Arvada, CO Environmental Rules: Flood Zones (2026)

Section 4-1-2-1 traces the City's authority to "C.R.S. Title 29, Article 20," which "delegated the responsibility of local government units to adopt regulations designated to minimize flood losses." The Regulatory Floodplain is built from FEMA's Flood Insurance Studies for both counties Arvada sits in: the Jefferson County FIS and DFIRM dated January 15, 2021, and the Adams County FIS and DFIRM dated September 28, 2018, per Section 4-1-2-5.A.1. The floodplain splits into a Flood Fringe Sub-Zone and a Floodway Sub-Zone, and Section 4-1-2-7.B.3 sets the residential freeboard standard: new construction and substantial improvements "shall have the lowest floor (including the basement and any mechanical equipment or attendant utilities) constructed at or above the flood protection elevation of two feet above the base flood elevation." Nonresidential buildings get a one-foot freeboard, or may instead be engineered watertight and certified by a Colorado professional engineer under Section 4-1-2-7.B.4.

Every project in the floodplain needs a Floodplain Development Permit under Section 8-3-5-6, reviewed by the Floodplain Administrator (the City Engineer or a designee under Section 8-1-1-4), who checks compliance with Division 4-1-2, confirms other federal and state approvals are in hand, and determines the site will be reasonably safe from flooding. Floodway Sub-Zone development is far more restricted: Section 4-1-2-8.B.4 bars any development that "would result in any increase in flood levels during the occurrence of the base flood discharge." Property owners who disagree with a Floodplain Administrator decision can appeal to the Floodplain Hearing Officer under Section 8-1-1-5, or seek a variance through the same office.