The waters had begun to subside on Wednesday afternoon but still rushed beneath a damaged bridge along the road linking Myanmar's major cities of Yangon, Mandalay and the capital Naypyitaw surrounded by acres of flooded fields.
The bridge stayed closed to heavy traffic as the carriageway for vehicles travelling north to south had buckled.
"When the water flooded the bridge we closed it, and by the time we arrived here around 8 a.m., two columns had sunk around two feet," said Deputy Minister of Construction Kyaw Linn, who joined in repair work by surveyors and workers.
Myanmar's heavy annual monsoon rains have caused widespread flooding that displaced more than 100,000 people and killed at least 11 in July.
Some dams were reported to be overflowing this month, but an irrigation and water management official told the privately-run Myanmar Times newspaper there was no risk of a collapse.
The dam built across the Swar creek in 2004 can hold 216,350 acre-feet of water to irrigate more than 20,000 acres (8,100 hectares) of farmland, says a Ministry of Agriculture and Irrigation document posted online.
Swar residents had expressed concerns that the dam was overflowing, said Ko Lwin, the journalist.
On Monday, the state-run Myanmar Alin newspaper said an administrator and an irrigation official had inspected the dam.
"There is nothing to be concerned about," it reported the administrator, Tun Nay Aung, as saying, as the dam had not exceeded its capacity.
Reuters was unable to trace contact details for Tun Nay Aung on Wednesday. Government spokesman Zaw Htay did not answer telephone calls from Reuters to seek comment regarding the prior concerns over the dam.
The Myanmar government is assessing some dam projects to help eliminate chronic power shortages, but their potential environmental impact makes the projects controversial.
Large areas were still cut off by the floods, said Aye Aye, 47, one of the relief providers in the Swar area.
"I don't know about all the people," she added. "But there were quite a lot of dogs. Motorcycles were also underwater. (We saw) dead buffaloes, dead cows."
