CEDAR RAPIDS, Iowa—The Cedar River poured over its banks here Thursday, forcing the evacuation of more than 3,000 homes, causing a railroad bridge to collapse and leaving cars underwater on downtown streets. Officials estimated that 100 blocks were underwater in Cedar Rapids, where several days of preparation could not hold back the rain-swollen river. Rescuers had to use boats to reach many stranded residents, and people could be seen dragging suitcases up closed highway exit ramps to escape the water.

Days of heavy rain across the state have sent nine rivers across Iowa at or above historic flood levels. Residents were already steeling themselves for floods before storms late Wednesday and early Thursday brought up to 5 inches of rain across west central Iowa.