San Lorenzo, CA— fire, flood & earthquake hazard information
San Lorenzo is a unincorporated community in Alameda County in the San Francisco Bay Area, covering about 3.0 square miles. This page summarizes what official government maps show for San Lorenzo: 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 San Lorenzo’s area that falls inside each mapped zone.
View San Lorenzo 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 San Lorenzo. Individual properties near the boundary can still fall inside a neighboring zone — check the exact address on the map.
FEMA flood zones
14% of San Lorenzo lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in a coastal high hazard zone (V/VE); 16% 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) | 14% |
| Coastal high hazard (V/VE) | less than 1% |
| 0.2% annual chance (500-yr) | 16% |
Earthquake faults & seismic zones
The nearest mapped fault, the Hayward fault zone, is about 2.0 mi (3.3 km) from the center of San Lorenzo. 99% of its area is in a state-designated liquefaction zone of required investigation.
| Nearest mapped fault | Hayward fault zone — 2.0 mi (3.3 km) |
| Liquefaction zone | 99% |
Dam inundation, aircraft noise & air quality
less than 1% of San Lorenzo lies within a state-reviewed dam-failure inundation area; 3% is inside an airport noise contour of 65 dB CNEL or louder; annual average fine-particle (PM2.5) concentration across its census tracts is 8.7 μg/m³, and its composite pollution burden ranks around the 34th percentile statewide.
| Dam-failure inundation area | less than 1% |
| Airport noise ≥65 dB CNEL | 3% |
| Annual PM2.5 (tract average) | 8.7 μg/m³ |
| Pollution burden percentile (statewide) | ~34 |
Frequently asked questions
- Is San Lorenzo in a wildfire hazard severity zone?
- CAL FIRE's current Fire Hazard Severity Zone maps do not designate any zones within San Lorenzo. Individual properties near the boundary can still fall inside a neighboring zone — check the exact address on the map.
- Is San Lorenzo in a FEMA flood zone?
- 14% of San Lorenzo lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in a coastal high hazard zone (V/VE); 16% 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 San Lorenzo?
- The nearest mapped fault, the Hayward fault zone, is about 2.0 mi (3.3 km) from the center of San Lorenzo. 99% of its area is in a state-designated liquefaction zone of required investigation.
- How do I check a specific address in San Lorenzo?
- Use the free sitelume interactive map at https://sitelume.com — search any San Lorenzo address to see which mapped zones it falls in, layer by layer.
Nearby in Alameda 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.