Applied Wetlands Science - Chapter 2 docx

Department of Agriculture Natural Resources Conservation Service Soil Surveys and the Hydric Soils of the United States ListComparison and CorroborationAerial Photographs U.S.. Geologica

Tammi, Carl E “Wetland Identification and Delineation”

Applied Wetlands Science and Technology

Editor Donald M Kent

Boca Raton: CRC Press LLC,2001

CHAPTER 2 Wetland Identification and DelineationCarl E Tammi

CONTENTS

Off-Site Wetland IdentificationIdentification ResourcesInterpreting Resources

U.S Geological Survey (USGS) Topographic MapsU.S Fish and Wildlife Service (USFWS) National Wetland Inventory Maps

U.S Department of Agriculture Natural Resources Conservation Service Soil Surveys and the Hydric Soils

of the United States ListComparison and CorroborationAerial Photographs

U.S Geological Survey Surficial Geologic MapsIndividual State Wetland Maps

On-Site Wetland DelineationWetland Hydrology

Hydrological Field IndicatorsHydric Soils

Hydric Soil Field IndicatorsHydrophytic Vegetation

Indicators of Hydrophytic VegetationIdentifying and Delineating Wetlands

Undisturbed AreasDisturbed AreasDifficult AreasAids to DelineationReferences

Wetland identification and the science of delineation are regulatory-driven ities that are commonly required in land-use development, planning, exploration, and

activ-a host of relactiv-ated activ-activities involving future site expactiv-ansion Although federactiv-ally mactiv-an-dated wetland regulatory statutes have been in existence for over 25 years, the science

man-of identifying and delineating the extent and types man-of wetlands has been consistentlyevolving As the science has evolved, a greater awareness of the functions and valueswetlands provide has occurred with the resultant development of extensive wetlandidentification and delineation resources within the last 10 years Today, the land-useplanner, wetland scientist, and manager have a range of tools in print, graphic, andelectronic format available to assist in making wetland determinations and defendablejurisdictional delineations Typically, the science of identifying and delineating wet-lands is a two-tiered process An initial office-based off-site assessment is conductedfor identification purposes A legally binding jurisdictional determination requires anon-site field assessment called a wetlands delineation

Identifying the location and determining the areal extent of jurisdictional lands is an important consideration for those involved in land use management,development, remediation, or assessment Today, defining wetland limits and bound-aries is primarily driven by comprehensive federal and, where applicable, state andlocal land-use laws and regulations Section 404 of the Clean Water Act is theprincipal tool that the U.S Army Corps of Engineers and the U.S EnvironmentalProtection Agency use to regulate the discharge of dredged or fill material into waters

wet-of the United States, including wetlands (33 CFR 320–330) At the federal level,wetlands are further defined from a regulatory viewpoint as, “Those areas that areinundated or saturated by surface or groundwater at a frequency and duration suf-ficient to support, and that under normal circumstances do support a prevalence ofvegetation typically adapted for life in saturated soil conditions Wetlands generallyinclude swamps, marshes, bogs, and similar areas” (33 CFR 328.3)

In identifying and delineating federal jurisdiction wetlands, three essential nical criteria or factors are applied: the presence of wetlands hydrology throughsurficial or groundwater; a prevalence of wetland vegetation (hydrophytes) thattypically has specialized morphological and physiological adaptations to toleratesaturated or inundated conditions; and wetland soils (hydric soils), which in theirundrained condition exhibit characteristics of somewhat poorly drained, poorlydrained, or very poorly drained soils Other major federal legislation that driveswetland identification includes Section 401 Water Quality Certification (delegated

tech-to the individual states), Section 10 of the Rivers and Harbors Act of 1899 and theNational Environmental Policy Act

Many states have promulgated and adopted wetland protection legislation forinland, and where applicable, coastal wetlands Identification and delineation tech-niques vary slightly from state to state, although most have adopted the principles

of the federal methodology (to be described in greater detail later)

Given the regulatory framework behind wetland protection, it is incumbent uponproject proponents and land-use managers to determine, locate, and identify wetlandresources on a subject parcel Furthermore, it is important to adequately and accu-rately determine the location and approximate areal extent, as well as the predom-inant wetland cover type, early in project planning stages to avoid wetland impacts

and resultant time-consuming permit decisions This action can streamline the mitting process during more advanced stages of project design through avoidanceand minimization of wetland impacts An off-site macroscale wetland determinationmakes a positive or negative wetland determination for a subject parcel, and deter-mines the approximate location of wetland and deepwater areas It also determinesthe approximate areal extent and distribution of wetland and deepwater areas, andthe predominant wetland cover type (Cowardin et al., 1979) Finally, an off-sitemacrosite wetland determination assesses the need for continued analysis andapproximate level of effort associated with any analyses.

per-In some instances, information relative to the potential presence of hydric soils,surficial hydrology, and site disturbance can be determined from off-site wetlanddeterminations Historical and current land use as it pertains to wetland resourcescan also be ascertained in many circumstances

By making initial determinations and preliminary conclusions regarding theaforementioned factors, a project proponent can make informed decisions, savevaluable time and expense, and determine if detailed on-site investigations arenecessary The level of effort to conduct off-site investigations can vary greatly, andcan be tailored to suit individual site permitting or project requirements

OFF-SITE WETLAND IDENTIFICATION

For the purposes of this chapter, off-site identification of wetlands is defined asassembling and interpreting readily available natural resource mapping and reportsand other documents, both published and unpublished, from existing sources, forthe sole purpose of identifying, locating, and describing wetland resources on agiven site or parcel of land By applying existing resource document information,the researcher can make initial determinations relative to the perceived presence orabsence of one, two, or sometimes three of the parameters necessary for an area to

be considered a jurisdictional wetland In instances where on-site inspection is notnecessary or is beyond the scope of the investigation (e.g., National EnvironmentalPolicy Act wide range alternatives analyses, or limited environmental assessments),off-site wetlands determinations may be the only source of information for environ-mental planning decisions

The overall accuracy of off-site wetland determinations is a function of the quality

of the information (sources) used and the ability of an individual(s) to interpret thedata The keys to conduct of an effective and technically valid analysis include thefollowing:

• Define the project scope and goals prior to conducting the analysis.

• Ensure that a wide range of available sources are investigated and used.

• Emphasize comparison and corroboration between different sources for the same site.

• Obtain recent data, but also data that cover many different years to assist in understanding the site history.

• Understand individual resource document symbols and interpretation keys.

• Understand regulatory requirements for documentation.

The primary objective of off-site wetland determinations is identifying anddetermining whether wetlands exist on a parcel, followed by the approximate dis-tribution and areal extent In determining and quantifying these parameters, the key

is corroboration between different sources That is, not only locating wetlands on asubject parcel from a single source, but corroborating the identification throughmultiple sources

Another important objective of off-site determinations is documenting the inant wetland cover type on parcels that have been preliminarily determined to havewetlands within their boundaries Depending on the source, an interpreter can deter-mine whether the wetlands are forested, scrub–shrub, emergent, aquatic bed, or openwater Detailed interpretation requires a greater level of effort and expertise but canresult in greater detail, such as evergreen forest vs deciduous forest, or persistentemergent vs nonpersistent emergent, or artificially created vs naturally occurring.Classification schemes can be tailored to an individual state’s system, or the widelyaccepted federal system developed by the U.S Fish and Wildlife Service (Cowardin

dom-et al., 1979) and now recognized as the Unified Federal Classification Scheme(Federal Geographic Data Committee, 1995)

Site soil characterizations and surficial hydrological features can also be nized and described from off-site resources Published sources exist which revealsite soils mapping to varying levels of detail and accuracy Determining the hydro-logical regime, or simply the hydrology of a wetland, is a significant feature indetermining the areal extent of wetlands both in the field and from mapped sources.Off-site interpretation can reveal a wetland’s hydrological source, as well as itsdrainage features

recog-Identification Resources

The first step in offsite wetland interpretation studies is identifying and obtainingreadily available sources of information Resources are generally diverse, with vary-ing levels of accuracy Also, resources have been dramatically expanded in recentyears with many new tools available to the interpreter These resources are generallyavailable and provide a baseline of information from which to work

• U.S Geological Survey (USGS) Topographic Maps, Standard Edition and sional Edition (7.5 minute or 15 minute quadrangles, scales 1:24,000 or 1:25,000, continental United States, 1:20,000 Puerto Rico, 1:63,360 Alaska), U.S Depart- ment of the Interior Geological Survey National Mapping Division.

Provi-• U.S Department of the Interior/Fish and Wildlife Service (USFWS) National Wetland Inventory Maps (scale 1:24,000, continental United States, 1:63,360, Alaska), interpreted and adapted from High Altitude Aerial Photography and super- imposed on U.S Geological Survey Topographic Maps.

• U.S Department of Agriculture Natural Resources Conservation Service County Soil Surveys, in cooperation with individual state agriculture experiment stations; used in conjunction with the hydric soils of the United States, 1991, National Technical Committee for Hydric Soils, U.S Department of Agriculture Natural Resources Conservation Service.

• Aerial photography (stereo-paired, black and white, color, color infrared; positive transparency/aero negative; various scales and dates), Federal, State, and Commer- cial Suppliers.

• U.S Geological Survey Surficial Geologic Map Quadrangles (7.5 minute gles, scale 1:24,000), U.S Department of the Interior Geological Survey.

quadran-• Individual state wetland maps (limited coverage and level of accuracy).

Interpreting Resources

This section describes in more detail the analysis and interpretation of theresources listed above Although the level of detail and accuracy varies with eachsource, a first-time evaluator should be able to extract sufficient information toreasonably determine if wetlands are present on-site, and the approximate historical

or current location and extent of wetlands

U.S Geological Survey (USGS) Topographic Maps

The U.S Department of the Interior, Geological Survey National Mapping sion generates 7.5- and 15-minute topographic maps through the National MappingProgram Available are two separate editions, the Standard Edition Maps and theProvisional Edition Maps, each produced at 1:24,000 (English units) or 1:25,000(metric units) for the continental United States Standard Edition Quadrangles rep-resent a finished product with the earth’s topographic relief depicted by contours.Provisional Edition Quadrangles represent an updated draft format, including handlettering and limited descriptive labeling of some physical features

Divi-Stereoplotting field verified, high altitude aerial photographs produce botheditions Some quadrangles are mapped by a combination of orthophotographicimages and map symbols, with orthophotographs derived from aerial photographs

by removing image displacements owing to camera tilt and terrain relief variations(USGS, 1991)

The use of USGS Topographic Maps for off-site wetland identification is oftenthe first step to evaluate a site’s physical features In addition to topographic,hypsographic, infrastructure, and other physical features, the USGS TopographicMaps provide detailed information relative to vegetation cover types, surface fea-tures, coastal features, hydrographic features such as rivers, lakes, and canals, andsubmerged areas and bogs Figure 1 is a section of an USGS Quadrangle and depictssome of these features The section includes wooded marsh or swamp in the westernand southern parts of the site, perennial ponds or lakes in the central part of the site,and perennial streams associated with cranberry bogs in the northeast part of thesite Although most of the wetland and open water interpretation keys that accom-pany the maps are self-explanatory, the individual submerged areas and bogs keysrequire a little elaboration to distinguish among different wetland cover types

Marsh or swamp designations are wetlands characterized by saturated soil ditions in the root zone (as opposed to inundation), with emergent, herbaceous, oraquatic bed vegetation as the dominant cover class An example would be a rush(Juncus spp., Scirpus spp.) and sedge (Carex spp.) dominated wet meadow.

con-Submerged marsh or swamp designations indicate an inundated root zone conditionwith emergent, herbaceous, or aquatic bed vegetative dominants A typical example

is a broad-leaved cattail (Typha latifolia) or pickerelweed (Pontederia cordata)marsh Wooded marsh or swamp is a wetland characterized by saturated soil con-ditions with shrub, sapling, or mature forest as the dominant cover class A saturatedred maple (Acer rubrum) swamp is an example Submerged wooded marsh or swamp

indicates root zone inundation (ponding) as the dominant water regime with shrub,

Figure 1 A U.S Geological Survey topographic map.

sapling, or mature forest as the dominant cover class A bottomland hardwood forestdominated by cypress (Taxodium spp.) trees is an example Land subject to inunda- tion can be floodplain and flood-prone areas that may support wetland hydrologyand wetland vegetation (hydrophytes) Rice fields and cranberry bogs are examples

of anthropogenically influenced wetland areas

Some of the advantages to using USGS Topographic Maps include the relativeaccuracy of the topographic contours in undisturbed areas, photointerpretation doc-umentation is groundtruthed at regular intervals, and individual quadrangles areperiodically photorevised which assists in chronological evaluation of a site’s history.The limitations in using USGS Topographic Maps include interpretation problemsassociated with the small scale (1 in equals 610 m) of the maps, and smaller wetlandsoften are frequently unmapped In some parts of the country, quadrangles may betoo outdated to be of use

U.S Fish and Wildlife Service (USFWS) National Wetland Inventory Maps

The USFWS initiated the National Wetland Inventory (NWI) program andmapping in 1975 to assess, measure, and characterize the extent of wetlands andopen water areas throughout the United States The NWI Maps are produced fromphotointerpretation of high altitude, stereo, aerial photographs High altitude aerialphotographs were selected over satellite imagery because of the problems satelliteimagery had in capturing optimum water conditions for wetland detection, detectingsmaller wetlands, and identifying forested wetlands (Tiner and Wilen, 1983) TheNWI Maps are developed from 1 : 60,000 color-infrared aerial photographs Pho-tointerpretation of the aerials provides a three-dimensional image, thus allowingthe interpreter to identify trees from shrubs, while considering shade and slope.Wetland and open water types are differentiated based on their characteristic pho-tographic signatures

NWI Maps are developed according to a comprehensive evaluation process(Tiner and Wilen, 1983) The preliminary field investigations and photointerpretation

of high altitude aerial photographs is the initial step, with review of existing wetlandinformation and quality control of the interpreted photographs completing the firstphase Draft map production is initiated with a subsequent interagency review ofdraft maps and final map production Available are two series of NWI Maps: the1:100,000/1:250,000 scale and large scale 1:24,000 The USGS Topographic MapQuadrangle is used as a base map with wetland and deepwater areas depicted

as overlays

A new wetland classification was developed by USFWS to correspond with theNWI Maps Classification of wetlands and deepwater habitats of the United States(Cowardin et al., 1979) describes individual wetland ecological attributes andarranges them in a hierarchical system that facilitates resource management andinventory The three key components in the ecological hierarchy are hydrophytes,hydric soils, and hydrology

The use of NWI Maps in off-site wetland identification typically provides thegreatest level of detail and accuracy with the least amount of interpretation effort

and expertise The USFWS Classification System is a comprehensive and progressiveinventory that groups wetlands into one of five major systems, marine, estuarine,lacustrine, riverine, and palustrine, based upon hydrologic, geomorphologic, chem-ical, and biological factors (Cowardin et al., 1979, see Chapter 1) The hierarchyprogresses through subsystems, classes, and subclasses that further refine anddescribe specific wetland structural (vegetation, hydrology, dominant life form, etc.)components Figure 2 depicts a representative section from an NWI Map that cor-responds with Figure 1, and that indicates several different wetland classes withinthe palustrine system Comparing Figure 2 with Figure 1, and using the interpretivekey that accompanies the map, the interpreter is able to determine that the woodedswamp or marsh of the USGS Map has been further defined as palustrine forestedbroad-leaved deciduous wetland An interpreter can become familiar with this systemwith a little practice resulting in quick characterizations of site conditions relative

to wetland types

The accuracy of NWI Maps varies between systems and classes, with the highestdegree of accuracy occurring for large marine, lacustrine, and estuarine systems.Less accurate are smaller mapped units for palustrine wetlands, specifically palus-trine forested wetlands The latter can be misstated owing to photointerpretationdifficulties encountered as a result of leaf-in periods, when the interpreter cannotaccurately describe the forest floor (MacConnell et al., 1989) NWI Maps providethe greatest diversity of all off-site references, with the possible exception of aerialphotographs However, the latter require a greater degree of photointerpretationexpertise, and the NWI maps were prepared for the express purpose of identifyingand classifying wetlands Through use of the USFWS Classification system, aninterpreter can characterize a wetland’s system, the dominant vegetative structurallife form (e.g., forested, emergent, aquatic bed), its hydrological regime (e.g., inter-mittent vs perennial), and substrate (e.g., rock bottom or unconsolidated bottom).The taxonomy also has provisions for documenting anthropogenic influence oncreated or farmed wetlands (e.g., palustrine farmed cranberry bogs and palustrineopen water artificially excavated)

The limitations of NWI Maps for off-site wetlands identification include thesmall scale (1 in equals 2000 ft), errors associated with photointerpretation of selectcover types (principally deciduous forest), limited field verification, and the lack ofphotorevision since initial production NWI Maps are beneficial as a qualitativereference and are one of the only federally produced and readily available documentsfor the sole purpose of identifying, inventorying, and characterizing wetlands

U.S Department of Agriculture Natural Resources Conservation Service Soil Surveys and the Hydric Soils of the United States List

The U.S Department of Agriculture Natural Resources Conservation Serviceproduces County Soil Surveys in cooperation with the individual state’s agriculturalexperiment station Programs have mapped individual soil series based on compre-hensive field investigations conducted by Natural Resources Conservation Serviceand State soil scientists To produce the maps, soil scientists observe the steepness,length and shape of slopes, the size and velocity of streams, the kinds of native

plants and rocks, and evaluate soil profiles (U.S Department of Agriculture NaturalResources Conservation Service,1978) Soil profiles are examined to the depth ofthe parent material and are compared to soil profiles examined in other counties forthe purpose of comparing and contrasting known soil series.

A unified soil taxonomy, the U.S Department of Agriculture Soils Classification,

is used across the nation to characterize and classify soil types Soil series and soilphase are the most common terms used in describing individual soil types A soil

Figure 2 A National Wetland Inventory map.

series is a grouping of soils that have similar profiles and major horizons and arenamed after the town in which the series was first discovered (U.S Department ofAgriculture Natural Resources Conservation Service, 1978) Phases further refinethe series based on the texture in the surface layer, slope, or stoniness (U.S Depart-ment of Agriculture Natural Resources Conservation Service, 1978) Soil mappingunits and boundaries are depicted as overlays on high altitude aerial photographyand are originally drafted by the field soil scientists These boundaries are furtherrefined following laboratory analysis of soil properties The finished product indi-cates soil boundary delineations, soil series descriptions, and biophysicochemicalproperties Additional sections of the soil survey provide information about recom-mended use and management of the soils, soil properties, and soil formation.Use of soil surveys for off-site wetland identification is limited to the identifi-cation and distribution of hydric soils Hydric soils, one of the three essentialcharacteristics of a federal jurisdictional wetland, have unique physical propertiesthat set them apart from nonhydric soils A hydric soil is defined as “a soil that issaturated, flooded, or ponded long enough during the growing season to developanaerobic conditions in the upper part” (U.S Department of Agriculture NaturalResources Conservation Service, 1991).

The development of hydric soils is ultimately driven by the presence of wetlandhydrology, and under sufficiently wet conditions (root zone saturation and inunda-tion), hydric soils support the growth of hydrophytic vegetation The U.S Depart-ment of Agriculture Natural Resources Conservation Service has developed a list ofhydric soils of the United States by applying criteria (e.g., drainage class, organic

vs mineral, etc.) of the National Technical Committee for Hydric Soils (U.S ment of Agriculture Natural Resources Conservation Service, 1991) Included in thislist are most of the somewhat poorly drained soil series, and all of the poorly drainedand very poorly drained soils Hydric soil classifications have been developed based

Depart-on taxDepart-onomic and morphologic features Tools subsequently have been developedfor assisting in the field determination of drainage classes (New England HydricSoils Technical Committee, 1998)

Through the use of individual soil surveys, an interpreter can determine allmapped soil series on-site and then cross-reference the list of soils with Hydric Soils

of the United States Figure 3 is a soil survey map of the site depicted in previousfigures Examination of the site and cross-reference with the hydric soils list indicatesthat Sanded Muck (SB), Peat (Pe), Freshwater Marsh (Fr), Scarboro Sandy loam(ScA), Muck (Mv), and Au Gres and Wareham loamy sands (AuA) are hydric soil.The occurrence of hydric soils corresponds with the wooded swamp or marsh,perennial lakes or ponds, and cranberry bogs of the USGS Map, as well as thepalustrine forested broad-leaved deciduous, palustrine farmed wetlands, and palus-trine open water of the NWI Map

Although soil mapping involves an intensive field effort, the accuracy of the soilmaps is quite variable, and areas mapped as hydric soils (a hydric soil series) cancontain inclusions of nonhydric soils Conversely, areas of nonhydric soils maycontain hydric inclusions The soil mapping information is best used as a macroscaleassessment tool and should not be used for definitive boundaries of hydric soils An

advantage in using soil surveys and the list of hydric soils is that the interpreter doesnot need to spend time learning the U.S Department of Agriculture Soils Classifi-cation and taxonomy system to be able to locate areas of mapped hydric soils on asite, although it is recommended that the interpreter understand the basic principlesunderlying the criteria for listing a soil as a hydric soil.

Figure 3 A U.S Department of Agriculture Soil Conservation Service soils survey.

Comparison and Corroboration

USGS Topographic Maps, USFWS NWI Maps, and U.S Department of culture Natural Resources Conservation Service Soil Surveys are typically the mostaccessible resources and require the least amount of technical knowledge to interpret.The effectiveness and level of accuracy in conducting off-site wetlands interpretationstudies using these resources is a function of the time needed to obtain each sourceand interpreting the information Emphasis should be placed on comparing andcontrasting individual sources: that is, comparing and corroborating the results fromUSGS to NWI to the Soil Survey, being sure to consider the years each source wasinitially produced For example, the USGS indicates wooded marsh or swampthroughout the western and southern sections of the reference site (Figure 1), theNWI indicates palustrine forested broad-leaved deciduous wetland in the westernand southern sections of the site (Figure 2), and the U.S Department of AgricultureNatural Resources Conservation Service indicates hydric soils in the western andsouthern sections of the site (Figure 3) Therefore, the interpreter can be reasonablyconfident that wetlands, and most likely forested wetlands, exist at the site In aneffort to further refine the information already obtained from these resources, addi-tional resources can be consulted and evaluated

Agri-Aerial Photographs

Aerial photography has been used since the 1860s for remote sensing land-usepatterns and activities through the use of hot-air balloons (McKnight, 1987) Theseactions spawned the development of photogrammetry, the science of obtainingreliable and defensible measurements from photographs and mapping from aerialphotographs (Ritchie et al., 1988) Historically, the interpretation of aerial photog-raphy has fallen under the term remote sensing, with the net result being that aerialphotographs were the only tool used in remote sensing Contemporary views havealtered the term to include a wide range of tools and analytical devices One recentdefinition stated remote sensing is the measurement of reflected, emitted, or back-scattered electromagnetic radiation from the earth’s surface using instruments sta-tioned at a distance from the site of interest (Roughgarden et al., 1991) Nonetheless,aerial photography is used today as a powerful source for remote sensing land use,including wetland identification, characterization, and perturbation as a result ofanthropogenic activities

Stereo-paired vertical contact prints provide the most useful and scientificallydefensible information as a three-dimensional image of the earth’s surface is pre-sented to the interpreter via a stereoscope This three-dimensional image is obtainedthrough photographs taken in stereo pairs with end overlap The photographs areinterpreted with a stereoscope, which allows the interpreter to closely examine siteconditions by adding depth of field, and provides the ability to distinguish wetlandcover types Different cover types have characteristic signatures that can be quanti-fied based on observable color, tone or hue, shadow, texture, and depth of field.Color signatures can be further refined using the Inter-Society Color Council and

National Bureau of Standards (ISCC-NBS) method of color description, using troid Color Charts (Smith and Anson, 1968).

Cen-Permanently and seasonally inundated forested, scrub–shrub, emergent, and openwater areas are relatively easy to distinguish from upland habitats using aerialphotographs Surface water has a different reflectance pattern than dry areas Thedifficulty comes when trying to identify seasonally saturated wetlands, particularlyseasonally saturated forested wetlands

Aerial photographs are available in many formats, scales, and geometry(Figure 4) The most common photograph types used for wetland identification arevertically oriented black and white, color, and color infrared using aerographic film.Aerial photograph geometry (i.e., basis of the angular relationship to the earth’ssurface) can be divided into two major categories: oblique (including low obliqueand high oblique) and vertical (see Figure 5 and Hudson and Lusch, 1990) Obliqueaerial photographs have an advantage to the interpreter, in that ground features can

be interpreted from a familiar point of view (McKnight, 1987) In addition, owing

to the orientation of the camera for oblique photos, the stereoscopic effect is reduced,thereby negating the three-dimensional effect However, due to measurement inad-equacies and scale development, vertically oriented photographs are used for deter-mining quantitative information and provide more useful and defensible informationfor wetland identification Combining aerial photographs with groundtruthing can

be a very effective and cost-efficient means to identifying and delineating wetlandboundaries on large parcels

Film types are also an important consideration in identifying wetlands matic black and white photographs are the least expensive and most common.However, color infrared photographs have a demonstrated and significant advantage.Color infrared discriminates between living and dead vegetation, enhances openwater areas, and discriminates natural features from man-made features

Panchro-Larger scale, low-altitude aerial photography is recommended over smaller scale,high-altitude aerial photography for clarity, ease of interpretation, distinguishingground features, and general resolution The most useful and accurate interpretationsare made through chronological analysis of a site

Aerial photographic coverage and availability significantly limit its use for site wetland identification Federal and State agencies have inventories with spottycoverage, which may not be available for purchase The National Archives (in Utah)maintains an active database and inventory of aerial photographs (black and white,color infrared, stereo-paired) covering the entire continental United States for selectyears, and these photographs are available for purchase They are generally high-altitude, small-scale aerial photographs Private commercial suppliers often maintaininventories, and usually specialize within a region (i.e., New England, Northwest,Southeast) Coverage is largely unpredictable varying from complete chronologicalcoverage over several years to no coverage at all Purchase costs can be quite high,with some firms charging access fees for database reviews

off-Because aerial photography provides the base map and framework for most otheroff-site resources, it is apparent how important it can be when used in its unrevisedform Stereo aerial photographic interpretation has evolved into a scientific andtechnical discipline of its own and, in some instances, requires considerable expertise

to extract valid information Nonstereo paired aerial photographs can be used tosupplement the other off-site information in a qualitative manner There is muchvariability among nonstereo aerial photographs, especially relative to geometry,

Figure 4 A vertical black and white aerial photograph.

scales, film types, and coverage When conducting preliminary qualitative off-sitewetland reviews, interpretation of aerial photographs may not be necessary However,

if the goal is to quantify wetland site conditions over time, aerial photographs mayprove to be an indispensable tool

U.S Geological Survey Surficial Geologic Maps

The U.S Geological Survey produces surficial geologic maps primarily for use

as indicators of geologic zonation above bedrock These maps provide some detailrelative to soil and subsurface composition and are helpful in locating and identifyingswamp deposits, alluvium, surface water bodies, and other wetland features Figure 6

Figure 5 Aerial photography angular orientation.

illustrates the location of surface waterbodies, swamp deposits (Qs), and cranberrybogs on the reference site The swamp deposit designations are indicative of organicmatter, clay, silt, and sand accumulating in swamps (USGS, 1967).

Figure 6 A U.S Geological Survey surficial geologic map.

Individual State Wetland Maps

Several individual states have produced wetland maps for use in macroscaleplanning, and at least in one instance (MacConnell et al., 1989), for jurisdictionalpurposes Most of the maps are developed based on interpretation of stereo-pairedaerial photography, similar to the process used by the National Wetland Inventory.Representative states that have produced wetland maps include Maine, Vermont(based on NWI), Massachusetts (Wetlands Restriction Program), New York, andNew Jersey Coverage, interpretation keys (classification systems), and accuracy arevariable from state to state

ON-SITE WETLAND DELINEATION

The ability to document wetland site conditions without detailed on-siteinvestigations has a demonstrated need from a natural resources planning perspec-tive as well as from a jurisdictional perspective Documentation of anthropogenicinfluence on wetlands is another demonstrated need for using off-site materialsfor wetland identification By using the resources and methods discussed above,

a reviewer can generally make a positive or negative determination regarding thepresence or absence of wetlands, estimate the areal extent of wetlands, and, insome cases, determine major cover types (although a follow-up site inspection isalways recommended for full confirmation) However, off-site wetland identifica-tion is not a substitute for on-site wetland delineation when the goal is a definitivedemarcation or delineation of wetlands for site development and project planningpurposes

The need to identify jurisdictional wetlands and delineate wetland/upland aries in the United States is principally driven by Section 404 of the Clean WaterAct by state and municipal wetland protection statutes The wetland protectionstatutes, and associated regulatory policies, dictate that wetland boundaries be estab-lished and, in many cases, confirmed, prior to site development and related landmanagement activities Therefore, project proponents are required to characterizeand quantify the differences between wetlands and uplands so that the boundary can

bound-be identified with some certainty and repeatability This is accomplished by fieldassessment of vegetation, soils, and hydrology

Through interagency consensus, three characteristics or parameters have beenselected to distinguish wetlands from uplands First, wetlands are characterized bythe presence of water, typically from a surface or groundwater source Water levels

in wetlands are typically dynamic, with the frequency of saturation and inundationvarying among wetland types and varying temporally within wetland types Second,wetlands are characterized by the presence of unique soils that are diagnostic ofwetland conditions These soils display properties that indicate anaerobic conditions

in the root zone resulting from prolonged saturation or inundation Finally, wetlandsare characterized by the presence of wetland vegetation that possesses morphological

adaptations that enable them to tolerate frequent root zone saturation or inundationand anaerobic conditions Earlier in this chapter, the regulatory definition of wetlandswas provided More recently, the National Academy of Sciences (National ResearchCouncil, 1995) proposed another definition of wetlands.

A wetland is an ecosystem that depends on constant or recurrent, shallow inundation

or saturation at or near the surface of the substrate The minimum essential teristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical and biological features reflective of recurrent, sustained inundation or saturation Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation These features will be present except where specific physicochemical, biotic, or anthropogenic factors have removed them

charac-or prevented their development.

There are many factors that affect the presence of these features Topographicalrelief and overall landscape position are significant physical factors that often dictatethe source for wetland hydrology For example, topographical depressions oftencorrespond closely with water table elevation in glaciated wetlands of the northeast-ern United States Headwaters of streams and rivers are often the result of sheetrunoff from watersheds that emanate from mountainous regions Palustrine andriverine wetlands are often associated with these surface water bodies Other factorsthat influence the formation of the three wetland factors include stratigraphy, surficialand bedrock geology, and watershed and climatological conditions including pre-cipitation and evapotranspiration

In identifying and delineating wetlands, it is important to establish in advancethe overall goal and scope of the wetland investigation The investigator shoulddetermine if it is necessary to conduct a comprehensive on-site delineation of theentire wetland and upland boundary or simply confirm the presence or absence ofwetlands A wetland determination is the process by which the evaluator makes apositive or negative assumption that wetlands are extant on a site This assumption

is based on identifying whether or not wetland characteristics are present anywherewithin the site’s boundaries

Wetland delineation is the process by which the investigator identifies and locateswetlands, then qualitatively or quantitatively assesses the areal extent of wetlands onthe site This is accomplished through consideration of hydrological field indicators,soil profiles, and vegetation sampling and inventory Wetland delineation techniquesand methodologies vary from place to place in response to local and state jurisdictionalrequirements Nevertheless, almost without exception, local and state mandated pro-cedures are predicated upon parameters defined by the federal agencies These factors,and their associated technical criteria, are expressed in the Corps of Engineers Wetland Delineation Manual (Environmental Laboratory, 1987), the Wetland Identification and Delineation Manuals, Volumes I and II (Sipple, 1988), the Federal Manual for Identifying and Delineating Jurisdictional Wetlands (Federal Interagency Committeefor Wetland Delineation, 1989), the National Food Security Act Manual (U.S Depart-ment of Agriculture, 1994), and the National Research Council (1995)