FEMA flood zone rules in Larimer County, CO β also called floodplain regulations or special flood hazard area (SFHA) rules β determine flood insurance requirements and elevation standards for new construction.
Larimer County has been an NFIP-participating community since 1974 and administers floodplain regulations under Article 12 of the Land Use Code. A Floodplain Development Permit (FDP) is required before any development in regulated floodplains, including the FEMA Floodplain, Best Available Floodplain, Municipal Floodplain, Poudre GMA Floodplain, and County Flood-Prone Areas. Substantial improvement (50% of market value) triggers full compliance. New construction in the floodway is prohibited. Big Thompson and Cache la Poudre corridors carry the highest risk after the 1976 and 2013 floods.
Larimer County joined the FEMA National Flood Insurance Program in 1974. Floodplain regulations are codified in Article 12 of the Larimer County Land Use Code (effective June 1, 2023) and administered by Larimer County Engineering. The county recognizes five regulated floodplain types: the FEMA-mapped Floodplain (Zones A, AE, AO, AH, and floodway), the Best Available Floodplain (using updated studies like the Colorado Hazard Mapping Program post-2013-flood Big Thompson maps), Municipal Floodplain mapping forwarded by cities, the Poudre Growth Management Area Floodplain coordinated with Fort Collins, and County Flood-Prone Areas. A Floodplain Development Permit (FDP) is required before construction begins for any 'development' in the Floodplain Protection District - including new structures, substantial improvements, fill, grading, stockpiling, and storage of materials. New buildings in the regulatory floodway are prohibited, and substantial improvements to existing floodway structures are heavily restricted. The 'substantial improvement' threshold is the NFIP standard of 50% of the structure's pre-improvement market value, triggering full floodplain compliance. Colorado Water Conservation Board rule 2 CCR 408-1 requires at least 1 foot of freeboard above base flood elevation for residential structures statewide; Larimer County enforces this minimum. The Big Thompson River corridor was reshaped by the catastrophic 1976 Big Thompson Canyon flood (one of the deadliest in Colorado history) and the September 2013 floods, which prompted new CHAMP-based maps. The Cache la Poudre River corridor through Fort Collins is also high-risk. Applications and questions go to Larimer County Engineering at 970-498-5700.
Development in a regulated floodplain without an approved Floodplain Development Permit violates Land Use Code Article 12 and triggers stop-work orders, after-the-fact permitting requirements, structure removal, and daily administrative penalties under Article 22. Substantial-improvement violations can disqualify the property from NFIP flood insurance. Federal penalties under 44 CFR Part 60 may apply if the county is found out of compliance with NFIP standards. Floodway violations carry the most severe consequences, including required demolition.
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