What is a Wetland Delineation?
A wetland delineation is a mapped line of the boundary between jurisdictional wetland and nonwetland portions of a site. A jurisdictional wetland is defined under the US Clean Water Act in Section 404. These wetlands are regulated under Federal law , generally with additional State laws and regulations. The delineation process includes:
- Determination and documentation of wetland and nonwetland status for applicable areas of the site
- Flagging the boundary line between wetland and nonwetland areas in the field
- Using GPS (generally submeter or sub-decimeter accuracy) to locate the flag locations and determination points
- Mapping the site by overlaying the field-collected GPS points on a base map and using those points to draw areas for the wetland and nonwetland site components
- Calculating wetland and nonwetland acreages for the site
- Describing the results of the field study in a report, set of maps and field data forms
- Optional but typical: Submittal of the report to the US Army Corps of Engineers (USACE) for verification and a formal finding of jurisdiction under the Clean Water Act, called a ”Jurisdictional Determination’ or JD for short
Step 1: Wetland Determination
First, we have to establish if jurisdictional wetlands are present on the site, parcel or area of land being studied. In order for an area to be classified as a wetland, it must have three characteristics:
- Presence of wetland hydrology
- Presence of hydric soils
- Presence of hydrophytic vegetation (wetland plants)
These factors, or their absence are documented and a determination is made if the area is a wetland or nonwetland (upland). Once wetland and upland determination points have been established, we determine a boundary between them.
Step 2: Field Boundary Flagging
Next, the wetland boundary line is established and marked in the field with flagging tape or other survey markings. This is sometimes referred to as a wetland line or delineation line.
Steps 3, 4 & 5: Mapping
The wetland determination plot locations and wetland flag locations are collected in a differential or RTK GPS system and mapped in a Geographic Information System (GIS) or Computer Aided Drafting (CAD) software application. The wetland area and upland area for the site are calculated.
Step 6: Wetland Delineation Report
A report is compiled describing the results of the wetland determination, the location of the wetland boundary line, and the areas of wetlands and nonwetlands within the study site. Detailed documentation of the determination factors are included, detailing field indicators of hydrology, soil conditions, and wetland vegetation and wetland plant communities.
Step 7: Jurisdictional Determination
The final step is to have the delineation verified by the US Army Corps of Engineers. USACE reviews the report, verifies the methods are compliant with the delineation manual, performs a field check of the wetland flags, and either issues a jurisdictional determination or requests changes be made to the map prior to issuance of the JD.
Other ecological studies and permitting services are often combined with wetland delineations.
Wetland Delineation Experts
Cypress has extensive experience with wetland delineations and jurisdictional determinations in US Army Corps of Engineers Districts throughout the United States. Our staff have performed hundreds of wetland delineations and wetland mapping studies up to 110,000 acres in size and hundreds of miles in length for linear projects, including projects for real estate developers, railways, transportation departments, port authorities, State/ Federal/ municipal governments, individual homeowners, civil engineering firms, construction firms and nonprofit organizations.
Representative Delineation Projects
Texas Flat Mitigation Bank: 1985-acre wetland delineation (also endangered species survey, wetland function assessments, stream assessments, permitting, restoration planning)
Private Client: 200-mile linear delineation for utility corridor Mobile, AL to Jackson, MS (also endangered species survey, stream characterization, environmental assessment, permitting)
Turtleskin Creek Mitigation Bank: 2740-acre wetland delineation (also endangered species survey, wetland function assessments, stream assessments, permitting, restoration planning)