National Flood Hazard Layer (NFHL)
Overview
National Flood Hazard Layer (NFHL) is a digital database maintained by FEMA that provides flood hazard information, including flood zones, base flood elevations, and floodplain boundaries. The NFHL is a geospatial compilation of effective Flood Insurance Rate Map (FIRM) data and is the authoritative source for flood hazard determinations.
Key Concepts
Flood zone is a geographic area classified by flood risk level (A, V, X zones). Base flood elevation (BFE) is the computed height of the 1% annual chance flood. Floodway is the channel and adjacent areas that must remain unobstructed for floodwater passage. Coastal barrier resource is protected coastal areas with development restrictions. LOMR (Letter of Map Revision) reflects physical changes to flood hazard boundaries.
Data Layers
| Layer | Description |
|---|---|
| S_FLD_HAZ_AR | Flood hazard zones (primary layer) |
| S_BFE | Base flood elevation lines |
| S_XS | Cross-section lines |
| S_FIRM_PAN | FIRM panel boundaries |
| S_LOMR | Letters of Map Revision |
Access Methods
- FEMA Map Service Center (MSC)
- FEMA National Flood Hazard Layer (NFHL) Viewer
- ArcGIS Online / REST services
- Direct download (GDB, Shapefile)
Appendix
Created: 2025-12-13 | Modified: 2025-12-13