Arch Cape Mill Creek Side
On November 15, the Oregon Department of Forestry’s Tillamook District received notice of sediment in Cedar Creek where it meets the Wilson River. The source was determined to be located near a slope above Arch Cape Mill Creek, within the Tillamook State Forest.
After review by the Department’s Engineering Geologist, it was determined to have been a deep-seated rapidly moving landslide likely triggered by the record 26 inches of rain this fall. As a result of the landslide, ODF is reviewing aerial data which indicates a history of ground movement in the area. This information will be helpful in future planning efforts.
Impact: The #93 Mongos Canyon motorcycle trail along Arch Cape Mill Creek is closed until further notice. Re-routing or re-opening the trail is pending future surveying and planning of the site. The slide was within the Tillamook State Forest where no structures are present.
The debris settled and was mostly contained on the slope within the 250 foot-wide forested stream buffer. Due to continued movement of the debris during rain events throughout the winter and the remote location and size of the slide, no action will be taken at this time to address further sediment delivery to Cedar Creek and the Wilson River.
· Landslides are a natural occurrence in the Coast Range, shaping the topography.
· ODF estimates, during large storm events on slopes with similar steepness, about 13 slides per square mile occur on forests over 100 years old in the Coast Range.
· Updates on the Arch Cape Mill Creek motorcycle trail and slide information will posted to the Tillamook State Forest blog http://tillamookstateforest.blogspot.com/
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For more information contact:
Kate Skinner, District Forester, Tillamook
503.845.2545 or kate.j.skinner@oregon.gov
