Debris Flow (Mud Slide) & Mudflow

What is a Debris Flow?

DEBRIS FLOW (commonly called a MUDSLIDE by the media) is a moving mass of loose mud, sand, soil, rock, water and air that travels down a slope under the influence of gravity. To be considered a debris flow, the moving material must be loose and capable of “flow”, and more than half of the solids in the mass must be larger than sand grains.

 

MUDFLOW is a mass of water and sand-sized particles that can flow very rapidly. Mudlflows are the sandy, more watery counterparts of debris flows.

 

The media often use the term MUDSLIDE for events that are actually DEBRIS FLOWS or MUDFLOWS.

 

Characteristics:

Debris and mud flows are a combination of fast moving water and a great volume of sediment and debris that surges down slope with tremendous force. The consistency is like that of pancake batter. They are similar to flash floods and can occur suddenly without time for adequate warning.

 

In urban settings such as Burbank, large debris flows usually only occurs when the hillsides are denuded following wilfires.  Wildfires burn the vegetation and damage the root systems that help hold the soil in place during storms.

 

Preparedness:

·         The first thing to prepare for all emergencies is to have a plan, what will you do? And have a disaster preparedness kit.

·         If you know your area is prone to or susceptible to potential mud or debris flows, have sandbags filled and placed to channel water, mud and debris away from your property before a storm begins.  (Where to get sandbags)

·         Watch the patterns of storm-water drainage on slopes near your home, and especially the places where runoff water converges, increasing flow over soil-covered slopes. Watch the hillsides around your home for any signs of land movement, such as small debris flows, or progressively tilting trees. Watching small changes could alert you to the potential of a greater threat.

What to Do During Intense Storms:

·         Stay alert. 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 landslides 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 at home, move to a second story if possible. Staying out of the path of a landslide 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 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 landslides. Watch the road for collapsed pavement, mud, fallen rocks, and other indications of possible debris flows.

What to Do if You Suspect Imminent Danger:

·         Call 9-1-1

·         Inform affected neighbors. Your neighbors may not be aware of potential hazards. Advising them of a potential threat may help save lives. Help neighbors who may need assistance to evacuate.

·         Evacuate. Getting out of the path of a debris flow is your best protection.