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Are You in a Floodplain?

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Floodplain maps help property owners determine if their property is at risk for flooding and if the property is within a regulatory floodplain. Regulatory floodplain maps (also known as effective floodplain maps) 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

Legend for Floodplain Inquiry Map

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. Compare your results to the legend.

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. Flood insurance is much less expensive if the property is located outside the blue areas. 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. Learn more about Elevation Certificates and how to obtain one for your building in "Elevation Certificates: Who Needs Them and Why," a FEMA Fact Sheet (PDF).

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 include more accurate topography, flow rates (hydrology), public works projects (such as Resilient St. Vrain), and other items. 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 GREEN on the Floodplain Inquiry Map. To view this map layer, go to the "List of Layers" icon underneath the "Search by Address" box and check the layer titled "Draft 100 Yr Floodplain for St. Vrain Creek." 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 early 2019.

The "Draft 500 Yr Floodplain for St. Vrain Creek" is also available for viewing. It is shown in PURPLE 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 RED on the Floodplain Inquiry Map. To view this map layer, go to the "List of Layers" icon underneath the "Search by Address" box and check the layer titled "Draft 100 Yr Floodplain for Left Hand Creek." Use the + and - buttons to zoom in and out.

  • This map represents possible new floodplain for Left Hand Creek using the increased flows adopted by Longmont, the State and FEMA after the 2013 flood.
  • This map has not been submitted to FEMA for review. At this time, this map is strictly for information only.

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 and are not FEMA regulatory maps. To view these boundaries, go to the "List of Layers" icon underneath the "Search by Address" box and check the layer titled "Lykins Gulch and Spring Gulch #1 100 Yr Floodplain (City Mapped)." 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 "2013 Flood Extents - Boulder County" and / or "2013 Flood Extents - Weld County." Use the + and - buttons to zoom in and out.

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.

Need More Information?

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

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