Rialto, CA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Governing section
- RMC 18.75.170(C)
- Required freeboard
- 1 foot above base flood elevation
- AO zone alternative
- 2 ft above grade if no depth number
- State recommendation
- 2 feet (not adopted locally)
- Nonresidential option
- Flood-proofing, engineer-certified
Summary
New and substantially improved residential structures in Rialto's mapped flood zones must have their lowest floor, including any basement, elevated at least one foot above the base flood elevation determined for the site. Nonresidential buildings may flood-proof instead.
C.Elevation and flood proofing... 1.Residential construction, new or substantial improvement, shall have the lowest floor, including basement,... b.In an A zone, elevated one foot above the base flood elevation; said base flood elevation shall be determined by one of the methods in Section 18.75.150(B) of this chapter. (The state of California recommends the lowest floor be elevated at least two feet above the base flood elevation, as determined by the community) c.In all other zones, elevated one foot above the base flood elevation. (The state of California recommends the lowest floor be elevated at least two feet above the base flood elevation.)
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 39).
Full Breakdown
170(C) sets Rialto's elevation and floodproofing standard. 150(B). In all other zones the same one-foot freeboard above base flood elevation applies; in an AO zone, the floor must sit at least one foot above the FIRM's depth number, or two feet above the highest adjacent grade if no depth number is specified. The code notes that the State of California recommends a more conservative two-foot freeboard, but Rialto's adopted local standard is one foot. 170(C)(2). 170(C)(3). 200.
Violations & Fines
Constructing or substantially improving a structure without meeting the elevation or floodproofing standards of Section 18.75.170 violates Chapter 18.75 and constitutes a misdemeanor under Section 18.75.080; the floodplain administrator can also require remedial action and documentation under Section 18.75.150(F)-(H).
Frequently Asked Questions
How high above base flood elevation must my Rialto home's floor be?
Can a commercial building be flood-proofed instead of elevated?
Does Rialto follow the state's recommended two-foot freeboard?
Sources & Official References
Other rules in Rialto
California rules heatmap·Compare Rialto to another location·View the California environmental rules overview
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Flood Elevation Requirements in Nearby Cities
How other cities in San Bernardino County handle flood elevation requirements.