Riverine Flood Risk in California
All California counties ranked by FEMA National Risk Index riverine flood score
Riverine Flood risk — rivers and streams overflowing their banks after heavy rain or snowmelt — is rated for 58 of 58 California counties in FEMA's National Risk Index. Los Angeles County carries the state's highest riverine flood score at 100.0, with $2.81B in expected annual riverine flood losses.
33 California counties are rated High or Very High for riverine flood, and expected annual losses from riverine flood total roughly $11.66B statewide. The full ranking below links to each county's complete 18-hazard risk profile.
County Rankings — Riverine Flood
| # | County | Riverine Flood Score | Rating | Ann. Freq. | Ann. Loss |
|---|---|---|---|---|---|
| 1 | Los Angeles County | Very High | 3.96 / yr | $2.81B | |
| 2 | Riverside County | Very High | 7.36 / yr | $1.13B | |
| 3 | Orange County | Very High | 2.89 / yr | $820M | |
| 4 | San Bernardino County | Very High | 12.96 / yr | $960M | |
| 5 | Santa Clara County | Very High | 2.07 / yr | $720M | |
| 6 | Alameda County | Very High | 2.25 / yr | $491M | |
| 7 | San Diego County | Very High | 7.89 / yr | $648M | |
| 8 | Contra Costa County | Very High | 1.18 / yr | $412M | |
| 9 | Ventura County | Very High | 1.93 / yr | $313M | |
| 10 | Sonoma County | High | 2.54 / yr | $280M | |
| 11 | Sacramento County | High | 1.93 / yr | $216M | |
| 12 | Fresno County | High | 4.11 / yr | $166M | |
| 13 | San Francisco County | High | 1.61 / yr | $178M | |
| 14 | Santa Barbara County | High | 1.54 / yr | $167M | |
| 15 | Kern County | High | 5.64 / yr | $147M | |
| 16 | San Mateo County | High | 1.39 / yr | $212M | |
| 17 | Tulare County | High | 3.04 / yr | $130M | |
| 18 | San Joaquin County | High | 1.11 / yr | $138M | |
| 19 | Solano County | High | 0.79 / yr | $141M | |
| 20 | Monterey County | High | 1.82 / yr | $109M | |
| 21 | San Luis Obispo County | High | 0.64 / yr | $110M | |
| 22 | Marin County | High | 2.11 / yr | $116M | |
| 23 | Santa Cruz County | High | 1.61 / yr | $105M | |
| 24 | Stanislaus County | High | 0.57 / yr | $94M | |
| 25 | Napa County | High | 1.11 / yr | $90M | |
| 26 | Placer County | High | 1.11 / yr | $107M | |
| 27 | Mendocino County | High | 0.75 / yr | $56M | |
| 28 | Shasta County | High | 1.00 / yr | $72M | |
| 29 | Merced County | High | 1.86 / yr | $59M | |
| 30 | Humboldt County | High | 0.86 / yr | $51M | |
| 31 | Imperial County | High | 1.54 / yr | $43M | |
| 32 | Lake County | High | 0.50 / yr | $51M | |
| 33 | Madera County | High | 1.43 / yr | $45M | |
| 34 | Butte County | Medium | 1.36 / yr | $48M | |
| 35 | El Dorado County | Medium | 1.14 / yr | $56M | |
| 36 | Siskiyou County | Medium | 1.00 / yr | $31M | |
| 37 | Tehama County | Medium | 0.75 / yr | $35M | |
| 38 | Nevada County | Medium | 0.86 / yr | $37M | |
| 39 | Yolo County | Medium | 0.93 / yr | $42M | |
| 40 | Plumas County | Medium | 0.46 / yr | $22M | |
| 41 | Kings County | Medium | 1.18 / yr | $25M | |
| 42 | Yuba County | Medium | 0.57 / yr | $25M | |
| 43 | Tuolumne County | Medium | 0.96 / yr | $19M | |
| 44 | Trinity County | Medium | 0.21 / yr | $13M | |
| 45 | Del Norte County | Medium | 0.32 / yr | $16M | |
| 46 | Calaveras County | Medium | 0.71 / yr | $15M | |
| 47 | Lassen County | Medium | 0.29 / yr | $13M | |
| 48 | Sutter County | Low | 0.61 / yr | $12M | |
| 49 | Mariposa County | Low | 2.07 / yr | $8M | |
| 50 | Amador County | Low | 0.75 / yr | $12M | |
| 51 | San Benito County | Low | 0.29 / yr | $18M | |
| 52 | Inyo County | Low | 4.96 / yr | $7M | |
| 53 | Mono County | Low | 0.68 / yr | $7M | |
| 54 | Modoc County | Low | 0.46 / yr | $5M | |
| 55 | Glenn County | Low | 0.71 / yr | $7M | |
| 56 | Colusa County | Low | 0.54 / yr | $4M | |
| 57 | Sierra County | Low | 0.14 / yr | $4M | |
| 58 | Alpine County | Very Low | 0.11 / yr | $1M |
58 California counties with measurable riverine flood risk. See the national riverine flood ranking or all California counties by overall risk.
Frequently Asked Questions
Which California county has the highest riverine flood risk?
Los Angeles County has the highest FEMA riverine flood risk score in California at 100.0 (Very High), with $2.81B in expected annual losses and about 3.96 events per year.
How many California counties face significant riverine flood risk?
58 California counties record measurable riverine flood risk in FEMA's National Risk Index; 33 of them are rated High or Very High.