Hmm, maybe our beavers are too busy dodging gators to be that industrious. Sounds like you have a large population if they're maintaining those large dams and plugging your inlet pipes.
Oh yes, surrounded by wetlands hosting a ton of beavers... 6 Down... many more to go I guess.
This quote from the article Dave mentiosn (Huge beaver dam in Alberta) is a little daunting:
"They're invading their old territories in a remarkable way in Canada," he said. "I found huge dams throughout Canada,
and beaver colonies with up to 100 of them in a square kilometer."