The National Weather Service has issued a flash flood watch for Friday afternoon through evening for areas of northeast Oregon, including Wallowa County, the Grand Ronde Valley, John Day Basin, northern and southern Blue Mountains, and the Ochoco-John Day Highlands. The northwest Blue Mountains of Washington are also included in the watch.
Debris flows are possible in areas with steep terrain, particularly within wildfire burn scars, during this weather event. 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.
“Recent wildfires have made land less stable,” says Bill Burns, engineering geologist with the Oregon Department of Geology and Mineral Industries (DOGAMI). “Heavy rain is a common landslide trigger, so it’s important to be aware of the potential hazard during this storm.”
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: bit.ly/landslidehazards.