Debris flow advisories and warnings

Link to Dept. of Forestry debris flow warnings

Emergency Warning System Procedures for Debris Flows in Western Oregon
updated 12-03-07 (38 KB PDF)

Landslide Hazards in Oregon Fact Sheet (1266 KB PDF)

OREGON’S DEBRIS FLOW WARNING SYSTEM AND HOW IT WORKS
Excerpted from the 11/4/99 document prepared by the Oregon Department of Forestry and modified 10/06/05 by DOGAMI

Oregon has implemented a debris flow warning system to advise people when certain areas become unsafe because of the threat of rapidly-moving landslides. The system is intended for people who live or travel below certain steep hillsides.

BACKGROUND
Debris flows are rapidly-moving landslides that can destroy everything in their paths. They can easily travel a mile or more, depending on the terrain. They typically contain boulders and logs transported in a fast-moving soil and water slurry down steep hillsides and through narrow canyons. A debris flow moves faster than a person can run.
The warning system was developed through Governor Kitzhaber’s Debris Avalanche Action Plan. The Plan directed several state agencies to seek solutions for reducing risks to life and property from debris flows. This action followed the 1996 series of winter-time debris flows that killed five people, closed major highways, and destroyed property.
Agencies involved in the warning system include the Department of Forestry (ODF), the Department of Geology and Mineral Industries (DOGAMI), Oregon Emergency Management (OEM) , and the Department of Transportation (ODOT).

Throughout the rainy season, ODF meteorologists will forecast storms and monitor rainfall at several locations throughout western Oregon. The warning system will be activated during expected and actual periods of intense rainfall that may trigger debris flows.

DEBRIS FLOW WARNINGS
Debris flow warnings are issued when a rainfall threshold is reached or nearly reached, particularly if night’s obscuring darkness is near. The analysis triggering a warning will also take into consideration other factors such as rapid snow melt and prior rainfall. A warning means people should avoid unsafe dwelling sites and roadways. The safest movement would be along routes that avoid steep slopes to the extent possible.

AFFECTED AREAS
Advisories and warnings use landmarks, county lines, or state highways to describe the boundaries of affected areas that are not safe.

WHAT TO DO
Homes and roads at the base of steep slopes in or near canyon outlets are in the most hazardous locations. People living or traveling roads in such areas should stay clear of steep stream channels and steep canyon walls. People living in these types of locations should have a safe place to go when a warning is issued. Motorists should avoid all but emergency travel on roads below hazardous areas during warning periods.

“People want to know what they should do when they hear about a landslide warning,” says James Roddey, Earth Science Information Officer for the Oregon Department of Geology and Mineral Industries (DOGAMI). “Some areas are more hazardous than others when the danger of landslides is high. People know that if there’s a flood warning, they should stay away from the river. We also want them to start thinking about staying away from steep slopes during intense rainstorms. Knowing ahead of time where the danger areas around your home for potential landslides might be is the first step in being prepared,” explains Roddey.

He recommends several steps:

• Stay alert. Listen to the radio, TV, or a weather radio for warnings, and if told to evacuate, do so immediately.

• Listen for unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle of falling mud or debris may precede larger landslides.
• If you think there is danger of a landslide, leave immediately.

• If water in a river or stream suddenly turns muddy or the amount of water flowing suddenly decreases or increases, this is a warning that the flow has been affected upstream You should immediately leave the area because a debris flow may soon be coming downstream.

• Assume highways are not safe. Be alert when driving, especially at night. Don’t overdrive your headlights. Embankments along roadsides may fail, sending rock and debris onto the road.

• Landowners and road managers should check road drainage systems and conduct needed maintenance in case the predicted heavy precipitation does occur.

Road maintenance personnel should also take heed of this increased hazard level and move out of the hazardous area along routes that avoid steep slopes if possible.

Cleaning up after landslides can also be hazardous. “When it’s this wet outside, people need to be careful when they’re cleaning up the mess. A small mudslide can actually be part of a larger landslide,” explains Roddey. “Cleanup should not be done until after the storm.”

WHERE TO FIND OUT ABOUT WARNINGS
Once a warning is declared, ODF creates and transmits the official statement to the National Weather Service, which relays the advisory or warning through its emergency management alert and information network. The National Oceanic and Atmospheric Administration (NOAA) Weather Radio and OEM’s communication systems are part of the network. Debris flow warnings are also posted on ODF’s Internet web site, http://egov.oregon.gov/ODF/FIRE/debris.shtml

Anyone interested can learn about the advisories and warnings on radio, local TV stations, NOAA weather radio, ODF’s web site or the National Weather Service (which links directly to ODF’s web site for the official statement).

DOGAMI will provide additional technical information in response to media or public questions. For more information contact James Roddey at (971) 673-1555.

Warnings will be cancelled through these same media if the expected heavy rainfall fails to materialize or after rainfall intensity drops for a sufficient period of time.

To learn more about protecting people and property, anyone interested can request a free brochure entitled Landslides in Oregon by calling The Nature of the Northwest Information Center at (503) 872-2750. The brochure was developed through the cooperative efforts of DOGAMI, ODF, OEM, Oregon Department of Transportation, Department of Administrative Services, Division of State Lands, and the Building Codes Division.

KEY CONTACTS FOR WARNING SYSTEM STATUS:
Oregon Department of Forestry’s web site: http://egov.oregon.gov/ODF/index.shtml
National Weather Service web site: http://www.wrh.noaa.gov/pqr/

NOAA Weather Radio Frequencies: 162.400, 162.425, 162.450, 162.475, 162.500,162.550.
Office of Emergency Management Duty Officer: (503) 378-6377
Department of Geology & Mineral Industries: (971) 673-1555
Local radio and TV stations (not out-of-state cable TV)

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