Every WindMayor city scored against the FEMA National Flood Hazard Layer — the federal map of Special Flood Hazard Areas (SFHA), the 1%-annual-chance floodplain where NFIP flood insurance is mandatory on federally-backed mortgages. Properties in those zones carry an annual premium that quietly eats into NOI. This overlay turns that exposure into a flood-adjusted DSCR so a high headline yield doesn't hide an uninsurable basement.
| # | City | St | Flood risk ↓ | Band | DSCR | Flood-adj DSCR* | Ins. load* |
|---|
* Flood-adjusted DSCR and insurance load are ILLUSTRATIVE — based on an assumed NFIP premium, not a quote. See methodology below.
The FEMA National Flood Hazard Layer (NFHL) is the
authoritative federal flood map and a U.S. Government work in
the public domain. We query its public ArcGIS REST service,
MapServer/28 — "Flood Hazard Zones"
(S_FLD_HAZ_AR polygons) — using the field
SFHA_TF. SFHA_TF = 'T' means a location sits
inside a Special Flood Hazard Area: FEMA zones
A, AE, AH, AO, AR, A99, V, VE — the 1%-annual-chance
("100-year") floodplain where the National Flood Insurance Program
mandates flood insurance for federally-backed loans.
3×3 grid of sample
points over a ±4 km box centred on the
city centroid (9 points, ~2–3 km spacing).flood_risk_score = fraction of sample points that
land in an SFHA, from 0.0 (minimal) to
1.0 (very high).resolution_tag: city_grid_sample) — a coarse
estimate at ~grid-spacing resolution. A score of 0.0 means no sample
point hit an SFHA; it does not guarantee zero flood risk
anywhere in the metro. For a real underwrite, pull the parcel's exact
flood zone from FEMA's Flood Map Service Center.
premium × flood_risk_score), from the NOI proxy,
then recompute DSCR. The $1,200 figure is an assumption, not a
quote. Real Risk Rating 2.0 premiums vary widely by
elevation, structure and prior claims. Do not use the
flood-adjusted DSCR for underwriting decisions.
Cities with no centroid or a failed query are recorded as
null — never fabricated.
hazards.fema.gov/arcgis/rest/services/public/NFHL ·
public domain · DSCR base from WindMayor cities dataset
(Zillow ZHVI/ZORI, research use) · R-OSM.flood-overlay