Geologic Hazards

Northwest Clackamas County is more susceptible to landslides than many other locations in the Portland-Metro area. Slides are commonly triggered by:

  • Heavy rain
  • Rapid snow melt
  • Earthquakes
  • Grading/removing material from bottom of slope or adding loads to the top of the slope
  • Concentrating water onto a slope (for example, from landscape irrigation, roof downspouts, or broken water/sewer lines)

Slides generally occur on moderate to steep slopes, especially in weak soil.

The City of Oregon City has a digital mapping program; once there, you can access the City's GIS mapping program, OCWebMaps, which includes Oregon City and outlying areas. In the Map Layers list, there is a section labeled "Hazards and Flood Info", which contains information for steep slopes and landslide areas (please note that to view a layer, you must check the box beside it, and check the box beside the "Hazards and Flood Info" section). Essentially, you can navigate to your address and see if your residence is in any of the known hazardous areas.

New Geologic Hazards Municipal Code Update

Revisions to the Geologic Hazard Code were adopted July 21, 2021; to view the updates, review the Supporting Documents section on this page. These code revisions were presented to the City Commission, Natural Resource Committee, and a Development Stakeholder Committee. The revisions were processed by the Planning Department with a Legislative Application processed through the Planning Commission and City Commission. A Community forum to discuss the code amendments and geologic hazards in general occurred on September 23, 2020. Learn more about the community forum on the 2020 Geologic Hazard Code Updates page.

Home Is Located Within a Hazards Zone - My Options

Oregon City regulates and limits tree removal, grading and development in areas with steep slopes or historic landslides. More information is available by going to the Planning Division page or by calling them at 503-722-3789. They can answer questions related to development in areas within the Geologic Hazard Overlay Zone; more information can be found in Chapter 17.44 of the Oregon City Municipal Code (OCMC).

Activities in the hazard zones identified in OCMC 17.44.025 require that a Geologic Hazards Checklist be completed. More detail can be found in the Supporting Documents section of this page.

Any owner or developer proposing development within the Geologic Hazard Area must complete the Declaration of Covenant of Release and Indemnity for Geologic Hazards found in the Supporting Documents section of this page.

Additional Resources & Information

Another fantastic source to learn more about landslides and how to prepare for them is at the Oregon Department of Geology and Oregon Department of Land Conservation and Development. This site also has digital mapping programs showing historical landslide information for all of Oregon. A handy Homeowner's Guide to Landslides booklet has also been published by the Department of Geology at Portland State University in cooperation with the Federal Emergency Management Agency (FEMA) and can be found in the Supporting Documents section of this page.

As of October 2019, The Department of Land Conservation and Development (DLCD) along with Oregon Department of Geology (DOGAMI) has published a new land use guide about landslides called Preparing for Landslide Hazards: A Land Use Guide for Oregon Communities (PDF) which can also be found at both agencies respective websites.

An analysis by DOGAMI can be viewed on YouTube: Landslide Susceptibility Mapping and Risk Analysis for Clackamas County, Oregon.

Supporting Documents