Just found this thread. Very interesting as far as I'm concerned.
One of the guys I work with owns 160+ acres, and lost over 200 hardwood trees over the last few years. He knows I like shooting and asked if I could come help to try to kill some of the beavers.
I'd destroyed 14 dams in a section of about 3/4 of a mile. Some were small, and some were over 6 feet tall. I was amazed at the amount of water that I was able to drain from some of the small "ponds" the beavers created.
A couple of the beaver lodges were too darn big to try to take apart by hand, and with the terrain, it was too steep to get his backhoe in to take the dams apart. I mixed about 10 pounds of tannerite, packed it into PCV pipe, and had a friend shoot it with a .308. I could see the lodge "jump" about 6" into the air. Smoke started rising from the lodge. I wish I had a video, since it was pretty cool to see. He hasn't had any more dams build in the area around that lodge since we used the tannerite.