Mudslide Safety for the Rainy Season

Oct 12, 2009

The U.S. Geological Survey issued a warning this week that severe mudslides are likely this winter in Southern California foothill communities that have recently been devastated by brush fires.  The Los Angeles Times reported that scientists have identified Pacoima Canyon, Big Tujunga Canyon, the Arroyo Seco, the West Fork of the San Gabriel River and Devils Canyon as being at high risk with an 80% chance of flows.


In some conditions, mudflows could contain up to 100,000 cubic yards of dirt and debris.  That’s enough material to cover a football field to a depth of 60 feet.

The threat of mudslides is made even greater by the potential for earthquakes in the area.  That possibility has been made apparent recently by mudslides triggered by earthquakes in Indonesia, which leveled an entire valley full of small villages.


The Red Cross has provided some helpful tips for driving in areas with the potential for mudslides:

  • Stay alert and awake. Many debris-flow fatalities occur when people are sleeping.
  • Listen to a NOAA Weather Radio or portable, battery-powered radio or television for warnings of intense rainfall.
  • Be aware that intense, short bursts of rain may be particularly dangerous, especially after longer periods of heavy rainfall and damp weather.
  • If you are in areas susceptible to mudslides and debris flows, consider leaving if it is safe to do so.
  • Remember that driving during an intense storm can be hazardous. If you remain, move to a second story if possible. Staying out of the path of a mudslide or debris flow saves lives.
  • Listen for any unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle of flowing or falling mud or debris may precede larger landslides. Moving debris can flow quickly and sometimes without warning.
  • If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and for a change from clear to muddy water. Such changes may indicate mudslide activity upstream, so be prepared to move quickly. Don’t delay! Save yourself, not your belongings.
  • Be especially alert when driving. Embankments along roadsides are particularly susceptible to mudslides. Watch the road for collapsed pavement, mud, fallen rocks, and other indications of possible debris flows.

If any drivers in your fleet are traveling in vulnerable areas, make sure they take this advice to heart and be safe!


Photo courtesy of crawfish head under the Creative Commons License.