The Sassafras flows into the Chesapeake across the bay from Harford County.
Also on Monday, the body of a woman who had been carried away by swift water on Friday evening in Harford County was recovered, Maryland State Police said.
She was identified as Melissa Anne Lehew, 34, of Darlington, Md.
Lehew fell and was swept off the Broad Run Bridge and into Broad Run, police said.
She had been trying to help someone inside a disabled car on the bridge in the Churchville area, police said.
Rushing water overtook that vehicle up to its roof, and it was also swept away, police said. When the vehicle was located, a man, Daniel Samis, 67, of Abingdon, was found dead inside, police said.
The flooding was caused by torrential rain in the area that day.