Riverside, CA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- BFE Definition
- 1%-annual-chance flood elevation, § 16.18.025
- Elevation Rule
- Lowest floor at/above BFE, § 16.18.100(C)(1)
- AO Zone Minimum
- 2 ft above highest adjacent grade if no depth given
- Certification Required
- Registered civil engineer or licensed surveyor
- Filing Office
- Public Works Department
- Penalty
- Misdemeanor, RMC § 16.18.035; presumed violation if uncertified
Summary
New and substantially improved residential buildings in a Riverside flood hazard zone must have their lowest floor 'elevated to or above the base flood elevation' under RMC § 16.18.100(C)(1). Base flood elevation (BFE) is defined in § 16.18.025 as the FIRM water-surface elevation for a flood with a one-percent annual chance of occurring, and elevation must be certified by a registered civil engineer or licensed surveyor.
Base flood elevation (BFE) means the elevation shown on the Flood Insurance Rate Map for Zones AE, AH, A1-30, VE and V1-V30 that indicates the water surface elevation resulting from a flood that has a one percent or greater chance of being equaled or exceeded in any given year...Upon the completion of the structure pad, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community inspector to be properly elevated. Such certification and verification shall be filed by the Public Works Department. All new construction or substantial improvements of residential structures shall have the lowest floor, including basements: a. In AE, AH, A1-30 Zones, elevated to or above the base flood elevation. b. In an AO Zone, elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 33).
Full Breakdown
100(C)(1) sets the construction standard: upon completion of the structure pad, the lowest floor elevation, including any basement, 'shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community inspector to be properly elevated,' with that certification filed by the Public Works Department. ' In an AO zone without a specified depth number, the floor must sit 'at least two feet above the highest adjacent grade,' or match the FIRM's specified depth number if one exists. 055 using FEMA guidance.
100(C)(2), certified by a registered civil engineer or architect. 100(C)(3), letting their floor sit below the BFE only if flood-resistant materials, anchoring, and automatic floodwater-entry design requirements are met.
Violations & Fines
RMC § 16.18.035 makes it a misdemeanor to construct or alter a structure without complying with Chapter 16.18, including the elevation standards of § 16.18.100. RMC § 16.18.065 separately requires the lowest-floor elevation certification for every covered structure to be documented and kept on file, and the chapter's own definition of 'Violation' in § 16.18.025 states an uncertified structure 'is presumed to be in violation until such time as that documentation is provided.'
Frequently Asked Questions
How high above flood level must a Riverside home be built?
Who has to certify a building's flood elevation in Riverside?
What is 'base flood elevation' under Riverside's code?
Sources & Official References
Other rules in Riverside
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Flood Elevation Requirements in Nearby Cities
How other cities in Riverside County handle flood elevation requirements.