SAN FRANCISCO — Rescue workers scoured mud-swollen riverbeds in the wealthy Southern California enclave of Montecito on Wednesday, clutching to the hope that they might find some of the more than a dozen people missing after mudslides swept away about 100 houses.

At least 17 people were killed in mud flows so powerful that some one-story ranch homes in the area, which is northwest of Los Angeles, were covered up to their gutters. The devastation, sudden and violent, struck early Tuesday after a winter storm drenched and destabilized hillsides stripped bare last month by the largest wildfire in California history.

“Hundreds of people have been rescued and evacuated, many of them having to be hoisted out of the area by our aircraft,” Bill Brown, the Santa Barbara County sheriff, said Wednesday afternoon.