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Natural hazard risk in Contra Costa County, California

Updated October 30, 2026. Based on FEMA, NOAA and OpenFEMA data. Published by Humblebee.

FEMA overall Risk Index rating: Very High (score 99.4 of 100)[5]

Expected annual loss (FEMA)
$970.5 million[1]
Federal disaster declarations since 1969
19[2]
NFIP flood claims paid, 1978 to 2026
$12.9 million[3]
Tornadoes recorded, 1950 to 2024
5[4]

FEMA's National Risk Index (version 1.20, December 2025) rates overall natural hazard risk for Contra Costa County as Very High, with a score of 99.4 out of 100[5]. The hazards with the highest FEMA scores in this county are earthquake, inland flooding and landslide[6].

FEMA risk ratings for each hazard

Ratings and expected losses from the FEMA National Risk Index. Each rating compares this county with all US counties for that hazard, from Very Low to Very High. They are planning estimates, not predictions, and they do not describe any single property.

FEMA lists $970.5 million in expected annual loss from all 18 natural hazards[1]. This is a FEMA estimate of average yearly loss, not money anyone paid[7]. FEMA's hazard-type Expected Annual Loss values list earthquake at $518.8 million a year, inland flooding at $412.5 million a year and heat wave at $17.8 million a year[8]. FEMA rates social vulnerability Relatively Low, with a score of 21.4[9]. FEMA rates community resilience Relatively High, with a score of 67.8[10]. The index does not predict next year's losses[7].

Hazards sorted by FEMA hazard-type Risk Index score, highest first
HazardFEMA risk ratingExpected annual loss
EarthquakeRelatively High$518.8 million[11]
Inland FloodingVery High$412.5 million[12]
LandslideRelatively High$2.4 million[13]
Heat WaveRelatively High$17.8 million[14]
WildfireRelatively Moderate$10.8 million[15]
DroughtRelatively High$2.8 million[16]
LightningRelatively High$1.5 million[17]
Volcanic ActivityVery Low$343[18]
Coastal FloodingRelatively Moderate$1.0 million[19]
TornadoRelatively Low$1.4 million[20]
TsunamiRelatively Low$1.0 million[21]
Strong WindRelatively Low$398,000[22]
HailVery Low$157,000[23]
Winter WeatherVery Low$8,045[24]
AvalancheVery Low$3[25]

Rated Not Applicable by FEMA for this county: hurricane, ice storm[26].

Social vulnerability and community resilience

FEMA uses these two ratings to scale expected losses into the Risk Index.

FEMA measureRatingScore
Social vulnerabilityRelatively Low21.4[9]
Community resilienceRelatively High67.8[10]

Flooding and flood insurance

FEMA rates inland flooding risk Very High compared with other US counties, with a score of 99.4[12]. FEMA rates coastal flooding Relatively Moderate[19]. OpenFEMA lists 2,681 residential flood insurance contracts in force, a rate of 0.9% of residential structures, as of 2026-08-03[27]. Inside the mapped Special Flood Hazard Area, 28% of homes are insured[27]. OpenFEMA records 1,202 NFIP claims from 1978 to 2026, and NFIP paid $12.9 million in total[3]. To check an address, use FEMA's Flood Map Service Center[28].

Measure Value
Inland Flooding, FEMA risk rating[12] Very High, $412.5 million expected loss a year
Coastal Flooding, FEMA risk rating[19] Relatively Moderate, $1.0 million expected loss a year
NFIP residential flood policies in force (2026)[27] 2,681 of 310,943 homes
Homes in FEMA's mapped high-risk flood area (SFHA)[27] 7,128, of which 1,997 insured
NFIP flood claims, 1978 to 2026[3] 1,202 filed, $12.9 million paid

Is a specific address in a flood zone? Only FEMA's flood maps answer that, property by property[28]. This page describes the whole county.

Search an address on the FEMA Flood Map Service Center

Disaster declarations and tornado records

OpenFEMA lists 19 federal disaster declarations for natural hazards that include Contra Costa County since 1969[2]. By incident type, flood has 8 and severe storm has 6[2]. The most recent are two declarations for severe winter storms, flooding and mudslides in January 2023[29]. NOAA's tornado database records 5 tornadoes in the county from 1950 to 2024, and the strongest were rated EF1[4].

Federal disaster declarations for natural hazards that include Contra Costa County, since 1969
Incident type Declarations
Flood[2] 8
Severe Storm[2] 6
Coastal Storm[2] 2
Drought[2] 1
Hurricane[2] 1
Earthquake[2] 1
Most recent declarations
Declaration Incident Declared
DR-4683-CA[29] Severe Winter Storms, Flooding, Landslides, And Mudslides 2023-01-14
EM-3591-CA[29] Severe Winter Storms, Flooding, And Mudslides 2023-01-09
DR-4308-CA[29] Severe Winter Storms, Flooding, And Mudslides 2017-04-01
DR-4305-CA[29] Severe Winter Storms, Flooding, And Mudslides 2017-03-16
DR-4301-CA[29] Severe Winter Storms, Flooding, And Mudslides 2017-02-14

How to prepare

Steps from Ready.gov, FEMA's preparedness site, for the hazards with the highest FEMA ratings here. Follow instructions from local officials and the National Weather Service when a warning is issued.

Earthquakes

Before

  • Practice Drop, Cover, and Hold On with your family and coworkers.
  • Sign up for earthquake alerts that can warn you before shaking starts.
  • Make a plan with an out-of-state contact and a place to meet if you get separated.
  • Anchor heavy items such as bookcases, refrigerators and water heaters, and keep heavy things on low shelves.
  • Consider earthquake insurance. Standard homeowners policies do not cover earthquake damage.

During

  • Drop to your hands and knees, cover your head and neck, and hold on until the shaking stops.
  • Indoors, stay where you are and avoid doorways. Outdoors, move to an open area away from buildings and power lines.
  • If you are driving, pull over, stop and set the parking brake.

Source: Ready.gov, earthquakes

Floods

Before

  • Check your flood risk with FEMA's Flood Map Service Center, and remember that floods do not follow map lines.
  • Sign up for your community's warning system. NOAA Weather Radio also broadcasts alerts.
  • Buy flood insurance through the NFIP well before a disaster. Homeowners policies do not cover flooding, and a new policy typically takes up to 30 days to go into effect.
  • Make a household plan with evacuation routes, shelter locations and what to do in a flash flood.
  • Keep important documents in a waterproof container and make password-protected digital copies.

During

  • If you are told to evacuate, leave right away and never drive around barricades.
  • Do not walk, swim or drive through floodwater. Six inches of moving water can knock you down.
  • If you are trapped in a building, go to the highest level, but do not climb into a closed attic.

Source: Ready.gov, floods

Extreme heat

Before

  • Learn the signs of heat illness and how to respond.
  • Do not rely on a fan as your main way to stay cool. Fans do not lower body temperature.
  • Find cool public places, such as libraries or malls, or ask your local health department.
  • Keep heat out with window shades, weather stripping and insulation.
  • If you cannot afford cooling costs, contact LIHEAP for help.

During

  • Never leave a person or an animal in a parked car in warm weather.
  • If your home has no air conditioning, go to a cooling center.
  • Wear light, loose clothing, drink plenty of fluids and avoid hard outdoor work in the middle of the day.

Source: Ready.gov, extreme heat

Questions people ask

Is Contra Costa County at risk of flooding?
FEMA rates inland flooding risk Very High compared with other US counties, with a score of 99.4[12]. OpenFEMA lists 8 flood declarations since 1969[2].
Is Contra Costa County at risk of earthquakes?
FEMA rates earthquake risk Relatively High, with a score of 99.7[11]. FEMA lists $518.8 million a year in expected earthquake loss[11].
Does Contra Costa County get tornadoes?
NOAA's tornado database records 5 tornadoes from 1950 to 2024, and the strongest were rated EF1[4]. FEMA rates tornado risk Relatively Low compared with other US counties[20].
How many disasters were declared in Contra Costa County?
OpenFEMA lists 19 federal disaster declarations for natural hazards since 1969[2].
How do I check a flood zone?
Flood zones apply to specific properties. Look up an address at FEMA's Flood Map Service Center or ask the local floodplain manager[28].

Facts and sources

  1. FEMA National Risk Index (version 1.20, December 2025): Expected Annual Loss from all 18 natural hazards in Contra Costa County is $970.5 million a year (Expected Annual Loss rating Relatively High, score 99.6). Of this, buildings account for $801.3 million, injuries and deaths (converted to dollars by FEMA) for... FEMA National Risk Index
  2. OpenFEMA Disaster Declarations Summaries list 19 federal disaster declarations for natural hazards that include Contra Costa County since 1969 (15 major disaster, 4 emergency or fire management). By incident type: flood 8, severe storm 6, coastal storm 2, drought 1, hurricane 1, earthquake 1. Biological (such as... OpenFEMA Disaster Declarations
  3. HazardFacts tally of OpenFEMA NFIP Redacted Claims (losses from 1978 to 2026): 1,202 National Flood Insurance Program claims were filed for losses in Contra Costa County, 669 of them with a payment, and NFIP paid $12.9 million in total (building, contents and increased cost of compliance, in dollars of the year... OpenFEMA NFIP claims
  4. NOAA Storm Prediction Center tornado database (1950 to 2024): 5 recorded tornadoes touched Contra Costa County. The strongest were rated EF1 (most recent of them on 2010-01-23). 0 were rated F3/EF3 or stronger. The most recent recorded tornado was on 2010-01-23. Ratings used the Fujita scale until early 2007 and... NOAA Storm Prediction Center
  5. FEMA National Risk Index (version 1.20, December 2025): the overall natural hazard Risk Index rating for Contra Costa County is Very High, with a Risk Index score of 99.4 out of 100. The score is the county's percentile rank among all US counties. FEMA National Risk Index
  6. Among the 18 hazards in the FEMA National Risk Index (version 1.20, December 2025), the hazards with the highest hazard-type Risk Index scores for Contra Costa County are earthquake (99.7, Relatively High), inland flooding (99.4, Very High), landslide (99.3, Relatively High). HazardFacts sorted FEMA's published... FEMA National Risk Index
  7. FEMA's National Risk Index FAQ (December 2025): Expected Annual Loss is FEMA's estimate of the average economic loss in dollars from natural hazards each year. The index is not meant to predict how much damage a community will have in the next year, and a hazard can still cause damage where a rating is low. Scores... FEMA National Risk Index documentation
  8. HazardFacts sorted FEMA's hazard-type Expected Annual Loss values for Contra Costa County (National Risk Index v1.20): the largest are earthquake ($518.8 million a year), inland flooding ($412.5 million a year), heat wave ($17.8 million a year), out of $970.5 million a year from all 18 hazards. FEMA National Risk Index
  9. FEMA National Risk Index (version 1.20, December 2025): Social Vulnerability rating for Contra Costa County is Relatively Low (score 21.4). FEMA describes social vulnerability as how susceptible social groups are to the harm natural hazards cause. FEMA National Risk Index
  10. FEMA National Risk Index (version 1.20, December 2025): Community Resilience rating for Contra Costa County is Relatively High (score 67.8). FEMA describes community resilience as a community's ability to prepare for, withstand and recover from hazards. FEMA National Risk Index
  11. FEMA National Risk Index (version 1.20, December 2025), earthquake in Contra Costa County: Risk Index rating Relatively High (score 99.7 of 100). Expected Annual Loss $518.8 million a year (rating Very High). FEMA's modeled annual frequency is 0.1273 events per year. FEMA National Risk Index
  12. FEMA National Risk Index (version 1.20, December 2025), inland flooding in Contra Costa County: Risk Index rating Very High (score 99.4 of 100). Expected Annual Loss $412.5 million a year (rating Very High). Annualized frequency 1.18 event-days per year, from recorded occurrences over a period of record of 26 years. FEMA National Risk Index
  13. FEMA National Risk Index (version 1.20, December 2025), landslide in Contra Costa County: Risk Index rating Relatively High (score 99.3 of 100). Expected Annual Loss $2.4 million a year (rating Relatively High). FEMA National Risk Index
  14. FEMA National Risk Index (version 1.20, December 2025), heat wave in Contra Costa County: Risk Index rating Relatively High (score 98.2 of 100). Expected Annual Loss $17.8 million a year (rating Relatively High). Annualized frequency 8.49 event-days per year, from recorded occurrences over a period of record of 18... FEMA National Risk Index
  15. FEMA National Risk Index (version 1.20, December 2025), wildfire in Contra Costa County: Risk Index rating Relatively Moderate (score 97.5 of 100). Expected Annual Loss $10.8 million a year (rating Relatively High). FEMA's modeled annual frequency is 0.0048 events per year. FEMA National Risk Index
  16. FEMA National Risk Index (version 1.20, December 2025), drought in Contra Costa County: Risk Index rating Relatively High (score 94.6 of 100). Expected Annual Loss $2.8 million a year (rating Relatively High). Annualized frequency 55.93 event-days per year, from recorded occurrences over a period of record of 22... FEMA National Risk Index
  17. FEMA National Risk Index (version 1.20, December 2025), lightning in Contra Costa County: Risk Index rating Relatively High (score 90.7 of 100). Expected Annual Loss $1.5 million a year (rating Relatively High). Annualized frequency 4.45 events per year, from recorded occurrences over a period of record of 24 years. FEMA National Risk Index
  18. FEMA National Risk Index (version 1.20, December 2025), volcanic activity in Contra Costa County: Risk Index rating Very Low (score 77.8 of 100). Expected Annual Loss $343 a year (rating Very Low). FEMA National Risk Index
  19. FEMA National Risk Index (version 1.20, December 2025), coastal flooding in Contra Costa County: Risk Index rating Relatively Moderate (score 66.0 of 100). Expected Annual Loss $1.0 million a year (rating Relatively Moderate). FEMA's modeled annual frequency is 1.5326 events per year. FEMA National Risk Index
  20. FEMA National Risk Index (version 1.20, December 2025), tornado in Contra Costa County: Risk Index rating Relatively Low (score 49.8 of 100). Expected Annual Loss $1.4 million a year (rating Relatively Low). Annualized frequency 0.1 events per year, from recorded occurrences over a period of record of 38 years. FEMA National Risk Index
  21. FEMA National Risk Index (version 1.20, December 2025), tsunami in Contra Costa County: Risk Index rating Relatively Low (score 47.6 of 100). Expected Annual Loss $1.0 million a year (rating Relatively Low). FEMA National Risk Index
  22. FEMA National Risk Index (version 1.20, December 2025), strong wind in Contra Costa County: Risk Index rating Relatively Low (score 34.4 of 100). Expected Annual Loss $398,000 a year (rating Relatively Low). Annualized frequency 0.04 events per year, from recorded occurrences over a period of record of 38 years. FEMA National Risk Index
  23. FEMA National Risk Index (version 1.20, December 2025), hail in Contra Costa County: Risk Index rating Very Low (score 33.0 of 100). Expected Annual Loss $157,000 a year (rating Relatively Low). Annualized frequency 0.04 events per year, from recorded occurrences over a period of record of 37 years. FEMA National Risk Index
  24. FEMA National Risk Index (version 1.20, December 2025), winter weather in Contra Costa County: Risk Index rating Very Low (score 9.2 of 100). Expected Annual Loss $8,045 a year (rating Very Low). Annualized frequency 0.44 events per year, from recorded occurrences over a period of record of 18 years. FEMA National Risk Index
  25. FEMA National Risk Index (version 1.20, December 2025), avalanche in Contra Costa County: Risk Index rating Very Low (score 5.2 of 100). Expected Annual Loss $3 a year (rating Very Low). Annualized frequency 0.01 events per year, from recorded occurrences over a period of record of 28 years. FEMA National Risk Index
  26. FEMA National Risk Index (version 1.20, December 2025) rates these hazards Not Applicable for Contra Costa County: hurricane, ice storm. FEMA uses Not Applicable when its source data has no historical record of the hazard in the community and the hazard is not considered geographically possible there. FEMA National Risk Index documentation
  27. NFIP Residential Penetration Rates (OpenFEMA, as of 2026-08-03): 2,681 residential flood insurance contracts were in force in Contra Costa County, out of 310,943 residential structures, a penetration rate of 0.9%. Inside FEMA's mapped Special Flood Hazard Area there were 7,128 residential structures and 1,997... OpenFEMA NFIP penetration rates
  28. FEMA's Flood Map Service Center is the official public source for flood maps (Flood Insurance Rate Maps) produced under the National Flood Insurance Program. Flood zones apply to specific properties: look up an address there or ask the local floodplain manager. County-level ratings do not tell you the flood zone of... FEMA Flood Map Service Center
  29. Most recent federal disaster declarations for natural hazards (table on this page). OpenFEMA Disaster Declarations

FEMA's National Risk Index compares each county with all other US counties. Ratings are relative (Very Low to Very High), not a measure of safety. Never call a place safe, unsafe, good or bad to live in. Risk Index and Expected Annual Loss values are FEMA estimates for planning. They do not predict next year's losses and do not apply to a single property. Flood zones are set by FEMA flood maps for specific properties. County ratings and flood insurance counts do not tell anyone whether an address is in a flood zone. Disaster declaration, NFIP and tornado counts are records of the past for this county only. Do not compare with other counties unless a fact does.

Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties, v1.20 (December 2025). Retrieved from fema.maps.arcgis.com on October 30, 2026. This product uses the Federal Emergency Management Agency's National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s). This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA.