South Carolina’s virtually unprecedented rainfall finally stopped Monday, but worries continue as rainwater moves from upstate and midland rivers and streams into its already hard-hit Low Country. Authorities said early Tuesday that rescue crews in boats and helicopters across the state were plucking stranded residents from rooftops. The death toll stood at 11 after parts of the state received more than 2 feet of rain. Among the dead: a state transportation supervisor who was swept away in his truck near Columbia. Most schools remained closed Tuesday. President Obama declared several counties a disaster area and ordered federal aid to support recovery efforts.