How do I check whether a parcel has wetlands on it?
Screen the parcel against the National Wetlands Inventory to see whether wetlands have been mapped there. That screen tells you where to look and what to expect. It does not tell you whether a regulator considers any of it jurisdictional — only a delineation in the field, confirmed by the US Army Corps of Engineers, does that.
The mistake almost everyone makes
Reading "no mapped wetland" as "no wetland". The inventory was interpreted from aerial imagery, some of it decades old, and it is assembled as a mosaic of project areas mapped at different times to different standards. Small, forested and seasonal wetlands are exactly the ones that photointerpretation misses. An unmapped parcel is an unstudied parcel, not a cleared one — and the inventory's own documentation says it is not intended for jurisdictional determinations.
How to check it
Screen the parcel boundary against the inventory
Look for mapped wetland polygons intersecting the parcel, and read the classification codes rather than just the presence: an estuarine emergent wetland and a farmed seasonally-flooded depression are treated very differently downstream. The codes are Cowardin classifications — a system, not a list — and the Service publishes the key that decodes them.
Look at hydric soils and the ground itself
Wetland determination rests on three indicators together — hydrology, hydrophytic vegetation and hydric soils. Soil survey data will often flag a wet area the imagery missed, and vice versa. Where the two disagree, that disagreement is the finding.
Get a delineation before you rely on it
A wetland delineation is field work by a qualified consultant, following the Corps manual and the applicable regional supplement. It produces a boundary; the Corps then issues an approved jurisdictional determination saying whether that boundary is regulated. Those are two separate steps and the second is the one that binds.
Expect the regulatory line to have moved
Which waters are federally regulated has changed materially since the Supreme Court's 2023 decision in Sackett v. EPA, and states regulate wetlands independently of the federal definition — several more strictly. A wetland can be outside federal jurisdiction and still be fully protected by state or local rule.
What this still does not tell you
- It is not a jurisdictional determination, and no dataset can be one. Section 404 jurisdiction is decided by the Corps on a delineated boundary.
- It does not establish a buffer or setback: those come from state and local ordinance, which the inventory says nothing about.
- Absence of a mapped wetland is not evidence of absence — the inventory is a screening product assembled from imagery of varying age.
- It is not a substitute for a delineation, and it is not legal advice.