As significant wet weather rolls across the state later this week, the California Governor’s Office of Emergency Services (Cal OES) encourages residents to be aware of mudslides and debris flows, especially in burn scar areas.
Prepare for Mudslides and Debris Flows
- Be on alert for local law enforcement messages and follow evacuation notifications immediately.
- Sign up for local emergency alerts.
- Monitor incoming storms, especially if you live in burned areas or downstream/downslope of a burned area.
- Have an evacuation plan in place for you and your pets.
During Mudslides and Debris Flows
- Remember – local authorities may indicate it is safer for you and your family to shelter in place if flash flooding is not impacting your neighborhood.
- Do not walk through moving water – just six inches of water can sweep an adult off his/her feet.
- Do not attempt to drive through a flood, debris flow or into flooded areas. It takes only a foot of water to float or sweep away most vehicles. Turn around, don’t drown.
- If you live on a hill, do not sleep in bedrooms that are on the ground floor which face the hazardous slopes.
Burn Scars
In the days, weeks, months and even years after a wildfire, the burned land often loses its vegetation, making the soil unable to absorb rainwater. Rainfall that would normally be absorbed by the soil will instead quickly run off.
Significantly less rain is required to produce a flash flood, and the potential for mudslides and debris flows increases with the loss of plants and vegetation that holds the soil in place. Because of this, locations that are downhill and downstream from burned areas are highly vulnerable to rain that can cause mudslides and debris flows, especially in and around steep terrain.
Debris Flow
Californians who live on or below hillsides, especially in areas impacted by recent wildfires, should be aware that precipitation increases the probability of potentially dangerous debris flows.
A debris flow is a fast-moving mass of material — slurries of water, rock, soil, vegetation, boulders and trees – that moves downhill by sliding, flowing and/or falling.
Debris flows range from a few square yards to hundreds of acres in size, and from a few inches to many dozen feet deep. Even smaller ones can be dangerous. Imagine trying to walk through a 3-inch-deep mass of wet concrete moving at 30 mph.