Contra Costa County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
Very HighComposite Risk Score
National percentile: 99th
Contra Costa County faces very high composite natural disaster risk (NRI Risk Index score 99.5, 99th national percentile), driven primarily by earthquake and riverine flood exposure. Expected annual loss across all 18 hazard types is $971M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Contra Costa County at very high composite risk, with a National Risk Index score of 99.5 out of 100 — placing it in the 99th 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 Contra Costa County's expected losses come from earthquake (ground shaking from sudden movement along geologic faults) at High risk — $519M in expected annual loss and about 0.13 events per year; riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Very High risk — $412M in expected annual loss and about 1.18 events per year; and landslide (downhill movement of rock, soil, and debris on unstable slopes) at High risk — $2M in expected annual loss and about 19.83 events per year. Across all hazards, FEMA estimates $971M in expected annual loss for a population of 1.17M.
Beyond physical exposure, Contra Costa County has a low social vulnerability rating (how susceptible the population is to harm) and a 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 federal record bears this out: Contra Costa County has received 21 federal disaster declarations since 1969, including 8 for flood events and 6 for severe storm events. The most recent was Severe Winter Storms, Flooding, Landslides, and Mudslides (flood), declared in January 2023.
Among 58 California counties, Contra Costa County ranks #8 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | High | 0.13 / yr | $519M |
| Riverine Flood | Very High | 1.18 / yr | $412M |
| Landslide | High | 19.83 / yr | $2M |
| Heat Wave | High | 8.49 / yr | $18M |
| Wildfire | Medium | 0.00 / yr | $11M |
| Drought | High | 55.93 / yr | $3M |
| Lightning | High | 4.45 / yr | $1M |
| Volcanic Activity | Very Low | 0.00 / yr | $343 |
| Coastal Flood | Medium | 1.53 / yr | $1M |
| Tornado | Low | 0.10 / yr | $1M |
| Tsunami | Low | 0.34 / yr | $1M |
| Strong Wind | Low | 0.04 / yr | $398K |
| Hail | Very Low | 0.04 / yr | $157K |
| Winter Weather | Very Low | 0.44 / yr | $8K |
| Avalanche | Very Low | 0.01 / yr | $3 |
| 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
Contra Costa County has received 21 federal disaster declarations since 1969, most recently Severe Winter Storms, Flooding, Landslides, and Mudslides in January 2023. Most frequent causes: Flood (8), Severe Storm (6), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| 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 |
| February 2006 | Severe Storm | Severe Storms, Flooding, Mudslides, and Landslides |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| February 1998 | Severe Storm | Severe Winter Storms and Flooding |
Showing the 10 most recent of 21 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Contra Costa County?
Contra Costa County has a composite FEMA National Risk Index score of 99.5 out of 100, placing it in the Very High category and the 99th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Contra Costa County?
The three highest-rated hazards are Earthquake (High, $519M EAL), Riverine Flood (Very High, $412M EAL), Landslide (High, $2M EAL). These account for most of the county's expected annual losses.
How does Contra Costa County compare to other California counties?
Contra Costa County ranks #8 of 58 California counties for overall natural disaster risk, with a very high rating.
How many federally declared disasters has Contra Costa County had?
FEMA records 21 federal disaster declarations for Contra Costa County since 1969, most often 8 for flood events and 6 for severe storm events. The most recent was Severe Winter Storms, Flooding, Landslides, and Mudslides, declared in January 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. Contra Costa County's $971M EAL is a statistical average, not a guarantee for any specific year or address.