The move on Tuesday came amid a state of emergency in several flood-ravaged provinces.
At least 47 people have been killed in the past two weeks from flash floods triggered by the worst rains in Iran in at least a decade.
Ali Asghar Peyvandi, the head of Iran’s Red Crescent, said he feared many villages in Khuzestan “will be submerged” as flood waters moved south towards the oil-rich province.
“With the possibility of dams overflowing, we have made preparations to accommodate 100,000 people,” he told state television.
Khuzestan has an extensive range of dams but officials said water was flowing into them at a fast rate. In some cases water levels were only 70cm lower than the dam crests, they reported.
“Our dams are more than 95 percent full,” Gholamreza Shariati, governor of the province, told state TV.
Iranian media said on Tuesday that electricity and telecommunications had been cut in affected areas, roads had been washed away and people were waiting on rooftops to be rescued in some villages.
President Hassan Rouhani, accused by critics of mishandling the flooding crisis, has promised compensation to all those affected.