Floodplain maps help property owners determine how much their property is at risk for flooding and if the property is within a regulatory floodplain. Regulatory floodplain maps (also known as effective Flood Insurance Rate Maps - FIRMs) are used by lenders and the insurance industry to determine flood insurance requirements.

Longmont has been part of the National Flood Insurance Program (NFIP) since 1971, and the city actively participates in floodplain management.

The goals of the NFIP are to reduce flood hazards by:

• Regulating floodplain activities
• Adopting floodplain policies
• Mapping floodplains
• Educating the public about floods and floodplains

Check Your Property's Floodplain Status

 

 

Find out if your property (within the City of Longmont limits) is in the floodplain with our Floodplain Inquiry Map. To use the map, enter your address into the property search box. After you click "OK" for the terms and conditions, wait a couple of minutes for the map to load. Compare your results to the legend. Please be patient; the map takes some time to open. To see each layer best, turn off any other open layers by clicking on the checkmark.

The Floodplain Inquiry Map contains the most up-to-date FEMA map information available and shows what regulatory floodplain zone your property is in. It is the map the Federal Emergency Management Agency (FEMA) and your mortgage lender will use to determine if you are required to carry flood insurance on your property.

If the map shows that any BLUE area--known as “A Zone" (AE, AO, AH, A)--is touching the building and you are applying for any type of federally backed loan, then flood insurance will likely be required. Be sure this information is verified using elevation details such as are provided on an Elevation Certificate.

If the map shows that any BLUE Area / “A Zone” (AE, AO, AH, A) is on your property (but not touching the building), flood insurance is not likely to be required, but lenders can still request it as part of the loan negotiations.

Be aware that anyone can purchase flood insurance, even if their property is not located within the blue area. Learn more about flood insurance.

Elevation Certificates

An Elevation Certificate is a document that provides information about a building's elevation compared to the estimated height of floodwaters during a major flood in the area. An Elevation certificate is no longer required to get a quote for flood insurance, but one is still useful to get the best premium.

Longmont's Planning and Development Services department maintains files with Elevation Certificates for buildings throughout the city. Contact the Floodplain Administrator to see if a certificate is on file for your property.

If no Elevation Certificate exists for your building, you'll need to work with a Professional Land Surveyor to have one prepared. We've compiled this list of active, licensed surveyors sorted alphabetically by town name that may be able to assist you. Additional information may be found through the Colorado Department of Regulatory Agencies' License Verification webpage.

Updated Floodplain Information

Floodplain maps are updated as changes occur to properties. These changes can occur from more accurate topography, updated flow rates (hydrology), public works projects (such as Resilient St. Vrain), and other changes. Updated floodplain information shown in the maps below will be used by the City of Longmont to help with new development decisions but the information cannot be used for flood insurance requirements until the maps have been approved by FEMA.

St. Vrain Creek

The floodplain maps for the St. Vrain Creek through Longmont are in the process of changing, based on updated hydrology information adopted after the 2013 flooding.

The draft 100-year floodplain information for St. Vrain Creek is shown in blue on the Floodplain Inquiry Map. This is the map layer that is shown automatically when the "Floodplain Inquiry" map is opened. Under the "List of Layers" it is titled "Preliminary FIRM Package" within the RSVP LOMR 1/Preliminary FIRMs/Additional Floodplain Layers. Use the + and - buttons to zoom in and out.

• This map is based on the increased flows adopted by Longmont, the State of Colorado and FEMA after the 2013 flood.
• This map has been sent in draft form to FEMA for review. Once final, it will become the new FEMA effective floodplain, most likely in summer of 2023.
• This map was adopted as Best Available Data by the City Council in December 2019

The "Draft 500-Year Floodplain for St. Vrain Creek" is also available for viewing. It is shown in orange on the map.

Left Hand Creek

There is also a new floodplain map available to view for Left Hand Creek. The draft floodplain information for this map is shown in blue on the Floodplain Inquiry Map. This layer is also shown automatically when the map is opened. In the "List of Layers" it is the layer titled "Preliminary FIRM Package." Use the + and - buttons to zoom in and out.

• This map represents new CHAMP floodplain mapping for Left Hand Creek using the increased flows adopted by Longmont, the State and FEMA after the 2013 flood.
• This map has been submitted to FEMA for review and was adopted by the City of Longmont as Best Available Information in December of 2019.

Lykins Gulch and Spring Gulch #1

Floodplain boundaries for Lykins Gulch and Spring Gulch #1 are also available to view on the Floodplain Inquiry Map. These boundaries have been mapped by the City but are not FEMA regulatory maps. These boundaries automatically appear when the Floodplain Inquiry Map is opened. These layers are named "City Mapped 1% Chance (100-Year) Floodplains." To turn them off, uncheck the box under the "List of Layers" under the address search box. Use the + and - buttons to zoom in and out.

Longmont 2013 Flood Map

An outline of the flooded areas of Longmont during the 2013 flood may also be viewed on the Floodplain Inquiry Map. To view this map layer (shown in yellow), go to the "List of Layers" icon underneath the "Search by Address" box and check the layer titled "RSVP LOMR 1/Preliminary FIRM/Additional Floodplain layers and check the box titled "2013 flood Extents - Weld County" or "2013 Flood Extents - Boulder County." Use the + and - buttons to zoom in and out.

Other Creeks

In addition to St. Vrain and Left Hand Creeks, Dry Creek No. 1 and Spring Gulch No. 1 are also FEMA mapped floodplains. However, they did not change on the Preliminary FIRMs because they were not affected by the 2013 flood.

Effective FIRMs

The December 2012 FIRM Maps are still the effective FIRMs, meaning that flood insurance requirements are still decided using these maps until the Preliminary FIRMs are effective. They are shown on the Floodplain Inquiry Map under the List of Layers as "Effective FIRMs, December 19, 2012."

Outside Longmont City Limits?

These resources may be useful to property owners outside the Longmont city limits. Please direct any questions about these maps to the county contacts listed on the linked pages.

Boulder County

Boulder County adopted Draft Phase 2 Champ floodplain maps and model for Left Hand Creek (and other creeks in Boulder County) as Best Available Information in July 2018.

• Visit the Boulder County Floodplain Management webpage

• View Boulder County floodplain maps

Weld County

Weld County also maintains its preliminary FIRMs maps online for review.

• Visit the Weld County Floodplain Management webpage

• View Weld County floodplain maps

For Weld County floodplain questions, contact:

• Colorado Water Conservation Board: Terri Fead, 303-866-3441 x3230 or terri.fead@state.co.us
• Weld County: Diana Aungst, 970-400-3524 or daungst@weldgov.com

Need More Information?

Assistance with floodplain information is available from Longmont's Floodplain Administrator. Floodplain information requests are responded to within 24 hours during business hours or 48 hours if outside business hours and an appointment to discuss in person can always be made.