Cleanup was beginning across Southern California on Saturday after a storm that forecasters billed as the most powerful in years caused flooding on multiple freeways, triggered dramatic mudslides and downed hundreds of trees and power lines. The storm was moving out Saturday morning after dumping record rain in some areas and leaving havoc in its wake. Thousands of Los Angeles County residents remained without power early Saturday, while road crews scrambled to repair sinkholes throughout the area, including one in Studio City that swallowed two vehicles Friday night. No one was injured in the incident.