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Benton County, OR Environmental Rules: Flood Elevation Requirements (2026)

Some Restrictions
Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

Key Facts

Residential freeboard
18 inches above BFE
Non-residential freeboard
18 inches above BFE (or floodproof)
Critical facilities
3 ft above BFE or 500-yr flood
Datum
mean sea level (NAVD 1988)
Certification required
Pre/Mid/Post-Construction Elevation Certificates
Administered by
County Floodplain Administrator

Summary

Unincorporated Benton County requires the lowest floor of new or substantially improved residential structures in a special flood hazard area to sit at least 18 inches above the Base Flood Elevation (BFE), the height of base-flood waters expressed in feet above mean sea level. Critical facilities such as schools and fire stations must clear the BFE by a full 3 feet, or the 500-year flood height, whichever is higher.

These county ordinances apply to unincorporated areas of Benton County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

(5)"Base Flood Elevation" means the height of the flood waters during a base flood at points along the water course, expressed in feet above mean sea level. ... Critical facilities constructed within the SFHA shall have the lowest floor elevated 3 feet above the Base Flood Elevation (BFE) or to the height of the 500-year flood, whichever is higher. ... (1)Where allowed, new construction, conversion to, and substantial improvement of any residential structure (as defined in BCC 83.020) shall have the lowest floor, including basement, elevated a minimum of 18 inches above the Base Flood Elevation (BFE).

View official code

Full Breakdown

035. 020 to include dwellings, accessory dwelling units, manufactured dwellings, and accessory living areas, must have the lowest floor, including any basement, elevated a minimum of 18 inches above the BFE. That freeboard exceeds the bare federal NFIP minimum of at-BFE construction. 610, with a floodproofing alternative certified by a registered engineer or architect in place of elevation. 500(3): they must be sited outside the special flood hazard area whenever a feasible alternative exists, and if built within it, the lowest floor must clear the BFE by 3 feet or reach the 500-year flood elevation, whichever is higher, with access routes elevated to the same standard. 260, reviewed and maintained by the county's Floodplain Administrator, a role assigned to the Planning Official.

Violations & Fines

Building below the required freeboard, or skipping the Pre-Construction Elevation Certificate BCC 83.260 requires before a building permit issues, is treated as noncompliance with the Floodplain Management Overlay ordinance and reviewed by the Floodplain Administrator alongside the County Engineer before any floodplain development permit is issued. A structure built without the documented elevation is presumed in violation under BCC 83.020(57) until the required certification is produced.

Frequently Asked Questions

How far above the base flood elevation must a new home be built in unincorporated Benton County?
BCC 83.620(1) requires the lowest floor, including any basement, of a new or substantially improved residential structure to sit at least 18 inches above the Base Flood Elevation shown on the county's Flood Insurance Rate Maps, a standard higher than the federal minimum of building at BFE.
What counts as the Base Flood Elevation?
BCC 51.020(5) defines it as the height of the flood waters during a base flood, the flood with a 1% annual chance of occurring, expressed in feet above mean sea level at points along the affected watercourse, tied to the county's adopted Flood Insurance Rate Maps.
Do schools and fire stations get a stricter elevation standard?
Yes. BCC 83.500(3) requires critical facilities, including schools, hospitals, and police and fire stations, to be sited outside the special flood hazard area where feasible, and if built inside it, their lowest floor must clear the BFE by 3 feet or reach the 500-year flood elevation, whichever is higher.
What documentation proves a structure meets the freeboard requirement?
BCC 83.260 requires Pre-, Mid-, and Post-Construction Elevation Certificates, prepared and sealed by an Oregon-registered land surveyor or civil engineer, documenting the BFE, natural and finished grade, and the lowest habitable floor elevation, submitted to and maintained by the county's Floodplain Administrator.

Sources & Official References

Other rules in Benton County

Animal Ordinances: Dog Leash LawsSome RestrictionsStormwater ManagementSignificant RestrictionsErosion ControlSome RestrictionsDefensible SpaceSome RestrictionsFlood ZonesSignificant RestrictionsNoise Ordinances: Barking DogsSome RestrictionsAnimal Ordinances: Bird ProtectionSignificant RestrictionsAnimal Ordinances: Veterinary Clinic ZoningSome RestrictionsAnimal Ordinances: Wildlife Rescue PermitsFew RestrictionsAnimal Ordinances: Exotic PetsHeavy Restrictions

All Benton County rules

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