Applied Wetlands Science - Chapter 2

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 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 ... - tailieumienphi.vn