Story County, IA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard requirement
- 3 feet above the 100-year flood elevation
- Fill extension
- at least 18 feet beyond the structure
- Accessory structure exemption
- up to 600 sq. ft.
- RV exemption
- under 180 consecutive days on site
- Enforcing office
- Story County Floodplain Manager
- Variance
- requires Board of Adjustment + Iowa DNR concurrence
Summary
In unincorporated Story County, new or substantially improved residential structures in the floodway fringe must have the lowest floor, including any basement, elevated a minimum of three feet above the one percent annual chance flood level. Compacted fill supporting the structure must hold that same three-foot freeboard and extend at least 18 feet beyond the structure. The Floodplain Manager enforces the standard under Chapter 80.
All new or substantially improved residential structures shall have the lowest floor (including basements) elevated a minimum of three (3) feet above the one percent annual chance or greater flood level. Construction shall be upon compacted fill meeting the requirements in Subsection 80.13.3.A which shall, at all points, be no lower than three (3) feet above the one percent annual chance or greater flood level and extend at such elevation at least 18 feet beyond the limits of any structure erected thereon.
Full Breakdown
Story County's floodplain ordinance (Chapter 80 of the Code of Ordinances) sets the three-foot freeboard as the baseline flood-protection standard for the Floodway Fringe District. 13(3)(C), every new or substantially improved residential structure, including additions and factory-built homes, must have its lowest floor, basements included, at least three feet above the one percent annual chance (100-year) flood level, built on compacted fill that holds that elevation for at least 18 feet beyond the structure's footprint. 23. 13(3)(B). 13(3)(L) lets small accessory structures, such as detached garages and sheds up to 600 square feet, skip the freeboard requirement if they carry no habitation use, use flood-resistant materials below one foot above the flood elevation, and elevate electrical and heating equipment three feet.
Recreational vehicles are also exempt from the anchoring and elevation rules if they stay on site fewer than 180 consecutive days and remain licensed and ready for highway use. 15.
Violations & Fines
Violations of Chapter 80's floodplain standards are enforced under Chapter 3 of the county code (§ 80.29). Each violation is a county infraction carrying a civil penalty of up to $750 for a first offense and up to $1,000 for each repeat offense, with every day of a continuing violation counted separately. The Floodplain Manager can deny or revoke a permit and require a professional engineer's compliance certification before occupancy, and the County may also seek abatement or an injunction in district court.
Frequently Asked Questions
Does a shed in the floodplain need the 3-foot freeboard?
Can I elevate my house on piers instead of fill?
How long can a camper sit on my floodplain lot without meeting the elevation rules?
Who issues the floodplain development permit?
Sources & Official References
Other rules in Story County
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