Byron, CA— fire, flood & earthquake hazard information
Byron is a unincorporated community in Contra Costa County in the San Francisco Bay Area, covering about 6.5 square miles. This page summarizes what official government maps show for Byron: CAL FIRE fire hazard severity zones, FEMA flood zones, state seismic hazard zones, dam inundation areas, airport noise contours, and air-quality indicators. Figures are the share of Byron’s area that falls inside each mapped zone.
View Byron on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, less than 1% is in a Moderate zone. The remainder of its area is outside currently designated zones.
| Moderate severity zone | less than 1% |
FEMA flood zones
28% of Byron lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 20% is in the 0.2% annual chance (500-year) area. Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
| Special Flood Hazard Area (100-yr) | 28% |
| 0.2% annual chance (500-yr) | 20% |
Earthquake faults & seismic zones
The nearest mapped fault, the Midland fault zone, is about 0.2 mi (0.3 km) from the center of Byron. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 95% of its area is in a state-designated liquefaction zone of required investigation.
| Nearest mapped fault | Midland fault zone — 0.2 mi (0.3 km) |
| Named fault traces crossing boundary | 1 |
| Liquefaction zone | 95% |
Dam inundation, aircraft noise & air quality
84% of Byron lies within a state-reviewed dam-failure inundation area; annual average fine-particle (PM2.5) concentration across its census tracts is 8.4 μg/m³, and its composite pollution burden ranks around the 67th percentile statewide.
| Dam-failure inundation area | 84% |
| Annual PM2.5 (tract average) | 8.4 μg/m³ |
| Pollution burden percentile (statewide) | ~67 |
Frequently asked questions
- Is Byron in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, less than 1% is in a Moderate zone. The remainder of its area is outside currently designated zones.
- Is Byron in a FEMA flood zone?
- 28% of Byron lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 20% is in the 0.2% annual chance (500-year) area. Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
- What earthquake faults and seismic zones affect Byron?
- The nearest mapped fault, the Midland fault zone, is about 0.2 mi (0.3 km) from the center of Byron. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 95% of its area is in a state-designated liquefaction zone of required investigation.
- How do I check a specific address in Byron?
- Use the free sitelume interactive map at https://sitelume.com — search any Byron address to see which mapped zones it falls in, layer by layer.
Nearby in Contra Costa County
Sources: CAL FIRE Fire Hazard Severity Zones; FEMA National Flood Hazard Layer; USGS Quaternary Faults; CGS Seismic Hazard Zones & Alquist-Priolo zones; Cal OES dam inundation maps; county ALUC noise contours; CalEnviroScreen 4.0. Area shares are computed against each place’s Census TIGER boundary (last computed 2026-07-24). Boundaries and zone designations change; always verify with the issuing agency.