A WETLAND EVALUATION METHOD FOR
THE EVERGLADES: IMPACT TO MITIGATION
by Thomas E. Lodge, Ph.D.
Principal Environmental Scientist
Law Environmental, Inc.
Contrary to popular view that persisted through the first half of this century-that
wetlands were wastelands, requiring drainage or other "improvements" in order to be
useful-wetlands are now regarded as being of considerable value to man's direct interests
as well as to natural systems. Wetlands can have numerous and widely differing kinds of
values. The perception of the overall value of a particular wetland depends on the observer
or user's needs and judgment, and no single system or set of standards for assessing values
will satisfy all parties. However, the obvious role now played by wetlands in permitting for
land development, has forced government agencies to explore ways to evaluate wetlands for
the purpose of an equitable and consistent application of modern wetland regulations.
Wetland evaluation is now important both for assessing impacts and for determining
appropriate mitigation. In fact, the much publicized memorandum of agreement (MOA)
between EPA and the Department of the Army states, "In determining compensatory
mitigation, the functional values lost by the resource to be impacted must be considered."
The science of evaluating wetlands in a consistent manner is still young. Perhaps the
most perplexing problem in developing wetland evaluation techniques is the vastly different
importance of particular ecological and/or human-interest functions that wetlands in
different regions may have. This problem makes comparing freshwater wetlands in Ohio
and Florida, for example, a challenging task. Even within a given local area, particular
wetlands may be so different that a fair comparison may not be completely feasible. Tidal
wetlands and interior, isolated freshwater wetlands, for example, may lie within a few tenths
of a mile from one another, but have entirely different functions.
Permitting agencies have avoided many of these wetland evaluation problems by
requiring "kind for kind" mitigation, located in close proximity to the impact site. However,
the widely recognized problem of "postage stamp" mitigation projects-their frequent failure
and the attendant lack of addressing regional ecological requirements-has focused attention
on a wider vision: mitigation banking. Mitigation banking has added to the importance of
more sophisticated wetland evaluation techniques. Mitigation banking alone may justify a
considerable effort in this direction.
Law Environmental, Inc., developed this wetland evaluation procedure specifically
for the freshwater wetlands of Broward County, located on Florida's lower east coast. The
work was done, in part, under a contract with Arvida Company. The approach taken is
quantitative and presents a model for demonstrating how such techniques can be developed
based on regional wetland characteristics.
The particular characteristics of the freshwater wetlands of Broward County were
conducive to such a procedure. Essentially all of the freshwater wetlands of Broward
County are, or were part of the historic Everglades ecosystem. Today, these wetland areas
are either impounded in water conservation areas or are severely impacted by drainage,
infestation by deleterious introduced vegetation, or land use practices. The concern for
possible loss of wetlands in the county due to development is primarily confined to the
degraded wetlands lying east of the levees that delimit the water conservation areas.
It is the origin and general condition of the latter wetlands that has shaped two of
our concerns about permitting procedures as defined by the federal MOA. First, avoidance
and minimization procedures should not be universally employed: steadfast protection of
degraded wetlands does not make sense when mitigation can produce wetlands of much
greater value in many cases. Second, the regional nature of the primary resource, the
Everglades, makes large scale, functionally coordinated wetland mitigation projects much
more appealing than numerous local, small projects. Mitigation banking has an obvious
application for Broward County's freshwater wetlands.
Both of these considerations demanded that a wetland evaluation procedure be
developed that was specific to the characteristics of Everglades wetlands. It was thought
that such a procedure could be used to determine a level of wetland functional value above
which avoidance and minimization would make sense, and below which permitting with
appropriate mitigation would be preferable. The following text is taken from this proposed
methodology. Appendices referenced in the text are not included here.
WETLAND EVALUATION METHODOLOGY
L Evaluation Criteria
Provided here is a general description of the important features of wetland evaluation
that should be required in wetland resource permitting decisions, including the calculation
of adequate compensatory mitigation for wetland impacts. The actual, detailed procedure
is provided in subsequent sections entitled Impact Evaluation, Avoidance and Minimization,
and Mitigation Requirements.
A. Special Wetland Characteristics
We have identified certain conditions or functions of freshwater wetlands in Broward
County for special consideration. These characteristics are considered to be of such high
importance that their presence in a wetland, where impacts are proposed, dictates that
avoidance and minimization procedures must be addressed in the first step of a permitting
procedure. This step precedes the determination of general wetland values, determined in
a wetland quality index procedure described below. The basis for this separate identification
and treatment of special characteristics lies in the fact that they may occur in wetlands that
are not otherwise of high value. The special characteristics include the following:
(a) regular use by threatened or endangered animal species;
(b) regular, annual use by flocks of wading birds for feeding;
(c) colonial nesting by wading birds;
(d) unique wetland resources, defined as significant areas dominated by pond
apple, cypress, and/or southern red maple; and
(e) recreational use (publicly owned lands only).
Each of these special characteristics is defined in more detail in Section III (Impact
B. Wetland quality index (WQI).
A list of 16 criteria has been developed for assessing the functional quality of
freshwater wetland plant communities as they relate to the historic Everglades ecosystem
(see Table 1). The evaluation results in a WQI for each plant community in a specific area
under consideration, and is applied after completion of a map of the general plant
communities on a site. The use' of this technique provides for a uniform, repeatable
approach. The resulting WQI value for each plant community is independent of area, with
the intent being a measure of the relative quality per unit area. A subsequent calculation,
described below, incorporates area to yield a wetland functional value.
While most of the WQI criteria are easily judged by a locally experienced ecologist,
the importance of adequate background hydrological information is made clear. A
reasonable basis for site hydrology must be provided by a qualified hydrologist, either by site
specific studies or by extrapolation from available data. The minimum requirements for
personnel who may determine the WQI for the purpose of wetland resource permitting are
defined (Appendix D).
For proposed mitigation projects, or for impact areas where wetland values can be
reasonably demonstrated or predicted to be changing due to circumstances outside of the
willful control of an applicant, a projected WQI for some future date may be used. Such
projections may not exceed 20 years from the date of the application for a County wetland
resource permit. Changes may be asserted by the applicant or by the County, but must be
supported by documented evidence. Such documentation may be based on observable
trends in vegetation, changed hydrology, etc. While it is anticipated that applicants may
wish to use this provision to assert a lower WQI for wetland impact areas that are expected
to deteriorate in value, there also may be situations where improved wetland hydrology,
eradication of deleterious introduced species, or local mitigation projects, etc., will justify
the extrapolation of an enhanced WQI for a future date.
C. Wetland functional value (WFV).
The functional value of a wetland is calculated from the WQI by multiplying the
WQI by the area, measured in acres. If a site or area of interest has more than one plant
community, this calculation is done for each one. The resulting individual WFV's are then
added together to achieve the total WFV of an area of proposed impact, setting the basis
for "no net loss" of wetland functional values. The amount of compensatory mitigation can
be then similarly calculated from the WQI of the proposed mitigation. The product of the
mitigation WQI and the mitigation acreage must compensate for the total WFV of the
impact (but with consideration of the kind of mitigation, the timing, etc., described below,
under Mitigation Requirements).' Complex mitigation projects (multiple areas having
different WQI) can be evaluated by summing the respective WFV for the various mitigation
areas. The methodology for enhancement and restoration types of mitigation is also
provided, by using the projected difference between WQI values prior to, and after an
D. Evaluation Procedure: Permitting Decision Pathway.
The procedures for obtaining a wetland resource permit begin with impact evaluation
and call for a number of considerations in a stepped procedure. The presence of certain
special characteristics trigger avoidance and minimization procedures, regardless of
associated WQI or WFV. Except for a de minimis WFV for isolated wetlands, a high WQI
also triggers avoidance and minimization procedures. However, for wetlands having lower
WQI values, in the absence of special conditions or functions, only impact evaluation and
compensatory mitigation are considered. The philosophy adopted in this regard is that a
steadfast requirement for avoiding impacts to degraded wetlands (i.e. saving degraded
wetlands) is not in the best interest of the county, and that compensatory mitigation to
produce wetlands of higher quality is the intelligent choice.
II. Data Requirements for Permit Applications
In order to proceed with the wetland resource permitting process, certain data are
required. For conceptual review, the needs are less rigorous, but the whole process should
be understood by an applicant prior to submitting a plan for conceptual review. The data
requirements for conventional permitting are as follows:
A. Wetlands jurisdictional delineation by the County, or by the applicant subject to
concurrence, based on the criteria of Broward County. The delineation is for the
area of concern, hereafter called the site, which is usually the project area or
B. Surveys for: a) threatened and endangered species of animals, referencing current
lists of the U.S. Fish and Wildlife Service and the Florida Game and Fresh Water
Fish Commission and, b) a survey of the site for use by wading birds in colonial
nesting (i.e., rookeries), or extended and regular use by flocks of wading birds in
feeding, referencing seasonal timing of such occurrences. A survey may also be
included, at the discretion of the applicant, for threatened and endangered plants,
relative to current lists of the U.S. Fish and Wildlife Service and the Florida
Department of Agriculture and Consumer Services.
C. A delineation of each of the freshwater wetland plant communities for the entire site,
and a sufficient delineation into the surrounding lands to understand the relationship
of the site to its environs. In cases where reasonably distinct plant community
boundaries do not exist, a description of gradations may be substituted, but it is
important to differentiate between forested and non-forested jurisdictional wetlands,
and to identify the plant communities or land use(s) that border the site.
D. A general assessment of the hydrology of the site, sufficient to address considerations
in the WQI matrix, and to address the value of the site for aquifer recharge, flood
conveyance, and flood storage.
E. A separate WQI for each identified jurisdictional freshwater wetland community,
identified on a plant community map, that lies within the area of impact or proposed
F. A determination of the total WFV for the proposed impact by multiplying the WQI
of each freshwater wetland plant community by its respective area (in acres), and
totalling the results for each freshwater wetland plant community within the area of
impact or proposed impact.
G. The characteristics of any proposed mitigation site, the mitigation approach
(restoration/enhancement, or creation), the calculations for the proposed WQI
benefits to be achieved by the mitigation, and the resulting total WFV to be realized
by the mitigation.
III. Impact Evaluation
This section and the subsequent sections-Avoidance and Minimization Procedures,
and Mitigation Requirements/ Comprehensive Plan Analysis--establish the total allowable
impact to wetland resources for a project in Broward County. The series of steps that follow
define the procedure for making this determination:
Step 1. The applicant should include an appropriate statement in the
application that demonstrates the present and proposed characteristics of the
hydrological conditions at the site, making certain to address (a) aquifer
recharge, (b) flood conveyance and, (c) flood storage. A report by a qualified
hydrological engineer and/or reports from other governmental agencies
having jurisdiction over these functions is the preferred methodology for
compliance. The County will include consideration of potential impacts due
to these factors in the overall proposal. Proceed to Step 2.
Step 2. Are any of the following special characteristics (conditions or
functions) present in the wetland areas) of impact?
(a) Regular use by threatened or endangered animal species; or
(b) Regular, annual use by significant flocks of wading birds for seasonal
(c) Seasonal colonial nesting (see definitions, Appendix A) by birds; or
(d) A unique wetland resource, defined as a swamp dominated by pond
apple (Anona glabra), cypress (Taxodium spp.), or southern red maple
(Acer rubrum), or a mixture of these species, and (i) having a WQI of
greater than 0.35, and (ii) occupying a contiguous area of more than
2 acres; or
(e) Regular recreational use (publicly owned lands only).
Yes: Proceed to avoidance procedures for alternatives to impacts.
Also, review the steps below to determine if the area also
requires these procedures because of a high WQI.
No: Go to Step 3.
Step 3. Is the wetland (or a wetland for projects having multiple wetlands) to be
impacted isolated, that is delineated as separate from all other jurisdictional
Yes: Go to Step 4 for isolated wetlands only.
No: Go to Step 5 for all non-isolated wetlands.
Step 4. Is the total WFV for the areas) of impact more than 0.43?
Yes: Go to Step 5.
No: Stop-no Wetland Resource Permit is required for this small
(de minimis) level of impact. This level is based on a
hypothetical 0.5-acre isolated wetland having the highest
possible rating in every WQI category except protected animal
species use and sheet flow (each rated 0), as the smallest
SStep 5. Is the WQI for any plant community in the area of impact rated 0.70 or
Yes: Proceed to avoidance and minimization and minimization procedures
for alternatives to impacts to plant communities of high wetland
No: Proceed directly to mitigation requirements.
IV. Avoidance and Minimization Procedures (not included in this presentation)
V. Mitigation Requirements
Compensatory mitigation is recognized as a form of avoidance and minimization of
adverse impacts. No practicable alternatives analysis, as that term is defined under the
Section 404(b)(1) Guidelines of the Clean Water Act, is required here. Rather, the permit
review will involve a comprehensive analysis to determine if the application taken as a
whole, and consistent with existing technology, logistics, and costs, achieves a satisfactory
- ecological result.
While the focus of mitigation is for the replacement of ecological values, the final
plan must also accommodate the engineering considerations for aquifer recharge, flood
conveyance, and flood storage. If these factors are being considered in a separate
permitting process by another agency, the County will not include additional requirements
here. However, in the absence of such independent review and permitting, the applicant
will be required to show that the project will not have a significant deleterious affect relative
to these factors.
A. Mitigation Considerations
Wetland losses or projected losses shall be compensated in the wetland resource
permitting process by appropriate compensating mitigation. The considerations to be used
in selection of qualifying mitigation are:
1. Functional replacement: replacement of identified important functions that
are or will be lost as a result of an impact to a wetland. These shall include flood
protection, deleterious hydrologic changes to other wetland areas, and special
requirements of threatened and/or endangered species that have been verified as
using the impact site. Unless a compelling basis can be provided, an historic or
existing herbaceous wetland shall be replaced by an herbaceous type, and an historic
or existing forested wetland shall be replaced by a similar forested type.
2. Location: the benefits of local replacement of functions versus the possible
benefits of remote replaceinent, especially when mitigation banking options are
3. Timing of the completion of the mitigation relative to the impact. Mitigation
timing is described as "in advance" of the impact, "concurrent" with the impact, or
Mitigation in advance means that the mitigation project was constructed, and any
required vegetation has been shown to have met acceptable establishment criteria
of survival and cover prior to the initial impacts of a project. Mitigation in advance
is highly desirable because success can be guaranteed prior to losses by impact. The
use of an existing mitigation bank would qualify in this category of timing.
Concurrent mitigation means that the mitigation project is completed, with any
required vegetation adequately installed during, but not later than the completion
date of a permitted project, according to the schedule established in the wetland
resource permit. It is contemplated that most mitigation projects will be undertaken
concurrently with impact, until such time that appropriate mitigation banks become
After-the-fact mitigation applies: (1) to permitted projects that required wetland
mitigation, but such mitigation was completed after the scheduled completion date
of the project, and (2) to unauthorized wetland impacts, as part of enforcement for
a violation. After-the-fact mitigation will not be considered in the normal course of
wetland resource permitting.
4. Mitigation approach: Restoration or enhancement versus creation. These
forms of mitigation relate to the character of the mitigation site, and to the methods
used in conducting the mitigation.
Restoration or enhancement of former Everglades plant communities are desirable
forms of mitigation for areas of Broward County that lie in the area of the historic
Everglades, but that have been degraded. Restoration applies to cases where the
original wetland had been severely degraded, perhaps to a non-wetland condition,
while enhancement applies to wetlands having endured less impact. The
methodology for determining mitigation credit for restoration or enhancement are
the same, involving the difference in WQI before and after the improvement.
Normally, more credit can be obtained from restoration than from enhancement
because of the lower initial or baseline WQI. However, restoration may entail a
more intensive effort to achieve the desired result.
For an area to qualify for restoration or enhancement, it must not have critical
habitat designation for a threatened or endangered species that would be damaged
by the proposed modificationss. The proposed modifications must be reasonably
projected to achieve a WQI of at least 0.70, based on examples or the application of
recognized scientific principles. If these conditions are met, then it will be accepted
into a wetlands resource permit application as viable compensation for wetlands
Wetland creation is a form of mitigation in which new wetland habitat is constructed
in uplands, or in wetlands that were or will be removed in a land development
process. Created wetland habitat may take various forms. Littoral shelves
constructed around the edges of stormwater lakes are an example. Unlike
restoration or enhancement, wetland creation does not benefit from pre-existing
wetland characteristics of an area, which include in-place wetland soils and (usually)
the existence of naturally occurring wetland vegetation. As a result, adequate soils
and vegetation must be imported and installed. Mitigation credit for created
wetlands is initially based on the final WQI to be realized, and assumes that the
baseline WQI is zero. However, because there is less assurance that creation will
meet the goal of net environmental benefit, the required mitigation credit to
compensate for impact losses are slightly greater than for creation or enhancement
(by a factor of 1.1), unless success is actually demonstrated in advance. Success in
advance can be demonstrated by use of a proven methodology and an historical
pattern of permit compliance, but acceptance so as to justify equality of impact WFV
mitigation credit WFV is left to the reasonable discretion of Broward County.
For creation to be considered as acceptable mitigation for wetland impacts, the final
WQI must be projected to be at least 0.70.
5. Lakes. Lakes created either for the use of extracted material, of for the
purpose of water management, or both, present a special problem. Certainly, lakes
have some aquatic refuge value to adjacent wetlands, as well as value to many
wetland animal species even without adjacent wetlands. By comparison, they have
substantially more value than uplands created for residential or other purposes.
Thus, for the purpose of this regulation, lakes created with adjacent wetlands (e.g.,
littoral shelves), and properly permitted by agencies having jurisdiction over their
construction, will be arbitrarily given a WQI value of 0.20 for their open water area.
Lakes that do not qualify will be given a value of zero, or negotiated on a case-by-
case basis. Littoral shelves with emergent vegetation will be considered as wetlands,
and treated separately in mitigation calculations. This section should be revised as
lake design criteria are developed to give extra credit, for example, for lakes that
receive pretreated stormwater.
6. Ratio requirements for the equivalence of the loss in wetland functional value
due to the impact, and the gain in wetland functional value resulting from the
mitigation, according to the following formula:
R x total WFV loss by impact
= total WFV credit by mitigation
where "R" is the ratio of mitigation credit required, to impact. This value accounts
for the mitigation approach (restoration/enhancement, or creation), the type of
wetland community being replaced (herbaceous, forested with cypress dominant, or
forested with species other than cypress) and the mitigation timing (in advance,
concurrent, or after-the-fact). The R-values are shown in table 2.
A summary of the methodology used to convert wetland impact acreage to required
mitigation acreage involves the following three equations:
1. To convert wetland impact area to WFV of the impact:
wetland impacted WFV
impact x wetland = of
acreage WQI impact
2. To convert WFV of impact to required WFV of mitigation:
WFV WFV of
of x R-value = mitigation
3. To convert required mitigation credit WFV to required mitigation area
WFV of mitigation required
mitigation + WQI = mitigation
required basis acreage
The mitigation WQI basis for restoration/enhancement projects is the difference in
WQI prior to, and after the mitigation improvement. For created wetlands, it is simply the
WQI of the created wetland. An example of this methodology is presented in Table 3.
B. Mitigation Success Criteria
The focus of this document is on the conceptual methodology of determining what
constitutes adequate mitigation for impacts to freshwater wetlands in Broward County.
While the guarantees for success of a mitigation project, after its physical completion, are
as important as the original concept, they were not the thrust of this document.
Various criteria for determining the success of mitigation projects are in place in
state and federal wetlands permitting processes. It should be the policy of Broward County
to impose monitoring and success criteria that agree with the analogous state and federal
permits that may apply to the same or related projects. The County should exhibit flexibility
in this regard, and only impose unique criteria in those instances where specific site
conditions justify such special treatment.
C. Preservation As a Form of Mitigation
Preservation should be considered as a viable form of mitigation for wetlands of high
WQI, or having special characteristics. No specific guidelines are offered here, but the
evaluation process described may be applicable to an overall procedure to be developed in