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Link to Dept. of Forestry debris flow warning system
How the debris flow warning systems works
An introduction to Oregon´s debris flow warning system
(Excerpted from a November 4, 1998 article in the Tillamook Headlight Herald)
The state of Oregon is prepared to alert people of heightened hazards from rapidly moving, life-threatening landslides called debris flows through a warning system involving the departments of Forestry (ODF), Geology and Minerals Industries (DOFAMI), and Office of Emergency Management (OEM).
Debris flows are rapidly moving landslides, commonly destroying almost everything in their paths and sometimes traveling for well over a mile.
The warning system was developed through Governor John Kitzhaber´s Debris Avalanche Action Plan, which directed several state agencies to seek solutions for reducing risks to life and property from debris flows. During the winter of 1996, a series of debris flows tragically killed five people, closed major highways and destroyed property.
"When a warning us issued, all parties have the shared responsibility to take prudent action," said Keith Mills, Geotechnical Specialist, ODF, Salem.
"People living near or traveling through steep V-shaped canyons need to stay clear of stream channels, canyon bottoms and fanshaped areas of sediment and boulder accumulations where a steep canyon empties into a wider valley," said Dennis Olmstead, DOGAMI. Homes located below large boulders perched on steep slopes or near canyon outlets, steep hillsides, and logjams in streams are hazardous areas under a warning. "People living in these type of locations should have a safe place to go when a warning is issued," he said.
Mills said that motorists should avoid all but emergency travel in these locations during warning periods. In contrast, debris flow advisories should serve as a reminder to landowners and other road managers of the responsibility to check drainage systems and to conduct needed maintenance in case a warning situation does occur.
Throughout the rainy season, ODF meteorologists will forecast storms and track rainfall at several locations throughout western Oregon. The advisory and warning system will then be used during expected (or realized) periods of tense rainfall that may trigger debris flows.
Advisories, which alert general locations on the possibility of severe weather which could trigger debris flow, are issued when rainfall is expected to reach a specific threshold for either a 6 hour, 12 hour or 24 hour period. Warnings are issued when the threshold is actually met during big rain storms and signal people to take immediate action to vacate or avoid areas prone to debris flows.
"The exact threshold triggering a warning will also depend on other factors such as rapid snow melt and prior heavy rainfall," said Mills. "It is important to remember that the system is only designed to advise or warn about debris flows which threaten life or property -- those most likely to occur during periods of heavy rainfall or snow melt."
Once an advisory or warning is declared, ODF immediately notifies the National Weather Service, which transmits the advisory or warning through its emergency management information network. The National Oceanic and Atmospheric Administration (NOAA) Weather Radio and OEM´s communication systems are all parts of the network. Debris flow warning and advisories will also be posted on the Oregon Department of Forestry homepage -- http://www.odf.state.or.us.
"OEM provides the link to local community by activating the Emergency Alert System (EAS), which provides warning information to the State Police, local emergency management organizations, 911 centers, and other emergency services agencies," said Abby Kershaw, OEM.
"The public is likely to hear about the advisories and warnings on radio, local TV stations, NOAA radio, and the National Weather Service web page on the Internet (http://nimbo.wrh.noaa.gov/portland/svr_pdx.shtml)," said Olmstead.
Individuals wishing to learn more about how to protect themselves and their property from landslides in Oregon can request a free brochure, "Landslides in Oregon," by calling ODF Public affairs at (503) 945-7424 or James Roddey, DOGAMI, at (503) 731-4100, ext 242.
Landslides home page at OregonGeology.com
Special Paper 34 - Slope Failures in Oregon, GIS Inventory for three 1996/1997 storm events
Data entry form to report landslide events
Information on Senate Bill 12, enacted during the 1999 legislative session, establishing Oregon’s policy regarding "rapidly moving" landslides and public safety.
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