Land Divisions in Potential Landslide Hazard Areas
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Source: Land Divisions in Potential Landslide Hazard Areas ↗ Last modified: Sun, 19 Apr 2026 20:05:41 GMT
What is the purpose of these regulations?
The intent of the regulations for landslide hazard areas is to ensure that land divisions in areas of potential landslide hazard are designed based on detailed knowledge of the site conditions in order to reduce the risk of private and public losses as a result of landslides.
Where do these regulations apply?
These regulations apply to land division proposals where any portion of the site is within a potential landslide area, as identified on the City’s Potential Landslide Hazard Areas Map, available on PortlandMaps ↗.
What are the land division requirements if my property is in the potential landslide hazard area?
If any part of your site is a potential landslide hazard area, your application must include a Landslide Hazard Study and address the standards or approval criteria of Portland City Code Chapter 33.632. The proposal must locate the lots, buildings, services, and utilities on parts of the site that are suitable for development in a manner that reasonably limits the risk of a landslide affecting the site, adjacent sites, and sites directly across a street or alley from the site.
Site improvements may be required to limit risk. Alternative development options, such as reduced density and housing types may also be required.
Frequently Asked Questions
How will I know if my property is in a potential landslide hazard area?
You can determine whether your site is within the potential Landslide Hazard Area or within other hazard areas on PortlandMaps ↗ by searching for your site address and then scrolling through the information on the right side of the screen. Alternatively, call 503-823-7300 or schedule a 15-minute appointment with a City Planner ↗.
How was the potential landslide hazard area map created?
The map was created from the following sources:
- Oregon Department of Geology and Mineral Industries (DOGAMI) Interpretative Map Series IMS-22: GIS Overview Map of Potential Rapidly Moving Landslide Hazards in Western Oregon.
- IMS-57 Landslide Inventory Map of Central and Eastern Multnomah County.
- IMS-57 Deep Landslide Susceptibility Map of Central and Western Multnomah County, high and moderate susceptibility areas.
- IMS-57 Shallow Landslide Susceptibility Map of Central and Western Multnomah County, high susceptibility areas modified to include only areas with an average 30 percent slope or greater.
If my site has a potential landslide hazard area, how are the density calculations impacted for the site?
For single-dwelling zones:
- Minimum density: The area of the site within the potential landslide hazard area is subtracted from the total site area when calculating minimum density (see Portland City Code Chapter 33.610 ↗).
- Maximum density: You may still propose the maximum number of lots allowed by your site area, as long as your proposal and landslide hazard study demonstrate that your site can safely accommodate the dwellings and accompanying services.
For multi-dwelling zones, the minimum density may be reduced through the land division to facilitate suitable development.
If my property has no obvious landslide hazard, but it is still shown within the potential landslide hazard area, do I still need to meet these requirements?
Yes. A landslide hazard study is still required. However, the level of investigation and analysis is expected to be commensurate with the level of hazard, the complexity of site conditions, and the complexity of the proposed development.