LOS ANGELES -- Santa Barbara County crews worked through the holidays to defend coastal communities from the second half of Southern California's familiar cycle of fire and flood.
They cleaned out the 11 debris basins that dot the Santa Barbara front country, making room for the dirt and ash and rocks that winter rains would inevitably send tumbling down mountain slopes laid bare by the massive Thomas fire.
But when the first major storm of the season slammed into the coast Monday, the thundering deluge of mud, car-sized boulders and trees that fell upon Montecito was beyond anything they expected.
Triggered by a band of intense rain -- which at one point early Tuesday dumped half an inch in five minutes -- the runoff gathered force in gullies and creek beds, collecting more and more deadly cargo as it blasted past the debris basins into wealthy hillside neighborhoods.
The Thomas fire was halted on the steep slopes just above Montecito, sparing the enclave. But the same dramatic landscape that made the Thomas fire so hard to fight propelled rivers of mud and rock on a devastating rampage, toppling houses, tossing cars around like pieces of Legos and carrying 3-foot-wide boulders all the way to the beach.
"It's almost unimaginable what I saw today," Tom Fayram, deputy public works director for Santa Barbara County, said Wednesday after a helicopter flight over the region.
Multiple debris flows dotted 13 miles of the front range. The basins his crews frantically emptied last month were "all chock full of rocks and debris," including the largest, which has a capacity of more than 20,000 dump trucks.
Some basins were constructed after the 1964 Coyote fire and the 1971 Romero fire burned large watersheds, setting the stage for floods and debris flows.
"We've seen pictures of debris flows from the Coyote fire in 1964 and large rocks were moved down. But nowhere near the scope of what happened here," Fayram said.
Heavy rain on steep slopes can trigger a flow without a fire, but big burns are a typical ingredient of Southern California debris flows.