O'Fallon, MO Environmental Rules: Flood Zones (2026)
FEMA flood zone rules in O'Fallon, MO, also called floodplain regulations or special flood hazard area (SFHA) rules, determine flood insurance requirements and elevation standards for new construction.
Key Facts
- Permit required
- Before any development in a flood hazard area
- Issuing official
- Floodplain Administrator
- Required disclosure
- Lowest floor elevation for every structure
- Non-residential option
- Flood-proofing with engineer/architect certification
- Penalty
- Misdemeanor, each day a separate offense
Summary
Any construction or development inside an O'Fallon flood hazard area needs a floodplain development permit before work starts, under Code Section 415.150. That covers new buildings, substantial improvements, and even watercourse alterations, and applies to any person, firm, corporation or unit of government.
A floodplain development permit shall be obtained before construction or development begins within any area of special flood hazard established in Article III, Section 415.070. No person, firm or corporation or unit of government shall initiate any development or substantial improvement or cause the same to be done without first obtaining a separate permit for each development as defined in Section 415.010.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4860992; v58 updated 2026-05-14; through 05-14-2026).
Full Breakdown
The permit application must go to the Floodplain Administrator on City-furnished forms, with plans drawn to scale showing the location, dimensions and elevations of the site, existing or proposed structures, fill and drainage facilities. 190(A)(2). Any proposal to alter or relocate a watercourse must describe the extent of that change; the Floodplain Administrator must notify adjacent communities and the Missouri State Emergency Management Agency beforehand and send proof of that notice to FEMA. The Administrator's other duties include confirming that all other required federal, state or local approvals have been obtained, verifying and recording actual elevations of completed structures, and using the best available federal, state or other data to set base flood elevations in Zone A areas where FEMA has not mapped one.
Violations & Fines
Violating any provision of the Flood Hazard Prevention Code, including building without the required permit, or breaching a condition attached to a variance, is a misdemeanor under Section 415.250. On conviction, the penalty is a fine or imprisonment as set by the City's general penalty section, Section 100.010, plus all costs and expenses of the case, with each day the violation continues counted as a separate offense; the City can also pursue any other lawful remedy to stop or fix the violation.
Frequently Asked Questions
Do I need a special permit to build in an O'Fallon flood hazard area?
What has to be in an O'Fallon floodplain development permit application?
What happens if I develop in an O'Fallon floodplain without a permit?
Sources & Official References
Other rules in O'Fallon
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