Check the LandPowered by GroundtruthCheck a location

Wetlands on land for sale: what the maps can and can't tell you

Wetlands can limit where you build, fill or put a driveway, and work in some wetlands needs a permit. Public wetland maps are a good early warning. They are not the final word.

The National Wetlands Inventory

The US Fish and Wildlife Service's National Wetlands Inventory (NWI) maps wetlands and deepwater habitats, mostly from aerial imagery. Each polygon has a type code, for example freshwater emergent wetland, forested wetland, or a riverine streambed that floods only part of the year.

NWI maps are made for broad planning. Many areas were mapped years ago from imagery. Small or seasonal wetlands can be missing, and boundaries can be off.

Mapped is not the same as regulated

Whether a wet area is regulated under federal law (Section 404 of the Clean Water Act, administered by the US Army Corps of Engineers) or state or local rules depends on an on-site delineation and current law. NWI maps don't decide this. A wetland that isn't on the map can still be regulated, and a mapped one might not be.

Signs to look for on site

  • Standing water or saturated ground well after rain
  • Plants that like wet conditions, such as cattails, sedges or willows
  • Soils mapped as poorly drained, or with frequent ponding
  • Low spots, springs or drainage ditches

Questions to follow up

  • If the screen shows a wetland at or close to where you'd build, hire a wetland consultant for a delineation before you commit.
  • Ask the county planning office about local wetland setbacks.
  • For federal questions, the local US Army Corps of Engineers district handles jurisdiction requests.

What a Groundtruth land screen checks

  • Whether the pin falls in a mapped NWI wetland, the nearest wetland within 500 m, its type, and how many are within 500 m
  • Mapped streams or water areas at the point (USGS NHD), and the nearest named waterbody
  • Soil drainage class and ponding frequency (USDA SSURGO)
  • Protected areas (PAD-US) and USFWS critical habitat at the point

What it can't tell you

  • Whether any wet area on the parcel is legally a regulated wetland
  • Where wetland boundaries fall across the whole parcel
  • Whether a permit is needed for a road, pond or building
Check a locationView a sample report

This guide is general information, not legal, engineering or insurance advice. Rules vary by state and county.