How to check a property for wetlands
Look up the property in the USFWS National Wetlands Inventory (NWI) Wetlands Mapper. NWI polygons show mapped wetlands and deepwater habitat with a code describing the type (PFO1A is a seasonally wet forested wetland, for example). NWI is a screening tool from aerial photo interpretation: it misses many small and forested wetlands and has no regulatory standing. Only a field delineation by a qualified wetland professional establishes where a regulated wetland is.
Step by step
- Open the NWI Wetlands Mapper and search the address.
- Click any polygon on or near the parcel to see its code and the source imagery date.
- Also check SSURGO soils for hydric soils (soil data) and nearby streams. Hydric soil with no NWI polygon is a reason to look closer.
- Check your state or county wetland inventory; some are more detailed than NWI.
Reading an NWI code
PFO1A: Palustrine (inland, non-tidal), FO forested, 1 broad-leaved deciduous, A temporarily flooded.
PEM1C is a seasonally flooded emergent (marsh) wetland. R codes are rivers, L lakes, E estuarine.
Why it matters for a site
- Regulated wetlands come with buffers set by local critical areas codes, often 50 to 200+ ft, which can take a big share of a small lot.
- Jurisdiction can sit with the Army Corps of Engineers, the state and the local government at once.
- Budget for a delineation early on any site with NWI polygons, hydric soils or a stream nearby.
Everything here is planning-level public data. Confirm boundaries, topography, wetlands and flood status with a licensed surveyor and the right specialists before design decisions depend on them.
Basesheet does all of this for any US address in about 30 seconds, free, with no account.
Build a base planRelated
- How to check if a property is in a FEMA flood zone
- How to find soil data for a site
- How to make a site base plan from an address
Updated October 2026.