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Floodplain Development

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A floodplain is low-lying ground close to a river that is at risk for flooding. Building or performing work on a structure in a floodplain has special requirements to help keep everyone safe. The City of Boulder's floodplain regulations are designed to reduce risk to life and property in areas along the 16 major drainageways within the city limits. The regulated floodplain currently covers about 15% of Boulder including over 2,500 individual structures.

Please review information about Stream, Wetland, and Water Body Permits for more information about construction in those areas. 

The City of Boulder regulates development based on FEMA Flood Insurance Rate Maps of the 1% Annual Chance Storm (aka the 100-year floodplain). Property owners of buildings with any portion of the structure (including roof overhang, gutters, footings, decks, balconies, etc.) encroaching into the 100-year floodplain are required to obtain a Floodplain Development Permit before expanding a building or constructing any improvements.

To apply for a permit you will need:

Is your property in the floodplain? Use the city's interactive Map of Floodplains and FEMA's Map Service Center to find out!

To request formal documentation from city staff about the floodplain designation of your property (usually required by insurance providers) apply for a Floodplain Information Request through the Customer Self-Service Portal

A request can be made to remove your property from the floodplain if your structure is elevated or if a property was incorrectly mapped. To remove your property or structure from the floodplain, you will need:

  • A licensed land surveyor to check if your property qualifies for a Letter of Map Amendment (LOMA) which will remove it from the floodplain.
  • A licensed land surveyor to complete a FEMA Elevation Certificate
  • To submit your elevation certificate and LOMA application directly to FEMA

It should be noted that, although Boulder’s floodplain mitigation and regulation is aligned with a 100-year flood, that doesn’t mean flooding can’t happen outside of the floodplain at any time.

Check to see if your property has an elevation certificate on file with the city's building department.

Enter an address or a street name in the box above and click on "Search" to look for a specific Flood Elevation Certificate (example: 1555 Arapahoe Ave or Arapahoe Ave)