United Nations officials say engineers were forced to let water pass through a dam on the Artibonite River on Sunday.
People living along the waterway were alerted to evacuate their families and livestock. Authorities are expected to fly over the area to look for flooding Monday.
Cholera is new to Haiti. The diarrhea and fever-causing illness has killed some 500 people and hospitalized thousands since appearing last month. Its origin has not yet been confirmed.