How Plattow scores natural-catastrophe risk
Plattow's headline score is a property's physical exposure to a damaging natural event, on a 0 to 100 scale. It is driven by the property's FEMA flood zone, then lifted by the worst location-specific peril FEMA rates for that location. It is not FEMA's composite dollar-loss index, which over-weights dense, high-value areas.
The short answer
A property's score is the higher of two inputs: its flood-zone score, and a lift from the most severe location-specific peril FEMA rates at that point. Severe, place-specific perils (wildfire, earthquake, hurricane, tornado, tsunami, volcanic activity, landslide) can reach the top of the scale. Diffuse perils (heat, cold, drought, hail, lightning, high wind, ice storm, winter weather, avalanche) are capped at Elevated, because they rarely make a property uninsurable or unbuildable.
Flood zone is the base
The FEMA flood zone is the dominant, exposure-independent driver. It comes from FEMA's National Flood Hazard Layer and maps directly to a band:
| FEMA flood zone | Band | Meaning |
|---|---|---|
| V, VE | High | Coastal high-velocity Special Flood Hazard Area (wave action). |
| A, AE, AO, AH | Elevated | Special Flood Hazard Area, 1 percent annual chance; mandatory flood insurance on federally backed loans. |
| X (0.2 percent shaded) | Moderate | 500-year floodplain; outside the high-risk zone but not minimal. |
| X (unshaded) | Low | Minimal flood risk; outside the 100 and 500-year floodplains. |
| D | Undetermined | FEMA has not analyzed flood risk here. |
The peril lift
Plattow then reads FEMA's National Risk Index per-peril ratings for the location and lifts the score for genuinely place-specific perils. The rule:
| Peril group | FEMA rating | Effect on score |
|---|---|---|
| Wildfire, earthquake, hurricane, tornado, tsunami, volcanic, landslide | Very High | Lifts to High |
| Same group | Relatively High | Lifts to Elevated |
| Heat, cold, drought, hail, lightning, high wind, ice storm, winter weather, avalanche | Very High | Lifts to Elevated (capped) |
The final score is the maximum of the flood-zone score and the peril lift. This is why a minimal-flood property in genuine wildfire or seismic country still reads elevated or high, while a dense, low-hazard location reads low.
Why Plattow does not use the FEMA composite
FEMA's composite National Risk Index combines expected annual loss, social vulnerability, and community resilience. Expected annual loss is a function of how much population and built value sits in a place, so dense, high-value urban areas score near the top regardless of a single property's physical exposure. For an underwriter or investor asking "how exposed is this specific property to a damaging event," that composite is misleading. Plattow reports the composite only as a labeled regional-context line, and bases the headline on the physical drivers above.
Sources
Flood zone: FEMA National Flood Hazard Layer. Per-peril ratings and the composite: FEMA National Risk Index. Geocoding and geography: U.S. Census Bureau. Elevation: U.S. Geological Survey. Every value Plattow returns names its federal source. See the sources page and the about page, or call the data at /api/report.
Open the Safe Havens map and per-address report. Related: About Plattow.