A number of methods can be used to delineate wetland areas. As per the Wetlands Delineation Manual (U.S. Army Corps of Engineers [USACE] 1987), one must identify potential jurisdictional wetlands by addressing the three criteria. This may be accomplished by using a combination of data sources and field indicators with different levels of attention (Figure 3.1). These levels may be applied based on the need for information and documentation as per the tractability of the issue.
To identify and delineate wetlands in a given area it is best to use a combination of existing data, reference materials, and field evaluation procedures. This approach allows all three criteria to be addressed in detail and their conditions recorded for future validation.
Field measurements may involve ground examinations of the three criteria (Figure 3.2). These activities may include field evaluations of hydric soils that may have been identified on soil survey maps or other sources of information; evaluations of indicators of waterlogged soils and/or flooding associated with wetland hydrology; and estimations of dominant plant species and the relative percentage of those plants that are commonly found in wetlands.
The following activities have been found to be beneficial for identification of jurisdictional wetlands and for delineating and mapping wetlands.
Selecting a Method of Analysis and Level of Detail
An important initial consideration in any project is the level of detail and efforts necessary to identify and delineate wetlands. The Federal Wetlands Delineation Manual (USACE 1987) presents three levels of effort that yield an increasing quantity of detail. Selection of the level of effort can be very helpful in tailoring the work product to the need for information. One can also start with the basic level and progress as results or the issues at hand demonstrate the need for more information (Figure 3.3).
The routine level of evaluation involves office efforts and perhaps limited fieldwork for an initial or reconnaissance-level effort. It is a very good starting point, because it reveals the possible extent of wetlands and identifies the potential for general wetland areas or potential jurisdictional wetlands.
The intermediate-level evaluation employs field-based methods to evaluate wetland resources and to quantify wetland characteristics and produce information to inform a detailed report (Figure 3.4). The results of this delineation and the intermediate-level report present a good level of information and can be used in various permitting activities that involve the USACE. The resulting work can be used by the USACE and can also inform the oversight activities on permitting by the U.S. Environmental Protection Agency (USEPA). These activities all come under the auspices of sections of the Federal Water Pollution Control Act, commonly known as the Clean Water Act (CWA).
In this farm field in the glaciated part of southeastern Ohio, frozen water and snow cover much of the land in early spring. Vegetation is crop residue. Delineations under these conditions require careful and thorough efforts.
Comprehensive-level methods are highly detailed and laborious and may be required for special case wetland areas that are under intense scrutiny or for better characterization of wetlands for purposes of wetland function evaluations in support of mitigation (Figure 3.5) or for other needs as discussed in later chapters.
Routine-Level Methods and Analysis Procedures
The preliminary or “routine”-level of analysis is a good place to start any effort. This is because one can conduct a “reconnaissance” and characterize the scope of the work. The routine evaluation indicates where potential jurisdictional wetlands or general wetlands may be located. It can involve an office evaluation of the soil survey and a field inspection for the presence of wetland plants, hydric soils, and wetland hydrology (Figure 3.6). Further detail can be collected within this framework by later applying comprehensive/intermediate-level evaluations to determine whether local areas are truly jurisdictional wetlands.
For the purposes of routine-level analyses, there is a need to define the concept of a “potential jurisdictional wetland.” This label or category allows for documenting a potential condition before the evaluation of all three wetland criteria has been made. Usually, it is necessary to “scope” the potential jurisdictional wetlands. This scoping or routine-level wetland report will allow the client to appreciate the conditions and choose whether to go forward (Lyon 1993).
Identifying plants is difficult because wetlands have a combination of upland, wetland, and aquatic plants. These can be a greater challenge where wetlands and wetland plants are ephemeral or, as shown here, practically invisible during the off-season. Delineators should try, whenever possible, to make plant and wetland determinations during the season when the indicators can be expected to be present.
Hence, it is desirable to define a potential jurisdictional wetland as an area that exhibits one or more of the three wetland criteria. This potential jurisdictional wetland may also be called a general wetland (Lyon 2001).
Wetlands identified during routine-level evaluations may be jurisdictional wetlands but it is necessary to complete an intermediate-level evaluation to make an actual determination as to whether the area is a jurisdictional wetland. The intermediate-level wetland determination would involve greater field sampling detail on plants, soils, and hydrological conditions (Figure 3.7).
To complete a routine investigation and identify potential jurisdictional wetlands, it is desirable to use the following suggested steps and procedures.
One should conduct the routine-level effort by:
Delineators should look for the three layers in any vegetative community: trees, shrubs, and ground cover. This desert waterway displays only two of the four major layers. The ground and shrub layers are apparent but the tree and vine layers are absent. It also shows how one or two of these layers may be missing from certain parts of the area, yet one has to work with this. The location is the Death Valley National Park in California.
Isolated wetlands are difficult to discern from jurisdictional wetlands. Pictured is an isolated hardwood swamp found near a roadside rest stop in Union County in central Ohio.
Note the high water, plants, and hydrologic indicators of flotsam. The classic wetland indicators are present but separated in space because it is a sandy beach barrier. The location is the Straits of Mackinac of Lake Michigan, Lower Peninsula of Michigan. This is also nesting habitat for the endangered piping plover.
Obtaining the county soil survey. Examine the soil type boundaries. It may be useful to transfer the soil boundaries from soil survey maps onto a topographic map or geographic information system (GIS) map of the site. If an engineering-style map is available this may also be used. This can be done for all soil types on the property, with particular attention to soils found on the USDA Hydric List (U.S. Department of Agriculture [USDA] 1991 or http://www.USDA.gov/hydricsoils).
Taking the soils map and other data sources such as aerial photos or images, National Wetlands Inventory (NWI) wetland maps, and large-scale topographic maps to the field and walking the site. Pay attention to lower elevation areas, all streams, creeks, gullies, wet spots, and wetlands. Evaluate any anomalous conditions of soil, bedrock, or hydrology that could result in flooding, ponded water, or a high water table (Figure 3.8).
Walk the entire site and visit the entire property. Walk or drive the surrounding area. Be alert to the above and other conditions. On the site, make notes as to the presence of indicators of hydric soils, wetland hydrology, and wetland plants.
It is vital to evaluate the entire site and avoid omission of small or hidden wetlands. This is necessary to assure that all potential jurisdictional wetlands are identified and located. It is also important because the USACE will often wish to inspect the entire site, and omission of wetlands can create many difficulties as to whether the evaluation was performed in total (Figure 3.9). Also, because findings are administered based on the presence and area of wetlands, omissions go to the heart of the quality and quantity of the evaluation.
One should pay particular attention to hydric soil areas as mapped on the soil survey (http://soils.usda.gov/survey/, http://soils.usda.gov/use/hydric/).
Also, look for wetland plants that may “signal” the presence of hydric soil conditions that do not appear on the soil survey or conditions such as hydric soil inclusions within the larger soil survey mapping unit.
One should note the presence of wetland plants, in particular the obligate wetland plants and facultative wetland plants.
Trees with fat bases are often a good indicator of wetland hydrology.
Taking the field information, available aerial photographs and images, the county soil survey, and other pertinent data and identifying potential wetland areas (Figure 3.10). It is desirable to identify any area with one or more wetland indicators as a potential jurisdictional wetland or general wetland. These locations can be noted and visited or visited again. Upon further examination, they may be later sampled at the intermediate level of detail to determine whether true jurisdictional wetland conditions are present.
Map the boundaries of potential jurisdictional wetlands on an overlay of the property map, large-scale topographical map, or engineering-style map or GIS map. The desirable minimum mapping unit should be one tenth or one hundredth of an acre. Using a digitizer, a scanner, a planimeter, or another area measurement device, make a preliminary estimate of the total area of potential jurisdictional wetlands from the mapping product.
Indicators here are similar to Figure 3.6, yet the absence of standing water demonstrates the value of the indicator.
Integrating information from other data sources, such as watershed and drainage maps, to help characterize any additional resource conditions that may be potentially of jurisdictional interest.
Spending some time checking the routine-level wetland report. This may include further field visits. It is important to be sure that no potential jurisdictional wetlands have gone unnoticed (Figure 3.11). The landowner is depending on the expert for an accurate assessment of potential jurisdictional wetlands. Later, the landowners will conduct their efforts based on the report or use it to initiate an intermediate-level evaluation and report. An inaccurate report at any level of detail can cause incredible difficulties after commencement of development, should a regulatory or other agency become involved and a conflict results as to the presence or absence of wetlands on the site.
Flotsam is deposited high in these branches from the surrounding Earth. How did they get there? This indicates that water levels may have been much higher previously, even though those same conditions are not present during a field visit.
This is a classic scene of a swamp in the spring. Standing water, emerging plants, and other indicators leave little doubt that this is a wetland area.
In late spring, ponded water is characteristic of a farmed wetland. The water conditions will delay planting. Subtle topographic differences exist with the home in the background sitting on a higher elevation. This site is near Circleville, Ohio.
Drainage pipe and ditches abound in the suburban environment. These man-made features alter the connectivity of water conveyances to reduce or eliminate flooding of structures.
Completion of these steps provides a certain minimum level of information and allows identification of areas that are potential jurisdictional wetlands. This preliminary or routine-level report is suitable for identifying the scope of the problem and is the starting point for further intermediate-level analyses to characterize potential jurisdictional wetlands as jurisdictional wetlands or not (Figure 3.12).
Comprehensive Intermediate-Level Methods and Analyses Procedures
A higher level of detail is supplied by comprehensive intermediate-level evaluation procedures (USACE 1987). The resulting product is valuable for making an actual determination of jurisdictional wetlands and their quantities. Such an analysis and the documents resulting from it can be used to respond to wetland-related questions posed by the USACE and the Clean Water Act (CWA), section 404, permitting process.
To complete an intermediate-level evaluation it is necessary to conduct a more intensive effort in the field and office, compared to the routine level of analysis.
Farmed wetlands often maintain many of their wetland characteristics over time despite human intervention. Larger wetlands filter water through farmed areas in wet years, often preventing planting or killing germinated seeds.
These steps are outlined in the Wetlands Delineation Manual (USACE 1987) and are provided here along with enhancements developed from many applications of these procedures by the authors and colleagues. It is assumed that a routine-level evaluation has been conducted to characterize the scope of the problem and that potential jurisdictional wetlands need to be identified and delineated as jurisdictional wetlands or not (Figure 3.13).
Where water and land meet, wetland plants propagate, procreate, and flourish. Here is a desert wetland in South Africa.
The steps in the evaluation may include the following:
Take data source materials developed from the routine-level evaluation and go to the field. Begin sampling for the three criteria to characterize the potential jurisdictional wetlands at the locations of interest (Figure 3.14). Record information collected in a notebook with appropriate writing instruments for the field (e.g., permanent markers or pens and waterproof paper).
For the intermediate-level effort, it is desirable to locate the field sampling in some reference framework. This can be accomplished by the establishment of a grid system of points to be sampled in the field. A 100 × 100 foot grid mesh has been found to be suitable size and resolution for sampling at the intermediate-level of detail.
Such a mesh of sampling locations can be laid out by pacing or by using a tape measure. The grid would be located within the boundaries and outside the boundaries of the potential jurisdictional wetland defined by the routine level evaluation (Figure 3.15). In this way, one can establish grid node locations within the wetlands and in the uplands and then refine the boundary between grid nodes.
Initially, one should lay out a 100-foot length on the ground using a tape measure. Over time and with experience one can use pacing to establish distances and the grid.
It is also possible to use steel or fabric distance tapes or other methods of estimation that provide a field-expedient way to measure distances and create grid sampling nodes separated at regular intervals.
With a set grid mesh and grid size and directional references for the grid, it is possible to sample at an appropriate frequency and document the location of the samples in the field and on mapping products. The grid can be referenced to cardinal directions, fence lines, or other reference points via a compass. It will be possible to relocate the sample sites for later inspection by USACE personnel.
Water ponds along this highway near the White Mountains in California. A desert spring also feeds wetland plants in a narrow strip adjacent to the highway.
It may be necessary to revisit the field to locate the jurisdictional boundary because they are often found between the sample points. In essence, it is necessary to interpolate between the points to fix the boundary. If the characteristics of the wetland boundary are not clear, sample soils and plants to determine the actual boundary as it is found between the sampling points of the 100-foot grid.
Be sure to “flag” or monument the individual sample points so that they can be checked at later field inspections. Surveyor’s tape, Mylar tape, or other permanent flags should be employed. Time and weather are hard on these materials and care should be taken in selecting materials that will last. Often, it may be many months before a given property is inspected, or it may never be necessary to inspect a property. It is still important, however, to be able to relocate the sampling sites at a later date. A request for an inspection by the USACE may be encountered at any time, and the elements of the field sample should be preserved to facilitate a response to questions posed by USACE.
It is also desirable to measure with a tape or pace from a given sample point to adjacent examples and evaluate whether the grid system is square. This allows one to determine whether individual points are out of position, and it facilitates correction of misplaced samples or lost points at a later date.
In certain instances, it is desirable to use survey methods to establish the grid and create a surveyed map. Suitable techniques are discussed later.
At each individual sample point or grid node, it is necessary to collect detailed information on soils, hydrology, and plants. Data should be recorded on field sheets or memo pads. The data can be presented later on the appropriate forms supplied in the Wetlands Delineation Manual (USACE 1987). In particular, forms B-2 and B-6 have been useful, and now examples like the Wetland Determination Form are useful (USACE 2010a–f). They provide adequate space for the recording of plant, soil, and hydrological measures on the form (Lyon 1993).
Sometimes water is present and ponded where it is unwelcome. Wildlife and wetland plants exploit the presence of unwelcome waters along this roadside in San Diego County, California.
To evaluate wetland hydrology and subsurface hydric soil conditions as well as soil type and characteristics, one should dig a hole. This can be done with a shovel at the grid sampling site. The sampling hole should be deep enough to evaluate the top eighteen or so inches of the soil profile and hydrology (Figure 3.16).
It may be sufficient to use a soil probe to evaluate soils, but it is much more difficult to observe soil characteristics mentioned below. In addition, a shovel hole or pit will remain for many months, and the location of a given sample can be inspected by regulatory personnel at a later date.
Observe the excavation hole for standing water or seepage of water into the hole from the bottom or from the sides. Observe the conditions for fifteen to twenty minutes after the hole is dug. One may wish to dig holes at several nodes and rotate around the site to observe them over time. This can be accomplished by checking the hole after a certain time period has elapsed while one is conducting other evaluations at sample nodes nearby.
Note the hydrologic conditions. If water has seeped in, note the depth or distance from the soil surface to the water seepage surface and make notes. Also, check for gley or very wet soils resulting from very anaerobic conditions, sulfur or methane smell, and other indicators of wetland hydrology.
Check for surface manifestation of wetland hydrology (Figure 3.17). This would include rafted debris, “fat-based” tree trunks, sediment-stained leaves, or dark and wetted leaves or duff.
Describe the soil type found at each sample point. This could include general soil textural conditions, soil levels or horizons, and soil colors. Record whether sample points have similar or dissimilar soils to those indicated by the county soil survey.
These soil evaluations should include checking the Munsell Color Charts (Munsell Color 1990) for color, value, and chroma and checking for iron oxide mottling, the presence and depth of organic matter and organic soils, and the presence of manganese reduction products and/or grey or gley deposits.
Be sure to sample each soil layer encountered and record your findings. These layers are commonly called the “A” horizon or top soils, “B” horizon or subsoil, and the “C” horizon or parent material (USDA 1962, 1975, 1991; Foth 1990; Richardson and Vepraskas 2007).
For jurisdictional purposes, soils that exhibit more than one of these indicators, such as standing water or seepage, dark Munsell chroma (/2, /1), lots of mottling, thick layers of high-organic-matter soils, gleyed soils, or other products from highly anaerobic soil chemistry conditions, will be considered to be evidence of a hydric criterion (USACE 1987).
Salt cedar is a real problem in many states. It effectively kicks out native plants by depositing salt in adjacent soils. The plant provides limited forage for local wildlife. This example is from along the Colorado River in Arizona.
One should check for indicators of wetland hydrology such as seasonal high water conditions (Figure 3.18). Such conditions are usually defined as 7 to 14 days’ duration of flooding or high water table per year during the growing season. In other manuals or proposed manuals, these periods may vary between 15 days of flooding or 21 days of very high water table. These measures of duration of flooding may change in the future, so be aware of current requirements. Currently, the interpretation is two weeks of standing water or subsurface saturation during the growing season period as defined by the USDA soil survey for the county.
The end of a culvert provides a common source of periodic water where wetland plants can develop and flourish.
Record whether the soil and surrounding landscape exhibit hydrological indicators. At each sample point, note flood markings or rafted debris lines, shallow root systems, wet and/or poorly decomposed plant materials, adjacent stream courses, and other indicators of wetland hydrology mentioned in the Wetlands Delineation Manual (USACE 1987). In particular, look for a surface layer of undecomposed leaves and/or an absence of plant growth compared to adjacent areas or silt and clay deposits on leaves and tree trunks.
Wetland plants can develop wherever water appears. Impoundments, like this one behind Boulder Dam in Arizona, often drown other riverine system features, but new wetlands can quickly develop.
Evaluate the plants found at the sample site. The ground, shrub, vine and tree layers of the vegetation need to be described by the plant species that are dominant. Dominance is defined as 50% or more vegetation in the vegetative layer are composed of facultative plants (FAC), facultative wetland plants (FACW) or more wetland-loving plants (obligate or OBL).
It has been found to be appropriate to evaluate the ground layer of vegetation within a circle of radius of 10 feet centered at the sample point. The shrub layer should be described within a 20-foot radius and the tree layer within a 30-foot radius circle about the sample point. These radii have proven useful in wetland delineations and are based on suggestions in the Wetlands Delineation Manual (USACE 1987). This approach may be not be suitable if there are changes in future interpretations or manuals, due to local or regional conditions or due to the requests by other, so be aware of current requirements (Wakeley 2002; USACE 2010a–f).
It is also necessary to estimate the relative abundance of each dominant plant species based on the relative prevalence of the given species. This is then compared to the relative percentage abundance or cover to the total quantity of vegetation at each sample point.
This may be done by visual estimates, particularly if the observer is experienced in this method of estimation. The Wetlands Delineation Manual (USACE 1987; USACE 2010a–f) and other sources provide additional dominance estimating procedures, but the visual estimate is both field expedient and accurately performed with practice.
The plant species data and the dominance estimates in percentage are used to identify the common plants at the sampling site. The wetland determination procedure is presented in the Wetlands Delineation Manual (USACE 1987) and other supplements and sources (Federal Interagency Committee for Wetlands Delineation [FICWD] 1989; USACE 2010a–f), and the same or similar techniques are addressed in scholarly books or journals (Mueller-Dombois and Ellenburg 1974; Lyon 1993, 2001). The procedure consists of determining whether 50% of the dominant plants have a high probability of occurring in wetlands (USACE 1987).
The National List (Reed, 1988; http://www.wetlands.com/fws/plants97.htm) records the plants species and their agreed-upon categories of probability of occurrence in wetlands. Wetland plant species do vary in their probability of occurrence from one region to another, and hence the probabilities are listed by the geographical region of interest. One uses the intermediate-level recording sheets to record and sum the percentage coverage of dominants that are listed as types facultative FAC, FACW, and OBL wetland plants species.
It is desirable to plot the locations of the sampled points on an available topographic map or engineering-style planimetric or plan map or GIS map and to supply the boundaries of any jurisdictional wetlands (Figure 3.19). It may also be desirable, though not necessary, to present the boundaries of any hydric soils encountered on a separate map. These boundaries will make a nice contrast with any USDA hydric soil boundaries shown on the soil survey map.
To make a finding that an area is a jurisdictional wetland it is necessary to (1) have hydric soils, (2) have evidence of wetland hydrology, and (3) find that 50% or more of the dominant plants have a high probability of occurring in a wetland.
All three of these criteria must be satisfied. Failure to meet one or more of the three criteria means that the area is not considered a wetland for jurisdictional purposes.
Use other sources of data and field checks to determine the adequacy and accuracy of mapped jurisdictional wetland boundaries. Check and recheck your work. Adjust boundaries as necessary and determine the acreage of the actual jurisdictional wetlands. Supply the acreage estimate in the comprehensive/intermediate wetland assessment report.
It is also desirable to check and pace the location and size of the wetland and ensure that its characteristics have been correctly mapped. Double-check the dimensions of the wetland by pacing or other measurement technique to ensure that the area estimates are correct. It may also be necessary to flag the actual boundaries of the wetland on the ground, to facilitate surveying of boundaries or to facilitate inspections by the USACE.
Flood waters can create temporary riverine systems and establish conditions for more permanent wetlands. Desert systems are particularly well adapted to both activate and procreate in a short time span and even in alternate years if necessary. The scene is from Santa Clara River floodplain in Tucson, Arizona.
Allow a period for evaluation of products by the client. Incorporate comments and criticisms and produce final products identifying jurisdictional wetland areas.
At this point the wetland report may be filed or the information used in planning and management of the wetland resource. A sample intermediate-level report is provided in Lyon (1993). Please note that in USACE (1987) Appendix C in the reference is outdated as are some other paragraphs and equivalent information must be obtained from regional wetlands-related offices such as USACE or Regional Supplements to the Corps of Engineers Wetland Deliniation Manual (USACE 2009a–b, 2010a–f).
These products and a report summarizing the methods used in their production may be submitted as a wetland assessment to the U.S. Army Corps of Engineers in support of CWA section 404 permitting activities. Note that the requirements for and types of permits as well as reporting requirements change over time. It is desirable to become familiar with the permitting requirements in the area of study before work begins. Follow the requirements and deadlines such that permitting is an orderly process.
The information and methods provided above lend some insight and appreciation of the complexities involved in wetland evaluations. Comprehensive/intermediate-level methods and reporting can be useful in a number of applications, and they provide a good, general model of how to acquire and present data for determination of jurisdictional wetlands.
The comprehensive/intermediate-level report is very suitable for permitting activities and often represents the minimum of detail necessary to support a finding of jurisdictional wetlands, depending on reporting requirements.
It is particularly desirable to document the preconstruction conditions of a given property using these techniques, even if no jurisdictional wetlands are found. Completion of a comprehensive intermediate report provides good documentation if questions arise after initiation of construction, and it is good evidence of due diligence on the part of the landowner in fulfilling responsibilities related to wetlands.
Comprehensive Advanced-Level Procedures
In certain situations it may be necessary to use additional techniques to augment those presented above or described in the Wetlands Delineation Manual (USACE 1987). The need for comprehensive procedures to supply great detail may be manifest by the complexity of the wetland or the complexity of the terrestrial and aquatic interface.
Detailed, comprehensive/advanced-level procedures may be necessary because the status and extent of the wetlands are in contention. Other needs may be dictated by the presence of a unique plant or animal species that uses the wetland as a habitat or home and hence wetland characteristics must be detailed for more than the simple needs of identifying a jurisdictional wetland and CWA Section 404 permitting activities. There may also be local or state requirements or requirements of water quality reporting and permitting within a state based on CWA Section 401 “State Certification of Water Quality.” All are reasons to add more detail to the evaluations.
The following chapters supply a number of methods that may be used to augment the comprehensive/intermediate-level procedures and reporting. Some of these methods are defined as comprehensive-type methods in the Wetlands Delineation Manual (USACE 1987) and other scholarly works (e.g., USACE 2009a–b, 2010a–f). Other approaches are suggested by the authors or colleagues based on personal experience.
All these techniques provide a higher level of detail and can be used to customize the wetland evaluation process to meet the unique characteristics of a particular site or jurisdiction or both.
Federal Interagency Committee for Wetlands Delineation. 1989. Federal manual for identifying and delineating jurisdictional wetlands. Washington, D.C.: U.S. Government Printing Office.
Foth, H. D.
1990. Fundamentals of soil science. New York, N.Y.: John Wiley.
. 1993. North American Landscape Characterization (NALC), Landsat Pathfinder technical plan. EPA 600/X-93/009. Las Vegas, Nev.: U.S. Environmental Protection Agency.
2001. Wetland characterization: GIS, remote sensing, and image analysis. Oxford, U.K.: Taylor & Francis.
. 1974. Aims and methods of vegetation ecology. New York, N.Y.: John Wiley.
1988. National list of plant species that occur in wetlands: National summary. Washington, D.C.: U.S. Department of Interior.
. 2007. Wetland soils: Genesis, hydrology, landscapes, and classification. Boca Raton, Fla.: CRC Press.
U.S. Army Corps of Engineers. 1987. Corps of Engineers wetlands delineation manual. Technical Report Y-87-1. Vicksburg, Miss.: Environmental Laboratory, U.S. Army Engineer Waterways Experiment Station.
U.S. Army Corps of Engineers. 2009a. Interim regional supplement to the Corps of Engineers wetland delineation manual: Caribbean Islands region. ERDC/EL TR-09-8. Vicksburg, Miss.: U.S. Army Engineer Research and Development Center.
U.S. Army Corps of Engineers. 2009b. Interim regional supplement to the Corps of Engineers wetland delineation manual: Northcentral and Northeast region. Wetlands Regulatory Assistance Program, ERDC/EL TR-09-19. Vicksburg, Miss.: U.S. Army Engineer Research and Development Center.
U.S. Army Corps of Engineers. 2010a. Regional supplement to the Corps of Engineers wetland delineation manual: Great Plains region (Version 2.0). ERDC/EL TR-10-1. Vicksburg, Miss.: U.S. Army Engineer Research and Development Center.
U.S. Army Corps of Engineers. 2010f. Regional supplement to the Corps of Engineers wetland delineation manual: Midwest region (Version 2.0). ERDC/EL TR-10-16. Vicksburg, Miss.: U.S. Army Engineer Research and Development Center.
2002. Developing a “regionalized” version of the Corps of Engineers wetlands delineation manual: Issues and recommendations. ERDC/EL TR-02-20. Vicksburg, Miss.: U.S. Army Research and Development Center.