The National Weather Service has issued a flood watch for most of northwest Oregon and southwest Washington for tonight through Wednesday afternoon. The watch includes the greater Portland metro area, north and central Oregon coast, the central Willamette Valley, the central Columbia River Gorge, the north and central Coast Range, and the northern Oregon Cascades and Cascade foothills.
“Intense rainfall is a common landslide trigger,” says Bill Burns, engineering geologist at the Oregon Department of Geology and Mineral Industries (DOGAMI). “Landslides and debris flows are possible during this period of severe weather, so it’s important to be aware of the potential hazard.”
Debris flows are rapidly moving, extremely destructive landslides. They can easily travel a mile or more, depending on the terrain. They will transport boulders and logs in a fast-moving soil and water slurry.
People, structures and roads located below steep slopes in canyons and near the mouths of canyons may be at serious risk. Caution should be used when traveling. According to DOGAMI, the most dangerous places include:
– Canyon bottoms, stream channels, and areas of rock and soil accumulation at the outlets of canyons.
– Bases of steep hillsides.
– Road cuts or other areas where slopes of hills have been excavated or over-steepened.
– Places where slides or debris flows have occurred in the past.
Learn more about landslides and debris flows and how to prepare for them:
Statewide Landslide Information Database (SLIDO): www.oregongeology.org/slido
Landslide and debris flow resources: http://bit.ly/landslidehazards