Floodplain Remapping Project

Background

Following the 2013 Flood, the Colorado Water Conservation Board (CWCB) initiated a program to re-map the predicted 1% annual chance flood zone (100-year floodplain) of the most affected waterways (shown in the image below). The program was called the “Colorado Hazard Mapping Program,” or CHAMP. Draft map data and related flood studies for the CHAMP– studied reaches were adopted by the Board of County Commissioners (BOCC) through Docket Z-17-0001 and Docket Z-17-0002. In September 2019, FEMA released Preliminary Flood Insurance Rate Maps (FIRMs) for the same CHAMP reaches, refining the draft maps. The Preliminary FIRMs were adopted by the BOCC, replacing the draft map data via Docket Z-19-0001 to allow the county to base floodplain regulations on the best available data.

In 2020 and 2021, FEMA ran appeal periods, where anyone had the opportunity to appeal or comment on the Preliminary FIRMs. Following FEMA’s resolution of the appeals, revised Preliminary FIRMs were released in July 2023. Boulder County aligned the Boulder County Floodplain and Floodway with the revised Preliminary FIRMs through Docket Z-23-0001. On October 24, 2024, the revised Preliminary FIRMs became effective for flood insurance purposes.

Lefthand Creek Re-Study

Due to an appeal, the portion of Lefthand Creek between Geer Canyon and 49th Street was excluded from the 2024 FIRM update and is being re-studied by the Federal Emergency Management Agency (FEMA). Letters were sent to affected property owners in May 2025. If you wish to receive email updates regarding the Lefthand Creek re-study, contact FloodplainAdmin@bouldercounty.gov.

A virtual public meeting for the Lefthand Creek re-study is taking place on Tuesday, May 27 at 6 p.m. Affected property owners are invited to register and attend the Virtual Public Meeting on the Lefthand Creek Floodplain Mapping Update. After registering, you will receive a confirmation email containing information about joining the webinar. A recording will be available shortly after the meeting.

Please contact the Floodplain Management Team (info below) with questions or to learn more about the floodplain mapping changes.

Floodplain Remapping Stream Reaches for 2019-2020 Effort

View the Map Accessibility Disclaimer.

View Maps

The interactive web map (button below), shows detailed flood risk zones and related FEMA map amendments that are currently regulated throughout unincorporated Boulder County as Floodplain Overlay Zoning District. This map will update as new FEMA maps become effective throughout Boulder County and as the Boulder County Board of County Commissioners (BOCC) adopts best available information.

The Boulder County and FEMA Regulatory Flood Risk Zones were updated on October 24, 2024 to reflect changes to the Floodplain Overlay District based on FEMA’s Physical Map Revision reflecting the Colorado Hazard Mapping Program (CHAMP) study. The zoning map amendments were adopted by the BOCC via Docket Z-23-0001.

New Information

• New Flood Insurance Rate Map (FIRM) effective date – Oct. 24, 2024
• View Zoning Map Amendments to the Floodplain Overlay District, Docket Z-23-0001
• Subscribe to receive timely email updates