Tammi, Carl E. “Wetland Identification and Delineation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001 ©2001 CRC Press LLC CHAPTER 2 Wetland Identification and Delineation Carl E. Tammi CONTENTS Off-Site Wetland Identification Identification Resources Interpreting Resources U.S. Geological Survey (USGS) Topographic Maps U.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 List Comparison and Corroboration Aerial Photographs U.S. Geological Survey Surficial Geologic Maps Individual State Wetland Maps On-Site Wetland Delineation Wetland Hydrology Hydrological Field Indicators Hydric Soils Hydric Soil Field Indicators Hydrophytic Vegetation Indicators of Hydrophytic Vegetation Identifying and Delineating Wetlands Undisturbed Areas Disturbed Areas Difficult Areas Aids to Delineation References ©2001 CRC Press LLC Wetland identification and the science of delineation are regulatory-driven activ- ities that are commonly required in land-use development, planning, exploration, and a host of related activities involving future site expansion. Although federally man- dated wetland regulatory statutes have been in existence for over 25 years, the science of identifying and delineating the extent and types of wetlands has been consistently evolving. As the science has evolved, a greater awareness of the functions and values wetlands provide has occurred with the resultant development of extensive wetland identification and delineation resources within the last 10 years. Today, the land-use planner, wetland scientist, and manager have a range of tools in print, graphic, and electronic format available to assist in making wetland determinations and defendable jurisdictional delineations. Typically, the science of identifying and delineating wet- lands is a two-tiered process. An initial office-based off-site assessment is conducted for identification purposes. A legally binding jurisdictional determination requires an on-site field assessment called a wetlands delineation. Identifying the location and determining the areal extent of jurisdictional wet- 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 and local land-use laws and regulations. Section 404 of the Clean Water Act is the principal tool that the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency use to regulate the discharge of dredged or fill material into waters 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 are inundated or saturated by surface or groundwater at a frequency and duration suf- ficient to support, and that under normal circumstances do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas” (33 CFR 328.3). In identifying and delineating federal jurisdiction wetlands, three essential tech- nical criteria or factors are applied: the presence of wetlands hydrology through surficial or groundwater; a prevalence of wetland vegetation (hydrophytes) that typically has specialized morphological and physiological adaptations to tolerate saturated or inundated conditions; and wetland soils (hydric soils), which in their undrained condition exhibit characteristics of somewhat poorly drained, poorly drained, or very poorly drained soils. Other major federal legislation that drives wetland identification includes Section 401 Water Quality Certification (delegated to the individual states), Section 10 of the Rivers and Harbors Act of 1899 and the National Environmental Policy Act. Many states have promulgated and adopted wetland protection legislation for inland, 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 upon project proponents and land-use managers to determine, locate, and identify wetland resources 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 ©2001 CRC Press LLC and resultant time-consuming permit decisions. This action can streamline the per- mitting process during more advanced stages of project design through avoidance and minimization of wetland impacts. An off-site macroscale wetland determination makes a positive or negative wetland determination for a subject parcel, and deter- mines the approximate location of wetland and deepwater areas. It also determines the approximate areal extent and distribution of wetland and deepwater areas, and the predominant wetland cover type (Cowardin et al., 1979). Finally, an off-site macrosite wetland determination assesses the need for continued analysis and approximate level of effort associated with any analyses. In some instances, information relative to the potential presence of hydric soils, surficial hydrology, and site disturbance can be determined from off-site wetland determinations. Historical and current land use as it pertains to wetland resources can also be ascertained in many circumstances. By making initial determinations and preliminary conclusions regarding the aforementioned factors, a project proponent can make informed decisions, save valuable time and expense, and determine if detailed on-site investigations are necessary. The level of effort to conduct off-site investigations can vary greatly, and can 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 as assembling and interpreting readily available natural resource mapping and reports and other documents, both published and unpublished, from existing sources, for the sole purpose of identifying, locating, and describing wetland resources on a given site or parcel of land. By applying existing resource document information, the researcher can make initial determinations relative to the perceived presence or absence 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 not necessary or is beyond the scope of the investigation (e.g., National Environmental Policy 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 the data. The keys to conduct of an effective and technically valid analysis include the following: • 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. ©2001 CRC Press LLC The primary objective of off-site wetland determinations is identifying and determining 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 a subject parcel from a single source, but corroborating the identification through multiple sources. Another important objective of off-site determinations is documenting the dom- inant wetland cover type on parcels that have been preliminarily determined to have wetlands within their boundaries. Depending on the source, an interpreter can deter- mine whether the wetlands are forested, scrub–shrub, emergent, aquatic bed, or open water. Detailed interpretation requires a greater level of effort and expertise but can result in greater detail, such as evergreen forest vs. deciduous forest, or persistent emergent vs. nonpersistent emergent, or artificially created vs. naturally occurring. Classification schemes can be tailored to an individual state’s system, or the widely accepted federal system developed by the U.S. Fish and Wildlife Service (Cowardin 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 recog- nized and described from off-site resources. Published sources exist which reveal site 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 in determining 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 its drainage features. Identification Resources The first step in offsite wetland interpretation studies is identifying and obtaining readily available sources of information. Resources are generally diverse, with vary- ing levels of accuracy. Also, resources have been dramatically expanded in recent years with many new tools available to the interpreter. These resources are generally available and provide a baseline of information from which to work. • U.S. Geological Survey (USGS) Topographic Maps, Standard Edition and Provi- 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. • 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. ©2001 CRC Press LLC • 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 quadran- gles, scale 1:24,000), U.S. Department of the Interior Geological Survey. • Individual state wetland maps (limited coverage and level of accuracy). Interpreting Resources This section describes in more detail the analysis and interpretation of the resources listed above. Although the level of detail and accuracy varies with each source, a first-time evaluator should be able to extract sufficient information to reasonably 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 Divi- sion generates 7.5- and 15-minute topographic maps through the National Mapping Program. Available are two separate editions, the Standard Edition Maps and the Provisional 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 hand lettering and limited descriptive labeling of some physical features. Stereoplotting field verified, high altitude aerial photographs produce both editions. Some quadrangles are mapped by a combination of orthophotographic images 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 often the first step to evaluate a site’s physical features. In addition to topographic, hypsographic, infrastructure, and other physical features, the USGS Topographic Maps provide detailed information relative to vegetation cover types, surface fea- tures, coastal features, hydrographic features such as rivers, lakes, and canals, and submerged areas and bogs. Figure 1 is a section of an USGS Quadrangle and depicts some of these features. The section includes wooded marsh or swamp in the western and 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 the site. Although most of the wetland and open water interpretation keys that accom- pany the maps are self-explanatory, the individual submerged areas and bogs keys require a little elaboration to distinguish among different wetland cover types. Marsh or swamp designations are wetlands characterized by saturated soil con- ditions in the root zone (as opposed to inundation), with emergent, herbaceous, or aquatic bed vegetation as the dominant cover class. An example would be a rush ( Juncus spp., Scirpus spp.) and sedge ( Carex spp.) dominated wet meadow . ©2001 CRC Press LLC Submerged marsh or swamp designations indicate an inundated root zone condition with 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 saturated red 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. ©2001 CRC Press LLC sapling, or mature forest as the dominant cover class. A bottomland hardwood forest dominated by cypress ( Taxodium spp.) trees is an example. Land subject to inunda- tion can be floodplain and flood-prone areas that may support wetland hydrology and 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 relative accuracy of the topographic contours in undisturbed areas, photointerpretation doc- umentation is groundtruthed at regular intervals, and individual quadrangles are periodically photorevised which assists in chronological evaluation of a site’s history. The limitations in using USGS Topographic Maps include interpretation problems associated with the small scale (1 in. equals 610 m) of the maps, and smaller wetlands often are frequently unmapped. In some parts of the country, quadrangles may be too 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 and mapping in 1975 to assess, measure, and characterize the extent of wetlands and open water areas throughout the United States. The NWI Maps are produced from photointerpretation of high altitude, stereo, aerial photographs. High altitude aerial photographs were selected over satellite imagery because of the problems satellite imagery had in capturing optimum water conditions for wetland detection, detecting smaller wetlands, and identifying forested wetlands (Tiner and Wilen, 1983). The NWI Maps are developed from 1:60,000 color-infrared aerial photographs. Pho- tointerpretation of the aerials provides a three-dimensional image, thus allowing the 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 wetland information and quality control of the interpreted photographs completing the first phase. Draft map production is initiated with a subsequent interagency review of draft maps and final map production. Available are two series of NWI Maps: the 1:100,000/1:250,000 scale and large scale 1:24,000. The USGS Topographic Map Quadrangle 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 the NWI Maps. Classification of wetlands and deepwater habitats of the United States (Cowardin et al., 1979) describes individual wetland ecological attributes and arranges them in a hierarchical system that facilitates resource management and inventory. 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 the greatest level of detail and accuracy with the least amount of interpretation effort ©2001 CRC Press LLC and expertise. The USFWS Classification System is a comprehensive and progressive inventory 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 hierarchy progresses through subsystems, classes, and subclasses that further refine and describe 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 within the palustrine system. Comparing Figure 2 with Figure 1, and using the interpretive key that accompanies the map, the interpreter is able to determine that the wooded swamp or marsh of the USGS Map has been further defined as palustrine forested broad-leaved deciduous wetland. An interpreter can become familiar with this system with 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 highest degree 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 photointerpretation difficulties encountered as a result of leaf-in periods, when the interpreter cannot accurately describe the forest floor (MacConnell et al., 1989). NWI Maps provide the greatest diversity of all off-site references, with the possible exception of aerial photographs. However, the latter require a greater degree of photointerpretation expertise, and the NWI maps were prepared for the express purpose of identifying and classifying wetlands. Through use of the USFWS Classification system, an interpreter can characterize a wetland’s system, the dominant vegetative structural life 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 on created or farmed wetlands (e.g., palustrine farmed cranberry bogs and palustrine open water artificially excavated). The limitations of NWI Maps for off-site wetlands identification include the small scale (1 in. equals 2000 ft), errors associated with photointerpretation of select cover types (principally deciduous forest), limited field verification, and the lack of photorevision since initial production. NWI Maps are beneficial as a qualitative reference and are one of the only federally produced and readily available documents for 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 Service produces County Soil Surveys in cooperation with the individual state’s agricultural experiment station. Programs have mapped individual soil series based on compre- hensive field investigations conducted by Natural Resources Conservation Service and 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 ©2001 CRC Press LLC plants and rocks, and evaluate soil profiles (U.S. Department of Agriculture Natural Resources Conservation Service, 1978). Soil profiles are examined to the depth of the parent material and are compared to soil profiles examined in other counties for the 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 soil phase are the most common terms used in describing individual soil types. A soil Figure 2 A National Wetland Inventory map. [...]... regarding the presence or absence of wetlands, estimate the areal extent of wetlands, and, in some cases, determine major cover types (although a follow-up site inspection is always recommended for full confirmation) However, off-site wetland identification is not a substitute for on-site wetland delineation when the goal is a definitive demarcation or delineation of wetlands for site development and project... saturation or inundation Finally, wetlands are characterized by the presence of wetland vegetation that possesses morphological 20 01 CRC Press LLC adaptations that enable them to tolerate frequent root zone saturation or inundation and anaerobic conditions Earlier in this chapter, the regulatory definition of wetlands was provided More recently, the National Academy of Sciences (National Research Council,... 19 92) Other sources (Tiner, 1991; Sipple, 19 92) discuss the importance of the dynamic nature (e.g., seasonality, degree of wetness) of wetlands as it relates to the individual factors and the ability to effectively recognize wetland boundaries Tiner (1993) proposed an innovative approach to delineating wetlands based on identifying primary indicators of hydrophytes and hydric soils in undrained wetlands. .. hues and very dark chromas (7.5 YR 2/ 0, 10 YR 2/ 1, etc.) 20 01 CRC Press LLC Table 2 Field Indicators of Hydric Soils Organic soils (histosols) Histic epipedons Sulfidic material Aquic or peraquic moisture regime Reducing condition Soil color Mottling or concretions High organic matter content in surface horizon Subsurface streaking Spodic horizon Note: Indicators are applied to the soil profile within... National Wetland Inventory maps, and the recollection of local officials or residents 20 01 CRC Press LLC Difficult Areas Some wetlands are inherently more difficult to identify and delineate than other wetlands The difficulty arises because one or more of the wetland indicators may be impermanent Slope wetlands in glaciated wetlands have thin soils over relatively impermeable till or varying hydraulic conditions... Engineers, 19 92) The 1987 Corps Manual, which is the current manual guiding federal jurisdictional technical delineation, defines growing season as that portion of the year when soil temperatures at 50 cm below the soil surface are higher than biologic zero (5˚C) For ease in determination, the growing period can be estimated to occur when air temperature exceeds 22 ˚C (U.S Army Corps of Engineers, 19 92) Drainage... indicates palustrine forested broad-leaved deciduous wetland in the western and southern sections of the site (Figure 2) , and the U.S Department of Agriculture Natural Resources Conservation Service indicates hydric soils in the western and southern sections of the site (Figure 3) Therefore, the interpreter can be reasonably confident that wetlands, and most likely forested wetlands, exist at the site In... IDENTIFYING AND DELINEATING WETLANDS Undisturbed Areas When a site is relatively undisturbed, identifying and delineating wetlands are accomplished by simultaneously applying the criteria for wetland hydrology, hydric soils, and hydrophytic vegetation Typically, the best time to identify or delineate wetlands is during the growing season, when dominant vegetation (especially 20 01 CRC Press LLC annuals)... condition of a wetland and is a function of flood duration and flood frequency All wetlands are dynamic systems from a hydrological viewpoint The hydrology of perennial wetlands varies irregularly on an annual basis Ephemeral wetlands such as vernal pools typically have seasonally varying hydroperiods Tidally influenced wetlands experience daily periodic hydrologic fluctuations Keeping in mind this inherent... WETLAND DELINEATION The ability to document wetland site conditions without detailed on-site investigations has a demonstrated need from a natural resources planning perspective as well as from a jurisdictional perspective Documentation of anthropogenic influence on wetlands is another demonstrated need for using off-site materials for wetland identification By using the resources and methods discussed . Identification and Delineation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC ,20 01 20 01 CRC Press LLC CHAPTER 2 Wetland Identification and Delineation . defendable jurisdictional delineations. Typically, the science of identifying and delineating wet- lands is a two-tiered process. An initial office-based off-site assessment is conducted for identification. similar areas” (33 CFR 328 .3). In identifying and delineating federal jurisdiction wetlands, three essential tech- nical criteria or factors are applied: the presence of wetlands hydrology through surficial