Thought Leadership

Navigating the Murky Waters: A Guide to Wetland Delineations

April 25, 2023

Staff performing wetland delineation

By Mari Olson – Wetland Ecologist

Before we dive into the topic of wetland delineation and why you might need one, let’s first understand what a wetland is. What comes to mind when you hear the term “wetland”? Most people, conjure images of a swamp, marsh, or bog. However, there are numerous classifications and contrary to popular belief, wetlands don’t have to be wet all the time.  Many wetlands can be farmed, mowed for hay, maintained as lawns, or used for other purposes.

Simply, a wetland is an area of land that remains inundated or saturated by surface or groundwater at a frequency and duration sufficient to support plant species that are tolerant of prolonged inundation or soil saturation. In these areas, the presence of water is the primary factor controlling the plant and animal communities living in wetlands.

Wetlands provide a variety of ecosystem services which include water purification, flood control, recreation, and habitats for numerous wildlife species. And that is why wetlands are protected by federal, state, and local regulations. Because wetlands are protected, if your project involves impacts to a wetland in any way (i.e., build a new road or a new development project), then you’ll need to perform a wetland delineation first.

What is a wetland delineation?

A wetland delineation is a process of identifying the boundaries and characteristics of a wetland area in accordance with the standards set by the U.S. Army Corps of Engineers (USACE) and the Environmental Protection Agency (EPA).  They are performed to determine if a site is subject to regulatory protection under the Clean Water Act, which aims to safeguard the nation’s waters and wetlands. Additionally, delineated wetlands may be subject to additional state and local regulations depending on your project’s location.

A wetland delineation typically involves four main steps:

  1. Preliminary assessment: This involves reviewing existing data sources such as topographic maps, aerial photographs, national and state wetland inventory maps, and soil surveys to identify potential wetland areas on the site.
  2. Field Investigation: This phase requires boots on the ground to confirm whether the suspected wetland areas identified during the preliminary assessment have the three necessary wetland parameters to be considered a wetland. The required parameters are hydrology or the ability of an area to hold water, the presence of wetland vegetation, and hydric soil characteristics. These wetland parameters are evaluated using a series of standard methods and technical guidelines established by the USACE and EPA.
  3. Delineation Report: This document summarizes the methodology and results of the field investigation and includes scaled maps that depict the wetland boundaries and types of wetlands present as well as the location of all data points and the area of investigation for the delineation project.
  4. Agency Concurrence: This phase requires regulatory agencies to confirm that the wetland boundaries identified in the wetland delineation report are accurate and that proper delineation procedures were utilized during the field investigation and properly documented in the report. The USACE issues federal wetland delineation concurrence. In addition, state agencies and local counties and municipalities with wetland regulations will also issue wetland delineation concurrence. Often, a wetland delineator will complete an on-site visit with regulators as part of the concurrence process.

Why is a wetland delineation important?

Wetland delineations are essential in providing information about the location, extent, and characteristics of wetlands on a particular site. They inform land-use decisions by identifying areas that are subject to regulatory protection under the Clean Water Act. Developers can use these reports to determine the feasibility of their projects and make informed decisions about how to approach potential wetland impacts.

In addition, wetland delineations provide valuable data for wetland restoration and conservation efforts.  These reports can help inform the design of restoration projects, guide the selection of appropriate plant species, and assist in monitoring the success of restoration efforts.

Who can perform wetland delineations?

Wetland delineations must be conducted by qualified and experienced professionals with the necessary knowledge and training to implement the applicable regulatory guidelines and methods accurately. These professionals may include biologists, ecologists, botanists, or soil scientists.

The qualifications required to perform a wetland delineation may vary depending on state and local regulations. In general, wetland delineators must complete a minimum of 40 hours of training in wetland identification and delineation methods. These individuals must also have a strong understanding of the local ecology, geology, hydrology, and plant and animal communities associated with wetlands.

The bottom line

A wetland delineation is a vital process in protecting and conserving important ecosystems. It provides valuable information to landowners, developers, and regulatory agencies to ensure that land-use decisions are sustainable and any unavoidable impacts to wetlands are minimized. By adhering to established wetland delineation protocols, we can safeguard the ecological integrity of our wetlands while allowing for responsible development and use.

Contact me, Mari Olson, to discuss how GEI can help with delineating wetlands on your projects.