DESCRIBED ABOVE; SEE DIFFICULT-TO-IDENTIFY WETLANDS BELOW.
During the oxidation-reduction process, the iron and manganese in
solution in saturated soils are sometimes precipitated as oxides
into concretions or soft masses upon exposure to air as the soil
dries. Concretions are local concentrations of chemical
compounds (e.g., iron oxide) in the form of a grain or nodule of
varying size, shape, hardness, and color (Buckman and Brady
1969). Manganese concretions are usually black or dark brown,
while iron concretions are usually yellow, orange or reddish
brown. In wetlands, these concretions are also usually
accompanied by soil colors as described above.
i
30
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DIFPICULT-TO-IDENTIFY WETLANDS
All wetlands have wetland hydrology, hydric soil, and plants
adapted to those conditions. However, there are exceptions where
evidence of all three mandatory criteria is not readily
observable, especially in the drier season of the year or during
droughts. A procedure for identifying these difficult-to-
identify wetlands is in Appendix 7. Before using the difficult-
to-identify procedures, the assumption that an area may be a
difficult-to-identify wetland must be based on strong well
documented evidence, such as: the area is a wetland type that is
listed in this manual as a difficult-to-identify wetland, the
area is in a landscape position that is highly likely to support
wetlands (e.g., significant depression or drainageway, or
adjacency or proximity to a verified wetland or other waterbody),
the area has vegetation that is Jcnown to be found in wetlands in
the local area, or the area is underlain by a soil that is known
to support wetlands in the local area. Wetland types that are
difficult to identify are listed below and in Appendix 5. In
some of the below-listed wetlands, such as playas, prairie
potholes, vernal pools, and pocosins it may be difficult to
identify more than one of the criteria during dry seasons of the
year or droughts even though such wetlands vould meet the
criteria if visited at the optimal time of year for their
delineation. Difficult-to-identify wetlands include the
following categories:
Forested Wetlands
Some (but not all) forested wetlands may be diff icult-to-
identify. They are found in many parts of the country and meet
the wetland hydrology criterion by inundation and/or saturation
at the surface for more than 14 consecutive days during the
growing season. They may be difficult to identify because of
seasonal fluctuations in the water table or drought (e.g., red
maple swamps in New England), vegetation communities that have an
atypical distribution of plants (i.e., comprised of plants that
also occur in uplands (e.g., hemlock swamps), or soils that are
not readily identifiable as hydric (e.g., red parent material
soils. See Appendix 6). Forested wetlands typically perform
important aquatic functions (e.g., water quality maintenance,
stream discharge regulation, and groundwater recharge).
Streamside/Riparian Wetlands
Streamside and riparian areas may support wetlands that are
diff icult-to-identify. The rise and fall of stream flow may make
hydrology determinations difficult during dry seasons or drought.
However, stream gage data may be available to document normal
hydrologic conditions. Recent deposits of sediment in river
channels or on floodplains may make soils difficult to identify
because soils may not have had time to develop typical indicators
^
31
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of saturation. Streamside and riparian wetlands typically
perform important aquatic functions such as water quality
maintenance by filtration of floodwaters and upland runoff,
streamflow regulation by storing and slowly releasing floodwaters
and runoff, and providing aquatic habitats for fish and wildlife.
Wet Meadows/Prairie Wetlands
Some wet meadow and prairie wetlands are difficult-to-identify.
These wetlands may occur near waterways, in depressions or in
outwashes in drainageways. They may not exhibit wetland
hydrology during dry seasons or drought. These wetlands may have
difficult-to-identify vegetation due to the invasion during dry
periods by plants usually found in uplands. These wetlands may
perform aquatic functions such as water quality maintenance and
groundwater recharge.
Difficult-to-identify wetlands also include the following
specific types:
Pocosins
The pocosin wetlands of the Southeast contain broadleaved
evergreen shrub bogs. Such bogs typically occur in areas
characterized by highly organic soils and long hydroperiods
during which inundation may but does not always occur. The
largest areas of pocosin wetlands occur in the outer Coastal
Plain of North Carolina. Although early settlers used the term
to depict a variety of swamp vegetation types, pocosin wetlands
usually are described as marshy or boggy shrub areas or flatwoods
with poor drainage where peaty soils typically support scattered
pines and a dense growty of shrubs, mostly evergreen (Sharitz and
Gibbons 1982). Hydrology of pocosins may not be readily apparent
due to the thick underlying peaty soils that may dry out rapidly
after the early part of the growing season due to
evapotranspiration. Located on the Coastal Plain, pocosins
perform important aquatic functions such as storing rainwater and
regulating its discharge into nearby estuaries where aquatic life
is affected by fluctuations in streamflow and salinity. Pocosins
also function to stabilize nutrients, reducing the potential for
nutrient overloading in nearby estuaries.
Playas
Playas occur in many arid and semiarid regions of the world.
Although occurring throughout much of the western United States,
they are concentrated in the southern Great Plains as either
ephemeral or permanent lakes or wetlands. The topography of most
playa regions is flat to gently rolling and generally devoid of
drainage. Playa basins collect water primarily in two peak
periods — May and September — as a result of regional
32
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convectional storms. Wetland hydrology is best characterized by
examining hydrological indicators over a multi-year period.
Playa basins may have a dense cover of annual or perennial
vegetation or may be barren, depending on the timing and other
factors such as precipitation and irrigational runoff. As with
potholes, the process of annual drying in playas enables the
invasion of FAC, FACU, and UPL plants during dry periods which
may persist into other seasons. Playas typically are important
waterfowl habitat. Additional information to assist in p.laya
wetland identification is in Appendix 5.
Prairie Potholes
Prairie potholes are glacially-formed depressional wetlands
located in the north central United States and southern Canada.
Many prairie potholes are seasonally dry but fill with snowmelt
and rain early in the growing season. This is because average
precipitation is far too sparse to meet the demands of
evaporation and as a result, some potholes are dry for a
significant portion of the year. The process of annual drying in
potholes enables the invasion of FAC, FACU, or UPL plant species
during dry periods which may persist into wet seasons.
Nevertheless, a variety of vegetation characteristic of a
freshwater marsh can exist in a prairie pothole with submergent
and floating plants in deeper water, bulrushes and cattails
closer to shore, and sedges located toward the upland. The
drastically fluctuating climate and alteration for farming have
resulted in highly disturbed conditions that make wetland
identification difficult. Potholes are typically known for
supporting an abundance of resident and migratory waterfowl.
Additional information to assist in prairie pothole wetland
identification is in Appendix 5.
Vernal Pools
Vernal pools are natural wetlands are depressional wetlands that
are covered by shallow water for variable periods from winter to
spring, but may be completely dry at the surface for most of the
summer and fall. They hold water long enough to allow some
aquatic organisms (e.g., salamanders and frogs) to grow and
reproduce (complete their life cycles), but not long enough to
permit the development of a typical pond or marsh ecosystem.
Since vernal pools vary considerably in depth and duration of
both from year to year, within a year, or between different
pools, plant composition is quite dynamic. Depending on the
seasonal phase of the pool, plants can range from OBL aquatic
plants to FAC and FACU species. Additional information to assist
in vernal pool wetland identification is in Appendix 5.
33
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PART III.
STANDARD METHODS FOR IDENTIFICATION AND DELINEATION OF WETLANDS
Four basic approaches for identifying and delineating wetlands
have been developed to cover situations ranging from desk-top or
office determinations to highly complex field determinations for
regulatory purposes. These methods are the recommended approaches
that have been successfully used to delineate wetlands by the
four Federal agencies. If situations require different
approaches, the reasons for departing from recommended approaches
should be documented. Remember, however, that any method for
making a wetland determination must consider the three technical
criteria (i.e., hydrophytic vegetation, hydric soils, and wetland
hydrology) listed in Part II of this manual. These criteria roust
be met in order to identify a wetland. Moreover, procedures for
determining the wetland boundary must be consistent with those
used in this manual. In applying all methods, relevant available
information on wetlands in the area of concern should be
collected and reviewed. Table lists primary data sources.
*
Selection of a Method
The wetland delineation methods presented in this manual can be
grouped into two general types: (1) offsite preliminary
procedures and (2) onsite procedures. The offsite procedures are
designed for use in the office for preliminary wetland
determinations, while onsite procedures are developed for use in
the field for definitive wetland determinations. When an onsite
inspection is unnecessary or cannot be undertaken for various
reasons, available information can be reviewed in the office to
make a preliminary wetland determination. If available
information is insufficient to make a preliminary wetland
determination or if a definitive wetland determination or wetland
boundary must be established, (e.g., for determining whether or
not there is jurisdiction or the boundaries of jurisdiction under
a Federal wetland regulatory program), an onsite inspection
should be conducted. For determining whether or not an area is
subject to Clean Water Act jurisdiction, an onsite inspection is
usually necessary. Depending on the field information needed or
the complexity of the area, one of three basic onsite methods nay
be employed: (1) routine, (2) intermediate-level, or (3)
comprehensive. Table presents some examples of when to use
each method.
The routine method is designed for areas equal to or less than
five acres in size or larger areas with homogeneous vegetation.
For areas greater than five acres in size or other areas of any
size that are highly diverse in vegetation, the
intermediate-level method or the comprehensive method should be
applied, as necessary. The comprehensive method is applied to
situations requiring detailed documentation of vegetation, soils,
-------
and hydrology. Assessments of significantly disturbed sites will
often require intermediate-level or comprehensive determinations
as well as some special procedures. In other cases where natural
conditions make wetland identification difficult, special
procedures for difficult-to-identify wetland determinations have
been developed. Wetland delineators should become well
acquainted with these types of situations (e.g., disturbed and
difficult-to-identify wetlands) and the appropriate procedures.
In making wetland determinations, one should select the
appropriate method for each individual unit within the area of
concern and not necessarily employ one method for the entire
site. Thus, a combination of determination methods may be used
for a given site.
Regardless of the method used, the desired outcome or final
product is a wetland/nonvetland determination. Depending on one's
expertise, available information, and individual or agency
preference, there are two basic approaches to delineating wetland
boundaries. The first approach involves characterizing plant
communities in the area, identifying plant communities meeting
the hydrophytic vegetation criterion, examining the soils in
these areas to confirm that the hydric soil criterion is met, and
finally looking for evidence of wetland hydrology to verify this
criterion. This approach has been widely used by the CE and EPA
and to a large extent by the FWS. A second approach involves
first delineating the approximate boundary of potential hydric
soils, and then verifying the presence of likely hydrophytic
vegetation and looking for signs of wetland hydrology. This type
of approach has been employed by the SCS and to a limited extent
by the FWS. Since these approaches yield the same result, this
manual incorporates both approaches into most of the methods
presented.
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Table 1.
Ita Name
Primary sources of information
making a wetland determination.
Topographic Maps (mostly 1:24,000;
Survey (USGS)
1:63,350 for Alaska)
1-800-USA-MAPS)
National Wetlands Inventory Maps
Wildlife Service
(mostly 1:24,000; 1:63,350
1-800-USA-MAPS)
for Alaska)
County Soil Survey Reports
Conservation Service
Offices
reports—local district
National Hydric Soils List
State Hydric Soils List
County Hydric Soil Map Unit List
National Insurance Agency
Management
Flood Maps Agency
Local Wetland Maps
agencies
Land Use and Land Cover Maps
(1-800-USA-MAPS)
Aerial Photographs
sources—USGS, other Federal and
private sources
ASCS Compliance Slides
Agricultural Stabilization and Conservation
Satellite Imagery
National List of Plant Species
that may be helpful in
Source
U.S. Geological
(Call
U.S. Fish and
(FWS) (Call
U.S.D.A. Soil
(SCS) District
(Unpublished
offices)
SCS National Office
SCS State Offices
SCS District Offices
Federal Emergency
State and local
USGS
Various
State agencies, and
U.S.D.A.
Service
EOSAT Corporation,
SPOT Corporation,
and others
Government Printing
36
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Office
That Occur in Wetlands
Documents
(Stock No. 024-010-00682-0)
Regional Lists of Plants that
Information Occur in Wetlands
22161
National Wetland Plant Database
Stream Gauge Data
and USGS
Soil Drainage Guides
Data Name
Environmental Impact Statements
State agencies
and Assessments
Published Reports
Local Expertise
consultants, and others
Site-specific Plans and
Engineering Designs
Superintendent of
Washington, DC 20402
Rational Technical
Service
5285 Port Royal Head
Springfield, VA
(703) 487-4650
FWS
CE District Offices
SCS District Offices
Source
Various Federal and
Federal and States
agencies,
universities, and
others
Universities,
Private developers
37
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Description of Methods
Offsite Preliminary Determinations
When an onsite inspection is not necessary because information on
hydrology, hydric soils, and hydrophytic vegetation is known or an
inspection is not possible due to time constraints or other reasons,
a preliminary wetland determination can be made in the office. This
approach provides an approximation of the presence of wetland and
its boundaries based on available information. The accuracy of the
determination depends on the quality of the information used and on
one's ability and experience in an area to interpret these data.
Where reliable, site-specific data have been previously collected,
the wetland determination can be reasonably accurate. Where these
data do not exist, more generalized information may be used to make
a preliminary wetland determination. In either case, however, if a
more accurate delineation is required, then onsite procedures must
be employed. For the purposes of determining whether an area is
subject to Federal jurisdiction under the Clean Water Act or other
Federal wetland regulatory program, onsite determinations are
usually necessary. Regardless of the method used, documentation of
all three criteria is mandatory.
Onsite Determinations
When an onsite inspection is necessary, always be sure to review
pertinent background information (e.g., NWI maps, soil surveys, and
site plans) before going to the subject site. This information will
be helpful in determining what type of field method should be
employed. Also, read the sections of this manual that discuss
disturbed (page 41) and difficult-to-identify (page 31) wetlands
before conducting field work. These situations pose significant
problems for the inexperienced wetland delineator, so learn the
procedures for evaluating these sites. Recommended equipment and
materials for conducting onsite determinations are listed in Table
•
Figures 1, 2, and 3 show the decision process for making onsite
wetland determinations by the various approaches presented in the
manual.
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Table 2. Recommended equipment and materials for onsite
determinations.
Equipment
Materials
Soil auger, probe, or spade
Sighting compass
Pen or pencil
Penknife
Hand lens
Vegetation sampling frame*
Camera/Film
wetland Binoculars
Tape measure
Prism or angle gauge
Diameter tape*
Vasculum (for plant collect.)
Names
Calculator*
Dissecting kit
Data sheets and clipboard
Field notebook
Base (topographic) map
Aerial photograph
Nation Wetlands Inventory map
Soil survey or other soil map
Appropriate Federal interagency
plants list
County hydric soil map unit list
Munsell soil color book
Plant identification field
guides/manuals
National List of Scientific Plant
Flagging tape/wire flags-wooden stakes
Plastic bag (for collecting plants and
soil samples as needed)
*Needed for comprehensive determination
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For every upcoming field inspection, the following pre-inspection
steps should be undertaken:
Step 1. Locate the project area on a nap (e.g., U.S. Geological
Survey topographic map or SCS soil survey map) or on an aerial
photograph and determine the limits of the area of concern. Proceed
to Step 2.
Step 2. Estimate the size of the subject area. Proceed to Step
3.
Step 3. Review existing background information and determine,
to the extent possible, the site's georaorphological setting (e.g.,
floodplain, isolated depression, or ridge and swale complex), its
habitat or vegetative complexity (i.e., the range of habitat or
vegetation types), and its soils. (Note: Depending on available
information, it may not be possible to determine the habitat
complexity without going on the site; if necessary, do a field
reconnaissance.) Proceed to Step 4.
Step 4. Determine whether a disturbed condition exists. Examine
available information and determine whether there is evidence of
sufficient natural or human-induced alteration to significantly
modify all or a portion of the area's vegetation, soils, and/or
hydrology. If such disturbance is noted, identify the limits of
affected areas for they should be evaluated separately for wetland
determination purposes (usually after evaluating undisturbed areas).
The presence of disturbed areas within the subject area should be
considered when selecting an onsite determination method. (Note; It
may be possible that at any time during this determination, one or
more of the three characteristics may be found to be significantly
altered. If this happens, follow the disturbed area wetland
determination procedures, as necessary, noted on p. 41). Proceed to
Step 5.
Step 5. Determine the field determination method to be used.
Considering the size and complexity of the area and the need for
quantification, determine whether a routine, intermediate-level, or
comprehensive field determination method should be used. When the
area is equal to or less than five acres in size or is larger and
appears to be relatively homogeneous with respect to vegetation,.
soils, and/or hydrology, use the routine method (see below). When
the area is greater than five acres in size, or is smaller but
appears to be highly diverse with respect to vegetation, use the
intermediate-level method (Appendix 3). When detailed quantification
of plant communities and more extensive documentation of other
factors (soils and hydrology) are required, use the comprehensive
method regardless of the wetland's size (Appendix 4). Significantly
disturbed sites (e.g., sites that have been filled, hydrologically
modified, cleared of vegetation, or had their soils altered) will
generally require intermediate-level or comprehensive methods. In
*
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these disturbed areas, it usually will be necessary to follow a set
of subroutines to determine whether the altered characteristic met
the applicable criterion prior to its modification; in the case of
altered wetland hydrology, it may be necessary to determine whether
the area is effectively drained. Because a large area may include a
diversity of smaller areas ranging from simple wetlands to
vegetatively complex areas, one may use a combination of the onsite
determination methods, as appropriate.
Disturbed Area Wetland Determinations
In the course of field investigations, one often encounters
significantly disturbed or altered areas. Disturbed areas include
situations where field indicators of one or more of the three
wetland identification criteria are obliterated or not present due
to recent change. The following sections discuss these situations
and present procedures for distinguishing wetlands from nonwetlands.
Disturbed areas have been altered either recently or in the past in
some way that makes wetland identification more difficult than it
would be in the absence of such changes. Disturbed areas include
both wetlands and nonwetlands that have been modified to varying
degrees by human activities (e.g., filling, excavation, clearing,
damming, and building construction) or by natural events (e.g.,
avalanches, mudslides, fire, volcanic deposition, and beaver dams).
Disturbed wetlands include areas subjected to deposition of fill or
dredged material, removal or other alteration of vegetation,
conversion to agricultural land and silviculture plantations, and
construction of levees, channelization and drainage systems, and/or i
dams (e.g., reservoirs and beaver dams) that significantly modify an
area's hydrology. In considering the effects of natural events
(e.g., a wetland buried by a mudslide), the relative permanence of
the change and whether the area is still functioning as a wetland
must be considered.. If natural events have relatively permanently
disturbed an area to the extent that wetland hydrology is no longer
present, and therefore hydric soils and hydrophytic vegetation, even
if still present, would not be expected to persist at the site, the
area is no longer a wetland. Detailed investigations of the prior
condition of such areas is generally inappropriate.
In cases where recent human activities have caused these changes, it
may be necessary to determine the date of the alteration or
conversion for legal purposes. If an illegal disturbance is
suspected, and the pre-disturbance condition must be determined for
the purposes of wetland regulatory program enforcement purposes,
then a detailed investigation of the prior and current conditions of
the disturbed area (i.e., whether the area was and is wetland or
non-wetland) is appropriate. However, if an area has been disturbed
by legal human activities that have effected the relatively
permanent removal of wetland hydrology, hydric soil, or hydrophytic
vegetation, then the area is non-wetland, and a detailed
»
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investigation of the prior condition of such areas is generally
inappropriate. In addition, determination of regulatory
jurisdiction for such areas is subject to agency interpretation.
For example, Federal wetland regulatory policy under the Clean Water
Act, and agricultural program policy under the Food Security Act of
1985, as amended, interprets the relative permanence of disturbance
to vegetation caused by agricultural cropping. Be sure to consult
appropriate agency in making Federal wetland jurisdictional
determinations in such areas.
In disturbed wetlands, field indicators for one or more of the three
technical criteria for wetland identification are usually absent.
Where it is necessary to determine whether the "missing"
indicator(s) (especially wetland hydrology) existed prior to
alteration, one should review aerial photographs, existing maps, and
other available information about the site. This determination may
involve evaluating a nearby reference site (similar to the original
character of the one altered) for indicator(s) of the "altered"
characteristic.
When a significantly disturbed condition is detected during an
onsite determination, and the prior condition of the area must be
determined or it is suspected that the area may still be a wetland,
the following steps should be taken to determine if the "missing"
indicator(s) was present before alteration and whether the criterion
in question was originally met. Be sure to record findings on the
appropriate data form. After completing the necessary steps in
Appendix 4, return to the applicable step of the onsite
determination method being used and continue evaluating the site's
characteristics.
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APPENDIX 1. Off site Preliminary Determination Method
The following steps are recommended for conducting an offsite
wetland determination:
Step 1. Locate the area of interest on a U.S. Geological Survey
topographic map and delineate the approximate subject area boundary
on the map. Note whether marsh or swamp symbols or lakes, ponds,
rivers, and other waterbodies are present within the area. If they
are, then there is a good likelihood that wetland is present.
Proceed to Step 2.
Step 2. Review appropriate National Wetlands Inventory (NWI)
maps, State wetland maps, or local wetland maps, where available. If
these maps designate wetlands in the subject area, there is a high
probability that wetlands are present unless there is evidence on
hand that the wetlands have been effectively drained, filled,
excavated, impounded, or otherwise significantly altered since the
effective date of the maps. Proceed to Step 3.
Step 3. Review SCS soil survey maps where available. In the
area of interest, are there any map units listed on the county list
of hydric soil map units or are there any soil map units with
significant hydric soil inclusions? If YES, then at least a portion
of the project area may be wetland. If this area is also shown as a
wetland on NWI or other wetland maps, then there is a very high
probability that the area is wetland unless it has been recently
altered (check recent aerial photos, Step 4). Areas without hydric
soils or hydric soil inclusions should in most cases be eliminated
from further review, but aerial photos still should be examined for
small wetlands to be more certain. This is especially true if
wetlands have been designated on the National Wetlands Inventory or
other wetland maps. Proceed to Step 4.
Step 4. Review recent aerial photos of the project area. Before
reviewing aerial photos, evaluate climatological data to determine
whether the photo year had normal or abnormal (high or low)
precipitation two to three months, for example, prior to the date of
the photo. This will help provide a useful perspective or
frame-of-reference for doing photo interpretation. In some cases,
aerial photos covering a multi-year period (e.g., 5-7 years) should
be reviewed, especially where recent climatic conditions have been
abnormal.
During photo interpretation, look for one or more signs of wetlands.
For example:
1) hydrophytic vegetation;
2) surface water;
3) saturated soils;
4) flooded or drowned out crops;
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5) stressed crops due to wetness;
6) greener crops in dry /ears;
7) differences in vegetation patterns due to different
planting dates.
If signs of wetland are observed, proceed to Step 5 when
site-specific data are available; if site-specific data are not
available, proceed to Step 6.
(CAUTION: Accurate photo interpretation of certain wetland types
requires considerable expertise. Evergreen forested wetlands,
seasonally saturated wetlands, and temporarily flooded wetlands, in
general, nay present considerable difficulty. If not proficient in
wetland photo interpretation, then one can rely more on the findings
of other sources, such as NWI naps and soil surveys, or seek help in
photo interpretation.)
Step 5. Review available site-specific information. In some
cases, information on vegetation, soils, and hydrology for the
project area has been collected during previous visits to the area
by agency personnel, environmental consultants or others. Moreover,
individuals or experts having firsthand knowledge of the project
site should be contacted for information whenever possible. Be sure,
however, to know the reliability of these sources. After reviewing
this information, proceed to Step 6.
Step 6. Determine whether wetlands exist in the subject area.
Based on a review of existing information, a preliminary
determination can be made that the area is likely to be a wetland
if:
1) Wetlands are shown on NWI or other wetland maps, and hydric
soil map unit or a soil map unit with hydric soil inclusions is
shown on the soil-survey; or
2) Hydric soil map unit or soil map unit with hydric soil
inclusions is shown on the soil survey (Note; In the latter case,
only the hydric inclusion is being evaluated as wetland.), and
A) site-specific information, if available, confirms
hydrophytic vegetation, hydric soils, and wetland
hydrology, or
B) wetlands are shown in aerial photos.
If, after examining the available reference material one is
still unsure whether the area is likely to be wetland, then a field
inspection should be conducted, whenever possible. Alternatively,
more detailed information on the site's characteristics may be
sought, to help make the preliminary determination.
*
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The validity of offsite preliminary determinations are dependent on
the availability of information for making a wetland determination,
the quality of this information, and one's ability and experience to
interpret these data. In most cases, therefore, the offsite
procedure yields a preliminary determination. For more accurate
results, one must conduct an onsite inspection.
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APPENDIX 2. Routine Onsite Determination Method
For most cases, wetland determinations can be made in the field
without rigorous sampling of vegetation and soils. Two approaches
for routine determinations are presented: (1) hydric soil assessment
procedure, and (2) plant community assessment procedure. In the
former approach, areas that meet or may meet the hydric soil
criterion are first identified and then dominant vegetation is
visually estimated to determine if hydrophytic vegetation is
obvious. If so, the area is designated as wetland. If not, then the
site must undergo a more rigorous evaluation following one of the
other onsite determination methods presented in the manual. The
second routine approach requires initial identification of
representative plant community types in the subject area and then
characterization of vegetation, soils, and hydrology for each type.
After identifying wetland and nonwetland communities, the wetland
boundary is delineated. All pertinent observations on the three
mandatory wetland criteria should be recorded on an appropriate data
sheet; this should be done for all inspections to determine
regulatory Jurisdiction.
Hydric Soil Assessment Procedure
Step 1. Identify the approximate limits of areas that may meet
the hydric soil criterion within the area of concern and sketch
limits on an aerial photograph. To help identify these limits use
sources of information such as Agricultural Stabilization and
Conservation slides, soil surveys, NWI maps, and other maps and
photographs. (Note; This step is more convenient to perform offsite,
but may be done onsite.) Proceed to Step 2.
Step 2. Scan the areas that may meet the hydric soil criterion
and determine if disturbed conditions exist. Are any significantly
disturbed areas present? If YES, identify their limits for they
should be evaluated separately for wetland determination purposes
(usually after evaluating undisturbed areas). Refer to the section
on disturbed areas (p. 41), if necessary, to evaluate the altered
characteristic(s) (vegetation, soils, or hydrology). If
appropriate, determine whether wetland regulatory policy exempts the
area from Federal regulatory jurisdiction (e.g., regulatory policy
on wetlands converted to cropland. See Disturbed Areas discussion,
p.85); then return to this method and continue evaluating
characteristics not altered. (Note; Prior experience with disturbed
sites may allow one to easily evaluate an altered characteristic,
such as when vegetation is not present in a farmed wetland due to
cultivation-.)- Keep in mind that if at any time during this
determination, one or more of these three characteristics are found
to have been significantly altered, the disturbed area determination
procedures should be followed. If the area is not significantly
disturbed, proceed to Step 3.
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Step 3. Scan the areas that ma/ meet the hydric soil criterion
and determine if obvious signs of wetland hydrology or hydric soil
are present. The wetland hydrology criterion is net for any area or
portion thereof where it is obvious or known that the area is
frequently inundated or saturated to the surface for a sufficient
duration during the growing season in most years. If the above
condition exists, the hydric soil criterion is presumed to be met
for the subject area and the area is considered wetland. If
necessary, confirm the presence of readily identified hydric soil by
examining the soil for appropriate properties. If the area's
hydrology has not be significantly disturbed and the soil is organic
(Histosols, except Folists) or is mineral classified as Sulfaquents,
Hydraquents, or Histic subgroups of Aquic Suborders, the area is
also considered wetland. (Note; The hydrophytic vegetation criterion
is presumed to be met under these conditions, i.e., undrained hydric
soil, so vegetation does not need to be examined. Moreover,
hydrophytic vegetation should be obvious in these situations;
however you may need to record dominant species for future
references) Areas lacking obvious indicators of wetland hydrology or
readily obvious hydric soils must be further examined, so proceed to
Step 4.
Step 4. Refine the boundary of areas that may meet the hydric
soil criterion. Verify the presence of hydric soil within the
appropriate map units by digging a number of holes at least 18
inches deep along the boundary (interface) between hydric soil units
and nonhydric soil units. Compare soil samples with descriptions in
the soil survey report to see if they are properly mapped. In this
way, the boundary of areas meeting the hydric soil criterion is
further refined by field observations. In map units where only part
of the unit is hydric (e.g., complexes, associations, and
inclusions), locate hydric soil areas on the ground by considering
landscape position and evaluating soil characteristics for hydric
soil properties. (Note; Some hydric soils, especially organic soils,
have not been given a series name and are referred to by common
names, such as peat, muck, swamp, marsh, vet alluvial land, tidal
marsh, Sulfaquents, and Sulfihemists. These areas are also
considered hydric soil nap units. Certain hydric soils are mapped
with nonhydric soils as an association or complex, while other
hydric soils occur as inclusions in nonhydric map units. Only the
hydric soil portion of these map units should be evaluated for the
hydrophytic vegetation criteria in Step 7.) If the area meets the
hydric soil criterion, proceed to Step 5.
Step 5. Consider the following:
1) Is the area presently lacking hydrophytic vegetation or
hydrologic indicators due to annual, seasonal or long-term
fluctuations in precipitation, surface water, or ground-water
levels?
2) Are hydrophytic vegetation indicators lacking due to
47
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seasonal fluctuation in temperature (e.g., seasonality of plant
growth)?
If the answer to either of these questions is YES or uncertain,
proceed to the section on difficult-to-identify wetland discussion
(p.31). If the answer to both questions is NO, normal conditions are
assumed to be present, so proceed to Step 6. (Note; In some cases,
normal climatic conditions, such as snow cover or frozen soils, may
prevent an accurate assessment of the wetland criteria; one must use
best professional judgement to determine if delaying the wetland
delineation is appropriate.)
Step 6. Select representative observation area(s). Identify one
or more observation areas that represent the area(s) meeting the
hydric soil criterion. A representative observation area is one in
which the apparent characteristics (determined visually) best
represent characteristics of the entire community. Mark the
approximate location of the observation area(s) on the aerial photo.
Proceed to Step 7.
Step 7. Characterize the plant community within the area(s)
meeting the hydric soil criterion. Visually estimate the percent
areal cover of dominant species for the entire plant community. If
dominant species are not obvious, use one of the other onsite
methods. Proceed to Step 8 or to another method, as appropriate.
Step 8. Record the indicator status of dominant species within
each area meeting the hydric soil criterion. Indicator status is
obtained from the interagency Federal list of plants occurring in
wetlands for the appropriate geographic region. Record information
on an appropriate data form. Proceed to Step 9.
Step 9. Determine whether wetland is present or additional
analysis is required. If the estimated percent areal cover of OBL
and FACW species (dominants) exceeds that of FACU and UPL species
(dominants), the"area is considered wetland and the
wetland-nonwetland boundary is the line delineated by the limits of
conditions that verify the wetland hydrology criterion (see p. 10).
If not, then the point intercept or other sampling procedures should
be performed to do a more rigorous analysis of site characteristics.
Plant Community Assessment Procedure
Step 1. Scan the entire project area, if possible, or walk, if
necessary, and identify plant community types present. In
identifying communities, pay particular attention to changes in
elevation throughout the site. (CAUTION: In highly variable sites,
such as ridge and swale complexes, be sure to stratify properly,
i.e., divide the site into homogeneous landforms to evaluate each
landform separately.) If possible, sketch the approximate location
of each plant community on a base map, an aerial photograph of the
48
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project area, or a county soil survey nap and label each community
with an appropriate name. (Note: For large homogeneous wetlands,
especially marshes dominated by herbaceous plants and shrub bogs
dominated by low-growing shrubs, it is usually not necessary to wa
the entire project area. In these cases, one can often see for long
distances and many have organic mucky soils that can be extremely
difficult to walk on. Forested areas, however, will usually require
a walk through the entire project area.)
In examining the project area, are any significantly disturbed areas
observed? If YES, identify their limits for they should be evaluated
separately for wetland determination purpose (usually after
evaluating undisturbed areas). Refer to the section on disturbed
areas (p.41) to evaluate the altered characteristic(s) (i.e.,
vegetation, soils, or hydrology). If appropriate, determine whether
wetland regulatory policy exempts the area from Federal regulatory
jurisdiction (e.g., regulatory policy on wetlands converted to
cropland); then return to this method to continue evaluating
characteristics not altered. Keep in mind that if at any time during
this determination one or more of these three characteristics are
found to have been significantly altered, the disturbed area
procedures should be followed. If the area is not significantly
disturbed, proceed to Step 2.
Step 2. Consider the following:
1) Is the area presently lacking hydrophytic vegetation or
hydrologic indicators due to annual, seasonal or long-term
fluctuations in precipitation, surface water, or ground-water
levels?
2) Are hydrophytic vegetation indicators lacking due to
seasonal fluctuations in temperature (e.g., seasonality of plant
growth)?
If the answer to either of these questions is YES or uncertain,
proceed to the section on difficult-to-identify wetland
determinations (p.31) . If the answer to both questions is NO, normal
conditions are assumed to be present, so proceed to Step 3. (Note;
In some cases, normal climatic conditions, such as snow cover or
frozen soils, may prevent an accurate assessment of the wetland
criteria; one must use best professional judgement to determine if
delaying the wetland delineation is appropriate.)
Step 3. Select representative observation area(s). Select one
or more representative observation areas within each community type.
A representative observation area is one in which the apparent
characteristics (determined visually) best represent characteristics
of the entire community. Mark the approximate location of the
observation areas on the base map or photo. Proceed to Step 4.
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Step 4. Characterize each plant community in the project area.
Within each plant community identified in Step l, visually estimate
the dominant plant species for each valid vegetative stratum in the
representative observation areas and record them on an appropriate
data form. Vegetative strata may include tree, sapling, shrub, herb,
woody vine, and bryophyte strata (see glossary for definitions).
Make sure the size of the observation area is sufficient to insure a
representative assessment of the plant community. A separate form
must be completed for each plant community identified for wetland
determination purposes. After identifying dominants within each
vegetative stratum, proceed to Step 5.
Step 5. Record the indicator status of dominant species in all
strata. Indicator status is obtained from the interagency Federal
list of plants occurring in wetlands for the appropriate geographic
region. Record indicator status for all dominant plant species on a
data form. Proceed to Step 6.
Step 6. Determine whether the hydrophytic vegetation criterion
is met. When more than 50 percent of the dominant species in each
community type have an indicator status of OBL, FACW, and/or FAC,
the hydrophytic vegetation criteria is met. Complete the vegetation
section of the data form. Portions of the project area failing this
test are usually not wetlands, although under certain circumstances
they may have wetland hydrology and therefore be wetland (see list
of difficult-to-identify wetlands on p.31). Proceed to Step 7.
Step 7. Determine whether soils must be characterized or
additional analysis is needed. Examine vegetative data collected for
each plant community (in Steps 5 and 6) and identify any plant
community where OBL species or OBL and FACW species predominate the
list of dominant plant species. In the absence of significant
hydrologic modification, these plant communities are considered
wetland (i.e., the. hydric soil and wetland hydrology criteria are
presumed to be met), but it may be advisable to record observations
of hydric soils and wetland hydrology, if assessing wetlands for
regulatory purposes; proceed to Steps 9 and 10 and quickly record
indicators of these criteria. Similarly, plant communities where UPL
species or UPL and FACU species predominate the list of dominants
are considered nonwetland. (CAUTION: Make sure that this plant
community is not a difficult-to-identify wetland, see p. 31.)
Proceed to Step 11. Plant communities lacking the above
characteristics must have soils closely examined; proceed to Step 8.
Step 8. Determine whether the hydric soil criterion is met.
Locate the observation area on a county soil survey map, if
possible, and determine the soil map unit delineation for the area.
Using a soil auger, probe, or spade, make a hole at least 18 inches
deep at the representative location in each plant community type.
Examine soil characteristics and compare if possible to soil
descriptions in the county soil survey report or classify to
Subgroup following "Soil Taxonomy" (often requires digging a deeper
>
50
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hole), or look for regional indicators of significant soil
saturation If soil has been plowed or otherwise altered, which may
have eliminated these indicators/ proceed to the section on
disturbed areas (p. 41). Complete the soils section on the
appropriate data sheet and proceed to Step 9 if conditions satisfy
the hydric soil criterion. Areas having soils that do not meet the
hydric soil criterion are nonwetlands. (CAUTION: Become familiar
with problematic hydric soils that do not possess good hydric field
indicators, such as red parent material soils, some sandy soils, and
some floodplain soils, so that these hydric soils are not
misidentified as nonhydric soils; see the difficult-to-identify
wetlands discussion on p.31.)
Step 9. Determine whether the wetland hydrology criterion is
met. Record observations and complete the hydrology section on the
appropriate data form. If the wetland hydroIgy criterion is net,
proceed to Step 10. If the wetland hydrology criterion is not met,
the area is nonwetland. (CAUTION: Seasonally saturated wetland may
not appear to meet the hydrology criterion at certain times of the
growing season; see discussion of difficult-to-identify wetlands,
page 31).
Step 10. Make the wetland determination. Examine data forms for
each plant community identified in the project area. Each community
meeting the hydrophytic vegetation, hydric soil, and wetland
hydrology criteria is considered wetland. If all communities meet
these three criteria, then the entire project area is a wetland. If
only a portion of the project area is wetland, then the
wetland-nonwetland boundary must be established. Proceed to Step 11.
Step 11. Determine the wetland-nonwetland boundary. Where a
base map or annotated photo was prepared, nark each plant community
type on the map or photo with a MW" if wetland or an "N" if
nonwetland. Combine all "W" types into a single mapping unit, if
possible, and all."N" types into another napping unit. On the map or
photo, the wetland boundary will be represented by the interface of
these mapping units. If flagging the boundary on the ground, the
boundary is established by determining the linits of the indicators
that verify all three criteria.
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APPENDIX 3. Intermediate-level Onsite Determination Method
On occasion, a more rigorous sampling method is required than the
routine method to determine whether hydrophytic vegetation is
present at a given site, especially where the boundary between
wetland and nonwetland is gradual or indistinct. This circumstance
requires more intensive sampling of vegetation and soils than
presented in the routine determination method. This method also may
be used for areas greater than five acres in size or other areas
that are highly diverse in vegetation.
The intermediate-level onsite determination method has been
developed to provide for more intensive vegetation sampling than the
routine method. Two optional approaches are presented: (1) quadrat
transect sampling procedure, and (2) vegetation unit sampling
procedure. The former procedure involves establishing transects
within the project area and sampling plant communities along the
transect within sample quadrats, with soils and hydrology also
assessed as needed in each sample plot. In contrast, the vegetation
unit sampling procedure offers a different approach for analyzing
the vegetation. First, vegetation units are designated in the
project area and then a meander survey is conducted in each unit
where visual estimates of percent areal coverage by plant species
are made. Soil and hydrology observations also are made as
necessary. Boundaries between wetland and nonwetland are established
by examining the transitional gradient between them.
The following steps should be completed:
Step 1. Locate the limits of the project area in the field and
conduct a general reconnaissance of the area. Previously the project
boundary should have been determined on aerial photos or maps. Now
appropriate ground reference points need to be located to insure
that sampling will be conducted in the proper area. In examining the
project area, were any significantly disturbed areas observed? If
YES, identify their limits for they should be evaluated separately
for wetland determination purposes (usually after evaluating
undisturbed areas). Refer to the section on disturbed areas (p. 41)
to evaluate the altered characteristic(s) (i.e., vegetation, soils,
or hydrology); then return to this method to continue evaluating, the
characteristics not altered. Keep in mind that if at any time during
this determination, one or more of these three characteristics is
found to have been significantly altered, the disturbed areas
procedures should be followed. If the area is not significantly
disturbed, proceed with Step 2.
Step 2. Decide how to analyze plant communities within the
project area: (1) by selecting representative plant communities
(vegetation units), or (2) by sampling along a transect. Discrete
vegetation units may be identified on aerial photographs,
topographic and other maps, and/or by field inspection. These units
>
52
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will be evaluated for hydrophytic vegetation and also for hydric
soils and wetland hydrology, as necessary, if the vegetation unit
approach is selected, proceed to Step 3. An alternative approach is
to establish transects for identifying plant communities, sampling
vegetation and evaluating other criteria, as appropriate. If the
transect approach is chosen, proceed to Step 4.
Step 3. Identifying vegetation units for sampling. Vegetation
units are identified by examining aerial photographs, topographic
naps, NWI maps, or other materials or, by direct field inspection.
All of the different vegetation units present in the project area
should be identified. The subject area should be traversed and
different vegetation units specifically located prior to conducting
the sampling.
Field inspection may refine previously identified vegetation units,
as appropriate. It may be advisable to divide large vegetation units
into subunits for independent analysis. (CAUTION: In highly variable
terrain, such as ridge and swale complexes, be sure to stratify
properly.) Decide which plant community to sample first and proceed
to Step 7.
Step 4. Establish a baseline for locating sampling transects.
Select as a baseline one project boundary or a conspicuous feature,
such as road, in the project area. The baseline should be more or ^
less parallel to the major watercourse through the area, if present^
or perpendicular to the hydrologic gradient (see Figure ) .
Determine the approximate baseline length. Proceed to Step 5.
Step 5. Determine the minimum number and position of transects.
Use the following to determine the minimum number and position of
transects (specific site conditions may necessitate changes in
intervals or additional transects). Divide the baseline length by
the number of required transects to establish baseline segments for
sampling. Establish one transect in each resulting baseline segment
(see Figure 4J . Use the midpoint of each baseline segment as a
transect starting point. For example, if the baseline is 1,200 feet
in length, three transects would be established: one at 200 feet,
one at 600 feet, and one at 1,000 feet from the baseline starting
point. Make sure that all plant community types are included within
the transects; this may'necessitate relocation of one or more
transect lines or establishing more transects. Each transect should
extend perpendicular to the baseline (see Figure 4J . Once positions
of transect lines are established, go to the beginning of the first
transect and proceed to Step 6.
Step 6. Locate sample plots along the transect. Along each
transect, sample plots are established within each plant community
encountered to assess vegetation, soils, and hydrology. When
identifying these sample plots, two approaches may be followed: (1)
walk the entire length of the transect, taking note of the number,
type, and location of plant communities present (flag the location,
53
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if necessary), and on the way back to the baseline, identify plots
and perform sampling, or (2) identify plant communities as the
transect is walked and sample the plot at that time ("sample as you
go"). The sample plot should be located so it is representative of
the plant community type. When the plant community type is large and
covers a significant distance along the transect, select an area
that is no closer than 300 feet to a perceptible change in plant
community type; mark the center of this area on the base map or
photo and flag the location in the field, if necessary. (CAUTION: In
highly variable terrain, such as ridge and swale complexes, be sure
to stratify properly to ensure best results.) At each plant
community, proceed to Step 7.
Step 7. Consider the following:
1) Is the area presently lacking hydrophytic vegetation or
hydrologic indicators due to annual, seasonal, or long-term
fluctuations in precipitation, surface water, or ground-water
levels?
2) Are hydrophytic vegetation indicators lacking due to
seasonal fluctuations in temperature (e.g., seasonality of plant
growth)?
If the answer to either of these questions is YES or uncertain,
proceed to the section on difficult-to-identify wetlands (p.'3lj ,
then return to this method and continue the wetland determination.
If the answer to both questions is NO, normal conditions are assumed
to be present, so proceed to Step 8. fNote; In some cases, normal
climatic conditions, such as snow cover or frozen soils, may prevent
an accurate assessment of the wetland criteria; one must use best
professional judgement to determine if delaying the wetland
delineation is appropriate.)
Step 8. Characterize the vegetation of the vegetation unit or
the plant community along the transect.
If analyzing vegetation units, meander through the unit making
visual estimates of the percent area covered for each species in the
herb, shrub, sapling, woody vine, and tree strata; alternatively,
for the tree stratum determine basal area using the Bitterlich
method (see Dilworth and Bell 1978; Avery and Burkhart 1983). Then:
1) Within each stratum determine and record the cover class of
each species and its corresponding midpoint. The cover classes (and
midpoints) are: T = <1% (none); 1 = 1-5% (3.0); 2 = 6-15% (10.5); 3
- 16-25% (20.5); 4 - 26-50% (38.0); 5 - 51-75% (63.0); 6 = 76-95%
(85.5); 7 - 96-100% (98.0).
2) Rank the species within each stratum according to their
midpoints. (Note; If two or more species have the same midpoints
and the same or essentially the same recorded percent areal cover,
54
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rank them equal; use absolute areal cover values as a tie-breaker
only if they are obviously different.)
3) Sum the midpoint values of all species within each stratum.
4) Multiply the total midpoint values for each stratum by 50
percent. (Note: This number represents the dominance threshold
number and is used to determine dominant species.)
5) Compile the cumulative total of the ranked species in each
stratum until 50 percent of the sum of the midpoints (i.e., the
dominance threshold number), for the herb, woody vine, shrub,
sapling, and tree strata (or alternatively basal area for trees) is
immediately exceeded. All species contributing areal cover or basal
area to the 50 percent threshold are considered dominants, plus any
additional species representing 20 percent or more of the total
cover class midpoint values for each stratum or the basal area for
tree stratum. (Note; If the threshold is reached by two or more
equally ranked species, consider them all dominants, along with any
higher ranked species. If all species are equally ranked, consider
them all dominants.)
6) Record all dominant species on an appropriate data sheet and
list indicator status of each. Proceed to Step 9.
If using the transect approach, sample vegetation in each stratum
(e.g., tree, shrub, herb, etc.) occurring in the sample plots using
the following quadrat sizes: (1) a 5-foot radius for bryophytes and
herbs, and (2) a 30-foot radius for trees, saplings, shrubs, and
woody vines. Plot size and shape may be changed as necessary to meet
site conditions, but be sure that it is sufficient to adequately
characterize the plant community. Determine dominant species for
each stratum by estimating one or more of the following as
appropriate: (1) relative basal area (trees); (2) areal cover
(trees, saplings, shrubs, herbs, woody vines, and bryophytes); or
(3) stem density (shrubs, saplings, herbs, and woody vines). When
estimating areal cover, use cover classes T (trace) through 7 and
use the midpoints of the cover classes to determine dominants, see
substeps 1 through 5 above. All plants covering the plot and
representative of the plant community under evaluation should be
counted in the cover estimate; plants overhanging from adjacent
plant communities should not be counted. Record all dominant species
on an appropriate data sheet and list the indicator status of each.
Proceed to Step 9.
Step 9. Determine whether the hydrophytic vegetation criterion
is met. When more than 50 percent of the dominant species in the
vegetation unit or sample plot have an indicator status of OBL,
FACW, and/or FAC, hydrophytic vegetation is present. If the
vegetation fails to be dominated by these types of species, the unit
or plot is usually not wetland, but check difficult-to-identify
wetlands and disturbed areas discussions for exceptions (pages 31
55
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and 41, respectively). If the hydrophytic vegetation criterion is
met, Proceed to Step 10 after completing the vegetation section of
the data sheet.
Step 10. Determine whether soils must be characterized or
additional analysis is needed. Examine vegetative data collected for
the vegetation unit or plot (in Steps 8 and 9) and identify any
plant community (units or plots) where OBL species or OBL and FACW
species predominate the list of dominants. In the absence of
significant hydrologic modification, these plant communities are
typically wetland (i.e., the hydric soil and wetland hydrology
criteria are presumed to be met), but it may be adviseable to record
indicators for the other criteria, especially if making a wetland
determination for regulatory purposes; proceed to Steps 11 and 12 as
necessary and record appropriate indicators.. Similarly, plant
communities where UPL species or UPL and FACU species predominate
the list of dominants are considered nonwetland. (CAUTION: Make sure
that this plant community is not a difficult-to-identify wetland,
see pp. 31). Proceed to Step 12. Plant communities (e.g., vegetation
units or plots) lacking the above characteristics must have soils
closely examined; proceed to Step 11.
Step 11. Determine whether the hydric soil criterion is met.
Locate the observation area on a county soil survey map, if
possible, and determine the soil map unit delineation for the area.
Using a soil auger, probe, or spade, make a hole at least 18 inches
deep at the representative location in each plant community type.
Examine soil characteristics and compare if possible to soil
descriptions in the county soil survey report or classify to
Subgroup following "Soil Taxonomy11 (often requires digging a deeper
hole), or look for regional indicators of significant soil
saturation. If soil has been plowed or otherwise altered, which may
have eliminated these indicators, proceed to the section on
disturbed areas (p.41). Complete the soils section on the
appropriate data sheet and proceed to Step 12 if conditions satisfy
the hydric soil criterion. Areas having soils that do not meet the
hydric soil criterion are nonwetlands. (CAUTION: Become familiar
with hydric soils that do not possess good hydric field indicators,
such as red parent material soils, some sandy soils, and some
floodplain soils, so that these hydric soils are not misidentified
as nonhydric soils; see the difficult-to-identify wetlands
discussion on p.31).
Step 12. Determine whether the wetland hydrology criterion is
met. Record observations and complete the hydrology section on the
appropriate data form. If the wetland hydrolgy criterion is met,
proceed to Step 13. If the wetland hydrology criterion is not net,
the area is nonwetland. (CAUTION: Seasonally saturated wetland may
not appear to meet the hydrology criterion at certain times of the
growing season; see discussion of difficult-to-identify wetlands,
page 31).
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Step 13. Make the wetland determination for the plant community
or vegetation unit. Examine the data fc-~is for the plant community M
(sample plot) or vegetation unit. Wher .'.e community or unit meets
the hydrophytic vegetation, hydric so:1. and wetland hydrology
criteria, the area is considered wetla-.= . Complete the summary data
sheet; proceed to Step 14 when continuing to sample the transect or
other vegetation units, or to Step 15 when determining, a boundary
between wetland and nonwetland plant communities or units. (Note:
Before going on, double check all data sheets to ensure that the
forms are completed properly.)
Step 14. Sample other plant communities along the transect or
other vegetation units. Repeat Steps 6 through 13 for all remaining
plant communities along the transect if following transect approach,
or repeat Steps 7 through 13 at the next vegetation unit. When
sampling is completed for this transect, proceed to Step 15, or when
sampling is completed for all vegetation units, proceed to Step 16.
Step 15. Determine the wetland-nonwetland boundary point along
the transect. When the transect contains both wetland and nonwetland
plant communities, then a boundary must be established. Proceed
along the transect from the wetland plot toward the nonwetland plot.
Look for the occurrence of UPL and FACU species, the appearance of
nonhydric soil types, subtle changes in hydrologic indicators,
and/or slight changes in topography. When such features are noted,
look closely for evidence of wetland hydrology in the soil (see p.
) and locate the wetland boundary (i.e., the point at which the
wetland hydrology criterion is no longer met). Establish sample
plots on each side of the boundary (e.g., within 50 feet) and repeat
Steps 8 through 13. If existing plots are within a reasonable
distance, additional plots may not be necessary, but always identify
the features that were used to identify the boundary. Data sheets
should be completed for each new plot. Mark the position of the
wetland boundary point on the base map or photo and stake or flag
the boundary in the field, as necessary. Continue along the transect
until the boundary points between all wetland and nonwetland plots
have been established. (CAUTION: In areas with a high interspersion
of wetland and nonwetland plant communities, several boundary
determinations will be required.) When all wetland determinations
along this transect have been completed, proceed to Step 17.
Step 16. Determine the wetland-nonwetland boundary between
adjacent vegetation units. Review all completed copies of the data
sheets for each vegetation unit. Identify each unit as either
wetland (W) or nonwetland (N). When adjacent vegetation units
contain both wetland and nonwetland communities, a boundary must be
established. Walk the interface between the two units from the
wetland unit toward the nonwetland unit and look for changes in
vegetation, soils, hydrologic indicators, and/or elevation. As a
general rule, at 100-foot intervals or whenever changes in the
vegetation unit's characteristics are noted, look for evidence to
locate the wetland-nonwetland boundary. At each designated boundary
57
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point, complete data sheets for new observation areas immediately
upslope and dovmslope of the wetland-nonwetland boundary (i.e., one
set for the wetland unit and one for the nonwetland unit), repeat
Steps 8 through 13 for each area, and record the distance and
compass directions between the boundary points. Record evidence of
wetland hydrology as close to the boundary as possible, and record
the features that were used to delineate the boundary. Mark the
position of the wetland boundary point on the base map or photo and
stake or flag the boundary in the field, as necessary. Based on
observations along the interface, identify other of boundary points
between each wetland unit and nonwetland unit. Repeat this step for
all adjacent vegetation units of wetland and nonwetland. When
wetland boundary points between all adjacent wetland and nonwetland
units have been established, proceed to Step 18.
Step 17. Sample other transects and make wetland determinations
along each. Repeat Steps 5 through 15 for each remaining transect.
When wetland boundary points for all transects have been
established, proceed to Step 18.
Step 18. Determine the wetland-nonwetland boundary for the
entire project area. Examine all completed copies of the data
sheets, and mark the location of each plant community type along the
transect on the base map or photo, when used. (Note; This has
already been done for the vegetation unit approach.) Identify each
plant community as either wetland (W) or nonvetland (N), if it has
not been done previously. If all plant communities are wetlands,
then the entire project area is wetland. If all communities are
nonwetlands, then the entire project area is nonwetland. If both
wetlands and nonwetlands are present, identify the boundary points
on the base map and connect these points on the map by generally
following contour lines to separate wetlands from nonwetlands.
Confirm this boundary by walking the contour lines between the
transects or vegetation units, as appropriate. Should anomalies be
encountered, it will be necessary to establish short transects in
these areas to refine the boundary; make any necessary adjustments
to the boundary on the base map and/or on the ground. If those areas
are significant in scope, be sure to record data used for the
boundary determination. When marking the boundary for subsequent
surveying by engineers, the boundary points should be flagged or
marked otherwise to facilitate the survey.
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APPENDIX 4. Comprehensive Onsite Determination Method
The comprehensive determination method is the most detailed,
complex, and labor-intensive approach of the three recommended types
of onsite determinations. It is usually reserved for highly
complicated and/or large project areas, and/or when the
determination requires rigorous documentation. Due to the latter
situation, this type of onsite determination may be used for areas
of any size.
In applying this method, a team of experts, including a wetland
ecologist and a soil scientist, is often needed, especially when
rigorous documentation of plants and soils are required. It is
possible, however, for a highly trained wetland boundary specialist
to singly apply this method.
Two alternative approaches of the comprehensive onsite determination
method are presented: (1) quadrat sampling procedure and (2) point
intercept sampling procedure. The former approach establishes
quadrats or sampling areas in the project site along transects,
while the latter approach involves a frequency analysis of
vegetation at sampling points along transects. The point intercept
sampling procedure requires that the limits of potential hydric
soils be established prior to evaluating the vegetation. In many
cases, soil maps are available to meet this requirement, but in
other cases a soil scientist may need to inventory the soils befor
applying this method. The quadrat sampling procedure, which involv
identifying plant communities along transects and analyzing
vegetation, soils, and hydrology within sample plots (quadrats), may
be the preferred approach when soil maps are unavailable or the
individual is more familiar with plant identification.
Quadrat Sampling Procedure
Prior to implementing this determination procedure, read the
sections of this manual that discuss disturbed area and difficult-
to-identify wetland section (p. 31) ; this information is often
relevant to project areas requiring a comprehensive determination.
Step 1. Locate the .limits of the project area in the field.
Previously, the project boundary should have been determined on
aerial photos or maps. Now appropriate ground reference points need
to be located to ensure that sampling will be conducted in the
proper area. Proceed to Step 2.
Step 2. Stratify the project area into different plant
community types. Delineate the locations of these types on aerial
photos or base maps and label each community with an appropriate
name. (CAUTION: In highly variable terrain, such as ridge and swale
complexes, be sure to stratify properly to ensure best results.) In
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evaluating the subject area, were any significantly disturbed areas
observed? If YES, identify their limits for they should be evaluated
separately for wetland determination purposes (usually after
evaluating undisturbed areas). Refer to the section on disturbed
areas (p.85) to evaluate the altered characteristic(s) (i.e.,
vegetation, soils, and/or hydrology); then return to this method to
continue evaluating the characteristics not altered. Keep in mind
that if at any time during this determination, it is found that one
or more or these three characteristics have been significantly
altered, the disturbed areas wetland determination procedures should
be followed. If the area is not significantly disturbed, proceed to
Step 3.
Step 3. Establish a baseline for locating sampling transects.
Select as a baseline one project boundary or a conspicuous feature,
such as a road, in the project area. The baseline ideally should be
more or less parallel to the major watercourse through the area, if
present, or perpendicular to the hydrologic gradient (see Figure 5).
Determine the approximate baseline length and record its origin,
length, and compass heading in a field notebook. When a limited
number of transects are planned, a baseline may not be necessary
provided there are sufficient fixed points (e.g., buildings, walls,
and fences) to serve as starting points for the transects. Proceed
to Step 4.
Step 4. Determine the required number and position of
transects. The number of transects necessary to adequately
characterize the site will vary due to the area's size and
complexity of habitats. In general, it is best to divide the
baseline into a number of equal segments and use the mid-point of
each baseline segment as the transect starting point (see Figure
). For example, if the baseline is 1,600 feet in length, four
transects will be established; one at 200 feet, one at 600 feet, one
at 1,000 feet, and one at 1,400 feet from the baseline starting
point. Each transect should extend perpendicular to the baseline.
Use the following as a guide to determine the minimum number of
baseline segments:
*If the baseline exceeds five miles, baseline segments should be 0.5
mile in length.
Make sure that each plant community type is included in at least one
transect; if not, modify the sampling design accordingly by
relocating one or more transect lines or by establishing additional
transects. When the starting points for all required transects have
been established, go to the beginning of the first transect and
proceed to Step 5.
Step 5. Identify sample plots along the transect. Along each
transect, sample plots may be established in two ways: (1) within
each plant community encountered (the plant community transect
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sampling approach); or (2) at fixed intervals (the fixed interval
transect sampling approach); these plots will be used to assess
vegetation, soils, and hydrology.
When employing the plant community transect sampling approach, two
techniques for identifying sample plots may be followed: (1) walk
the entire length of the transect, taking note of the number, type,
and location of plant communities present (flag the locations, if
necessary) and on the way back to the baseline, record the length of
the transect, identify sample plots and perform sampling; or (2)
identify plant communities as the transect is walked, sample the
plot at that time ("sample as you go"), and record the length of the
transect.
When conducting the fixed interval transect sampling approach,
establish sample plots along each transect using the following as a
guide:
The first sample plot should be established at a distance of 50 feet
from the baseline. When obvious nonwetlands occupy a long segment of
the transect from the baseline, begin the first plot in the
nonwetland at approximately 300 feet from the point where the
nonwetland begins to intergrade into a potential wetland community
type. Keep in mind that additional plots will be required to
determine the wetland-nonwetland boundary between fixed points. In
large areas having a mosaic of plant communities, one transect may
contain several wetland boundaries.
If obstacles such as a body of water or impenetrable thicket prevent
access through the length of the transect, access from the opposite
side of the project area may be necessary to complete the transect;
take appropriate compass reading and location data. At each sample
plot (i.e., plant-community or fixed interval area), proceed to Step
6. -
Step 6. Consider the following:
1) Is the area presently lacking hydrophytic vegetation or
hydrologic indicators due to annual, seasonal or long-term
fluctuations in precipitation, surface water, or ground-water
levels?
2) Are hydrophytic vegetation indicators lacking due to
seasonal fluctuations in temperature (e.g., seasonality of plant
growth)?
If the answer to either of these questions is YES or uncertain,
proceed to the section on difficult-to-identify wetland
determinations (p. 31). If the answer to both questions is NO,
normal conditions are assumed to be present. Proceed to Step 7 when
following the plant community transect approach. If following the
fixed interval approach, go to the appropriate fixed point along th||
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transect and proceed to Step 8. (Note: in some cases, normal
climatic conditions, such as snow cover or frozen soils, may prevent
an accurate assessment of the wetland criteria; one must use best
professional judgement to determine if delaying the wetland
delineation is appropriate.)
Step 7. Locate a sample plot in the plant community type
encountered. Choose a representative location along the transect in
this plant community. Select an area that is no closer than 50 feet
from the baseline or from any perceptible change in the plant
community type. Mark the center of the sample plot on the base map
or photo and flag the point in the field. Additional sample plots
should be established within the plant community at 300-foot
intervals along the transect or sooner if a different plant
community is encountered. (Note; In large-sized plant communities, a
sampling interval larger than 300 feet may be appropriate, but try
to use 300-foot intervals first.) Proceed to Step 8.
Step 8. Lay out the boundary of the sample plot. A circular
sample plot with a 30-foot radius should usually be established,
however, the size and shape of the plot may be changed to match
local conditions (e.g., narrow ridges and swales) as necessary. At
the flagged center of the plot, use a compass to divide the circular
plot into four equal sampling units at 90', 180*, 270", and 360*.
Mark the outer points of the plot with flagging. Proceed to Step 9.
Step 9. Characterize the vegetation and determine dominant
species within the sample plot. Sample the vegetation in each layer
or stratum (i.e., tree, sapling, shrub, herb, woody vine, and
bryophyte) within the plot using the following procedures for each
vegetative stratum and enter data on appropriate data sheet (see
Appendix for examples of data sheet):
1) Herb stratum " .
A) Sample this stratum using corresponding approach:
(1) Plant community transect sampling approach:
(a) Select one of the following designs:
(i) Eight (8) - 8" x 20" sample quadrats (two
for each sampling unit within the circular
plot); or
(ii) Four (4) - 20" x 20" sample quadrats (one
for each sample unit within the plot); or
(iii) Four (4) - 40" x 40" sample quadrats (one
for each sample unit).
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(Notei Alternate shapes of sample quadrats are
acceptable provided they are similar in area to
those listed above.)
(b) Randomly toss the quadrat frame into the
understory of the appropriate sample unit of the
plot.
(c) Record percent areal cover of each plant
species.
(d) Repeat (b) and (c) as required by the sampling
scheme.
(e) Construct a species area curve (see example,
Appendix . ) for the plot to determine whether
the number of quadrats sampled sufficiently
represent the vegetation in the stratum; the
number of samples necessary corresponds to the
point at which the curve levels off
horizontally; if necessary, sample additional
quadrats within the plot until the curve levels
off.
(f) For each plant species sampled, determine the
average percent areal cover by summing the
percent areal cover for all sample quadrats
within the plot and dividing by the total number
of quadrats (see example, Appendix ). Proceed
to substep B below.
(2) Fixed interval sampling approach:
(a) Place one (1) - 40" x 40" sample quadrat centered
on the transect point.
(b) Determine percent areal coverage for each
species. Proceed to substep B below.
B) Rank plant species by their average percent areal cover,
beginning with the most abundant species.
C) Sun the percent cover (fixed interval sampling approach)
or average percent cover (plant community transect
sampling approach).
D) Determine the dominance threshold number - the number at
which 50 percent of the total dominance measure (i.e.,
total cover) for the stratum is represented by one or more
plant species when ranked in descending order of abundance
(i.e., from most to least abundant).
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E) Sun the cover values for the ranked plant species
beginning with the most abundant until the dominance
threshold number is immediately exceeded; these species
contributing to surpassing the threshold number are
considered dominants, plus any additional species
representing 20 percent or more of the total cover of the
stratum; denote dominant species with an asterisk on the
appropriate data form.
F) Designate the indicator status of each dominant.
2) Bryophyte stratum (mosses, horned liverworts, and true
liverworts): Bryophytes may be sampled as a separate stratum in
certain wetlands, such as shrub bogs, moss-lichen wetlands, and the
wetter wooded swamps, where they are abundant and represent an
important component of the plant community. If treated as a separate
stratum, follow the same procedures as listed for herb stratum. In
many wetlands, however, bryophytes are not abundant and should be
included as part of the herb stratum.
3) Shrub stratum (woody plants usually between 3 and 20 feet tall,
including multi-stemmed, bushy shrubs and small trees below 20
feet):
A) Determine the percent areal cover of shrub species within
the entire plot by walking through the plot, listing all
shrub species and estimating the percent areal cover of
each species.
B) Indicate the appropriate cover class (T and 1 through 7)
and its corresponding midpoints (shown in parentheses) for
each species: T « <1% cover (None); 1 - 1-5% (3.0); 2 =
6-15% (10.5); 3 - 16-25% (20.5); 4 - 26-50% (38.0); 5 =
51-75% (63.0); 6 - 76-95% (85.5); 7 = 96-100% (98.0).
C) Rank shrub species according to their midpoints, from
highest to lowest midpoint;
D) Sum the midpoint values of all shrub species.
E) Determine the dominance threshold number - the number at
which 50 percent of the total dominance measure (i.e.,
cover class midpoints) for the stratum is represented by
one or more plant species when ranked in descending order.
F) Sum the midpoint values for the ranked shrub species,
beginning with the most abundant, until the dominance
threshold number is immediately exceeded; these species
are considered dominants, plus any additional species
representing 20 percent or more of the total midpoint
values of the stratum; identify dominant species (e.g.,
with an asterisk) on the appropriate data form.
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G) Designate the indicator status of each dominant.
4) Sapling stratum (young or small trees greater than or equal to
feet tall and with a diameter at breast height less than 5 inches) :
Follow the same procedures as listed for the shrub stratum or the
tree stratum (i.e., plot sampling technique), whichever is
preferred.
5) Woody vine stratum (climbing or twining woody plants): Follow the
same procedures as listed for the shrub stratum.
6) Tree stratum (woody plants greater than or equal to 20 feet tall
and with a diameter at breast height equal to or greater than 5
inches): Determine the basal area of the trees by individual and by
species within the 30-foot radius sample plot. Basal area for
individual trees can be calculated by measuring diameter at breast
height (dbh) with a diameter tape and converting diameter to basal
area using the formula A * £d2/4 (where A * basal area, £ = 3.1416,
and d - dbh).
Do the following steps:
A) Locate and mark, if necessary, a sample unit (plot) with a
radius of 30 feet, or change the shape of the plot to match
topography, or increase size of plot based on species area
curve assessment. (Note; A larger sampling unit may be required
when trees are large and widely spaced.)
B) Identify each tree within the plot, measure its dbh (using a
diameter tape), compute its basal area, then record data on the
data form. (Note; Compute basal area using the formula A =
I>d2/4, where A - basal area, B " 3.1416, and d = dbh. To
expedite this calculation, use a hand calculator into which the
following conversion factor is stored - 0.005454 for diameter
data in inches or 0.78535 in feet. Basal area in square feet of
an individual tree can be obtained by squaring the tree
diameter and multiplying by the stored conversion factor.)
C) Calculate the total basal area for each tree species by
summing the basal area values of all individual trees of each
species.
D) Rank species according to their total basal area, in
descending order from the largest basal area to the smallest.
E) Calculate the total basal area value of all trees in the
plot by summing the total basal area for all species.
F) Determine the dominant trees species; dominant species are
those species (when ranked in descending order and cumulatively
totaled) that immediately exceed 50 percent of the total basal
area value for the plot, plus any additional species comprising
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20 percent or more of the total basal area of the plot; record
the dominant species on the appropriate data form.
G) Designate the indicator status of each dominant (i.e., OBL,
FACW, FAC, .FACU, or UPL).
After determining the dominants for each stratum, proceed to Step
10.
Step 10. Determine whether the hydrophytic vegetation criterion
is met. When more than 50 percent of the dominant species in the
sample plot have an indicator status of OBL, FACW, and/or FAC,
hydrophytic vegetation is present. Complete the vegetation section
of the summary data sheet. If the vegetation fails to be dominated
by these types of species, the plot is usually not a wetland,
however, it may constitute hydrophytic vegetation under certain
circumstances (see disturbed areas discussion, on pp. 41, and the
list of difficult-to-identify wetlands on pp. 31). If hydrophytic
vegetation is present, proceed to Step 11. If the hydrophytic
vegetation criterion is not met, then the area is nonwetland.
Step 11. Determine whether the hydric soil criterion is met.
Locate the observation area on a county soil survey map, if
possible, and determine the soil map unit delineation for the area.
Using a soil auger, probe, or spade, make a hole at least 18 inches
deep at the representative location in each plant community type.
Examine soil characteristics and compare if possible to soil
descriptions in the county soil survey report or classify to
Subgroup following "Soil Taxonomy" (often requires digging a deeper
hole), or look for regional indicators of significant soil
saturation (Appendix ). If soil has been plowed or otherwise
altered, which may have eliminated these indicators, proceed to the
section on disturbed areas (p.41). Complete the soils section on
the appropriate data sheet and proceed to Step 9 if conditions
satisfy the hydric soil criterion. Areas having soils that do not
meet the hydric soil criterion are nonwetlands. (CAUTION: Become
familiar with hydric soils that do not possess good hydric field
indicators, such as red parent material soils, some sandy soils, and
some floodplain soils, so that these hydric soils are not
misidentified as nonhydric soils; see the difficult-to-identify
wetlands discussion on p. 31.)
Step 12. Determine whether the wetland hydrology criterion is
met. Record observations and complete the hydrology section on the
appropriate data form. If the wetland hydrolgy criterion is met,
proceed to Step 13. If the wetland hydrology criterion is not met,
the area is nonwetland. (CAUTION: Seasonally saturated wetland may
not appear to meet the hydrology criterion at certain times of the
growing season; see discussion of difficult-to-identify wetlands,
page 31).
Step 13. Make the wetland determination for the sample plot.
Examine the data forms for the plot. When the plot meets the
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hydrophytic vegetation, hydric soil, and wetland hydrology criteria
it is considered wetland. Complete the summary data sheet; proceed
to Step 14 when continuing to sample transects, or to Step 15 when
determining a boundary between wetland and nonwetland sample plots.
(Note: Double check all data sheets to ensure that they are
completed properly before going to another plot.)
Step 14. Take other samples along the transect. Repeat steps 5
through 13, as appropriate. When sampling is completed for this
transect proceed to Step 15.
Step 15. Determine the wetland-nonwetland boundary point along
the transect. When the transect contains both wetland and nonwetland
plots, then a boundary must be established. Proceed along the
transect from the wetland plot toward the nonwetland plot. Look for
the occurrence of UPL and FACU species, the appearance of nonhydric
soil types, subtle changes in hydrologic indicators, and/or slight
changes in topography. When such features are noted, evaluate the
three criteria and locate the wetland-nonwetland boundary (i.e., the
point at which one of the three wetland hydrology criterion is no
longer met; make sure, however, that this area does not qualify as a
problem area wetland) . Establish new sample plots on each side of
the boundary (e.g., within 50 feet) and repeat Steps 8 through 12.
If existing plots are within a reasonable distance of the boundary,
additional plots may not be necessary, but always document the
features that were used to identify the boundary. Data sheets should
be completed for each plot. Mark the position of the wetland
boundary point on the base map or photo and place a surveyor flag
stake at the boundary point in the field, as necessary. Continue
along the transect until the boundary points between all wetland and
nonwetland plots have been established. (CAUTION: In areas with a
high interspersion of wetland and nonwetland plant communities,
several boundary determinations will be required.) When all wetland
determinations along this transect have been completed, proceed to
Step 16.
Step 16. Sample other transects and make wetland determinations
along each. Repeat Steps 5 through 15 for each remaining transect.
When wetland boundary points for all transects have been
established, proceed to Step 17.
Step 17. Determine the wetland-nonwetland boundary for the
entire project area. Examine all completed copies of the data sheets
and mark the location of each plot on the base map or photo.
Identify each plot as either wetland (W) or nonwetland (N) on the
map or photo. If all plots are wetlands, then the entire project
area is wetland. If all plots are nonwetlands, then the entire
project area is nonwetland. If both wetland and nonwetland plots are
present, identify the boundary points on the base map or on the
ground, and connect these points on the map by generally following
contour lines to separate wetlands from nonwetlands. Confirm this
boundary on the ground by walking the contour lines between the
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transects. Should anomalies be encountered, it will be necessary to
establish short transects in these areas to refine the boundary,
apply Step 15, and make any necessary adjustments to the boundary on
the base map and/or on the ground, it may be worthwhile to place
surveyor flags or stakes at these boundary points, especially when
marking the boundary for subsequent surveying by engineers.
Point Intercept Sampling Procedure
The point intercept sampling procedure is a frequency analysis of
vegetation used in areas that may meet the hydric soil and wetland
hydrology criteria. It involves first identifying areas that may
meet the hydric soil and wetland hydrology criteria within the area
of concern and then refining the boundaries of areas that may meet
the hydric soil criterion for further examination. Transects are.
then established for analyzing vegetation and determining whether
hydrophytic vegetation criterion is met by calculating a prevalence
index. Sample worksheets and a sample problem using this method are
presented in Appendices . respectively.
Step 1. Identify the approximate limits of areas that may meet
the hydric soil criterion within the area of concern and sketch
limits on an aerial photograph. To help identify these limits use
sources of information such as Agricultural Stabilization and
Conservation Service slides, soil surveys, NWI maps, and other maps
and photographs. (Note: This step is more convenient to perform
offsite, but may be done onsite; some modification of study area
lines may be required after seeing the site in the field). Areas
that may meet the hydric soil criterion should be stratified into
areas of similar soils and similar vegetation lifeforms (e.g.,
forested wetland, shrub wetland, and emergent wetland) for further
analysis. Proceed to Step 2.
Step 2. Scan the areas that may meet the hydric soil criterion
and determine if disturbed conditions exist. Are any significantly
disturbed areas present? If YES, identify their limits for they
should be evaluated separately for wetland determination purposes
(usually after evaluating undisturbed areas). Refer to the section
on disturbed areas (p.41), if necessary/ to evaluate the altered
characteristic(s) (vegetation, soils, or hydrology), then return to
this method and continue evaluating characteristics not altered.
(Note: Prior experience with disturbed sites may allow one to easily
evaluate an altered characteristic, such as when vegetation is not
present in a farmed wetland due to cultivation.) Keep in mind that
if at any time during this determination one or more of these three
characteristics is found to have been significantly altered, the
disturbed area wetland determination procedures should be followed.
If the area is not significantly disturbed, proceed to Step 3.
Step 3. Scan the areas that may meet the hydric soil criterion
and determine if obvious signs of wetland hydrology or hydric soil
»
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are present. The wetland hydrology criterion is net for any area or
portion thereof where, it is obvious or known that the area is
frequently inundated or saturated to the surface during the growin
season. If the above condition exists, the hydric soil criterion is
presumed to be met for the subject area and the area is considered
wetland. If necessary (e.g., for a regulatory jurisdiction
delineation), confirm the presence of readily identified hydric soil
by examining the soil for appropriate properties and take note of
dominant plants which should easily meet the hydrophytic vegetation
criterion. If the area's hydrology has not been significantly
modified and the soil is organic (Histosols, except Folists) or is
mineral classified as Sulfaquents, Hydraguents, or Histic Subgroups
of Aquic Suborders according to "Soil Taxonomy", then the area is
also considered wetland. (Note; The hydrophytic vegetation criterion
is presumed to be met under these conditions, since the wetland
hydrology and hydric soil criteria are met, so vegetation may not
need to be examined, except for regulatory purposes. Regardless,
hydrophytic vegetation should be fairly obvious in these
situations.) Areas lacking obvious indicators of wetland hydrology
must be further examined, so proceed to Step 4.
Step 4. Refine the boundary of areas that meet the hydric soil
criterion. Verify the presence of hydric soil within the appropriate
map units by digging a number of holes at least 18 inches deep along
the boundary (interface) between hydric soil units and nonhydric
soil units. Compare soil samples with descriptions in the soil
survey report to see if they are properly napped, and look for soi
properties caused by wetland hydrology (see Appendix ). In th
way, the boundary of areas meeting the hydric soil criterion is
further refined by field observations. In map units where only part
of the unit is hydric (e.g., complexes, associations, and
inclusions), locate hydric soil areas on the ground by considering
landscape position and evaluating soil characteristics of the hydric
soil portion or for properties caused by wetland hydrology. (Note;
Some hydric soils, especially organic soils, have not been given a
series name and are referred to by common names, such as peat, muck,
swamp, marsh, wet alluvial land, tidal marsh, Sulfaquents, and
Sulfihemists; these areas are also considered hydric soil map units
and should appear on the county lists of hydric soil map units.
Certain hydric soils are mapped with nonhydric soils as an
association or complex, while other hydric soils occur as inclusions
in nonhydric soil map units. Only the hydric soil portion of these
map units should be evaluated for hydrophytic vegetation.) In areas
where hydric soils are not easily located by landscape position and
soil characteristics (morphology), a soil scientist should be
consulted. (CAUTION: Become familiar with hydric soils that do not
possess good hydric field indicators, such as red parent material
soils, some sandy soils, and some floodplains soils, so that these
hydric soils are not misidentified as nonhydric soils, see section
on difficult-to-identify wetlands, p. 31.) fNote; If the project
area does not have a soil map, hydric soil areas must be determined
in the field to use the point intercept sampling method. Consider
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landscape position, such as depressions, drainagevays, floodplains,
and seepage slopes, and either classify the soil or look for field
indicators of hydric soil, then delineate the hydric soil areas
accordingly. If the boundary of the hydric soil area cannot be
readily delineated, one should use the quadrat sampling procedure
(page )
After establishing the boundary of the area in question, proceed to
Step 5.
Step 5. Consider the following:
1) Is the area presently lacking hydrophytic vegetation or
hydrologic indicators due to annual, seasonal, or long-term
fluctuations in precipitation, surface water, or ground water
levels?
2) Are hydrophytic vegetation indicators lacking due to
seasonal fluctuations in temperature (e.g., seasonality of plant
growth)?
If the answer to either of these questions is YES or uncertain,
proceed to the section on problem area wetland determinations (p.
_). If the answer to both questions is NO, normal conditions are
assumed to be present. Proceed to Step 6. (Note; In some cases,
normal climatic conditions, such as snow cover or frozen soils, may
prevent an accurate assessment of the wetland criteria; one must use
best professional judgement to determine if delaying the wetland
delineation is appropriate.)
Step 6. Determine random starting points and random directions
for three 200-foot line transects in each area that meets or may
meet the hydric soil criterion. (Note; More than three transects may
be required depending on the standard error obtained for the three
transects.) There"are many ways to determine random starting points
and random transect direction. The following procedures are
suggested:
1) Starting point - Starting points for the transects are
selected randomly along the perimeter of the area to be examined.
Determine the approximate perimeter length and select three random
numbers (from a table for generating random numbers or other
suitable method); these random numbers indicate the position of the
starting points for the three transects; pick a point along the
perimeter to begin pacing off the distance to the starting points.
2) Transect direction - At a starting point, spin a pencil or
similar pointed object in the air and let it fall to the ground. The
direction that the pencil is pointing indicates the direction of the
transect. Proceed to Step 7.
Step 7. Lay out the transect in the established direction. If
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the transect crosses the hydric soil boundary (into the nonhydric
soil area) , bend the line back into the hydric soil area by random;
selecting a new direction for the transect following the procedure'
suggested above, Mark the approximate location of the transect on a
base map or aerial photo. Proceed to Step 8.
Step 8. Record plant data (e.g., species name, indicator group,
and number of occurrences) at interval points along the transect.
Only individual plants with stems located in the subject area (i.e.,
soil type) should be recorded. At the starting point and at each
point on 2-foot intervals along the transect, record all individual
plants that would intersect an imaginary vertical line extending
through the point. Count each individual plant only once per sample
point; each individual of a single species counts as a separate
plant for the tally (e.g., three individuals of red maple count as
three hits for red maple at that single point) . If this imaginary
line has no plants intersecting it (either above or below the sample
point), record nothing. Identify each plant observed to species (or
other taxonomic category if species cannot be identified), enter
species name on the Prevalence Index Worksheet, and record all
occurrences of each species along the transect. Tor each species
listed, identify its indicator group from the appropriate regional
list of plant species that occur in wetlands (i.e., OBL, FACW, FAC,
FACU, and UPL; see pp. ) . Plant species not recorded on the lists
are assumed to be upland species. If no regional indicator status
and only one national indicator status is assigned, apply the
national indicator status to the species. If no regional indicator,
status is assigned and more than one national indicator status is
assigned, do not use the species to calculate a prevalence index. If
the plant species is on the list and no regional or national
indicator status is assigned, do not use the species to calculate
the prevalence index. For a transect to be valid for a prevalence
calculation, at least 80 percent of the occurrences must be plants
that have been identified and placed in an indicator group. Get help
in plant identification if necessary. Unidentified plants or plants
without indicator status are recorded but are not used to calculate
the prevalence index. Proceed to Step 9.
Step 9. Calculate the total frequency of occurrences for each
species (or other taxonomic category), for each indicator group of
plants, and for all plant species observed, and enter on the
Prevalence Index Worksheet. The frequency of occurrences of a plant
species equals the number of times it occurs at the sampling points
along the transect. Proceed to Step 10.
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Step 10. Calculate the prevalence index for the transect using
the following formula:
IFo + 2Ffv + 3Ff + 4Ffu + 5Fu
Pli = ,. Fo + Ffw -I- Ff * Ffu + Fu
where
Pli « Prevalence Index for transect i;
Fo * Frequency of occurrence of obligate wetland (OBL) species;
Ffw « Frequency of occurrence of facultative wetland (FACW)
species;
Ff « Frequency of occurrence of facultative (FAC) species;
Ffu « Frequency of occurrence of facultative upland (FACU) species;
Fu •= Frequency of occurrence of upland (UPL) species.
After calculating and recording the prevalence index for this
transect, proceed to Step 11.
Step 11. Repeat Steps 5 through 10 for two other transects.
After completing the three transects, proceed to Step 12.
Step 12. Calculate a mean prevalence index for the three
transects. To be considered wetland, a hydric soil area usually must
have a mean prevalence index (PIM) of less than 3.0. A minimum of
three transects are required in each delineated area of hydric soil,
but enough transects are required so that the standard error for PIM
does not exceed 0.20 percent.
Compute the mean prevalence index for the three transects by using
the following formula:
PIM - PIT
N
where - •
PIM - mean prevalence index for transects;
PIT « sum of prevalence index values for all transects;
N = total number of transects.
After computing the mean prevalence index for the three transects,
proceed to Step 13.
Step 13. Calculate the standard deviation (s) for the
prevalence index using the following formula:
(PI1-PIMJ2 + (PI2-PIM)2 + (PI3-PIMJ2
s '
N-l
(Note; See formulas in Steps 8 and 10 for symbol definitions.)
After performing this calculation, proceed to Step 14.
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Step 14. Calculate the standard error (sx) of the mean
prevalence index using the following formula:
:s
where
s ** standard deviation for the Prevalence Index
N « total number of transects
(Note: The sx cannot exceed 0.20. If sx exceeds 0.20, one or more
additional transects are required. Repeat Steps 6 through 14, as
necessary, for each additional transect.) When sx for all transects
does not exceed 0.20, proceed to Step 15.
Step 15. Record final mean prevalence index value for each
hydric soil nap unit and make a wetland determination. All areas
having a mean prevalence index of less than 3.0 meet the hydrophytic
vegetation criterion (see p. 18) . If the community has a prevalence
index equal to or greater than 3.0, it is usually not hydrophytic
vegetation except under certain circumstances; consult the section
on difficult-to-identify wetlands (p. 31) for these exceptions.
Proceed to Step 16.
Step 16. Determine whether the wetland hydrology criterion i
met. Record observations and complete the hydrology section on the
appropriate data form. If the wetland hydrolgy criterion is met,
then the area is considered a wetland. If the area has been
hydrologically disturbed, one must determine whether the area is
effectively drained before making a wetland determination; this type
of area should have been identified in Step 2 (see disturbed areas
discussion, page 41) . If the area is effectively drained, it is
considered nonwetland; if it is not, the wetland hydrology driterion
is met and the area is considered a wetland. (CAUTION: Seasonally
saturated wetland may not appear to meet the hydrology criterion at
certain times of the growing season; see discussion of difficult-to-
identify wetlands, page 31) .
Step 17. Delineate the wetland boundary. After identifying the
wetland, delineate the boundary by refining the limits of the area
that meets the all three criteria (including any problem area
wetlands). Mark the boundaries with flagging tape, if necessary.
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APPENDIX 5. Descriptions of Difficult-to-Identify Wetlands.
Prairie Potholes.
Potholes are glacially-formed depressions that are capable of
storing water (Eisenlohr 1972). They are generally located in
the north central United States and southern Canada. Although
potholes may occur in forested areas, the majority occur in the
prairie region where they are subject to arid or semi-arid
climatic conditions. Most potholes are small, generally less
than an acre in size.
Pothole soils are generally poorly drained, slowly permeable
soils capable of ponding water. Precipitation is the basic
source of water in potholes. Runoff from the drainage area is
highly variable, but it is the key in determining if and how
long ponding will occur. Precipitation in the pothole region
varies appreciably from year to year. Average precipitation is
far too small to meet the demands of evaporation and as a
result most potholes are dry for a significant portion of the
year, containing water for only a short period generally early
in the growing season. In years of drought, potholes may not
pond water at all. However in most years, seasonal
replenishment can be expected (Eisenlohr 1972).
In certain areas, the vast majority of potholes are farmed,
either occasionally or every year, depending upon the duration
of ponding. Many potholes have been either partially or totally
drained to enhance agricultural production. The drastically
fluctuating climate and alteration for fanning have resulted in
highly disturbed conditions that make wetland identification
difficult. Aerial photographs, ASCS compliance slides, and
other offsite information that depict long-term conditions are
often better indicators of wetland conditions than onsite
indicators reflecting only a single point in time.
Plant communities in potholes are usually disturbed, either
naturally or due to farming, and many do not exhibit vegetation
typical of more stable wetlands. The process of annual drying
(drawdown) in potholes enables the invasion of FAC, FACU, or
UPL plant species during dry periods which may persist into the
wet seasons. Stewart and Kantrud (1971) have recognized this
condition in describing vegetation phases in their
classification of wetlands for the Prairie Pothole Region. The
phases are as follows:
For nohcropland areas:
Drawdown bare soil phase. As surface water in the open
water phase gradually recedes and disappears, expanses of
bare mud flats, which often become dry, are exposed.
Ordinarily, this phase is of short duration, but in
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intermittent-alkali zones and occasionally in the more
saline deep marsh zones, it nay persist for considerable
periods.
Natural drawdown emergent chase. Undisturbed areas with
emergent drawdown vegetation are considered to be in this
phase. This growth is composed mostly of annual plants,
including many forbs, that germinate on the exposed mud or
bare soil of the drawdown bare soil phase. After the
drawdown emergents become established, surface water is
occasionally restored by heavy summer rains.
Characteristic plant species of this phase include:
Eleocharis acicularis (terrestrial form), Rumex maritimus,
Kochia scoparia, Xanthium italicum, Chenopodium rubruro,
and Senecio congestus.
For cropland area1
Cropland drawdown ase. Tilled pothole bottoms with
drawdown vegetatic. characterize this phase. The plants
include many coarse, introduced annual weeds and grasses
that normally develop on exposed mud flats during the
growing season. These species appear as overwinter
emergents whenever surface water is restored by summer
rains. Characteristic plant species include: Agropyron
repens, Echinochloa crusgalli, Polygonum lapathifolium,
Veronica peregrina, Hordeum jubatum, Plagiobothrys
scopulorum, Xanthium italicum, Bidens frondosa, Seteria
glauca, Polygonum convolvulus, Agropyron snithii, Brassica
kaber, Descruainia sophia, Androsace occidentalis, Ellisia
nyctelea, Erigeron canadensis, and Iva xanthifolia.
Cropland tillage phase. In this phase, tilled bottom, soils
are dominated by annual field weeds, characteristic of
fallow or neglected low cropland. Tilled dry pothole
bottoms devoid of vegetation are also considered to be in
this phase. Planted small grain or row crops are often
present.
Plavas.
Playas occur in many arid or semiarid regions of the world.
Although occurring throughout much of the western United
States, they are concentrated in the southern Great Plains as
either ephemeral or permanent lakes or wetlands (Nelson et. al.
1983) . The topography of most playa regions is flat to gently
rolling and generally devoid of drainage. Runoff from the
surrounding terrain is collected into playa basins, where water
is evaporated rapidly. Playas range in size from several
hundred acres to only a few acres, with the majority being less
than 10 acres.
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Surface soils of playas are generally clays that form a highly
impermeable seal and increase their water-holding capacity. The
playa soils are typically Vertisols. In the southern Great
Plains, playa soils are listed as Randall, Lipan, or Ness
clays, Stegall silty clay loams, Lofton clay loams, or may be
uncharacterized occurring as inclusions within nonhydric soil
map units. Soils of playas are generally distinguishable from
surrounding upland soils because of their contrasting darker
color (Reed 1930).
The hydrology of playas involves rapid accumulation of natural
runoff during late spring, with a gradual loss by evaporation
and seepage through the summer except where basins have been
excavated to concentrate water. The hydrology is influenced by
agricultural practices, including basin modification for water
collection and retention and grazing in the watershed. Water
reaching the playa is derived primarily from precipitation and
runoff within the basin watershed.
Playa basins are dry most of the time. The basins collect water
primarily in two peak periods - May and September -as a result
of regional convectional storms common throughout the region.
Water collection in the basins is generally representative of
seasonal or long-term extremes and not average annual
conditions. As a result, wetland hydrology is best
characterized by examining hydrological indicators over a
multi-year period rather than relying on hydrological
conditions that may be present at any point in time.
The hydrology of most playa wetlands seldom allows a stable
flora to develop. Playa basins may have a dense cover of annual
or perennial vegetation or may be barren, depending on the
timing, intensity and amount of precipitation and irrigation
runoff, the extent of grazing, and the size of the playas. As
with potholes, the process of annual drying (drawdown) in
playas enables the invasion of FAC, FACU, and UPL plants during
dry periods which may persist into other seasons. Playa basins
may show vegetative zonation in concentric bands from the basin
center to the perimeter in response to decreasing water depths
or soil moisture levels. However, such zonation is not typical
of all playa basins; small playas that collect limited runoff
may support prairie vegetation (primarily FACU and UPL species)
or may be cultivated. Cultivated basins often contain either
the living plants or remnants of smartweeds (Polygonum spp.),
ragweeds (Ambrosia spp.), or other invading annuals. Some playa
basins are large enough to have an open expanse of deep water
that may support aquatic plant communities.
Vernal Pools.
Vernal pools are depressional areas covered by shallow water
for variable periods from winter to spring, but may be
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completely dry for most of the summer and fall. Small pools
may drain completely several times during the rainy season a
some pools may not retain any water during drought years.
An understanding of the natural history of the plants that
occur in the transitional areas from pool to typically
terrestrial habitat is useful in delineating these wetlands.
Zedler (1987) provides an excellent overview of vernal pools
which is briefly summarized below.
Vernal pools are wide-ranging in size (from 10 feet wide to 10
acres) but are always shallow (less than 6 inches to 2 feet
deep). Depth and duration of saturation and inundation are
more important in defining a vernal pool than size. Soils with
confining layers, either nearly impermeable clay layers or
iron-silica cemented hardpans, often have a seasonally perched
water table which favors the development of vernal pool.
Microrelief on the soils typically is hummocky, with pits
(depressions) and mounds. Individual vernal pools are often
interconnected by a series of swales and tributaries, winter
rainfall perches on the confining layer, until removed by
evapotranspiration in the spring. A cemented hardpan or nearly
impermeable clay subsoil layer, the pit and mound microrelief,
and presence of swales are strong indicators of vernal pools.
Vernal pools hold water long enough to allow some strictly
aquatic organisms to grow and reproduce (complete their life
cycles), but not long enough to permit the development of a
typical pond or marsh ecosystem. Changes in a vernal pool
during the season are so dramatic that it is in some ways more
appropriate to consider it to be sequence of ecosystem (a
cyclical wetland) rather than a single static type. Vernal
pool development can be broken into four phases: (1) wetting
phase, (2) aquatic phase, (3) drying phase, and (4) drought
phase. The first rains stimulate the germination of dormant
seeds and the growth of perennial plants (wetting phase). When
the cumulative rainfall is sufficient to saturate the soils,
aquatic plants and animals proliferate (aquatic phase).
Nonaquatic plants are subjected to stress at this time. As the
pool levels begin to recede (drying phase), the high soil
moisture insures that plant growth continues after standing
water is gone. Eventually, the plants succumb to drought and
turn brown, with drying cracks appearing in the soil (drought
phase).
Plant species characteristic of vernal pools are endemic to
vernal pools, or occur in vernal pools but are common in other
aquatic habitats or associated with vernal pools (see Tables
6A-D in Zedler, 1987). Non-pool species can tolerate the
limited periods of standing water that exist toward the pool
margins.
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Since vernal pools typically vary considerably in depth and
duration or both from year to year, within a year, or between
different pools, plant composition is quite dynamic. FAC, FACU
and UPL species often invade the pool basins in dry years, as
they do in .other seasonally variable wetlands. Lack of
hydrophytic plant species also may be indicative of recent
disturbances such as off-road vehicle activities,, farming, or
grazing. In delineating these wetlands, it is important to be
aware not only of the "pool" but of the vernal pool complex
(pool, basin, swales, tributaries), parts of which may have
shorter and more variable periods of inundation.
Other Seasonally Variable Wetlands.
In many regions (especially in arid and semiarid regions and areas
with distinct wet and dry seasons), depressional areas occur that
may have evidence of all three wetland criteria during the wetter
portion of the growing season, but normally lack evidence of wetland
hydrology and/or hydrophytic vegetation during the drier portion of
the growing season. In addition, some of these areas lack hydric
soil properties. Seasonal changes in plant species dominance may
create problems for recognizing these wet during dry periods. While
OBL and FACW plant species are nonnallly dominant during the wetter
portion of the growing season, FACU and UPL species (usually
annuals) may be dominant during the drier portion of the growing
season and during and for some time after droughts. Examples of
seasonally variable wetlands are pothole wetlands in the upper
Midwest, playa wetlands in the Southwest, and vernal pools along the
West Coast; these are discussed above. Become familiar with the
ecology of these and similar types of wetlands (see Appendix for
readings). Also, be particularly aware of drought conditions that
permit invasion of UPL species (even perennials).
Vegetated River Bars and Adjacent Flats. Along western streams in
arid and semiarid parts of the country, some river bars and flats
may be vegetated by FACU species while others may be colonized by
wetter species. If these areas are frequently inundated and/or
saturated sufficient to meet the wetland hydrology criterion, they
are wetlands. They may be subject to flooding more than once during
the growing season, depending on rainfall patterns. The soils often
do not reflect the characteristic morphological properties of hydric
soils, however, and thereby pose delineation problems.
Difficult-to-Identify Wetland Situations
Certain situations encountered in the field make wetland
identification and delineation difficult. These situations are
discussed below along with guidance on how to handle them.
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created wetlands. These wetlands include manmade (artificial)
wetlands, beaver-created wetlands, and other wetlands that have
recently formed due to natural processes. Artificial wetlands may be
purposely or accidentally created (e.g., road impoundments,
undersized culverts, irrigation, and seepage from earth-dammed
impoundments) by human activities. Many of these areas will have
evidence of wetland hydrology and hydrophytic vegetation. The area
should lack typical morphological properties of hydric soils, since
the soils have just recently been inundated and/or saturated. Since
all of these wetlands are newly established, evidence of one or more
of the wetland identification criteria may not be present. One must
always consider the relative permanency of the wetter conditions.
For example, if a beaver has recently blocked a road culvert that
has now caused flooding of nonwetland (e.g., upland forest or
field), it is quite possible that the blockage will soon be removed.
In this case, the action is considered nonpermanent and the area is
not considered wetland. If, however, hydrophytic vegetation has
colonized the area, the hydrology is considered more or less
permanently altered and the area is considered wetland. Temporary
roads may impede the natural flow of water and impound water for
some time. Yet, since the road is only temporary, the effect is also
temporary, so the area is not considered wetland, unless, of course,
it was wetland prior to the road construction.
Wetlands on glacial till or in rockv areas.
Sloping wetlands occur in glaciated areas where soils cover
relatively impermeable glacial till or where layers of glacial till
have different hydraulic conditions that permit groundwater seepage.
Such areas are seldom, if ever, flooded, but downslope groundwater
movement keeps the soils saturated for a sufficient portion of the
growing season to produce anaerobic and reducing soil conditions.
This promotes the development of hydric soils and hydrophytic
vegetation. Evidence of wetland hydrology may be lacking during the
drier portion of the growing season. Hydric soil properties also may
be difficult to observe because certain areas are so rocky that it
is difficult to examine soil characteristics within 18 inches.
Wetland-nonwetland mosaics. In numerous areas, including northern
glaciated regions and the coastal plain, the local topography may be
pockmarked with a complex of "pits" (depressions) and "mounds"
(knolls). The pits may be wet enough to be classified as wetland,
whereas the mounds are usually nonwetland. (Note; In some areas, the
shallow mounds are also wetland. When this is true, the entire area
is wetland.) The interspersion of wet pits and dry mounds may make
the delineation of the wetland boundary difficult when the pits are
too small to separate from the mounds. Of course, any area should
be mapped within practical limits. When it is not practicable to
separate the wet pits from the dry mounds, it is recommended that
the wetland-nonwetland boundary be delineated by assessing the
percent of the area covered by the wetland pits in an area of
similar pit-mound relief. At least two random transects should be
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established to determine the percent of pits vs. mounds. Based on
the assessment at two-foot intervals along each transect, the
percent of wetland vs. upland points can be established for the
area. Consult the appropriate regulatory agency to learn what ratio
they want to consider "wetland" for regulatory purposes. One should
also note in his or her field report that this protocol was used and
give an estimated size range for the wetland pits (e.g., 3-5'
diameter) as well as a brief narrative description of the site.
Cyclical wetlands. While the hydrology of all wetlands varies
annually, the hydrology of certain wetlands may naturally fluctuate
in a cyclical patterns of a series of consecutive wet years followed
by a series of dry years. During the wet periods, hydrophytic
vegetation and wetland hydrology are present, yet during the dry
periods, the hydrology does not appear to meet the wetland hydrology
criterion and FACU and UPL plant species often become established
and may predominate under these temporal drier conditions. Despite
the lack of periodic flooding or saturated soils for a multi-year
period, these area should still be considered wetland, since in the
long run, wetland characteristics prevail. Specific examples of
cyclic wetlands include Alaska's black spruce-permafrost wetlands
(see Alaska in regional list above), groundwater wetlands of the
Cimmaron Terrace of Oklahoma and Kansas, and wetlands in coastal and
West Texas (see Midwest regional list above). Other cyclical
wetlands are associated with drought-prone areas such as southern
California and the arid and semi-arid regions of the country.
Vegetated Flats. Vegetated flats are characterized by a marked
seasonal periodicity in plant growth. They are dominated by annual
OBL species, such as wild rice (Zizania aguatica), and/or perennial
OBL species, such as spatterdock (Nuphar luteum), that have
nonpersistent vegetative parts (i.e., leaves and stems breakdown
rapidly during the winter, providing no evidence of the plant on the
wetland surface at the beginning of the next growing season). During
winter and early spring, these areas lack vegetative cover and
resemble mud flats; therefore, they do not appear to qualify as
wetlands. But during the growing season the vegetation becomes
increasingly evident, qualifying the area as wetland. In evaluating
these areas, which occur both in coastal and interior parts of the
country (e.g., regularly flooded freshwater tidal marshes and
exposed shores of lakes or reservoirs during drawdowns due to
natural fluctuations or human actions), one must consider the time
of year of the field observation and the seasonality of the
vegetation. Again, one must become familiar with the ecology of
these wetland types (see Appendix for readings).
Interdunal swale wetlands. Along the U.S. coastline, seasonally wet
swales supporting hydrophytic vegetation are located within sand
dune complexes on barrier islands and beaches. Some of these swales
are inundated or saturated to the surface for considerable periods
during the growing season, while others are wet for only the early
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part of the season. In some cases, swales may be flooded irregularly
by the tides. These wetlands have sandy soils that generally lack
evidence of hydric soil properties. In addition, evidence of wetlanl
hydrology may be absent during the drier part of the growing season.
Consequently, these wetlands may be difficult to identify.
Springs and seepage wetlands. Wetlands occurring in flowing waters
from springs and groundwater seepage areas may not exhibit typical
hydric soil properties due to oxygen-enriched waters. Springs have
permanently flowing waters, while seepage flows may be seasonal.
Not all seepage areas, however, are considered wetlands. To qualify
as wetland, the following conditions should be met: (1) 'seepage flow
by oxygen-enriched waters is continuous for at least a 30-day period
during the growing season in most years and saturate the soil to the
surface, and (2) OBL and/or FACW species predominate or have a
prevalence index less than or equal to 2.5. Soils wet for this
duration are typically considered to have an aquic moisture regime
and are hydric. The outer boundary of these wetlands is established
by the limits of predominance of OBL and/or FACW species.
Drought-affected Wetlands. Droughts periodically occur in many
parts of the country, especially in the semiarid and arid West.
During drought, it is quite obvious that water will not be observed
in many wetlands, especially those higher up on the soil moisture
gradient. With the drying of these wetlands over a number of
consecutive years, environmental conditions no longer favor the
growth of hydrophytic vegetation, so FACU and UPL species become
established and often predominate in time. Thus, the plant
community composition changes to one that is no longer dominated by
hydrophytes. Such communities fail to meet the hydrophytic
vegetation criterion, unless treated as problem area wetlands which
is the case. Drought-affected wetlands should be identified by the
presence of hydric soils, further refined by clear signs of long-
term hydrology as .expressed in the soil by: Thick organic surface
layers, gleyed layers, low chroma matrices with high chroma mottles,
and others listed as regional wetland hydrology indicators.
Additional verification of hydrology may be advisable for some sites
and an examination of aerial photographs during the wet part of the
growing season in years of normal precipitation (distributions and
amount) should reveal signs of wetland hydrology. In addition,
landscape position (e.g., depressions and sloughs) may provide
additional evidence for recognizing these wetlands during droughts.
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APPENDIX 6. Difficult-To-Identify Hydric Soils
Some hydric soils are soils lacking diagnostic hydric soil
properties or soils that may look like hydric soils in terms of soil
color, but whose color is not the result of excess wetness.
Presumably, the area in question has been located on a soil survey
map that identified it as a hydric component of a map unit on the
county list of hydric soil map units or if no maps are available,
soil properties (matrix colors) that appear to contradict landscape
position (e.g., red-colored soils in obvious depressions or gray-
colored soils in obvious uplands) have been observed. Problem area
soils are discussed in the following subsection.
To determine whether the area in question is wetland, emphasis will
be placed on vegetation and signs of hydrology, yet always consider
landscape position in assessing the likelihood of wetland in these
situations.
Seven types of these hydric soils are recognized and discussed
below.
Hvdric Entisols ffloodplain and sandy soils). Entisols are usually
young or recently formed soils that have little or no evidence of
pedogenically developed horizons (U.S.D.A. Soil Survey Staff 1975) .
These soils are typical of floodplains throughout the U.S., but are
also found in glacial outwash plains, along tidal waters, and in
other areas. They include sandy soils of riverine islands, bars, and
banks and finer-textured soils of floodplain terraces. Wet entisols
have an aquic or peraquic moisture regime and are considered hydric
soils, unless effectively drained. Some Entisols are easily
recognized as hydric soils such as the Sulfaquents of tidal salt
marshes and Hydraquents, whereas others pose problems because they
do not possess typical hydric soil field indicators. Wet sandy
Entisols (with loamy fine sand and coarser textures in horizons
vithin 20 inches of the surface) may lack sufficient organic matter
and clay to develop hydric soil colors. When these soils have a hue
between 10YR and 10Y and distinct or prominent mottles present, a
chroma of 3 or less is permitted to identify the soil as hydric
(i.e., an aquic moisture regime). Also, hydrologic data showing that
the soil is flooded or ponded enough to be wetland are sufficient to
verify these soils as hydric. Sandy Entisols must have positive
indicators of hydrology (see positive indicators for sandy soils for
your region) in the upper 6 inches and have colors of the loamy fine
sand or coarser Aquents. Soils that key to the aerie suborder or
have colors of the aerie suborder within 12 inches are not
considered hydric soils. Other Entisols are considered hydric if
they classify in the aquic suborder and have the colors as listed
for soils that are finer than loamy fine sand in some or all layers
to a depth of 12 inches. Soils that key to the aerie subgroup or
have aerie colors above 12 inches as listed for Aquent subgroups are
not hydric.
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Hydric Mollisols fprairie and steppe soils). Mollisols are dark
colored, base-rich soils. They are common in the central part of the
conterminous U.S. from eastern Illinois to Montana and south to
Texas. Natural vegetation is mainly tall and mid grass prairies and
short grass steppes. These soils typically have deep, dark-colored
surface (mollic epipedons) and subsurface layers that have color
values of less than 4 moist and commonly have chromas of 2 or less.
The low chroma colors of Mollisols are not necessarily due to
wetness of periods of saturation. They are rich in organic natter
due largely to the vegetation (deep roots) and reworking of the soil
and organic matter by earthworms, ants, moles, and rodents. The low
chroma colors of Mollisols are not necessarily due to prolonged
saturation, so be particularly careful in making wetland
determinations in these soils. Many Great Groups of aquic Mollisols
do not have aerie subgroups. Therefore, if a Mollisol is classified
as an Aguoll, special care is needed to determine if it is hydric.
There are two suborders of Mollisols that have aquic moisture
regimes: Albolls and Aguolls. Albolls have an albic horizon that
separates the surface layer from an argillic or natric horizon. The
albic horizon must have chromas of 2 or less or the albic, argillic,
or natric horizons must have characteristics associated with wetness
such as mottles, iron-manganese concretions larger than 2 nun or
both. All Albolls are considered hydric soils. Aguolls exhibiting
regional hydrology characteristics for Mollisols in the upper part
are considered hydric.
Hydric Oxisols. These soils are highly weathered, reddish,
yellowish, or grayish soils of tropical and subtropical regions.
They are mixtures of quartz, kaolin, free oxides, and organic
matter. For the most part, they are nearly featureless soils without
clearly distinguishable horizons. Oxisols normally occur on stable
surfaces and weathering has proceeded to great depths. To be hydric,
these normally red-colored soils are required to have chromas 2 or
less immediately below the surface layer, or if there are distinct
or prominent mottles, the chroma is 3 or less. They also qualify as
hydric if they have continuous plinthite within 12 inches of the
surface.
Hydric Spodosols (evergreen forest soils). These soils, usually
associated with coniferous forests, are common in northern temperate
and boreal regions of the U.S. and along the Gulf-Atlantic Coastal
Plain. Spodosols have a gray eluvial E-horizon overlying a
diagnostic spodic horizon of accumulated (sometimes weakly cemented)
organic matter, aluminum, and iron (U.S.D.A. Soil Survey Staff
1975). A process called podzolization is responsible for creating
these two soil layers. Organic acids from the leaf litter on the
soil surface are moved downward through the soil with rainfall,
cleaning the sand grains in the first horizon (the E-horizon) then
coating the sand grains with organic matter and iron oxides in the
second layer (the spodic horizon). Certain vegetation produce
organic acids that speed podzolization including eastern hemlock
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(Tsuga canadensis), spruces (Picea spp.), pine (Pinus spp.), larches
(Larix spp.)/ and oaks (Quercus spp.) (Buol, et al. 1980). The E-
horizon or Albic horizon by definition has a chroma of 3 or less and
is often mistaken for a gleyed layer by the novice. These Spodosols
must have one of the positive regional hydrology indicators and meet
the color requirement for Aguods listed in "Soil Taxonomy." Hydric
Spodosols that have a thick (more than 12 inches) sandy epipedon are
extremely difficult to identify especially in the Gulf-Atlantic
Coastal Plain. These soils must also meet the color requirements for
the Aquod suborder and meet one of the regional hydrology indicators
for sandy soils.
Hvdric Vertisols (shrink and swell soils). These soils are dark-
colored clayey soils that are extensive in the Great Plains, in the
southern U.S., and in parts of California. They develop wide, deep
cracks when dry and swell shut, when wet. Many Vertisols exhibit
gilgai microtopography with swells and swales or mounds and hollows.
The morphology of these soils may be distinctly different on the
mound and in the hollow. They commonly have thick dark-colored
surface layers because of the churning action created by the
shrinking and swelling clays. During wet periods, they are very
slowly permeable and may pond water on the surface of the micro-
hollows, but in dry periods they are rapidly permeable with water
travelling along the deep cracks to lower layers. These soils must
meet one of the regional hydrology indicators for Vertisols to
qualify as hydric.
Hvdric soils derived from red parent material. Hydric mineral soils
derived from red parent materials (e.g., weathered clays, Triassic
sandstones, and Triassic shales) may lack the low chroma colors
characteristic of most hydric mineral soils. In these soils, the hue
is redder than 10YR because of parent materials that remain red
after citrate-dithionite extraction, so the low chroma requirement
for hydric soil is waived (U.S.D.A. Soil Conservation Service 1982) .
Red soils are most"common along the Gulf-Atlantic Coastal Plain
(Ultisols), but are also found in the Midwest and parts of the
Southwest and West (Alfisols), in the tropics, and in glacial areas
where older landscapes of red shales and sandstones have been
exposed. In southern New England, red parent material hydric soils
are derived from reddish sandstone, shale, conglomerate, or basalt.
These soils include the following series: Meno (Aerie Haplaguepts),
Wilbraham (Aquic Dystrochrepts), Lim (Aerie Fluvaguents), and Bash
(Fluvaquentic Dystrochrepts). In the absence of diagnostic hydric
soil properties, more weight must be placed on the vegetation and
hydrology. Follow procedures for identifying wetlands in problem
area soils at the beginning of this subsection.
Hydric soils derived from low chroma parent materials. Soils derived
from slate and phyllite produce low chroma colors due to this parent
material. In southern New England, nonhydric soils having
predominantly low chroma colors include the following series:
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Newport, Nassau, Dutchess, Bernardston, Pittstown, Dummerston,
Taconic, Macomber, Lakesboro, and Fullan. A few series derived from,
these materials are hydric, including Stissing, Brayton, and
Mansfield, with the first two including nonhydric members as well.
Due to the difficulty of using soil colors as indicators of wetness,
more weight must be placed on vegetation and hydrology. Follow
procedures for identifying wetlands in problem area soils at the
beginning of this subsection.
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APPENDIX 7. Procedures for Difficult-to-Identify Wetlands
Difficult-to-identify wetlands are to be identified using the
procedures below. These procedures should only be used in
accordance with the guidance for difficult-to-identify wetlands on
Page 31. :
1. What is the reason for the difficulty in wetland
identification/delineation? (Identify only one of the parameters as
the basis for this difficulty):
If vegetation is the criterion for which a positive indicator
was not identifiable, go to 2a. If soils, go to 2b. If hydrology,
go to 2c.
2a. Is the plant community growing on a soil that meets the
hydric soil criterion on page 22?
If no, the area is non-wetland.
If yes, document the reasons for this conclusion and go to
3a.
3a. Are one or more of the following conditions satisfied?:
* hydrologic records or aerial photography
combined with hydrologic records (items l and 2
on page 11) document wetland hydrology; or
* one or more primary hydrologic indicators (item
3 on page 11) is documented to have been found
at the site; or
* one or more secondary hydrologic indicators are
materially present and supported by
corroborative information as described in item 4
on page 12 (e.g., regional indicators of
saturation, hydrologic gauge data, NWI naps).
If no, the area is non-wetland.
If yes, the area is a wetland; document the reasons
for this conclusion. The upper boundary of these
wetlands is established by the limits of the
combination of the wetland hydrology indicators
present and hydric soil.
2b. Does the soil support a plant community that meets the
hydrophytic vegetation criterion on page 18?
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If no, the area is non-wetland.
If yes, document the reasons for this conclusion and go
to 3b.
3b. Are one or more of the following conditions
satisfied:
* hydrologic records or aerial photography
combined with hydrologic records (items l and 2
on page 11) document wetland hydrology; or
* one or more primary hydrologic indicators (item
3 on page 11) is documented; or
* one or more secondary hydrologic indicators are
materially present and supported by
corroborative information as described in item 4
on page 12 (e.g., regional indicators of
saturation, hydrologic gauge data, NWI maps)?
If no, the area is non-wetland.
If yes, the area is a wetland; document the reasons
for this conclusion. The upper boundary of these
wetlands is established by the limits of the
combination of the wetland hydrology indicators
present and hydrophytic vegetation.
2c. Is the plant community growing on a soil that meets the
hydric soil criterion on page 22 ?
If no, the area is non-wetland.
If yes, document the reasons for this conclusion and go to
3c.
3c. Does the area demonstrate a regional indicator of
saturation (see Appendix -)
If no, go to 5c.
If yes, go to 4c.
4c. Does the area support a plant community that meets
the hydrophytic vegetation criterion on page 18 ?
If no, the area is non-wetland.
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If yes, the area is a wetland. Document the reasons for
this conclusion. The upper boundary of this wetland is
established by the limits of the combination of
hydrophytic vegetation, hydric soils, and the regional
indicators of saturation present.
5c. Does the percent cover of obligate wetland (OBL) and
facultative wetland (FACW) species in all strata
except the tree stratum exceed that of the
facultative upland (FACU) and upland (UPL) species in
the all strata except the tree stratum or does the
plant community have a mean prevalence index of less
than 3.0?
If no, the area is non-wetland.
If yes, the area is wetland; document the
reasons for this conclusion. The upper boundary
of this wetland is established by the limits of
the combination of the wetland vegetation as
described in this step and hydric soils.
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APPENDIX 8. Disturbed Area Procedures
Step 1. Determine whether vegetation, soils, and/or hydrology
have been significantly altered at the site. Proceed to Step 2.
Step 2. Determine whether the "altered" characteristic met the
wetland criterion in question prior to site alteration. Review
existing information for the area (e.g., aerial photos, NWI maps,
soil surveys, hydrologic data, and previous site inspection
reports), contact knowledgeable persons familiar with the area, and
conduct an onsite inspection to build supportive evidence. The
strongest evidence involves considering all of the above plus
evaluating a nearby reference site (an area similar to the one
altered before modification) for field indicators of the three
technical criteria for wetland. If a human activity or natural event
altered the vegetation, proceed to Step 3; the soils, proceed to
Step 4; the hydrology, proceed to Step 5.
Step 3. Determine whether the hydrophytic vegetation criterion
was met prior to disturbance:
1) Describe the type of alteration. Examine the area and
describe the type of alteration that occurred. Look for evidence of
selective harvesting, clearcutting, bulldozing, recent conversion to
agriculture, or other activities (e.g., burning, discing, the
presence of buildings, dams, levees, roads, and parking lots).
2) Determine the approximate date when the alteration occurred
if necessary. Check aerial photographs, examine building permits,
consult with local individuals, and review other possible sources of
information.
3) Describe -the effects on the vegetation. Generally describe
how the recent activities and events have affected the plant
communities. Consider the following:
A) Has all or a portion of the area been cleared of
vegetation?
B) Has only one layer of the plant community (e.g., trees)
been removed?
C) Has selective harvesting resulted in the removal of
some species?
D) Has the vegetation been burned, mowed, or heavily
grazed?
E) Has the vegetation been covered by fill, dredged
material, or structures?
F) Have increased water levels resulted in the death of
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all or some of the vegetation?
4) Determine whether the area had plant communities that met
the hydrophytic vegetation criterion. Develop a list of species that
previously occurred at the site from existing information, if
possible, and determine whether the hydrophytic vegetation criterion
was met. If site-specific data do not exist, then do the following,
as appropriate:
A) If the vegetation is removed and no other alterations
are done, then the presence of hydric soils and evidence
of wetland hydrology will be used to identify wetlands.
If such evidence is found, conditions are assumed to be
sufficient to support hydrophytic vegetation. It may be
advantageous to examine a nearby reference site to collect
data on the plant community to confirm this assumption.
(Note; Determination of regulatory jurisdiction for such
areas is subject to agency interpretation. For example,
Federal wetland regulatory policy under the Clean Water
Act, and agricultural program policy under the Food
Security Act of 1985, as amended, interprets the relative
permanence of disturbance to vegetation caused by
cropping. Be sure to consult appropriate agency in making
Federal wetland jurisdictional determinations in such
areas.)
B) If the area is filled, burying the vegetation,"and no
other alterations (i.e., to hydrology or soils) have taken
place, then either: (1) look below the fill layer for
hydric soil and indicators of wetland hydrology, plus any
signs of hydrophytic vegetation (if not decomposed), or
(2) if type of fill (e.g., concrete) precludes examination
of soil beneath the fill, then review existing information
(e.g., soil survey, wetland maps, and aerial photos) to
determine if the area was wetland. If necessary, evaluate
a neighboring undisturbed area (reference site) with
characteristics (i.e., vegetation, soils, hydrology, and
topography) similar to the area in question prior to its
alteration. Be sure to record the location and major
characteristics (vegetation, soils, hydrology, and
topography) of the reference site. Sample the vegetation
in this reference area using an appropriate onsite
determination method to determine whether hydrophytic
vegetation is present. If the hydrophytic vegetation
criterion is met at the reference site, then this
criterion is presumed to have been met in the altered
area. If no indicators of hydrophytic vegetation are found
at the reference site, then the original vegetation at the
project area is not considered to have met the hydrophytic
vegetation criterion.
C) If soils and/or hydrology also have been disturbed,
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then continue Steps 4,5, and 6 below, as necessary.
Otherwise, return to the applicable step of the onsite
determination method being used.
Step 4. Determine whether or not hydric soils previously
occurred:
1) Describe the type of alteration. Examine the area and
describe the type of alteration that occurred. Look for
evidence of:
A) Deposition of dredged or fill material - In many cases
the presence of fill material will be obvious. If so, it
will be necessary to dig a hole to reach the original soil
(sometimes several feet deep). Fill material will usually
be a different color or texture than the original soil
(except when fill material has been obtained from similar
areas onsite). Look for decomposing vegetation between
soil layers and the presence of buried organic or hydric
mineral soil layers. In rare cases, excessive deposition
of sediments may be due to catastrophic conditions, e.g.,
mud slides and volcanic eruptions. Floodplain environments
are subjected to periodic sedimentation, but this is a
more normal occurrence and does not constitute a
significant disturbance for purposes of this manual.
B) Presence of nonwoody debris at the surface - This can
only be applied in areas where the original soils do not
contain rocks. Nonwoody debris includes items such as
rocks, bricks, and concrete fragments.
C) Subsurface plowing - Has the area recently been plowed
below the A-horizon or to depths of greater than 10
inches? "
D) Removal of surface layers - Has the surface soil layer
been removed by scraping or natural landslides? Look for
bare soil surfaces with exposed plant roots or scrape
scars on the surface.
E) Presence of manmade structures - Are buildings, dams,
levees, roads, or parking lots present?
2) Determine the approximate date when the alteration
occurred, if necessary. Check aerial photographs, examine
building permits, consult with local individuals, and
review other possible sources of information.
3) Describe the effects on soils. Consider the following:
A) Has the soil been buried? If so, record the depth of
fill material and determine whether the original soil,was
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left intact or disturbed. (Note: The presence of a typical
sequence of soil horizons or layers in the buried soil is
an indication that the soil is still intact; check
description in the soil survey report.)
B) Has the soil been nixed at a depth below the A-horizon
or greater than 12 inches? If so, it will be necessary to
examine the soil at a depth immediately below the plow
layer or disturbed zone.
C) Has the soil been sufficiently altered to change the
soil phase? Describe these changes. If a hydric soil has
been drained to some extent, refer to Step 5 below to
determine whether soil is effectively drained or is still
hydric.
4) Characterize the soils that previously existed at the
disturbed site. Obtain all possible evidence that may be
used to characterize soils that previously occurred on the
area. Consider the following potential sources of
information:
A) Soil surveys - In many cases, recent soil surveys are
available. If so, determine the soils that were mapped for
the area. If all soils are hydric soils, it is presumed
that the entire area had hydric soils prior to alteration.
Consult aerial photos to refine hydric soil boundaries,
especially for soil map units with hydric soil inclusions.
B) Buried soils - When fill material has been placed over
the original soil without physically disturbing the soil,
examine and characterize the buried soils. Dig a hole
through the fill material until the original soil is
encountered. Determine the point at which the original
soil material begins. Remove 18 inches of the original
soil from the hole and follow standard procedures for
determining whether the hydric soil criterion is met (see
p. ). (Note; When the fill material is a thick layer,
it might be necessary to use a backhoe or posthole digger
to excavate the soil pit.) If USGS topographic maps
indicate distinct variation in the area's topography, this
procedure must be applied in each portion of the area that
originally had a different surface elevation.
C) Deeply plowed soils or removed surface layers - If soil
surface layers are removed, redistributed or deeply plowed
(excluding r.ormal plowing), vegetation will not be
present, so review existing information (e.g., soil
surveys, wetland maps, and aerial photos), identify a
nearby reference site that is similar to disturbed area
prior to its alteration, evaluate for indicators of
hydrophytic vegetation, hydric soils, and wetland
hydrology and make wetland or nonwetland determination, as
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appropriate.
5) Determine whether hydric soils were present at the project
area prior to alteration. Examine the available data and
determine whether evidence of hydric soils were formerly
present. If no evidence of hydric soils is found, the
original soils are considered nonhydric soils. If evidence
of hydric soils is found, the hydric soil criterion has
been met. Continue to Step 5 if hydrology also was
altered. Otherwise, record decision and return to the
applicable step of the onsite determination method being
used.
Step 5. Determine whether wetland hydrology existed prior to
alteration and whether wetland hydrology still exists (i.e., is the
area effectively drained?). To determine whether wetland hydrology
still occurs, proceed to Step 6. To determine whether wetland
hydrology existed prior to the alteration:
1) Describe the type of alteration. Examine the area and
describe the type of alteration that occurred. Look for
evidence of:
A) dams - Has recent construction of a dam or some natural
event (e.g., beaver activity or landslide) caused the area
to become increasingly wetter or drier? (Note: This
activity could have occurred at a considerable distance
from the site in question, so be aware of and consider the
impacts of major dams in the watershed above the project
area.)
B) levees, dikes, and similar structures - Have levees or
dikes been recently constructed that prevent the area fron
periodic overbank flooding?
C) ditches or drain tiles - Have ditches or drain.tiles
been recently constructed causing the area to drain more
rapidly?
D) channelization - Have feeder streams recently been
channelized sufficiently to alter the frequency and/or
duration of inundation?
E) filling of channels and/or depressions (land-leveling)
- Have natural channels or depressions been recently
filled?
F) diversion of water - Has an upstream drainage pattern
been altered that results in water being diverted from the
area?
G) groundwater withdrawal - Has prolonged and intensive
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pumping of groundwater for irrigation or other purposes
significantly lowered the water table and/or altered
drainage patterns?
2) Determine the approximate date when the alteration
occurred, if necessary. Check aerial photographs, consult
with local individuals, and review other possible sources
of information.
3) Describe the effects of the alteration on the area's
hydrology. Consider the following and generally describe
how the observed alteration affected the project area:
A) Is the area more frequently or less frequently
inundated than prior to alteration? To what degree and
why?
B) Is the duration of inundation and soil saturation
different than prior to alteration? How much different and
why?
4) Characterize the hydrology that previously existed at the
area. Obtain and record all possible evidence that nay be
useful for characterizing the previous hydrology. Consider
the following:
A) stream or tidal gauge data - If a stream or tidal
gauging station is located near the area, it may be
possible to calculate elevations representing the upper
limit of wetland hydrology based on duration of
inundation. Consult SCS district offices, hydrologists
from the local CE district offices or other agencies for
assistance. If fill material has not been placed on the
area, survey this elevation from the nearest USGS
benchmark. If fill material has been placed on the area,
compare the calculated elevation with elevations shown on
a USGS topographic map or any other survey map that
predates site alteration.
B) field hydrologic indicators onsite or in a neighboring
reference area - Certain field indicators of wetland
hydrology may still be present. Look for water marks on
trees or other structures, drift lines, and debris
deposits (see pp. 17-19 for additional hydrology
indicators). If adjacent undisturbed areas are in the same
topographic position, have the same soils (check soil
survey map),' and are similarly influenced by the same
sources of inundation, look for wetland hydrology
indicators in these areas.
C) aerial photographs - Examine aerial photographs and
determine whether the area has been inundated or saturated
*
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during the growing season. Consider the time of the year
that the aerial photographs were taken and use only
photographs taken prior to site alteration.
D) historical records - Examine historical records for
evidence that the area has been periodically inundated.
Obtain copies of any such information.
E) National Flood Insurance Agency flood maps - Determine
the previous frequency of inundation of the area from
national floods maps (if available).
F) local government officials or other knowledgeable
individuals - Contact individuals who might have knowledge
that the area was periodically inundated or saturated.
If sufficient data on hydrology that existed prior to site
alteration are not available to determine whether wetland hydrology
was previously present, then use the other wetland identification
criteria (i.e., hydrophytic vegetation and hydric soils) to make a
wetland determination.
5) Determine whether wetland hydrology previously occurred.
Examine available data. If hydrology was significantly
altered recently (e.g., since Clean Water Act), was
wetland hydrology present prior to the alteration? If the
vegetation and soils have not been disturbed, use site
characteristics - vegetation, soils, and field evidence ol
wetland hydrology - to identify wetland. If vegetation
and soil are removed, then review existing information
(e.g., soil surveys, wetland maps, and aerial photos),
following procedures in Step 6, substep 3. If no evidence
of wetland hydrology is found, the original hydrology of
the area is not considered to meet the wetland hydrology
criterion. If evidence of wetland hydrology is found, the
area used to meet the wetland hydrology criterion. Record
decision and return to the applicable step of the onsite
determination method being used.
Step 6. Determine whether wetland hydrology still exists. Many
wetlands have a single ditch running through them, while others may
have an extensive network of ditches. A single ditch through a
wetland may not be sufficient to effectively drain it; in other
words, the wetland hydrology criterion still may be met under these
circumstances. Undoubtedly, when ditches or drain tiles are
observed, questions as to the extent of drainage arise, especially
if the ditches or drain tiles are part of a more elaborate stream
channelization or other drainage project. In these cases and other
situations where the hydrology of an area has been significantly
altered (e.g., dams, levees, groundwater withdrawals, and water
diversions), one must determine whether wetland hydrology still
exists. If it is present, the area is not effectively drained. If
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wetland hydrology is not present, the area is not a wetland. TO
determine whether wetland hydrology still exists:
1) Describe the type or nature of the alteration. Look for
evidence of:
A) dams;
B) levees, dikes, and similar structures;
C) ditches;
D) channelization;
E) filling of channels and/or depressions;
F) diversion of water; and
G) groundwater withdrawal.
(See Step 5 above for discussion of these factors.)
2) Determine the approximate date when the alteration occurred,
if necessary. Check aerial photographs, consult with local
officials, and review other possible sources of information.
3) Characterize the hydrology that presently exists at the
area. When evaluating agricultural land to determine the presence or
absence of wetland, it is recognized that such lands are generally
disturbed and must be viewed in that context. Wetland hydrology is
often altered on agricultural lands, so the mere presence o.f soils
meeting the hydric soil criterion is not sufficient to determine
that wetlands are present. Due to the common hydrologic and
vegetative modifications on agricultural lands, indicators of
wetland hydrology, together with soil-related properties, are the
roost reliable means of wetland identification. The following
procedure is designed to provide technical guidance for determining
whether an area subject to some degree of hydrologic modification
still meets the wetland hydrology criterion. In general, the
hydrology of most such areas can be evaluated by reviewing existing
site-specific information, examining aerial photographs, or
conducting onsite inspections to look for evidence of wetland
hydrology (substeps A-F). More rigorous assessment (substep G) may
be done less commonly where despite the lack of wetland hydrology
evidence one has a strong suspicion that wetland hydrology still
exists. The reason for doing this more detailed assessment should be
documented. CAUTION: WHEN THE HYDROLOGY OF AN AREA HAS BEEN
SIGNIFICANTLY ALTERED, SOIL CHARACTERISTICS RESULTING FROM WETLAND
HYDROLOGY CANNOT BE USED TO VERIFY WETLAND HYDROLOGY SINCE THEY
PERSIST AFTER WETLAND HYDROLOGY HAS BEEN ELIMINATED.) Figure
shows the sequence of substeps
required to evaluate whether the wetland hydrology criteria is met.
A) Review existing site-specific hydrologic information to see
if data support the wetland hydrology criterion. If such data
are unavailable or inconclusive, proceed to Step 2.
B) Examine aerial photographs (preferably early spring or wet
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growing season) for several recent years (e.g., a minimum of 5
years is recommended), look for signs of inundation or
prolonged soil saturation, and consider these observations in
the context of long-term hydrology. (Note: Large-scale aerial
photographs, 1:24,000 and larger, are preferred.) Be sure to
know the prevailing environmental conditions for all dates of
photography. Try to avoid abnormally wet or dry dates for they
may lead to erroneous conclusions about wetland hydrology. You
are attempting to assess conditions during normal rainfall
years. If the area is wet more years than not during normal
rainfall years (e.g., 3 of 5 years or 6 or 10 years), then the
wetland hydrology criterion is presumed to be met. If the area
shows no indication of wetness during normal rainfall years or
shows such signs in only a few years (e.g., 1 of 5 years or 3
of 10 years), then the wetland hydrology criterion is presumed
not to be met. If conditions are between the two mentioned
above (e.g., 2 of 5 years or 4-5 of 10 years), proceed to
substep C. (Note; Only those areas showing signs of wetness
should be considered to meet the wetland hydrology criterion.)
C) Examine additional aerial photos, National Wetland Inventory
maps, or other information for indication of wetland or signs
of wetland hydrology. If other information, coupled with the
previous information is substep B, indicates that the area is
wet more often than not (e.g., 3 of 5 years or 6 of 10 years),
or indicates that the area is wet half of the time (e.g., 3 of
6 years or 5 of 10 years), then the wetland hydrology criterion
is presumed to be met. If other information, coupled with the
previous information in substep 2, provides indication that the
area is wet less often than not (e.g., 2 of 5 years or 4 of 10
years), then the wetland hydrology criterion is presumed not to
be met. If it is perceived after reviewing additional
information that wetland hydrology is still inconclusive,
proceed to substep D.
D) Inspect the site for direct evidence of inundation or
prolonged soil saturation or other field evidence of wetland
hydrology (excluding soil properties resulting from long-term
hydrology) to determine whether the wetland hydrology criterion
is met. Ideally, such inspection should be done during the
early or wet part of the growing season during a normal
rainfall year. Avoid periods after heavy rainfall or
immediately after more normal rainfalls. After conducting the
onsite inspection, if necessary, proceed to substep E in areas
where vegetation has not been removed or cultivated or to
substep G in cultivated areas to perform a more rigorous
assessment of vegetation and/or hydrology and document your
reason for doing so.
E) Inspect the site, on the ground to assess changes in the
plant community. If OBL or OBL and FACW plant
species (especially in the herb stratum) are dominant or
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scattered throughout the site and UPL species are absent or not
dominant, the area is considered to meet the wetland hydrology
criterion and remains wetland. If UPL species predominate one
or more strata (i.e., they represent more than 50 percent of
the dominants in a given stratum) and no OBL species are
present, then the area is considered effectively drained and is
no longer wetland. fNote; Make sure that the UPL species are
materially present and dominate a valid stratum, see p. ).
If the vegetation differs from the above situations, then the
vegetation at this site should be compared if possible with a
nearby undisturbed reference area, so proceed to substep F; if
it is not possible to evaluate a reference site and the area is
ditched, channelized or tile-drained, go to substep G.
F) Locate a nearby undisturbed reference site with vegetation,
soils, hydrology, and topography similar to the subject area
prior to its alteration, examine the vegetation (following an
appropriate onsite delineation method), and compare it with the
vegetation at the project site. If the vegetation is similar
(i.e., has the same dominants or the subject area has different
dominants with the same indicator status or wetter as the
reference site), then the area is considered to be wetland —
the wetland hydrology criterion is presumed to be satisfied. If
the vegetation has changed to where FACU and UPL species or UPL
species alone predominate and OBL species are absent, then the
area is considered effectively drained and is nonwetland. If
the vegetation is different than indicated above, additional
work is required — go to substep G.
G) Select one of the following approaches to further assess the
area's hydrology:
(1) Determine the "zone of influence" of the drainage
structure and its effect on the water table using
existing SCS soil drainage guides, the ellipse
equation, or similar drainage model (SCS soil
drainage guides and the ellipse equation relate only
to water table and do not address surface water), and
determine the effect of the drainage structure on
surface water (ponding and flooding). Factors to
consider when analyzing the effect of the drainage
structure on surface water are: (a) the type of
drainage system (e.g., size, spacing, depth, grade,
and outlet conditions); (b) surface inlets; (c)
condition of the drainage system; (d) how surface
water is removed; and (e) soil type as it related to
~ runoff. An example using the ellipse equation to
calculate the zone of influence is given in Appendix
; or,
(2) Conduct detailed ground water studies, making direct
observations of inundation and soils saturation
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throughout the area in question. Data should be
collected in the following manner:
(a) Depth of Wells. Well should be placed
within 24 inches of the soil surface or to the
top of the restrictive horizon, if shallower.
(b) Annual Observation Period. Observations
should be made during the expected high water
table period including both the nongrowing and
growing seasons; the recommended period of
observation will vary regionally. At a minimum
the period should encompass a three month period
during the wettest part of the growing season
and include the month before the start of the
growing season if the wettest part is in the
Spring.
(c) Frequency of Observation. During the
observation periods, the veils should be
observed a minimum of two times per week at a
regular interval not to exceed four days between
observations; for soils with anticipated rapid
fluctuations of the water table (e.g., sandy
soils), a one or two day observation interval is
recommended.
(d) Length of Study. A minimum of three annual
observation periods, each having at least 90% of
average yearly precipitation and at least 90% of
normal monthly distribution. Also, the year
prior to the water table study must have had 90%
of the monthly and annual precipitation. The
observation study may cease after the minimum
consecutive time period required for meeting the
wetland hydrology criterion. (Note; Data from
any year that does not have 90% of average
precipitation cannot be counted toward the
three-year study duration unless it can be
adequately justified in a specific case.)
Precipitation information should be locally
derived (not necessarily site-specific) from the
nearest NOAA-approved weather station or other
available sources of technically valid
information (e.g., university branch stations or
research sites, media weather stations, USGS
stations, state agency stations, etc.). These
precipitation stations must be located within 25
miles of the monitored water table study. If
this is not possible, consult appropriate
regulatory agency for alternatives. Appendix
contains information on the installation of
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ground-water observation wells
5 logy
Jeter
delineating the wetland.
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