Imperial County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
HighComposite Risk Score
National percentile: 96th
Imperial County faces high composite natural disaster risk (NRI Risk Index score 96.5, 96th national percentile), driven primarily by earthquake and riverine flood exposure. Expected annual loss across all 18 hazard types is $148M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Imperial County at high composite risk, with a National Risk Index score of 96.5 out of 100 — placing it in the 96th national percentile and in the upper tier of natural-disaster risk nationally. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by earthquake (ground shaking from sudden movement along geologic faults) at High risk — $101M in expected annual loss and about 0.15 events per year; riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at High risk — $43M in expected annual loss and about 1.54 events per year; and heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Medium risk — $3M in expected annual loss and about 16.90 events per year. Across all hazards, FEMA estimates $148M in expected annual loss for a population of 179K.
Beyond physical exposure, Imperial County has a very high social vulnerability rating (how susceptible the population is to harm) and a very low community resilience rating (its capacity to prepare for and recover from disasters). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
History supports the rating: Imperial County has received 15 federal disaster declarations since 1976, including 4 for flood events and 3 for severe storm events. The most recent was Tropical Storm Hilary (hurricane), declared in November 2023.
Among 58 California counties, Imperial County ranks #25 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | High | 0.15 / yr | $101M |
| Riverine Flood | High | 1.54 / yr | $43M |
| Heat Wave | Medium | 16.90 / yr | $3M |
| Volcanic Activity | Low | 0.00 / yr | $2K |
| Wildfire | Low | 0.00 / yr | $184K |
| Drought | Medium | 39.28 / yr | $321K |
| Strong Wind | Medium | 0.28 / yr | $401K |
| Landslide | Very Low | 6.46 / yr | $459 |
| Hurricane | Very Low | 0.02 / yr | $5K |
| Hail | Very Low | 0.05 / yr | $46K |
| Lightning | Very Low | 11.27 / yr | $35K |
| Tornado | Very Low | 0.10 / yr | $53K |
| Winter Weather | Very Low | 0.00 / yr | $0 |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Imperial County has received 15 federal disaster declarations since 1976, most recently Tropical Storm Hilary in November 2023. Most frequent causes: Flood (4), Severe Storm (3), Hurricane (2).
| Declared | Type | Disaster |
|---|---|---|
| November 2023 | Hurricane | Tropical Storm Hilary |
| April 2023 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| March 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| May 2010 | Earthquake | Earthquake |
| March 2010 | Severe Storm | Severe Winter Storms, Flooding, and Debris and Mud Flows |
| March 2007 | Freezing | Severe Freeze |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| March 1995 | Severe Storm | Severe Winter Storms, Flooding Landslides, Mud Flow |
Showing the 10 most recent of 15 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Imperial County?
Imperial County has a composite FEMA National Risk Index score of 96.5 out of 100, placing it in the High category and the 96th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Imperial County?
The three highest-rated hazards are Earthquake (High, $101M EAL), Riverine Flood (High, $43M EAL), Heat Wave (Medium, $3M EAL). These account for most of the county's expected annual losses.
How does Imperial County compare to other California counties?
Imperial County ranks #25 of 58 California counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has Imperial County had?
FEMA records 15 federal disaster declarations for Imperial County since 1976, most often 4 for flood events and 3 for severe storm events. The most recent was Tropical Storm Hilary, declared in November 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. Imperial County's $148M EAL is a statistical average, not a guarantee for any specific year or address.