Wetland Delineation

A scientific investigation that identifies and maps the boundaries of wetlands on a property using specific criteria for hydrology, hydric soils, and hydrophytic vegetation, as required by the Clean Water Act.

What is a Wetland Delineation?

A wetland delineation is a field investigation conducted by qualified scientists to identify and map the boundaries of wetlands and other waters on a property. Wetlands are legally defined by the presence of three criteria: hydric soils (soils that develop under saturated conditions), hydrophytic vegetation (plants adapted to wet conditions), and wetland hydrology (evidence of periodic inundation or saturation). All three criteria must be present for an area to be classified as a wetland.

Why Wetland Delineation Matters

Wetlands are protected under the federal Clean Water Act (Section 404), and development that would fill, dredge, or otherwise impact wetlands requires a permit from the U.S. Army Corps of Engineers. Many states have additional wetland protection laws. Identifying wetlands early in the development planning process is critical because wetland impacts can trigger extensive permitting requirements, costly mitigation obligations, and significant project delays.

The Delineation Process

A qualified wetland scientist conducts field surveys to identify areas meeting the three-criteria test, maps the wetland boundaries using GPS, and prepares a delineation report. The report is submitted to the Army Corps of Engineers for verification. The Corps may conduct its own field inspection before issuing a jurisdictional determination confirming the wetland boundaries.

Wetlands and Development

For developers, wetlands on a site can significantly constrain the developable area and trigger federal permitting requirements (Section 404 permits) that add months or years to the entitlement process. Wetland mitigation — creating or restoring wetlands to compensate for impacts — is typically required and can be costly. Purchasing wetland mitigation bank credits is an alternative to on-site mitigation.