Wetland Delineations

What is a Wetland Delineation?

A wetland delineation determines the boundary between uplands and wetlands on a property following guidelines established by the United States Army Corps of Engineers (USACE). It involves identifying, characterizing, and mapping wetlands based on soil, vegetation and hydrologic characteristics. The process of delineation involves a combination of fieldwork, data analysis, and consultation with regulatory agencies. In the field, a skilled wetland scientist evaluates the site’s characteristics for key indicators such as wetland hydrology, hydric soils and hydrophytic vegetation, which define wetland ecosystems (See “What is a Wetland?”). These findings are then meticulously mapped and documented to delineate the precise boundaries of the wetlands on the property.

Why Do I Need a Wetland Delineation?

Because of their benefits (e.g., habitat, water quality improvement, stormwater storage, carbon sequestration), wetlands are important and regulated ecosystems in the United States. The U.S. Environmental Protection Agency (EPA) generates and enforces policies that avoide or minimize adverse impacts to wetlands when possible. A wetland delineation is needed whenever there is a potential impact on wetland areas due to land development projects. By identifying and mapping wetland boundaries accurately, stakeholders can make informed decisions that prioritize the conservation and sustainable use of these vital ecosystems.

A wetland delineation is also necessary if an activity negatively impacts a wetland to determine the amount of “compensatory mitigation” needed.  Compensatory mitigation could mean several things:

    • Restoration: Re-establishing or rehabilitating a degraded wetland.
    • Establishment: Creating a new wetland where one did not previously exist;
    • Enhancement: Improving existing one or more wetland functions; or
    • Preservation: Using legal and physical mechanisms to protect or enhance an existing, ecologically important wetland.

As a developer or project decision-maker, wetland delineation and its potential findings may appear daunting. Here are some common concerns and why they might be causing unnecessary worry:

  1. Limited Expertise: Wetland delineation demands specialized knowledge and skills. Collaborating with an experienced consultant can help alleviate uncertainties and ensure precise determination of wetland boundaries.
  2. Regulatory Complexity: The rules governing wetland delineation and permitting can be intricate and difficult to decipher. Partnering with a consultant well-versed in regulatory compliance and environmental permitting is essential for success.
  3. Time Constraints: Tight project schedules can amplify the pressure. Recognizing the significance of meeting deadlines is crucial, along with harnessing cutting-edge technology and tools to enhance efficiency and accuracy.
  4. Cost Considerations: Wetland delineation may seem like an added expense, particularly for larger projects. However, investing in this process upfront can prevent substantial costs and complications later on if a wetland that was not known about is disturbed during construction.
  5. Potential for Disruptions: Delineations may reveal previously unidentified wetland boundaries, potentially causing delays or interruptions during permitting. Addressing these discoveries early is key to minimizing project disruptions.

The process of identifying and delineating wetlands is complex. Contact Comite Resources, an environmental consulting company with a knowledgeable and experienced staff, to provide expertise and support throughout the entire process.

What is a Wetland?

A wetland is an area where water is present either on the soil surface or within the plant root zone for a portion of the year and contains vegetation adapted to wet soils. Wetlands are diverse ecosystems that bridge the gap between terrestrial and aquatic environments. They’re incredibly important because they provide habitat for a wide variety of plant and animal species, help control flooding by absorbing excess water, improve water quality by removing pollutants such as excess nutrients, and help maintain biodiversity.

Wetlands include marshes, swamps, bogs, and areas along water bodies such as bayous or lakes. Wetlands dominated by trees are called swamps and wetlands dominated by herbaceous (i.e., non-woody plants) plants are called marshes. Wetland vegetation species distribution is determined by hydrology, specifically length and depth of soil surface flooding.  A typical wetland will emerge from an adjacent water body into the shallow aquatic zone where floating or rooted plants grow to the marsh zone where herbaceous (non-woody) plants grow.  Beyond the marsh, at a slightly higher elevation, may be a shrub/scrub area with short woody and herbaceous vegetation that, grades to swamp dominated by bald cypress trees at lower elevations and longer flooding times.

(top) Schematic of idealized freshwater wetland zonation. (bottom) Actual freshwater wetland zonation in a coastal Louisiana wetland.

There are seven major types of wetlands, classified as either coastal or inland, in the United States. These wetlands exhibit considerable diversity due to variations in soil type, topography, climate, hydrology, water chemistry, vegetation, and various other factors. They support a rich biodiversity and span across diverse landscapes and range from the icy tundra to the lush tropics, and are present on every continent except Antarctica.

 

Wetland Type Dominant Vegetation Dominant Hydrology
Coastal Wetlands
 

Tidal Salt Marsh

Herbaceous – ex: smooth cordgrass  

Tidal

Tidal Freshwater Marsh Herbaceous – ex: maiden cane Tidal
Mangroves Woody – Mangrove trees Tidal
Inland Wetlands
 

Inland Freshwater Marsh

 

Herbaceous – ex: cattails

Rivers, streams, precipitation, watershed runoff
Northern Peatlands Herbaceous – ex: moss Precipitation
 

Southern Deepwater Swamps

Woody – ex: bald cypress, water tupelo Rivers, streams, precipitation, watershed runoff
 

Riparian Wetlands

Woody – shrubs and trees, ex: buttonbush and willow, Rivers, streams, precipitation, watershed runoff

 

Wetlands are important and diverse ecosystems that provide economic benefits to society.  For example, coastal mangrove wetlands can protect houses from intense wind and storm surge (Figure 2).

Figure 2. Coastal forested wetlands provide protection from wind and storm surge (Image from D. E. Marois and W.J. Mitsch (2015). Coastal protection from tsunamis and cyclones provided by mangrove wetlands – a review. International Journal of Biodiversity Science, Ecosystem Services & Management 11:1:71-83, DOI: 10.1080/21513732.2014.997292.

State and federal legislation, such as Section 404 of the Clean Water Act (CWA), exists to protect wetlands.  Wetlands determined to be ‘jurisdictional wetlands’ (as delineated using Section 404 of the CWA) have their uses regulated by agencies such as the U.S. Army Corp of Engineers, including wetlands on private property.  So, What is a jurisdictional wetland?  Sign up to receive additional information.