Bethel Island, CA— fire, flood & earthquake hazard information
Bethel Island is a unincorporated community in Contra Costa County in the San Francisco Bay Area, covering about 5.3 square miles. This page summarizes what official government maps show for Bethel Island: 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 Bethel Island’s area that falls inside each mapped zone.
View Bethel Island on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
CAL FIRE's current Fire Hazard Severity Zone maps do not designate any zones within Bethel Island. Individual properties near the boundary can still fall inside a neighboring zone — check the exact address on the map.
FEMA flood zones
97% of Bethel Island lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 3% 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) | 97% |
| 0.2% annual chance (500-yr) | 3% |
Earthquake faults & seismic zones
The nearest mapped fault, the Midland fault zone, is about 0.6 mi (1.0 km) from the center of Bethel Island. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 90% of its area is in a state-designated liquefaction zone of required investigation.
| Nearest mapped fault | Midland fault zone — 0.6 mi (1.0 km) |
| Named fault traces crossing boundary | 1 |
| Liquefaction zone | 90% |
Dam inundation, aircraft noise & air quality
11% of Bethel Island lies within a state-reviewed dam-failure inundation area; annual average fine-particle (PM2.5) concentration across its census tracts is 8.6 μg/m³, and its composite pollution burden ranks around the 62th percentile statewide.
| Dam-failure inundation area | 11% |
| Annual PM2.5 (tract average) | 8.6 μg/m³ |
| Pollution burden percentile (statewide) | ~62 |
Frequently asked questions
- Is Bethel Island in a wildfire hazard severity zone?
- CAL FIRE's current Fire Hazard Severity Zone maps do not designate any zones within Bethel Island. Individual properties near the boundary can still fall inside a neighboring zone — check the exact address on the map.
- Is Bethel Island in a FEMA flood zone?
- 97% of Bethel Island lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 3% 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 Bethel Island?
- The nearest mapped fault, the Midland fault zone, is about 0.6 mi (1.0 km) from the center of Bethel Island. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 90% of its area is in a state-designated liquefaction zone of required investigation.
- How do I check a specific address in Bethel Island?
- Use the free sitelume interactive map at https://sitelume.com — search any Bethel Island 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.