Port Costa, CA— fire, flood & earthquake hazard information
Port Costa is a unincorporated community in Contra Costa County in the San Francisco Bay Area, covering about 0.2 square miles. This page summarizes what official government maps show for Port Costa: 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 Port Costa’s area that falls inside each mapped zone.
View Port Costa on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, 100% is in a High zone. The remainder of its area is outside currently designated zones.
| High severity zone | 100% |
FEMA flood zones
11% of Port Costa lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO). Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
| Special Flood Hazard Area (100-yr) | 11% |
Earthquake faults & seismic zones
The nearest mapped fault, the Southampton fault, is about 0.3 mi (0.5 km) from the center of Port Costa. 21% of its area is in a state-designated liquefaction zone of required investigation. 36% is in an earthquake-induced landslide zone.
| Nearest mapped fault | Southampton fault — 0.3 mi (0.5 km) |
| Liquefaction zone | 21% |
| Earthquake-induced landslide zone | 36% |
Dam inundation, aircraft noise & air quality
annual average fine-particle (PM2.5) concentration across its census tracts is 8.8 μg/m³, and its composite pollution burden ranks around the 44th percentile statewide.
| Annual PM2.5 (tract average) | 8.8 μg/m³ |
| Pollution burden percentile (statewide) | ~44 |
Frequently asked questions
- Is Port Costa in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, 100% is in a High zone. The remainder of its area is outside currently designated zones.
- Is Port Costa in a FEMA flood zone?
- 11% of Port Costa lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO). Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
- What earthquake faults and seismic zones affect Port Costa?
- The nearest mapped fault, the Southampton fault, is about 0.3 mi (0.5 km) from the center of Port Costa. 21% of its area is in a state-designated liquefaction zone of required investigation. 36% is in an earthquake-induced landslide zone.
- How do I check a specific address in Port Costa?
- Use the free sitelume interactive map at https://sitelume.com — search any Port Costa 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.