California coastal flooding risk
Marin County has the highest coastal flooding risk in California, scoring 97.2 out of 100 — rated "Very High" by FEMA's National Risk Index.
| # | County | NRI score | Rating |
|---|---|---|---|
| 1 | Marin County | 97.2 | Very High |
| 2 | Orange County | 92 | Relatively High |
| 3 | San Mateo County | 91.8 | Relatively High |
| 4 | Los Angeles County | 90 | Relatively High |
| 5 | Santa Clara County | 88.8 | Relatively High |
| 6 | Humboldt County | 87.8 | Relatively High |
| 7 | Alameda County | 86 | Relatively High |
| 8 | Solano County | 82.8 | Relatively High |
| 9 | San Diego County | 72.8 | Relatively Moderate |
| 10 | Sonoma County | 68.6 | Relatively Moderate |
| 11 | Napa County | 68.2 | Relatively Moderate |
| 12 | Contra Costa County | 66 | Relatively Moderate |
| 13 | San Francisco County | 62 | Relatively Moderate |
| 14 | Ventura County | 60.8 | Relatively Moderate |
| 15 | Monterey County | 59.8 | Relatively Low |
| 16 | Mendocino County | 54.4 | Relatively Low |
| 17 | Santa Barbara County | 51.4 | Relatively Low |
| 18 | San Luis Obispo County | 50 | Relatively Low |
| 19 | Santa Cruz County | 49.2 | Relatively Low |
| 20 | Del Norte County | 42.4 | Very Low |
| 21 | Sacramento County | 0 | No Rating |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties. See the methodology page for definitions. Download the full CSV for all counties.
Coastal Flooding risk nationally:
Other hazard risks in California:
Frequently asked questions
What is the highest coastal flooding risk county in California?
Marin County, CA has the highest coastal flooding risk in California, with a FEMA National Risk Index score of 97.2 out of 100 (rated "Very High").
How many counties in California are rated Very High for coastal flooding risk?
1 of 21 scored California counties are rated "Very High" for coastal flooding risk by FEMA's National Risk Index.
What causes coastal flooding risk in California?
Coastal flooding scores cover storm surge, wave action, and tidal flooding along the Gulf, Atlantic, and Pacific coasts, and Great Lakes shoreline. Inland flooding is scored separately. Counties with "Not Applicable" ratings have no significant coastal exposure. Coastal flood events are reported at zone level in NOAA Storm Events and are not included in county-level counts.