Landslides are relatively common, naturally occurring events in some parts of Oregon. Landslides include any detached mass of soil, rock, or debris that moves down a slope or stream channel. They are classified by the type and rate of movement of materials transported and occur when earth materials fall, slide, or flow down a slope.

Landslides pose significant threat to many communities in Oregon and create challenges to development in steep terrain, coastal regions, and other landslide-prone areas. Landslides threaten transportation corridors, fuel and energy conduits, and community facilities. While not all landslides result in property damage, many landslides impact roads and other infrastructure, and can pose a serious life-safety hazard. Landslide-prone areas are often easily identified; they often exist in highly desirable locations for development, such as beachfront or hillside property. 

Although landslides occur frequently in Oregon (see the Atlas of Oregon map titled “Landslides and Earthquakes”), most landslides occur in very sparsely populated areas within or near the Coast and Cascade Mountains. On occasion, major landslides occur on US Highway 101 or on I-84 that sever these major transportation routes causing temporary but significant economic damage to these regions of the state. Although less frequent, landslides and debris flows do occur that result in the death of people located in their paths.

Because of its importance to the state’s economy, landslides occurring in Multnomah County present the greatest danger from this type of disaster. Landslides in Tillamook County, particularly those that close US Highway 101 have a significant affect on commerce in the Oregon Coast Region. Landslides occurring in Lincoln County have closed US Highway 101. Based upon local hazard analysis the counties that have identified landslides as a major concern are: Hood River, Multnomah, Tillamook, Wallowa, and Wheeler. 

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