RemoveFloodInsurance.com
The validation study
Before offering a single report, we ran our method across every parcel touching a FEMA flood zone in nine counties of a single major U.S. metropolitan region: 217,236 of them. This page is the summary of what we found, and it is where the numbers on our home page come from. (Counties are anonymized - the study's value is the method and the proportions, which the federal datasets make repeatable anywhere in the country.)
What we did, and what every report does
For each parcel we read the current FEMA flood zone, found the governing Base Flood Elevation where one exists, and measured ground elevations from USGS LiDAR at the building footprint where federal footprint data identified a structure. The delivered reports run the same method with additional per-order machinery, all disclosed in each report's own methodology section:
- Live reads of FEMA's National Flood Hazard Layer: flood zone, FIRM panel and effective date, Letters of Map Change on and near the property, levee records, and Topographic Low Confidence Areas.
- Ground elevations sampled at the building's perimeter where the federal USA Structures dataset identifies the structure (a grid around the geocoded point otherwise - the report states which basis applied), with a one-click correction page if the wrong building was outlined.
- The governing Base Flood Elevation taken from the zone polygon where published; otherwise interpolated along FEMA's stream profile between the two bracketing published BFE lines, with the interpolation and its uncertainty stated on the report - never silently borrowed from a distant line.
- Older flood elevations published in the NGVD29 datum converted to NAVD88 through NOAA's VDatum service, with the conversion and its uncertainty disclosed.
- Refusal gates that stop an automated report rather than ship a wrong one: coastal V zones, regulatory floodways, depth-based AO zones, unmappable datums, coarse-only terrain data, boundary-ambiguous geocodes, and Coastal Barrier Resources System areas get flagged for human review instead.
- Verdict thresholds that must clear the combined error budget - LiDAR vertical accuracy, whole-foot BFE rounding, geocoding position, and the BFE's own interpolation or conversion uncertainty.
What we found
| County | Flood-zone parcels | Mapped outside the SFHA | Cleared the 2-ft bar (guarded) | Borderline (0.5–2 ft) |
|---|---|---|---|---|
| County 1 | 84,380 | 39,324 | 1,147 | 1,567 |
| County 2 | 36,290 | 23,153 | 407 | 508 |
| County 3 | 24,789 | 3,927 | 679 | 635 |
| County 4 | 22,502 | 1,225 | 1,594 | 1,512 |
| County 5 | 18,888 | 603 | 529 | 409 |
| County 6 | 12,589 | 0 | 296 | 248 |
| County 7 | 10,866 | 16 | 309 | 411 |
| County 8 | 5,743 | 35 | 206 | 226 |
| County 9 | 1,189 | 0 | 23 | 34 |
| Total | 217,236 | 68,283 | 5,190 | 5,550 |
Filter definition (the same for every number we publish): "Mapped outside the SFHA" counts parcels touching or adjoining a flood zone that the current map places outside the high-risk area behind an accredited or provisionally accredited levee - levee-based mapping is exactly the kind of determination that can lag or change, which is why these owners benefit from a records check. "Cleared the 2-ft bar (guarded)" counts in-zone parcels whose lowest sampled ground measured at least 2 ft above the governing Base Flood Elevation after excluding coastal V zones, regulatory floodways, margins above 8 ft (implausible values that usually indicate a data problem), and any Base Flood Elevation borrowed from a BFE line farther than 300 ft away - the same exclusions our reports apply. Across all nine counties that is 5,190 of 148,953 in-zone parcels, about 1 in 29. The home-page statistic comes from this table. One methodological note: the study screened parcels on a sampling grid; the reports we deliver sample at the building's own perimeter where federal footprint data identifies the structure, so an individual property's result can differ from its study bucket.
What it means for you
Two groups of owners are paying more than the map requires: owners already mapped out whose lenders never re-checked, and owners inside the zone whose ground clears the flood elevation. The free lookup on our home page tells you which situation your address is in, from live FEMA records.