Portland, OR Environmental Rules: Flood Zones (2026)
FEMA flood zone rules in Portland, 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 trigger
- Any development in a flood hazard area
- Freeboard, Willamette/Johnson Creek
- Base flood elevation + 2 ft
- Freeboard, Columbia River zones
- Base flood elevation + 1 ft
- Administered by
- Portland Permitting & Development
- Floodway encroachment
- Prohibited absent no-rise study
Summary
Portland requires a development permit before any construction, fill, or grading in a mapped flood hazard area, with elevation and floodproofing standards set by zone.
A. Permits. All permit applications will be reviewed to determine whether proposed development and building sites comply with the provisions of this Chapter and will be reasonably safe from flooding. A development or building permit must be obtained before construction or development begins within any flood hazard area. The development or building permit is required for all structures, including manufactured homes, and for all other development, as defined in this Chapter, including fill. Such applications for permits must include the following information:
1. Boundary of flood hazard areas.
2. Boundaries of the high hazard area, top of bank, 50-foot setback from top of bank, Ordinary High Water Mark, and the PICM Riparian Buffer Zone, as applicable.
3. The base flood elevation and design flood elevation.
4. Elevation of lowest floor, including basement, for all structures and floodproofed elevations for nonresidential structures.
5. When required by the Floodplain Administrator, documentation necessary to verify substantial improvement or substantial damage.
6. Elevation of lowest point of bridge structures.
7. Existing and proposed topography of the site taken at a contour interval (normally 1 foot) sufficiently detailed to define the topography over the entire site and adjacent watercourses subject to flooding. Ninety percent of the contours must be plotted within 1 contour interval of the true location.
Full Breakdown
Chapter 24.50 covers all of the city's floodway and flood fringe areas along the Willamette and Columbia Rivers, Johnson Creek, Fanno Creek, Tryon Creek, and Crystal Springs Creek. A development or building permit is required before construction, fill, or grading begins in any flood hazard area, and new or substantially improved structures must have their lowest floor elevated to the flood protection elevation (base flood elevation plus 1 to 2 feet of freeboard depending on the watercourse). The Floodplain Administrator, housed in Portland Permitting & Development, reviews applications and can require a FEMA elevation certificate, floodproofing certification, and compensatory excavation to offset lost flood storage volume.
Violations & Fines
Building or filling in a flood hazard area without the required permit is a Title 24 violation: the City Administrator can issue a stop-work order under § 24.10.060, withhold occupancy approval, and pursue court action to force removal of unlawful work. Floodway encroachments are barred outright under § 24.50.060(D) unless engineering analysis shows no rise in the base flood elevation, and appeals go to the Administrative Appeal Board under Chapter 24.10.
Frequently Asked Questions
Do I need a permit to build in a Portland flood hazard area?
How much freeboard does Portland require above base flood elevation?
Sources & Official References
Other rules in Portland
Compare Portland to another location·View the Oregon environmental rules overview
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Flood Zones in Nearby Cities
How other cities in Multnomah County handle flood zones.