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Boulder Creek Floodplain Mapping Update

Boulder Creek Floodplain Mapping Update

The Boulder Creek Floodplain Mapping Study evaluated the floodplain from the area west of 61st Street, upstream to the mouth of Boulder Canyon, west of Boulder city limits. The study area encompassed a reach length of five and a half miles.

Based on this study, the city has developed new floodplain maps for Boulder Creek that would replace both the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Boulder floodplain map.

The proposed floodplain maps were developed based on:

  • updated topographic data,
  • updated floodplain, floodway and high-hazard zone boundaries, and
  • city improvements that help reduce flooding along Boulder Creek.


The Federal Emergency Management Agency (FEMA) is proposing to adopt the updated floodplain maps for Boulder Creek and incorporate the new floodplain mapping into the Flood Insurance Rate Maps. There is a statutory 90-day appeal period from May 5, 2016 to Aug. 2, 2016 for anyone who is interested in appealing FEMA's proposed map adoption.

The new floodplain mapping was adopted by City Council on Sept. 18, 2012 and is currently regulatory.  FEMA began reviewing the mapping on Oct. 30, 2012.  Final project documentation was submitted to FEMA in September 2013. In November 2013, FEMA indicated that they accepted the results of the study and will be adopting the new mapping through the Physical Map Revision process, which is a multi-year process. The process was delayed due to the September 2013 flooding.  FEMA released Preliminary Flood Insurance Rate Maps (FIRMs) on July 23, 2015 and held an Open House meeting Wednesday, Sept. 16, 2015.  These maps are available on FEMA's website:  

The new FIRMs are anticipated to become effective December of 2017, although this schedule is subject to change. Please see the link to the FEMA fact sheet for more information. 

Previous Meetings

City Council Public Hearing - Tuesday, Sept. 18, 2012
The Utilities Division provided City Council with an update on the current status of the Boulder Creek Floodplain Mapping Update and requested approval of the study. City Council voted unanimously to approve the floodplain mapping study and directed staff to submit the study to the FEMA for review and adoption.

Planning Board Public Hearing - March 15, 2012
The Planning Board voted 4-0 to recommend approval of the flood mapping study.

Water Resources Advisory Board (WRAB) Public Hearing - Feb. 27, 2012
The WRAB voted 4-0 to recommend approval of the flood mapping study.

Study Results

The final report and all attachments, including photos and maps, are available under the "Technical Report" links on this webpage.

To see the revisions to the floodplain maps, select the "Floodplain Map (interactive)" link. The revised Boulder Creek mapping can be viewed by selecting "Revised Boulder Creek Flood Layers" and then choose different layers for viewing.

Please Note: These maps may not be completely comprehensive due to data limitations. Staff will continue to make enhancements and modifications as needed.

For property-specific information about the land development requirements for all floodplain zones, contact Planning & Development Services at 303-441-1880 or


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