A Comparison of Three Wetland Evaluation Methods in their

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A Comparison of Three Wetland Evaluation Methods in their A Comparison of Three Wetland Evaluation Methods in their

Assessment of Nontidal Wetlands in the Coastal Plain of Virginia Assessment of Nontidal Wetlands in the Coastal Plain of Virginia

Melissa Claire Chaun College of William and Mary - Virginia Institute of Marine Science

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A COMPARISON OF THREE WETLAND EVALUATION

METHODS IN THEIR ASSESSMENT OF NONTIDAL

WETLANDS IN THE COASTAL PLAIN OF VIRGINIA

A Thesis

Presented to

The Faculty of the School of Marine Science

The College of William and Mary in Virginia

In Partial Fulfillment

Of the Requirements for the Degree of

Master of Arts

by

Melissa Claire Chaun

1995

APPROVAL SHEET

This thesis is submitted in partial fulfillment of the requirements for the degree of

Master of Arts

Melissa C. Chaun

Approved, December 1995

Carlton H. Hershner, Ph.D. Committee Chairman/Advisor

Thomas A. Barnard Jr., MrA.

^*r/James E. Kirkley, Ph.D j

James E. Perry III, Ph.D.

Gene M. Silberhom, Ph.D.

TABLE OF CONTENTS

ACKNOWLEDGEMENTS

LIST OF TABLES ........... iv

LIST OF FIGURES.................................................................................... v

A BSTR A CT.......................................................................................................................... vi

1.0 INTRODUCTION........................................................................................................ 21.1 Importance of Wetland E valuation..................................................................2

1.2.1 Focus on Nontidal W etlands..............................................................41.2.2 Focus on Evaluation Methods of Nontidal W etlands......................41.2.3 Hypothesis .......................................................................................... 6

2.0 LITERATURE REVIEW ...........................................................................................72.1 What are W etlands?..........................................................................................7

2.1.1 Section 404 of the Clean Water Act Amendments (1977) .............72.1.2 United States Fish and Wildlife Service's Wetland Classification

System (1979)...................................................................................... 82.1.3 Food Security Act of 1985 ................................................................82.1.4 Virginia Wetlands Act (1 9 7 2 )........................................................... 9

2.2 Different Perspectives of V alue...................................................................... 102.2.1 Valuing Natural R esources.............................................................. 102.2.2 What is Wetland Evaluation?............................................................10

2.3 Functions of Wetlands ....................................................................................122.3.1 Aquatic/Finfish and Wildlife Habitat: Diversity and Abundance

............................................................................................................. 132.3.2 Nutrient Retention and Transformation.......................................... 142.3.3 Sediment/Toxin Retention................................ 162.3.4 Floodflow Alteration......................................................................... 172.3.5 Groundwater Recharge and Discharge .......................................... 182.3.6 Erosion Control ................................................................................19

2.4 Values of W etlands.......................................................................................... 202.4.1 Recreation, Aesthetics and Heritage Value ................................... 212.4.2 Research/Education Potential ......................................................... 21

2.5 Wetland Evaluation Methods ........................................................................ 222.5.1 Hollands and Magee Method for Assessing the Functions of Wetlands

222.5.2 A Method for Assessing Wetland Characteristics and Values . . . 232.5.3 Habitat Assessment Technique (HAT) ..........................................24

2.5.4 Wetland Evaluation Technique II (WET I I ) ....................................252.5.5 Manual for Assessment of Bottomland Hardwood Functions (WET-

BLH) ..................................................................................................262.5.6 Method for the Evaluation of Inland Wetlands in Connecticut: A

Watershed Approach......................................................................... 272.5.7 Method for the Comparative Evaluation of Nontidal Wetlands in New

Hampshire .........................................................................................272.5.8 A Technique for the Functional Assessment of Nontidal Wetlands in

the Coastal Plain of V irg in ia ............................................................282.5.9 Canada's Wetland Evaluation Guide ...............................................29

3.0 METHODS AND SITE DESCRIPTIONS............................................................... 313.1 Selecting the Evaluation M ethods.................................................................. 313.2 Site Selection................................................................................................... 323.3 Materials ..........................................................................................................343.4 Data A nalysis................................................................................................... 35

3.4.1 Field Component................................................................................353.4.2 Theoretical Component.....................................................................36

4.0 R ESU LTS.......................................................... 50

5.0 DISCUSSION............................................................................................................. 53

6.0 CONCLUSIONS / MANAGEMENT IMPLICATIONS .......................................65

APPENDIX A: FIELD RESU LTS...................................................................................... 70

APPENDIX B: WEIGHTING THE FA CTO RS................................................................ 76

APPENDIX C: COMPARATIVE RANKING OF FACTORS ...................................... 123

APPENDIX D: EXAMPLES OF QUESTIONS / INTERPRETATION KEYS FROMEACH OF THE THREE M ETHODS...........................................129

REFERENCES......................................................................................................................139

VITA 146

ACKNOWLEDGEMENTS

My sincere gratitude and appreciation goes out to all the individuals who have influenced my life and work here at VIMS. First, I am indebted to Dr. Carl Hershner, my advisor and committee chairman, for his guidance, support and infinite patience during the progress of this project. Dr. Hershner provided the idea, but as a true mentor, allowed me to run with it. I would like to thank the rest of my committee, Tom Barnard, Jim Perry, Jim Kirkley and Gene Silberhom, for their input and support. A very special thank you goes to Pamela Mason whose never-ending encouragement helped me through the challenging times. I also wish to extend my gratitude to Julie Bradshaw for her invaluable insight and trust as I critiqued her VIMS Technique!

There are several other individuals I would like to recognize: Michelle Fox, Pamela Mason, Rebecca Smith and Dr. Gerry Johnson, for helping me with field work; Dr. David Evans, for his statistical reinforcement of my data analysis; Ms. Marilyn Lewis, for retrieving all that much needed literature; the trailer crew, Sharon Dewing, Julie Glover and Anna Kenne, for their hours of counsel in exposing me to the fine art of digitizing in ARC/Info, and to everyone in the Wetlands Program, for sharing their knowledge and enthusiasm of this precious resource.

Finally, I want to thank my parents, Hugh and Pamela Chaun, for their unconditional love and support in whatever I do. The greatest recognition, however, goes to God. Without Him, none of this would have been possible.

LIST OF TABLES

Table AO:

Table A21:

Table A22:

Table A23:

Table B3:

Table B3.1:

Table B4:

Table B5:

Table B5.1:

Table B5.2:

Table B6:

Table Cl:

Table C2:

Final Ratings by New Hampshire Method Using Stream Order to Group the Wetland S ites..................................................................................... 45

Summary of Field Results per R ating..........................................................50

Number of Sites that Received Three Identical/Different Ratings 51

Similarity Indices Between 2 Evaluation Methods for All 20 Wetland Sites 51

New Hampshire Method - Ranking of Factors in Floodflow Alteration Ratings............................................................................................................ 44

New Hampshire Method - Sensitivity Analysis of Floodflow Alteration Factors.............................................................................................................43

Wetland Evaluation Technique - Maximum Possible Weight of Factors that can Contribute to a Final Rating of High (H), Moderate (M) or Low (L) for Nutrient Retention and Transformation (modified)....................................47

VIMS Technique - Probability that a Response of High (H), Moderate (M) or Low (L) to a Factor will Yield a Final Rating of High, Moderate or Low for Nutrient Retention and Transformation (modified)....................................40

VIMS Technique - Factors Used in Nutrient Retention and Transformation R atings............................................................................................................ 38

VIMS Technique - Number of High (H), Moderate (M) and Low (L) Responses to Each Factor that Results in a Final Rating of High, Moderate or Low for Nutrient Retention and Transformation.........................................39

New Hampshire Method - Weight and Rank of Factors in Nutrient Retention and Transformation Ratings............................................... 42

Floodflow Alteration - Factors Used by each Method to Evaluate the Function and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L) . . . . 56

Nutrient Retention and Transformation - Factors Used by each Method to Evaluate the Function and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L ) ........................................................................................................... 58

Table C3: Sediment/Toxin Retention - Factors Used by each Method to Evaluate theFunction and their Ranking from Most Influential (1) to Least Influential (4) in Determining a Final Rating of High (H), Moderate (M) or Low (L) . . 60

Table C4: Aquatic/Finfish Habitat - Factors Used by each Method to Evaluate theFunction and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L) . . 63

Table C5: Wildlife Habitat - Factors Used by each Method to Evaluate the Function andtheir Ranking from Most Influential (1) to Least Influential (13) in Determining a Final Rating of High (H), Moderate (M) or Low ( L ) . . . . 54

Table C6: Similarity Indices Between 2 Evaluation Methods in the Type of Information(Factors) Used to Evaluate the 5 Functions................................................ 55

Table C7: Similarity Indices Between 2 Evaluation Methods in the Ranking of theFactors Used to Evaluate the 5 Functions................................................ 55

Table Dl: Landscape Management Information - Floodflow Alteration.................... 68

Table D2: Landscape Management Information - Nutrient Retention/Transformation . 68

Table D3: Landscape Management Information - Sediment/Toxin Retention 68

Table D4: Landscape Management Information - Aquatic/Finfish Habitat..................69

Table D5: Landscape Management Information - Wildlife Habitat..............................69

LIST OF FIGURES

Figure 1: Location of Wetland Sites in the York River Basin, Virginia..................... 33

v

ABSTRACT

Three wetland evaluation methods were compared to determine whether they were interpreting the wetland science in the same way. The methods used were: 1) Wetland Evaluation Technique (WET II), 2) A Technique for the Functional Assessment of Nontidal Wetlands in the Coastal Plain of Virginia (VIMS Technique); and, 3) Method for the Comparative Evaluation of Nontidal Wetlands in New Hampshire (New Hampshire Method). Twenty nontidal wetlands in the coastal plain of Virginia were evaluated by all three methods to see whether the methods gave the same ratings for the same wetland. Each method uses a unique qualitative evaluation/interpretation scheme, and thereby incorporates an element of professional judgment, to predict either a high, moderate or low probability that a particular wetland will perform a certain function. Although the methods vary in the number of functions/values they assess, there are five functions/values common to all: floodflow alteration, nutrient retention and transformation, sediment/toxin retention, wildlife habitat and aquatic habitat. The interpretation key for each of the five functions/values was scrutinized individually for the types of information required to evaluate the function and how that information was used to obtain the final rating for the function. It was hypothesized that all three methods would give similar ratings for the same wetland since all three claim to be scientifically defensible, based on the current scientific literature. The field results, however, reveal differences among the three methods in their assessment of each wetland. Furthermore, from the "sensitivity" analyses performed on the interpretation keys, it appears as though the wetland science is not being interpreted identically by all three methods. This comparative study demonstrates that the process by which science is interpreted and incorporated into a practical planning/management tool is anything but straightforward.

vi

A COMPARISON OF THREE WETLAND EVALUATION

METHODS IN THEIR ASSESSMENT OF NONTIDAL

WETLANDS IN THE COASTAL PLAIN OF VIRGINIA

1.0 INTRODUCTION

1.1 Importance of Wetland Evaluation

Wetlands of the United States can be divided into two principal classes according to water

regime: tidal and nontidal wetlands. The coastal plain of Virginia is the relatively flat land

east of U.S. Route 95 and influenced by the Chesapeake Bay and its tributaries. Virginia

comprises approximately 26.1 million acres, of which there are 387,300 acres (1.48%) of

coastal tidal wetlands (Field, Reyer, Genovese, and Shearer, 1991). Tidal wetlands generally

refer to coastal marshes, mudflats and mangrove swamps that are subjected to periodic

flooding by ocean-driven tides (Burke, Meyers, Tiner and Groman, 1988).

Nontidal coastal v/etlands in Virginia comprise some 525,700 acres (2.01% of Virginia) (Field

et al., 1991). Nontidal wetlands represent a diverse range of wet inland environments. They

consist of freshwater marshes and ponds, shrub swamps, bottomland hardwood forests,

wooded swamps and bogs, as well as inland saline and alkaline marshes and ponds (Burke et

a l , 1988). They are typically created by a combination of surface-water flooding or ponding,

and groundwater discharge. They therefore form along nontidal rivers, streams, lakes and

ponds; in isolated upland depressions where surface water accumulates; in conjunction with

springs and seeps (areas of active groundwater discharge); and where the water table remains

near the surface for some time. In such areas the soil becomes saturated to form hydric soils,

and plants, known as hydrophytes, adapted for life in wet, predominantly anaerobic conditions

become established to form nontidal wetlands (Burke et al., 1988). The formation of

anaerobic conditions following the onset of flooding or saturation depends upon such factors

as soil type, amount of organic material in the soils, soil temperature, and the chemical oxygen

demand of the reducing ions. The low oxygen availability reduces, or in many plant species

inhibits, metabolic activities of the roots and affects nutrient uptake and mobilization. These

conditions also result in the accumulation of reduced forms of iron, manganese, sulphur and

carbon to levels that are toxic to most plants (Coburn, 1993).

2

The evaluation of wetlands has occupied the interests of both scientists and politicians, with

resource managers playing the key liaison. Where wetlands were once valued primarily as

habitat for wildlife, particularly migratory birds, the legal basis for present day wetland

regulation is the recognition that these landscape units have ecological functions of

importance to public health, safety and welfare (Larson, 1990), as well as to the surrounding

environment. Human threats to wetlands include draining, dredging, filling, construction of

shoreline structures, groundwater withdrawal and impoundments. From 1956 to 1977,

Virginia lost over 63,000 acres of tidal wetlands and nontidal vegetated wetlands,

representing almost 7% of the state's total wetlands acreage (Tiner, 1987). Direct conversion

of wetlands to cropland was the major cause of inland wetland loss. Coastal wetland loss was

primarily due to urban development and coastal water impoundments (ibid).

Early efforts at wetland evaluation focussed on estimates of the dollar value of the wildlife

product or of the number of days of recreational use (Larson, 1990). Since the early 1970's,

numerous wetlands evaluation methods have been developed as a management tool in the on

going conflict between conservation goals and development pressures. Methods have been

designed by federal/state agencies, private consulting firms, and the academic community to

ascertain all known wetland functions and values, or a selected few. They have been created

to produce a verifiable and reproducible outcome which can be applied in a number of ways:

comparison of two or more wetlands; prioritization of wetlands for acquisition, research or

advanced identification; enumeration of possible permit conditions; prediction of project

impacts on wetland functions and values; and, comparison of created or restored wetlands

with reference or pre-impact wetlands for mitigation purposes (Adamus, Stockwell, Clairain,

Smith and Young, 1987).

3

1.2 Purpose of Study

1.2.1 Focus on Nontidal Wetlands

Concern for wetlands began with the goal of preserving tidal wetlands. These systems were

first recognized to be important for providing valuable fisheries and wildlife habitat,

contributing significant amounts of primary production to the aquatic environment and

maintaining shoreline stability. The importance of the fin- and shellfish industries, and the

general acceptance of these functional roles of tidal wetlands have convinced most coastal

states and communities that wetlands are valuable fish nurseries. Protection of these

functions, therefore, was the objective of the first wetlands legislation (Larson, 1990).

Although nontidal wetlands comprise approximately 95 percent of all wetlands in the

coterminous U.S. (Burke, Meyers, Tiner, and Groman, 1988), concern for this class of

wetlands is a more recent issue. This may be due to two factors. First, the attention given

to tidal wetlands may have overshadowed nontidal wetlands as a less important class of

wetlands. Second, due to private property implications, it may be more difficult to convince

the public, especially the agricultural sector, of the functions and values of these systems. The

present study focuses on nontidal wetlands because less research has been devoted to them.

In many states such as Virginia, nontidal wetlands still await significant protection by state

legislation (Odum, 1988).

1.2.2 Focus on Evaluation Methods o f Nontidal Wetlands

This study critiques three evaluation methods in their assessment of nontidal wetlands. Over

the past two decades, more than two dozen wetlands evaluation methods have been designed,

but little attempt has been made to evaluate the progress in designing these methods. The

knowledge-base concerning wetland functions and values has been steadily increasing over

time; however, our understanding of whether such evaluation methods are able to accurately

and consistently determine wetland functions and values, and how these methods actually

4

accomplish their objectives, appears to be lacking.

The accuracy of wetland evaluation methods can be examined by comparing the results from

these formal methods with more in-depth, site-specific numerical data from the same wetland

sites, as was done in a study by Eargle (1989). Eargle examined the accuracy (and

reproducibility) of the WET II Technique on three different wetland types in South Carolina.

However, quantitative studies on Virginia's nontidal wetlands are scarce and often do not

contain the specific data needed to quantify functions. Consequently, determining the

accuracy of these methods could not be addressed in the present study.

The precision or consistency (reproducibility) of wetland evaluation methods can be

addressed if numerous evaluators with similar backgrounds and experience were to evaluate

the same wetland sites using the same evaluation methods. (It has been observed that

following a one-week training course in WET II, however, variability of values assigned by

different evaluators is very low (Coburn, 1993).) Although feasible, this issue would require

significant effort and input by several individuals.

The present study therefore addressed the third issue: determining how nontidal wetlands

evaluation methods accomplish their objectives. It is assumed that the interpretation of the

wetland science into formal evaluation methods is consistent; that is, that best professional

judgment in the field of wetlands science is universal. In addition, some wetland professionals

claim to examine a broad range of factors when evaluating a site in the field. By critiquing

three methods of comparable age (1986-1991) to discern how they accomplish their

objectives, not only will the degree of universality in wetland science interpretation be

determined, but also it may be revealed that few factors are actually necessary in the

evaluation of a function. If that is the case, then wetland evaluation methods could be further

refined.

5

The study had a two-fold objective: 1) to determine whether wetland evaluation methods

interpret the wetland science in the same way, and 2) as a practical application, to identify

whether these qualitative assessment data may be organized into useful landscape

management information.

1.2.3 Hypothesis

It was hypothesized that all three evaluation methods would give very similar final ratings for

the functions assessed at each wetland site because they share three fundamental

characteristics. Each method uses a unique qualitative evaluation/interpretation scheme, and

thereby incorporates an element of professional judgment, to predict either a high, moderate

or low probability that a particular wetland will perform a certain function. The methods,

therefore, are intended to precede, not replace, site-specific quantitative studies or

assessments. All the authors recommend that the final evaluations remain qualitative; that the

evaluator does not attempt to assign discrete numbers to the high, moderate or low ratings.

Secondly, these qualitative methods are designed essentially to compare two or more

wetlands. They can be used as a management tool to "red-flag" a wetland that may be

providing a valuable, if not critical, function and/or value to the surrounding landscape.

Lastly, each method claims to be scientifically defensible and therefore based upon accepted

wetland science. It was presumed that if all three methods assess the same function, they will

require a similar input of data to adequately evaluate the function qualitatively. In addition,

it was anticipated that each method would be very similar at the finer scale of data

interpretation. They would assign comparable weights (degrees of influence) to each factor

(type of information) they had in common, again, because they are assumed to use the same

universally accepted wetland science.

6

2.0 LITERATURE REVIEW

2.1 What are Wetlands?

Wetlands are transitional systems between terrestrial and aquatic habitats. They are

components of the landscape where the permanent or temporary presence of water acts

together with the soils to determine the type of vegetation. Hence, hydrology, vegetation and

soil composition are the primary criteria used in the identification of a wetland. The presence

of at least one wetland indicator from each of the three parameters is usually required to make

a positive wetland identification. Sometimes however, rooted plants may be absent and in

some cases the substrate may consist of rocks instead of soil. Several definitions have been

developed at the federal and state levels to define "wetland" for various laws, regulations and

programs. Four definitions are cited for comparison.

2.1.1 Section 404 o f the Clean Water Act Amendments (1977)

Section 404 of the Clean Water Act (CWA) requires a permit to be issued for any dredge or

fill activity in waters of the United States including wetlands. The following is the regulatory

definition of wetlands used by the United States Environmental Protection Agency (EPA) and

U.S. Army Corps of Engineers (COE) for administering the Section 404 Permit Program:

[Wetlands are] 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 o f vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

Functional assessment is critical to the Section 404 program since most decisions revolve

around an assessment of wetland functions (Ainslie, 1994).

7

2.1.2 United States Fish and Wildlife Service's Wetland Classification System (1979)

The Fish and Wildlife Service (FWS), in cooperation with other federal agencies, state

agencies and private organizations and individuals, created a wetland definition for conducting

an inventory of the nation's wetlands. This definition was published in the FWS's volume

"Classification of Wetlands and Deepwater Habitats of the United States" (Cowardin, Carter,

Golet and LaRoe, 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 o f this classification wetlands must have one or more o f the following three attributes: (1) at least periodically, the land supports predominantlyhydrophytes, (2) the substrate is predominantly undrained hydric soil, and (3) the substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season o f each year.

2.1.3 Food Security Act o f 1985

This definition is used by the U.S. Department of Agriculture, Natural Resource Conservation

Service (NRCS), for identifying wetlands on agricultural land in assessing farmer eligibility

for the department's program benefits under the "Swampbuster" provision of this Act (PL 99-

198):

Wetlands are defined as areas that have a predominance o f 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 o f hydrophytic vegetation typically adapted for life in saturated soil conditions, except lands in Alaska identified as having a high potential fo r agricultural development and a predominance o f permafrost soils.*

* Special note: The Emergency Wetlands Resources Act of 1986 also contains this definition, but without the exception for Alaska.

The "Swampbuster" provision denies federal price supports, payments, certain loans and other

benefits to farmers who convert wetlands for agricultural purposes (Subtitle B of the FSA).

8

2.1.4 Virginia Wetlands Act (1972)

The Commonwealth of Virginia adopted the Virginia Wetlands Act (§28.2-1300, Va Code

Ann.) in 1972 to establish standards and guidelines for tidal wetlands, thereby legally

segregating tidal and nontidal wetlands in Virginia (Coburn, 1993). Nontidal wetlands are

as yet unprotected by state law. However, Virginia is presently developing a program to

regulate uses of nontidal freshwater wetlands and to meet Past-Govemor Wilder's stated goal

of no net loss of nontidal wetlands values. This will be effected primarily through

enhancement of Section 401 Certification of the Clean Water Act Amendments (Cobum,

1993).

To date, therefore, the Virginia Wetlands Act defines wetlands to mean only vegetated and

non vegetated tidal wetlands:

"Vegetated wetlands" means lands lying between and contiguous to mean low water and an elevation above mean low water equal to the factor one and one-half times the mean tide range at the site o f the proposed project in the county, city, or town in question, and upon which is growing any o f the following species: saltmarsh cord grass (Spartina altemiflora). saltmeadow hay fSpartina patens), saltgrass fDistichlis spicata).../~32 species, including saline, brackish and freshwater varieties!...reed grass fPhragmites communis). or switch grass fPanicum virgatum).

"Nonvegetated wetlands" means unvegetated lands lying contiguous to mean low water and between mean low water and mean high water, including those unvegetated areas o f Back Bay and its tributaries and the North Landing River and its tributaries subject to flooding by normal and wind tides but not hurricane or tropical storm tides.

The EPA, COE and NRCS wetland definitions include only areas that are vegetated under

normal circumstances, while the definitions used by the FWS and Virginia Wetlands Act

recognize both vegetated and nonvegetated areas. The first three wetland definitions are

conceptually the same; they all incorporate three basic elements — hydrology, vegetation and

soils — for identifying wetlands.

9

2.2 Different Perspectives of Value

2.2.1 Valuing Natural Resources

An ecosystem may be valued for several practical reasons: 1) gauging the feasibility of broad

policy goals, such as "no-net-loss of wetlands" or the merits of protecting fisheries habitat;

2) computing the losses resulting from damage to habitats from hazardous wastes, oil spills,

development, or other impacts; 3) determining project priorities in environmental restoration;

4) assessing property values and engaging in wetland mitigation banking; and, 5) analyzing

regulatory impacts (NOAA Chesapeake Bay Environmental Valuation Workshop, 1994). A

fundamental distinction between the way economists and other disciplines use value is the

economist's emphasis on human preferences. Nonpreference-related "values" are

mathematical and functional. In the mathematical sense, value means magnitude. In the

functional sense, value refers to the biological or physical relationships of one entity to

another. For example, wetlands can be valued as water filtration/purification systems, as

spawning habitat for fish, or for the nutritional value of omega-3 fatty acids. These exist

whether or not humans prefer them or are even aware of them (NOAA Chesapeake Bay

Environmental Valuation Workshop, 1994).

2.2.2 What is Wetland Evaluation ?

Wetland evaluation can be considered as two operations: the scientific process of functional

assessment in which the biological, chemical, geological and physical characteristics of a

wetland are determined; and, the socio-economic process of assigning values to the wetland

by defining those characteristics that are beneficial to society (Larson and Mazzarese, 1992).

For example, functional assessment typically focusses on the probability a wetland is

important for hydrologic processes such as flood control, shoreline stability and water quality

maintenance. To determine its ability to purify water, the assessment may therefore examine

the wetland's capability of retaining nutrients, toxins and/or trapping sediments. However,

many assessment methods also consider the wetland's importance as a habitat for aquatic and

10

terrestrial species. The socio-economic evaluation of wetlands considers the habitat

significance of a wetland, but it examines that feature as it pertains to human values. For

example, this type of evaluation often considers the active and passive recreational values of

a wetland. Game hunting and fishing constitute active recreational activities; bird watching

and aesthetic/spiritual enjoyment are considered passive ones. Moreover, a particular wetland

may be highly valued by society if it is utilized by an endangered species. The potential of a

wetland to serve as an educational/research site is also often weighed in this type of

evaluation.

Some methods focus on functional assessment; others take a more comprehensive approach

and incorporate both the functional assessment and socio-economic evaluation of a wetland.

Recently, producers of assessment/evaluation methods have aimed at generating relatively

simple techniques, enabling a preliminary assessment/evaluation to be conducted within a

minimal time period. Such techniques are intended to precede, not replace, lengthier scientific

inventories (Abate, 1992). They are a means of quickly assessing those wetlands which may

require further examination as they appear to be particularly important for one or several

functions and/or values. The methods are therefore capable of "red-flagging" a wetland, as

well as comparing several wetlands within a watershed or other landscape unit.

It is now recognized that not all wetlands perform all known functions, and not all functions

are performed equally by each wetland. The specific biological, chemical, geological and

physical features of each wetland determine how the wetland will function. It is therefore

difficult to determine the functions a wetland performs without site-specific analysis.

Detailed, scientific studies of a wetland are necessary to quantify the functions of a wetland.

However, general descriptions and measurements of these features, as obtained from these

assessment/evaluation methods, can help predict which functions may be present in a specific

wetland (Larson, Adamus and Clairain, 1989). Nevertheless, there is the need for an accurate

and sophisticated assessment method to support long-term management and policy

development (Hershner, 1993).

11

Apart from being a component of many wetlands assessment techniques, the socio-economic

evaluation of wetlands also has its own field in the domain of economics. Methods include

both market and nonmarket strategies. Some believe that a wetland evaluation must

incorporate both ecology and economics in a common framework to produce accurate, robust

value information (Amacher, Brazee, Bulkley and Moll, 1988). The short-term economic

gains acquired through wetlands destruction can be ascertained; therefore, development is

perceived to be of net benefit to society (Coburn, 1993). Furthermore, the laws of

margination continue to apply. As we deplete wetlands, the value of the goods and services

of that resource will increase. However, the long-term economic and environmental costs of

wetland destruction may well outweigh the short-term gains. To date, a handful of economic

evaluation methods do exist, but none have proved satisfactory in their application to

wetlands.

2.3 Functions of Wetlands

Ecological processes are generally described by function, such as nutrient retention and

transformation or wildlife diversity and abundance. Function is an ecological process that

may not directly benefit humanity. The further classification of a function by its value

connotes usefulness to humanity. However, these terms are often used interchangeably

because functions may also be values. The location of a wetland within the landscape (i.e.

proximity to human development) may determine the value of a functional ecologic process

(Mitsch and Gosselink, 1993). A wetland may play an active role in the hydrologic cycle of

its watershed, but may be regarded as highly valuable if human development exists

downstream and the wetland can dissipate flood waters. If the wetland is located downstream

from a pollution source, it may have the opportunity to act as a water filtration system, thus

purifying the inflowing water before it reaches downstream environments, whether they be

potable water reservoirs, groundwater aquifers, agricultural lands or pristine wilderness.

12

Assessment/evaluation methods may vary not only in the functions they choose to assess, but

also in how they categorize these functions. The principal functions most prevalent in these

methods are described below.

2.3.1 Aquatic/Finfish and Wildlife Habitat: Diversity and Abundance

Wetlands provide habitat for numerous species of birds, mammals, reptiles, amphibians, fish,

shellfish and insects (Marble, 1992). Moreover, of the nation's endangered and threatened

species, 50 percent of the animals and 28 percent of the plants rely on wetlands for their

survival (Niering, 1988). This function refers to the support of diverse and/or abundant

invertebrates and vertebrates via activities such as herbivory, predation and bioturbation

(Brinson, 1993). In addition, a wetland may support migratory and ephemeral species that

use the resource only periodically for such specific life stages as breeding, migration, molting

and over-wintering (Marble, 1992). Many bird species depend on wetland habitat.

Predacious birds such as hawks, bald eagles, ospreys and owls feed and nest in wetlands.

Wetland seeds and tubers provide crucial winter food for waterfowl such as ducks and geese

(Weller, 1979). Bottomland forested wetlands are primary wintering grounds for waterfowl

and important breeding areas for wood ducks, herons, egrets and wild turkeys (Tiner, 1984).

Furthermore, during the autumn season when uplands lose most of their wildlife habitat value,

bottomland hardwood wetlands are entering a new productivity phase by releasing mast

(Harris and Gosselink, 1990).

Wetlands can be used by fish species as feeding, spawning and nursery grounds. While this

function is well defined for coastal estuaries and associated wetlands, little is known about

the role of nontidal wetlands in support of fisheries. Nonetheless, common fish species that

utilize freshwater wetlands include pickerel, sunfish, bass, crappie, bullhead, carp, herring,

white perch and American shad (Mitsch and Gosselink, 1993).

13

A wetland's ability to fulfill this function depends upon the type and quality of habitat it

possesses. Critical habitat factors affecting terrestrial and aquatic diversity and abundance

include: location and size of wetland, accessibility, adjacent forest acreage, watershed size,

vegetation composition and canopy structure, the interspersion of vegetation and water, water

quality, pH, salinity, temperature, substrate composition, water depth and velocity, and degree

of human disturbance. For example, wetlands having large watersheds may be more valuable

as wildlife habitat because they are likely to be sustained hydrologically throughout time, and

are also richer in nutrients than those with smaller watersheds (Marble, 1992).

Since needs vary from species to species, the more diverse a wetland's attributes, the more

likely it will be able to sustain a diversity of species. Vertical layering and horizontal overlap

of several vegetation classes, such as forested, scrub/shrub, emergent and algal, support a

greater diversity of wildlife species than a wetland with a less complex vegetative structure.

Complex foliage height diversity, for example, increases the number of niches available for

feeding, protective cover and shading. Moreover, although diversity and abundance are

different conceptually, they are known to be highly correlated with one another (Marble,

1992).

2.3.2 Nutrient Retention and Transformation

This function refers to the retention of nutrients, the transformation of inorganic compounds

to their organic forms, and the transformation of nitrogen into its gaseous form. Wetlands

in systems with flowing waters are generally more productive than those with stagnant waters

due to the continuous influx of nutrients (Coburn, 1993). Wetlands receive water from

precipitation, surface runoff, directly (flooding) and indirectly (percolation) from streams and

lakes, groundwater and as wastewater discharges. Water may leave wetlands as surface water

outflows, groundwater, evaporation, evapotranspiration or pumping (Coburn, 1993).

Wetlands can maintain water quality by removing nutrients from both the water column and

sediments during the growing season, via uptake and storage by wetland vegetation. In

14

addition, some nutrients may adhere to sediment particles. Vegetation can reduce water

velocity via frictional resistance, which in turn enhances sedimentation out of the water

column. Nutrient burial below the zone of biological activity is thus increased (Marble,

1992). The age of the wetland vegetation is also important. Unlike the early stages of

succession where accumulating biomass retains nutrients such as phosphorus, mature

successional stages recycle vegetative phosphorus and do not remove it from the sediments

or water (Cobum, 1993).

Soil composition is also an important factor. Phosphorus is readily immobilized by aluminum,

calcium and iron via adsorption and precipitation reactions. Since fine mineral soils typically

possess higher concentrations of these ions, they usually have a greater capacity to retain

phosphoms than organic soils (Marble, 1992).

Studies have shown that wetlands can act as sinks for nitrogen and phosphoms under both

nutrient enriched and natural conditions. Wetlands can therefore function as nutrient traps

for urban and agricultural runoff which tend to contain significant concentrations of dissolved

nitrogen and phosphorus. In an average stream, both total nitrogen and total phosphoms

concentrations are roughly 9 times higher when the watershed is > 90% farmed as compared

with > 90% forested watersheds (Omernik, 1977). Mitsch, Dorge and Wiemhoff (1979)

found a riverine swamp to be acting as a sink for phosphoms. The net phosphoms input by

floodwaters to the swamp was over 10 times greater than the outflow of phosphoms to the

river. Boyt, Bayley and Zoltek (1976) studied a hardwood swamp that had been receiving

sewage effluent for 20 years and found a 98 percent reduction in total phosphoms and a 90

percent reduction in total nitrogen in the outflow waters. These percentages are comparable

to those achieved by advanced treatment of wastewater (i.e. coagulation-sedimentation and

nitrification-denitrification).

Nutrient retention and transformation improves with retention time and low nutrient loading

rates. Retention time increases with hydroperiod, (permanently flooded or saturated

15

conditions), lower slopes, dense vegetation (weaker water velocities), and constricted or non

existent outlets (Marble, 1992).

2.3.3 Sediment/Toxin Retention

Sediment/toxin retention is similar to the nutrient retention and transformation function.

Sediments often contain chemically and physically attached nutrients and contaminants such

as heavy metals, pesticides, herbicides and other organic toxins. Sediments and associated

toxins are transported by runoff or channel flow into wetlands where they can be removed by

several processes. Compounds can be removed from the water column via sediment

deposition and burial, chemical breakdown, and/or assimilation by organisms. Several studies

have shown wetlands to be effective filtration mechanisms and thus can behave as natural

wastewater and stormwater treatment systems. Riparian areas have been shown to retain 80

percent of sediment runoff from adjacent agricultural lands (Richardson, 1989). Freshwater

wetlands filter 60 to 90 percent of suspended solids from wastewater (Richardson, 1989).

The Commonwealth's Best Management Practices (BMP) Manual for urban areas suggests

using wetland vegetation for the natural biological treatment of stormwater. Wetland plants

can provide the following water treatment operations: 1) break down phenols to amino acids,

2) destroy cyanide groups, 3) consume nitrates and phosphates from untreated stormwater,

4) neutralize extreme pH conditions, 5) reduce chemical oxygen demand; and, 6) increase the

dissolved oxygen demand content of water (Virginia State Water Control Board, 1979b).

As with nutrient retention and transformation, detention of sediments and toxins improves

with retention time. Deposition of upland-eroded sediment appears to be greatest in riparian

areas bordering first-order streams. The larger flow volumes of the higher order streams

probably allow less chance for sediment deposition (Lowrance, Sharpe and Sheridan, 1986;

Cooper, Gilliam, Daniels and Robarge, 1987). In addition, the fetch/exposure of a particular

wetland can determine whether it provides this function. Sheltered areas are less prone to

wind mixing which enhances suspension and transport of sediments out of the wetland.

16

Shallow water wetlands offer greater frictional resistance to flow, and in turn, favour

sedimentation of suspended solids. Apart from providing frictional resistance, vegetation

encourages the retention of materials by reducing the resuspension of bottom sediments from

wind mixing, by lengthening the flow path of water through the wetland, and by contributing

to the organic content of the bottom sediments which in turn helps to retain toxins associated

with sediments (Marble, 1992).

Such factors determine whether a wetland will be effective at performing the function of

sediment/toxin retention. Wetlands that receive runoff from watersheds with erosion-prone

areas or contaminant sources, are most likely to have the opportunity to function as sediment

and toxin removers. As will be shown later, some evaluation techniques choose to keep these

two concepts separate.

2.3.4 Floodflow Alteration

Floodflow alteration is the process by which peak flows from runoff, surface flow and

precipitation are delayed or stored. Depending upon its position within the watershed, a

wetland can detain flood waters by intercepting sheet flow, thereby reducing flood peaks. By

reducing flood peaks, wetlands can abate flood-related damage (Marble, 1992). Wetlands

can store or remove water in several ways. While water storage capacity varies according to

wetland size, water depth, degree of constriction and soil properties, the processes of uptake

and evapotranspiration vary depending upon type and extent of vegetation. Open water

bodies engage in surface evaporation. In addition, vegetated wetlands usually contain large

quantities of litterfall that act as a sponge, and if not already saturated, can release water very

slowly (Cobum, 1993).

Flood control has become evermore important in urban areas where the rate and volume of

stormwater runoff have increased with impervious surfaces, such as roads, parking lots and

buildings (Wohlgemuth, 1993). Even in the early 1970's, the U.S. Army Corps of Engineers

17

found that protection of 3,400 ha of natural wetland systems along the Charles River in

Massachusetts was the most cost-effective solution to controlling flood waters. The report

presented a novel attitude to flood control for Congressional consideration. All the proposed

expenditures were not to build but to preserve (U.S. Army Corps, 1972; Carter, Bedinger,

Novitzki and Wilen, 1979).

From a more non-human perspective, a wetland capable of surface water storage also

provides maintenance of water on site for vegetation and wildlife. Inputs from the watershed

during flooding include not only water, but also particulate and dissolved organic matter, as

well as nutrients (Cobum, 1993). Consequently, a wetland can improve downstream and/or

groundwater quality (Brinson, 1993). Such phenomena demonstrate that most wetland

functions are not independent of one another (Larson, Adamus and Clairain, 1989).

2.3.5 Groundwater Recharge and Discharge

By holding surface water long enough to enable the water to percolate into the underlying

sediments and/or bedrock aquifers, a wetland is capable of recharging groundwater. To

recharge groundwater, the water source of the wetland must be surface water i.e. channel

flow or overland flow (Marble, 1992). Recharge potential varies according to wetland type,

geographic location, season, permeability of underlying soil strata, water table location and

precipitation (Tiner, 1984).

A wetland is more likely to recharge groundwater if, for example, it is located in a watershed

dominated by soils with slow infiltration rates because the volume of runoff entering the

wetland will be significant. A wetland underlain by permeable soils and materials with high

infiltration rates is also more likely to recharge groundwater. The longer the detention time

of the water in the wetland, the greater the opportunity for the water to percolate into the

underlying substrate. A constricted or non-existent outlet usually creates a hydraulic gradient

favouring groundwater recharge. Moreover, such conditions typically result in a wetland

18

possessing fluctuating water levels, which will periodically inundate adjacent unsaturated

soils. Seasonally or temporarily flooded soils are more likely to transmit water than saturated

soils (Marble, 1992).

While wetlands positioned above the local groundwater table may have the ability to recharge

groundwater, wetlands in direct contact with saturated zones can serve as discharge areas for

groundwater. Such wetlands are located where permeable rocks intersect at the surface

(Novitzki, 1989). Factors affecting discharge of groundwater into wetlands include: location

and hydrological characteristics of aquifers, soil types and profiles in conjunction with

topography, and seasons (Coburn, 1993). Whether a wetland serves as a groundwater

recharge or discharge site therefore primarily depends upon its position relative to the water

table (Cobum, 1993).

Issues of public interest concerning groundwater sources that influence wetlands include

contamination, raising or lowering of local water tables by impounding, irrigation or pumping

for municipal, industrial or agricultural water supplies, and paving formerly pervious surfaces

(Brooks, 1989). At least 60 municipalities in Massachusetts have public wells in or very near

wetlands (Motts and Heeley, 1973), and freshwater wetlands have been observed to be

important potential recharge reservoirs to the groundwater aquifer that supplies potable water

on Hilton Head Island, South Carolina (May, 1989).

2.3.6 Erosion Control

The movement of water generated by winds, storms and river currents can cause substantial

erosion of coastlines and shorelines. Tidal wetlands can contribute to shoreline stability; in

the same way, nontidal wetlands can function as a protective fringe along the shores of rivers,

lakes and reservoirs by helping to dissipate the kinetic energy of moving water. Emergent

vegetation can reduce erosive and destabilizing forces along banks by slowing water velocity

via frictional resistance and by anchoring soil with their dense root masses. Trees and shrubs

19

along riparian zones can help buffer alluvial floodplain sediments from the erosive power of

a flooding river (Brooks, 1989). Hence, the Virginia Erosion and Sediment Control

Handbook recognizes the use of wetland vegetation in stabilizing streambanks (Virginia

Department of Conservation and Recreation, 1992).

Factors involved in erosion control and substrate stabilization include: waterbody type,

energy of the water, type and location of wetland vegetation, erodibility of the soils, type and

amounts of suspended materials in the water, and season of the year (Coburn, 1993).

2.4 Values of Wetlands

Functions and values of wetlands are not two distinct concepts. The six functions just

described are all valuable to humanity in one way or another. The authors of an evaluation

method designed in Connecticut, for example, use the term "functional values" to refer to all

the functions and/or values assessed. However, there are those who prefer to differentiate

between the two, despite their association from the human perspective. Functions are those

abiotic and biotic processes that a wetland performs within its physical landscape. Values are

less tangible than functions. They are those attributes of a wetland which directly or indirectly

provide an investment or worth to humanity; that is, value is an anthropocentric term.

Wetland values may change as our perception and technology change even though the

functions of wetlands remain the same (Harris and Gosselink, 1990). As previously

mentioned, wetland evaluation can be considered as two operations: the scientific process

of functional assessment in which the biological, chemical, geological and physical

characteristics of a wetland are identified; and, the socio-economic process of assigning

values to the wetland by defining those characteristics that are beneficial to society (Larson

and Mazzarese, 1992).

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2.4.1 Recreation, Aesthetics and Heritage Value

Many recreational activities involve water. Although deepwater habitats are primarily used

for water-dependent recreation such as swimming and boating, vegetated wetlands can attract

hunters, trappers, anglers, birders, hikers and nature-lovers of all kinds. The dynamic nature

of the wetland ecosystem has fascinated the human mind, and many artists, photographers,

authors and musicians have been inspired by these environments (Brooks, 1989).

Recreational activity can often be translated into economic value by determining the amount

of money spent on license and admission fees, travel, accommodation, food, the purchase and

rental of equipment, and the purchase of art, crafts and various kinds of literature (Brooks,

1989).

Although more difficult to quantify, aesthetic and heritage values are often recognized. A

wetland located within an urban landscape may be more highly valued (and enjoyed) for its

intrinsic qualities than one surrounded by other wetlands and/or a more pristine environment.

A wetland may provide habitat for unusual and rare flora and fauna, (e.g. insectivorous plants

and bog turtles), contribute to the regional landscape scenes familiar to and appreciated by

travellers (e.g. riverine wetlands along the Susquehanna River and peat bogs of the Poconos),

or be a part of the local, cultural history (e.g. archaeological significance of the forested

wetlands of Virginia's Colonial National Historical Park) (Brooks, 1989).

2.4.2 Research/Education Potential

Since wetlands of all types have been observed to support a great number and variety of life

forms, they also represent a living laboratory for the study of ecosystem dynamics, the inter

relationships between abiotic and biotic elements and processes.

21

However, other than general statements of this nature, little has been documented about the

use of wetlands for education and research, although this use may be considerable. For

example, about one-half of the high schools in Ontario, Canada incorporate at least one

annual wetland visit as part of their science curriculum. Moreover, the extensive body of

literature on wetlands demonstrates the general significance of these systems for research

(Bardecki, 1984).

For an individual wetland to have research/educational value, it must be accessible by foot

and/or vehicle. In addition, its proximity to and affiliation with an educational institution will

enhance its educational value.

2.5 Wetland Evaluation Methods

Previous literature reviews of wetland evaluation methods have been conducted by Lonard,

Clairain, Huffman, Hardy, Brown, Ballard and Watts, (1981 and 1984) and Bradshaw, J.

(1991). The 1981 review examined 40 wetlands evaluation methods according to several

screening criteria, and assessed 20 of the methods in detail using a series of descriptive

parameters. The 1984 review summarized 25 wetlands evaluation methods identified from

the pre-1981 literature, as well as those published since 1981. This study, therefore, mentions

those methods which are either more recent, more applicable to the present study, and/or are

less well-known in the literature.

2.5.1 Hollands and Magee Method fo r Assessing the Functions o f Wetlands

The method was first developed in 1975 in response to requirements under the Massachusetts

Protection Act to determine the significance of threatened wetlands for each of seven

functions. During the next decade, the authors modified the method to incorporate the

requirements of other state wetland statutes and Section 404 of the Clean Water Act. The

method is now designed to evaluate ten functions: biological, hydrologic support,

22

groundwater, storm and floodwater storage, shoreline protection, water quality maintenance,

cultural and economic, recreational, aesthetic, and educational.

Thirty-two factors (variables) are used to evaluate the ten functions via a semi-quantitative

weighting scheme. Since the authors believed that some factors were of greater significance

than others in evaluating a given function, the factors were weighted based upon the authors'

professional judgment. Numbers were assigned according to the significance (weight) of a

particular factor, and its value (weight) for the wetland in question. Factors used in the

evaluation include: dominant wetland class, class richness, vegetative density, hydrological

position, topographic position in watershed, water level fluctuation, size, percent open water,

underlying and surficial geology and public access.

According to the authors, their method enables comparison among several wetlands, it

provides wetland inventory data for regulatory agencies, it is quick, simple and inexpensive,

and the results compare favorably with more complex methods such as the Adamus (1983)

method. The only disadvantage they claim, however, is that the method cannot be done by

one individual. A two-person team comprising a geologist/hydrologist and a

botanist/ecologist experienced in wetlands is required.

2.5.2 A Method fo r Assessing Wetland Characteristics and Values

Marble and Gross (1984) provide a classification and qualitative evaluation system to identify

glaciated northeastern wetland functions and their social values. The authors profess that the

information required to determine wetland values can be easily collected and assessed.

Therefore, the method can be implemented on a regional- or municipal-wide level to provide

local decision-makers, planners and other interested individuals with consistent and

comparable data on wetlands.

23

The method identifies the relative importance of wetlands in providing wildlife habitat, flood

control and erosion/sediment control, based upon the assumption that physical and functional

attributes of wetlands vary predictably in relation to topographic location. The wetland

physical characteristics of vegetation, size, underlying glacial material and surface hydrology,

were found to be highly correlated with the three landscape positions of valley, hillside and

hilltop. Moreover, landscape position frequently determined wetland values relating to

wildlife habitat, flood control and erosion/sediment control. Based on these relationships, it

was concluded that wetlands in valley locations have the highest value, as opposed to hillside

and hilltop wetlands in the Connecticut study area.

As with most evaluation methods, the authors caution that their method is not intended to be

the only tool by which to evaluate wetlands. Scenic, recreational and educational values

should be considered for any political or administrative decision to be complete. A field visit

to the wetland of interest should be made, but time-consuming measurements and sampling

are not necessary. The method, therefore, is not intended to replace intensive field

assessment.

2.5.3 Habitat Assessment Technique (HAT)

The wetland Habitat Assessment Technique (HAT), developed by Cable, Brack and Holmes

(1989), is the first known attempt to directly incorporate ecological concerns (faunal and

species indices) with the concept of economic efficiency (optimum habitat area). It represents

a refinement of the earlier efforts to modify the Graber and Graber (1976) method and

addresses many of the concerns expressed by Lonard and others (1981) (Cable et al., 1989).

The HAT procedure is founded on the premise that species diversity and the uniqueness of

species found in a wetland can be used to assess the quality of a wetland habitat. The

presence of both numerous species and uncommon species makes an area more valuable.

Establishing the optimum habitat tract size, however, the element that integrates economics

24

and ecology, is the least precise component of HAT. Additional wildlife studies will help to

provide the missing data on species habitat requirements.

Nonetheless, using birds as indicators, HAT quantifies habitat quality, thus enabling

comparisons to be made among sampled areas. It is not only rapid, (a field visit is not

necessary if site-specific bird records are available), simple and inexpensive, but it can provide

input to more comprehensive evaluation techniques, such as the U.S. Fish and Wildlife

Services' Habitat Evaluations Procedure (HEP), or the Army Corps of Engineers' WET II,

which assess other wetland values.

2.5.4 Wetland Evaluation Technique II (WET II)

WET II, the 1987 revision of the method initially developed for the Federal Highway

Administration, qualitatively evaluates a total of eleven wetlands functions and values:

groundwater recharge and discharge, floodflow alteration, sediment stabilization,

sediment/toxin retention, nutrient retention and transformation, production export, terrestrial

and aquatic wildlife diversity and abundance, uniqueness/heritage and recreation. WET II

evaluates these functions and values at three levels: social significance, effectiveness and

opportunity. Social significance assesses the value of a wetland to society based on its

strategic location, official status or designations, and natural features. Effectiveness assesses

the capability of a wetland to perform a function due to its biological, chemical or physical

attributes. Effectiveness does not estimate the magnitude at which a function is performed

(Larson, Adamus and Clairain, 1989). The last level, opportunity, assesses the probability

that a wetland will perform a function to its level of capability. For example, at present, a

wetland may be potentially very effective at sediment trapping due to its constrictive outlet,

but there may be no sediment to trap. Twenty years later after development has occurred

within its watershed, there may be ample opportunity for the wetland to trap sediment

(Odum, Harvey, Rozas and Chambers, 1986).

25

WET II evaluates a wetland by identifying its functions and values in terms of variables

(factors) that correlate with its biological, chemical and physical characteristics, as well as

those of its watershed or surrounding landscape. Answers to an extensive series of questions

are analyzed in an interpretation key which assigns qualitative probability ratings of high,

moderate or low to each of the functions and values assessed.

The method can be used equally well for a diverse range of systems such as, bottomland

hardwoods, mudflats, desert stream beds and tropical swamps. It can be used with highly

variable levels of data sources ranging from office available data to field testing results

(Cobum, 1993).

Despite its comprehensive nature, WET II is primarily designed for conducting an initial,

rapid assessment of wetland functions and values. It is not intended to substitute for

numerical data or quantitative evaluation methods. It does not, for example, assess the

suitability of wetland habitats for many important wildlife resources, such as furbearers and

game animals. Other methods such as the U.S. Fish and Wildlife Services' Habitat

Evaluations Procedure (HEP) must be used for these species (Adamus et al. 1987). Since the

procedure yields only high, moderate or low values, comparisons among wetlands are difficult

but nonetheless possible.

2.5.5 Manual fo r Assessment o f Bottomland Hardwood Functions (WET-BLH)

Along with its revised version, the WET II procedure also underwent regionalization in 1990.

WET-BLH applies to bottomland hardwoods (BLH) in the southeastern United States. It

evaluates the majority of wetland functions identified in WET II, at both the levels of

effectiveness and opportunity. Along with social significance, WET-BLH adopts additional

categories and evaluates ecological significance, economic significance, cultural and

recreational significance.

26

2.5.6 Method fo r the Evaluation o f Inland Wetlands in Connecticut: A Watershed

Approach

The "Connecticut Method" was first published in 1986 by the Connecticut Department of

Environmental Protection. It was subsequently reviewed for a second publication in 1991.

More recently, the Connecticut Method was adapted for the state of New Hampshire via an

Editorial Review Committee comprised of representatives from several state and private

organizations.

2.5.7 Method for the Comparative Evaluation ofNontidal Wetlands in New Hampshire

As with the Connecticut Method, the New Hampshire Method provides a quasi-quantitative

method of wetland evaluation for use by public officials and those involved in wetlands

management who are not necessarily experts in the wetlands field (Ammann and Stone,

1991). The method is therefore more simple, rapid and easier to use than WET II. It is

designed to be scientifically defensible, although the technical rationales for many of the rating

criteria are not included in the manual. The method encompasses as many of the known

functions and values of wetlands as possible, 14 in total: ecological integrity, wildlife habitat,

finfish habitat, educational potential, visual/aesthetic quality, water-based recreation, flood

control potential, groundwater use potential, sediment trapping, nutrient attenuation,

shoreline anchoring and dissipation of erosive forces, historical site potential and

noteworthiness. It also introduces urban wetland quality values.

To facilitate making comparisons among wetlands, the method advises that all wetlands

within the same watershed be evaluated. The wetlands can then be ranked for each of the 14

functional values. Comparisons among wetlands for each function are easily made because

the technique utilizes a functional value index (FVI). The FVI is obtained from scaled and

weighted values. Since the numbers are only arbitrary and relative, the index is most useful

in comparing different wetlands, or the same wetland under different management plans

27

(Mitsch and Gosselink, 1993).

According to the authors, a number of technical changes have been made in the New

Hampshire version of the Connecticut Method. The flood control function was rewritten and

Ammann added a new function, urban quality of life. The principal author also separated the

sediment trapping and nutrient retention functions into two functions: sediment trapping and

nutrient attenuation. Technical changes were also made in the remaining functions and the

explanatory appendices were expanded.

The method is an inventory and planning tool, not a detailed evaluation method. It is

therefore intended to be used to compare the relative values of a number of wetlands and not

as a site-specific impact evaluation tool (Ammann and Stone, 1991).

2.5.8 A Technique fo r the Functional Assessment o f Nontidal Wetlands in the Coastal

Plain o f Virginia

Also known as the VIMS Technique, this very rapid relatively inexpensive assessment

technique, designed by Bradshaw (1991) at the Virginia Institute of Marine Science, relies on

data easily obtained from existing sources and brief site visits. The method enables the rating

of a wetland as having a high, moderate, or low probability of opportunity and effectiveness

at performing the following functions: flood storage and storm flow modification, nutrient

retention and transformation, sediment retention, toxin retention, sediment stabilization,

wildlife habitat, aquatic habitat and public use. It excludes the evaluation of groundwater

discharge/recharge due to time constraints, and does not explicitly address the social values

of a wetland, other than public use. The factors (variables) characteristic of a particular

function are quantitatively and qualitatively assessed to give a qualitative rating of high,

moderate or low for each factor. The relative importance ("weight") of each factor is

reflected in the combination of the factor ratings, as determined by the interpretation key, to

produce a final rating of high, moderate or low for each function. This, in turn, predicts a

28

wetland's overall ability to perform that function.

The method has had limited field testing but is promising. Revisions of the technique are

currently being considered to better evaluate functions according to effectiveness and

opportunity. In addition, modifications are anticipated to create several versions of the

technique to enable the evaluation of different wetlands according to type and landscape

position (e.g. lakeside, riverine and estuarine).

2.5.9 Canada's Wetland Evaluation Guide

The scope of functions evaluated in the Canadian method is similar to that of WET II, but it

does not clearly differentiate between wetland functions, processes, products and values.

According to Larson and Mazzarese (1992), it nevertheless advances wetland assessment into

a new dimension. The guide consists of three stages. Stage One, called the "General

Analysis," is a preliminary assessment of the wetland, based upon biophysical, hydrological,

biogeochemical and socio-cultural data, and the proposed project, based upon economic

significance. All considerations are at an international, federal, or provincial/state level of

significance. A few also consider regional importance.

Comparing the significance of the wetland and the project provides the evaluator with

knowledge about the desirability of: 1) protecting the wetland due to its exceptional value;

2) approving the project because it has outstanding value and the wetland has little or no

value; and 3) deferring to Stage Two because no conclusion is obvious. (The ratings provide

guidance only to the recommendations.) Stage Two, the "Detailed Analysis," is a detailed

assessment of the functions and benefits of both the wetland and the proposed project using

a multiple value evaluation matrix. The matrix requires biological, hydrological and

biogeochemical, social/cultural and market and non-market economic production values of

the wetland. It also uses project production values. The stage is divided into six steps: steps

one to five complete the evaluation matrix and provide a summary of wetland and project

29

status; step six recommends a course of action: project approval, rejection, approval with

conditions, or referral to Stage Three.

Designed for the evaluation of federal, or at most, provincially significant projects,the final

stage, "Specialized Analysis," requires expertise in resource economics, biology and financial

assessment. It emphasizes the calculation of precise market and non-market economic

production costs and benefits occurring from wetlands as well as from proposed development

with potential impact.

30

3.0 METHODS AND SITE DESCRIPTIONS

3.1 Selecting the Evaluation Methods

Three wetland evaluation methods were selected for critique in this study: the Wetland

Evaluation Technique II (WET II), revised by the U.S. Army Corps of Engineers (Adamus,

Stockwell, Clairain, Smith and Young, 1987); the Method for the Comparative Evaluation

of Nontidal Wetlands in New Hampshire (New Hampshire Method), produced by A.P.

Ammann and A.L. Stone (1991); and, the Technique for the Functional Assessment of

Nontidal Wetlands in the Coastal Plain of Virginia (VIMS Technique), designed by J.

Bradshaw (1991) at the Virginia Institute of Marine Science.

WET II was developed after many years of research and review by numerous individuals from

government (COE, FWS, EPA), academia and private industry. The method was selected for

this study because due to its history of development and extensive use to date, WET II is

regarded as one of the most comprehensive wetlands evaluation methods available and is

currently one of the best known. It can evaluate all types of wetlands in the coterminous

United States and therefore could be used for this study.

WET II consists of three levels of assessment effort for certain functions and values. Since

the third level necessitates the calculation of species diversity indices and the seasonal

assessment of several factors, evaluation was restricted to the second level of effort to make

the assessment feasible within one or two working days. Also, this made the degree of effort

more comparable with the other two techniques. The interpretation key from WET II is

available in a computerized version and was used to interpret and store the field data in this

study.

The New Hampshire Method was selected because, like WET II, it is comprehensive in the

number of functions and values it assesses, yet, unlike WET II, it is not geared for exclusive

use by wetland scientists and those with similar expertise. Ammann and his co-workers

31

created the method so that any concerned citizen could "red-flag" a wetland if, for example,

local developmental pressures were eminent. Although designed for the state of New

Hampshire, the method was easily applied to the non-tidal wetlands of Virginia. The method

is attractive to use in New Hampshire because the manual includes county, soil and

groundwater map data. As with other qualitative assessment techniques, the New Hampshire

Method claims to be scientifically defensible but its questions are fewer in number; hence, it

requires less time to use compared with WET II.

Lastly, the VIMS Technique was selected for two reasons: it was designed for the coastal

plain of Virginia, and since further revisions of the technique are anticipated for the future,

as much field testing as possible was advocated.

3.2 Site Selection

The three evaluation methods were critiqued to identify the similarities and differences in their

assessment of nontidal wetlands. Twenty York River basin nontidal wetlands, representing

a variety of wetland classes in the coastal plain of Virginia, were selected for study sites.

Selection was based upon the class and size of wetland, as well as accessibility by vehicle and

foot. As Figure 1 shows, 12 of the wetland sites were located in the upper reaches of the

York River, in the vicinity of West Point, Virginia. The remaining 8 sites were selected from

York County and the City of Newport News. Wetland sites were chosen to ensure a diversity

of wetland classes and surrounding land-uses was used in the study.

32

Figure 1: Location of Wetland Sites in the York River Basin, Virginia

33

Wetl

and

Site

s

The nontidal wetlands represented three major Palustrine classes: forested, scrub-shrub and

emergent wetlands, as identified by National Wetland Inventory (NWI) maps. The NWI

developed a standardized system that would serve all agencies in the United States. The

classification scheme, based on Cowardin et al. (1979), groups ecologically similar habitats,

furnishes acceptable units for inventory and mapping, and provides uniformity in concepts,

terminology and definitions. The system uses a hierarchial format of systems, subsystems,

classes, subclass modifiers and dominance types. Consequently, a wetland can be clearly

defined (Cobum, 1993). The Palustrine System includes all nontidal wetlands dominated by

trees, shrubs, persistent emergents, or emergent mosses and lichens. It also includes wetlands

lacking such vegetation, but with all of the following four characteristics: 1) area less than

8 ha (20 acres); 2) lack of active wave-formed or bedrock shoreline features; 3) water depth

in the deepest part of the basin less than 2 m (6.6 ft) at low water; and, 4) salinity due to

ocean-derived salts less than 0.5 ppt (Cowardin et al., 1979).

3.3 Materials

Field equipment included a hand-held level and stadia rod for estimation of elevations between

the water/wetland border and the wetland/upland border (as required by the VIMS

technique), a soil probe and a metre stick for water depth and velocity estimations.

The evaluation methods not only require field visits, but also information from various other

published sources. The most recent (1989-93) National Wetland Inventory (NWI) maps

(1:24,000) were used to select and identify the twenty nontidal wetland sites. U.S. Geological

Survey Topographic Maps (1:24,000) and NRCS Soil Survey Maps (1:15,840) of the

counties were referenced to determine surrounding land-use and possible impacts to the

wetland, public access for educational, research and recreational purposes, and soil/sediment

composition. Agencies and organizations such as the Department of Conservation and

Recreation, (Divisions of Natural Heritage, and Planning and Recreation), Department of

Game and Inland Fisheries, Department of Environmental Quality (Water Division),

34

Department of Historic Resources, and the appropriate Planning District Commissions were

contacted for information on wildlife and aquatic importance of the wetlands, the recreational

significance of the sites, groundwater and surface water relevance of the wetlands,

archaeological significance of the areas and rate of development in the surrounding landscape,

respectively. Although the majority of these values were not used in the final comparative

study, all questions asked by all three methods were answered as completely as possible.

To calculate acreage (wetland(s), watershed, open water) and stream length, GIS

(Geographic Information System) technology was used, specifically, the software package

ARC/Info 6.0. (ARC/Info is a registered trademark of ESRI, Inc. of Redlands, California).

3.4 Data Analysis

3.4.1 Field Component

To critique the three methods, a function-specific comparative study was done. Since the

methods varied in the total number of functions they assessed, the five functions common to

all three methods were examined. These were floodflow alteration, nutrient retention and

transformation, sediment/toxin retention, wildlife habitat and aquatic habitat.

Each of the twenty wetland sites was assessed using all three evaluation methods. (See

Appendix D for examples of questions and interpretation keys). The final ratings from each

method for the five functions were tabulated and compared via similarity indices. The indices

were calculated by adding together the number of sites which received two identical ratings

from two of the techniques, (i.e. two H's, two M's or two L's), and dividing that number by

20, the total number of sites.

35

3.4.2 Theoretical Component

The type of information (factors) required to evaluate each function was compared among

the three methods by categorizing the factors into broad terms. (See Table C l excerpt below

and Tables Cl to C5 in Appendix C).

Table Cl: Floodflow Alteration - Factors Used by each Method to Evaluate theFunction...

No. FactorH M

WET VIMS NH WET VIMS

1

Water velocity/flow ( inlet/outlet/channel characteristics - constriction, ditches, canals, channelization, levees, type of flow, sinuosity)

2 Acreage (wetland(s), including accessible wetlands, watershed [ratio], open water)

3Hydroperiod/hydrology (flooding regime, extent and duration, ponding, impoundments)

4 Vegetation ([sub]class, density, fringe, interspersion with water, zonation)

For example, questions relating to water velocity, degree of channel constriction, or sinuosity

were all lumped under the water velocity/flow category. Any question about acreage was

placed into a category by that name. Acreage for the wetland itself, its watershed, upstream

wetlands, the waterbody, etc., were all grouped into the same broad category. The challenge

was to lump as many of the headings and subheadings used by WET II into as few categories

as possible, without losing vital information, while maintaining enough commonality so as to

be able to compare the data with the other two less comprehensive methods. This

arrangement was used to record the ranking of each factor in determining its degree of

influence (weight) on a final rating of High (H), Moderate (M) or Low (L) for the function.

36

To calculate the degree of influence (weight) of each factor, two basic approaches were used.

One involved the calculation of probabilities. Since the VIMS Technique comprised relatively

few questions and a simple interpretation key, it was possible to identify all the various

combinations of responses that could result in the three final ratings of H, M and L for each

function. In other words, it was possible to sample the entire "universe." Tables B2.1&2,

B5.1&2, B8.1&2, B11.1&2 and B14.1&2 in Appendix B, with an example below, illustrate

how this was done.

37

Tabl

e B5

.1:

VIM

S Te

chni

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- Fac

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Used

in

Nut

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and

Tran

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Rat

ings G

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55 S 55 S 5 5 S 55 -< &

55 S

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55 S

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55 S

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bo3JO©3©

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12 ^3 ©3 £

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- 32,

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14,

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0 (7

%,

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)

Table B5.2: VIMS Technique - Number of High (H), Moderate (M) and Low (L)Responses to Each Factor that Results in a Final Rating of High, Moderate or Low for Nutrient Retention and Transformation

FactorsFrequency of Responses

H M L H M L H M L

Potential sources of excess nutrients: 16 16 0 138 138 138 8 8 24

Proportion of land with nutrient source... 16 16 0 138 138 138 8 8 24

Average runoff in 2 year, 24 hour storm: 24 4 4 133 153 128 5 5 30

Average slope of watershed: 24 4 4 133 153 128 5 5 30

Proportion of 2 year, 24 hour storm... 28 0 4 210 0 204 5 0 35

Retention/detention of stormwater... 24 4 4 133 153 128 5 5 30

Final Rating: Total Number of Combinations

32 H 414 M 40 L

Once the total number of possible combinations was identified, the probability that a response

of h, m or 1 to each factor would yield an analogous final rating of H, M or L was calculated

(Tables B2, B5, B8, B 11 and B 14 in Appendix B). For example, Tables B5.1 and B5.2 show

that there are 486 different ways to answer all six factors to evaluate the nutrient retention

and transformation function. If the entire universe of possibilities is sampled, each factor can

ultimately receive an equal number of high, moderate and low responses i.e. 162 H's, 162 M's

and 162 L's. (Since factor 5 has no Moderate option, it can receive 243 H's and 243 L's).

According to the technique's interpretation key, 32 of the 486 different combinations will

result in a final rating of High (H), 414 in Moderate (M), and 40 in Low (L). When the first

factor, potential sources of excess nutrients, is answered High, theoretically, 16/162 or 10%

of the time, the final rating will also be High. When it is given a Moderate response, 138/162

or 85% of the time, the final rating will also be Moderate. Fifteen percent of the time, or

39

24/162 low responses to the first factor will result in a Low final rating. The factors were

ranked in order of decreasing probabilities. A rank of 1 represented the highest probability

that a factor answered h, m or 1 will result in a final rating of H, M or L, respectively.

Table B5: VIMS Technique - Probability that a Response of High (H), Moderate(M) or Low (L) to a Factor will Yield a Final Rating of High, Moderate or Low for Nutrient Retention and Transformation

FactorsH M L

(P) Rank (P) Rank (P) Rank

Potential sources of excess nutrients: 0.10 3 0.85 (2) 0.15 2

Proportion of land with nutrient source... 0.10 3 0.85 (2) 0.15 2

Average runoff in 2 year, 24 hour storm: 0.15 1 0.94 1 0.19 1Average slope of watershed: 0.15 1 0.94 1 0.19 1Proportion of 2 year, 24 hour storm... 0.12 2 0 - 0.14 3

Retention/detention of stormwater... 0.15 1 0.94 1 0.19 1

Final Rating: 1a 5A 1L(P) - probability(2) - Actually has no influence on the Moderate final rating. There was calculated to be an equal probability (0.85) among all three responses (h, m, l)in their effect on a Moderate outcome.

Although there are few questions to be answered in the VIMS Technique, many questions

represented more than a single factor category. For example, factors 3 and 5 in the above

table, average runoff and storm volume, involve some quantitative calculations and additional

considerations to arrive at a response. Factor 3 not only uses the average rainfall for the

region, but also requires the estimation of land-use proportions and the size of the wetland,

its watershed and any upstream wetlands. Factor 5 involves the same calculations as well as

the determination of wetland storage capacity. Therefore, if two or more rankings were given

to the same factor category in influencing the same final outcome, the highest rank was used.

As in the case of a High rating, Factor 3 is ranked a 1, while Factor 5 is ranked a 2. A rank

of 1 would therefore be used for the implied factor categories of climate/rainfall, land use and

acreage.

40

For the New Hampshire and WET II methods, a final score of 1.0 was used since the

identification of all possible combinations (sampling the entire “universe”) could not be done

feasibly. Nonetheless, the New Hampshire Method was straightforward to analyze. Unlike

the other two techniques where a factor's degree of influence on the final rating may change,

the factors in the New Hampshire Method keep the same weight, regardless of whether a

High, Moderate or Low rating is being determined. In addition, the method asks a series of

questions whose h, m and 1 responses are assigned semi-quantitative values of 1.0, 0.5 and

0.1, respectively. The Functional Value Index (FVI) used by the method requires that the

average score of all the questions be calculated. Consequently, a maximum score of 1.0 is

possible, (not involving the final step of multiplying by an acreage value to obtain a Wetland

Value Unit (WVU)). Therefore, a value of 1.0 was divided by the total number of questions

per function to arrive at a weight for each question. Some questions belonged to a subset

asked in previous sections. For example, the nutrient retention and transformation function

uses FVTs from the sediment/toxin retention function, and the wildlife habitat function uses

the FVI from a functional value known as Ecological Integrity. These factors (questions)

consequently received lower weights. The factors were ranked in order of decreasing weight.

(See Table B6 below , modified to show ranking and Tables B6, B9, B12 and B15 in

Appendix B).

Acreage (the entire wetland or stream/lake area) is used in the New Hampshire Method as a

multiplier in all functions to obtain the Wetland Value Unit (WVU). Acreage, therefore, has

the greatest influence in determining a final rating for any function. Regardless of the FVI,

small wetlands tend to rate Low on the WVU scale; large wetlands, High. As a result, the

acreage factor was labelled the multiplier and given the highest rank.

41

Table B6: New Hampshire Method - Weight and Rank of Factors in Nutrient____________ Retention and Transformation Ratings____________________________

Factors Weight Rank

Average slope of watershed above wetland:H: >8% M: 3-8% L: <3% 0.0875 4

Potential sources of excess sediment in the watershed above the wetland:H: extensive areas of active cropland, construction sites, eroding banks, ditches, etc.M: some areas of active cropland, a few construction sites, and similar areasL: land use in watershed predominantly forested, abandoned farmland or undeveloped

0.0875 4

Potential sources of excess nutrients in watershed above wetland:H: large areas of active cropland, pastureland, or urban land; many dairies/livestock operations, sewage treatment plants/numerous on-site septic systems within 100’ of streamM: watershed contains some/few such areas/operations/plants/systems within 100' of streamL: watershed predominantly forested or otherwise undeveloped

0.125 3

Effective floodwater storage of wetland 0.05 5

Wetland location in relation to an intermittent or perennial stream or a lake:H: wetland forms a buffer > 50 ft wide between upland and stream or lakeM: buffer 20-50 ft wideL: buffer < 20 ft wide or wetland not bordering a stream or lake

0.05 5

Dominant wetland class bordering a stream or lake:H: scrub-shrub or dense stands of cattails or phragmites M: forestedL: other types, or wetland does not border a stream or lake

0.05 5

Areas of impounded open water (including beaver dams):H: wetland contains permanently impounded open water > 5 acres M: 0.5-5 acresL: < 0.5 acres or wetland does not contain open water

0.05 5

Dominant wetland class:H: floating aquatic plants, emergent (marsh), forested, or scrub/shrub L: bogs

0.25 2

Wetland hydroperiod:H: wetland contains permanently impounded open water > 5 acres M: 0.5-5 acres, OR > 5 acres of wetland flooded or ponded annually L: above criteria not met (saturated or rarely ponded or flooded)

0.25 2

Functional Value Index (FVI) 1.0 -

Total area of wetland (acres) multiplier 1

Wetland Value Units WVU -H, M, L -1.0, 0.5, 0.1

42

Table B3.1 shows the "sensitivity” analysis performed on the floodflow alteration function of

the New Hampshire Method. For only this function, the method uses the factors to produce

two ratios. Since the operator is therefore division and not addition, a "weight" could not be

assigned to the factors of wetland acreage, watershed acreage and wetland control length

(outlet diameter). Instead, each of the three factors was increased by 1%, 5%, 10%, 50%,

100%, 200% and 500% increments, while holding the other two factors constant, to detect

the effect each could have on the FVI. The three factors were ranked according to which had

the most and which had the least effect on the FVI for floodflow (Table B3).

Table B3.1: New Hampshire Method - Sensitivity Analysis of Floodflow AlterationFactors

PercentIncrease

WetlandArea FVI Watershed

Area FVI OutletDiameter FVI

0 1.00 0.600 2.00 0.600 2.00 0.600

1 1.01 0.600 2.02 0.600 2.02 0.600

5 1.05 0.600 2.10 0.610 2.10 0.575

10 1.10 0.600 2.20 0.620 2.20 0.550

50 1.50 0.600 3.00 0.700 3.00 0.435

100 2.00 0.600 4.00 0.800 4.00 0.350

200 3.00 0.600 6.00 0.900 6.00 0.225

500 6.00 0.600 12.00 0.800 12.00 0.055

PercentIncrease



0 20.00 1.00 50.00 1.00 4.00 1.00

1 20.20 1.00 50.50 1.00 4.04 1.00

5 21.00 1.00 52.50 1.00 4.20 1.00

10 22.00 1.00 55.00 1.00 4.40 1.00

50 30.00 1.00 75.00 1.00 6.00 1.00

100 40.00 1.00 100.00 1.00 8.00 1.00

200 60.00 1.00 150.00 1.00 12.00 1.00

500 120.00 1.00 300.00 1.00 24.00 0.81

43

PercentIncrease



0 10.00 1.00 100 1.00 3.00 1.00

1 10.10 1.00 101 1.00 3.03 1.00

5 10.50 1.00 105 1.00 3.15 1.00

10 11.00 1.00 110 1.00 3.30 1.00

50 15.00 1.00 150 1.00 4.50 1.00

100 20.00 1.00 200 1.00 6.00 1.00

200 30.00 1.00 300 1.00 9.00 0.94

500 60.00 1.00 600 0.95 18.00 0.71

Table B3: New Hampshire Method - Ranking of Factors in Floodflow AlterationRatings

Factors Rank

Area of wetland in acres 3

Area of watershed above the outlet of the wetland in acres 2

Wetland Control Length (WCL) in feet [outlet diameter] 1

Functional Value Index (FVI) for Flood Control Potential FVI

Total area of wetland (acres) multiplier

Wetland Value Units WVU

The New Hampshire Method informs the user that there are a variety of ways in which the

data can be interpreted for planning/management purposes. To illustrate one such way, the

Functional Value Index (FVI) for each function was recorded, and when the Wetland Value

Unit (WVU) differed from the FVI, the WVU was recorded in parentheses. Wetland size

ranged from 0.147 acres to 24.984 acres, with only three sites possessing acreages greater

than 10. When all twenty WVU’s for each function were divided into three equivalent ranges

and assigned H, M and L ratings, only the larger sites received a High rating; most were rated

Low due to this range in acreage. Ratings established in this way made the New Hampshire

Method appear to be very insensitive at differentiating among various wetlands. It was

decided, therefore, to assign the WVU’s corresponding H, M and L values by grouping the

sites according to landscape position (Table AO). Three categories of stream order were

used: isolated wetlands, which had no surficial hydrologic connection at any time of the year

44

to any other wetland; first-order wetlands, whose surface water represented a headwater or

the beginning of a perennial stream; and, higher-order wetlands, whose streams resulted from

the joining of at least two upstream channels. Once grouped, the range in WVU’s was

divided into three equal segments and assigned ratings of High, Moderate and Low.

Table AO: Final Ratings by New Hampshire Method Using Stream Order to Groupthe Wetland Sites

Site # FF Rating NRT Rating S/TR Rating AH Rating WH Rating

Isolated

13 0.06 L 0.05 L 0.02 L 0 L 0.09 L

15 0.09 L 0.07 L 0.04 L 0 L 0.09 L

18 2.61 H 1.01 H 0.78 H 0 L 1.66 H

19 1.74 H 0.67 H 0.52 H 0 L 1.12 H

20 0.54 L 0.32 M 0.20 L 0 L 0.57 M

First-Order

6 1.70 L 0.94 L 0.84 L 0.04 L 0.98 L

8 2.09 L 1.37 M 1.30 M 0.16 L 1.66 M

9 5.40 H 4.22 H 3.38 H 3.30 H 4.28 H

10 2.01 L 1.02 L 0.79 L 0 L 1.36 M

11 6.50 H 2.94 H 2.99 H 0 L 3.53 H

17 0 L 0.28 L 0.18 L 0.30 L 0.42 L

Higher-Order

1 3.65 L 2.10 L 1.82 L 0.10 L 2.51 L

2 3.07 L 1.50 L 1.53 L 0.03 L 2.22 L

3 16.67 H 10.54 H 11.33 H 0.41 L 13.85 H

4 24.98 H 15.80 H 16.99 H 0.49 M 18.26 H

5 2.30 L 1.40 L 1.34 L 1.32 H 1.72 L

7 4.80 L 5.43 M 5.14 L 0.10 L 6.09 M

12 24.68 H 16.04 H 14.81 H 0.55 M 18.13 H

14 4.70 L 2.52 L 2.50 L 0.07 L 3.58 L

16 0 L 0.58 L 0.30 L 0.59 M 0.85 L

FF - Floodflow AlterationNRT - Nutrient Retention and TransformationS/TR - Sediment/Toxin RetentionAH - Aquatic HabitatWH - Wildlife Habitat

45

To maintain a degree of consistency, and at the same time solve the problem of the purely

qualitative nature of WET II, the WET II technique was also analyzed using a final score of

1.0. However, since the interpretation keys were complex for this method, adjustments had

to be made. Often, a factor could have varying weights depending on its locations throughout

the key. Therefore, it was decided to calculate the maximum possible weight for each factor

used in evaluating the function (Tables B l, B4, B7, BIO and B 13 in Appendix B; Table B1

simplified below). For instance, if three questions belonging to the same level of the key all

had to be answered correctly to obtain a High rating, then each question/factor would be

assigned a weight of 0.33 (1.0/3). If a High rating could also be achieved by answering those

same three questions as "false," but answering an additional question at the next level of the

key as "true," then all four questions would have a weight of 0.25 (1.0/4). However, since

the maximum possible weight was used in the final analysis, the first three questions would

keep their weights of 0.33, while the fourth would receive 0.25 as its maximum weight. This

seemed appropriate since the fourth question was on a lower level. (See Appendix B, after

Table B l, for an illustration). As with the other two techniques, if the same factor received

two or more weights in its influence on the same final rating, the highest weight was used.

Again, the factors were ranked in decreasing order, with a rank of 1 assigned to the factor

with the most weight.

46

Tabl

e B4

: W

etlan

d Ev

alua

tion

Tech

niqu

e - M

axim

um

Possi

ble

Weig

ht o

f Fa

ctors

tha

t can

Co

ntrib

ute

to a

Fina

l Ra

ting

of H

igh

(H),

Mod

erat

e (M

) or

Low

(L)

for

Nut

rien

t Re

tent

ion

and

Tra

nsfo

rmat

ion

co(N <N

O

COCM

O

o© <oo o

CO

T3oxT3

m

©<N

O' ©co O

00

00 o

CL,

cnco

(SIVO

O

CSVO

T3<uT3

JO

*0two o

T3

co inO *—<

- max

imum

we

ight

for

oppo

rtuni

ty

(vs.

effe

ctiv

enes

s)

For the floodflow, nutrient and sediment functions, it was found that occasionally, factors

were used for evaluating opportunity, but not effectiveness, two concepts that are kept

separate in WET II. Ignoring the opportunity ratings would have implied that WET II failed

to consider some factors that were used by one or both the remaining methods. Information

would have been lost. To ensure fair treatment, since the other two techniques combined the

concepts, it was decided to record the opportunity ratings in parentheses when they differed

from the effectiveness ratings.

Only the Palustrine System was examined for the aquatic/finfish habitat and wildlife habitat

functions of WET n. The corresponding interpretation keys had specific boxes for the other

wetland systems of Estuarine, Lacustrine and Riverine. Since the field sites for this study

represented only the Palustrine System, those factors specific to the other systems did not

contribute to the final rating for these functions. Determining the weights of these factors,

therefore, would not have helped in explaining any field result discrepancies among the

methods. In addition, WET II actually separates the wildlife (waterfowl) function into three

categories: breeding, migration and wintering. To facilitate comparison with the other two

methods, the wildlife habitat key was treated as a single key by summing the maximum

possible weight from each of the three wildlife keys, to obtain a cumulative weight.

Consequently, for this function of WET II, the score could be greater than 1.0, but the

ranking process was the same.

To determine how much of the same type of information was used by each method to assess

the five functions, similarity indices were calculated. The cumulative number of different

factors used between each pair of methods comprised the denominator. The number of

factors shared by the two methods constituted the numerator.

Similarity indices were also calculated to determine to what extent the factors shared by two

methods were also given the same weight or degree of influence in evaluating the same

function. The number of factors given the same ranking by both methods was divided by the

48

number of factors the two methods had in common.

Finally, as a practical application, the study attempted to assess how useful and reliable the

acquired field data may be in assisting with management decisions. Using the field data from

any two sites of the same wetland class, i.e. two PFOlA's or two PFOlC's, tables were

constructed to illustrate one way in which the results from this study could be organized to

offer useful landscape management information.

49

4.0 RESULTS

Tables A1 to A20 in Appendix A record the results of using all three evaluation methods on

each of the twenty wetland sites.

Table A21: Summary of Field Results per Rating

FunctionH M L

WET VIMS NH WET VIMS NH WET VIMS NH

Floodflow Alteration 12 16 15 7 2 3 1 2 2

Nutrient R & T 10 0 1 1 19 19 9 1 0

Sediment/Toxin Retention 12 0 2 0 19 12 8 1 6

Aquatic/Finfish Habitat 0 11 4 8 0 9 12 9 7

Wildlife Habitat 17 9 11 3 10 9 0 1 0

Using only the Functional Value Index (FVI) ratings from the New Hampshire Method, Table

A21 reveals that all three methods tended to rate a majority (at least 12/20 or > 60%) of the

wetlands High for floodflow alteration. The three methods were similar in their individual

treatments of both the nutrient and sediment functions. Within each method, the numbers of

H, M and L’s were essentially the same for both functions. WET II evaluated most sites as

having either a High or a Low probability of performing the nutrient and sediment functions;

the VIMS and New Hampshire methods evaluated most sites as having a Moderate rating.

The proportion of H, M and L’s varied greatly among the three methods for the

aquatic/finfish habitat function. WET II failed to assign any H’s to the sites; the VIMS

Technique, any M ’s. For the wildlife habitat function, all three methods tended to evaluate

the sites as having either a High or Moderate probability of providing valuable habitat. Both

the VIMS and New Hampshire methods assessed half the sites as High, half as Moderate.

WET II awarded 85% of the sites as High.

50

Table A22: Number of Sites that Received Three Identical/Different Ratings

FunctionNumber of Sites

Identical Ratings Different Ratings

Floodflow Alteration 7 2

Nutrient Retention & Transformation 1 2

Sediment/Toxin Retention 0 7

Aquatic/Finfish Habitat 1(3) 6

Wildlife Habitat 9 1

(#) - value calculated using WVU's grouped by stream order for the NH Method

Table A23: Similarity Indices Between 2 Evaluation Methods for All 20 Wetland Sites

Function WET vs VIMS VIMS vs NH WET vs NH

Floodflow Alteration 0.70 0.55 0.35

Nutrient Retention & Transformation 0.05 0.90 0.05

Sediment/Toxin Retention 0.05 0.55 0.05

Aquatic/Finfish Habitat 0.15 0.55 0.10

Wildlife Habitat 0.60 0.55 0.70NH - ratings determined using FVTs (not WVU's)

If only the Functional Value Index ratings are used from the New Hampshire Method, Tables

A22 and A23 show that the wildlife habitat function exhibited the most agreement among the

three evaluation methods. Nine out of the twenty wetland sites received identical ratings from

the three techniques (i.e. three H's, M's or L's). All three similarity indices were > 55%.

More than half of the sites were given the same rating from two of the methods.

The floodflow alteration function displayed the second most agreement among the three

methods if the New Hampshire Method's FVI ratings were used in lieu of the Wetland Value

Unit ratings. Seven out of the twenty wetland sites were given the same final rating by all

three methods. All three similarity indices were >35% . At least one-third of all the sites

received identical ratings from the three methods.

51

If the WVU’s are used instead of the FVI’s, three sites received the same evaluation from the

three methods for the aquatic/finfish habitat function. (All three sites received a Low rating

from each method.) Just over half of the sites, (11/20 or 55%) were given the same

evaluation by the VIMS and New Hampshire methods. However, six sites were given

completely different ratings by the three methods; that is, each of the six sites received an H,

M and L for the aquatic/finfish habitat function.

Only one site showed a three-way agreement for nutrient retention and transformation.

However, the highest similarity index out of the five functions was achieved between the

VIMS and New Hampshire methods for the nutrient function. Eighteen of the twenty

wetlands, or 90% of the sites, received the same rating from these two techniques.

Not a single site was given the same rating by all three for sediment/toxin retention. In fact,

as far as displaying the most disagreement among the three methods, sediment/toxin retention

resulted in the highest total of seven sites. As with the floodflow, aquatic habitat and wildlife

habitat functions, 55% of the sites did receive the same final rating by the VIMS and New

Hampshire methods for sediment/toxin retention.

Finally, Table A23 shows that the VIMS Technique always shared the highest similarity index

with one of the other methods for the floodflow, nutrient, sediment and aquatic habitat

functions.

52

5.0 DISCUSSION

The wildlife habitat function exhibited the most agreement among the three evaluation

methods in assessing the 20 wetland sites. Historically, wetlands were first recognized and

appreciated for their habitat value. Literature about the role of wetlands for this function is

extensive and probably the best known when compared with the other four functions. The

critical factors for predicting the probability that a wetland will perform this function may be

clearly identified, leaving little question as to which factors are the most important. Table C5

in Appendix C (simplified below) shows that acreage, vegetation, accessibility, degree of

disturbance, surrounding land use, wetland type and water quality are used by all three

methods to evaluate wildlife habitat. Overall, the three methods use 44-64% of the same type

of information to evaluate the wildlife function (Table C6 below)

At least 19 of the 20 sites, or 95% of the wetlands surveyed, were rated as having either a

High or Moderate probability of providing valuable wildlife habitat (Table A21). Many

wetland scientists and managers appear to favour the wildlife habitat function as one of the

most, if not, the most valuable function a wetland can perform (P. Mason and J. Bradshaw,

pers. comm.). Hence, there could be a built-in bias towards rating most wetlands as having

at least a Moderate probability of performing the function.

53

Table C5: Wildlife Habitat - Factors Used by each Method to Evaluate theFunction and their Ranking from Most Influential (1) to Least Influential (13) in Determining a Final Rating of High (H), Moderate (M) or Low (L)__________________________________________________

No. FactorH M L

W V N W V N W V N

l Acreage 1 2 l l 2 l 2 2 l

2 Vegetation 4 2 3 2 2 3 1 2 3

3 Accessibility/proximity 5 2 3 3 2 3 5 2 3

4 Disturbance/impacts 4 2 4 4 2 4 3 2 4

5 Land use 4 2 4 8 2 4 2 2 4

6 Wetland type 2 1 3 7 1 3 5 1 3

7 Water quality 11 2 2 13 2 2 7 2 2

8 Soil composition 6 - 4 6 - 4 3 - 4

9 Water velocity/depth 8 - 3 9 - 3 4 - 3

10 Special habitat features 6 - 3 10 - 3 - - 3

11 Islands/inclusions of upland - - 3 - - 3 - - 3

12 Climate 3 - - 1 - - 6 - -

13 Exposure/fetch 10 - - 5 - - 4 - -

14 Salinity/conductivity 12 - - 13 - - 3 - -

15 Hydroperiod 7 - - 3 - - - - -

16 Wetland/upland border shape 6 - - 11 - - - - -

17 PH 9 - - 12 - - - - -W - WET, V - VIMS, N - NH

Discrepancies among the methods, however, did exist when assessing the wildlife habitat

function. These may be due to a number of reasons. Both the New Hampshire and VIMS

methods maintain the same rankings for the first 7 factors, whether interpreting for a High,

Moderate or Low outcome. WET II, however, tends to change the degree of influence a

factor has on the final rating when evaluating for a specific outcome. Although not ranked

above a 3 in their degree of influence on the final result, the factors of soil composition, water

velocity/flow and special habitat features are not used by the VIMS Technique to evaluate

54

wildlife habitat, and the remaining seven factors of climate, degree of exposure, salinity

regime, hydroperiod, boundary shape and pH, are used solely by WET II. This difference in

the type of information used to assess the function may explain why less than 71% (Table

A23) of the sites received identical ratings by two or more of the evaluation methods.

Moreover, of the factors the techniques have in common, Table C7 reveals that < 30% are

given the same degree of influence in determining the final rating.

Table C6: Similarity Indices Between 2 Evaluation Methods in the Type of____________ Information (Factors) Used to Evaluate the 5 Functions_____________

FunctionWET vs VIMS VIMS vs NH WET vs NH

H M L H M L H M L

Floodflow Alteration 0.67 0.50 0.67 0.33 0.20 0.33 0.29 0.29 0.29

Nutrient Retention & Transformation 0.36 0.40 0.36 0.78 0.67 0.78 0.44 0.44 0.44

Sediment/Toxin Retention 0.33 0.46 0.43 0.70 0.60 0.70 0.30 0.31 0.31

Aquatic/Finfish Habitat 0.38 0.15 0.27 0.44 0.25 0.33 0.62 0.62 0.64

Wildlife Habitat 0.44 0.44 0.58 0.64 0.64 0.64 0.59 0.63 0.64Calculated using effectiveness (not opportunity) ratings by WET II

Table C7: Similarity Indices Between 2 Evaluation Methods in the Ranking of theFactors Used to Evaluate the 5 Functions


H M L H M L H M L

Floodflow Alteration 0.33 0.33 0.17 0.33 0 0.33 0 0 0.50

Nutrient Retention & Transformation 0.25 0.75 0.50 0.14 0.17 0.14 0.75 0 0.25


Aquatic/Finfish Habitat 0.80 0.50 0 0.50 0.50 0.33 0.25 0.25 0.29

Wildlife Habitat 0 0.14 0.29 0.14 0.14 0.14 0.30 0.30 0Calculated using effectiveness (not opportunity) ratings by WET II

The floodflow alteration function showed the second most agreement among the three

evaluation techniques. Table C l in Appendix C (simplified below) shows that all three

methods used outlet constriction (water velocity) and acreage to evaluate the function. In

fact, Table C6 above reveals that the three techniques use 20-67% of the same information

55

to evaluate floodflow alteration at a site.

Table Cl: Floodflow Alteration - Factors Used by each Method to Evaluate theFunction and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L)______________________________________________________

No. FactorH M L

w V N w V N w V N

1 Water velocity/flow 1 1 2 1 1 2 2 1 2

2 Acreage 2 1 1 2 - 1 4 2 1

3 Hydroperiod/hydrology 1 1 - 2 1 - 1 1 -

4 Vegetation 2 1 - 2 1 - 3 1 -

5 Wetland storage capacity - 1 2 - - 2 - 2 2

6 Climate 3 1 - 4 - - 4 2 -

7 Soils 4 1 - 3 - - 5 2 -

8 Land use (1) 1 - (1) - - (2) 2 -

9 Upstream wetlands (1) 1 - (1) - - (2) 2 -W - WET, V - VIMS, N - NH ( ) - used in opportunity evaluation (vs. effectiveness)

As with wildlife habitat, the literature on floodflow alteration may be sufficient to identify the

key factors. Consequently, agreement in the field is possible. Moreover, the physical and

biological characteristics necessary for performing such a function may be readily

acknowledged and easily visible in the field, compared with the nutrient and sediment

retention functions, for example.

Nevertheless, less than 71% (Table A23) of the wetland sites were given the same rating by

any two of the techniques. The New Hampshire Method relies upon only the three factors

of acreage, constriction (water velocity) and wetland storage capacity to predict the

probability that a wetland will alter floodwater, while WET II and the VIMS Technique ask

additional questions about hydroperiod/hydrology, vegetation, climate and soils. Although

there is a 20-67% overlap in the factors used to evaluate the function, two-thirds of the

similarity indices are below 33% (Table C6), and of those factors common between two

56

techniques, < 50% (Table Cl) are given the same weight (degree of influence). Moreover,

the function has three similarity indices of 0. Not a single factor has the same degree of

influence in determining a Moderate rating between the New Hampshire Method and the

other two techniques, or in determining a High rating between the New Hampshire Method

and WET II.

The highest similarity indices for the nutrient (0.90), sediment (0.55) and aquatic (0.55)

functions were shared between the VIMS and the New Hampshire methods(Table A23). The

methods were extremely similar in evaluating the sites for nutrient retention and

transformation. Ninety percent, or 18/20 wetland sites were given identical ratings by the two

methods. The two use 67-78% of the same information to evaluate the nutrient function

(Table C6, simplified below).



H M L H M L H M L

Nutrient Retention & Transformation 0.36 0.40 0.36 0.78 0.67 0.78 0.44 0.44 0.44

57

Table C2: Nutrient Retention and Transformation - Factors Used by each Methodto Evaluate the Function and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L)________________________________________

No. FactorH M L

W V N W V N W V N

l Vegetation 2 1 2 l 1 2 l 1 2

2 Hydroperiod/hydrology 2 1 2 l 1 2 2 1 2

3 Water velocity/flow 1 1 5 l 1 5 1 1 5

4 Land use 3 1 3 2 1 3 3 1 3

5 Acreage - 1 1 (2) 1 1 (2) 1 1

6 Watershed slope - 1 4 - 1 4 - 1 4

7 Wetland storage capacity - 5 - 5 - 5

8 Climate - 1 - (1) 1 - (2) 1 -

9 Upstream wetlands - 1 - (1) 1 - (2) 1 -

10 Impacts/modifications 2 - - 1 - - 1 - -

11 Soils 3 - - 2 - - 2 - -W - WET, V - VIMS, N - NH ( ) - used in opportunity evaluation (vs. effectiveness)

Table C2 in Appendix C (simplified above) shows that for the evaluation of this function, the

VIMS and New Hampshire techniques both consider the same seven factors: vegetation

density and diversity, type of hydroperiod/hydrology, water velocity/flow/depth

characteristics, surrounding land use, acreage, watershed slope and wetland storage capacity.

The WET II technique, on the other hand, does not use the latter two factors to assess the

nutrient function. Acreage is regarded as the most important factor according to the New

Hampshire and VIMS methods. WET II gives acreage a second-place ranking, but only uses

the factor when evaluating for opportunity separately. Finally, the degree of

impact/modification and soil type are used solely by WET II, which also may account for the

greater degree of disparity between WET II and the other two techniques.

58



H M L H M L H M L

Nutrient Retention & Transformation 0.25 0.75 0.50 0.14 0.17 0.14 0.75 0 0.25

The fact that 18/20 sites received identical ratings from the VIMS and New Hampshire

methods is not well explained, however, by the similarity indices in Table C7 above. Only a

meager 14-17% of those factors shared by the two techniques are ranked the same in degree

of influence on the final rating. The challenge, as mentioned previously, was to represent all

the questions (factors) asked by all three methods by grouping the factors into sufficiently

broad categories so as to enable comparison among the methods. Some detail was lost,

therefore, in the lumping process. Hence, the indices may under- or over-estimate the degree

of similarity between two methods.

As far as receiving three identical ratings, only one site (Table A22), Site 3 (Table A3,

Appendix A) was evaluated as having a Moderate probability of retaining and/or transforming

nutrients by all three methods. Table C6 shows that less than half, 36-40%, and 44% of the

factors used by the methods are shared between WET II and the VIMS Technique, and WET

II and the New Hampshire Method, respectively. This difference in the type of information

used to assess the nutrient function may explain why only 5% (Table A23) of the sites earned

the same evaluation from either WET II and the VIMS Technique, or WET II and the New

Hampshire Method.

Similar explanations exist for the sediment/toxin retention function. Although only 11/20 of

the sites (55%) received identical ratings from the two methods, both the VIMS and New

Hampshire methods used the same seven factors. As Table C3 in Appendix C (simplified

below) shows, WET II only uses acreage and watershed slope when evaluating for

59

opportunity separately. Wetland storage capacity is not included. As with the nutrient

function, WET II used additional factors not considered by the other two methods. WET II

uses degree of impact/modification, amount of exposure/fetch, salinity regime and special

aquatic habitat features to evaluate for sediment/toxin retention.

Table C3: Sediment/Toxin Retention - Factors Used by each Method to Evaluatethe Function and their Ranking from Most Influential (1) to Least Influential (4) in Determining a Final Rating of High (H), Moderate (M) or Low (L)______________________________________________________

N o . F actorH M L

W V N W V N W V N

1 Vegetation 2 1 2 l 1 2 1 1 2

2 Hydroperiod/hydrology 3 1 2 l 1 2 2 1 2

3 Water velocity/flow 1 1 2 1 1 4 1 1 4

4 Land use (1) 1 3 3 1 3 4 1 3

5 Acreage - 1 1 (1) 1 1 (1) 1 1

6 Soils 2 1 - 1 1 - 1 1 -

7 Watershed slope (1) 1 3 (1) 1 3 (1) 1 3

8 Climate - 1 - 4 1 - 4 1 -

9 Wetland storage capacity - 2 2 - - 4 - 2 4

10 Upstream wetlands - 1 - (1) 1 - (1) 1 -

11 Impacts/modifications 3 - - 1 - - 1 - -

12 Exposure/fetch 3 - - 1 - - 1 - -

13 Salinity/conductivity - - - 1 - - 2 - -

14 Aquatic habitat features - - - 2 - - 3 - -W - WET, V - VIMS, N - NH ( ) - used in opportunity evaluation (vs. effectiveness)

Less than half, 33-46%, of the factors used by the WET and VIMS techniques are common

to both (Table C6, simplified below). Only 30-31% of the factors used by the WET II and

New Hampshire methods are common to both.

60



H M L H M L H M L




H M L H M L H M L

Sediment/Toxin Retention 0.33 0.67 0.50 0.29 0.17 0.14 0.33 0.25 0,25

The sediment/toxin retention function exhibited the most disagreement among the three

evaluation methods. Seven sites (Table A22) received three different ratings from the three

methods; the lowest similarity indices between two of the three methods were calculated for

this function (Table A23 below). This may be explained by the difference in type of

information used by each method, even though out of the few factors they did have in

common, 14-67% were given the same degree of influence on the final rating (Table C7

above).

61

Table A23: Similarity Indices Between 2 Evaluation Methods for All 20 Wetland SitesFunction WET vs VIMS VIMS vs NH WET vs NH

Floodflow Alteration 0.70 0.55 0.35

Nutrient Retention & Transformation 0.05 0.90 0.05

Sediment/Toxin Retention 0.05 0.55 0.05

Aquatic/Finfish Habitat 0.15 0.55 0.10

Wildlife Habitat 0.60 0.55 0.70NH - ratings determined using FVI's (not WVU's)

The literature may be insufficient in identifying the factors which contribute to a wetland’s

ability not only to retain sediments or toxins, but also to retain and/or transform nutrients.

There may not yet be universal consensus about which are the pivotal factors. Another

possible explanation for the disagreement among the methods in assessing the same site for

these functions, could be that both functions may only be adequately evaluated by quantitative

means, due to the inherent nature of their biophysical properties.

Consensus may be lacking for the aquatic/finfish habitat function as the focus and type of

information differ for each method. Both the New Hampshire Method and the VIMS

Technique evaluate this function with fish populations in mind, but the latter noticeably omits

factors which pertain to acreage, vegetation, surrounding land use and substrate composition

(Table C4 in Appendix C, simplified below). WET II evaluates for both finfish and

invertebrates, and asks for additional information such as pH, salinity, temperature and

climate. Nonetheless, degree of impact/modification, water quality, water velocity/depth and

cover/shade are considered by all three methods in predicting the probability that a wetland

will provide aquatic/finfish habitat. Moreover, this was the only function where all three

methods identically ranked a factor they had in common. Degree of impact/modification has

an influence of 2 (out of 5) when all three methods evaluate for a Moderate rating. Water

quality is also ranked a 2 by all three methods, but when determining a High rating.

62

Table C4: Aquatic/Finfish Habitat - Factors Used by each Method to Evaluate theFunction and their Ranking from Most Influential (1) to Least Influential (5) in Determining a Final Rating of High (H), Moderate (M) or Low (L)______________________________________________________

No. FactorH M L

W V N W V N W V N

l Impacts/modifications 1 2 2 2 2 2 2 - 2

2 Water quality 2 2 2 3 1 2 3 1 2

3 Water velocity/depth 1 1 2 3 - 2 3 1 2

4 Cover/shade 1 1 2 4 - 2 - 2 2

5 Hydroperiod 1 1 - 3 - - 3 1 -

6 Acreage 1 - 1 3 - 1 3 - 1

7 Vegetation 1 - 2 2 - 2 2 - 2

8 Land use 1 - 2 3 - 2 3 - 2

9 Substrate type 1 - 2 3 - 2 3 - 2

10 pH 1 - - 2 - - 2 - -

11 Salinity/conductivity 1 - - 1 - - 1 - -

12 Bottom water temperature 3 - - 4 - - - - -

13 Climate 2 - - 5 - - - - -W - WET, V - VIMS, N - NH

The VIMS and New Hampshire methods earned the highest similarity index for the function.

Fifty-five percent of the sites received the same final rating by the two methods (Table A23).

Although these methods have only 25- 44% of the information in common, 33-50% of the

factors they share are ranked the same in degree of influence on the final outcome (Tables C6

and C7, simplified below).

63



H M L H M L H M L

Aquatic/Finfish Habitat 0.38 0.15 0.27 0.44 0.25 0.33 0.62 0.62 0.64



H M L H M L H M L

Aquatic/Finfish Habitat 0.80 0.50 0 0.50 0.50 0.33 0.25 0.25 0.29

64

6.0 CONCLUSIONS / MANAGEMENT IMPLICATIONS

The WET II, VIMS Technique and New Hampshire Method all differ in the total number of

factors they use to assess the functions of floodflow alteration, nutrient retention and

transformation, sediment/toxin retention, aquatic/finfish habitat and wildlife habitat. Any two

of the three methods use anywhere from 15-78% of the same type of information (factors)

to predict the probability that a wetland will perform one of these functions. Any two of the

three methods give 0-80% of their common factors, the same degree of influence in

determining a final rating of High, Moderate or Low.

The processes by which the factors were identified and ranked, however, were not simple.

The labelling of factor categories and the ranking of the various factors often called for its

own best professional judgment. The minimum/maximum number of factor categories had

to be decided to obtain the necessary information. Factors were often interdependent. For

example, the extent to which erosion occurs within a wetland depends upon variables such

as soil composition, average rainfall, adjacent gradient or slope and surrounding land use.

When a method asked a question about erosion, it had to be decided which factor category

or categories best represented that type of information.

This study did not attempt to critique the design of the methods themselves. Disagreement

among the three methods in assessing the field sites may also be explained by differences in

how the questions are asked. Although every attempt was made to ensure that similar

questions from each method were being answered as consistently as possible for the same site,

variations may have existed.

The VIMS Technique proved to require the least amount of time to complete. Fewer

questions needed to be answered, primarily because the technique assesses fewer functions

and no socio-cultural values, compared with the other two methods. The corresponding

interpretation keys are simple to use and the final ratings can be determined fairly quickly.

65

(Refer to Appendix D). It may be preferable, however, to alter the layout of the

interpretation keys. Often, it does not require much time and analysis to identify pivotal

questions/factors. Consequently, an evaluator may be able to (sub)consciously bias the

responses and thus the final outcome. Nonetheless, the highest similarity indices for the

nutrient (0.90), sediment (0.55) and aquatic (0.55) functions were shared between the VIMS

and the New Hampshire methods.

The VIMS Technique tends to rate most nontidal wetlands in Virginia's coastal plain (66%)

as High for floodflow alteration ability, 85% as having a Moderate probability of retaining

both nutrients and sediments, 83% of wetlands as having a Low probability of providing

aquatic/finfish habitat, and 41% and 46% as having a High or Moderate probability,

respectively, of providing wildlife habitat (Appendix B).

The format of the New Hampshire Method is even more straightforward than the VIMS

Technique, as shown in Appendix D. The interpretation/evaluation key is built into the

questionnaire and is easy to use. All calculations can be performed on the page. The manual

supplies most of the secondary data needed to evaluate many of the socio-cultural values.

Although specific to the state of New Hampshire, this method could be easily adapted for use

in Virginia. The fact that it was designed for the non-scientist as well as the scientist, makes

it an attractive evaluation/planning tool for almost any concerned/interested individual. As

many agencies continue to experience budget reductions, equipping the public with a "user-

friendly" wetland assessment technique helps to inform others of the valuable and yet

dwindling wetland resource.

The semi-quantitative scheme used to determine the final ratings, lends versatility to this

method. However, calculating the Wetland Value Unit (WVU), by multiplying the Functional

Value Index (FVI) by an acreage value, tends to result in only the larger sites of the data set

receiving High ratings. Small sites consistently appeared to be evaluated as Low. Many

ecologists would argue quality over quantity. There are those who believe that a small "high

66

quality" wetland may be just as valuable as a large "poor quality" wetland. The New

Hampshire Method does not appear to consider this concept.

The WET II technique required the most amount of time to complete. It is very

comprehensive due to the number of functions and values it assesses, and the extensive series

of questions that must be answered to evaluate them. If the technique does, in fact, undergo

modulations to separate the major types of wetlands (palustrine, lacustrine, estuarine, riverine,

marine, etc.), and thereby eliminate the need to answer questions that do not apply to certain

wetlands, then it will be much more efficient to use; hence, more attractive. Despite the

complexity of the interpretation keys, it is the complexity itself, facilitated by the software

package, which helps to create a somewhat "black-box" perspective when evaluating a site.

This promotes a more objective approach to answering the myriad of questions.

Apart from comparing different methods, there are additional reasons why it may be of value

to identify the rating factor(s) which have the greatest influence. If these pivotal factors are

identified, it may be worthwhile to question whether these evaluation methods can be refined.

If a few critical factors are all that are needed to evaluate a wetland, then an even more rapid

evaluation method could be designed.

Table Set D illustrates one way in which the field data from this study may be organized to

offer management information at the landscape level. Due to the general inconsistencies from

using more than one method to evaluate a site, obtaining this kind of information would, at

present, have to be restricted to the use of only one method. In addition, diversity among

wetland classes would have to be minimized in order to make the necessary generalizations.

Nevertheless, if a matrix could be established, such as the example shown here, a wetland

identified by the National Wetlands Inventory could be evaluated without a field visit, based

solely upon its position in the landscape. The accuracy of the evaluation method, however,

would have to be verified if such a management matrix were to be reliable.

67

Table Dl: Landscape Management Information - Floodflow Alteration

WetlandClass

First-Order Stream Higher Order Stream Isolated


PFOIA(3 sites)

H/M H/L H - - - - - -

PFOIC (4 sites) H H H M M H H H M

PFOIE(2 sites) - - - M H/L H - - -

PEMIE (2 sites) - - - - - - H H H/M

where H, M, L - High, Moderate, Low NH - FVI (not WVU) final ratings

Table D2: Landscape Management Information - Nutrient Retention/Transformation

WetlandClass



PFOIA L M M - - - - - -

PFOIC L M M L M M H M M

PFOIE - - - H MIL M - - -

PEMIE - - - - - - H M M

Table D3: Landscape Management Information - Sediment/Toxin Retention

WetlandClass



PFOIA L M M - - - - - -

PFOIC L M M H M M H M L

PFOIE - - - L M/L M - - -

PEMIE - - - - - - H M L

68

Table D4: Landscape Management Information - Aquatic/Finflsh Habitat

WetlandClass



PFOIA M/L L M/L - - - - - -

PFOIC L L L L H H M L L

PFOIE - - - L H M - - -

PEMIE - - - - - - M L L

Table D5: Landscape Management Information ■ Wildlife Habitat

WetlandClass



PFOIA H/M M M - - - - - -

PFOIC H L M H M H H/M H/M M

PFOIE - - - H H/M H - - -

PEMIE - - - - - - H H M

Despite the number of similarities among the three wetland evaluation methods, many more

differences exist. The methods differ in the total amount of information required to evaluate

each of the five functions, and the importance (degree of influence) of this information varies

among the assessment techniques. The interpretation of the current wetland science into a

formal planning/management tool is anything but straightforward. Even when supported by

the literature, consensus about which are the critical factors necessary to predict the

probability that a wetland will perform a function, does not guarantee consistent application

of the information. Consequently, applying science in the design of management tools such

as wetland assessment techniques, is a challenging and ever-changing process.

69

APPENDIX A: FIELD RESULTS

Table A l: Wetland Site 1 - PSS1/FQ4C (Tastine Swamp, King & Queen County^Function WET VIMS NH

Floodflow Alteration M M H (L)

Nutrient Retention/Transformation L (H) M M(L)

Sediment/Toxin Retention L (H) M M (L)

Aquatic/Finfish Habitat L H H (L)

Wildlife Habitat H M H (L)where H , M, L - High, Moderate, Low (WET) - opportunity (vs. effectiveness) (NH) - multiplied by acreage and grouped by stream order

Table A2: Wetland Site 2 - PFOIC (Tastine Swamp, King & Queen County)Function WET VIMS NH

Floodflow Alteration M M H (L)

Nutrient Retention/Transformation L (H) M M (L)

Sediment/Toxin Retention H M M(L)

Aquatic/Finfish Habitat L H H (L)

Wildlife Habitat H M H (L)

Table A3: Wetland Site 3 - PSS/EMlEb (Tastine Swamp, King & Queen County Function WET VIMS NH

Floodflow Alteration M H H

Nutrient Retention/Transformation M (H) M M (H)

Sediment/Toxin Retention H M H

Aquatic/Finfish Habitat L H M (L)

Wildlife Habitat H H H

Table A4: Wetland Site 4 - PSS/FOlEb (Tastine Swamp, King & Queen County'Function WET VIMS NH

Floodflow Alteration M H H

Nutrient Retention/Transformation L (H) M M (H)

Sediment/Toxin Retention L(H ) M H

Aquatic/Finfish Habitat L H H (M)


71

Table A5: Wetland Site 5 - PEMlFh/PUBHh (Tastine Swamp, King & Queen Co/Function WET VIMS NH

Floodflow Alteration H (M) H H (L)

Nutrient Retention/Transformation H M M (L)

Sediment/Toxin Retention H M M (L)

Aquatic/Finfish Habitat M H M (H)

Wildlife Habitat H H H (L)

Table A6: Wetland Site 6 - PFOIA (Tastine Swamp, King & Queen County)Function WET VIMS NH

Floodflow Alteration M L H (L)



Aquatic/Finfish Habitat L L M (L)

Wildlife Habitat M M M (L)

Table A7: Wetland Site 7 - PSSl/UBFb (Tastine Swamp, King & Queen County]Function WET VIMS NH


Nutrient Retention/Transformation H M M


Aquatic/Finfish Habitat M H H (L)

Wildlife Habitat H H H (M)

Table A8: Wetland Site 8 - PFOIA (Corbin Creek, King & Queen County)Function WET VIMS NH


Nutrient Retention/Transformation L (H) M M

Sediment/Toxin Retention L (H) M M

Aquatic/Finfish Habitat L L M(L)

Wildlife Habitat H M M

72

Table A9: Wetland Site 9 - PUBHh (Glebe Swamp, King & Queen County)Function WET VIMS NH

Floodflow Alteration L (M) H H

Nutrient Retention/Transformation L (H) M H

Sediment/Toxin Retention H M M (H)

Aquatic/Finfish Habitat L H M (H)


Table A10: Wetland Site 10 - PFOIC (West Point High School, King William Co.)Function WET VIMS NH




Aquatic/Finfish Habitat L L L

Wildlife Habitat H L M

Table A ll: Wetland Site 11 - PFOIA (Church of the Nazarene, King William Co.]

Function WET VIMS NH

Floodflow Alteration H (M) H H

Nutrient Retention/Transformation L M M (H)

Sediment/Toxin Retention L (H) M M (H)

Aquatic/Finfish Habitat M L L

Wildlife Habitat M M M (H)

Table A12: Wetland Site 12 - PFOIE (Mill Creek, City of Williamsburg)Function WET VIMS NH

Floodflow Alteration M (H) H H

Nutrient Retention/Transformation H M M (H)

Sediment/Toxin Retention L (H) M M (H)

Aquatic/Finfish Habitat L H M

Wildlife Habitat H M H

73

Table A13: Wetland Site 13 - PFOIC (Colonial National Historical Park, York Co.)Function WET VIMS NH

Floodflow Alteration H (M) H M (L)

Nutrient Retention/Transformation H (L) M M (L)

Sediment/Toxin Retention H (L) M L


Wildlife Habitat H H M (L)

Table A14: Wetland Site 14 - PFOIE (Baptist Run, York County)Function WET VIMS NH

Floodflow Alteration M L H (L)

Nutrient Retention/Transformation H(L) L M (L)

Sediment/Toxin Retention L (M) L M (L)


Wildlife Habitat H H H (L)

Table A15: Wetland Site 15 - PFOIC (Shiping Light Church, City of Newport News]Function WET VIMS NH


Nutrient Retention/Transformation H (L) M M (L)

Sediment/Toxin Retention H M L


Wildlife Habitat M M M (L)

Table A16: Wetland Site 16 - PFQ5Fh (Newport News Park, City of Newport NewsFunction WET VIMS NH

Floodflow Alteration H (M) H L

Nutrient Retention/Transformation L (M) M M (L)

Sediment/Toxin Retention H M L

Aquatic/Finfish Habitat L H M


74

Table A17: Wetland Site 17 - PFOlEh (Newport News Park, City of Newport NewsFunction WET VIMS NH

Floodflow Alteration H (M) H L

Nutrient Retention/Transformation H(L) M M (L)




Table A18: Wetland Site 18 - PEMIE (Newport News Park, York County)Function WET VIMS NH


Nutrient Retention/Transformation H (L) M M (H)

Sediment/Toxin Retention H (L) M L (H)


Wildlife Habitat H H M (H)

Table A19: Wetland Site 19 - PSS1E (Newport News Park, York County)Function WET VIMS NH


Nutrient Retention/Transformation H (L) M M (H)

Sediment/Toxin Retention H (L) M L (H)


Wildlife Habitat H M M (H)

Table A20: Wetland Site 20 - PEMIE (Newport News Park, York County)Function WET VIMS NH


Nutrient Retention/Transformation H (L) M M

Sediment/Toxin Retention H (L) M L


Wildlife Habitat H H M

75

APPENDIX B: WEIGHTING THE FACTORS

Tabl

e Bl

: W

etla

nd

Eval

uatio

n Te

chni

que

- Max

imum

Po

ssib

le W

eight

of

Fact

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nal

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g of

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(H

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oder

ate

(M)

or Lo

w (L

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Floodflow Alteration Effectiveness (FFAE) Key

0.100.100 .1 0

0.10o.io

0.11

[ (10D/E/F-y) ) 1 . 0tidal/estuarine/marine -LOW

ANY of the following:

* \ 3A

[(8.3-=n) and (23=n) ] 0.-S'no permanent outlet and water not artificially removed

(9.2-yor 63.1-y> /.£>unconstricted inlet and constricted outlet or flat hydrograph

[(2.1. 2=y) + (31. 3=n)+(9 . l=y) ] 0 - S S>40 acres aind Zone B < Zone A and constricted outlet

[(2.1. 3=y)+(31. 5=y) + (23=n) ] Q & G>200 acres and Zone A >10% of Zones B and C and water not artificially removed

nAL^Xof the following:

(l) (2.1. l=n)>5 acres

2. (35.1-y)expansive flooding

3. (24.3-=n)soil does not have slow infiltration rate

4. (32A=n or 32E=y or 34.3.1=y)* not permanently flooded or saturated or ponding

(5.) (23-n) fp g p O X tjwater not artificially removed

){C(AU )of the following:

6 ) (2.1.3-y) •>200 acres

2. (24.3-n)soil does not have slow infiltration rate

3. (1.l=y) OR [(22.1.1=y)+(31.6D/E=y)+(12A/B=y)+ (15.1 A=y or 15.2-y)]

"dry" region or E>P OR flow suggested and Zone B and C >60% eB and forested or scrub-shrub and channel flow intercepted by large clumps or

. spreads out over a wide area(4.) (23-n)

water not artificially removed

(22.1. l=y) 0 J 6 * ?flow is suggested

T

Continued --

-HIGH

-HIGH

— FFAE List B -~FFAE List A

WET 2.0

FFAE Key (Cont.)

FFAE List A

K

0 X > & * AOS1*-

f the following:

1. (32A=y) 0 . 1 0 ^permanently flooded

2. (2.1.3=n) Ox 10D .< & * <200 acres

3. [ (1l=y) or (9.l=n+9.2=n)]fringe/island situation or outlet not constricted

4. [ (1. l=n) or (2.1. l=y) ]ot a "dry" region or E<P or <5 acres

■LOW

■MODERATE

FFAE L i s t B

/^LL/f the following:(12A+B=n)

not forested or scrub-shrub2. (31.6A=y or 31.6E=y)

<60% of Zones B and C is eB3. (15.2=n)

instream vegetation-water interspersion not great

LOW

MODERATE

— End —

Tab

le B

(Exa

mpl

e):

VIM

S Te

chni

que

- Fac

tors

Used

in

Floo

dflow

Al

tera

tion

Rat

ings

CNcn

T3 60

60

’O 3CN

T3cn

cn

x:O h

60C/3

T3

CN

Total

Num

ber

of Co

mbi

natio

ns t

o ob

tain

each

Fina

l Ra

ting:

H

- 12

, M - 3

, L -3

(66%

, 17

%,

17%

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m

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cn

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XI

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Table B3: New Hampshire Method - Ranking of Factors in Floodflow Alteration____________ Ratings________________________________________________________

Factors Ranking

Area of wetland in acres 3

Area of watershed above the outlet of the wetland in acres 2

Wetland Control Length (WCL) in feet [outlet diameter] 1

Functional Value Index (FVI) for Flood Control Potential FVI



85

Table B3.1: New Hampshire Method - Sensitivity Analysis of Floodflow AlterationFactors

PercentIncrease



0 1 . 0 0 0.600 2 . 0 0 0.600 2 . 0 0 0.6001 1 .0 1 0.600 2 . 0 2 0.600 2 . 0 2 0.6005 1.05 0.600 2 . 1 0 0.610 2 . 1 0 0.575

1 0 1 . 1 0 0.600 2 . 2 0 0.620 2 . 2 0 0.55050 1.50 0.600 3.00 0.700 3.00 0.435

1 0 0 2 . 0 0 0.600 4.00 0.800 4.00 0.3502 0 0 3.00 0.600 6 . 0 0 0.900 6 . 0 0 0.225

500 6 . 0 0 0.600 1 2 . 0 0 0.800 1 2 . 0 0 0.055

PercentIncrease


Area FVIOutlet

Diameter FVI

0 2 0 . 0 0 1 . 0 0 50.00 1 . 0 0 4.00 1 . 0 0

1 2 0 . 2 0 1 . 0 0 50.50 1 . 0 0 4.04 1 . 0 0

5 2 1 . 0 0 1 . 0 0 52.50 1 . 0 0 4.20 1 . 0 0

1 0 2 2 . 0 0 1 . 0 0 55.00 1 . 0 0 4.40 1 . 0 0

50 30.00 1 . 0 0 75.00 1 . 0 0 6 . 0 0 1 . 0 0

1 0 0 40.00 1 . 0 0 1 0 0 . 0 0 1 . 0 0 8 . 0 0 1 . 0 0

2 0 0 60.00 1 . 0 0 150.00 1 . 0 0 1 2 . 0 0 1 . 0 0

500 1 2 0 . 0 0 1 . 0 0 300.00 1 . 0 0 24.00 0.81

PercentIncrease



0 1 0 . 0 0 1 . 0 0 1 0 0 1 . 0 0 3.00 1 . 0 0

1 1 0 . 1 0 1 . 0 0 1 0 1 1 . 0 0 3.03 1 . 0 0

5 10.50 1 . 0 0 105 1 . 0 0 3.15 1 . 0 0

1 0 1 1 . 0 0 1 . 0 0 1 1 0 1 . 0 0 3.30 1 . 0 0

50 15.00 1 . 0 0 150 1 . 0 0 4.50 1 . 0 0

1 0 0 2 0 . 0 0 1 . 0 0 2 0 0 1 . 0 0 6 . 0 0 1 . 0 0

2 0 0 30.00 1 . 0 0 300 1 . 0 0 9.00 0.94

500 60.00 1 . 0 0 600 0.95 18.00 0.71

86

Tabl

e B4

: W

etla

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Eval

uatio

n Te

chni

que

- Max

imum

Po

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le W

eigh

t of

Fact

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e B5

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S Te

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Table B6: New Hampshire Method - Weight of Factors in Nutrient Retention____________ and Transformation Ratings___________________________________

Factors Weight

Average slope of watershed above wetland:H: >8% M: 3-8% L: <3% 0.0875

Potential sources of excess sediment in the watershed above the wetland:H: extensive areas of active cropland, construction sites, eroding banks, ditches, etc.M: some areas of active cropland, a few construction sites, and similar areas L: land use in watershed predominantly forested, abandoned farmland or undeveloped

0.0875

Potential sources of excess nutrients in watershed above wetland:H: large areas of active cropland, pastureland, or urban land; many dairies/livestock operations, sewage treatment plants/numerous on-site septic systems within 100' of streamM: watershed contains some/few such areas/operations/plants/systems within 100' of streamL: watershed predominantly forested or otherwise undeveloped

0.125

Effective floodwater storage of wetland 0.05

Wetland location in relation to an intermittent or perennial stream or a lake:H: wetland forms a buffer > 50 ft wide between upland and stream or lake M: buffer 20-50 ft wideL: buffer < 20 ft wide or wetland not bordering a stream or lake

0.05


0.05


0.05

Dominant wetland class:H: floating aquatic plants, emergent (marsh), forested, or scrub/shrub L: bogs

0.25

Wetland hydroperiod:H: wetland contains permanently impounded open water > 5 acres M: 0.5-5 acres, OR > 5 acres of wetland flooded or ponded annually L: above criteria not met (saturated or rarely ponded or flooded)

0.25

Functional Value Index (FVI) 1.0



H, M, L - 1.0, 0.5, 0.1

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Table B9: New Hampshire Method - Weight of Factors in Sediment/ToxinRetention Ratings

Factors Weight

Average slope of watershed:H: >8% M: 3-8% L: <3% 0.1

Potential sources of excess sediment in watershed:H: extensive areas of active cropland, construction sites, eroding road banks, ditches, and similar areasM: some areas of active cropland, a few construction sites, and similar areas L: land use in watershed predominantly forested, abandoned farmland or undeveloped

0.1

Effective floodwater storage of wetlands 0.2

Wetland location in relation to an intermittent or perennial stream or a lake:H: wetland forms a buffer > 50 ft wide between upland and stream or lake M: buffer 20-50 ft wideL: buffer < 20 ft wide or wetland not bordering stream or lake

0.2


0.2


0.2




H, M, L -1 .0 , 0.5, 0.1

103

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Table B12a: New Hampshire Method - Weight of Factors in Aquatic/Finfish ____________ Habitat Ratings for Streams and Rivers_____________________

Factors Weight

Dominant land use in watershed: H: woodland, wetland or abandoned farmlandM: active farmland or rural residential L: urban and heavily developed suburban areas

0.125

Water quality of the watercourse associated with the wetland:H: minimal pollution; actual water quality meets or exceeds Class A or B standardsM: moderate pollution; actual water quality is below Class B standards

0.125

Barriers to anadromous fish ([beaver] dams, water falls, road crossings, etc.):H: no barrier(s), or if present equipped with provisions for fish passage, OR waterbody is beyond range of anadromous fishL: artificial barrier(s) without provision for fish passage, AND river/stream is within range of anadromous fish

0.125

Stream width (bank to bank): H: > 50 ft M: 2-50 ft L: < 2 ft 0.125

Available shade:H: woodland, scrubland or other tall vegetation provides > 50% cover (shade) to streamM: portions of stream bank unvegetated, OR vegetation too low (< 6') (25- 50% cover)L: major portions of stream bank veg. < 6', OR unvegetated (< 25% cover)

0.125

Physical character of stream channel associated with wetland:H: stream in natural channel, either a meandering low grade (< 0.2%) stream, OR moderate to high (0.2% or higher) gradient stream with pools + riffles M: portions of stream recently modified, OR stream formerly channelized but has regained some natural channel features (meandering, regrowth of instream vegetation, addition of cover objects)L: stream has recently been channelized, OR stream is confined in a nonvegetated chute or pipe

0.125

Abundance of cover objects:H: > 70% of water area contains cover objects (logs, undercut banks, submerged vegetation)M: 30-70% of water area contains cover objects L: < 30% of water area contains cover objects

0.125

Spawning areas:H: low gradient, slow moving stream with abundant areas of grass and low emergent vegetation which are flooded for several weeks in spring, OR a medium/high gradient stream with gravel M: moderate amount of spawning areas present L: few spawning areas present

0.125


Area of stream or river associated with wetland (acres) multiplier

Wetland Value Units WVUH, M, L -1 .0 , 0.5, 0.1

110

Table B12b: New Hampshire Method - Weight of Factors in Aquatic/FinfishHabitat Ratings for Lakes and Ponds

Factors Weight

Dominant land use in watershed above wetland:H: woodland, wetland or abandoned farmland M: active farmland or rural residential L: urban and heavily developed suburban areas

0.167

Water quality of pond or lake associated with wetland:H: minimal pollution; actual water quality meets or exceeds Class A or B standardsM: moderate pollution; actual water quality is below Class B standards

0.167

Barriers to anadromous fish (dams, beaver dams, water falls, road crossings, etc.):H: no barrier(s) present, or if present equipped with fish ladders or other provisions for fish passage, OR waterbody is beyond the range of anadromous fishL: artificial barrier(s) present without provision for fish passage, AND lake/pond is within range of anadromous fish

0.167

Total area of pond or lake, including areas of rooted, submerged and emergent vegetation:

H: >100 acres M: 10-100 acres L: < 10 acres

0.167

Abundance of cover objects:H: > 70% of area visible from shore contains cover objects (submerged logs, rocks, etc.)M: 30-70% of area visible from shore contains cover objects L: < 30% of area visible from shore contains cover objects

0.167

Percent of pond or lake having rooted submerged or emergent vegetation: H: 15-50%L: > 50% or < 15%

0.167


Area of pond or lake associated with wetland (acres) multiplier

W etland Value Units WVU

H, M, L -1 .0 , 0.5, 0.1

111

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Tabl

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4.1

(Con

t):

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S Te

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- Fac

tors

Us

ed

in W

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e H

abita

t R

atin

gs mfi'Oad3So

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73X

(H2

X

<N m in WD73 *j3 .S *fa IX

inb£

(N cn

Total

Num

ber

of Co

mbi

natio

ns t

o ob

tain

each

Fi

nal

Ratin

g:

H - 9

9, M

-111

, L

- 33

(41%

, 46

%,

13%

)

Tabl

e B1

4.2:

VI

MS

Tech

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e - N

umbe

r of

High

(H

), M

oder

ate

(M)

and

Low

(L)

Res

pons

es t

hat

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n a

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l Ra

ting

of

Hig

h, M

oder

ate

or Lo

w for

W

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ab

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t__

____

____

____

____

____

____

____

____

____

____

____

____

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o

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COCO

COCO

COCO

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OS

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Table B15: New Hampshire Method - Weight of Factors in Wildlife Habitat____________ Ratings___________________________________________________

Factors Weight

Percent of wetland having very poorly drained soils or Hydric A soils and/or open water: H: >50% M: 25-50% L: <25% 0.0083

Dominant land use zoning of WETLAND: H: agriculture, forestry/open spaceM: rural residential L: industrial, dense residential

0.0083

Ratio of number of occupied buildings within 500 ft of wetland edge to total area of wetland (acres): H: <0.10 M: 0.10-0.50 L: >0.50 0.0083

Percent of original wetland filled:H: < 10% M: 10-50% L: > 50%

0.0083

Percent of wetland edge bordered by a buffer of woodland or idle land at least 500 ft in width: H: >80% M: 20-80% L: <20%

0.0083

Level of human activity WITHIN WETLAND (litter, bike trails, roads, residences) H: low level - few trails in use and/or sparse litter M: moderate level - some used trails, roads, etc.L: high level - many trails, roads, etc. within wetland

0.0083

Level of human activity WITHIN UPLAND within 500 ft of the wetland edge as evidenced by litter, bike trails, roads, residences, etc.

H: low level - few trails in use and/or sparse litter M: moderate level - some trails, scattered residences, etc.L: high level - many trails, roads, etc. within upland

0.0083

Percent of wetland plant community presently being altered by mowing, grazing, farming, or other activity. (Include areas now dominated by phragmites or purple loosestrife).

H: < 10% M: 10-50% L: > 50%

0.0083

Percent of wetland being drained for agriculture or other purposes: H: < 10% M: 10-50% L: > 50%

0.0083

Public roads and/or railroad crossings per 500 ft: H: 0 M: 1 L: > 2 0.0083

Long-term stability:H: wetland appears to be naturally occurring, not impounded by dam/dike M: wetland appears to be somewhat dependent on artificial diking by dam, road, fill, etc.

0.0083

Area of shallow permanent open water (< 6' deep) including streams in or adjacent to wetland:

H: > 3 acres M: 0.5-3 acres L: < 0.5 acre0.1

Water quality of the watercourse, pond or lake associated with the wetland: H: minimal pollution; water quality > Class A or B standards M: moderate pollution; water quality is below Class B standards

0.1083

121

Wetland diversity: H: 3 or more wetland classesM: 2 wetland classes L: one wetland class

0.1

Dominant wetland class: H: emergent marsh and/or shallow open waterM: forested and/or scrub-shrub wetland L: scrub-shrub saturated (bog) or wet meadow

0.1

Interspersion of vegetation classes and/or open water:H: at least 2 wetland classes highly interspersed; areas of each class scattered within wetland like a patchwork quilt M: moderate interspersion of wetland classesL: low degree of interspersion; each wetland class is more or less contiguous and separate from the other classes

0.1

Wetland juxtaposition:H: wetland connected to other wetlands within 1 mile radius by perennial stream/lakeM: wetland connected to other wetlands within 1-3 mile radius by perennial stream/lake, OR other unconnected wetlands exist within 1 mile radius L: wetland not hydrologically connected to other wetlands within 3 miles and no other unconnected wetlands within 1 mile

0.1

Islands/inclusions of upland within wetland: H: > 2 M: 1 L: 0 0.1

Wildlife access to other wetlands (overland). Travel lanes should be 50-100 feet wide: H: free access along well vegetated stream corridor, woodland/lakeshore M: access partially blocked by roads, urban areas or other obstructions L: access blocked by roads, urban areas or other obstructions

0.1

Percent of wetland edge bordered by upland wildlife habitat (woodland, farmland) at least 500 ft in width: H: > 40% M: 10-40% L: < 10%

0.1



Wetland Value Units wvuH, M, L - 1.0, 0.5, 0.1

122

APPENDIX C: COMPARATIVE RANKING OF FACTORS

Tabl

e C

l: Fl

oodf

low

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ratio

n -

Fact

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trien

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and

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atio

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ethod

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Tabl

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: Se

dim

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Tabl

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Meth

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APPENDIX D: EXAMPLES OF QUESTIONS / INTERPRETATION KEYS FROM EACH OF THE THREE METHODS

WETLANDS RESEARCH PROGRAM

TECHNICAL REPORT Y-87-

WETLAND EVALUATION TECHNIQUE (WETVolume II

by

Paul R. Adamus

Eco-Analysts, Inc.

and

ARA, Inc.Augusta, Maine 04330

and

Ellis J. Clairain, Jr., Daniel R. Smith, Richard E. Young

Environmental Laboratory

DEPARTMENT OF THE ARMY Waterways Experiment Station, Corps of Engineers

PO Box 631, Vicksburg, Mississippi 39180-0631

©IPEIMTDOGML DEMFT

April 1987

Prepared for DEPARTMENT OF THE ARMY US Army Corps of Engineers Washington, DC 20314-1000

and US Department of Transportation Federal Highway Administration

Washington, DC 20590

WET 2.0

15. VEGETATION/WATER INTERSPERSION

(Answer "I" to all of 15.1 if the wetland system is riverine. Answer "Yn to 15.1A if surface water is absent.) Does the horizontal pattern of erect vegetation in Zone B (Figure 15) consist of:

15.1A -Relatively few, continuous areas supporting vegetation with little or no interspersion with channels, pools, or flats (Figure 16)?

15. IB A condition intermediate between 15.1A and 15.1C.?

15.1C A mosaic of relatively small patches of vegetation (i.e., none smaller in diameter than two times the height of the prevailing vegetation) interspersed with pools, channels, or flats (Figure 16)?

15.2 (Answer "I" if channel or tidal flow never occurs in the AA/IA.) Is either of the following conditions present in that portion of the AA/IA having measurable flow?

(a) In channel situations, vegetation in Zone B consists mainly of persistent emergent distributed in the mosaic pattern described in 15.1C.

(b) Under average flow conditions, water enters the AA/IA in a channel and then spreads out over a wide area.

OR OR

B.

OROR

Figure 16. Examples of low and high vegetation/water interspersion (Note:In this figure, Part A exemplifies low vegetation/water interspersion (Question 15.1A = ,rY"), and Part B exemplifies high vegetation water interspersion (Question 15.1C = "Y").)

WET 2.0

Sediment/Toxicant Retention Effectiveness (S/TRE) Key

ANY of the following:

1. (9.2=y)unconstricted inlet and constricted outlet

2. (8.3=n and 8.4=n)no outlet

3. [(36.1.2=y) and ((22.3 = n) or (64 = n)J]substantial erect vegetation in Zones A and B and no evidence of erosion on aerial photos or inlet

HIGH

\ FANY of the following:

1. [(19.1A=n) + (43A/B/C/D/E=y) + (31.4=n) + (31.6A=y)]not sheltered and water depth <40 in. and sB<oB and B and C is 0% eB

2. (19.lB=y)unsheltered

(28 = y )

direct alteration evident

T3.

4. [(7=n) or (41.2=y)] high velocity

LOW

[(7=y) or (4l.l=y) or (42.1.1=y)] low velocity

AND ANY of the following:

1. (34.3.l=y)dike or dam downslope creates flooding

2. [ (22.3 = n) + (31.6A=n)+(12A/B/Da=y)+(22.2=y or 19.2=y}]no long-term erosion and B and C is not 0% eB and forested/scrub-shrub or persistent emergent and actively accreting delta part of AA

HIGH

.BOTH of the following:

1.

2 .

[(7=y) or (4l.l=y) or (3l.l=n)]low velocity or Zone C > Zones A and B

(45E+F+G=n)substrate not bedrock, rubble or cobble-gravel

S/TRE List A

S/TRE List B

— Continued —

WET 2.0

S/TRE Key (Cont.)

S/TRE List A

BOTH of the following:

1 . (13A/B/Da=y)part forested, scrub-shrub or persistent emergent

2. [ (3 6.1.l=n) + (25.2A=y) ] OR [(36.2.1 = n) + (25.2B=y) + (7=y)+ (9. l=y)]

erect vegetation in Zones A+B >20 ft wide and sediment sourceis overland flow OR Zone eB usually >20 ft wide and sediment source is channel flow and low velocity and constricted outlet

T-----MODERATE

OR ALL of the following:

1 . (9. l=y) constricted outlet

rS/TRE List B

2. (10D/E=y)tidal riverine or estuarine

3. (48B=y) or [(1.2=y)+ (13A/B/Da=y)]salinity=0.5-5.0 ppt or high rain-erosivity factor and forested,scrub—shrub or persistent emergent

S/TRE List B

ALL of the following;..

1. (31. 4=y)Zone sB > Zones oB and C

2. (10D/E/F=y)marine, estuarine or tidal riverine

3. (48B=y)salinity = 0.5-5.0 ppt

OR ALL of the following:

1. (10C/D=y)riverine

2. (35.l=y)expanded flooding or flow

3. [ (15.2=y) or (31.4=y)]good interspersion or Zone sB > Zones oB and C

4. (9.1=y) or (31.1=n) or ((49.1. 2=y) +(49.1.l=y)]

constricted outlet or Zones A+B>C or pools/riffles

— End —

A T echnique for the Functional A ssessm en t o f N on tid a l W etlands in the Coastal P lain

of V irginia

by

Julie Go Bradshaw

Special Report No. 315 in A pplied M arine Science and

Ocean Engineering

Virginia Institute of M arine Science School of M arine Science

College of W illiam and M ary G loucester Point, Virginia 23062

Decem ber 1991

Flood storage and flood flow m odification

Factor ratings

Factor 1: Proportion of 2 year, 24 hour storm volum e stored in wetland

High: >25% Low: <25%

Factor 2: W atershed slope

High: >8% Moderate: 3-8% Low: <3%

Factor 3: R etention/detention of storm w ater w ithin wetland (priority: physical characteristics; secondary: vegetation characteristics

High: detention time likely to be great due to significant constriction at outlet,very sinuous channels within the wetland, ponding w ithin wetland, high vegetation density w ithin the wetland (stem s/acre), a n d /o r the wetland plants have rigid stem s

Moderate: detention time likely to be intermediate

Low: detention time likely to be short due to lack of constriction at the wetlandoutlet, channelized flow through the wetland, low vegetation density within the wetland, a n d /o r lack of vegetation with rigid stems.

In terpretation Key

1. Are either Factor 1 or Factor 3 HIGH?

Y—HIGH N —go to 2.

2. Is Factor 3 MODERATE?

Y—MODERATE N—go to 3

3. Are at least 2 of the 3 Factors MODERATE or HIGH?

Y—MODERATE N —LOW

A-7

NHDES - WRD - 1991 - 3

METHOD FOR THE COMPARATIVE EVALUATION OF NONTIDAL WETLANDS IN NEW HAMPSHIRE

Based on the "Method for the Evaluation of Inland Wetlands in Connecticut"(Ammann, et al., 1986)

The preparation o f this manual was supported by the Audubon Society o f New Hampshire Wetlands Protection Project and the USDA Soil Conservation Service.

This manual is published by the New Hampshire Department of Environmental Services6 Hazen Drive

Concord, NH 03301

Prepared for the Assistance of New Hampshire Towns by:

Alan P. Ammann, Ph.D., Principal Author U.S.D.A. Soil Conservation Service

Amanda Lindley Stone Audubon Society of New Hampshire

Robert W. Varney, Commissioner John Dabuliewicz, Assistant Commissioner

Printed on Recycled Paper

MARCH 1991

NHDES

Wetland Name/Code:

NEEDED FOR THIS EVALUATION: Functional Value 10NUTRIENT A TTENUA TION• USGS topographic map

• Land use map or recent aerial photographs• Knowledge or familiarity with the area regarding extent and type of current development• Ability to delineate a watershed (See Appendix E)

A BEvaluation Computations Questions or Actual Value

C D Evaluation Functional Value

Criteria Index (FVI)

PART A - OPPORTUNITY FOR NUTRIENT ATTENUATIONALL QUESTIONS TO BE ANSWERED IN THE OFFICE:1. Opportunity for sediment

trapping.Average FVI for Part A of FV 9

2. Potential sources of excess nutrients in watershed above wetland.

a. Large areas of active cropland, 1 0 pastureland, or urban land.Many dairies or other livestock operations, sewage treatment plants, or numerous on-site septic systems within 100 feet of stream

b. Watershed contains some 0 5 areas of active cropland, pastureland, or urban land. Afew dairies or other livestock operations or a few on-site septic systems within 100 feet of the stream

c. Watershed predominantly 0.1 forested or otherwise undeveloped

AVERAGE FVI FOR FUNCTIONAL VALUE 10. PART A = Average of Column D for Pari A =

PART B - OVERALL POTENTIAL FOR NUTRIENT ATTENUATION

QUESTIONS TO ANSWER IN THE OFFICE:1. Opportunity for nutrient

attenuation.Average FVI for Part A (above)

2. Overall potential for sediment trapping in the wetland.

Average FVI for Part B of FV 9

QUESTIONS TO ANSWER IN THE FIELD:

3. Dominant wetland class. (Refer to Question V.2.4).

a. Floating aquatic plants, emergent (marsh), forested, or scrub/shrub, except bogs

b. Bogs °-1

Continued on next page..,

Wetland Name/Code:

Functional Value 10 NUTRIENT A TTENUA TION (continued)

AEvaluationQuestions

Computations or Actual Value

CEvaluation

Criteria

DFunctional Value

Index (FVI)

4. Wetland hydroperiod. a. Wetland contains perma- 1.0 nently impounded openwater > 5 acres in size

b. Wetland contains perma- 0.5 nently impounded openwater from 0.5 to 5 acres in size, OR more than 5 acres of the wetland are flooded or ponded annually during a portion of the growing season

c. Above criteria are not met 0.1 (e.g. the wetland has predominantly saturatedsoil conditions and is rarely ponded or flooded during the growing season.)

AVERAGE FVI FOR FUNCTIO NAL VALUE 10, PART B = Average of Column D for Part B = = Average FVI forNutrient Attenuation.

EVALUATION AREA FOR FUNCTIONAL VALUE 10 = Total area of wetland = __________________ acres.

REFERENCES

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Albrecht, V.S. 1991. Are all wetlands created equal?: Bring standards back to reality. National Wetlands Newsletter, Sept./Oct. 13(5): 6-7.

Amacher, G.S., Brazee, R.J., Bulkley, J.W. and R.A. Moll. 1988. Interdisciplinary Approach to Valuation of Michigan Coastal Wetlands. Rep. U.S. Geol. Surv. Water Resour. Div., 112 pp.

Adamus, P.R., Stockwell, L.T., Clairain, E.J., Jr., Smith, R.D. and R.E. Young. 1987. Wetland Evaluation Technique (WET)Vol. II. Methodology. U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS. 206 pp. plus appendices.

Adamus, P.R., Daniel, R.D. and T. Muir. 1990. Manual for Assessment of Bottomland Hardwood Functions. U.S. Environ. Protection Agency, Office of Wetlands Protection. Washington, D.C., USA. 72 pp.

Ainslie, W.B. 1994. Rapid wetland functional assessment: Its role and utility in the regulatory arena. Water, Air and Soil Pollution 77: 433-444.

Ammann, A.P., Franzen, R.W. and J.L. Johnson. 1986 and 1991. Method for the Evaluation of Inland Wetlands in Connecticut: A Watershed Approach. DEP Bulletin No. 9. Connecticut Department of Environmental Protection, Hartford, CT. pp. (Incomplete citation).

Ammann, A.P. and A.L. Stone. 1991. Method for the Comparative Evaluation of Nontidal Wetlands in New Hampshire. New Hampshire Department of Environmental Services, Concord, NH. NHDES-WRD-1991-3.

Bardecki, M.J. 1984a. What value wetlands? J. Soil and Water Conserv. 39(3): 166-169.

Bond, W.K., Cox, K.W., Heberlein, T., Manning, E.W., Witty, D.R. and D.A. Young. 1992. Wetland Evaluation Guide. Final Report of the Wetlands are not Wastelands Project. Sustaining Wetlands Issues Paper, No. 1992-1. North American Wetlands Conservation Council (Canada), Ottawa, Ontario. 121 pp.

Boyt, F.L., Bayley, S.E. and J. Zoltek, Jr. 1976. Removal of nutrients from treated municipal wastewater by wetland vegetation. J. Water Poll. Cont. Fed. 49: 789-799.

Bradshaw, J.G. 1991. A Technique for the Functional Assessment of Nontidal Wetlands in

139

the Coastal Plain of Virginia. Special Report No. 315 in Applied Marine Science and Ocean Engineering. Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, Gloucester Point, VA.

Bradshaw, J.G. Personal communication, June 1, 1995. Marine Scientist, Virginia Institute of Marine Science, Gloucester Point, VA 23062.

Brinson, M.M. 1993. A Hydrogeomorphic Classification for Wetlands. Draft. Prepared for Office, Chief of Engineer, U.S. Army. Washington, D.C. 81 pp. plus field data sheets.

Brooks, R.P. 1989. An overview of ecological functions and economic values of wetlands, pp. 11-20 In: Majumdar, S.K., R.P. Brooks, F.J. Brenner and R.W. Tiner, Jr. (eds). Wetlands Ecology and Conservation: Emphasis in Pennsylvania. 395 pp.

Brown, M. 1986. Assessing wetland values in landscapes dominated by humanity, pp. 49- 54. In: Kusler, J.A. and P. Riexinger. Proc. National Wetland AssessmentSymposium. June 17-20, 1985, Portland, Maine. Assn. State Wetland Managers, Chester, VT. 331 pp.

Burke, D.G., Meyers, E.J., Tiner, R.W., Jr. and H. Groman. 1988. Protecting Nontidal Wetlands. American Planning Association, Chicago, IL. 76 pp.

Cable, T.T., Brack, V. and V.R. Holmes. 1989. Simplified method for wetland habitat assessment. Environ. Mgmt. 13(2): 207-213.

Carter, V., Bedinger, M.S., Novitzki, R.P. and W.O. Wilen. 1979. pp. 334-376 In: Greeson, P.E., Clark, J.R. and J.E. Clark (eds). Wetland Functions and Values: The State of Our Understanding. American Water Resources Assoc.

Chaun, M. 1993. Plowing through the muck: A review of wetland assessment/evaluation methods. Wetlands Program Technical Report, November 1993, No. 93-11.

Cobum, C.B., Jr. 1993. An Overview of Approaches to Evaluating and Regulating Wetlands in the States. Department of Biology, Tennessee Technological University. 162 pp.

Cooper, J.R., Gilliam, J.W., Daniels, R.B. and W.P. Robarge. 1987. Riparian areas as filters for agricultural sediment. Soil Sci. Soc. Am. J. 51: 416-420.

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VITA

Melissa Claire Chaun

Bom in Vancouver, British Columbia, Canada on April 11, 1969. Graduated from Crofton House School, Vancouver, B.C. in 1987. Received a B.Sc. in Biology (Ecology) from McGill University, Montreal, Quebec in 1991. Entered the Master's Program at the Virginia Institute of Marine Science, School of Marine Science, The College of William and Mary in August 1992.

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Documents

A Comparison of Three Wetland Evaluation Methods in their