MONTECITO, CALIFORNIA — More than a dozen are dead after a torrent of mud and debris swept through California's Santa Barbara County last week. <br /> <br />The Ventura County Star reports that this deadly and shockingly common occurrence is called a "debris flow," though it's also commonly called a mudslide. <br /> <br />Often at risk for debris flows are mountainous areas that have been ravaged by wildfire. Fire kills vegetation and nutrients in the soil, causing it to become hydrophobic or water-repellant. <br /> <br />During intense rainfall, water that would normally be absorbed into the ground instead saturates it and causes the earth to liquefy into a flowing river of mud. <br /> <br />Debris flows grow in size as they pick up boulders, trees, and other debris, and are powerful enough to uproot or destroy entire neighborhoods. <br /> <br />Many of the deaths in Montecito reportedly occurred while most residents were asleep, after heavy rain fell in a short period of time around 3:30 a.m.
