Weather Takes A Turn, Triggering Flood Warnings

PORTLAND, Ore. — Rain, wind, thunder and lighting moved in across the state late Thursday night and early Friday morning, triggering concerns of flooding especially in areas just burned by wildfires.

Flood warnings and advisories were in effect for Clackamas, Linn, Marion, Multnomah, Polk and Yamhill counties, but most have since expired.  The Cascades and Foothills are under flash flood watches.

The potential for landslides, debris flows and rock falls are also causing concern.  Bill Burns, Engineering Geologist for Oregon, says certain areas are prone to slides and now we’ve had wildfires in some of those areas, making the threat of slides even worse.  Like a perfect landslide storm.  He’s very concerned.  He says these types of slides can move tens of miles an hour and sometimes faster than you can outrun.  They gain momentum as they pick up debris.

Burns says the best thing to do before a storm hits is study your area.  Are you at the mouth of a channel or a drainage where slides flow to?  Or at the base of steep slope when rocks fall from?  If you are, and we get that heavy rain, he says you may want to consider evacuating as anyone below steep slopes in canyons and near the mouths of canyons may be at serious risk.

If your home, work, or route is in a watch area:

  • Stay alert. Track the flood watch by radio, TV, weather radio or online. If told to evacuate, do so immediately.
  • Listen. Unusual sounds 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.
  • Watch the water. If water in a stream or creek 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.
  • Travel with extreme caution. Assume roads are not safe. Be alert when driving, especially at night. Embankments along roadsides may fail, sending rock and debris onto the road.

More information is available on the Department of Geology and Mineral Industries website.

Clackamas County also provided the following tips:

Listen and watch for rushing water, mud, unusual sounds

  • Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
  • A faint rumbling sound that increases in volume is noticeable as the landslide nears.
  • Fences, retaining walls, utility poles, k-rails, boulders or trees move.

During a landslide or debris flow

  • Heed all warnings and evacuation notices.
  • Never cross a road with water or mud flowing.
  • Never cross a bridge if you see a flow approaching.
  • It can grow faster and larger too quickly for you to escape.
  • If you do get stuck in the path of a landslide move uphill as quickly as possible.
  • Avoid river valleys and low-lying areas during times of danger.
  • If you are near a stream or channel, be alert for any sudden increase or decrease in water flow or water that changes from clear to muddy. These can be signs that a landslide or debris flow is coming.

After a landslide or debris flow

  • Stay away from the slide area. There may be danger of additional slides.
  • Listen to local radio or television stations for the latest emergency information.
  • Watch for flooding. Floods sometimes follow landslides and debris flows because they may both be started by the same conditions.
  • Check for injured and trapped persons near the slide, without entering the direct slide area. Direct rescuers to their locations.
  • Allow trained professionals to check the building foundation, chimney, and surrounding land for damage.

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