Oregon
» Introduction to Landslide Activities in Oregon
Photo of the toe area of the Newell Creek Apartment landslide, Oregon City, 2005 (photo from Scott Burns, 2005). One half of the apartment complex, including six structures like the one in the photo, were destroyed.
One of the most common and devastating geologic hazards in Oregon is landslides. Average annual repair costs for landslides in Oregon exceed $10 million, and severe winter storm losses can exceed $100 million (Wang and others, 2002). In the past ten years, Oregon has witnessed significant individual landslide events, like the Newell Creek Apartment complex in Oregon City, the landslide in downtown Astoria, debris flows on Mount Hood, and the debris flow at Woodson; these events are likely increasing the estimated average and severe winter storm losses. As population growth continues and as development into landslide susceptible terrain occurs, greater losses are likely to result. To reduce losses from landslides, planning and action are necessary at all community levels from state government to individual families. One successful way to reduce losses from landslides is through pre-disaster mitigation, which can be performed at many scales from statewide to local. Before pre-disaster mitigation can occur, the landslide hazard must be located. Once the hazard is located, the population and infrastructure vulnerable to the hazards can be identified and the risk mitigated.
» Websites
- Oregon Geology - Landslides Home Page
- SLIDO & SP-34 Interactive Map
- Pilot Lidar and Hazards Interactive Map
- Oregon Lidar Consortium (OLC)
- Oregon Department of Geology and Mineral Industries
DOGAMI’s Interpretive Map Series (IMS) includes many publications that identify landslides and landslide hazards, for example IMS-6, Water-induced landslide hazards, western portion of the Salem Hills, Marion County, Oregon. This publication series also includes studies with damage and loss estimates, for example IMS-24, Geologic hazards, earthquake and landslide hazard maps, and future earthquake damage estimates for six counties in the mid/southern Willamette valley including Yamhill, Marion, Polk, Benton, Linn, and Lane counties, and the City of Albany, Oregon.
Photo of the debris flow at Newton Creek, Mount Hood, 2006. This debris flow turned and flowed down Highway 35, destroying several miles of highway (photo from Bill Burns, 2006).
Photo of the upper scarp area of the Astoria First Street and Commercial Street landslides, Astoria, 2007 (photo from Bill Burns, 2007).
Photo of the Woodson debris flow fan deposit, Woodson, 2007. A large fill embankment in the creek above Woodson was plugged as the result of heavy rainfall. The plug caused the embankment to become a dam, which catastrophically failed days later to this large debris flow.
» Inventory Status for Oregon
The Oregon Department of Geology and Mineral Industries (DOGAMI), along with other Oregon state agencies, local governments, and federal agencies, has been studying and preparing maps with landslides and landslide hazards in Oregon since the 1950s. Most of this work has been published on paper maps and recently has been digitized and put into a database as the Statewide Landslide Information Database for Oregon (SLIDO), discussed below. Along with SLIDO, DOGAMI is engaged in several other efforts to inventory landslides in Oregon.
Another publication from DOGAMI that catalogs landslides is Special Paper 34, Slope failures in Oregon, GIS inventory for three storm events in 1996-97 (Hofmeister, 2000). The objective of this project was to collect and consolidate data on Oregon landslides associated with severe storm events in February 1996, November 1996, and December 1996/January 1997. The February storm event led to a Federal disaster declaration for 27 counties, the November event for 3 counties, and the December/January storms for 14 counties. The inventory database includes over 9,500 slide location entries. The database entries contain several items describing the geographic location of each landslide and up to 15 additional items relating to failure mechanism, size, geometry, associated damage, etc., depending upon the information obtained from the contributing sources. The digital outputs are intended to provide a starting point for future landslide-related studies. This publication is also available on the DOGAMI web site.
Currently DOGAMI is producing lidar-based landslide inventories for small portions of Oregon. The first of these maps was released in 2006, LIDAR-Based Landslide Geomorphology Map of Oregon City (Open File Report O-06-27). A pilot project area was selected to compare remote sensing data/images for effectiveness (Burns, 2007). Two key findings from this pilot study were: 1) the use of the light detection and ranging (lidar) data resulted in the identification of between 3 to 200 times the number of landslides found with the other data sets, and 2) the accuracy of the spatial extent of the landslides identified was greatly improved with the lidar data.
Map of the Statewide Landslide Information Database for Oregon (SLIDO) – Release 1 (Burns, Madin, Ma, 2008)
Map of the over 9,500 landslides from Special Paper 34 (Hofmeister, 2000)
Map of landslides identified using lidar in the Oregon City area (Madin and Burns, 2006)
