The Igua dam, on the Verruga river near the city of Vitoria da Conquista in southern Bahia, collapsed on Saturday night, forcing authorities to evacuate residents, mainly in the town of Itambe.
A second dam gave way to rising water levels in Jussiape, 100 kilometers to the north, on Sunday morning, bringing more alerts for residents to move to safer ground.
Rescuers rowed dinghies along flooded streets to reach trapped families or take them supplies. One man paddled on an inflatable mattress to reach a home.
Bahia Governor Rui Castro said at least 400,000 people have been impacted by the heavy rains and thousands evacuated from some 67 towns facing emergency situations due to floods caused by heavy rainfall for almost two months.