Alameda County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
Very HighComposite Risk Score
National percentile: 100th
Alameda County faces very high composite natural disaster risk (NRI Risk Index score 99.8, 100th national percentile), driven primarily by earthquake and landslide exposure. Expected annual loss across all 18 hazard types is $1.88B.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Alameda County at very high composite risk, with a National Risk Index score of 99.8 out of 100 — placing it in the 100th national percentile and among the most at-risk counties in the United States. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Alameda County's expected losses come from earthquake (ground shaking from sudden movement along geologic faults) at Very High risk — $1.35B in expected annual loss and about 0.14 events per year; landslide (downhill movement of rock, soil, and debris on unstable slopes) at High risk — $6M in expected annual loss and about 24.63 events per year; and riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Very High risk — $491M in expected annual loss and about 2.25 events per year. Across all hazards, FEMA estimates $1.88B in expected annual loss for a population of 1.68M.
Beyond physical exposure, Alameda County has a low social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The county's disaster history tells the same story: Alameda County has received 24 federal disaster declarations since 1970, including 8 for severe storm events and 7 for flood events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides (severe storm), declared in April 2023.
Among 58 California counties, Alameda County ranks #3 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | Very High | 0.14 / yr | $1.35B |
| Landslide | High | 24.63 / yr | $6M |
| Riverine Flood | Very High | 2.25 / yr | $491M |
| Wildfire | High | 0.01 / yr | $12M |
| Heat Wave | High | 7.10 / yr | $13M |
| Coastal Flood | High | 0.98 / yr | $5M |
| Drought | Medium | 58.43 / yr | $1M |
| Volcanic Activity | Very Low | 0.00 / yr | $348 |
| Tornado | Medium | 0.09 / yr | $2M |
| Tsunami | Low | 0.34 / yr | $3M |
| Lightning | Low | 4.50 / yr | $235K |
| Hail | Low | 0.04 / yr | $167K |
| Strong Wind | Very Low | 0.04 / yr | $94K |
| Avalanche | Very Low | 0.01 / yr | $4 |
| Winter Weather | Very Low | 0.69 / yr | $3K |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
Disaster History
Alameda County has received 24 federal disaster declarations since 1970, most recently Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides in April 2023. Most frequent causes: Severe Storm (8), Flood (7), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2023 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| January 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| January 2023 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| April 2017 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| March 2017 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| February 2017 | Severe Storm | Severe Winter Storms, Flooding, and Mudslides |
| June 2006 | Severe Storm | Severe Storms, Flooding, Landslides, and Mudslides |
| February 2006 | Severe Storm | Severe Storms, Flooding, Mudslides, and Landslides |
Showing the 10 most recent of 24 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Alameda County?
Alameda County has a composite FEMA National Risk Index score of 99.8 out of 100, placing it in the Very High category and the 100th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Alameda County?
The three highest-rated hazards are Earthquake (Very High, $1.35B EAL), Landslide (High, $6M EAL), Riverine Flood (Very High, $491M EAL). These account for most of the county's expected annual losses.
How does Alameda County compare to other California counties?
Alameda County ranks #3 of 58 California counties for overall natural disaster risk, with a very high rating.
How many federally declared disasters has Alameda County had?
FEMA records 24 federal disaster declarations for Alameda County since 1970, most often 8 for severe storm events and 7 for flood events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared in April 2023.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Alameda County's $1.88B EAL is a statistical average, not a guarantee for any specific year or address.