Grading & Drainage: Gresham vs Portland
How do grading & drainage rules compare between Gresham, OR and Portland, OR?
Gresham has fewer restrictions than Portland.
Gresham, OR
Multnomah County
Portland requires grading permits under PCC Title 24 for excavation or fill exceeding 50 cubic yards or slopes over 20%. Portland's Landslide Hazard areas (West Hills) require geotechnical reports. Drainage cannot be redirected onto neighboring properties (ORS 105.170). Retaining walls over 4 feet require engineered plans. Multnomah County Land Use requires grading permits in unincorporated areas on SEC overlay or steep slopes.
View full Gresham rules →Portland, OR
Multnomah County
Portland regulates grading and drainage through Title 10 (Erosion and Sediment Control), Title 17 (Public Improvements), and Title 24 (Building Regulations). Grading permits are required from the Bureau of Development Services for excavation or fill exceeding certain thresholds. All grading must maintain natural drainage patterns and prevent adverse impacts to neighboring properties.
View full Portland rules →Key Facts Comparison
| Fact | Gresham | Portland |
|---|---|---|
| Portland Threshold | 50 cu yd / 20% slope | - |
| West Hills | Landslide overlay geo report | - |
| Retaining Walls | Permit if >4 ft | - |
| State Law | ORS 105.170 drainage | - |
| DSL Permit | Wetlands/salmon habitat | - |
| Permit Required | - | Cuts/fills over 5 ft depth or 50 cu yd |
| Governing Codes | - | Title 10, Title 17, Title 24 |
| Drainage Standard | - | No adverse impact to neighbors |
| Environmental Zones | - | Additional restrictions apply |
| Issuing Agency | - | Bureau of Development Services |
Highlighted rows indicate differences between cities.
Gresham FAQ
Do I need a grading permit to regrade my yard?
Yes in Portland if you move over 50 cubic yards or work on slopes over 20%. Small gardening/landscaping is exempt. West Hills properties often require geotech reports for any earthwork.
Can I build a 3-foot retaining wall without a permit?
Under 4 feet typically exempt from structural permit under ORSC, but Portland still requires a zoning review if it affects setbacks or drainage. Always check with BDS.
Portland FAQ
When do I need a grading permit in Portland?
Grading permits are generally required for excavation or fill exceeding 5 feet in depth or 50 cubic yards in volume. Even smaller projects must comply with erosion control requirements under Title 10 and drainage standards under Title 17.
Can I change drainage patterns on my property?
Grading and drainage changes must not adversely impact neighboring properties. If your project creates or replaces 500 or more square feet of impervious surface, stormwater management requirements under the SWMM also apply.
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