Colorado Hazard Mapping Program (CHAMP) PDF

The 2013 flood event caused widespread damage and changes along waterways throughout the County and in other areas of the state. In response, the State of Colorado is taking steps towards bolstering long-term planning and resiliency efforts by funding the Colorado Hazard Mapping Program (CHAMP) that will update local hazard information including regulatory floodplain maps for the most affected waterways.

Draft floodplain boundaries for CHAMP Year 1 are now available on the Larimer County Flood Information Locator. The draft floodplain maps will also be presented at three open house meetings in October 2017. 

Comments and questions can also be submitted to the Larimer County Engineering Department using the Comments or Questions Card.

Larimer County joined the National Flood Insurance Program in 1974 and has been active in floodplain management since that time. Floodplains are regulated as an overlay zone in Larimer County. The floodplain regulations and the floodplain maps provide the foundation for Larimer County's Floodplain Management Program.

The links to the maps below can be used to determine the limits of the regulatory floodplains in Larimer County. The Larimer County Engineering Department can also be contacted to determine if a property is within a FEMA or locally designated floodplain. It should be noted that there are many areas in Larimer County that are not shown within a regulated floodplain and have undetermined flood hazards. A property can still be at risk of flooding even if the property is not shown in a regulatory floodplain.


  1. In 1968, Congress created the National Flood Insurance Program (NFIP) through the National Flood Insurance Act, making flood insurance available for the first time. In 1973, the Flood Disaster Protection Act amended the program by making flood insurance a mandatory condition for receiving Federal financial assistance or a federally backed loan if the building is located in a Special Flood Hazard Area. That same year, House Bill 1041 was passed by the Colorado Legislature, and provided alternative authority for counties to regulate floodplains. These statutes along with the Zoning Enabling Act were the basis for administration of floodplains.

    In July 1974, Larimer County joined the NFIP. This provided the opportunity for property owners in Larimer County to become eligible to purchase flood insurance at subsidized rates.

  2. On December 1, 1975, Larimer County adopted floodplain regulations as an amendment to the County Building Code and the Flood Review Board was created.

  3. Floodplains are an overlay zone in Larimer County. The most current floodplain regulations can be found in the Larimer County Land Use Code Section 4.2.2.

  4. A flood is a general and temporary condition of partial or complete inundation of normally dry land areas from:

    1. The overflow of water from channels and reservoir spillways;
    2. The unusual and rapid accumulation or runoff of surface waters from any source; or
    3. Mudslides or mudflows that occur from excess surface water that is combined with mud or other debris that is sufficiently fluid so as to flow over the surface of normally dry land areas (such as earth carried by a current of water and deposited along the path of the current).

    Floods occur for many reasons, such as long-lasting rainfall over a broad area, locally intense thunderstorm generated rainfall, or rapid melting of a large snow pack with or without accompanying rainfall. Because floods result from many different circumstances, not all floods are equal in magnitude, duration, or effect.

  5. In the 1960’s, the United States government decided to use the 1-percent annual exceedance probability (AEP) flood as the basis for the National Flood Insurance Program. The 1-percent AEP flood was thought to be a fair balance between protecting the public and overly stringent regulation. Because the 1-percent AEP flood has a 1 in 100 chance of being equaled or exceeded in any 1 year, it is also referred to as the “100-year flood.”

  6. Floods happen irregularly. The “100-year flood” is an estimate of the long-term average recurrence interval, which does not mean that we really have 100 years between each flood of greater or equal magnitude. The “100-year flood” is also known as the 1-percent annual chance flood, which means that a flood of this magnitude has a 1- percent chance of occurring in any given year. A home in the 1-percent (100-year) floodplain has a 26-percent chance of being flooded at least once during the span of a 30-year mortgage.

  7. The floodplain is any area that is susceptible to being inundated by surface water from any source. Mostly, this is the area adjacent to a river, creek, lake, stream, or other waterway that is subject to flooding when there is a significant run-off event.

    The floodplain is typically divided into a floodway zone and a flood fringe zone. The floodway is the channel of a river and adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. These areas are expected to have the fastest and deepest flows during a flood. The flood fringe areas are the outer edges of the floodplain where flows are shallower and slower moving. 

    More about Floodplain, Flood Fringe and Floodways

  8. Certain uses are limited or even prohibited within the floodplain. In general, new structures, or substantial modifications or improvements to existing structures within the floodway overlay zone are difficult. The floodway is highly restricted for development purposes since this area should be reserved in order to convey the expected flows within these limits. There are fewer restrictions within the flood fringe areas and new structures and development is generally allowed as long as the development meets the County floodplain regulations including proper elevation requirements.

    You must be issued a Floodplain Development Permit from Larimer County before you start any work, including grading, excavation or filling, in any portion of the floodplain.

  9. Certain Special Flood Hazard Areas within Larimer County are designated as "Approximate Zone A" floodplains. Approximate Zone A floodplains are developed using limited flowrate and topographic information rather than more detailed information that includes Base Flood Elevations (BFEs). Generally, there is not a distinction between the floodway and flood fringe in Approximate Zone A floodplains.

    Before a building permit can be issued or development can occur within an Approximate Zone A floodplain, the property owner is required to provide a small, detailed study specific to that property outlining the limits of the floodplain. This requires hiring a licensed professional engineer and surveyor to better define the site topography and the flowrates and then use the detailed information to define the limits of the floodway, flood fringe and provide BFEs that can be used to meet minimum elevation requirements. No new development is allowed within the determined floodway zone of an Approximate Zone A floodplain.

  10. To determine if your property is within a FEMA or locally designated floodplain, you can contact the Larimer County Engineering Department or view the flood zone information through the County’s interactive map. Floodplain areas designated by FEMA on the Flood Insurance Rate Maps (FIRMS) are also available online through FEMA’s Map Service Center.

    Keep in mind that even if your property is not shown in a regulatory floodplain, it does not mean that there is no risk of flooding. There are many areas in Larimer County that are not shown within a regulated floodplain but have undetermined flood hazards.

  11. Structures in a floodplain may be damaged when flooding occurs. Some structures flood frequently, while others 
    get damaged only by the more severe events.

    Flood insurance may be required. If you receive a mortgage or loan from a federally regulated or insured lender, you are required to have flood insurance if the structure is located in a floodplain. Generally, flood insurance can be purchased by contacting your regular homeowner's insurance agent. Even if you are not required to have flood insurance, it can still be a good investment if you live in or near a floodplain.

    Structures in the floodplain must comply with floodplain regulations. Larimer County requires permits for remodeling, improving, expanding or rebuilding any structure in a floodplain. In order to reduce long-term flood damage, structures that are substantially improved or substantially damaged are required to become compliant with current floodplain regulations. Substantially damaged structures in a floodway cannot be repaired or replaced within the floodway if the damage was due to flooding. In Larimer County, the cost of improvements is tracked over a 10-year rolling period. Certain items defined under Routine Maintenance or Minor Work can be excluded. Please see the separate sections regarding Routine Maintenance, Minor Work, and Substantial Damage for detailed descriptions of these definitions.

  12. Routine maintenance are repairs necessary to keep a structure in a safe and habitable condition, do not trigger a building permit, and are not associated with a general improvement of the structure or repair of a damaged structure. Such repairs include:

    1. Normal maintenance of structures such as re-roofing, replacing roofing tiles and replacing siding;
    2. Exterior and interior painting, papering, tiling, carpeting, cabinets, counter tops and similar finish work;
    3. Basement sealing;
    4. Repairing or replacing damaged or broken window panes;
    5. Repairing plumbing systems, electrical systems, heating or air conditioning systems and repairing wells or septic systems.
  13. Small development activities (except for filling, grading and excavating) valued at less than $2000.

  14. Substantial damage is damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would equal or exceed 50 percent of the market value of the structure just prior to when the damage occurred.

  15. It depends on which overly zone the structure is located in. Any building that was constructed prior to implementation of the floodplain regulations has a non-conforming use designation and can remain in place indefinitely unless it is substantially damaged or substantially improved. Once it is substantially damaged or substantially improved, the structure must comply with current regulations, which prohibit certain uses.

    Within the floodway (critical zone), a substantially damaged structure may not be repaired or rebuilt per the Larimer County Land Use Code if the damage was caused by flooding. If the damaged was caused by something other than a flood or if the structure was located within the flood fringe (less critical zone), a substantially damaged structure may be repaired or rebuilt as long as it is elevated to the regulatory flood protection elevation.

  16. General maintenance such as clearing debris or excessive vegetation may be done without obtaining a floodplain development permit. Any bank restoration, armoring, channel improvements, etc. requires approval from Larimer County through the issuance of a floodplain development permit.

    Do not dump or throw anything into ditches or streams or within the floodplain: Trash and vegetation dumped into a stream degrades water quality and every piece of trash contributes to flooding.

    Report Violations: Report any observations of dumping debris or vegetation clearing within the floodplain to Larimer County at (970) 498-5729.

  17. You must submit a Floodplain Development Permit Application and required plans and documentation to Larimer County Engineering Department. Some projects within the floodplain will require approval from the Flood Review Board and/or the Board of County Commissioners. Formal Map changes will also require approval from FEMA. The application includes a checklist that outlines all required documentation and approval steps. The Floodplain Manager will review your application for compliance with the Flood Hazard Overlay Zone Districts. For information on the floodplain development permit, contact our Floodplain staff at (970) 498-5729 or send email.

  18. State and federal agencies may also require permits prior to approval of your floodplain development permit application with the County. It is your responsibility to obtain any necessary permits and approvals prior to submitting an application with Larimer County. Other agencies that may have applicable permits include, U.S. Army Corps of Engineers, Colorado Division of Water Resources, Environmental Protection Agency, Water Quality Control Division of the State Health Department, etc.

  19. You may apply for a building permit at the same time you apply for your floodplain development permit but a building permit will not be issued until the Floodplain Manager has approved your floodplain development permit. Therefore, it is recommended that you contact County Floodplain staff at (970) 498-5729 or send email prior to submitting your application. This helps address any areas of concern that may cease or delay the building permit process.

    Be sure to check your building permit for any conditions of approval that will need to be addressed during the construction phase and prior to a certificate of occupancy or letter of completion. Elevation and no-rise certificates are often required and must be completed by registered professional land surveyors and engineers licensed in the State of Colorado

  20. An elevation certificate is an official record showing that a structure or addition located within a regulatory floodplain is properly elevated. The FEMA form must be completed by a registered professional land surveyor licensed in the State of Colorado and must provide all necessary information to ensure the structure is elevated in accordance with the building requirements. If an elevation certificate is listed as condition on your building permit, a certificate of occupancy will not be issued until this is received.

  21. When work is proposed in a regulatory floodway, a no-rise certificate with supporting documentation is required. The no-rise certificate must be prepared by a professional engineer who is licensed in the State of Colorado. This certificate demonstrates that a proper engineering study has been conducted and verifies that the proposed work will not increase flood heights. The no-rise certificate is required to be submitted with your floodplain development permit application. This process generally requires Flood Review Board approval.

  22. If your project includes a map change request, a variance from Section 4.2.2 of the Larimer County Land Use Code, an expansion of a non-conforming use, a stream alteration, etc., approval from the Larimer County Flood Review Board is required.

    Project such as railroads, streets, roads, bridges, flood and water control structures, above and below ground utilities (excluding service connections), pipelines, marinas, boat rentals, docks, piers, and wharves that are located within a regulatory floodplain are processed as a Floodplain Special Review. These projects go to the Flood Review Board for a recommendation, and then go to the Board of County Commissioners for final approval.

  23. To be removed from the floodplain shown on the Flood Insurance Rate Map (FIRM), a structure must be on land that is not subject to flooding by a 100-year flood. Remember, more severe floods, erosion, debris blockages, etc. can and do happen, so even if your home is found to be on high ground, it may still be damaged by an extreme flood event.

    If your lot or building site is on natural ground that is higher than the Base Flood Elevation (BFE) shown on the FIRM, then you may request a Letter of Map Amendment (LOMA). To support your request, you will need to have a land surveyor or engineer determine the elevation of the ground next to your building and complete a FEMA Elevation Certificate. If the ground is higher than the BFE, then FEMA may issue a LOMA.

    If your home was built on fill that was placed after the FIRM was prepared (within the flood fringe overlay zone), you may request a Letter of Map Revision Based on Fill (LOMR-F). As with a LOMA, a FEMA Elevation Certificate will need to be completed by a land surveyor or engineer. If the filled ground is higher than the BFE, and if you do not have a basement, then FEMA may issue a LOMR-F.

  24. Any building that was constructed prior to implementation of the floodplain regulations has a legal non-conforming use designation and can remain in place indefinitely unless it is substantially damaged or substantially improved. Once it is substantially damaged or substantially improved, the structure must comply with current regulations.



Attn Floodplain
Larimer County Engineering Department
200 West Oak Street, Suite 3000
P.O. Box 1190
Fort Collins, CO 80522-1190

(970) 498-5729