All four beaver dams and even the lodge where the beavers lived were washed downstream, said Heidi Perryman, who founded the group Worth a Dam.
But Thursday night the father beaver was seen swimming against the current with two of his three kits, Perryman said.
The third kit and a 2-year-old offspring that also lived in the creek were not seen.
The 2-year-old returned to the dam last June shortly after the mother beaver died. He has been seen helping the father beaver care for the kits, which are now about 10 months old.
Perryman said that the 2-year-old hasn't been seen in a while and it is possible he has moved away on his own.
The beavers have had their dams washed away during heavy rainstorms before and re-built them, but they have never had their lodge washed away.
"All that was left was a hole," Perryman said.
She said it isn't clear whether the beavers will rebuild again or move somewhere else, but said at least they weren't washed away in the current.