As an intense storm moved through Southern California, a debris flow sent mud down Mulholland Drive in Hollywood Hills -- leading to a full closure of the roadway Thursday evening, authorities said.

It’s different like that.” Debris flows carry mud and water, and their power, speed and thick consistency allow them to also transport heavy objects like a boulder the size of a Volkswagen Beetle.

One of the worst debris flows in modern California history occurred when a river of mud and rock flowed through Montecito in January 2018, killing 23 people and destroying at least 130 homes.

Debris flows made up of water, mud, boulders, brush and trees emerged from the canyons of the Santa Ynez Mountains, overtopped debris basins and traveled several miles, destroying parts of the ...

Generally, National Weather Service debris-flow warnings are triggered if a quarter-inch of rain falls in 15 minutes, or if one inch falls in an hour, Mickelson said.

Such a debris flow likely added damage to Mount Rainier National Park when a flood sparked by nearly 18 inches of rain in two days shut it down in November 2006. Experts are concerned that the ...