Wetland Delineation: What It Is and Why It Matters

Wetland Delineation: What It Is and Why It Matters

Wetland Delineation Definition

Wetland “delineation” is a phrase used to describe the process of conducting field surveys in order to establish the exact borders of a wetland.  It involves a detailed study of the soils, hydrology, vegetation, and wildlife of the wetland.

The regulation definition of a wetland, as well as any additional criteria, are used by a wetland delineator. Wetlands are defined, mapped, and delineated by their vegetation.

Delineation is the act of locating the wetland or watercourse’s boundary or border Delineation also entails describing the wetland or watercourse’s functions and values in terms of its physical location in the landscape.

Regulations at all levels of government use wetland delineation to determine a wetland’s presence (location) and physical boundaries (size).

It is also necessary to determine the boundaries of wetland areas before making a final decision about who has jurisdiction over the area. This procedure determines which bodies of water within a project’s limits fit the definition of “Waters of the United States.”

Fish and Wildlife Service, the body responsible for assessing the impact on fish and wildlife of projects subject to Section 404, defines a wetland as having three characteristics:

  • Hydrophytes, a type of plant that thrives only in or near water, can be found on the land at least occasionally.
  • Hydric soil is the dominating subsoil, or layer, beneath the surface.
  • For each year, a different non-soil substrate is used that is soaked or partially submerged in water at some point throughout its growing season.

For the most part, wetland habitats are areas of land where specific types of vegetation and animal life can thrive due to the soil type and the long-term presence of water in or on the soil.

What Is Involved In A Wetland Delineation?

A wetland delineation is an assessment of the wetland boundaries and features. The purpose of the wetland delineation is to identify the wetland boundaries and determine the wetland’s classification.

The delineation process includes the collection of field data, mapping, and verification of the wetland boundaries.

The field data collected includes water level measurements, soil samples, and vegetation surveys. The mapped data is then analyzed to identify wetlands and other jurisdictional features. The verified boundaries are then used to develop a wetland delineation report.

For a “simple” delineation, a trained specialist gathers and documents the wetland boundaries based on land-use maps, aerial photographs, topographic maps, soil surveys, and other information.

Additional information about the potential impact of the project may be needed for certain levels of federal or state approval.

Other types of delineations are more complex and require more work.

For those types of delineations, a qualified wetlands specialist must first survey the land, estimate the wetland area (often called “buffer”) using local knowledge and existing maps, and determine which wetland’s boundaries encompass all or most of the area being considered for a project.

The number of different types of wetland delineation varies, as do their specific requirements and standards.

Why Wetland Delineation Matters

The following outline why wetland delineation matters.

  1. Land developers and engineers rely heavily on wetland delineations to help them avoid any potential snags that could slow or halt the progress of their plans. The degradation of wetland habitat can be avoided if the borders of a parcel of land are precisely identified.
  1. Wetland delineations also help ensure that local and state government regulations are followed, since development outside of the delineated boundaries is unlawful. For example, water development projects that require approval by federal agencies (Clean Water Act, Section 404) may contain limits to the size of a project that can occur without approval. Wetland delineations are a key piece of documentation to determine the exact boundaries of wetlands that need approval from the government, which in turn sets the legal limit for the amount and type of wetland impacts that can occur.
  1. In some cases, wetland delineations are used as a route-clearance criterion for certain types of federally funded projects. For example, the U.S. Army Corps of Engineers (USACE) often requires that wetlands be delineated and photographed prior to a project’s approval, to prove that the land is navigable, meaning that it is not a wetland.
  1. Wetland’s delineations also provide the basis for identifying mitigation opportunities for mitigation banks – accounts of credits for restoring and protecting wetlands – as well as determining the boundaries of compensatory mitigation areas required by Section 404 permits.
  2. Compensatory mitigation areas help ensure that any project’s wetland impacts can be mitigated by reducing or removing the impact elsewhere in the watershed. For example, if a project causes significant wetland impacts, these areas help ensure that other projects within the watershed are not negatively impacted in the same way.
  1. Wetland delineations also provide a legal and practical basis for individual landowners to sue developers over potential environmental issues resulting from development within their property.
  2. In some cases, companies with pre-existing water rights to a wetland may want to develop that land themselves, in order to increase their water supply and maintain or increase their value. It is often necessary to hire a wetland delineator to determine the location of legally owned wetlands on an individual’s property.
  1. Wetland delineations also provide a legal basis in most states for placing limits on the amount of development that can occur within certain watersheds. In many cases, if a wetland is not delineated, then private landowners are not legally obligated to reduce impacts to their property from development.
  1. Wetland’s delineations may be used to determine which wetlands are part of federally protected areas, such as national parks and wildlife refuges.
  2. Wetland delineations can be used to determine if certain types of development (such as the massive Asian carp threat in the Great Lakes) require mitigation actions.

The delineation process can also provide information that will help inform federal, state and local agencies about potential environmental impacts.

  1. Wetland delineation also helps to identify which land features are suitable for specific purposes, such as conservation or restoration.

Wetland Delineation Importance

Some aspects that make water delineation important are as follows:


The single most important reason for delineating jurisdictional wetlands is to ensure that the hydrology of a wetland is not disturbed by any activities that may affect the water or land around the wetland.


Waters of the U.S. must be delineated on all permits, leases, plans and maps to determine who has jurisdiction over that water body.


For each project involving jurisdictional wetlands, every decision made in regard to the project must consider where water bodies are located within the project’s limits to avoid delays in getting necessary permits and approvals for a project.


Delineating a jurisdictional wetland may save time and money when determining if a permit or other requirement is necessary.

For example, to determine if a permit or other requirement is necessary for a non-federal industrial facility, the water bodies should be delineated.

There may be a need to do certain permits that will not require an EAD (Environmental Assessment and Determination) as long as the water bodies were delineated.

In addition, an EAD is required by federal agencies such as the U.S. Fish and Wildlife Service; Army Corps of Engineers; U.S. Geological Survey; EPA, etc. for every project that affects a jurisdictional wetland.


To determine if a permit or other requirement is necessary, it is important to know who has jurisdiction over jurisdictional wetlands.

Depending on the activity, an EAD may not need to be done for the project if the water bodies were delineated properly and it is determined that there are no jurisdictional wetlands within the proposed project limits


Any wetland delineations should be accurate and up-to-date.

The delineation process helps to ensure that the water bodies are located within the proposed project limits to avoid delays, harm to ecosystem and costs in getting necessary permits.

In Conclusion

The delineation process is the most important process of determining jurisdictional waters in any project that involves wetlands.

Without accurate and timely wetland delineations, it will be difficult for companies to submit the necessary permits, plans, and maps.

Landowners will face unnecessary delays in getting necessary permits and approvals for development projects that would require a wetland inspection or mitigation bank.

In case of any litigation, it will be difficult for the plaintiffs to prove their claim in terms of water bodies being located within the project limits.

Delineating is a tedious process, but once you are through with the process you will have a long-term benefit from it.

Water Delineation FAQs

What is a wetland delineation?

A wetland delineation is a process of locating the location of a water body or wetland. The delineation process helps to identify the boundaries of a wetland and any potential impacts that may occur as a result of activities within the wetland.

Delineate means to show the exact location of a border or boundary. The delineation process includes fieldwork, data analysis, and report preparation.

How long does a wetland delineation take?

Wetland Delineations take approximately two weeks to complete and cost approximately $100 to create. Most surveys will begin working on your property within 24 hours of your request.

Is a wetland delineation required?

A wetland delineation is required if you are developing property, planning to build on your property, or have wetlands on your property that may require special permitting.

How do I hire an environmental consultant?

Suppliers or soil and water conservation districts can usually provide a list of qualified consultants that have completed work in your area. It is always recommended to interview at least three or four consultants for your project.

Why is wetland delineation important?

A wetland delineation is important because the boundary delineation of a water body is used to determine if a wetland will affect an area that is adjacent to a wetland.

It can also be needed by the general public to determine if they need to take any special precautions when entering a wetland.

What are some examples of activities that may affect wetlands?

Some examples of activities that may affect wetlands include: building roads, construction, agriculture, and private development (i.e., cottages or vacation homes).

Who does wetland delineation?

Wetland delineation is done by volunteers, contractors, and other state and federal agencies.

Who owns wetlands?

Wetlands are owned by the public and are usually administered by the State Fish and Wildlife Department or the private landowner.

What is required for a wetland delineation?

A wetland delineation requires a fee to determine who has jurisdiction over certain jurisdictional water bodies. The contractor should provide you with a written statement of work that defines what will be included in your project (i.e., field work, on-site inspections and adjoining property).

How much does wetland delineation cost?

A wetland delineation generally costs between $100 and $300. The fee depends on the size of the property and the duration of the project.

What are some examples of wetlands that I may encounter while building?

Wetlands that may be encountered while building include: ponds, swamps, marshes, bogs, fens, and floodplains. These types of wetlands can be found in lowlands near streams or rivers or on higher land with good drainage characteristics.

What should I do if the delineation I receive from my contractor is different from what I expected?

If the delineation is different from what you expected, you can request a refund of up to 50% of your money back.

You may also contact your local soil and water conservation district for additional information about the process for requesting a refund

How do you get wetland delineation experience?

Students are tested in a nearby marsh while their teacher is on the other side of the world. A passing grade of at least 80 percent is required to become a Certified Wetland Delineator after completing the course. The course normally consists of 160 hours.

What is the difference between wetland delineation and mapping?

Mapping wetland boundaries involves creating a map that shows the location of all constructions, roads, and other structure that are located near wetlands.

The delineation is a document that shows the different jurisdictions over a wetland, who the landowner is, and what the values are of the wetland.

Wetland hydroperiod definition?

It is the balance between inflows and outflows of water, soil contours, and subsurface conditions that constitutes a wetland’s hydrologic signature.

Characteristics of wetland soil?

Soggy soils, water-loving plants, and water are three of the most common characteristics of wetlands.

Hydric soils, hydrophytic vegetation, and wetland hydrology are all terms used by scientists. The delayed decomposition of organic material in certain soils can lead to large levels of organic matter.

What does delineate mean?

Delineate means to show the exact location of a border or boundary.

What are the main purposes of delineating wetlands?

The following are three main purposes for completing a wetland delineation.

  • to define jurisdictional boundaries
  • to determine if mitigation is required
  • to understand the physical and biological characteristics of an area.

How long is a wetland delineation good for?

According to the regulations, the Corps letter must provide an explanation of why the wetlands delineation is only effective for a three-year period from the date of the letter.

What should I do if my wetland delineation has expired?

You should reapply as soon as possible so that your wetland delineation can be extended.

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