Floodplain Remapping

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. The program was called the “Colorado Hazard Mapping Program,” or CHAMP. Visit the CHAMP website to learn more.

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 Town of Lyons Board of Trustees, replacing the draft map data, to allow the county to base floodplain regulations on the best available data. In 2021, upon final FEMA approval and adoption, the floodplain mapping will be formalized for flood insurance purposes.

Please contact floodplain@townoflyons.com with questions or to learn more about the floodplain mapping changes.

Interactive Preliminary Floodplain Map

Preliminary Floodplain Map 2020
View Lyons' Preliminary floodplain map, as re-mapped by Colorado Hazard Mapping Program in 2019.
 Learn more about Colorado Hazard Mapping.

What is the timeline of the CHAMP process?


Phase I data was submitted by CHAMP to FEMA in the spring of 2017 and Phase II data was submitted in the spring of 2018. FEMA issued Preliminary Flood Insurance Rate Maps (FIRMs) based on CHAMP data in September 2019. The FEMA process after receiving Preliminary FIRMs includes a formal public comment and appeal period (anticipated for spring 2020), further analysis, and the release of final effective FIRMs. The timeline for this phase of the FIRM development process can last 18 months or longer and is dependent upon FEMA timelines and budgets.

How are the maps produced?


Maps are generated by combining ground surveying information and topographical data, anticipated rainfall and river flows, and then using modeling software to develop flood profiles and flood inundation maps. The process of developing floodplain maps is a technical undertaking by well-qualified professionals.

Who is affected?


The CWCB floodplain maps and associated data will be more accurate and ultimately replace the regulatory floodplain maps currently in use. Both the flood elevations and the floodplain boundaries are likely to change. Any resident or property owner within or near a current regulatory mapped floodplain may be affected by the new maps in terms of development regulations and eventually flood insurance requirements.

When do the draft maps or Preliminary FIRMs become effective?


Boulder County locally adopted the draft maps developed from the CHAMP study for regulatory purposes shortly after they were submitted to FEMA for initial review.

The Lyons Board of Trustees adopted Ordinance 1075, on January 21, 2020, adopting best available data, which uses both the existing FIRM and the Preliminary FIRM to regulate development. These new regulations (Ordinance 1075) will go into effect on March 13, 2020. Local adoption of the Preliminary FIRMs does not impact flood insurance requirements and rates.

Preliminary FIRMs

08013C0232K - Northern Lyons

08013C0232K - Northern Lyons

08013C0231K - Apple Valley

08013C0231K - Apple Valley

08013C0234K - Eastern Corridor

08013C0234K - Eastern Corridor

08013C0253K

08013C0253K

When will FEMA adopt the CHAMP mapping?


FEMA adoption of the CHAMP mapping is anticipated by 2021 for the entire area. Formal public comment will be collected as part of the FEMA adoption process. Once adopted by FEMA, the maps become the effective Flood Insurance Rate Maps (FIRMs) and will then be used for both insurance and regulatory purposes.

On February 10, 2020, the Town of Lyons held a public meeting to present the Preliminary FIRMs. The slides below were presented at the meeting (click each to expand).

CHAMP Presentation

CHAMP Presentation Feb 2020_Lyons_BoCo

Town of Lyons Regulatory Flood Map 4

Town of Lyons Regulatory Flood Map 4

Town of Lyons Regulatory Flood Map 4 - Close

Town of Lyons Regulatory Flood Map 4 - Close