FEMA rates relative riverine flooding risk for Boulder County as relatively high and reports FEMA annualized frequency of 0.750 per year for the area.
FEMA summary
FEMA's profile for Boulder County reports FEMA annualized frequency of 0.750 per year for riverine flooding. FEMA's relative risk rating for the area is relatively high; the annualized frequency is a separate measure.
Hazard metrics cover FEMA county-equivalent geographies rather than individual addresses or parcels. Use local or state hazard maps before making a property, insurance, retrofit, or evacuation decision.
Select a hazard to inspect FEMA's figures for Boulder County.
Riverine Flooding
FEMA combines its area-wide loss estimate and community data in this relative rating. Event frequency appears separately below.
Relative FEMA score
98.1/100
Occurrence thresholds vary by hazard. The FEMA methodology defines the value for each hazard.
The area loss estimate combines FEMA's modeled losses to buildings, population, and agriculture across Boulder County. It is not an estimate for a home or address.
City risk summary
For Longmont, FEMA rates riverine flooding risk for Boulder County as relatively high, with a relative score of 98.1/100. The next highest relative scores are wildfire at 96.7/100 and landslide at 96.2/100.
Using FEMA data for Boulder County, Longmont is tied #2 among 16 covered Colorado entries for riverine flooding risk; 3 entries share that score. Lafayette is about 12 straight-line miles from the Longmont map point and uses the same FEMA geography.
For homeowners and movers
Preparedness actions
Living in Longmont? Learn how to handle water storage, sanitation, and security in a small space.
The map shows Longmont. All FEMA figures on this page cover Boulder County.
The FEMA figures cover Boulder County. Address-level conditions require local maps, building records, and property details.
FEMA rates relative riverine flooding risk for Boulder County as relatively high. Its FEMA annualized frequency is 0.750 per year. Damage at a specific address also depends on the building, soil, elevation, and exact hazard zone.
Among 16 Colorado cities covered by this directory, Longmont is Tied #2 for relative riverine flooding risk based on FEMA's score for Boulder County. 3 covered cities share this rank because they use the same FEMA geography. Homes within Longmont can have different soil, elevation, construction, and hazard-zone conditions.
In FEMA's data for Boulder County, the highest relative ratings are Riverine Flooding (Relatively High), Wildfire (Relatively Moderate), and Landslide (Relatively High). FEMA uses estimated losses and community data along with event frequency when assigning these ratings.
The hazard numbers cover Boulder County. For an individual home, check local fault, flood, fire, evacuation, and building records for the exact address.
FEMA gives Boulder County an overall relative risk rating of relatively moderate. Conditions at a specific home depend on its hazard zones, building type, maintenance, insurance, and access to evacuation routes and emergency services.
Start with this step: Confirm the exact hazard using official local maps before making property or insurance decisions. Know how local officials issue warnings and evacuation instructions. Use Ready.gov Be Informed and local emergency guidance for a complete plan.
Distances are measured between city coordinates.
| City | Distance | Riverine Flooding rating | Relative score |
|---|---|---|---|
| Lafayette, CO | 12 mi | Relatively High | 98.1 |
| Boulder, CO | 13 mi | Relatively High | 98.1 |
| Thornton, CO | 19 mi | Relatively Low | 55.8 |
| Westminster, CO | 20 mi | Relatively Low | 55.8 |
| Arvada, CO | 23 mi | Relatively Moderate | 94.5 |
Limited to products tagged for riverine flooding or general preparedness.
Disclosure: As an Amazon Associate, this site may earn from qualifying purchases.
Water
Filters up to 100,000 gallons. Essential when tap water is compromised.
View product
GoBag
Keeps critical documents and electronics dry if you have to evacuate through water.
View product
Tools
18 tools in one. Essential for turning off gas valves or making repairs.
View productHazard metrics come from FEMA National Risk Index v1.19.0 (March 2023). City population and coordinates come from SimpleMaps US Cities Database. For current conditions, use official local maps, warnings, inspections, and professional advice.