Wetland delineation resources

What is wetland delineation? Wetland delineation establishes the existence (location) and physical limits (size) of a wetland for purposes of federal, state, and local regulations.

Wetland delineation is also an element of a jurisdictional determination. This process identifies which water bodies within a project's boundaries meet the definition of "waters of the United States." For more information on this, see the U.S. Army Corps of Engineers (Corps) Regulatory Guidance Letter 16-01 Jurisdictional Determinations.

Important: The Corps, not applicants or their consultants, determines whether or not a wetland is a "water of the United States," which are regulated under the federal Clean Water Act. If the Corps determines a wetland is not subject to the Clean Water Act, the wetland may still be a "water of the state" and subject to regulation by Ecology and local jurisdictions. We do regulate wetlands determined by the Corps to be non-jurisdictional due to their isolation from navigable waters. (More on isolated wetlands)

Use only approved methods and guidance to delineate wetlands on your property.

Resources for conducting a wetland delineation Does a wetland delineation expire? Delineation results and reporting Delineations for difficult situations, including during drought years