Hillsboro, OR Environmental Rules: Flood Zones (2026)
FEMA flood zone rules in Hillsboro, OR, 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
- Floodplain Activity (FA) Permit
- Governing zone
- RFO Regulatory Floodplain Overlay
- Flood study date
- October 19, 2018
- Administered by
- City Floodplain Administrator
Summary
Hillsboro requires a Floodplain Activity Permit for nearly all development in the FEMA-mapped 1% annual chance floodplain, administered by the City's Floodplain Administrator under the Regulatory Floodplain Overlay zone.
The Regulatory Floodplain Overlay (RFO) zone applies to special flood hazard area (also known as the "1% annual chance floodplain," "100-year floodplain," "floodplain") identified by the Federal Insurance Administration in a scientific and engineering report titled "Flood Insurance Study for Washington County, Oregon and Incorporated Areas" dated October 19, 2018, with accompanying Flood Insurance Maps, which are hereby adopted by reference and declared to be a part of the Community Development Code. The Flood Insurance Study is on file and available at the Community Development Department at 150 E Main Street, Hillsboro, Oregon. The Flood Insurance Study and accompanying FIRMs are hereby adopted by reference and declared to be a part of this ordinance. The RFO may also apply to areas identified by the Floodplain Administrator or City Engineer under paragraph B, Boundary Interpretation, below. All proposed development, including placement of manufactured homes, in the RFO requires a Floodplain Activity Permit (see CDC Section 12.80.070 Floodplain Activity), except where an exemption is granted in Section 12.27.120.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 1 | Community Development Code: Supplement 1).
Full Breakdown
The Regulatory Floodplain Overlay (RFO) zone covers FEMA-mapped special flood hazard areas identified in the Flood Insurance Study for Washington County, dated October 19, 2018. Any new structure, addition, topographic alteration, fill, or placement of a manufactured home inside the RFO needs a Floodplain Activity (FA) Permit reviewed by the City Floodplain Administrator, unless it qualifies for a narrow exemption such as agricultural fencing or underground utilities with no ground disturbance. Hillsboro's floodplain rules operate inside FEMA's National Flood Insurance Program and Oregon's statewide land-use planning framework, not as a freestanding city ordinance.
Violations & Fines
Building or filling in the floodplain without an FA Permit is a code violation; the City can require removal, restoration, or retroactive permitting, and unpermitted work can jeopardize residents' flood insurance eligibility.
Frequently Asked Questions
Does every property in Hillsboro need a floodplain permit?
What counts as regulated 'development' in the floodplain?
Sources & Official References
Other rules in Hillsboro
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Flood Zones in Nearby Cities
How other cities in Washington County handle flood zones.