Acalanes Ridge, CA— fire, flood & earthquake hazard information
Acalanes Ridge is a unincorporated community in Contra Costa County in the San Francisco Bay Area, covering about 0.5 square miles. This page summarizes what official government maps show for Acalanes Ridge: 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 Acalanes Ridge’s area that falls inside each mapped zone.
View Acalanes Ridge on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, 2% of Acalanes Ridge is in a Very High fire hazard severity zone. The remainder of its area is outside currently designated zones.
| Very High severity zone | 2% |
FEMA flood zones
FEMA's National Flood Hazard Layer does not map any Special Flood Hazard Areas within Acalanes Ridge. Unmapped does not mean flooding cannot occur — it means no zone is currently designated.
Earthquake faults & seismic zones
The nearest mapped fault, the Franklin fault, is about 0.1 mi (0.1 km) from the center of Acalanes Ridge. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 21% of its area is in a state-designated liquefaction zone of required investigation. 17% is in an earthquake-induced landslide zone.
| Nearest mapped fault | Franklin fault — 0.1 mi (0.1 km) |
| Named fault traces crossing boundary | 1 |
| Liquefaction zone | 21% |
| Earthquake-induced landslide zone | 17% |
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 22th percentile statewide.
| Annual PM2.5 (tract average) | 8.8 μg/m³ |
| Pollution burden percentile (statewide) | ~22 |
Frequently asked questions
- Is Acalanes Ridge in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, 2% of Acalanes Ridge is in a Very High fire hazard severity zone. The remainder of its area is outside currently designated zones.
- Is Acalanes Ridge in a FEMA flood zone?
- FEMA's National Flood Hazard Layer does not map any Special Flood Hazard Areas within Acalanes Ridge. Unmapped does not mean flooding cannot occur — it means no zone is currently designated.
- What earthquake faults and seismic zones affect Acalanes Ridge?
- The nearest mapped fault, the Franklin fault, is about 0.1 mi (0.1 km) from the center of Acalanes Ridge. 1 named fault trace in the USGS Quaternary fault database cross its boundary. 21% of its area is in a state-designated liquefaction zone of required investigation. 17% is in an earthquake-induced landslide zone.
- How do I check a specific address in Acalanes Ridge?
- Use the free sitelume interactive map at https://sitelume.com — search any Acalanes Ridge 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.