Watch and Learn Now:
How To Do A Wetland Delineation

June 20, 2018

For most people, the words swamp, marsh, bog or wetland mean a peaceful pond with cattails, water lilies, waterfowl and frogs. But contrary to popular belief, wetlands are not always wet.

Some wetlands are farmed, mowed for hay or maintained as a lawn. The Clean Water Act, all wetlands, according to the U.S. Army Corps of Engineers (COE) share these characteristics:

  • Hydrology – the degree of flooding or soil saturation. The period of soil saturation varies according to several factors, including the climate conditions, soil texture and permeability, wetland type, the geographic location of the wetland and man-made disturbances.
  • Soil – wetland or “hydric” soils are soils formed in conditions of saturation (or wetter) long enough during the growing season to develop characteristics unique to wetlands. Depending on location, there are approximately 20 “hydric soil indicators” that can identify a soil as a wetland.
  • Vegetation – wetlands are dominated by “hydrophytes” – water-loving plants. To determine if a plant community meets wetland criteria data is collected to evaluate if a community is dominated by hydrophytes. The COE has defined the “hydric indicator status” of more than 1,400 species of plants usually found in wetlands. Five categories describe these plants. After identifying and making a comprehensive list of the plants located in the community, a delineator will calculate the dominance of hydrophytes using several methods.

Benefits and purpose of a wetland

Wetlands are essential and provide several ecological, economic and social benefits, which is why policies are in place when developing in or around wetland areas. Wetlands provide habitat for fish, wildlife and plants; recharge groundwater and reduce flooding; provide clean drinking water; offer food and fiber; and support cultural and recreational activities. And because of this, wetlands are protected by federal, state and/or local regulations.

When do I need to do a wetland delineation?

If you are planning a development project, building a new road or have an agricultural field that needs draining where a wetland may be disrupted or impacted, a delineation is your first step. A delineation tells you precisely the wetland location within your project plan. To obtain a permit for impacting a wetland, the delineated wetland boundary must be approved by the COE and often other local agencies that may have regulatory authority.

The best time to conduct a wetland delineation is during the “growing season,” the part of the year when soil temperature (measured 20 inches below the surface) is above biological zero (5°C or 41°F). A bud break on woody vegetation and visible “green-up” denoting active vegetation growth is also a proxy for the start of the growing season. Plants dying or entering dormancy mark the end of the growing season. The growing season varies considerably both year to year and geographically.

How to conduct a wetland delineation

A wetland delineation should result in three findings:

  1. Delineation results map – this map should clearly define the boundaries of each delineated wetland or stream, the location of all data points and the area of investigation.
  2. Boundaries – wetland and tributary boundaries should be clearly marked in the field with wetland flags to aid in agency verification.
  3. Report – should include the delineation methods, results, data forms documenting the findings, photographs, climate conditions before and at the time of the delineation and other relevant figures.

Step one – resource review

Whether it is a small or large wetland delineation project, a delineator should prepare by researching the project area. This involves using mapping products such as aerial photographs and soil maps to identify potential aquatic resources. Some essential resources available:

  1. Aerial photos
  2. National Wetlands Inventory – U.S. Fish and Wildlife Service (USFWS)
  3. Soil Survey by Natural Resource Conservation Service (NRCS)
  4. Topography
  5. Relative local or state-level maps that could exist for wetlands (e.g., state Departments of Natural Resources often have localized maps of known wetlands and aquatic resources)

If you are working on a smaller project, merely having a map is all you need. But if you are working on a larger project, you may be on a team, so it’s best to determine in advance who will cover what areas.

I always try to import project limits in the Global Positioning System (GPS) unit so I always know where I am on the site in respect to the proposed project. I don’t want to delineate too much or too little.
Rebecca Beduhn, SEH Natural Resource Scientist

Step two – field gear + field procedures

So, you’re ready to head out on a wetland delineation. But before you go, do you have the essential field gear? Here’s a check-list of the essential wetland delineation field gear recommended to help do your job, or make it easier:

Delineator items

Additional field gear to pack and prepare for your wetland delineation include:

  • Cell phone
  • Waterproof field camera
  • Soil knife
  • 2-way radios or “Spot” phone for working in remote areas
  • Rain jacket
  • Water and lunch for long days

Now that you’re prepared with the recommended essential wetland delineation gear and a plan, you’re ready to venture to the project site and begin the wetland delineation.

When you arrive at the project site, where do you begin? Is there an exact “start line” and “finish line”?

“Generally, you can start anywhere,” says Beduhn. “I look at the vegetation around me, review the locations from my resource mapping and begin the delineation with a sample point.”

These are the field procedures to follow in both upland and wetland areas:

1. Look at the vegetation around you. What types of vegetation do you see? It’s not uncommon to find vegetation in both upland and wetland areas. Rebecca will sometimes touch the vegetation to determine what the plant is. For example, Bedhun could feel edges on one plant picked during a delineation, and as a result, could identify the plant. “It helps to remember ‘sedges have edges’,” said Beduhn. “Many sedges are found in wetlands, but not all of them. It’s important to identify the type of sedge to determine the hydric indicator status of that species.” Other interesting vegetation found in this particular delineation is “sticky Willy.” Botanists won’t call it sticky Willy — they use the scientific names. Rebecca says some of the descriptive, common names can be helpful to remember a particular plant species. Other vegetation includes milkweed and reed canary grass – both of which can be found in uplands and wetlands. When you locate an area where the dominant vegetation is hydrophytic (grows in wetlands the majority of the time), you are on the right track to finding your wetland boundary.

2. Locate the topographic (topo) break. While not an accurate indicator, wetland boundaries are often associated with changes in topography, where the wetland is predominantly lower in the landscape.

3. Complete a soil sample.

  1. Use an auger, begin digging a hole or “pit” into the ground.
  2. With each dig the contents in the auger are placed on the ground around you (note: the soil is placed on the ground in the order in which it was extracted to recreate the entire soil profile from the top to the bottom of your pit).
  3. Dig a hole — typical soil depths are generally 18-24-inches below the ground to:
    • Observe the soil to determine the presence or absence of hydric soil characteristics
    • Observe hydrology including depth to the water table and saturated soils
    • Identify disturbances
  4. Refer to the Munsell Soils Color Chart book to identify soil color by:
    • Hue – dominant color of the soil [i.e., Red (R), Yellow-Red (YR), Green (G), Green-Yellow (GY) and so on]
    • Value – light and darkness of the soil (i.e., the value indicates with a number like 2, 4, 6 and so on)
    • Chroma – purity or strength of the soil color (i.e., the value indicates with a number, typically in the range of 2-14)
  5. According to the United States Department of Agriculture (USDA), three particle sizes make up soil texture: sand, silt or clay and all mineral soils are comprised by one or more of these soil textures. Organic soils may contain these soil particles but also dominated with dead organic matter derived from decaying vegetation and other biota found in soil.
  6. Determine soil texture by employing the “feel analysis” flow chart.
  7. Place a pink wetland delineation pin flag into the ground denoting the location of the soil profile and record the point into the GPS.

Additional conditions to note during a wetland delineation is the temperature (higher or lower than normal) and precipitation (wetter or drier than normal).

Watch Beduhn in this video as she goes through the step-by-step of a soil sample.

Step three – the draft report

Content of a wetland delineation report consists of:

  • Introduction – site description and purpose for the delineation
  • Wetland delineation descriptions and methods – definition, methodology, hydrophytic/wetland vegetation, hydric/wetland soils, hydrology
  • Results – description of the wetland identified and regulatory considerations
  • Bibliography
  • Tables, figures and appendices

After the draft report is prepared, the project owner then engages a wetland regulatory agency to review and confirm the results.

“We are all humans and vary in our approaches and analysis,” says Rebecca. “If the conditions change or something wasn’t identified accurately in the initial delineation, we fix it.”

In Minnesota, an approved wetland delineation is valid for five years, so long as conditions have not changed the boundary of that wetland during the five years since the initial approval.

Wetland classification

Scientists classify dozens of wetland types, characterized by vegetation, soil type condition and degree of saturation or water cover. Agencies may require one or more of these types for all wetland delineations. In Minnesota, wetlands are classified three ways:

  1. U.S. Fish & Wildlife Service Circular 39 – identifies wetlands, lakes and streams based primarily on hydrology. The publication defines eight wetland types in Minnesota.1
  2. Cowardin – incorporates information on landscape position, plant communities and hydrology. This publication defines five main types of wetlands with numerous subcategories and modifiers. It is also the classification system used for wetlands described in the National Wetlands Inventory.2
  3. Eggers and Reed – a descriptive approach based on wetland plant communities occurring specifically in Minnesota and Wisconsin. This publication describes 15 types of wetlands.3

Wrapping it up

Wetlands are essential landscapes that provide ecological, economic and social benefits to the human and natural environment. This lends to strict policies for working in or near wetlands. Before you start your next project, following the steps and procedures for a proper wetland delineation is a basic and primary tenet to keep your project moving forward.

About the Author

Rebecca Beduhn

Rebecca Beduhn is a nationally-certified professional wetland scientist, Minnesota professional soil scientist-in training, and a Minnesota certified wetland delineator specializing in hydric soils. She is committed to preserving our environment and spends her days conducting wetland assessments and delineations, preparing regulatory permitting documents and mitigation site monitoring. Contact Rebecca


  1. Shaw, S. P. and C. G. Fredine. 1956. Wetlands of the United States. U.S. Fish & Wildlife Service, Circular 39.
  2. Cowardin, L., M., V. Carter, F. C. Golet and T. T. LaRoe. 1979.
  3. Eggers, S. D., and D. M. Reed. 2014.

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