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  • Floodplain Map
  • Creeks of Boulder
  • Floodplain Development
  • Be Prepared
  • Community Resilience

Maps of Floodplains

Floodplain maps provide the basis for floodplain management, regulation, and insurance requirements by identifying flood-prone areas that may threaten life and property. Floodplain maps are reviewed and approved by FEMA for flood insurance purposes. Floodplain maps guide flood management programs, including floodplain regulation, safety, preservation, preparation and mitigation.

To have city staff look up your floodplain information, fill out the Floodplain Information Request (Fax) pdf form and either fax it to 303-441-4241 or drop it off in-person at the Planning and Development Services Center at 1739 Broadway, third floor.  Please note that there is a fee for this service.

You can also get a Public Flood Map or a Flood Insurance Rate Map from the FEMA Map Service Center.

Floodplain Map Changes

Floodplain maps are periodically updated and revised to reflect changing conditions, such as impacts of flooding, new topography, land development, updated mapping studies, and construction of floodplain improvements.

Floodplain map changes can take several forms:

  • Local Map Changes
  • Flood Insurance Rate Maps (FIRMs) or Digital Flood Insurance Rate Maps (DFRIMs)
  • Letters of Map Change (LOMCs)
  • Conditional Letters of Map Amendment (CLOMAs)

Changes to the Flood Map

The Flood Insurance Rate Map (FIRM) identifies areas in a community that are subject to flooding and shows the risks associated with these flood hazards. One of the areas shown on a FIRM is a Special Flood Hazard Area (SFHA), or the 100-year floodplain. This area has a one percent or greater chance of flooding in any given year.

FEMA uses the most accurate flood hazard information available and applies rigorous standards while developing FIRMs. However, because of limitations of scale or topographic definition on the source maps, there may be elevated areas or "islands" that are not actually in the new regulatory floodplain shown on the maps. These island areas may appear relatively small on the FIRM and are sometimes included in the 100-year floodplain by nationwide floodplain map determination companies that prepare floodplain designations on behalf of the mortgage industry. Such cases are referred to as "inadvertent inclusions."

The City of Boulder will attempt to identify any inadvertent inclusions and notify the property owners of the Letter of Map Amendment (LOMA) processes and the "grandfather" provisions of the NFIP that may apply to their situations.

Letter of Map Amendment (LOMA) Process

If your property is an inadvertent inclusion, you can submit a Letter of Map Amendment (LOMA) or a Letter of Map Revision Based on Fill (LOMR-F) to change the designation of your property and avoid the federal flood insurance requirements for properties located in the 100-year floodplain. In most cases, you will need to hire a licensed land surveyor or registered professional engineer to prepare an Elevation Certificate for the property. FEMA will normally complete its review and issue a decision in four to six weeks.

The issuance of a LOMA or LOMR-F eliminates the federal flood insurance requirement as a condition of federal or federally-backed financing; however, mortgage lenders can still require flood insurance as a condition of providing financing, regardless of the location of a structure.

Purchasing a flood insurance policy is wise even if your property is located outside of the 100-year floodplain. More than 25 percent of claims are made by property owners located outside the 100-year floodplain.

LOMA and LOMR-F determinations cannot be made by FEMA until after a flood mapping study is officially adopted. However, if you think you qualify for a LOMA or LOMR-F determination, you may want to confirm this by contacting a licensed land surveyor or registered professional engineer today.

Grandfather Provisions

If your home was previously considered outside the 100-year floodplain and was constructed without flood protection measures, you may be eligible for reduced insurance rates.

The NFIP offers Grandfather Provisions for structures built in compliance with the Flood Insurance Rate Map (FIRM) that was in effect at the time of construction, as well as structures built before a rate map was in place.

If your building was constructed before July 17, 1978 (Pre-FIRM construction), you are eligible to maintain the prior flood zone and base flood elevation as long as you maintain continuous coverage and purchase your policy before the revised FIRM goes into effect. The flood policy can also be assigned to a new owner at the option of the policyholder. If you do not obtain a policy for a Pre-FIRM building before the effective date of the FIRM change, then you are eligible to receive the Pre-FIRM (subsidized) rates based on the new flood zone rather than the actual elevation-based rates.

If your building was constructed after July 17, 1978 (Post-FIRM construction), you are eligible to maintain the prior flood zone and base flood elevation as long as you maintain continuous coverage and purchase your policy before the revised FIRM goes into effect. The flood policy can also be assigned to a new owner at the option of the policyholder. If the building was constructed in compliance with a specific FIRM, you are eligible to obtain a policy using the flood zone and base flood elevation from the FIRM that was in place at the time of construction. Proof of the compliant construction and FIRM in place at the time of construction must be submitted to the insurance company as part of obtaining a policy. Continuous flood insurance coverage is not required to remain eligible for this rating.

Preferred Risk Policies

  1. Buildings written on Preferred Risk Policies are required to be located in zones B, C, or X on the FIRM in effect on the date of application and on the date of each subsequent renewal.
  2. A building that becomes ineligible for a Preferred Risk Policy due to a map change to a special flood hazard area (100-year floodplain) can be rewritten on a standard rated policy using zones B, C, or X.