Flood Zones: Gresham vs Portland
How do flood zones rules compare between Gresham, OR and Portland, OR?
Gresham and Portland have similar restriction levels.
Gresham, OR
Multnomah County
Gresham participates in the NFIP and regulates development in FEMA-designated flood zones. Properties in the floodplain have strict building requirements including elevation certificates and flood-resistant construction.
View full Gresham rules →Portland, OR
Multnomah County
Portland regulates development in FEMA-designated flood hazard areas under City Code Chapter 24.50 (Flood Hazard Areas). The city amended these regulations in 2024 to comply with FEMA Pre-Implementation Compliance Measures (PICM). Major flood zones include Johnson Creek, Crystal Springs Creek, Columbia Slough, Tryon Creek, and the Willamette River corridor.
View full Portland rules →Key Facts Comparison
| Fact | Gresham | Portland |
|---|---|---|
| NFIP | Participating community | - |
| Elevation | Must build above BFE | - |
| Certificate | Elevation certificate required | - |
| Key Area | Johnson Creek floodplain | - |
| Governing Code | - | Portland City Code Chapter 24.50 |
| Elevation Requirement | - | 1 foot above Base Flood Elevation |
| Major Flood Areas | - | Johnson Creek, Columbia Slough, Willamette River |
| 2024 Amendment | - | FEMA PICM compliance measures |
| Tree Replacement | - | 3:1 to 6:1 ratio in floodplain |
Highlighted rows indicate differences between cities.
Gresham FAQ
Is my property in a flood zone in Gresham?
Check FEMA flood maps or contact Gresham Development Services. Johnson Creek and tributaries are primary flood hazard areas.
Can I build in a flood zone in Gresham?
Yes, with strict requirements: elevation above the base flood elevation, flood-resistant construction, and an elevation certificate.
Portland FAQ
What areas of Portland are in FEMA flood zones?
Major flood hazard areas include Johnson Creek, Crystal Springs Creek, Columbia Slough, Tryon Creek, and portions of the Willamette River corridor. FEMA flood maps identify specific properties in the 100-year and 500-year floodplains.
Can I build in a Portland flood zone?
Development is allowed but heavily regulated under Chapter 24.50. New structures must be elevated at least one foot above Base Flood Elevation. A Flood Hazard Area Development Permit is required for any construction, fill, or substantial improvement in the floodplain.
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