Flood Risk (v1)
Version 1.0.0 · Published 2026-06-19
What this is
Flood Risk joins the Environmental Feature Inventory as a category alongside TRI, contaminated sites, RCRA hazardous waste, major roadways, traffic noise, golf courses, phosphate, CAFOs, ag fields, and water quality. In Florida, flood is the single largest environmental financial risk: a home can be environmentally pristine and still sit in a zone that requires several thousand dollars a year of flood insurance. Like water quality, flood is a property-level category, it describes the zone your parcel sits in, not a nearby point.
Data source
We query the FEMA National Flood Hazard Layer (NFHL), the federal system of record for flood zones, as a point lookup against FEMA's public mapping service (the "Flood Hazard Zones" layer). For your address we read the flood zone designation (for example AE, VE, or X), whether it falls in a Special Flood Hazard Area, and the static Base Flood Elevation when one is published.
Tier-firing rules
| Tier | FEMA zone | What it means |
|---|---|---|
| SEVERE | V, VE, VO | Coastal high-hazard zone subject to wave action (VO is the sheet-flow / velocity variant). The most dangerous and most expensive to insure. |
| MODERATE | A, AE, AO, AH, AR, A99 (or any Special Flood Hazard Area) | The 1%-annual-chance floodplain (the "100-year" flood). Flood insurance is federally required for a mortgage here. |
| MINOR | X (shaded) | The 0.2%-annual-chance ("500-year") floodplain. Insurance is not required but flooding is still possible. |
| none | X (unshaded), D, or unmapped | Minimal mapped flood hazard, an undetermined-risk area, or outside FEMA's mapped coverage. |
How it affects the grade
The flood tier feeds the Environmental Grade through the same worst-feature-wins rule as every other category: a severe (V/VE/VO) zone sets a base grade of D, and a moderate (A/AE) zone contributes like any other moderate hazard. Because flood is a property-level zone rather than a nearby point, it is excluded from the "dominant feature on the parcel" proximity cap (that rule is for physical point sources next door), so an AE zone informs the grade without single-handedly forcing it to D.
What v1 does not yet include
- Storm surge (NOAA SLOSH inundation by hurricane category) is a separate forthcoming category.
- Historical claims (OpenFEMA NFIP claim history for the area) is a forthcoming signal.
- A flood-insurance dollar estimate in the Ongoing Costs subscore is planned alongside the broader insurance estimate work.
Source: FEMA National Flood Hazard Layer (NFHL), hazards.fema.gov. Flood zones are revised by FEMA over time; always confirm the current effective map for an address before relying on it.