FEMA Flood Zones
Zone X
The moderate- and low-risk zone outside the Special Flood Hazard Area — shaded X (0.2% annual chance) and unshaded X (minimal hazard).
fldzone = 'X'
Risk tier: Moderate to low — outside the Special Flood Hazard Area (SFHA).
Zone X covers everything outside the high-risk 1%-annual-chance floodplain. It is by far the most common value in the dataset. Critically, X bundles two very different risk pictures that FEMA distinguishes on the map by shading — a distinction the dataset preserves in zonesubty.
Shaded vs. unshaded X
| Shaded X | Unshaded X | |
|---|---|---|
| Risk | Moderate | Low / minimal |
| What it covers | The 0.2%-annual-chance (500-year) floodplain; 1%-annual-chance areas with average depths under 1 foot or drainage areas under 1 sq mi; and areas protected by a levee from the base flood | Areas of minimal flood hazard, above the 0.2%-annual-chance flood level |
| Legacy equivalent | Zone B | Zone C |
Because both are stored as fldzone = 'X', use zonesubty to tell them apart.
zonesubty values
zonesubty | Interpretation |
|---|---|
0.2 PCT ANNUAL CHANCE FLOOD HAZARD | Shaded X — the 500-year floodplain. |
1 PCT DEPTH LESS THAN 1 FOOT | Shaded X — nominal 1%-annual-chance flooding of very shallow depth. |
AREA WITH REDUCED FLOOD RISK DUE TO LEVEE | Shaded X — protected by a levee (residual risk remains if the levee is overtopped or fails). |
AREA OF MINIMAL FLOOD HAZARD | Unshaded X — minimal hazard. |
| (empty) | Unshaded X — minimal hazard. |
Building and insurance implications
- Outside the SFHA, so flood insurance is not federally required — but it is available at lower Preferred Risk rates, and it is worth noting that a substantial share of NFIP claims come from outside the SFHA, particularly in shaded X.
- No SFHA elevation requirements apply, though local ordinances may still address drainage.
In the data
| Column | Value |
|---|---|
fldzone | X |
staticbfe | NULL |
zonesubty | shaded/unshaded qualifier (see table above) |
firmid / firmdate | source FIRM panel and effective date |
-- Split X parcels into shaded (moderate) vs. unshaded (minimal)
SELECT lrid, parceladdr,
CASE
WHEN zonesubty IN ('AREA OF MINIMAL FLOOD HAZARD', '') OR zonesubty IS NULL
THEN 'unshaded X (minimal)'
ELSE 'shaded X (moderate)'
END AS x_class
FROM lr_parcel_us
WHERE fldzone = 'X';See also: Zones B and C (the legacy equivalents), Zone D (undetermined risk).