Johnson County, IA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard requirement
- 1 foot above base flood elevation
- Applies to
- New/substantially improved residential structures
- Fill extension
- At least 18 feet beyond structure
- Non-residential option
- Elevate or floodproof to same level
- BFE increase cap
- Development can't raise BFE over 1 foot
- Enforcing agency
- Zoning Administrator, Johnson County
- Coverage area
- Floodway Fringe Overlay District, unincorporated county
Summary
New and substantially improved residential structures in Johnson County's Floodway Fringe Overlay District must have their lowest floor, including any basement, elevated at least one foot above the base flood elevation. Non-residential structures can meet the same one-foot freeboard either by elevation or by certified floodproofing to that level.
All new or substantially improved residential structures shall have the lowest floor, including basement, elevated a minimum of one (1) foot above the base flood elevation. Construction shall be upon compacted fill which shall, at all points, be no lower than one (1.0) feet above the base flood elevation and extend at such elevation at least eighteen (18) feet beyond the limits of any structure erected thereon.
Official source re-checked September 7, 2026: the cited page had not changed since it was quoted.
Full Breakdown
8(B) sets performance standards for the Floodway Fringe Overlay District, which covers areas mapped as Zone AE outside the regulated floodway. Until a regulatory floodway is designated, no development may raise the base flood elevation by more than one foot, and the applicant must supply the Iowa DNR with the technical data to prove it. 8(B)(2) requires the lowest floor, including any basement, to sit at least one foot above the base flood elevation, built on compacted fill that is no lower than one foot above BFE and that extends at least 18 feet beyond the structure in every direction; where fill is impractical because of topography or street grades, piers or extended foundations may substitute if they can withstand flood forces.
2(3) of the Iowa Administrative Code. 8(B)(3) get a choice: elevate the lowest floor one foot above BFE the same way, or floodproof the structure and its utility and sanitary systems to that level. Floodproofing must be certified by a professional engineer registered in Iowa as watertight and able to withstand the flood's depth, pressure, velocity, and impact and uplift forces, and the Administrator keeps a record of the certified elevation referenced to the 1929 North American Vertical Datum.
Violations & Fines
Floodplain violations are enforced under UDO Chapter 8:8. A civil infraction runs up to $750 for a first offense and up to $1,000 for a repeat violation of the same section. Where no other penalty is specified, a criminal violation carries a fine up to $625 and up to 30 days in jail, with each day of noncompliance treated as a separate offense. The Zoning Administrator may also revoke the development permit or issue a stop-work order, and the Board of Supervisors can seek a restraining order or abatement through the County Attorney.
Frequently Asked Questions
How much freeboard does Johnson County require above the base flood elevation?
Can I use fill to raise my house instead of building on piers?
Does floodproofing count instead of elevating a building?
Can new development raise the base flood elevation on neighboring property?
Sources & Official References
Other rules in Johnson County
Compare Johnson County to another location·View the Iowa environmental rules overview
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